Ron C. wrote:Are you sure you can get the 16 psi boost out of that 4-71??
If you can you'll probably have to overdrive the heck out of it and that would concern me about the intake temps to run 100 oct gas.
A true 16 psi would certainly reach your goal.
Ron C. wrote:
[/quote]Tokyo Torquer wrote:A 4-71 GMC blower is 280ci.. you would have to overdrive by 40% to reach 16 lbs of overheated boost on a 327ci engine. That is far too much for pump gas and 8.5:1 compression. More reasonable is 12.5% overdrive which would give you ~10lbs boost on the 327.
Mike , my doubt is exactly about that: 4-71 blower aren't very efficient, I think 12.5 % overdrive will not do ~10lbs boost...maybe 5 lbs at that ratio...have you some own experience with they?
I'm choose a SV intake mainly because the air gap it have...it can lower the intake charge temp a few degrees...
That cam is awefully big for that little engine.. are you looking to winde that blower motor past 7000rpm?
Yes the cam is big, but they say that a blown motor "tame" about 10 cam degrees ...shift point would be at 6800
You dont mention whether this is mostly street or track.
40%street 60% track
Dual 750 holleys is far too big for that engine. Dual 600s will do just fine even at that high boost, and never bigger than dual 650's on that 327.
Ok I apreciate your opinion, and now I remember Bill Jenkins had two 1100 dominators on his pro stock 327ci 9000 rpm N/A Vega...
Big Al's Toy Box can sell you an adapter plate to convert a real (6-71) blower intake for a 4-71. You will get better fuel distribution than with the converted 4-barrel intake.
A 355 with a 6-71 would be much better to work with.
I agree 1000%... but both are hard to find and expensive here...
Thanks for reply
Tokyo Torquer wrote:
.. I have lots of resources here to calculate boost for any size roots blower on any engine as well as the BDS and Dyers reference charts.. they all say that you can achieve 10lbs boost with the suggested % overdrive. My first blower was a 4-71 but that was a long, long time ago.
Tokyo Torquer wrote:stripping the rotors will help, but it wears out eventually. the tighter the clearance the more boost you make. teflon strips get you very tight bit wear the fastest. Nylatron doesnt wear as fast, but still wears out. cant say if the hard anodizing is the way to tighten up clearances.
Baprace wrote:BrazilianZ28Camaro, you need disimilar materials to run clearances that may touch, aluminum rotors and magnesium case work well together, a rotor that has teflon strips in it will take up the clearance problems.