It was detonating, mostly because of the vacuum leak but also because the timing creeps up on this car. I have to check it every few months and it is 2-3 degrees beyond where I left it. The spacer was a 4 hole, Mr Gasket spacer. The spacer I had way back when was two 1/4" gaskets bonded together, but while it sat off the car uncompressed it delaminated and gave up vacuum leaks.
a friend of mine had this exact issue with a set of custom-made je pistons on a 425 here recently. He actually sent them a stock piston and ask them to copy the dome exactly and they used the incorrect blueprint instead and he ended up with four Pistons hitting the combustion chamber. he was chasing what he thought was lifter noise until I told him about this thread and the issue you were having.
I'm talking to more and more people that have has the issue...I still have to take this motor back apart, but there are two ahead of it.
i run custom je pistons for 9-11 years now in two different engines one i sold to a member and still running, with piston at zero deck height no problems. stock piston is 50-55 thousands in the hole, no wonder they don't hit. maybe copying the old dome is the problem. if your making custom pistons why would you not move the pin height down to move the piston closer to the deck, then go with a smaller dome. mine have the corners milled .
I thought you were running Tom's pistons. didnt he correct the dome issue when he designed these? the reason my friend had to order custom JE pistons was a special bore size to save a block. it wasn't a high performance build.
The issue is not exclusive to any piston manufacturer. I'm running a derivative of Toms pistons (from Autotec) that I spec'd myself, and they hit. But Tom's spec did not, at least in my original block and heads. Every engine is so specific, I dont think it's quite as simple as buying from one source or another, and there seems to be some issues with the industry wide CAD/CAM profile for these domes. Short answer, fit each piston, and check for clearance with no head gaskets on the motor, no matter what the source.
Quick Update on this year's Pure Stock Drags: The spreadsheet is out and available on the web, very cool intel on what the fastest stock muscle cars are doing at the track these days: https://www.psmcdr.com/pastyears And for the Buick lovers, there were more Buick GS's there than any other make/model - more than Chevelle SS's, Camaro's, GTO's, etc.. Here's how they stacked up: To see how they did against other makes/models/brands, go visit the website OR, Just come out next year! September 18-19 in Stanton Michigan.
Ha! While I was counting only GS's for that discussion, let me specifically mention Starc's BEAUTIFUL 79 Hot Air Turbo Coupe, with a 3.42 rear. He ran a best of 17.1 this year at 79.6 for a bye run win. This car makes an impressive 138 RWHP, and pictures do not do it justice. Including Starc's car, Buick was the third best represented make, behind Chevrolet and Pontiac.
Our group sure enjoyed the Pure Stock Drags and we were only spectating! Thanks for the updates Rhett!
