2 bolt or 4 bolt

[botlfed]

is there any way of telling wether my lt1 is a 2 or 4 bolt main without pulling the pan i will be pulling the pan in the next couple months when i do the ai heads and cam swap. im just wondering if there is a way to tell by the vin or casting numbers

[Injuneer]

No way to tell, other then looking at the main caps. All LT1 blocks have the same casting numbers. Only the Corvette engines were 4-bolt. All B-Bodys and F-Bodys had 2-bolt mains. But some 4-bolts were used as "replacement" engines in F-Bodys, when the engine was replaced under warranty.

For a normally aspirated application, the 2-bolt block is more than adequate. With a "power adder" setup, you would be looking at finding a stock block with straight 4-bolt mains, or having your 2-bolt block converted to 4-bolt.

[1slo_camaro]

just for my dummness would a 2-bolt converted to a 4-bolt be weaker, considering your drilling and all into the block?

[Injuneer]

Depends. The LT1 block was designed for straight 4-bolt mains. Hence, there is extra "meat" in the webs to accomodate those bolts. The arguement is then whether you want to install a "straight" 4-bolt conversion, which would obviously be stronger than the 2-bolt setup, or would you want to install a "splayed" 4-bolt conversion. In any case, you use beefy forged caps.

The shop that built my engine did a bit of homework on the LT1 blocks. A buddy of mine was running a 383 LT1 with over 20# of boost, making 1,125HP. The block was a Corvette straight 4-bolt block. The shop claimed that they felt the LT1 block was stronger than a traditional factory SBC, and a lot more like the Chvy Bowtie performance block than anything else. They also felt that the webs were designed to handle the straight bolts. I have a splayed conversion, and so far its holding together, but I'm only at about 800HP. We got into the discussion of "splayed" vs. "straight" after my block was done, but before they built my friend's engine. They eventually tore his engine down, because he wanted even more power. The block was in good shape, and he sold it to yet another friend who was builing an 1,100HP nitrous motor. I'm not sure how far he ever got with the nitrous setup.

[97LT4SS]

My '97 block has 4-bolt mains, saw them during the rebuild. It's the original block, because the VIN matched.

[1slo_camaro]

hey fred thanks for the clarification like all ive ever dealt with was 4-bolt bbc and sbc i never knew you could switch a 2-bolt to a 4-bolt i was afraid to eeven think about it cause i didnt want anything to break lol but now i know its ok to do lol thanks buddy

[Injuneer]

My '97 block has 4-bolt mains, saw them during the rebuild. It's the original block, because the VIN matched.

That's because you have a Corvette LT4.

[97LT4SS]

I never knew SLP used an LT4 block. I always thought SLP modified the original LT1 with LT4 components (Intake, Heads, Cam). I've owned the car since 1999 and never put two and two together. Great news for me.

Thanks Fred