Re: CJ5 misfires at high RPM/hard acceleration
 

In article <1184542280.091378.265490@o61g2000hsh.googlegroups .com>,
<matthew.nye@gmail.com> wrote:

> Thanks for everyone's replies. Here's what I've done from your
> suggestions:

Yes the ballast resistor can go either way. The gas you see
squirting out when you move the linkage has nothing to do with the
secondaries working or not. Although the 600 is "in theory" a little
large for a stock 304, if it's tuned right there is no problem. I have
a Holley 600 on a 289 that runs perfectly.

I agree that your total timing is on the conservative side, but I
don't think it would cause your particular symptoms. I had a 390 in a
station wagon that would eventually get up to 70mph, but only at light
enough throttle where the vacuum stayed high. When I started to put my
foot down, it would actually *decelerate*. Nothing I did with the
distributor changed that. (I bought it in this condition, so I had no
frame of reference). The previous owner had the timing apparently set
right. But, just because the distributor is firing with the crank
doesn't mean the cam is in the right place. Of course, it turned out to
be the chain.

Re: CJ5 misfires at high RPM/hard acceleration
 

In article <1184542280.091378.265490@o61g2000hsh.googlegroups .com>,
<matthew.nye@gmail.com> wrote:

> Thanks for everyone's replies. Here's what I've done from your
> suggestions:

Yes the ballast resistor can go either way. The gas you see
squirting out when you move the linkage has nothing to do with the
secondaries working or not. Although the 600 is "in theory" a little
large for a stock 304, if it's tuned right there is no problem. I have
a Holley 600 on a 289 that runs perfectly.

I agree that your total timing is on the conservative side, but I
don't think it would cause your particular symptoms. I had a 390 in a
station wagon that would eventually get up to 70mph, but only at light
enough throttle where the vacuum stayed high. When I started to put my
foot down, it would actually *decelerate*. Nothing I did with the
distributor changed that. (I bought it in this condition, so I had no
frame of reference). The previous owner had the timing apparently set
right. But, just because the distributor is firing with the crank
doesn't mean the cam is in the right place. Of course, it turned out to
be the chain.

Re: CJ5 misfires at high RPM/hard acceleration
 

In article <1184542280.091378.265490@o61g2000hsh.googlegroups .com>,
<matthew.nye@gmail.com> wrote:

> Thanks for everyone's replies. Here's what I've done from your
> suggestions:

Yes the ballast resistor can go either way. The gas you see
squirting out when you move the linkage has nothing to do with the
secondaries working or not. Although the 600 is "in theory" a little
large for a stock 304, if it's tuned right there is no problem. I have
a Holley 600 on a 289 that runs perfectly.

I agree that your total timing is on the conservative side, but I
don't think it would cause your particular symptoms. I had a 390 in a
station wagon that would eventually get up to 70mph, but only at light
enough throttle where the vacuum stayed high. When I started to put my
foot down, it would actually *decelerate*. Nothing I did with the
distributor changed that. (I bought it in this condition, so I had no
frame of reference). The previous owner had the timing apparently set
right. But, just because the distributor is firing with the crank
doesn't mean the cam is in the right place. Of course, it turned out to
be the chain.

