Low Manifold Vacuum
01-18-2005, 03:36 PM
#1
Guest
Posts: n/a
Low Manifold Vacuum
"problem" performance continues in a rebuilt 2.8L GM .....
Engine now has 4000 miles on it and still has relatively low manifold
vacuum. Vacuum is running 14-15 in hg. at idle and should be a few
inches MORE vac. to adequately run all the vacuum controls: Brake
booster, heater controls, dist. vacuum advance, *power piston* (2SE
carb), etc.
I checked and checked for manifold leaks, reset the damn manifold
gaskets three times.... etc.
Im pretty damn sure the problem is the engine 'mechanicals' .
Compression is 130 psig all cylinders
Mechanical valve timing has been degreed, and verified OK.
Ignition timing perfect - both by vacuum gauge (max rpm less 1/2" hg.)
and by accurate degreeing + timing light. --- both methods equate to
the same EXACT timing advance.
NO leaking vacuum hoses or controls.
If I remove a vac. hose from the manifold port the engine
**increases*** rpm --- which tells me I dont have a leak.
Poor vacuum causes power piston in carb to lift 'early' (for over-rich
mixture) - if I manually hold power piston / metering rod and remove a
manifold vac hose = same rpm increase.
Engine was broken in with 20 weight straight weight non-detergent oil.
Im about ready to dump a half can of cleanser down the carb to scuff
the cylinder walls in desparation and run the valve lifters with ZERO
lash ......
Your sage advice would be appreciated. I need another 2-3 inches of
vacuum to make all the vac. controls, brake booster and power piston-ed
carb. to operate properly. Any advice of why this damn engine is
running 'short' by about 2-3 inches hg. of vacuum and what to do about
it would be VEEEEEEEERRRRRRRRRRYYYYYYYYY much appreciated.
;-)
Engine now has 4000 miles on it and still has relatively low manifold
vacuum. Vacuum is running 14-15 in hg. at idle and should be a few
inches MORE vac. to adequately run all the vacuum controls: Brake
booster, heater controls, dist. vacuum advance, *power piston* (2SE
carb), etc.
I checked and checked for manifold leaks, reset the damn manifold
gaskets three times.... etc.
Im pretty damn sure the problem is the engine 'mechanicals' .
Compression is 130 psig all cylinders
Mechanical valve timing has been degreed, and verified OK.
Ignition timing perfect - both by vacuum gauge (max rpm less 1/2" hg.)
and by accurate degreeing + timing light. --- both methods equate to
the same EXACT timing advance.
NO leaking vacuum hoses or controls.
If I remove a vac. hose from the manifold port the engine
**increases*** rpm --- which tells me I dont have a leak.
Poor vacuum causes power piston in carb to lift 'early' (for over-rich
mixture) - if I manually hold power piston / metering rod and remove a
manifold vac hose = same rpm increase.
Engine was broken in with 20 weight straight weight non-detergent oil.
Im about ready to dump a half can of cleanser down the carb to scuff
the cylinder walls in desparation and run the valve lifters with ZERO
lash ......
Your sage advice would be appreciated. I need another 2-3 inches of
vacuum to make all the vac. controls, brake booster and power piston-ed
carb. to operate properly. Any advice of why this damn engine is
running 'short' by about 2-3 inches hg. of vacuum and what to do about
it would be VEEEEEEEERRRRRRRRRRYYYYYYYYY much appreciated.
;-)
01-18-2005, 04:17 PM
#2
Guest
Posts: n/a
Re: Low Manifold Vacuum
That's not really low for a SMOG motor at idle. You may see that's
at the edge of the green zone: http://www.----------.com/vacuumgauge.jpg
And you have noticed it's up around twenty at the more efficient
operating Revolutions Per Minute. None of the accessories use vacuum,
unless used.
God Bless America, ßill O|||||||O
mailto:--------------------
Rich Hampel wrote:
>
> "problem" performance continues in a rebuilt 2.8L GM .....
> Engine now has 4000 miles on it and still has relatively low manifold
> vacuum. Vacuum is running 14-15 in hg. at idle and should be a few
> inches MORE vac. to adequately run all the vacuum controls: Brake
> booster, heater controls, dist. vacuum advance, *power piston* (2SE
> carb), etc.
>
> I checked and checked for manifold leaks, reset the damn manifold
> gaskets three times.... etc.
> Im pretty damn sure the problem is the engine 'mechanicals' .
> Compression is 130 psig all cylinders
> Mechanical valve timing has been degreed, and verified OK.
> Ignition timing perfect - both by vacuum gauge (max rpm less 1/2" hg.)
> and by accurate degreeing + timing light. --- both methods equate to
> the same EXACT timing advance.
> NO leaking vacuum hoses or controls.
> If I remove a vac. hose from the manifold port the engine
> **increases*** rpm --- which tells me I dont have a leak.
> Poor vacuum causes power piston in carb to lift 'early' (for over-rich
> mixture) - if I manually hold power piston / metering rod and remove a
> manifold vac hose = same rpm increase.
>
> Engine was broken in with 20 weight straight weight non-detergent oil.
