compression ratios ??

[Blown57]

What's up, nice site you guys have here. I'll try and keep this as short as possible. I have a 57 Chevy with a roots blown smallblock that I've been thinking about switching to a blow thru carb set up. I'm currently running a 385, 4.040x3.75, smallblock with a 4-71 single carb blower and a alcohol dominator. The pistons that I'm running are SRP blower pistons that list as 9.8 compression with a 64cc head, which is what I have. The block was decked a little so the compression might be a little higher than that. The car has ran 10.0's at 133 with little tuning and I feel it has a 9.80 in it still, but I would like to change it around where it would be more streetable. I've been looking at maybe getting a F1R set up with a intercooler. I'm guessing I have around 10.0 compression, how much boost could I run on pump gas/race gas if I go with a set up like this ??

Thanks in advance for the help and if you would like more details about the engine just ask.




Matt

[regattacoupe]

Welcome to the site and thank you. Do you have any pictures of this monster? Thats a pretty cool sounding car by the way. As for pump gas and a 10:1 compressing ratio the tune is very critical. I don't know about blow-thru very much so i'm not going to pretend to. On pump gas you probably won't even get the F1R into it's effiency range. 6-10psi depending on tune? However with race gas you'll have a real monster on your hands. Let us know what you decide.

[Blown57]

Thanks for the compliments, I'll post a couple pics tonight. It's not much of a looker though, been in primer for years.

A little more info...the blower I'm using is a old Dyers street setup and it really isn't meant to be spun as fast I'm currently running it, 28% overdriven, and it's only making about 8-9 lbs of boost. The engine has 4340 crank/rods, Dart Iron Eagle heads with 2.08/1.60 and a crane solid roller blower/nitrous cam. I would really like to see low 9's out of this engine and I think it's probably possible with a blow thru. Running race gas is not a issue either, the car doesn't get driven much, I'm also assuming that upping the boost for race gas is just a simple pulley change,,correct??

One more question for you guys,, when does o-ringing become neccessary ?? I've been told several different things on this, some say 12 lbs, some 15 lbs and I've seen a few roots setups on big blocks go 20lbs and last all season, but I know that is over the limit and really pushing things.


Thanks
Matt

[regattacoupe]

Well primer is an indication of a fast car and i've been a primer racer more than once. Honestly that sounds like a solid combo, and the iron heads should have no problem holding a gasket with good quality gasket and good ARP head studs. Everyone has an opinion and my opinion is that boost dosen't blow head gaskets, a bad or aggresive tune blows head gaskets.

As far as the F1R is concerned what ever pulley is on there to begin with would be a good baseline and I bet it will be bad fast if the tune is in check. I don't have a ballpark as to where it will be right off the bat but the F1R leaves all the headroom you'll realistically need.