TXSTICK

I have a 383 stroker with a Holley Street Avenger 770 cfm on it.
I do not know what jets are in the carb yet. I have not checked the timing but a comp cam tech told me the cam (I believe it is a comp cam XR282HR) likes about 12 deg adv. The car is very rich at idle and I have been told by someone who followed me it is very rich driving down the road.
(burns the eyes)

The car was orig in California at near sea level and is now at around 2800 ft.

What would be a good starting point for the jets front and rear?
I will check the timing and set the carb idle mixture screws this week with a vacuum gauge. But I an not sure if that is all it needs.

thanks

chuck

Dicecal

http://www.lbfun.com/warehouse/tech_...rb%20Paper.pdf

vt65

Chuck, I have the same problem but i'm running a 383 with a new 750 Holley, runs bad rich, always have to be at the back of the line, no-one wants to follow us, hope you get some good ideas here, getting tired of 7 mpg

TXSTICK

Thanks for the link.

chuck

mikem350

If its that rich..you probably have a PROBLEM w the CARB, not timing

Check obvious...is choke flap open???
Is pcv hooked up..most carbs are set up so they expect to see more air coming in via the pcv

also a leaking power valve will cause richness

use the same jets that shipped with the carb originally..Holley has about 100 years of experience here...I've used avengers and only had to tweek the idle screws about 1/4 turn each and NEVER had another problem

TXSTICK

Thanks, previous owner sent me an email and said the carb was adjusted during the dyno tune of the engine.

I will check for pcv and other items you said above.

thanks
chuck

65tripleblack

If you are using the stock coil and/or a weak one, you may have that type of problem because you are not getting consistent and complete burn. If you are fouling plugs, as well, there is the proof of the pudding.

TXSTICK

It has the Pertronics II Ignition, and I put in a Pertronics coil (45,000) about 5 months ago.
I have not pulled a plug yet.

claysmoker

If you are close to 3000' above sea level, go down two jet sizes both primary and secondary. I'm at 5K feet and the problem is even worse here. I drilled both the primary blades with a .090" hole and it helps lean the idle as well.

I'm sure these carbs come out of the factory on the rich side anyway, so you may have to go more than the two jet sizes. If you pick up an off idle stumble, you may also have to change the accelerator pump cam. I ended up with a black one.

Check the vacuum at idle. You may have to go to a smaller numerical power valve. I think those carbs come with a 6.5, and mine is much happier with a 4.5 at my altitude.

Good luck!

TXSTICK

Thanks, my friend who is a mechanic, also said it could be due to the higher altitude. It does stumble off idle. I will have to look at what is in the car after I do my last car show next weekend. I won't do another until Jan 2012. I don't need the car down right now.

chuck

Kensmith

Chuck,

The car was tuned in Sacramento, CA. Do not change timing as it is correct. If you are at 3,000 ft elevation it's the carb. Elevation will make a difference. If you were at 6,000 ft it would run like a 6 cylinder. Call Holley Tech and he will tell you what to do to tune the carb. Also, plugs are new like everything else on the motor. Vacuum advance can is also new so it has to be the carb and altitude.

Westlotorn

If it has backfired at all you may have just popped the power valve, it only takes once.
I would look at all 8 spark plugs and read them. If all 8 are black you know it is most likely carb issue and it sounds like it will be on this engine.
If some are clean and others are fouled it gives you a new direction to look.
Good luck.

mechron

hi ken, and hi turbo cat. if he is on here (thanks for the body drop, it was simple) on a holley if it jetted right the altuted it will take of itsef. at 6000 ft. it is all about the presuhure differentual thrugh the vintuiers.

as for the timing, who cares, my pantera is super fun.

Vet65te

Chuck, the 770 Avenger has #72 Primary Jets and #75 Secondary Jets.
For comparison, the next size down Avenger, the 670 comes with #65 Primary Jets and #68 Secondary Jets.
Mike T.

TXSTICK

thanks Ken.
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Westlotorn, It did a couple of times on the way out from Calif.
The coil was going TU. It finally did about 50 miles from my house.
I will check the power valve and my change it like claysmoker has suggested.

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Vet65te I did read last night (holley manual on line) that for every 2000 ft of increased altitude the carb jet size should be dropped 1 size.

Thanks everyone!
Chuck

Vet65te

Txstick - I believe all the Avenger Carbs come with what Holley calls their Power Valve Saver built into the baseplate. Of course, since you're probably going to be in there anyway to change jets, you might as well verify the power valve too.
Mike T.

TXSTICK

Mike,
Correct, I also read that. But I might need to change it to a different one anyway per claysmoker. The Holley manual says to check the vaccum with the engine warm and at idle. Half the vaccum number, and if even go down to the next odd size (8 would use a 3.5, 9 would use a 4.5). If the vaccum is more than 13 then the stock 6.5 will do fine. The wrong one can cause a rich condition.

cv67

Def on the rich side you could run that on a 68 all day no need for more than a 70 jet.

The 1/2 vacuum powervalve thing, no

You should be able to run fine on the stock 6.5

Vet65te

Chuck, I'll be interested to hear what your vacuum reading comes out to at your altitude compared to what it was for the PO at nearly sea level. I expect to have to do even more 'carb-jet-tweaking' when we finally move from our current location in Northern California, which is maybe a hundred feet above sea level, to our lot in Prescott Arizona which is roughly at the 5400 foot elevation.
Mike T.

TXSTICK

Mike, I will post it next week. I am not going to work on the car until after this weekend. (Last show to go to) But I bet I will have to drop the jets down to around 68's on the front and a couple sizes on the rear.


Chuck