Power Valve Issue? - Page 3

pusherfans · #41 (**permalink**) 07-05-2010, 03:01 PM

lean idle it 15-18 on the a/f mixture.

I tried a few more things since and I am sending the carb to AED in the mormning. Details are in another post about idle feed restrictors that seemed to "merge" with this subject. . . .

zrayr · #42 (**permalink**) 07-05-2010, 03:30 PM

like you, I have tried in the past to make a carb designed for one application work in a different envirenment. I fussed & fiddled & swore. But in the end, like you, I just had to admit that race carbs work great when accelerating or full bore, but they hate to cruise at a slight throttle opening.

Z.

pusherfans · #43 (**permalink**) 07-17-2010, 02:20 PM

Just posted this on Club Cobra:

Okay, so AED had a 3 week back log. I decided to fix it myself, one last try. I changed the idle feed restrictors, 3 different times with different sizes, no good. Just leaned out the idle and did nothing for the transition. I also played with the idle air bleeds again, throttle plate positions, etc. Nothing worked, each step made it worse.

I did have a ring out session (to vent frustration) and learned it runs perfect! at WOT. It truly is a drag race carb. So I pulled it out and cleaned it all up, put in new gaskets and put it all back to bone stock as it came from Holley. Now it is on eBay.

I bought a Street HP 4150 - 850 CFM this time, since it has bigger body (smaller plates).

OUT OF THE BOX - PERFECT!!!

I changed the power valve to 3.5 (idle vacuum is 7) and adjusted the accel pumps, floats, idle mixtures and idle speed. That's it! Done! Cruises perfectly, idles perfectly, no rich spots, no lean spots, WOT right on. I don't even feel any less response or performance from the engine.

The Holley part number is 82851.

Now, I'm going to drive it for a couple weeks to confirm, then the O2 sensor can come off and the TP go on. (maybe the reverse of that) Hopefully the TP won't cause any issues.

pusherfans · #44 (**permalink**) 08-10-2010, 04:50 AM

Well, I am done. I confirmed it. It still drives awesome. Perfect street manners. The street carb was the way to go for me. TP back on, verified the O2 sensor readings and no changes. O2 sensor off and we're done.

gsharapa · #45 (**permalink**) 02-10-2011, 08:26 PM

Came across this on YouTube that pretty much supports the lower power valves with big over lap cams.

http://www.youtube.com/watch?v=Va2cd...eature=related

RET_COP · #46 (**permalink**) 02-11-2011, 03:08 AM

Pusherfans,
When you were having your problems did you look at how much transfer slot was exposed like a earlier poster suggested?

I believe that carb came with primary throttle plates drilled with 1/16dia. or so holes, is this correct?

If so Im wondering if the throttle plates holes were too big or not needed in your case because of the bigger upper bores and you were getting too much air causing you to bring the idle down and then causing you to have almost no Transfer showing. This is a classic case as you described.

By filling in the holes temporarily, thus causing a lower idle, you would have had to open up the blades some, exposing more transfer slot, which would have covered the transition from idle to main circuit..

I'm sorry I just found this thread. But I was curious.

Lou

pusherfans · #47 (**permalink**) 02-11-2011, 05:24 AM

Quote:

Originally Posted by RET_COP

Pusherfans,
When you were having your problems did you look at how much transfer slot was exposed like a earlier poster suggested?

I believe that carb came with primary throttle plates drilled with 1/16dia. or so holes, is this correct?

If so Im wondering if the throttle plates holes were too big or not needed in your case because of the bigger upper bores and you were getting too much air causing you to bring the idle down and then causing you to have almost no Transfer showing. This is a classic case as you described.

By filling in the holes temporarily, thus causing a lower idle, you would have had to open up the blades some, exposing more transfer slot, which would have covered the transition from idle to main circuit..

I'm sorry I just found this thread. But I was curious.

Lou

Thanks. I changed carbs with a Street carb (Holley HP4150 Street, 850 cfm) and all of the problems went away. I just put in the correct power valves for my vacuum idle and adjusted the floats and idle mixture and rpm and it was perfect! Thanks.