498 Trick Flow Head Carb Tuning

1972 Satellite
Weight was 3200 with driver old combo (440 iron headed, filled with hard block. So little lighter now
New engine B block eagle 4.15 stroker kit 11.1 compression
Out of the box trick flows 240 for roller cam
Harland Sharp rocker arms 1.7 (thanks AndyF)
Comp Roller Cam (thanks fast68plymouth) around 268 dur and 690 lift.
High volume pump with jeg cheap pan and milodon pickup (thats a whole different story)
Trick flow intake out of the box.
950 holley unknown anything about it
MP distributor
super comp headers, open exhaust
8" ptc converter
4.1 gear
ladder bar car
transbrake
4 passes on new gear, converter and engine
No timing changes and little rich by looking at plugs
Passes made yesterday at Byron, il
Best pass was 10.214 at 131.04

Jets
82 front 3.5PV POWER VALVE IS BAD!!!!!!!!!!!
85 rear plugged


Copying some info fromm the 600 hp thread

Here is metering block info. This was never driving on street, was not impressive at tip in around the pit and short drives. Will get exhaust welded up soon.

Knowing the power valve is bad I have a new 2.5 sitting in garage.

What jet change should I make?
Can pick up different power valve tomorrow after work. Idle before vacuum guage was around 5-7 but jumpy and real senstive to idle screws, idle best around 3/4 turn out. I have no partial throttle info.

outer air bleeds are .069
inner air bleeds are .030

Plugs after run and driving back to trailer.

The .088" on the e holes is wrong. Look deeper inside, you'll see a smaller drill hole in each one.

I agree. they should be more like .026"

Fix what is wrong first before changing anything else
Changing one thing at a time will get you far better results than two or three things at once
What plug numbers are you using?
How much total timing are you running now?

Sorry for typo on that, fixed it to be the .028
Good Catch!!!

I want to fix the power valve but think I should change the jetting to match. Think it was bad since i owned it.

I wouldn't use a super soft power valve like 2.5 or 3.5 in a street car. If it was me I'd put a 6 or 6.5 in it and see how it works. Idle vacuum doesn't really matter, the power valve doesn't work at idle it works when the engine gets loaded at higher RPM. Put a vacuum gauge in the car and see what it says when you are cruising down the freeway. It will probably be 13 or 15 or something in that range. If that is the case then a 6 or 6.5 should be fine.

82 jets up front are probably too large but hard to tell without some data. See if you can find a model number on the carb and then jet it like stock. You'll probably want something like a 75 jet + power valve up front and maybe 85 with no power valve out back. Hard to say without knowing more about the carb though.

Carb is 80496 will dig up the factory jetting.

Edit to show holley stock jetting

I will pick up a 6.5 power valve today, change the front jets to 79 and leave the rear at 85

Plugs are
Autolite # 3924

Timing at 34 degrees total with mechanical kicked in. Can not remember where its at initial.

factory 79/79 jetting ?
does it have secondary power valve?

Assuming factory it does. My carb does not have a secondary power valve

Do yourself a favor....... Buy an A/F ratio gauge.

A/f Gauge is on the list, need some exhaust also. Going broke with this car

Changed front jet to 79, replaced power valve with a 5.5, same DA as last week differnt track. Cordova Il
Ran 10.1 at 131-132

Will post a video later today

Sounds like you are making pretty good power. Should be a fun ride at 132 mph. Keep an eye on the plugs if you don't have an AF gauge.

Was checking the plugs and could lean down more, I was hoping the weather would cool off and hit that 9.99. Will see what next weekend does.

What is your complete tune now? Do you have an 80496 with pressed-in idle & main air bleeds, or 80496-1 with screw-in bleeds?

Pressed in idle & air bleeds
Jets
79 front 5.5PV
85 rear plugged

Timing still at 34

Check timing with a different light...looks like mark is very close to the thread...you could be of buy a couple degrees.or even more ...

Will double check timing tonight

The original 80496-1 model w/ the replaceable bleeds came w/ the following:
IAB - .072
MAB - .032
Pri & Sec jets: 78 (6.5 power valves both sides)
PVCR - .054
IFR - ???; probably the same as your .036

My SUGGESTIONS...
- modify the body for replaceable air bleeds and start with .072 IAB and .030 MAB (I'd expect the MAB could go either way from here, but the IAB is probably pretty close)
- start with a 78 pri & 86 sec
- relocate the IFRs to the lower openings using 6-32 brass set screws and start with .035
- plug the middle of the 3 emulsion holes on each side (leave top & bottom holes active)
- .035 accel pump nozzles

I believe that will give you a more workable baseline from which to tune w/ a wideband 02 setup.

FWIW, I've seen build sheets for a number of 80496-based carbs from a couple of "well known" custom carb companies and they generally run 76/86 w/ a .059 PVCR or 78/86 w/ a .054

Good info thanks!!

Brad, I'm pretty sure both my 80496-1's came with 74 IAB.

I can only pass on what the one I bought in the late '90s came with, and know that Holley changes things almost on a whim at times.