Engine SwapEverything about swapping an engine into your Third Gen.....be it V6, V8, LTX/LSX, crate engine, etc. Pictures, questions, answers, and work logs.
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question on engine compression ratio with current motor swap
im in the middle of swapping over an l98 motor that has 500 miles on it.... stock short block... have an option of getting athe aluminum l98 heads that have been worked over some but have been milled to 53 ccs... the guy tells me that would put my compression raito at like 10.5 to 1 witch to me sounds low as the iron l98 heads are 64 ccs and stock compression is like 9.5 to 1 or so... so basically i woudl liek to confirm this before i give him the money for the heads and i have a motor that has insane compression thats not streetable... we have 93 octane here so id be running that anyway....
thanks
__________________ 91 RS mods: 342 posi rear, spohn lca's and panhard rod with relocation brackets,ls1 driveshaft, built 700r4 trans with slp 2400 converter, b+m trans cooler, stewart stage 2 water pump, 1 5/8 edelbrock headers with 3' flowmaster exaust, 3 inch catco cat, i , msd distributor and msd wires, walbro 190 fuel pump, 58 mm throttle body, slp runners, ported stock intake. ac delete.
* Putting her together after 5 yrs of sitting . 350 tpi going in finally!
Re: question on engine compression ratio with current motor swap
The iron-head L98 with 64cc heads was rated 9.3:1 with steel-shim head gaskets, the aluminum-head L98 was rated 9.5:1 with thicker composition head gaskets, because the aluminum heads didn't mix well with GM's steel-shims. If you use fel-pro steel-shims, you could see over 10.5:1, which is fine. If you use the GM 12557236 head gaskets, you'll be around 10.0:1. But if you have flat-top pistons, the felpros will push you over 11:1, which I advise against.
Re: question on engine compression ratio with current motor swap
ya i have the stock short block with jsut some autozzone replacement head gaskets currently sitting in my car... i mean 10.5 to 1 is fine.. any sugestions on witch head gaskets???
__________________ 91 RS mods: 342 posi rear, spohn lca's and panhard rod with relocation brackets,ls1 driveshaft, built 700r4 trans with slp 2400 converter, b+m trans cooler, stewart stage 2 water pump, 1 5/8 edelbrock headers with 3' flowmaster exaust, 3 inch catco cat, i , msd distributor and msd wires, walbro 190 fuel pump, 58 mm throttle body, slp runners, ported stock intake. ac delete.
* Putting her together after 5 yrs of sitting . 350 tpi going in finally!
Re: question on engine compression ratio with current motor swap
The FelPro steel-shims for a 350 Chevy. They only make one design. It is rubber-coated, 4.100" bores, 0.015" compressed thickness, so your pistons better be at least 0.020" below the decks.