Re: CJ5 misfires at high RPM/hard acceleration
 

matthew.nye@gmail.com wrote:
> Thanks for everyone's replies. Here's what I've done from your
> suggestions:
>
> - Having the gas cap off made no difference. I actually don't have
> any of the emissions stuff on it, so there's no canister, just the gas
> tank to the pump.
> - Having the coil's + lead hooked directly to the battery made no
> difference, I tried switching the leads on the ballast resistor too
> first to see if I had it hooked up wrong. I may be wrong, but I think
> the ballast resistor leads can go either way?
> - I tried what Roy suggested with interesting results. When I
> advanced the engine to 10 or 15 degrees, it would run noticeably
> better, but not perfect. I could actually get the secondaries to open
> up on the carb before it crapped out, which I haven't been able to do
> since the fuel pump change. I was grabbing at straws when I replaced
> the vacuum advance. I could suck air right through it with my mouth
> so I knew it was bad, that & having it plugged in at idle made no
> difference in timing advance. When I have the new one plugged in, it
> automatically advances it to about 10 BTDC at idle. I didn't see any
> adjustments on it, but maybe that's what is wrong? I couldn't get the
> engine started with it advanced so far when testing, I could only test
> it out by having it started first & then advancing it. The idle was
> terrible with a lot of misfiring at that point, if that means
> anything.
> - I've had a few people also tell me it's over carbureted, but that's
> what has always been on it (my dad owned it for like about 15 years
> before me) & it seemed to have ran fine for the longest time. That is
> an interesting theory though that the old pump could have just been so
> tired that it didn't put enough pressure through to put it at it's
> full potential. I was considering a 500cfm 2-bbl holley if I had to
> purchase one, but it sounds like that might be too much as well? To
> clarify, the pump just started leaking when it went out, it didn't
> seize up or anything, in fact I didn't know it was going bad until I
> started getting sprayed with gas (there's no fenders, windshield,
> etc). I don't know if I cleaned the jets out good enough when I
> rebuilt the carb, so it's a possibility that part of the diaphragm got
> stuck in it. it does seem to flow OK though when I look at the spray
> coming out of the jets.
> - The vacuum is very steady at idle, maybe 1hg of movement at most
> from side to side. I have not performed a compression check, what
> would that tell me if it were low? I don't have a compression tester
> available so I'm not going to be able to do that one right away.
> - The plugs are bosch platinums with a heat rating of 9. I'm not sure
> what that equates to heat-wise though, is that a standard across all
> plugs?\
>
> Any suggestions on the distributor? I checked the springs & weights
> of the centrifugal advance & they seem to be nice & responsive, but
> then again, I'm not sure what they're supposed to look like. Should I
> try replacing the entire distributor before I go crazy & take the
> entire front of my engine apart for the timing chain or start messing
> with the carb? Is there any way to test whether or not the timing
> chain has slipped a tooth without actually looking at it?
>
> Thanks again guys,
>
> -Matt
>

I really think your problem is the timing, and could be caused by a few
different things. Engines with aftermarket headers, cams, etc. usually
like a little more timing. As long as you aren't experiencing ping and
the starter doesn't kick back when the engine is hot, you're not hurting
anything.

An engine with not enough timing advance will do exactly what yours is
doing. It will also seem like it is running rich because the fuel
mixture is exiting the cylinder before is has had time to completely
burn. the popping noise you're hearing is actually from the exhaust
valve opening while the mixture is still burning.

If you have access to a timing light with the dial adjustable advance on
it, check the timing at idle with the vacuum advance disconnected, then
rev the engine to about 3000-3500 RPM and check it there. It should have
advance to about 30-34 degrees. If it is much less than this, then your
mechanical advance is not functioning properly. My guess is that this is
what is happening. IF you are not getting 30-34 degrees, you can test to
see if the additional timing fixes the problem by advancing the timing
to get about 30 degrees at 3000 RPM. One word of caution when doing
this: you are compensating for a malfunctioning mechanical advance and
will have a lot of timing at idle, so when you do your acceleration test
like this, go light on the gas pedal to prevent a ton of pinging.

There is a slight possibility that the outer ring on your balancer has
slipped on the rubber ring between the outer ring and the hub. This is
one thing that would explain the timing issue. An

One thing that comes to mind that I have seen people forget during a
Holley rebuild is the little needle check that goes in the fuel passage
underneath the accelerator pump nozzle. If you leave that out, the
engine vacuum at higher RPM can cause fuel to flow out the nozzle. It
also causes other problems, which you don't seem to be experiencing, so
it is probably in there.

A 600 may not be ideal for a 304, but it can be made to run just fine.
There are literally thousands of 302 Fords, 305 Chevys and 318 Mopars
running Holey 600 carbs on them. I am assuming you probably have the
Holley model 1850 (probably with a dash number after it) The number will
be on the front of the choke horn. The problem with these carbs is that
they are set up to run on a wide range of engines, and are very rarely
perfect out of the box for your particular application. they are
normally tuned a bit rich as far as jetting goes, but nothing extreme.

