Mopar mega. Block

Whats the max bore size for a mega block not a Siamese block

Cesar, assuming you mean Hemi, a megablock means it is siamese bores. If it does not have core shift, it will go 4.500. A regular Hemi block is generally good for 4.310

The instruction sheets that shipped with them originally claimed they'd go to 4.600" actually, but I don't know anybody who's tried it.

Ours is on 4.565 sonic checked ok on thrust apart from back cylinders no. 7 & 8 bulkhead side are a bit thin but no probs yet and holds temps well with street driving/racing, but the combo makes max hp @only 6000rpm.

I thought the later MP/World "megablocks" were the only ones that claimed they'd go out to 4.600"?

In my response above, I was referring to the pre-World Mopar Hemi blocks.

There were 2 different mega blocks 1 was a siamese the other wasn't. The siamese has mopar cast in the block above the 2468330. As you can see 4.31 is the max recommended bore for the full water jacket block.

Mike

Fwiw I have a full water jacket block and there's a sticker on the bellhousing area that says 4.34 max bore.

Maybe best to just have it sonic checked.

Just for Info, we had a 4.50 bore 528, using an early # 625. The block had a crack in the external water jacket nr the starter. We got it repaired but we still always had to run it with block / rad sealer. Doing a little bit of digging I heard there was a few out there like that. Anyway, we got a replacement block sent over to the UK FOC after my wife managed to get hold of Dave Hakims email address,that one was a #624. We ran the 528 for years and it's still going with another owner but then we wanted to go 572. We dug the #624 out, it was sonic checked, there was no way it would safely go out to 4.50". We ended up with a KB block.