Luke Skyjacker

iTrader: (1)

Ended up with a 6.5. We will see how this works soon

Luke_PCScarbs

Agreed.

The 6.5 will work just fine with a stock cam. Good luck with the setup, pm me if you have any questions. I'd love to help.

xpndbl3

iTrader: (23)

I wasn't aware holley changed pvcr diameters over the years?

Luke_PCScarbs

Not all carburetor part numbers have the same PVCR sizes.

Pop N Wood

iTrader: (1)

That is what I have in my LS2 with a stock cam. I'm happy with it.

I'm running a 71 primary and 74 secondary jet. My PVCR is unmodified and measures 0.050.

xpndbl3

iTrader: (23)

so the 750/850/950 double pumpers have different sized pvcr in them?

I'm assuming you work for a carb company? what do you charge to drill/tap the pvcr for those blanks so I can try out different sizes?

Luke_PCScarbs

pm sent

Luke Skyjacker

iTrader: (1)

Luke can u give us a crash course in PVCR? Just trying to get an idea of what your referring to here.

Pop N Wood

iTrader: (1)

McMaster car sells brass 6-32, 8-32 and 10-32 sets screws for next to nothing. You can easily drill and tap any orifice in the carb yourself. Here is a pretty good article on how to do it

http://www.innovatemotorsports.com/r...FI_mileage.php

Another thread describing it.

https://ls1tech.com/forums/conversio...de-anyone.html

I didn't need/haven't yet modified my PVCR restrictions, but I did drill and tap the idle feed restriction and airbleeds this way.

You can also buy metering blocks with replaceble restictions (Quick fuel, proform), but at a few bucks per jet/restriction it is massively cheaper to drill and tap a standard Holley unit. A bag of blanks from McMaster Carr cost about the same as a single quick fuel restictor. I did buy a set of bottom taps, but standard taper taps work as well.

Here is an excellent link that talks a lot about PVCR's in Holleys

http://www.google.com/imgres?imgurl=...26tbs%3Disch:1

Luke_PCScarbs

Notice in the Chevy High Performance article that is in the first link, they don't talk about the AFR at the race track. Some of what they did was outragous, and is VERY detrimental to power. Good on fuel economy though.

The last link has some good, GENERAL tuning tips in it. There are some very important "to do/not to do" things when modifying your PVCRs that none of these links discuss.

Luke_PCScarbs

The PVCRs (Power Valve Channel Restriction) are visible when the power valve is removed. They act as the jets for the power enrichment of the main circuit. When the power valve opens, fuel passes through the PVCRs to get to the main wells. By increasing the size of these it can allow you to run less main jet. So when your engine is under light cruising load (and power valve is closed) you can get better fuel economy. If sized properly, when under a heavy load (and power valve is open) the main circuit will see the same amount of fuel as it did before you modified the metering block. Thus, still achieving the proper AFR at WOT.