If the engine runs the best with the mixture screws turned all the way
in, or close to it, then obviously it is running too rich.

Hook your vacuum gage up to manifold vacuum, which is any point below
the throttle plates. Going by your vacuum reading, you're in the right
spot now. Set your idle speed to the proper RPM and then remove the
sight plug for the float level and adjust it so that the fuel level is
just below the hole. By rocking the vehicle slightly, you should see the
gas flow out of the sight hole just a little bit.

Now using your vacuum gage, set the idle mixture screws to achieve the
highest vacuum reading at idle. If the idle speed rises when you make
adjustments, then reset the RPM to the correct level. A well tuned
engine with a stock camshaft should have about 20" of vacuum, but an
engine with a lot of miles will read less. Worn rings and valve seats
will reduce vacuum.

Try the timing test and see what happens. The carb tips I gave you will
probably not affect your misfire condition, but were more for when you
get to the point of tuning the carb.

Chris

Re: CJ5 misfires at high RPM/hard acceleration
 

matthew.nye@gmail.com wrote:
> Thanks for everyone's replies. Here's what I've done from your
> suggestions:
>
> - Having the gas cap off made no difference. I actually don't have
> any of the emissions stuff on it, so there's no canister, just the gas
> tank to the pump.
> - Having the coil's + lead hooked directly to the battery made no
> difference, I tried switching the leads on the ballast resistor too
> first to see if I had it hooked up wrong. I may be wrong, but I think
> the ballast resistor leads can go either way?
> - I tried what Roy suggested with interesting results. When I
> advanced the engine to 10 or 15 degrees, it would run noticeably
> better, but not perfect. I could actually get the secondaries to open
> up on the carb before it crapped out, which I haven't been able to do
> since the fuel pump change. I was grabbing at straws when I replaced
> the vacuum advance. I could suck air right through it with my mouth
> so I knew it was bad, that & having it plugged in at idle made no
> difference in timing advance. When I have the new one plugged in, it
> automatically advances it to about 10 BTDC at idle. I didn't see any
> adjustments on it, but maybe that's what is wrong? I couldn't get the
> engine started with it advanced so far when testing, I could only test
> it out by having it started first & then advancing it. The idle was
> terrible with a lot of misfiring at that point, if that means
> anything.
> - I've had a few people also tell me it's over carbureted, but that's
> what has always been on it (my dad owned it for like about 15 years
> before me) & it seemed to have ran fine for the longest time. That is
> an interesting theory though that the old pump could have just been so
> tired that it didn't put enough pressure through to put it at it's
> full potential. I was considering a 500cfm 2-bbl holley if I had to
> purchase one, but it sounds like that might be too much as well? To
> clarify, the pump just started leaking when it went out, it didn't
> seize up or anything, in fact I didn't know it was going bad until I
> started getting sprayed with gas (there's no fenders, windshield,
> etc). I don't know if I cleaned the jets out good enough when I
> rebuilt the carb, so it's a possibility that part of the diaphragm got
> stuck in it. it does seem to flow OK though when I look at the spray
> coming out of the jets.
> - The vacuum is very steady at idle, maybe 1hg of movement at most
> from side to side. I have not performed a compression check, what
> would that tell me if it were low? I don't have a compression tester
> available so I'm not going to be able to do that one right away.
> - The plugs are bosch platinums with a heat rating of 9. I'm not sure
> what that equates to heat-wise though, is that a standard across all
> plugs?\
>
> Any suggestions on the distributor? I checked the springs & weights
> of the centrifugal advance & they seem to be nice & responsive, but
> then again, I'm not sure what they're supposed to look like. Should I
> try replacing the entire distributor before I go crazy & take the
> entire front of my engine apart for the timing chain or start messing
> with the carb? Is there any way to test whether or not the timing
> chain has slipped a tooth without actually looking at it?
>
> Thanks again guys,
>
> -Matt
>

I really think your problem is the timing, and could be caused by a few
different things. Engines with aftermarket headers, cams, etc. usually
like a little more timing. As long as you aren't experiencing ping and
the starter doesn't kick back when the engine is hot, you're not hurting
anything.

