Hooked up the power valve

[MNcarbturbo]

And the car runs like junk.

I stole a switch off my boosted 3800 project and finally put it on my car for a PECV/PEVR switch. I just have a switch that turns on at 3" of vacuume, a line coming off the intake for mainfold pressure, and a switch to block the boost pressure from making it to the power valve. So at 3" all signal is cut to the carb and the power valve goes full rich.

My problem is it runs bad from 6" to 1" of vacuume. I didnt have the switch hooked up yesterday so the power valve ran directly off mainifold pressure. I had the same issue. Runs worse than it normally does when cold, and when up to operating temp it bogs from that 6-1". If I keep it at 1-2" long enough it will pop out the carb, which Im assuming its backfiring. It runs 2000 RPM at 8", 1900 at 7", 1800 at 6", 1700 at 5" and so on until its running at about 14" at 1" and just is a slug. But once I go over 1" the thing comes right back alive and runs normally.

This never happened with the the power valve vented disconnected. No cold running issues, no poping, and definitly no flat spot in the carb. That is the one thing I changed and runs flat out bad.

I had the same problem last spring and the car wouldnt even think of running. I know the power valve stop height was messed with by the previous owner and at the advice of a local carb guy I pulled the plug above the top of the power valve and build an adjuster so I could play with that height. It doesnt make any difference where it is. Runs equally bad everywhere.

My question is, if that height adjustment is only for idle, why does the car run so bad at speed? I know its not right to run without the power valve but the car runs so good with it disconnected and so bad with it hooked up I can't think of whats wrong.

 

[charlief1]

I hate to say it but the substitute electrical PECV/PEVR isn't all that effective. The 301 Garage Forum Has some good info and one of the guys even rebuilds them if your's is broken. Those guys did some good research on them and found out that it starts reacting at 3psi and closes completely at 5 psi.

You mention vacuum but are you talking about boost or the vacuum signal on the carb?

 

[MNcarbturbo]

My understanding what the PEVR valve does is you have to supply fuel for the 2" or whatever it is on the manifold side and not the 5" on the pre-turbo side. Since there is less vacuume on the pressure side of the turbo rather than the carb side you have to supply fuel for the lower vacuume, wich this does.

I am talking about the vacuume signal to the power valve, which is hooked to the manifold pressure.

I know its not 100% right, but this setup should be function the same as a true PEVR at the area im having issues. If a PEVR makes the power valve go full rich at 5 PSI, mine goes full rich at 1" or so. I have an issue with the carb being way lean at 2" manifold pressure, its bad until the power valve goes full rich wich is around 1", and as soon as that happens it runs great.

I really wish I had a AFR guage right now.

 

[charlief1]

This should help some. It explains how it works and who repairs it.

Destroying the PEVR!

 

[mat231v6]

And the car runs like junk.

I stole a switch off my boosted 3800 project and finally put it on my car for a PECV/PEVR switch. I just have a switch that turns on at 3" of vacuume, a line coming off the intake for mainfold pressure, and a switch to block the boost pressure from making it to the power valve. So at 3" all signal is cut to the carb and the power valve goes full rich.

My problem is it runs bad from 6" to 1" of vacuume. I didnt have the switch hooked up yesterday so the power valve ran directly off mainifold pressure. I had the same issue. Runs worse than it normally does when cold, and when up to operating temp it bogs from that 6-1". If I keep it at 1-2" long enough it will pop out the carb, which Im assuming its backfiring. It runs 2000 RPM at 8", 1900 at 7", 1800 at 6", 1700 at 5" and so on until its running at about 14" at 1" and just is a slug. But once I go over 1" the thing comes right back alive and runs normally.

This never happened with the the power valve vented disconnected. No cold running issues, no poping, and definitly no flat spot in the carb. That is the one thing I changed and runs flat out bad.

I had the same problem last spring and the car wouldnt even think of running. I know the power valve stop height was messed with by the previous owner and at the advice of a local carb guy I pulled the plug above the top of the power valve and build an adjuster so I could play with that height. It doesnt make any difference where it is. Runs equally bad everywhere.

My question is, if that height adjustment is only for idle, why does the car run so bad at speed? I know its not right to run without the power valve but the car runs so good with it disconnected and so bad with it hooked up I can't think of whats wrong.

so i take it the home made one is no good.

 

[MNcarbturbo]

Im not going to say it was a failure yet. I think theres something else going on here. I almost think my metering rods are too small now with a cam, ported heads, exhaust work ect. Or that the valve is sticking. Something like that. Im assuming its running lean with it hooked up, almost like until the valve goes full rich its stuck as far down as it goes. Maybe the little rubber seal is getting caught too.

I think this electric way should work, theres almost gotta be something else wrong with it. Theres no reason it shouldnt work. Its hooked up the way it needs to be.

 

[WarWagon]

I really wish I had a AFR guage right now.

You should, I agree save $250 for one. If your not constantly reading the plugs to try and get a handle on AFR.

 

[MNcarbturbo]

I disconnected the line going to the power valve and regained all driveability. Smooth, good idle, ect.

I put my hand vacuume pump on the line and I can't keep the power valve down. I can usually pull down about 25" of hg without too much effort with the little pump. I put it on the power valve port and it doesnt even think about holding the vaccume. It either has a big leak from the seal being torn or something or it just doesnt seal. I should be able to pull vacuume for more than the 1/2 a second.

I think Im going to tee in a guage and see if it actually holds the vacuume to the power valve or it just has a massive leak. I have a feeling this is just a fairly bad leak that is pouring in unmetered air making the car run so bad.