One thing I love about our passion, each of us is free to do things our own way. Even through the years I've changed my approach to things from WFO to being more concervative. I go to car events and marvel at the novel/new approaches to doing things. However I tend to appreciate simple and well thought out, to price is no object 21 Century gizmo infested equipment. My son appreciates the latter.
My approach for the turbo was based on having used that model turbo in two other projects, and many hours of testing and playing with it. I found the turbo, which is quite small actually, was not meant by Buick to make their cars dragsters, but to boost the low end without effecting economy. If one was looking for just Horsepower, you'd look for a bigger unit that came slower, but harder up top. Even on the 225 Mopar, it was on the wastegate before 2000. It was easier on it to see when it reached it's 7.5 as the mopar had a stick. When I istalled it on the 250 it was on an automatic with a looser TC. It would light the tires in an instant, and the needle on the VDO gauge always looked like it was directly connected to the throttle pedal. Anything that quick in a turbo is leaving HP on the table. The 225 used a single 2" throttle propane carb. It had more than a 50% increase in power over NA propane, and perhaps had a little bit more in it but it started to lean out as it approached 160RWHP. The Chevy proved that a small gas carb, a 2" SU, could make some pretty big HP as it attained 16lbs of boost when the wastegate was disabled. We needed to put a lot of water in it when we did that to prevent/minimize detonation. Using a larger carb would have not helped much as the compressor inlet in that turbo is only 2". When I chose the carter, I knew it would flow less than the SU, simply because 1 7/8" is smaller and the SU actually flows better for throttle size than a venturi carb. The Corvair 1st series of YH carbs was rated at 170 cfm. I couldn't find a rating for the last series, but at 1/8" bigger, it would flow better. Figuring that engines generally work at about 70% volumetric efficiency, a 50% power increase would represent 105% volumetric efficiency. 200 CFM at 105% is about 23-2400 rpm in a 250 L6. Knowing that it would be on the wastegate well before 2000 we know that the small carb can supply max torque. As I was using a stock longblock I wasn't looking for 300hp. The smaller carb will go quite fat on the upper end, and that was preferable to me than spending time, money, and underhood space on some kind of water injection. Timing was to be taken care of through a Dale Engineering vacumm advance unit as I had used in the previous 250. KISS was the main imputous to that design. Had I wanted to turn top times at the strip, it would have been a whole different thing.
MBHD
Your friend was right about the taillights. Good eyes, that one.
Last edited by Greybeard; 02/01/11 08:21 PM.
