Hotrodder

Hi there thirdgen guys. Wonder if you can help me out with this one. The more I search the web for information about the L05 engine the more confused I get. I have decoded the engine and found out what it's possible from that. I also have the chassis number from the engines donor car which was a 1992 Buick Roadmaster. The engine is a factory roller lifter 2 bolt block. Correct me if I'm wrong, but it seems to me that there was (at least) three different versions of the L05: 1. Non roller. (Trucks & vans) 2. Roller lifters. 3. Roller lifters with 9C1 package (Caprice only) Judging from that my engine should be a "version 2" (If the alternatives are correct). But when it comes to compression the information differs a lot. Some say 8:1, while others say 9,5:1. What's correct for my Roadmaster engine?

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Adapt - improvice - overcome.

Damon

I beleive it's 9.3:1. -193 swirl port heads they used on that motor are, I believe, 64cc chambers and the pistons should be slightly dished units (-12cc). It would be difficult to get down to 8:1 with 64cc heads. Somebody can double-check me on that I'm sure.

kdrolt

Damon is basically right. 64 cc chambers, -193 casting number, 9.3:1 for the passenger car models. IIRC the pistons aren't dished on the passenger car models (though they are slightly on the trucks, hence lower CR on the trucks), but the pstons will have double eyebrow (valve reliefs) that total approx 5 cc per piston.

Hotrodder: the only differences between the 1991-1993 copcar 9C1 Caprice LO5 engine and the one used on passenger car models in 1991-1993 Roadmasters, Custom Cruisers, Caprice and the 1993 Cad Fleetwood, is the cam, injectors, the ECM tune, and the Ypipe on the exhaust. The 9C1 copcar got the -773 cam from the TPI Fcar, using more lift and duration. The larger injectors, revised ECM tuning, and slightly lower exhaust Ypipe boosted the power from 180 fwhp to 205 fwhp. OTHER than these items, the copcar vs non-copcar car models had identical engines; same heads, same block, same pistons, same roller lifters, same intake etc.

Truck TBI 350s were very similar, but they mostly has flat tappet cams in the light duty trucks (rollers made it into medium duty trucks circa 1995), and they had lower restriction exhausts. The trucks also had the slight dished piston to allow lower octane fuel and to be more resistant to detonation during heavy work. FWIW, HTH.

Hotrodder

Thank you very much!

In other words: The engine will do well with a pair of modified vortec heads, maybee a little thinner head gasket and high lift cam.

I don't think I would have gone that route with a 8:1 compression engine.

I have already rebuilt it with an Airgap intake and will top that off with a 650cfm carb later when the hot rod is ready for the road.

(I'm aware of the different bolt patterns on the Vortec heads)