Did Buick use different pistons in the 2 barrel and 4 barrel engines if so what were the part numbers?
Had a look at the parts catalog, looks like three different pistons, below: Std size Piston & Pin part numbers: 1395513 1964-65 - V6 & 300 - Export 1399524 1964-67 - V6 & 300 - Domestic 2bbl 1399525 1964-67 - 300 only - 4bbl So it's probably a safe bet that compression ratio differences were due to pistons, leaving the cyl heads common...though I didn't chase cyl head numbers. Devon
2 barrel 300 was advertised at 9 to 1 but replacement pistons are 8.2 to 1. 4 barrel 300 was advertised 10.25 but replacement pistons are 9.5 to 1. There was a 340 HP piston that was advertised 11 to 1 . 64 had aluminum heads, 65-67 had iron heads.
The aluminum head had a slightly smaller chamber then the iron head, they advertise 4 barrel as 11:1 for aluminum and 10.25:1 for iron, 2 barrel 9:1 aluminum and 8.5:1 for iron. Some say these numbers are higher then they really are.
Good info. If the later engines mimic the early ones, then the early engines may have suffered from excessive deck height also, reducing actual static compression ratios. Just a guess. Devon
I took a peak in the parts pile and the pistons from a 1964 Buick 300 4 barrel engine carry part number 1357552 and were made by Alcoa. They are a flat top with a very shallow recess but no valve notches and a full round skirt design. The 4 barrel equipped engine was advertised at 250 HP @ 4800 RPM and 355 lbs-ft @ 3000 RPM with 11:1 compression ratio versus 9:1 for the 2 barrel. Cylinder heads were nominally 54ccs. I've got an OEM head gasket around here and should run the numbers sometime but I suspect the actual compression ratios may have been a bit lower. Often, the quoted numbers are for a highest possible given a stack up of production tolerances.
To be fair about it, the 2bbl version of the engine with factory 9:1 compression pairs very nicely with the MGB body to give excellent all around performance. It really is generally a very substantial step up, bringing the car overall into the Muscle Car realm quite handily. Jim
