350 Sleeve or 305 block
 

I currently have a 86 Camaro with a 350/330 crate motor that I run in IHRA stock eliminator. I am thinking about building a 305 engine so I can run some in the NHRA. Is it legal to sleeve a 350 block to make a 305? Or do you have to use a true 305 block? I have heard conflicting answers. I have been unable to find this information in writing anywhere. Thanks in advance. Jason Tucker

Re: 350 Sleeve or 305 block
 

Yes, you can legally sleeve a 350 block down to 305 bore size.

Re: 350 Sleeve or 305 block
 

Alan,
Thanks for the quick response. Jason

Re: 350 Sleeve or 305 block
 

Two bolt mains only as the 305 was never available with four bolt ...Trevor

Re: 350 Sleeve or 305 block
 

They count main cap bolts in Stock?

Re: 350 Sleeve or 305 block
 

The Dart 305 block is 4 bolt mains and I was told is legal for stock? The small bore bowtie 182 block is 2 bolt main and also legal but very hard to find. The 305 block # 627 filled is a good option.

rod butcher

Re: 350 Sleeve or 305 block
 

Slightly off topic but aren't many 396 racers using sleeved more common 454 blocks ?

Re: 350 Sleeve or 305 block
 

If the Dart block is an accepted product, there's no problem with running it. I think you would be lots further ahead by buying one and doing it up. How many stock blocks do you have to go through before you find one that sonic tests OK, is crack free, is not core shifted,etc. before you can go ahead and use it? If you have to reject 4 or 5 OEM blocks before you get a good one, you spent enough on the rejects to pay for a Dart block. One thing about the Dart block-it's heavy. They don't seem to care about the main caps,however.

Re: 350 Sleeve or 305 block
 

Some, yes, I have one. But the Dart block is the way to go, the only drawback is weight. If I did not already have the prepped 454 block left over from a 427, I'd have bought a Dart.

Re: 350 Sleeve or 305 block
 

Yes, been happening for decades.

Re: 350 Sleeve or 305 block
 

My dart little m weighed 218. Almost 40 lbs more than unfilled stock block.

Re: 350 Sleeve or 305 block
 

Have used the same stock 305 block (filled) for 15 years. ARP main bolts, good crank and rods in excess of 7400 RPM, no issues in a stick shift stocker. You do need to pay attention to the stock block core shift though. Pick a good block to start. My 2 cents worth 🏁🏁

Re: 350 Sleeve or 305 block
 

If you want to go fast and have the best of the best the dart blocks are hands down the way to go. In the grand scheme of things they don't add much cost either if you think about all the costs associated with prepping a stock block. The 305 replacement is a nice piece, as are the little m and big m accepted blocks for those applications. Unless a customer already has a block and refuses to upgrade we don't do any engines without starting with the dart block, just make sure you get someone who knows what they're doing to hone it.