c

Bill,

They probably didn't get the engine to its peak power RPM. Remember, the 4.0
head makes peak power at about 4000 RPM. The head doesn't know what engine
it is sitting on top of. If the engines are approximately the same size, the
bore and stroke don't have much effect on the peak power RPM. A long stroke,
small bore engine should make more low RPM torque than a short stroke, big
bore engine. Also, porting a head will almost always move the power band up.

To explain this to some degree, a cylinder head port by design has a "sweet
spot" where it best fills and empties the cylinder. This is basically where
your power peak will be. This also works in conjustion with the intake,
camshaft and exhaust. This is why it is important to match all of the
components so that they all, by design, produce their peak power at about
the same RPM. In your case, the head is probably helping a little in the
lower RPM and will show more improvement as the RPM gets closer to 4000.

As far as the dyno test, if they used a chassis dyno and read the power at
the rear wheels, then it is rear wheel horsepower. This number is generally
about 20-30% lower than the flywheel rating due to friction losses in the
trans, transfer case, and axle. An automatic trans will usually show more
power loss than a standard because of the toque convertor and more friction
loss internally.

Did they give you a copy of the dyno sheet? If so, look at the number in the
BSFC (Brake specific fuel comsumption) column. This will give a good idea as
to where the fuel mixture is. The number should be around 0.5 or a bit
higher for the correct fuel mixture. This basically means that it is using
..5 pounds of fuel per horsepower per hour. If the number is too high, it
shows an inefficient engine. This would have also been a good time for you
to play with your timing to optimize it. Normally, the timing that shows the
best power on the dyno will be 2-4 degrees higher than what you should run
because of temperature, barometric pressure, and load changes in real world
driving.

Chris

"William Oliveri" <wuji@bigvalley.net> wrote in message
news:2hhi42Fco2thU1@uni-berlin.de...
> The 4.2/4.0 mod should add about 40 horse power due to the porting on the
> 4.0L head.
>
> I'm not sure how the dyno test works but I think it's at the wheels.
>
> Looks like they cut it off at about 3350 rpm.
>
> Bill
>
>
>
> "Tim Vice" <timothy.vice@washburn.edu> wrote in message
> news:36Msc.67492$iy5.64474@okepread05...
> > Is the horsepower that you are getting at the wheels, or at the crank?
> >
> > What is the difference in the heads to create more horsepower, or have
you
> > done some other things?
> >
> > At what RPM was the highest horsepower created?
> >
> > Just some questions because I'm looking into stroking my 4.0
> >
> > Tim
> >
> >
> > "William Oliveri" <wuji@bigvalley.net> wrote in message
> > news:2hhg59Fd4rv0U1@uni-berlin.de...
> > > 4.2 block / 4.0 Head.
> > >
> > > Results: 124.9 Horsepower. I should have about 160, yes?
> > >
> > > Air/Fuel ratio came back a tad lean if anything.
> > >
> > > Engine has about 60 miles on it.
> > >
> > > Mechanic told me there's nothing wrong with the injectors.
> > >
> > > Bill
> > >
> > >
> >
> >
>
>

Erik Litchy

RocknTJ wrote:
> I was told there is about 30% loss on 4 wheel drive vehicles. The guy that
> did my Cobra said, he had seen a 60% loss with some Audi all wheel drives.
> Auto or manual makes a difference too.
>
>

60% ? was the transmission on the audi glowing white hot?

Erik Litchy

RocknTJ wrote:
> I was told there is about 30% loss on 4 wheel drive vehicles. The guy that
> did my Cobra said, he had seen a 60% loss with some Audi all wheel drives.
> Auto or manual makes a difference too.
>
>

60% ? was the transmission on the audi glowing white hot?

Erik Litchy

RocknTJ wrote:
> I was told there is about 30% loss on 4 wheel drive vehicles. The guy that
> did my Cobra said, he had seen a 60% loss with some Audi all wheel drives.
> Auto or manual makes a difference too.
>
>

60% ? was the transmission on the audi glowing white hot?

Erik Litchy

RocknTJ wrote:
> I was told there is about 30% loss on 4 wheel drive vehicles. The guy that
> did my Cobra said, he had seen a 60% loss with some Audi all wheel drives.
> Auto or manual makes a difference too.
>
>

60% ? was the transmission on the audi glowing white hot?

