The original 215 aluminum V8 appeared in the Buick Special and Skylark models, while the Old's version was offered in the Olds F-85, Cutlass, and Jetfire models as well as the Pontiac Tempest.
The Buick version used only five bolts per cylinder to mount its heads, and the heads had a combustion chamber following contemporary Buick practice. The heads were also angled "upward" to create a "flat top" look common to Buick engines of the day. Buick altered compression ratios via piston height and design. You can bolt a Buick head to an Olds block.
Olds engineers went their own route with cylinder head design, preferring a Chevy small block-like combustion chamber and an extra bolt (six in all) around each cylinder to mount the head. The valve cover was also more conventional looking. (Ken Costello built his first MGB V8 using an Olds engine picked up in Belgium !). The valve train is also different. Old used different heads with the same pistons to produce higher compression ratios. An Olds head will not work on a Buick block because of the extra head bolts. For performance applications, you'll want either 829 heads (10.25:1 C.R. for '61-'62 4 bbl auto and manual cars, '63 4 bbl manual cars), or 534 heads (10.75:1 '63 4-bbl automatics). Two bbl heads (No. 746) have low compression ratios and aren't suitable for any performance work.
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