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Jetfire block vs f85/cutlass block

Home Page Forums Discussion Topics – Ask the Experts Jetfire block vs f85/cutlass block

This topic contains 16 replies, has 6 voices, and was last updated by  captiannapalm 1 year, 2 months ago.

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    I’ve seen vague mention of the jetfire block being “beefier” than the standard block. Does anyone know this to be true? If so where does the “beef” come in? Mains, caps, both?



    I am sure others know better but I do not think the block was any different. I think it was just the pistons, rod caps and rod bolts. They had better bearings but all replacement bearings now are the same as the Jetfire bearings were.



    if thats the case i wont seek out a jetfire block i know about for a future build. if anyone else knows any different please let me know



    They were stamped specific to the Jetfire on the front pad. It is nice to have the correct number stamped in the block but other than that I do not think there was a difference. I would also assume that the Jetfire specific stamp is to identify it as a short block assembly and not the specific Jetfire block. If there is a difference I hope to learn myself.

    The Jetfire stamps were also specific for 62 and then for 63.



    Here’s a bit of info. According to that April 62 parts book, Olds did not list a bare block, only a block assembly that included the fitted pistons, rings, and cam and main bearings. The 2bl, 4bbl, and Jetfire block assemblies all had different part numbers, primarily due to the different pistons. There is no indication of any differences in the bare block casting.



    Are you looking for anything specific? I have a 63 Jetfire engine I am going to pull apart and sell off what is still good. The pistons are frozen in the cylinders but will not know how bad it is till I get it apart. If the block is ok I would sell it for $300. If you wanted to chance it I would sell it as is, intake to pan for $500, exhaust manifolds and turbo stuff not included. I know at least one spark plug hole will need fixed. It is a 4 speed engine but no flywheel.



    My understanding is that the Turbo engines have deeper bolt holes/longer bolts for the main bearing caps. I believe there are some other small differences but they escape me at the moment. I’ll check back if I can find the info.



    The Jetfire block is different than a 215 used in any other body style. The main bearing cap bolt holes were drilled and threaded 9/32″ deeper. The main bearing cap bolts are 9/32″ longer and have 12 point heads. The pistons used were only used in ’62 & ’63 Jetfire’s and ’63 4bbl carb cars. The main bearings were “Marine-400” bearings and were unique to the Jetfire cars. The heads and valves were different too, but you only asked about the block. You can make a Jetfire block from a non-Jetfire block by drilling the main cap bolt holes deeper and threading them to fit the longer Jetfire bolts. Functionally, it will work, but as Eric states, the block identification will be incorrect. Just depends on what outcome you want?



    Just looking for a stronger block without going rover block



    Checked with the machinist and also uses beefier rods and longer head bolts.

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