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dusterbd13
11-25-2007, 04:51 PM
ok, i will preface this by saying that i am not much of a holley guy. ive been dyed in the wool carter since my first AVS. the reason being, that Holleys never seemed to run right for me. or maybe i could never get them to run right may be a better way of saying that.
with all that said, i found myself the proud owner of a dual metering block, double pumper holley. friend of mines dad gave it to me, so the price was right. according to him, its a 750 CFM unit that has been modified. i cannot confirm the CFM rating due to the choke horn being milled off. any way to ID it?
the car runs pretty good. not too bad thrttle response, stable idle.
now, for the problems:
1. at idle, thecar runs pig rich. seems to run best with the front metering block idle screws turned the whole way in. no screws on the back, and not sure if there should be.
2. after running the car for a little while and stopping it, the car WILL NOT restart. acts like its flooded.
3. Pig rich during cruise, horrible fuel economy.
4. rear accelerator pump not working.

I have no idea what is in the carb or what has been modified. he pulled it off his Camaro, put it on the bench, and then gave it to me. nothing has been changes except for the idle speed setting and idle mixture scres from the camaro, and he stated that he had the number 1 and 2 problems with it.

so please, give me suggestions, and maybe make me able to tune holleys while im at it.

thanks
Michael

MrQuick
11-25-2007, 06:57 PM
First i'd look for a stuck open needle seat but you say it runs abit. Then i'd go to the power valve. Rich run with a hard restart is a tell tale sign. Your gonna need to pull that puppy off and go through it. Learn how to work it or pay a tuner.

Compared to a Carter its very simple. I cut my teeth on Rochester's my self.

dusterbd13
11-25-2007, 07:35 PM
it runs really good, actually. ive gotten about 200 miles on the car with this carb so far.
ive noticed no overflow from the vent tubes, which i was always told on a holley is the way to see if the needle and seats are stuck open. is that true?

and is there a way to test a power valve, or just replace it?

lastly, on power valve selection. iknow that you can alter the vacuum reading based on idle mixture, so with my issues, do i choose the power valve based on current manifold vacuum, or replace it twice?

i kinda look forward to learning holleys a bit better, actually. i need to branch out a bit. ive rebuilt a bunch of them, just never got proficient at tuning them.

Michael

Shaker455
11-27-2007, 08:31 AM
Michael,
I posted this a few weeks ago:

There's a raised casting number on the primary driverside upper left corner of the mainbody.

Example: P-32 is an 850CFM mainbody

Also post the numbers you see stamped on the throttleblades flipping the carb upside down.

Example: 180 is a 1-3/4" base...= 850CFM

Sound like that carb given to you needs to be rebuilt

If you want to do it yourself here's a few books to grab:

Holley Carburetors, manifolds & fuel injection by Mike Urich & Bill Fisher
ISBN# 1-55788-052-2

Super Tuning and modifing Holley Carburetors
Dave Emanuel
ISBN# 1-884089-28-3

MrQuick
11-28-2007, 11:00 PM
I agree those books are worth the time.

Best way to learn is to have a teacher but tearing into them is good too.

They do sell a power valve tester but if you disassemble it after it has been run, fuel on both sides of the power valve is an indication of failure. If its been dry, look at the body side of the diaphram and it looks wrinkled and stained then it is no good. My mentor use to suck on the valve then seal it off with his tongue. If it held vacuum then it was good. Not a test I would recommend.

While its still running you might want to get a vacuum reading at the manifold with it in gear loaded to help with tuning your power valve choice. Vacuum readings would depend mainly on engine rpm not necassarly mixture percentages, could be wrong.I know it was a mixture set...turn screws till you get the best vac reading. Rich idle mix = low idle and visa versa that makes sence however if you set the idle speed to a given rpm point then idle mixture would not really be a factor.

As far as PV choice. Some say 2in below the reading, some say 1in. I've been good with 2in below. You don't want PV enrichment at idle.