SSC

Last night I was trying my new 700r4 out (ballz out) I hit above the tach redline 6k+ and pop pop.
I slowed down and the idle was really crappy 600rpm in gear and 600rpm out. It sounds like the GEN IV power valve protection failed
I took a vac reading when I got home and it's jumping 15/17in. Power valve right??
Well anyway I never pulled running vac in gear, out it pull's 15 1/2in where I have the timing set to. Im going to assume that in gear it should have been around 10ish, close enough?? My other car backs down around -5in, in gear so I'm going to base -5in for in gear load. Does that sound like a safe assumption (-5in) for load? So 8 or 8.5 powervalve should be right for this setup according to holley. The old power valve is a 6.5 and I havent had any problems except for the blow out last night. I'm tempted to go back to a 6.5 but 8 or 8.5 is what holley recomends and should be better.

With this in mind what should I choose 6.5 or 8?
SSC

Jester

Newly Ordained Minister of the Universal Life Church?

You could try blessing the carb see if that helps Seriously tho whats that for..tax break?

As for the PV, I'd just run a 6.5 and not worry about it. Unless you have a midrange flatspot that an 8.5" might fix..you probably won't be able to notice a difference. they don't make them in 8"..only half sizes.

SSC

:hail:I tryed blessing the carb dident work, so I condemed it to a eternity in the firey pits of hell:nono: http://www.ulc.net/?source=goto
Running a non profit orginization has it benifits and its legit in my state.

Yea 8.5, I just looked it up. They do make an even 5 PV though. I guess I'll stick to the 6.5.
Thanks Jester!
SSC

RB83L69

Power valves don't care about engine RPM. Only moving parts are concerned with that. Pop at high RPM and fluctating vacuum do not equal dead power valve. There's something else going on, maybe valve train related. The vacuum indicates that one or more cylinder is drawing air in differently from others.

The 6.5 PV should work OK, but may give you a hard choice: either jet it a little rich on the primaries and get poor gas mileage, or jet it correctly and maybe have a tip-in sag especially when cold. A higher numbered valve would work better, up to the point where it opens at idle. 7.5 or 8.5 usually works better with mild cams. I'd suggest experimenting with it when you get the other issue worked out, which I would suspect a loose rocker at the very least, and quite possibly more than that.

A blown-out power valve will produce an extremely rich idle, very poor gas mileage, and generally weird part-throttle behavior.

SSC

The pop sound came from the carb, when running an open eliment filter its unmistakeable yet no black spot on the inside of the lid.
It was beltching black smoke when I got home. The really odd thing is I just moved it into the garage and it's acting fine!!! What gives here? Im going to take your advice Reb and adjust the valves to make sure. Im going to pull a vac reading on it in a few minutes. I think I'll leave the guage connected while doing this to see if theres somthing screwy.
Thanks!
SSC


Maybe the prayer worked

chevymad

Its acting fine now?? I wonder if the float drop is set too far. When you were on it the fuel level dropped then the float stuck. Now that its had some time to sit it come loose again and is back to normal. Something else to check anyway.

onebad82z

iTrader: (7)

So,I have a quick question for all?I have a tip in sag as RB83L69 describes it.I have jetted my carb,done everything under the sun to get rid of it but it remains!!I am running a 750 DP Speed Demon with 70/75 jets,stock pink accelerator pump cam,.31 squirters.It is on my 355 with AFR 195 heads/64cc(box stock),Weiand Stealth dual plane,Comp Xtreme 487"/490"-230/236 dur @.050 cam,10:1 CR,4 speed manual trans,3.73 gears.I still have the 6.5 power valve in the carb it came with.Would going up to a 7.5 or even an 8.5 help kill this sag I have?I am fed up with it.I have jetted the carb down which has helped clean up the mixture but it is still a bit rich,but yet if I go any leaner the sag gets worse.Could this be a power valve issue??

Jester

onebad82z- No. That sounds liek a lean accel. pump problem. Experiment with different pump cams, and/or go to the next size squirter up in the primaries.

SSC

I'm not sure. I dident get to work on it last night. It could be that happend and it went lean (pop). I set everthing when it got a new engine back in November. I need to get back into town and I'll check that, being on call up and down the front range sucks!


SSC