An engine with not enough timing advance will do exactly what yours is
doing. It will also seem like it is running rich because the fuel
mixture is exiting the cylinder before is has had time to completely
burn. the popping noise you're hearing is actually from the exhaust
valve opening while the mixture is still burning.

If you have access to a timing light with the dial adjustable advance on
it, check the timing at idle with the vacuum advance disconnected, then
rev the engine to about 3000-3500 RPM and check it there. It should have
advance to about 30-34 degrees. If it is much less than this, then your
mechanical advance is not functioning properly. My guess is that this is
what is happening. IF you are not getting 30-34 degrees, you can test to
see if the additional timing fixes the problem by advancing the timing
to get about 30 degrees at 3000 RPM. One word of caution when doing
this: you are compensating for a malfunctioning mechanical advance and
will have a lot of timing at idle, so when you do your acceleration test
like this, go light on the gas pedal to prevent a ton of pinging.

There is a slight possibility that the outer ring on your balancer has
slipped on the rubber ring between the outer ring and the hub. This is
one thing that would explain the timing issue. An

One thing that comes to mind that I have seen people forget during a
Holley rebuild is the little needle check that goes in the fuel passage
underneath the accelerator pump nozzle. If you leave that out, the
engine vacuum at higher RPM can cause fuel to flow out the nozzle. It
also causes other problems, which you don't seem to be experiencing, so
it is probably in there.

A 600 may not be ideal for a 304, but it can be made to run just fine.
There are literally thousands of 302 Fords, 305 Chevys and 318 Mopars
running Holey 600 carbs on them. I am assuming you probably have the
Holley model 1850 (probably with a dash number after it) The number will
be on the front of the choke horn. The problem with these carbs is that
they are set up to run on a wide range of engines, and are very rarely
perfect out of the box for your particular application. they are
normally tuned a bit rich as far as jetting goes, but nothing extreme.

If the engine runs the best with the mixture screws turned all the way
in, or close to it, then obviously it is running too rich.

Hook your vacuum gage up to manifold vacuum, which is any point below
the throttle plates. Going by your vacuum reading, you're in the right
spot now. Set your idle speed to the proper RPM and then remove the
sight plug for the float level and adjust it so that the fuel level is
just below the hole. By rocking the vehicle slightly, you should see the
gas flow out of the sight hole just a little bit.

Now using your vacuum gage, set the idle mixture screws to achieve the
highest vacuum reading at idle. If the idle speed rises when you make
adjustments, then reset the RPM to the correct level. A well tuned
engine with a stock camshaft should have about 20" of vacuum, but an
engine with a lot of miles will read less. Worn rings and valve seats
will reduce vacuum.

Try the timing test and see what happens. The carb tips I gave you will
probably not affect your misfire condition, but were more for when you
get to the point of tuning the carb.

