Need turbo advice please- '70 z28 rs

kree

New Member
Joined
Jun 4, 2003
I'm new here guys! i dont have a buick GN, but i joined this forum cause you guys are turbo junkies and know your stuff. I have a '70 camaro rs/z28 with a 406 pushing about 425hp with about 9:1 compression. I was thinking about twin turbos with the budget upside-down header installation or even a single turbo with proper plumbing. can anyone tell me what would be the ideal turbo and A/R ratio to make a 9 sec. car with a single turbo? Thanx guys
 
I cannot give you an answer, but can offer some help.

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first thing would be, are you running some kind of efi or a carb? if your going carberated, forget about it, your MUCH better off with a blower. from what i have seen the guys who run twin turbo setups usually have pretty small turbos, like te33, having 2 of them works out to be about the same as a +/- 66 with less lag thanks to their smaller size. if I were you I would really concider a single turbo, they can make about the same power and its a whole lot less complicated, and cheaper too. I'm not a turbo expert at all, but I think I would start out with something cheap and go from there, like a used gn turbo, see if its over kill or not enough before you spend lots of money on a new turbo. just my thoughs.
 
Thanx guys - some specific questions....

First off, I'd like to thank everyone helping me out on this. Your advice is much appreciated. After doing some homework I am leaning toward a single turbo. My engine specs can always be adjusted (cam,stall speed etc.) What I really need to know is what turbo is best for my 406 to get into the 9's. Since the baseline of my 406 is higher than what a stock 3.8 would be without a turbo (approx. 400+hp), can I get away with using a turbo thats not as serious as the ones that GN's use to get into the 9's. For example, would I be able to pull it off with a PT60 series turbo? Or can I do it by running less boost. ie. 15psi instead of 22+psi? What would be the best trim size for use with my displacement? What would be the ideal A/R ratio? and How can I calculate this? Also, what is the best way to handle the oil return line from the turbo with a small-block chevy? I do have a supercharger-ready carb, so what would be the problems assosciated with this setup? I was contemplating using a carb with an extra injector before the carb to richen the mixture according to boost. What would be the best EFI system to use for my setup? I was thinking of converting my edelbrock intake by welding in bungs on the runners for the injectors, then using a 90 degree pipe on top where the carb would be and mounting a throttle body to it. However, if I do this, what should I use as an ECU to controll it? I know there are a lot of questions guys, but its the only way to learn. Thanx once again guys.
 
Boy, you are in need of A Plan! First off, if you are serious about going turbo, get the book "Maximum Boost" by Corky Bell. Lots of info in there about adding a turbo to a car. You'll find lots of answers there. How to do a carb setup, carb vs. efi, oil supply and return, etc... is all there.

Until then, I can help you get an estimate of the turbo size you'll need and whether your fantasy is realistic or not. Let's start off simple: you say you want to run 9's. How much flywheel hp do you think that will take in your car? What is the redline rpm of your engine?

John
 
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