Hello, this is my first post so please bear with me.
I am building a 408 out of an lq4 engine for my 72 Nova. It will have all forged rotating assy, BTR stage 2 or 3 turbo cam and Holley Hi Ram Intake.

Power goals are appx 700 with the option of turning up the boost occasionally. This is primarily a street car with 1 or 2 times a year track use.

Im thinking of possibly a BW S475 or I already have a Forced Inductions GT91 with 1.08AR exhaust housing.

Id like to use the GT91 as I already have it but am afraid it might be to big.

Any input would be greatly appreciated.

 

What turbine you got on your 91 it will make a huge difference if its a gt55 or f trim, etc.

 

Not 100% sure. It’s listed as a 3rd-94mm. I probably should call Jose at Forced Inductions and see if he can give me some more input on it.

 

The 91 i think will be better but it depends on what turned up means. Honestly i think it will fairly low boost to hit 700 on a 408 and the s475 would do that but if you go with the 91 it will leave you alot of growing room for later on. It will probably be a little lazier spool but not a ton and getting some of the wee out of the car makes it more enjoyable in my opinion and helps limit the ohh **** moments.

 

Thanks for the input guys.

 

The 75 will do what you want pretty easily as will the 91 I would just figure the 91 would be a bit lazier

 

That would be my guess too. Kicker is, I have the 91 on the shelf. Not that the 475 is very expensive but Im thinking I could try out the 91 and if its too lazy Ill switch it out. I just wanted to be sure It wasn’t going to be too ridiculously large for the application. Could be cranked up to 1000 on occasion.

 

My S488 with a 1.32 housing spools like a PD blower on my 416” motor. I wouldn’t worry about the 91 at all.

 

Was going to use my 317 heads but found out today they are fatally cracked. Would like to stay below 2000 on heads and was looking at a set of stock LSA heads pretty hard. What is you guys opinion on those? That or stock LS3s. Top end of my spectrum would be cnc ported LS3s but I think my power goals could be achieved for less.

 

Stock lsa’s or ls3’s will work great and they flow a ton without being ported #squareportmafia

 

I don't mean to sound like a dick, but when did we get so jaded about horsepower that people worry if their built 408 has a little bit of lag before the extra 4 or 5 hundred horsepower from the turbo kicks in? Your tires will go up in smoke at any speed, regardless of whether you chose a few millimeters wrong on size. If this is really mostly a street car, just go smaller. If you are covertly planning to race more, go bigger. Remember, your '72 Nova came from the factory with approximately the same horsepower as a frightened poodle, and was still considered a musclecar.