Power valve?

Dana Fitzpatrick · 07-16-2016, 03:00 PM

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?

Dana Fitzpatrick · 07-16-2016, 03:23 PM

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

BLIND MULE · 07-16-2016, 03:31 PM

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!

Dana Fitzpatrick · 07-16-2016, 05:20 PM

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

Chevy55 · 07-16-2016, 07:08 PM

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.

BLIND MULE · 07-16-2016, 08:24 PM

Maybe around a 3.5 PV just a guess?

HandOverFist · 07-16-2016, 08:30 PM

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

BLIND MULE · 07-16-2016, 10:59 PM

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

Dana Fitzpatrick · 07-17-2016, 10:51 AM

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.

Woodfin · 07-17-2016, 11:42 AM

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.

07-16-2016, 03:00 PM	#1
Dana Fitzpatrick Member Join Date: May 2009 Posts: 148 Likes: 4 Liked 10 Times in 6 Posts	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?

07-16-2016, 03:23 PM	#2
Dana Fitzpatrick Member Join Date: May 2009 Posts: 148 Likes: 4 Liked 10 Times in 6 Posts	Re: Power valve? Sorry,I meant to post this in tech.Will the moderator please move it? Thank you.

07-16-2016, 03:31 PM	#3
BLIND MULE Member Join Date: Dec 2002 Location: Alabama Posts: 318 Likes: 0 Liked 0 Times in 0 Posts	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!

07-16-2016, 05:20 PM	#4
Dana Fitzpatrick Member Join Date: May 2009 Posts: 148 Likes: 4 Liked 10 Times in 6 Posts	Re: Power valve? Just to be clear,it does have a pv in it now,same one that it had with automatic.

07-16-2016, 07:08 PM	#5
Chevy55 Banned Join Date: Nov 2014 Posts: 324 Likes: 625 Liked 179 Times in 89 Posts	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. Last edited by Chevy55; 07-16-2016 at 07:11 PM.

07-16-2016, 08:24 PM	#6
BLIND MULE Member Join Date: Dec 2002 Location: Alabama Posts: 318 Likes: 0 Liked 0 Times in 0 Posts	Re: Power valve? Maybe around a 3.5 PV just a guess?

07-16-2016, 08:30 PM	#7
HandOverFist VIP Member Join Date: Oct 2013 Location: Gulf Breeze, FL Posts: 1,651 Likes: 8 Liked 33 Times in 16 Posts	Re: Power valve? I've been advised to do away with any PV...no more guess work. __________________ Rich Taylor I/SA - 321

07-16-2016, 10:59 PM	#8
BLIND MULE Member Join Date: Dec 2002 Location: Alabama Posts: 318 Likes: 0 Liked 0 Times in 0 Posts	Re: Power valve? I never run them my homemade carbs get the job done!

07-17-2016, 10:51 AM	#9
Dana Fitzpatrick Member Join Date: May 2009 Posts: 148 Likes: 4 Liked 10 Times in 6 Posts	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. Last edited by Dana Fitzpatrick; 07-17-2016 at 12:02 PM.

07-17-2016, 11:42 AM	#10
Woodfin Senior Member Join Date: Sep 2006 Location: Kilgore TX Posts: 536 Likes: 8 Liked 274 Times in 105 Posts	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.