My neighbor has a tbi L05 we put in his old land cruiser a few years ago.
just blew a head gasket. I have a set of low mileage 083 tpi heads. Will this increase the compression ratio up to much on the L05 ? I think he has swirl ports on it. It’s from a 87 full size blazer.

 

If he used a .020 shim HG and had .016 deck height he'd be right at 10.1:1 CR with iron heads and a really nice .036 quench. Obviously the deck height is a thing of variance and worth measuring. I'd place odds on it being slightly lower though. With some Felpro HGs you'd be at 9.73:1 and probably with a not so great quench.

I'd use the shims and do a little love to the chambers around the valve area to add a CC or two (and some flow.) I'd also want a decent exhaust if possible and I'd be wary of towing with it too. If he's got a carb he should be aware of the tune on it. If he's doing this you should understand why he puked HGs out too. You could just be throwing gasoline on a fire there by upping CR and putting new HGs into it.

 

Aren't the LO5's dished with 4 valve reliefs? If so, with an .020 or so steel shim gasket, you'd be right where the L98's were...about 9.3. Assuming GM casted and machined everything perfectly....

 

Brain fart, if they're L98 heads yeah you'll be basically where you started compression wise. I thought they were LB9 heads for some reason.

You'll gain a bit of performance probably but not really a ton. If you ported em out you'd do a decent bit better. Then again if you ported the swirlies you'd probably do a decent bit better as well.

 

Compression will stay about the same. You can expect to need to retune it with a more aggressive timing map. Will lose a large amount of low-midrange torque (probably in the 20+ ft/lbs range) and not equal the performance of the TBI heads until about 4,500 rpm. At 5,000 rpm you would be lucky to see 10 hp gain.

 

Thanks all for the input, he’s thinking now of reusing his old heads now.