>
> Im about ready to dump a half can of cleanser down the carb to scuff
> the cylinder walls in desparation and run the valve lifters with ZERO
> lash ......
>
> Your sage advice would be appreciated. I need another 2-3 inches of
> vacuum to make all the vac. controls, brake booster and power piston-ed
> carb. to operate properly. Any advice of why this damn engine is
> running 'short' by about 2-3 inches hg. of vacuum and what to do about
> it would be VEEEEEEEERRRRRRRRRRYYYYYYYYY much appreciated.
>
> ;-)
at the edge of the green zone: http://www.----------.com/vacuumgauge.jpg
And you have noticed it's up around twenty at the more efficient
operating Revolutions Per Minute. None of the accessories use vacuum,
unless used.
God Bless America, ßill O|||||||O
mailto:--------------------
Rich Hampel wrote:
>
> "problem" performance continues in a rebuilt 2.8L GM .....
> Engine now has 4000 miles on it and still has relatively low manifold
> vacuum. Vacuum is running 14-15 in hg. at idle and should be a few
> inches MORE vac. to adequately run all the vacuum controls: Brake
> booster, heater controls, dist. vacuum advance, *power piston* (2SE
> carb), etc.
>
> I checked and checked for manifold leaks, reset the damn manifold
> gaskets three times.... etc.
> Im pretty damn sure the problem is the engine 'mechanicals' .
> Compression is 130 psig all cylinders
> Mechanical valve timing has been degreed, and verified OK.
> Ignition timing perfect - both by vacuum gauge (max rpm less 1/2" hg.)
> and by accurate degreeing + timing light. --- both methods equate to
> the same EXACT timing advance.
> NO leaking vacuum hoses or controls.
> If I remove a vac. hose from the manifold port the engine
> **increases*** rpm --- which tells me I dont have a leak.
> Poor vacuum causes power piston in carb to lift 'early' (for over-rich
> mixture) - if I manually hold power piston / metering rod and remove a
> manifold vac hose = same rpm increase.
>
> Engine was broken in with 20 weight straight weight non-detergent oil.
>
> Im about ready to dump a half can of cleanser down the carb to scuff
> the cylinder walls in desparation and run the valve lifters with ZERO
> lash ......
>
> Your sage advice would be appreciated. I need another 2-3 inches of
> vacuum to make all the vac. controls, brake booster and power piston-ed
> carb. to operate properly. Any advice of why this damn engine is
> running 'short' by about 2-3 inches hg. of vacuum and what to do about
> it would be VEEEEEEEERRRRRRRRRRYYYYYYYYY much appreciated.
>
> ;-)
01-18-2005, 04:17 PM
#3
Guest
Posts: n/a
Re: Low Manifold Vacuum
That's not really low for a SMOG motor at idle. You may see that's
at the edge of the green zone: http://www.----------.com/vacuumgauge.jpg
And you have noticed it's up around twenty at the more efficient
operating Revolutions Per Minute. None of the accessories use vacuum,
unless used.
God Bless America, ßill O|||||||O
mailto:--------------------
Rich Hampel wrote:
>
> "problem" performance continues in a rebuilt 2.8L GM .....
> Engine now has 4000 miles on it and still has relatively low manifold
> vacuum. Vacuum is running 14-15 in hg. at idle and should be a few
> inches MORE vac. to adequately run all the vacuum controls: Brake
> booster, heater controls, dist. vacuum advance, *power piston* (2SE
> carb), etc.
>
> I checked and checked for manifold leaks, reset the damn manifold
> gaskets three times.... etc.
> Im pretty damn sure the problem is the engine 'mechanicals' .
> Compression is 130 psig all cylinders
> Mechanical valve timing has been degreed, and verified OK.
> Ignition timing perfect - both by vacuum gauge (max rpm less 1/2" hg.)
> and by accurate degreeing + timing light. --- both methods equate to
> the same EXACT timing advance.
> NO leaking vacuum hoses or controls.
> If I remove a vac. hose from the manifold port the engine
> **increases*** rpm --- which tells me I dont have a leak.
> Poor vacuum causes power piston in carb to lift 'early' (for over-rich
> mixture) - if I manually hold power piston / metering rod and remove a
> manifold vac hose = same rpm increase.
>
> Engine was broken in with 20 weight straight weight non-detergent oil.
>
> Im about ready to dump a half can of cleanser down the carb to scuff
> the cylinder walls in desparation and run the valve lifters with ZERO
> lash ......
>
> Your sage advice would be appreciated. I need another 2-3 inches of
> vacuum to make all the vac. controls, brake booster and power piston-ed
> carb. to operate properly. Any advice of why this damn engine is
> running 'short' by about 2-3 inches hg. of vacuum and what to do about
> it would be VEEEEEEEERRRRRRRRRRYYYYYYYYY much appreciated.
>
> ;-)
at the edge of the green zone: http://www.----------.com/vacuumgauge.jpg
And you have noticed it's up around twenty at the more efficient
operating Revolutions Per Minute. None of the accessories use vacuum,
unless used.
