Power valve?
 

I've got a 68 Camaro stocker that currently has a 461 in it.I've always ran a primary pv in it when it had an automatic,it now has a stick,no changes to the engine.It's very choppy in 1st gear going thru the pits,clears up halfway thru the gear.Do you stick guys run power valves?

Re: Power valve?
 

Sorry,I meant to post this in tech.Will the moderator please move it? Thank you.

Re: Power valve?
 

A power valve will help but you dont want it to rupture if you ever had a backfire! I never run them have had good luck without!

Re: Power valve?
 

Just to be clear,it does have a pv in it now,same one that it had with automatic.

Re: Power valve?
 

Power valve is only affected by engine vacuum. and it must be closed at idle The # on the PV body is the inches of vacuum it will open.
Check the engine vacuum and use a PV a couple inches higher.
Think I got it right. :)

Re: Power valve?
 

Maybe around a 3.5 PV just a guess?

Re: Power valve?
 

I've been advised to do away with any PV...no more guess work.

Re: Power valve?
 

I never run them my homemade carbs get the job done!

Re: Power valve?
 

Thanks everyone. Power valve is correct for engine,even tried a new one,cleaned out carb,blew it out,float level and fuel pressure checked.This carb worked very well with a foot braked auto,crisp and did not have the problem going thru the pits in 1st gear.Problem started with stick installation,it's choppy and surges until about 2500-3000 in first then is fine.I just wondered if the stick guys pulled the valve....I'm going to order a block off plug and up the jets......Thank you.

Re: Power valve?
 

I am watching this question with interest.

*one thought, when driving at low speed only have the throttle open a small amount and regulate the car speed by selecting whatever gear gives the desired pit road speed.

*I have experimented with power valves on gas carbs. I like the low speed performance and cleaner when staging with footbrake. With trans brake leaving where you are wide open on converter or two step I do not run a power valve.

*I do know it is common with Methanol carbs to run a primary power valve.

It may mostly come down to personal preference.

I would like to know the % of who runs what.

Re: Power valve?
 

I always blocked the PV on my carbed stocker. You have a different load now compared to when it had a converter.

Sean

Re: Power valve?
 

I have had quite a few alky carbs seen and rebuilt others for friends and have NEVER seen one with a Primary or otherwise PV! Not sure it's real common?

Re: Power valve?
 

Thanks,Sean. I wondered if that's the problem,the converter flashed to around 5,800. Thanks.

Re: Power valve?
 

BLP and APD both use primary power valves with Methanol. I should have said, "power valve usage with Methanol in common with BLP and APD"

Yet, I am off subject for the original question, I apologize.

Re: Power valve?
 

Your running on the transition circuit in the pits, it's prob lean. Power valve has nothing to do with that unless it leaks. Then it will pull fuel down the vacuum port behind it.

Re: Power valve?
 

My APD HP1000 methanol carb has never had a power valve in it. I've had 3 methanol carbs over the years, and none have used power valves.

Re: Power valve?
 

Take it out and plug it. It does not affect idle or transition to the booster. Yes it works on engine vacuum ,but it only richens the mixture when the vac is low and the engine is pulling fuel thru the boosters. You should bump your primary jet size up if you do take it out. on our 585 we usually go 76 pri and 78 sec. 396 motors 78 pri and 80 sec.

Re: Power valve?
 

Thanks for all the replies,they give me some good direction on fixing the problem.