Chevy Nova Forum banner

1 - 7 of 7 Posts

·
Registered
Joined
·
556 Posts
Discussion Starter #1
Whats the rule of thumb about jet size increase after you block off the power valve in a holley carb.
 

·
Premium Member
Joined
·
10,210 Posts
DriveWFO said:
I think it's 8 jet sizes.
Yep just about right on..here is what the Mortec website says about this;

Mortech.com Website said:
Many tuners will automatically remove the power valves and use a "plug" thinking this is the "hot" ticket. However, if the power valve is removed and plugged, the main jet size must be increased 6-10 jet sizes to make up the required fuel amount lost by the removal of the power valve. In addition, when the power valve circuit is plugged, the part throttle fuel economy is worsened and may become overly rich. Plug fouling may become a problem at part throttle.
http://www.mortec.com/carbtip1.htm
 

·
Registered
Joined
·
556 Posts
Discussion Starter #4
thats what I needed
 

·
Registered
Joined
·
31 Posts
I don't understand this idea of jetting up if you block off the power valve.

Why not block the port in the carb that feeds the valve, and then leave the power valve installed?

Correct me if I am wrong, but a power valve shuts off at the rated vacuum. If the port is plugged in the base-plate, it will never see that vacuum, and as such it will never close.

So you would have a rich idle, but should be as intended up top. Thoughts?
 

·
Registered
Joined
·
4,612 Posts
interesting

never thought of doing that ,, it would effect idle though ,,

alot of people feel that blocking the power valve , is better , worrying about if the passage ( pvrc ) would be come blocked , that it would starve the engine , maybe burn something up ,, so they block it and jet up to compensate ,

sometimes , a big motor will develop vacume at high speeds and loads , which might cause the PV to shut , leaning the engine exactly when you don't want it to happen ,, so ,,, blocking it does away with a few problems ,,

i've wondered about an electronic tuneable power valve , :rolleyes:,, do a feed back from an O2 analyzer to control it , , etc etc
 

·
Registered
Joined
·
31 Posts
i've wondered about an electronic tuneable power valve , :rolleyes:,, do a feed back from an O2 analyzer to control it , , etc etc
They make those... it's called EFI. lol.

I just blocked my valve because I bought a car with a blower that didn't have the valves boost referenced... ran like crap but it much better now. Still idles like ****... though since it never managed to pull enough vacuum to open the power valves in the first place.

I'm going to switch to EFI pretty soon... just wanted a way to get by for a few weeks.

EFI is pretty affordable these days. You can get a MegaSquirt for less than $300 ... everything else for about a grand.
 
1 - 7 of 7 Posts
Top