God Bless America, ßill O|||||||O
mailto:--------------------
Rich Hampel wrote:
>
> "problem" performance continues in a rebuilt 2.8L GM .....
> Engine now has 4000 miles on it and still has relatively low manifold
> vacuum. Vacuum is running 14-15 in hg. at idle and should be a few
> inches MORE vac. to adequately run all the vacuum controls: Brake
> booster, heater controls, dist. vacuum advance, *power piston* (2SE
> carb), etc.
>
> I checked and checked for manifold leaks, reset the damn manifold
> gaskets three times.... etc.
> Im pretty damn sure the problem is the engine 'mechanicals' .
> Compression is 130 psig all cylinders
> Mechanical valve timing has been degreed, and verified OK.
> Ignition timing perfect - both by vacuum gauge (max rpm less 1/2" hg.)
> and by accurate degreeing + timing light. --- both methods equate to
> the same EXACT timing advance.
> NO leaking vacuum hoses or controls.
> If I remove a vac. hose from the manifold port the engine
> **increases*** rpm --- which tells me I dont have a leak.
> Poor vacuum causes power piston in carb to lift 'early' (for over-rich
> mixture) - if I manually hold power piston / metering rod and remove a
> manifold vac hose = same rpm increase.
>
> Engine was broken in with 20 weight straight weight non-detergent oil.
>
> Im about ready to dump a half can of cleanser down the carb to scuff
> the cylinder walls in desparation and run the valve lifters with ZERO
> lash ......
>
> Your sage advice would be appreciated. I need another 2-3 inches of
> vacuum to make all the vac. controls, brake booster and power piston-ed
> carb. to operate properly. Any advice of why this damn engine is
> running 'short' by about 2-3 inches hg. of vacuum and what to do about
> it would be VEEEEEEEERRRRRRRRRRYYYYYYYYY much appreciated.
>
> ;-)
01-18-2005, 04:17 PM
#4
Guest
Posts: n/a
Re: Low Manifold Vacuum
That's not really low for a SMOG motor at idle. You may see that's
at the edge of the green zone: http://www.----------.com/vacuumgauge.jpg
And you have noticed it's up around twenty at the more efficient
operating Revolutions Per Minute. None of the accessories use vacuum,
unless used.
God Bless America, ßill O|||||||O
mailto:--------------------
Rich Hampel wrote:
>
> "problem" performance continues in a rebuilt 2.8L GM .....
> Engine now has 4000 miles on it and still has relatively low manifold
> vacuum. Vacuum is running 14-15 in hg. at idle and should be a few
> inches MORE vac. to adequately run all the vacuum controls: Brake
> booster, heater controls, dist. vacuum advance, *power piston* (2SE
> carb), etc.
>
> I checked and checked for manifold leaks, reset the damn manifold
> gaskets three times.... etc.
> Im pretty damn sure the problem is the engine 'mechanicals' .
> Compression is 130 psig all cylinders
> Mechanical valve timing has been degreed, and verified OK.
> Ignition timing perfect - both by vacuum gauge (max rpm less 1/2" hg.)
> and by accurate degreeing + timing light. --- both methods equate to
> the same EXACT timing advance.
> NO leaking vacuum hoses or controls.
> If I remove a vac. hose from the manifold port the engine
> **increases*** rpm --- which tells me I dont have a leak.
> Poor vacuum causes power piston in carb to lift 'early' (for over-rich
> mixture) - if I manually hold power piston / metering rod and remove a
> manifold vac hose = same rpm increase.
>
> Engine was broken in with 20 weight straight weight non-detergent oil.
>
> Im about ready to dump a half can of cleanser down the carb to scuff
> the cylinder walls in desparation and run the valve lifters with ZERO
> lash ......
>
> Your sage advice would be appreciated. I need another 2-3 inches of
> vacuum to make all the vac. controls, brake booster and power piston-ed
> carb. to operate properly. Any advice of why this damn engine is
> running 'short' by about 2-3 inches hg. of vacuum and what to do about
> it would be VEEEEEEEERRRRRRRRRRYYYYYYYYY much appreciated.
>
> ;-)
at the edge of the green zone: http://www.----------.com/vacuumgauge.jpg
And you have noticed it's up around twenty at the more efficient
operating Revolutions Per Minute. None of the accessories use vacuum,
unless used.
God Bless America, ßill O|||||||O
mailto:--------------------
Rich Hampel wrote:
>
> "problem" performance continues in a rebuilt 2.8L GM .....
> Engine now has 4000 miles on it and still has relatively low manifold
> vacuum. Vacuum is running 14-15 in hg. at idle and should be a few
> inches MORE vac. to adequately run all the vacuum controls: Brake
> booster, heater controls, dist. vacuum advance, *power piston* (2SE
> carb), etc.
>
> I checked and checked for manifold leaks, reset the damn manifold
> gaskets three times.... etc.
> Im pretty damn sure the problem is the engine 'mechanicals' .
> Compression is 130 psig all cylinders
> Mechanical valve timing has been degreed, and verified OK.
