Baseline Jetting.

Hey guys, got a question.

I have been trying to narrow down a loss of power (I think). The car has a Demonsizzler Thermoquad carb now that is way, way off. It doesn't seem to matter what I do, the a/f for most the run is in the 9's and low 10's. After a couple passes the plugs are black. The exhaust manifolds are changing all sorts of colors due to what I believe is raw fuel burning in them. I have smaller than factory 340 jetting in it, and have tried messing with the air door. I have tried different fuel pressures with no change.

I have a holley hp series 770 or 780 I believe that I am going to throw on and make a couple passes with. I would like to have it semi close with maybe a lean side jetting to start.
The motor is 402 cu in, factory manifolds, and intake, solid roller.
The motor went 11.57 @ 117.9 in a 3670 AAR with a six-pack.
Now is in a 71 Duster, 3166 w/ factory intake hogged out and has gone 11.95 @ 113

What jetting is good to start?

Thanks

Anybody have a good starting point? It has 70, 75's in it right now.

Look here for the list number and start where holley put in it as a baseline

http://www.holley.com/data/TechService/Technical/Carb%20Numerical%20Listing.pdf

Which carb you talkin.... you can look it up on the
Holley website... just get the numbers off the carb

Im running 78's and 85's in my 750 Demon on a mild 408 if that helps.It came with 76's and 83's.My plugs look the same either way but i picked up almost a mph in the 1/8 with the change .Those jett sizes dont seem that big to me .Are you sure you dont have another problem ,leaking needle and seat ,floats too high ,etc ...

The thermoquad is the one running real rich. I have had it apart a few times and I can't really find anything "wrong" with it. All of the adjustments are set to factory settings as far as I can tell, I have tried contacting the builder to no avail.

Right now I am trying to figure out why the car is running slow. The motor is down over 100hp, and I am making one change at a time and this time it is the carb. Hopefully it comes around.

So I should stick to what jets holley put in from the factory?

Have you done a leak down yet

The motor was taken out of the aar.
Ryanj freshened it up, and did the 71 intake. Also the p/s exhaust manifold was replaced for the correct 71. Both of the new parts were hogged out pretty good.
I have not done a leakdown, compression is @ 245psi and pretty even across the board. The whole car has around 12passes so far. It's consistantly slow.

Brian:

What you might want to do is put the six pack on it and try to establish a baseline "starting point". Then work backwards from there. Did they change the cam when the motor was gone through??

Give me a call at the shop. I will try to help you if I can. 973-267-4364.

MB

Quote:

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Brian:

What you might want to do is put the six pack on it and try to establish a baseline "starting point". Then work backwards from there. Did they change the cam when the motor was gone through??

Give me a call at the shop. I will try to help you if I can. 973-267-4364.

MB

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Mike ,
I am going to set the holley up so I can throw it on wednesday night. The six pack will go back on if it doesn't pick up here pretty soon..

The cam is the same, though I am beginning to wonder if it was installed at the same spot. The cranking compression is 245, when the motor was in the aar it was 215-220.

I think I might have found the smoking gun last night. It appears one of my mopar performance plug wires were not made the same as the rest, the rubber clips on the cap, but the metal terminal is about 1/2-3/4" from actually making contact with the cap terminal. The distributor cap terminal on the one plug is green, and has serious corrosion, you can see where the spark has been burning through the cap.... Number 2 spark plug looks brand new, wet, but not black like the rest of them.
I put a new cap, rotor, and set of firecores on it. Gonna leave the thermoquad, but bring the holley to try if it is still pig rich.