Chris

Re: CJ5 misfires at high RPM/hard acceleration
 

matthew.nye@gmail.com wrote:
> Thanks for everyone's replies. Here's what I've done from your
> suggestions:
>
> - Having the gas cap off made no difference. I actually don't have
> any of the emissions stuff on it, so there's no canister, just the gas
> tank to the pump.
> - Having the coil's + lead hooked directly to the battery made no
> difference, I tried switching the leads on the ballast resistor too
> first to see if I had it hooked up wrong. I may be wrong, but I think
> the ballast resistor leads can go either way?
> - I tried what Roy suggested with interesting results. When I
> advanced the engine to 10 or 15 degrees, it would run noticeably
> better, but not perfect. I could actually get the secondaries to open
> up on the carb before it crapped out, which I haven't been able to do
> since the fuel pump change. I was grabbing at straws when I replaced
> the vacuum advance. I could suck air right through it with my mouth
> so I knew it was bad, that & having it plugged in at idle made no
> difference in timing advance. When I have the new one plugged in, it
> automatically advances it to about 10 BTDC at idle. I didn't see any
> adjustments on it, but maybe that's what is wrong? I couldn't get the
> engine started with it advanced so far when testing, I could only test
> it out by having it started first & then advancing it. The idle was
> terrible with a lot of misfiring at that point, if that means
> anything.
> - I've had a few people also tell me it's over carbureted, but that's
> what has always been on it (my dad owned it for like about 15 years
> before me) & it seemed to have ran fine for the longest time. That is
> an interesting theory though that the old pump could have just been so
> tired that it didn't put enough pressure through to put it at it's
> full potential. I was considering a 500cfm 2-bbl holley if I had to
> purchase one, but it sounds like that might be too much as well? To
> clarify, the pump just started leaking when it went out, it didn't
> seize up or anything, in fact I didn't know it was going bad until I
> started getting sprayed with gas (there's no fenders, windshield,
> etc). I don't know if I cleaned the jets out good enough when I
> rebuilt the carb, so it's a possibility that part of the diaphragm got
> stuck in it. it does seem to flow OK though when I look at the spray
> coming out of the jets.
> - The vacuum is very steady at idle, maybe 1hg of movement at most
> from side to side. I have not performed a compression check, what
> would that tell me if it were low? I don't have a compression tester
> available so I'm not going to be able to do that one right away.
> - The plugs are bosch platinums with a heat rating of 9. I'm not sure
> what that equates to heat-wise though, is that a standard across all
> plugs?\
>
> Any suggestions on the distributor? I checked the springs & weights
> of the centrifugal advance & they seem to be nice & responsive, but
> then again, I'm not sure what they're supposed to look like. Should I
> try replacing the entire distributor before I go crazy & take the
> entire front of my engine apart for the timing chain or start messing
> with the carb? Is there any way to test whether or not the timing
> chain has slipped a tooth without actually looking at it?
>
> Thanks again guys,
>
> -Matt
>

I really think your problem is the timing, and could be caused by a few
different things. Engines with aftermarket headers, cams, etc. usually
like a little more timing. As long as you aren't experiencing ping and
the starter doesn't kick back when the engine is hot, you're not hurting
anything.

An engine with not enough timing advance will do exactly what yours is
doing. It will also seem like it is running rich because the fuel
mixture is exiting the cylinder before is has had time to completely
burn. the popping noise you're hearing is actually from the exhaust
valve opening while the mixture is still burning.

If you have access to a timing light with the dial adjustable advance on
it, check the timing at idle with the vacuum advance disconnected, then
rev the engine to about 3000-3500 RPM and check it there. It should have
advance to about 30-34 degrees. If it is much less than this, then your
mechanical advance is not functioning properly. My guess is that this is
what is happening. IF you are not getting 30-34 degrees, you can test to
see if the additional timing fixes the problem by advancing the timing
to get about 30 degrees at 3000 RPM. One word of caution when doing
this: you are compensating for a malfunctioning mechanical advance and
will have a lot of timing at idle, so when you do your acceleration test
like this, go light on the gas pedal to prevent a ton of pinging.

There is a slight possibility that the outer ring on your balancer has
slipped on the rubber ring between the outer ring and the hub. This is
one thing that would explain the timing issue. An

One thing that comes to mind that I have seen people forget during a
Holley rebuild is the little needle check that goes in the fuel passage
underneath the accelerator pump nozzle. If you leave that out, the
engine vacuum at higher RPM can cause fuel to flow out the nozzle. It
also causes other problems, which you don't seem to be experiencing, so
it is probably in there.

A 600 may not be ideal for a 304, but it can be made to run just fine.
There are literally thousands of 302 Fords, 305 Chevys and 318 Mopars
running Holey 600 carbs on them. I am assuming you probably have the
Holley model 1850 (probably with a dash number after it) The number will
be on the front of the choke horn. The problem with these carbs is that
they are set up to run on a wide range of engines, and are very rarely
perfect out of the box for your particular application. they are
normally tuned a bit rich as far as jetting goes, but nothing extreme.

If the engine runs the best with the mixture screws turned all the way
in, or close to it, then obviously it is running too rich.