> Ignition timing perfect - both by vacuum gauge (max rpm less 1/2" hg.)
> and by accurate degreeing + timing light. --- both methods equate to
> the same EXACT timing advance.
> NO leaking vacuum hoses or controls.
> If I remove a vac. hose from the manifold port the engine
> **increases*** rpm --- which tells me I dont have a leak.
> Poor vacuum causes power piston in carb to lift 'early' (for over-rich
> mixture) - if I manually hold power piston / metering rod and remove a
> manifold vac hose = same rpm increase.
>
> Engine was broken in with 20 weight straight weight non-detergent oil.
>
> Im about ready to dump a half can of cleanser down the carb to scuff
> the cylinder walls in desparation and run the valve lifters with ZERO
> lash ......
>
> Your sage advice would be appreciated. I need another 2-3 inches of
> vacuum to make all the vac. controls, brake booster and power piston-ed
> carb. to operate properly. Any advice of why this damn engine is
> running 'short' by about 2-3 inches hg. of vacuum and what to do about
> it would be VEEEEEEEERRRRRRRRRRYYYYYYYYY much appreciated.
>
> ;-)
01-18-2005, 04:17 PM
#5
Guest
Posts: n/a
Re: Low Manifold Vacuum
1st up, I'm not familiar with the 2.8, but is it possible you have a leak in
your brake servo ? You say the problem continues in a new engine ?
Dave Milne, Scotland
'91 Grand Wagoneer, '99 TJ
"Rich Hampel" <RhmpL33@nospam.net> wrote in message
news:180120051536111216%RhmpL33@nospam.net...
> "problem" performance continues in a rebuilt 2.8L GM .....
> Engine now has 4000 miles on it and still has relatively low manifold
> vacuum. Vacuum is running 14-15 in hg. at idle and should be a few
> inches MORE vac. to adequately run all the vacuum controls: Brake
> booster, heater controls, dist. vacuum advance, *power piston* (2SE
> carb), etc.
>
> I checked and checked for manifold leaks, reset the damn manifold
> gaskets three times.... etc.
> Im pretty damn sure the problem is the engine 'mechanicals' .
> Compression is 130 psig all cylinders
> Mechanical valve timing has been degreed, and verified OK.
> Ignition timing perfect - both by vacuum gauge (max rpm less 1/2" hg.)
> and by accurate degreeing + timing light. --- both methods equate to
> the same EXACT timing advance.
> NO leaking vacuum hoses or controls.
> If I remove a vac. hose from the manifold port the engine
> **increases*** rpm --- which tells me I dont have a leak.
> Poor vacuum causes power piston in carb to lift 'early' (for over-rich
> mixture) - if I manually hold power piston / metering rod and remove a
> manifold vac hose = same rpm increase.
>
> Engine was broken in with 20 weight straight weight non-detergent oil.
>
> Im about ready to dump a half can of cleanser down the carb to scuff
> the cylinder walls in desparation and run the valve lifters with ZERO
> lash ......
>
> Your sage advice would be appreciated. I need another 2-3 inches of
> vacuum to make all the vac. controls, brake booster and power piston-ed
> carb. to operate properly. Any advice of why this damn engine is
> running 'short' by about 2-3 inches hg. of vacuum and what to do about
> it would be VEEEEEEEERRRRRRRRRRYYYYYYYYY much appreciated.
>
> ;-)
your brake servo ? You say the problem continues in a new engine ?
Dave Milne, Scotland
'91 Grand Wagoneer, '99 TJ
"Rich Hampel" <RhmpL33@nospam.net> wrote in message
news:180120051536111216%RhmpL33@nospam.net...
> "problem" performance continues in a rebuilt 2.8L GM .....
> Engine now has 4000 miles on it and still has relatively low manifold
> vacuum. Vacuum is running 14-15 in hg. at idle and should be a few
> inches MORE vac. to adequately run all the vacuum controls: Brake
> booster, heater controls, dist. vacuum advance, *power piston* (2SE
> carb), etc.
>
> I checked and checked for manifold leaks, reset the damn manifold
> gaskets three times.... etc.
> Im pretty damn sure the problem is the engine 'mechanicals' .
> Compression is 130 psig all cylinders
> Mechanical valve timing has been degreed, and verified OK.
> Ignition timing perfect - both by vacuum gauge (max rpm less 1/2" hg.)
> and by accurate degreeing + timing light. --- both methods equate to
> the same EXACT timing advance.
> NO leaking vacuum hoses or controls.
> If I remove a vac. hose from the manifold port the engine
> **increases*** rpm --- which tells me I dont have a leak.
> Poor vacuum causes power piston in carb to lift 'early' (for over-rich
> mixture) - if I manually hold power piston / metering rod and remove a
> manifold vac hose = same rpm increase.
>
> Engine was broken in with 20 weight straight weight non-detergent oil.
>
> Im about ready to dump a half can of cleanser down the carb to scuff
> the cylinder walls in desparation and run the valve lifters with ZERO
> lash ......
