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Old 04-14-2018, 11:00 AM   #1
davepl
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Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
Watched a guru tune my carb yesterday...

My 427/390 (2+2 project) went on the dyno yesterday. Started out dead lean, even though it was supposed to be set up for stock, so I was lucky enough to be able to get Larry Webb to come out and tune it.

Larry spent SIXTY YEARS with GM as well as various race teams. He was at Alan Green Chevrolet up here. He's really the expert on Rochester Mechanical injection but obviously knows his way around a Q-Jet as well. They were turning rods down on the lathe to make custom ones, that's the level they were operating at...

Made 402/498 on a rated 390/460. What's interesting is that the 3% increase in displacement yielded exactly a 3% bump in rated power!

That's my brother holding up the wall watching, not me!

Also interesting to me was that it was leaning out and he didn't just fatten it up. He spent a lot of time looking over the dyno numbers and then decided it was a fuel delivery problem, which it turned out to be, the mechanical pump couldn't keep the bowl full. Imagine trying to sort that out by yourself, on the truck, without a dyno! You'd probably never know that you're truck only made 275hp instead of 400hp!

I'm really ambivalent because I've had the opportunity to meet some really fascinating and talented guys like Larry over the last several years, and none of them have apprentices. You'd really hope a guy like this would be teaching the next guy up, but alas I think most of that knowledge will die with them when they go!
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1970 GMC Sierra Grande Custom Camper - Built, not Bought
1969 Pontiac 2+2 427/390 4-speed Coupe
1969 Pontiac 2+2 427/390 4-speed Convertible
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