Hook your vacuum gage up to manifold vacuum, which is any point below
the throttle plates. Going by your vacuum reading, you're in the right
spot now. Set your idle speed to the proper RPM and then remove the
sight plug for the float level and adjust it so that the fuel level is
just below the hole. By rocking the vehicle slightly, you should see the
gas flow out of the sight hole just a little bit.

Now using your vacuum gage, set the idle mixture screws to achieve the
highest vacuum reading at idle. If the idle speed rises when you make
adjustments, then reset the RPM to the correct level. A well tuned
engine with a stock camshaft should have about 20" of vacuum, but an
engine with a lot of miles will read less. Worn rings and valve seats
will reduce vacuum.

Try the timing test and see what happens. The carb tips I gave you will
probably not affect your misfire condition, but were more for when you
get to the point of tuning the carb.

Chris

Re: CJ5 misfires at high RPM/hard acceleration
 

matthew.nye@gmail.com wrote:
> Thanks for everyone's replies. Here's what I've done from your
> suggestions:
>
> - Having the gas cap off made no difference. I actually don't have
> any of the emissions stuff on it, so there's no canister, just the gas
> tank to the pump.
> - Having the coil's + lead hooked directly to the battery made no
> difference, I tried switching the leads on the ballast resistor too
> first to see if I had it hooked up wrong. I may be wrong, but I think
> the ballast resistor leads can go either way?
> - I tried what Roy suggested with interesting results. When I
> advanced the engine to 10 or 15 degrees, it would run noticeably
> better, but not perfect. I could actually get the secondaries to open
> up on the carb before it crapped out, which I haven't been able to do
> since the fuel pump change. I was grabbing at straws when I replaced
> the vacuum advance. I could suck air right through it with my mouth
> so I knew it was bad, that & having it plugged in at idle made no
> difference in timing advance. When I have the new one plugged in, it
> automatically advances it to about 10 BTDC at idle. I didn't see any
> adjustments on it, but maybe that's what is wrong? I couldn't get the
> engine started with it advanced so far when testing, I could only test
> it out by having it started first & then advancing it. The idle was
> terrible with a lot of misfiring at that point, if that means
> anything.
> - I've had a few people also tell me it's over carbureted, but that's
> what has always been on it (my dad owned it for like about 15 years
> before me) & it seemed to have ran fine for the longest time. That is
> an interesting theory though that the old pump could have just been so
> tired that it didn't put enough pressure through to put it at it's
> full potential. I was considering a 500cfm 2-bbl holley if I had to
> purchase one, but it sounds like that might be too much as well? To
> clarify, the pump just started leaking when it went out, it didn't
> seize up or anything, in fact I didn't know it was going bad until I
> started getting sprayed with gas (there's no fenders, windshield,
> etc). I don't know if I cleaned the jets out good enough when I
> rebuilt the carb, so it's a possibility that part of the diaphragm got
> stuck in it. it does seem to flow OK though when I look at the spray
> coming out of the jets.
> - The vacuum is very steady at idle, maybe 1hg of movement at most
> from side to side. I have not performed a compression check, what
> would that tell me if it were low? I don't have a compression tester
> available so I'm not going to be able to do that one right away.
> - The plugs are bosch platinums with a heat rating of 9. I'm not sure
> what that equates to heat-wise though, is that a standard across all
> plugs?\
>
> Any suggestions on the distributor? I checked the springs & weights
> of the centrifugal advance & they seem to be nice & responsive, but
> then again, I'm not sure what they're supposed to look like. Should I
> try replacing the entire distributor before I go crazy & take the
> entire front of my engine apart for the timing chain or start messing
> with the carb? Is there any way to test whether or not the timing
> chain has slipped a tooth without actually looking at it?
>
> Thanks again guys,
>
> -Matt
>

I really think your problem is the timing, and could be caused by a few
different things. Engines with aftermarket headers, cams, etc. usually
like a little more timing. As long as you aren't experiencing ping and
the starter doesn't kick back when the engine is hot, you're not hurting
anything.

An engine with not enough timing advance will do exactly what yours is
doing. It will also seem like it is running rich because the fuel
mixture is exiting the cylinder before is has had time to completely
burn. the popping noise you're hearing is actually from the exhaust
valve opening while the mixture is still burning.

