The 74-75 pistons look like the high compression 1970 pistons and can be easily mistaken as such. But the 1.935 pin height problem takes away any possible chance of good performance and produces no quench at all. Look for this number inside the skirt...1231733...this is the correct 1970 piston with 1.975 pin height and shallow dish.
I measured the 70 stock pistons I just had removed from a spare rusted bore motor I have to use the rods for another motor. The pin height varied from about 1.974 out to about 1.987, all in the same motor. Most varied from one side of the piston to the other a few thousandths, and one of them measured 1.975 on one side and 1.987 on the other. Maybe this one motor isn't typical, but if you happened to get a motor from the factory with all pin heights on the high side, you got lucky and a good runner.
* TA Performance sells a stock replacement cast piston like the 1970 but has an even better pin location at 1.997 and a 22.5 cc dish. Part number TA 1607. Ask them if these match the stock balance if you intend to just swap pistons on a budget job. * In the photos, the piston on the far left is the most desirable 1970 part number 1231733. * The third one to the right is the 1976 that is often mistaken for a 1970 shallow dish, but has the very low compression due to the 1.935 pin height. Many aftermarket "stock replacement" pistons are similar to the 1976 piston and sold as a "one size fits all" piston. Check specs before buying, but better yet call TA about that dandy 1607. .
Yet more reasons to NOT use OEM pistons from Buick. (heavy, poor QA) Guy's gotta be nuts to not use aftermarket pistons on anything beyond a grocery-getter.
Only reason I'm using stock 70 pistons and a 35 year old c118 cam, in my 11 second Buick, is poverty. It may blow up any time, but hammering stock Buick pistons since 1960 without a blown engine or even a blown piston, has been lots of fun for this poor boy. I think this is my thirteenth motor, (from different cars and engine upgrades). The end may be near... Anybody got a good short block with them nice Auto Tec pistons for sale cheap? All I have is stage 2 heads, B4B and an old quadrajet, and 58 years of experience pounding the livin hell out of old Buicks.
Got a set of the stock bore TA1607 pistons hung on a set of recon'd stock rods ready to go in my stock 71 motor as soon as I get time to pull the motor. Just gonna swap the rods/pistons out. I will try to get some deck to piston dimensions before and after the swap to document what I've got and just for putting the info out there. And to figure my before and after compression ratio change on a stock motor.
TTT with more info... Got around to swapping my TA1607 pistons in over the weekend. My compression ratio with stock 71 pistons/heads along with FP head gaskets and stock deck height(piston depth varied from .040-.045) figured around 8.2:1. After the piston/rod swap along with using McCord steel shim head gaskets(think they're .020 thick, forgot to measure, someone let me know if I'm wrong), piston to deck height was between .030 to .035 , the c.r. now figures to be about 9.5:1 using the .035 number. Also swapped out my weak break-in springs for TA1435(TA288-94 cam has about 120mi on it now) and topped it off with a B4B. Just thought someone might like to see info like this.
Got a part number/source for those steel-shim gaskets? Be fun to take the engine apart in ten years or whatever, and see if there's any witness marks from the pistons/heads touching.
Pistons/heads touching with .050-.055 quench? (.030-.035 piston to deck + .020 gasket). It's still more quench than recommended. Bought the gaskets from Tom Rix. Part number label was missing. http://v8buick.com/index.php?threads/buick-455-mls-and-steel-head-gaskets.333545/#post-2802658
Hehe. Turns out the no-ethanol 87 octane ain't gonna cut it. Got some detonation at WOT now. Hoping 92-93 oct no-ethanol will be plenty in the future. Going to see about getting a 5 gal can of 104 unl to add to my current half tank of 87 to bring it up. TA288-94 definitely runs better with more compression. Lol
You should be OK on the 93. Last fall I ran my flat top, 7cc valve cuts, at .03 down, .040 gasket with 73 cc heads....that like 10.75 and we had no issues on 93 with 32 timing
