am posting this here since I believe you guys have more experience with higher HP motors. I just replaced my 350 with a 396 stroker. Picked up car from my mechanics(friends) shop when completed and I found brakes at about 50%-60% of what I recall in stopping ability and pedal travel is compromised( increased). Vac leak? I think not. Cam is 236/242@.05 and a 112LSA. I have not yet looked at the VAFPR but I suspect idle FP is less that what it was prior(20 lbs idle 43 lbs at WOT 98 MAP. My datalogs in 60 miles of cruising showed higher MAPs than prior in cells that saw light cruising idle MAP is now 65-70 and prior was 50-55. Idle was left too high(1000 rpms) as it was increased during first start and break in at shop. I did not reduce it(forgot). That might explain in part the higher MAPs but only partially. Looks like a vacuum booster is needed. Question is whether I can place the vac line at the manifold tapping into the nipple fitting at rear passenger side of it? Don't think it wall adversely affect fuel tables(lower MAP results) as I will just see globally lower MAPs. .Also no room in engine compartment so will place unit in storage compartment behind passenger(C4) and run line along fuel lines and up firewall.

Thank you for comments.

 

 

There is little room under the hood of a C4. It looks like it will go in one of two compartments (10"x 10" x 10") behind seats.

 

thay run about $350+ for the aftermarket pumps