>
> Your sage advice would be appreciated. I need another 2-3 inches of
> vacuum to make all the vac. controls, brake booster and power piston-ed
> carb. to operate properly. Any advice of why this damn engine is
> running 'short' by about 2-3 inches hg. of vacuum and what to do about
> it would be VEEEEEEEERRRRRRRRRRYYYYYYYYY much appreciated.
>
> ;-)
01-18-2005, 04:17 PM
#6
Guest
Posts: n/a
Re: Low Manifold Vacuum
1st up, I'm not familiar with the 2.8, but is it possible you have a leak in
your brake servo ? You say the problem continues in a new engine ?
Dave Milne, Scotland
'91 Grand Wagoneer, '99 TJ
"Rich Hampel" <RhmpL33@nospam.net> wrote in message
news:180120051536111216%RhmpL33@nospam.net...
> "problem" performance continues in a rebuilt 2.8L GM .....
> Engine now has 4000 miles on it and still has relatively low manifold
> vacuum. Vacuum is running 14-15 in hg. at idle and should be a few
> inches MORE vac. to adequately run all the vacuum controls: Brake
> booster, heater controls, dist. vacuum advance, *power piston* (2SE
> carb), etc.
>
> I checked and checked for manifold leaks, reset the damn manifold
> gaskets three times.... etc.
> Im pretty damn sure the problem is the engine 'mechanicals' .
> Compression is 130 psig all cylinders
> Mechanical valve timing has been degreed, and verified OK.
> Ignition timing perfect - both by vacuum gauge (max rpm less 1/2" hg.)
> and by accurate degreeing + timing light. --- both methods equate to
> the same EXACT timing advance.
> NO leaking vacuum hoses or controls.
> If I remove a vac. hose from the manifold port the engine
> **increases*** rpm --- which tells me I dont have a leak.
> Poor vacuum causes power piston in carb to lift 'early' (for over-rich
> mixture) - if I manually hold power piston / metering rod and remove a
> manifold vac hose = same rpm increase.
>
> Engine was broken in with 20 weight straight weight non-detergent oil.
>
> Im about ready to dump a half can of cleanser down the carb to scuff
> the cylinder walls in desparation and run the valve lifters with ZERO
> lash ......
>
> Your sage advice would be appreciated. I need another 2-3 inches of
> vacuum to make all the vac. controls, brake booster and power piston-ed
> carb. to operate properly. Any advice of why this damn engine is
> running 'short' by about 2-3 inches hg. of vacuum and what to do about
> it would be VEEEEEEEERRRRRRRRRRYYYYYYYYY much appreciated.
>
> ;-)
your brake servo ? You say the problem continues in a new engine ?
Dave Milne, Scotland
'91 Grand Wagoneer, '99 TJ
"Rich Hampel" <RhmpL33@nospam.net> wrote in message
news:180120051536111216%RhmpL33@nospam.net...
> "problem" performance continues in a rebuilt 2.8L GM .....
> Engine now has 4000 miles on it and still has relatively low manifold
> vacuum. Vacuum is running 14-15 in hg. at idle and should be a few
> inches MORE vac. to adequately run all the vacuum controls: Brake
> booster, heater controls, dist. vacuum advance, *power piston* (2SE
> carb), etc.
>
> I checked and checked for manifold leaks, reset the damn manifold
> gaskets three times.... etc.
> Im pretty damn sure the problem is the engine 'mechanicals' .
> Compression is 130 psig all cylinders
> Mechanical valve timing has been degreed, and verified OK.
> Ignition timing perfect - both by vacuum gauge (max rpm less 1/2" hg.)
> and by accurate degreeing + timing light. --- both methods equate to
> the same EXACT timing advance.
> NO leaking vacuum hoses or controls.
> If I remove a vac. hose from the manifold port the engine
> **increases*** rpm --- which tells me I dont have a leak.
> Poor vacuum causes power piston in carb to lift 'early' (for over-rich
> mixture) - if I manually hold power piston / metering rod and remove a
> manifold vac hose = same rpm increase.
>
> Engine was broken in with 20 weight straight weight non-detergent oil.
>
> Im about ready to dump a half can of cleanser down the carb to scuff
> the cylinder walls in desparation and run the valve lifters with ZERO
> lash ......
>
> Your sage advice would be appreciated. I need another 2-3 inches of
> vacuum to make all the vac. controls, brake booster and power piston-ed
> carb. to operate properly. Any advice of why this damn engine is
> running 'short' by about 2-3 inches hg. of vacuum and what to do about
> it would be VEEEEEEEERRRRRRRRRRYYYYYYYYY much appreciated.
>
> ;-)
01-18-2005, 04:17 PM
#7
Guest
Posts: n/a
Re: Low Manifold Vacuum
1st up, I'm not familiar with the 2.8, but is it possible you have a leak in
your brake servo ? You say the problem continues in a new engine ?
Dave Milne, Scotland
'91 Grand Wagoneer, '99 TJ
"Rich Hampel" <RhmpL33@nospam.net> wrote in message
news:180120051536111216%RhmpL33@nospam.net...
> "problem" performance continues in a rebuilt 2.8L GM .....
