I just finished rereading the diy blow through carb.
My question is do I have to drill my pvcr?
Can I run my setup without modifying it?

I was thinking leaving it stock then mod it if I need more fuel.

Anybody run stock size pvcr?

 

How much boost..power?

I say open up the pvcr's

That said you could start with a stock size but most at least open it up slightly. You can work your way up on PVCR size. The mistake some make is too big too soon.. but that can be resolved by drilling/tapping the pvcr for set screws

You will need to jet up both pri/sec sides.

 

10 psi max and lower if I hit 450whp before that.

Carb is 650cfm holley 4150 on 302 ford.

And do you know the stock pvcr size?

 

10 psi miiiiight be ok with stock pvcr's if they are .039's, if your high speed bleed are small. Plenty rich for me on a 308 with an A/A and 7 psi. If you are 10 psi and an IC, you probably need to go up a bit.

 

The reason for drilling the pvcr is to keep from having to run a huge primary main jet. Stock should be .039" like 10sec said. Just to give you an idea of what drilling pvcr does a 78 main jet and stock pvcr should be about the same as a 71 MJ and 1/16" or .0625" pvcr. Drilling them to 5/64 or .0781 will only need around a 62 MJ to have the same flow. If you have a set of wire gauge/numbered bits you take smaller steps.

I started out with stock pvcr on mine, but had to jet up so much that the car did not run very good when not in boost. Drilling the pvcr let me use a more normal main jet which helped off boost carburation. I got it jetted at WOT and then figured the total area of restriction, MJ+pvcr, and then started jetting down the primary until I was happy with cruise, being careful to stay out of boost. I then figured what pvcr size I needed to get back to the area that I started with. I use this calculator http://www.1728.com/diam.htm and this jet chart http://www.angelfire.com/fl4/pontiacdude428/HolleyInfo.html To get area.

 

Cool thanks guys.

 

Yes, I just dragged a thread up from the cellar. I am running a inline 250 with a Garrett T3 through a Holley 350cfm 2bbl. I got trigger happy with the hanger18 mod and drilled the PCVR'S to .078" from the start. I have it dialed in pretty close, but gets really rich (10-10.5) on the wideband during boost. My idle and cruise are spot on.

I need pictures or a good description on how to make the PCVR'S smaller.

Thanks

 

^^Sounds like you need to go smaller on the secondary jets. What do you got in it?

 

Two barrel doesn't have secondary jets,
Drill and tap the PVCRs to 10x32, (just don't run the tap all the way in) and put brass setscrews in them, drill the setscrews to your desired orifice size.

 

How much boost? and How much jet do you have up front?


As for reducing size of PVCR -
1. Buy new metering block
OR
2. Drill and tap for small allen head set screws. The set screws will then need a PVCR hole drilled for a smaller size.