RocknTJ

Here you go I knew I could find it:
http://jeepsunlimited.com/forums/sho...hreadid=511089
it looks like at 60 miles your are almost exactly what a stock TJ is. It
will come around, I am sure.

Good luck.

--James

"William Oliveri" <wuji@bigvalley.net> wrote in message
news:2hhjsoFd3q0aU1@uni-berlin.de...
> I just talked to the engine rebuilder who told me about the same thing you
> said.
>
> He said a true dyno would be an engine dyno, not the rear wheel dyno.
> Especially in my case since I have a drive shaft problem from the lift
kit.
> Also, break it in at least a couple of thousand miles before making an
> evaluation.
>
> The A/F ratio, they said they couldn't get a print out on their machine so
> they give it back verbally. They said a tad lean side if anything.
>
> Bill
>
>
> "RocknTJ" <jetowle@***.net> wrote in message
> news:oEMsc.20983$7y5.12301@fed1read03...
> >
> > I was told there is about 30% loss on 4 wheel drive vehicles. The guy
that
> > did my Cobra said, he had seen a 60% loss with some Audi all wheel
drives.
> > Auto or manual makes a difference too.
> >
> > In addition, 60 miles is not enough to let everything seat properly. I
had
> > my Cobra tested at 2222 miles and was told that is still not enough
miles
> > for proper seating.
> >
> > What was the A/F ratio in numbers? I would think it needs to stay around
> 12.
> >
> > --James
> >
> > "William Oliveri" <wuji@bigvalley.net> wrote in message
> > news:2hhg59Fd4rv0U1@uni-berlin.de...
> > > 4.2 block / 4.0 Head.
> > >
> > > Results: 124.9 Horsepower. I should have about 160, yes?
> > >
> > > Air/Fuel ratio came back a tad lean if anything.
> > >
> > > Engine has about 60 miles on it.
> > >
> > > Mechanic told me there's nothing wrong with the injectors.
> > >
> > > Bill
> > >
> > >
> >
> >
>
>

RocknTJ

Here you go I knew I could find it:
http://jeepsunlimited.com/forums/sho...hreadid=511089
it looks like at 60 miles your are almost exactly what a stock TJ is. It
will come around, I am sure.

Good luck.

--James

"William Oliveri" <wuji@bigvalley.net> wrote in message
news:2hhjsoFd3q0aU1@uni-berlin.de...
> I just talked to the engine rebuilder who told me about the same thing you
> said.
>
> He said a true dyno would be an engine dyno, not the rear wheel dyno.
> Especially in my case since I have a drive shaft problem from the lift
kit.
> Also, break it in at least a couple of thousand miles before making an
> evaluation.
>
> The A/F ratio, they said they couldn't get a print out on their machine so
> they give it back verbally. They said a tad lean side if anything.
>
> Bill
>
>
> "RocknTJ" <jetowle@***.net> wrote in message
> news:oEMsc.20983$7y5.12301@fed1read03...
> >
> > I was told there is about 30% loss on 4 wheel drive vehicles. The guy
that
> > did my Cobra said, he had seen a 60% loss with some Audi all wheel
drives.
> > Auto or manual makes a difference too.
> >
> > In addition, 60 miles is not enough to let everything seat properly. I
had
> > my Cobra tested at 2222 miles and was told that is still not enough
miles
> > for proper seating.
> >
> > What was the A/F ratio in numbers? I would think it needs to stay around
> 12.
> >
> > --James
> >
> > "William Oliveri" <wuji@bigvalley.net> wrote in message
> > news:2hhg59Fd4rv0U1@uni-berlin.de...
> > > 4.2 block / 4.0 Head.
> > >
> > > Results: 124.9 Horsepower. I should have about 160, yes?
> > >
> > > Air/Fuel ratio came back a tad lean if anything.
> > >
> > > Engine has about 60 miles on it.
> > >
> > > Mechanic told me there's nothing wrong with the injectors.
> > >
> > > Bill
> > >
> > >
> >
> >
>
>

RocknTJ

Here you go I knew I could find it:
http://jeepsunlimited.com/forums/sho...hreadid=511089
it looks like at 60 miles your are almost exactly what a stock TJ is. It
will come around, I am sure.