> Engine now has 4000 miles on it and still has relatively low manifold
> vacuum. Vacuum is running 14-15 in hg. at idle and should be a few
> inches MORE vac. to adequately run all the vacuum controls: Brake
> booster, heater controls, dist. vacuum advance, *power piston* (2SE
> carb), etc.
>
> I checked and checked for manifold leaks, reset the damn manifold
> gaskets three times.... etc.
> Im pretty damn sure the problem is the engine 'mechanicals' .
> Compression is 130 psig all cylinders
> Mechanical valve timing has been degreed, and verified OK.
> Ignition timing perfect - both by vacuum gauge (max rpm less 1/2" hg.)
> and by accurate degreeing + timing light. --- both methods equate to
> the same EXACT timing advance.
> NO leaking vacuum hoses or controls.
> If I remove a vac. hose from the manifold port the engine
> **increases*** rpm --- which tells me I dont have a leak.
> Poor vacuum causes power piston in carb to lift 'early' (for over-rich
> mixture) - if I manually hold power piston / metering rod and remove a
> manifold vac hose = same rpm increase.
>
> Engine was broken in with 20 weight straight weight non-detergent oil.
>
> Im about ready to dump a half can of cleanser down the carb to scuff
> the cylinder walls in desparation and run the valve lifters with ZERO
> lash ......
>
> Your sage advice would be appreciated. I need another 2-3 inches of
> vacuum to make all the vac. controls, brake booster and power piston-ed
> carb. to operate properly. Any advice of why this damn engine is
> running 'short' by about 2-3 inches hg. of vacuum and what to do about
> it would be VEEEEEEEERRRRRRRRRRYYYYYYYYY much appreciated.
>
> ;-)
your brake servo ? You say the problem continues in a new engine ?
Dave Milne, Scotland
'91 Grand Wagoneer, '99 TJ
"Rich Hampel" <RhmpL33@nospam.net> wrote in message
news:180120051536111216%RhmpL33@nospam.net...
> "problem" performance continues in a rebuilt 2.8L GM .....
> Engine now has 4000 miles on it and still has relatively low manifold
> vacuum. Vacuum is running 14-15 in hg. at idle and should be a few
> inches MORE vac. to adequately run all the vacuum controls: Brake
> booster, heater controls, dist. vacuum advance, *power piston* (2SE
> carb), etc.
>
> I checked and checked for manifold leaks, reset the damn manifold
> gaskets three times.... etc.
> Im pretty damn sure the problem is the engine 'mechanicals' .
> Compression is 130 psig all cylinders
> Mechanical valve timing has been degreed, and verified OK.
> Ignition timing perfect - both by vacuum gauge (max rpm less 1/2" hg.)
> and by accurate degreeing + timing light. --- both methods equate to
> the same EXACT timing advance.
> NO leaking vacuum hoses or controls.
> If I remove a vac. hose from the manifold port the engine
> **increases*** rpm --- which tells me I dont have a leak.
> Poor vacuum causes power piston in carb to lift 'early' (for over-rich
> mixture) - if I manually hold power piston / metering rod and remove a
> manifold vac hose = same rpm increase.
>
> Engine was broken in with 20 weight straight weight non-detergent oil.
>
> Im about ready to dump a half can of cleanser down the carb to scuff
> the cylinder walls in desparation and run the valve lifters with ZERO
> lash ......
>
> Your sage advice would be appreciated. I need another 2-3 inches of
> vacuum to make all the vac. controls, brake booster and power piston-ed
> carb. to operate properly. Any advice of why this damn engine is
> running 'short' by about 2-3 inches hg. of vacuum and what to do about
> it would be VEEEEEEEERRRRRRRRRRYYYYYYYYY much appreciated.
>
> ;-)
01-18-2005, 04:41 PM
#8
Guest
Posts: n/a
Re: Low Manifold Vacuum
I would guess that your valves are a bit short on time if you don't have
zero lash on them. My book calls for zero.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Rich Hampel wrote:
>
> "problem" performance continues in a rebuilt 2.8L GM .....
> Engine now has 4000 miles on it and still has relatively low manifold
> vacuum. Vacuum is running 14-15 in hg. at idle and should be a few
> inches MORE vac. to adequately run all the vacuum controls: Brake
> booster, heater controls, dist. vacuum advance, *power piston* (2SE
> carb), etc.
>
> I checked and checked for manifold leaks, reset the damn manifold
> gaskets three times.... etc.
> Im pretty damn sure the problem is the engine 'mechanicals' .
> Compression is 130 psig all cylinders
> Mechanical valve timing has been degreed, and verified OK.
> Ignition timing perfect - both by vacuum gauge (max rpm less 1/2" hg.)
> and by accurate degreeing + timing light. --- both methods equate to
> the same EXACT timing advance.
> NO leaking vacuum hoses or controls.
> If I remove a vac. hose from the manifold port the engine
> **increases*** rpm --- which tells me I dont have a leak.
> Poor vacuum causes power piston in carb to lift 'early' (for over-rich
> mixture) - if I manually hold power piston / metering rod and remove a
> manifold vac hose = same rpm increase.
