Went back to Cecil Sun, air was about the same as week before. Barometer a little lower but the temp was a little lower, too. Still not super air. Jetted up 4 sizes from 94 to 98 on the 9375 Dom but exhaust temp only went down 15 deg. from 1485 to 1470. Still way to high, right? Can't see that I should have to go to 100 jets! Car did pick up some, revved quicker and best mph yet 131! Anyone out there running this much jet on a Stage 2? Bruce BQUICK 10.22/131
Bruce, I think your going to find staying at 94 square or maybe 95 square will be your best package. J
But isn't that exh temp too high? And the motor seems to respond to more fuel....thing is greedy! Bruce
You may need to have the carb built for your application. If it picks up both et and mph then it likes more fuel. The larger jets in your carb do not mean that you are getting more fuel than smaller jets in someone elses carb. If it takes that much jet in normal air you won't be able to jet properly in really good air, get the carb redone for your application you will be glad you had it done. I had a dominator on my old engine that would run over 1600 deg. with over 100 jets in it, had it recalibrated with new boosters, emulssion tubes, metering blocks and air bleeds and was able to drop down under 90 square for 1450 deg. max readings and picked up 3 tenths. Where are you taking your egt readings and and what point in the run? Is that a max reading on the temp or are you reading an average, beggining or end of the run? My gage was set to read a max temp and would be highest through the top end. My car liked 1450-1475 deg. at that point.
Hey Dennis, thanks for the response. I'm taking the reading about 1.5 inch away from #8. MAX (peak) from run. Who did your carb? I was thinking of drilling out the intermediate and high speed air bleeds to keep it crisp on the bottom and jet up a couple more. OK, I don't feel so bad seeing that you are running similar EGTs. Bruce
I had pro systems out of Michigan do mine. I had them build it originally and was unhappy, after the second time it was very nice. They can wet flow the carb for a baseline and do the work to it, wet flow again when finished and help with adjustments after that. They would need all of your experience with the carb to compare with the wet flow performance and can figure what your engine likes. My carb was kind of a shot in the dark the first time and they missed, but with my info on how the carb worked on the engine they nailed it the second try. That max egt reading can throw you a curve, try to check during a run to see where you really are for temps. Once you figure out what the car runs at a particular temp you can dial the car very well with the use of the gage.
Dennis.....Wouldn't it be cool if you could hit a button and save EGT at different points down track? Say right at top of 2nd then after shifting. I can't really look at my EGT on a run.... safely....... Bruce
You could try setting up a camcorder inside the car next time out. Just make sure it can see the guages and the EGT readings and you've got a "high-tech data recorder".
A power versus an EGT graph on a piston aircraft engine shows max power is made at about 50 degrees F on the rich side of the EGT curve and not at max EGT. I suspect the same or similar results would apply to an automotive piston engine.
Pro Systems did my carb on Mighty Mouse and they did a phenominal job. I have about 24 pulls on a chassis dyno and the EGT and 02 curve is as good as it gets. I wouldn't hesitate to use them again. J
Last Dominator I saw requiring that large of a jet wasn't getting enough fuel . Is the supply system up to the job?
250 Mallory pump, 1/2 in lines, return-style regulator. Hmmmm, pump does seem quieter than when new this spring. Maybe it's going away.... I guess I need to put the ole fuel pressure gauge on the cowl and look at it going down track, The AutoMeter electric gauge only worked for a week..... Bruce
Problem solved. Talked to Mike at Holley (very helpful, he has a Buick), he said my 9375 Dom is designed for a 2-4 set up on a tunnel ram, so it has big high speed air bleeds. Very difficult to get it rich enough on top end with a single 4 setup. So I went down to 28s from 34s and bingo, temp went from 1470 to 1380. Car went 10.20 on the brakes (killed 3 mph). Now the carb will respond to jet changes. Bruce
Good job Bruce, My 9375 has never responded to jet changes the way I thought it should either. If you don't mind, I'd like to piggyback on your hard work. Which air bleeds are the high speeds? Where did you buy new ones? Thanks a bunch, see me at a Buick event year for a cold one.
Hey Shayne Actually I robbed some 28s out of a 9377 (1150) that I have. Couldn't wait.... Haven't rec'd the air bleeds from Holley yet.....but they are supposed to be on the way. They have size 23 blanks that can be drilled. The high speed air bleeds are the ones closest to the squirters. I drilled the idle air bleeds out some to improve streetability and idle. Also, allows the mixture screws to have more effect. Bruce
Just checked mine and they're also 34's. I'll get some for tuning next year. There are an awful lot of 9375's out there on 10 & 11 sec. Buicks, I wonder how maney could be having similar issues and not know it?
Just some thoughts from my world. I just talked to a local shop that has a chassis dyno about doing my car. They build some very nice Outlaw 10.5 cars out there. He suggested at the very least make a few dyno pulls with their O2 sensor to set-up the A/F curve. I have always belived that it is very difficult to set-up the high speed bleeds at the track, unless you have a data recorder. An EGT meter only reads max temp, but where did that happen? You need to record a graph over the entire RPM range to get it right. Another point about EGT meters, where do you turn it on? I have seen motors show higher EGT's during the burnout than going down the track. Burnout = part throttle, high RPM. Race = full throttle, variable RPM. It will make a difference. Have fun.