If you have access to a timing light with the dial adjustable advance on
it, check the timing at idle with the vacuum advance disconnected, then
rev the engine to about 3000-3500 RPM and check it there. It should have
advance to about 30-34 degrees. If it is much less than this, then your
mechanical advance is not functioning properly. My guess is that this is
what is happening. IF you are not getting 30-34 degrees, you can test to
see if the additional timing fixes the problem by advancing the timing
to get about 30 degrees at 3000 RPM. One word of caution when doing
this: you are compensating for a malfunctioning mechanical advance and
will have a lot of timing at idle, so when you do your acceleration test
like this, go light on the gas pedal to prevent a ton of pinging.

There is a slight possibility that the outer ring on your balancer has
slipped on the rubber ring between the outer ring and the hub. This is
one thing that would explain the timing issue. An

One thing that comes to mind that I have seen people forget during a
Holley rebuild is the little needle check that goes in the fuel passage
underneath the accelerator pump nozzle. If you leave that out, the
engine vacuum at higher RPM can cause fuel to flow out the nozzle. It
also causes other problems, which you don't seem to be experiencing, so
it is probably in there.

A 600 may not be ideal for a 304, but it can be made to run just fine.
There are literally thousands of 302 Fords, 305 Chevys and 318 Mopars
running Holey 600 carbs on them. I am assuming you probably have the
Holley model 1850 (probably with a dash number after it) The number will
be on the front of the choke horn. The problem with these carbs is that
they are set up to run on a wide range of engines, and are very rarely
perfect out of the box for your particular application. they are
normally tuned a bit rich as far as jetting goes, but nothing extreme.

If the engine runs the best with the mixture screws turned all the way
in, or close to it, then obviously it is running too rich.

Hook your vacuum gage up to manifold vacuum, which is any point below
the throttle plates. Going by your vacuum reading, you're in the right
spot now. Set your idle speed to the proper RPM and then remove the
sight plug for the float level and adjust it so that the fuel level is
just below the hole. By rocking the vehicle slightly, you should see the
gas flow out of the sight hole just a little bit.

Now using your vacuum gage, set the idle mixture screws to achieve the
highest vacuum reading at idle. If the idle speed rises when you make
adjustments, then reset the RPM to the correct level. A well tuned
engine with a stock camshaft should have about 20" of vacuum, but an
engine with a lot of miles will read less. Worn rings and valve seats
will reduce vacuum.

Try the timing test and see what happens. The carb tips I gave you will
probably not affect your misfire condition, but were more for when you
get to the point of tuning the carb.

Chris

Re: CJ5 misfires at high RPM/hard acceleration
 

matthew.nye@gmail.com wrote:
> Thanks for everyone's replies. Here's what I've done from your
> suggestions:

> The plugs are bosch platinums with a heat rating of 9
<snipped>

'All' the old Jeep engines 'I' personally have seen (and read about
'many') will 'NOT' run on Bosch platinum plugs.

They foul up almost immediately.

I would change those before doing anything else and put proper Champion
truck plugs back into it.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's - Gone to the rust pile...
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

Re: CJ5 misfires at high RPM/hard acceleration
 

matthew.nye@gmail.com wrote:
> Thanks for everyone's replies. Here's what I've done from your
> suggestions:

> The plugs are bosch platinums with a heat rating of 9
<snipped>

'All' the old Jeep engines 'I' personally have seen (and read about
'many') will 'NOT' run on Bosch platinum plugs.

They foul up almost immediately.

I would change those before doing anything else and put proper Champion
truck plugs back into it.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's - Gone to the rust pile...
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

Re: CJ5 misfires at high RPM/hard acceleration
 

matthew.nye@gmail.com wrote:
> Thanks for everyone's replies. Here's what I've done from your
> suggestions:

> The plugs are bosch platinums with a heat rating of 9
<snipped>

'All' the old Jeep engines 'I' personally have seen (and read about
'many') will 'NOT' run on Bosch platinum plugs.

They foul up almost immediately.

I would change those before doing anything else and put proper Champion
truck plugs back into it.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's - Gone to the rust pile...
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)