>
> Engine was broken in with 20 weight straight weight non-detergent oil.
>
> Im about ready to dump a half can of cleanser down the carb to scuff
> the cylinder walls in desparation and run the valve lifters with ZERO
> lash ......
>
> Your sage advice would be appreciated. I need another 2-3 inches of
> vacuum to make all the vac. controls, brake booster and power piston-ed
> carb. to operate properly. Any advice of why this damn engine is
> running 'short' by about 2-3 inches hg. of vacuum and what to do about
> it would be VEEEEEEEERRRRRRRRRRYYYYYYYYY much appreciated.
>
> ;-)
zero lash on them. My book calls for zero.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Rich Hampel wrote:
>
> "problem" performance continues in a rebuilt 2.8L GM .....
> Engine now has 4000 miles on it and still has relatively low manifold
> vacuum. Vacuum is running 14-15 in hg. at idle and should be a few
> inches MORE vac. to adequately run all the vacuum controls: Brake
> booster, heater controls, dist. vacuum advance, *power piston* (2SE
> carb), etc.
>
> I checked and checked for manifold leaks, reset the damn manifold
> gaskets three times.... etc.
> Im pretty damn sure the problem is the engine 'mechanicals' .
> Compression is 130 psig all cylinders
> Mechanical valve timing has been degreed, and verified OK.
> Ignition timing perfect - both by vacuum gauge (max rpm less 1/2" hg.)
> and by accurate degreeing + timing light. --- both methods equate to
> the same EXACT timing advance.
> NO leaking vacuum hoses or controls.
> If I remove a vac. hose from the manifold port the engine
> **increases*** rpm --- which tells me I dont have a leak.
> Poor vacuum causes power piston in carb to lift 'early' (for over-rich
> mixture) - if I manually hold power piston / metering rod and remove a
> manifold vac hose = same rpm increase.
>
> Engine was broken in with 20 weight straight weight non-detergent oil.
>
> Im about ready to dump a half can of cleanser down the carb to scuff
> the cylinder walls in desparation and run the valve lifters with ZERO
> lash ......
>
> Your sage advice would be appreciated. I need another 2-3 inches of
> vacuum to make all the vac. controls, brake booster and power piston-ed
> carb. to operate properly. Any advice of why this damn engine is
> running 'short' by about 2-3 inches hg. of vacuum and what to do about
> it would be VEEEEEEEERRRRRRRRRRYYYYYYYYY much appreciated.
>
> ;-)
01-18-2005, 04:41 PM
#9
Guest
Posts: n/a
Re: Low Manifold Vacuum
I would guess that your valves are a bit short on time if you don't have
zero lash on them. My book calls for zero.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Rich Hampel wrote:
>
> "problem" performance continues in a rebuilt 2.8L GM .....
> Engine now has 4000 miles on it and still has relatively low manifold
> vacuum. Vacuum is running 14-15 in hg. at idle and should be a few
> inches MORE vac. to adequately run all the vacuum controls: Brake
> booster, heater controls, dist. vacuum advance, *power piston* (2SE
> carb), etc.
>
> I checked and checked for manifold leaks, reset the damn manifold
> gaskets three times.... etc.
> Im pretty damn sure the problem is the engine 'mechanicals' .
> Compression is 130 psig all cylinders
> Mechanical valve timing has been degreed, and verified OK.
> Ignition timing perfect - both by vacuum gauge (max rpm less 1/2" hg.)
> and by accurate degreeing + timing light. --- both methods equate to
> the same EXACT timing advance.
> NO leaking vacuum hoses or controls.
> If I remove a vac. hose from the manifold port the engine
> **increases*** rpm --- which tells me I dont have a leak.
> Poor vacuum causes power piston in carb to lift 'early' (for over-rich
> mixture) - if I manually hold power piston / metering rod and remove a
> manifold vac hose = same rpm increase.
>
> Engine was broken in with 20 weight straight weight non-detergent oil.
>
> Im about ready to dump a half can of cleanser down the carb to scuff
> the cylinder walls in desparation and run the valve lifters with ZERO
> lash ......
>
> Your sage advice would be appreciated. I need another 2-3 inches of
> vacuum to make all the vac. controls, brake booster and power piston-ed
> carb. to operate properly. Any advice of why this damn engine is
> running 'short' by about 2-3 inches hg. of vacuum and what to do about
> it would be VEEEEEEEERRRRRRRRRRYYYYYYYYY much appreciated.
>
> ;-)
zero lash on them. My book calls for zero.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Rich Hampel wrote:
>
> "problem" performance continues in a rebuilt 2.8L GM .....
> Engine now has 4000 miles on it and still has relatively low manifold
> vacuum. Vacuum is running 14-15 in hg. at idle and should be a few
> inches MORE vac. to adequately run all the vacuum controls: Brake
> booster, heater controls, dist. vacuum advance, *power piston* (2SE
> carb), etc.
>
> I checked and checked for manifold leaks, reset the damn manifold
> gaskets three times.... etc.
> Im pretty damn sure the problem is the engine 'mechanicals' .
