Blow thru carb jet/pvcr calculator
 

Anyone know of an online calculator to quickly determine the amount of jet change needed when opening up the pvcr to keep the same AFR? Thx.

I sent Charlie66 a calculator some years ago for his blowthru carb work (before he went to EFI).

I would contact him and see if he still has that excel file and can send it you you.

Tom V.

Thx Tom. Correct me if Im wrong but you can calculate the area of both orifices to get a total? Then say you drill the pvcr larger, calculate that additional area and then reduce the jet the same amount of area? Will that be correct?

Yes that is correct.
Stock, as you know is 2 Power Valve Channel Restrictions typically .059" on a 850 cfm 4781 Holley carb.

Low boost PVCRs can be increased to about .084" for each one.
More boost then you drill (and add 2 more PVCRs at .059" and based on your boost and AFR numbers drill those out to the size needed.
Again stop around .084" for each one.

If you are like Charlie, Lots of Boost, then you go with SIX PVCRs and go thru the same enlargement process along with bigger jettings too.

Hope that helps. AFR/Lamda Gage is your friend, along with a SHOTGUN RIDER actually reading and documenting the AFR/Lamda numbers on a clipboard. Fast car with lots of boost, hard to do it all yourself safely.

Tom V.
ps Find a very quiet road that you can use for your tuning without irritating the locals.

Thx for the info Tom.