Good luck.

--James

"William Oliveri" <wuji@bigvalley.net> wrote in message
news:2hhjsoFd3q0aU1@uni-berlin.de...
> I just talked to the engine rebuilder who told me about the same thing you
> said.
>
> He said a true dyno would be an engine dyno, not the rear wheel dyno.
> Especially in my case since I have a drive shaft problem from the lift
kit.
> Also, break it in at least a couple of thousand miles before making an
> evaluation.
>
> The A/F ratio, they said they couldn't get a print out on their machine so
> they give it back verbally. They said a tad lean side if anything.
>
> Bill
>
>
> "RocknTJ" <jetowle@***.net> wrote in message
> news:oEMsc.20983$7y5.12301@fed1read03...
> >
> > I was told there is about 30% loss on 4 wheel drive vehicles. The guy
that
> > did my Cobra said, he had seen a 60% loss with some Audi all wheel
drives.
> > Auto or manual makes a difference too.
> >
> > In addition, 60 miles is not enough to let everything seat properly. I
had
> > my Cobra tested at 2222 miles and was told that is still not enough
miles
> > for proper seating.
> >
> > What was the A/F ratio in numbers? I would think it needs to stay around
> 12.
> >
> > --James
> >
> > "William Oliveri" <wuji@bigvalley.net> wrote in message
> > news:2hhg59Fd4rv0U1@uni-berlin.de...
> > > 4.2 block / 4.0 Head.
> > >
> > > Results: 124.9 Horsepower. I should have about 160, yes?
> > >
> > > Air/Fuel ratio came back a tad lean if anything.
> > >
> > > Engine has about 60 miles on it.
> > >
> > > Mechanic told me there's nothing wrong with the injectors.
> > >
> > > Bill
> > >
> > >
> >
> >
>
>

RocknTJ

Here you go I knew I could find it:
http://jeepsunlimited.com/forums/sho...hreadid=511089
it looks like at 60 miles your are almost exactly what a stock TJ is. It
will come around, I am sure.

Good luck.

--James

"William Oliveri" <wuji@bigvalley.net> wrote in message
news:2hhjsoFd3q0aU1@uni-berlin.de...
> I just talked to the engine rebuilder who told me about the same thing you
> said.
>
> He said a true dyno would be an engine dyno, not the rear wheel dyno.
> Especially in my case since I have a drive shaft problem from the lift
kit.
> Also, break it in at least a couple of thousand miles before making an
> evaluation.
>
> The A/F ratio, they said they couldn't get a print out on their machine so
> they give it back verbally. They said a tad lean side if anything.
>
> Bill
>
>
> "RocknTJ" <jetowle@***.net> wrote in message
> news:oEMsc.20983$7y5.12301@fed1read03...
> >
> > I was told there is about 30% loss on 4 wheel drive vehicles. The guy
that
> > did my Cobra said, he had seen a 60% loss with some Audi all wheel
drives.
> > Auto or manual makes a difference too.
> >
> > In addition, 60 miles is not enough to let everything seat properly. I
had
> > my Cobra tested at 2222 miles and was told that is still not enough
miles
> > for proper seating.
> >
> > What was the A/F ratio in numbers? I would think it needs to stay around
> 12.
> >
> > --James
> >
> > "William Oliveri" <wuji@bigvalley.net> wrote in message
> > news:2hhg59Fd4rv0U1@uni-berlin.de...
> > > 4.2 block / 4.0 Head.
> > >
> > > Results: 124.9 Horsepower. I should have about 160, yes?
> > >
> > > Air/Fuel ratio came back a tad lean if anything.
> > >
> > > Engine has about 60 miles on it.
> > >
> > > Mechanic told me there's nothing wrong with the injectors.
> > >
> > > Bill
> > >
> > >
> >
> >
>
>

L.W.(=?iso-8859-1?Q?=DFill?=) Hughes III

129 HP Stock and with the supercharger:
http://jeepsunlimited.com/forums/sho...hreadid=511089
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/

RocknTJ wrote:
>
> Here you go I knew I could find it:
> http://jeepsunlimited.com/forums/sho...hreadid=511089
> it looks like at 60 miles your are almost exactly what a stock TJ is. It
> will come around, I am sure.
>
> Good luck.
>
> --James