> Compression is 130 psig all cylinders
> Mechanical valve timing has been degreed, and verified OK.
> Ignition timing perfect - both by vacuum gauge (max rpm less 1/2" hg.)
> and by accurate degreeing + timing light. --- both methods equate to
> the same EXACT timing advance.
> NO leaking vacuum hoses or controls.
> If I remove a vac. hose from the manifold port the engine
> **increases*** rpm --- which tells me I dont have a leak.
> Poor vacuum causes power piston in carb to lift 'early' (for over-rich
> mixture) - if I manually hold power piston / metering rod and remove a
> manifold vac hose = same rpm increase.
>
> Engine was broken in with 20 weight straight weight non-detergent oil.
>
> Im about ready to dump a half can of cleanser down the carb to scuff
> the cylinder walls in desparation and run the valve lifters with ZERO
> lash ......
>
> Your sage advice would be appreciated. I need another 2-3 inches of
> vacuum to make all the vac. controls, brake booster and power piston-ed
> carb. to operate properly. Any advice of why this damn engine is
> running 'short' by about 2-3 inches hg. of vacuum and what to do about
> it would be VEEEEEEEERRRRRRRRRRYYYYYYYYY much appreciated.
>
> ;-)
01-18-2005, 04:41 PM
#10
Guest
Posts: n/a
Re: Low Manifold Vacuum
I would guess that your valves are a bit short on time if you don't have
zero lash on them. My book calls for zero.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Rich Hampel wrote:
>
> "problem" performance continues in a rebuilt 2.8L GM .....
> Engine now has 4000 miles on it and still has relatively low manifold
> vacuum. Vacuum is running 14-15 in hg. at idle and should be a few
> inches MORE vac. to adequately run all the vacuum controls: Brake
> booster, heater controls, dist. vacuum advance, *power piston* (2SE
> carb), etc.
>
> I checked and checked for manifold leaks, reset the damn manifold
> gaskets three times.... etc.
> Im pretty damn sure the problem is the engine 'mechanicals' .
> Compression is 130 psig all cylinders
> Mechanical valve timing has been degreed, and verified OK.
> Ignition timing perfect - both by vacuum gauge (max rpm less 1/2" hg.)
> and by accurate degreeing + timing light. --- both methods equate to
> the same EXACT timing advance.
> NO leaking vacuum hoses or controls.
> If I remove a vac. hose from the manifold port the engine
> **increases*** rpm --- which tells me I dont have a leak.
> Poor vacuum causes power piston in carb to lift 'early' (for over-rich
> mixture) - if I manually hold power piston / metering rod and remove a
> manifold vac hose = same rpm increase.
>
> Engine was broken in with 20 weight straight weight non-detergent oil.
>
> Im about ready to dump a half can of cleanser down the carb to scuff
> the cylinder walls in desparation and run the valve lifters with ZERO
> lash ......
>
> Your sage advice would be appreciated. I need another 2-3 inches of
> vacuum to make all the vac. controls, brake booster and power piston-ed
> carb. to operate properly. Any advice of why this damn engine is
> running 'short' by about 2-3 inches hg. of vacuum and what to do about
> it would be VEEEEEEEERRRRRRRRRRYYYYYYYYY much appreciated.
>
> ;-)
zero lash on them. My book calls for zero.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Rich Hampel wrote:
>
> "problem" performance continues in a rebuilt 2.8L GM .....
> Engine now has 4000 miles on it and still has relatively low manifold
> vacuum. Vacuum is running 14-15 in hg. at idle and should be a few
> inches MORE vac. to adequately run all the vacuum controls: Brake
> booster, heater controls, dist. vacuum advance, *power piston* (2SE
> carb), etc.
>
> I checked and checked for manifold leaks, reset the damn manifold
> gaskets three times.... etc.
> Im pretty damn sure the problem is the engine 'mechanicals' .
> Compression is 130 psig all cylinders
> Mechanical valve timing has been degreed, and verified OK.
> Ignition timing perfect - both by vacuum gauge (max rpm less 1/2" hg.)
> and by accurate degreeing + timing light. --- both methods equate to
> the same EXACT timing advance.
> NO leaking vacuum hoses or controls.
> If I remove a vac. hose from the manifold port the engine
> **increases*** rpm --- which tells me I dont have a leak.
> Poor vacuum causes power piston in carb to lift 'early' (for over-rich
> mixture) - if I manually hold power piston / metering rod and remove a
> manifold vac hose = same rpm increase.
>
> Engine was broken in with 20 weight straight weight non-detergent oil.
>
> Im about ready to dump a half can of cleanser down the carb to scuff
> the cylinder walls in desparation and run the valve lifters with ZERO
> lash ......
>
> Your sage advice would be appreciated. I need another 2-3 inches of
> vacuum to make all the vac. controls, brake booster and power piston-ed
> carb. to operate properly. Any advice of why this damn engine is
> running 'short' by about 2-3 inches hg. of vacuum and what to do about
> it would be VEEEEEEEERRRRRRRRRRYYYYYYYYY much appreciated.
>
> ;-)
