HELP! 283 crankshaft won't fit in 283 block

[studiog]

Hi,
I am building a 283 motor for my 1961 Corvette. I have found the correct block casting and date for the car... a 1961 block. I also have a fresh reground 283 crank according to the casting numbers and I even measured the stroke to be sure it wasn't a 327. When I did a pre assembly of the crank in the block I found that the counterweights of the crank don't clear the block. The cast number of he crank 3876768 indicates it was manufactured between 1964-67. Is there such a thing as an early 283 crank and/or block. I thought any 283 crank would fit any 283 block. Thanks in advance for any help that might be provided.
Gary S. :confused

 

[Tom Bryant]

Hi,
I thought any 283 crank would fit any 283 block.

Gary S. :confused

I did too. Your crank is definately a 283 crank. Check this list.

http://www.mortec.com/cranks.htm

The last replacement crankshaft that Chevy listed in the parts book for a 283 was for all engines '57-'67. A one part fits all type of offering. They were all small journal. I'm not sure what the original application on your crank was. In the '64-'67 area some of the 283 blocks used a different casting than the earlier ones. The Chevy IIs for sure, and maybe others, used the same basic casting as a 327 high performance block with the thicker main bearings webs ect. but only bored for a 283. I remember reading in Hot Rod years ago an article on building a 283 for NHRA class racing or maybe just a home built small journal 302, and they used this block since it was the strongest 283 example. These blocks probably had room for a 327 crank so I suppose it is possible that the original crank used might have had bigger counterweights.

I'm sorry I can't be more precise on this. I have a complete 1961 Corvette 283/270hp engine stored over in Indiana at my dads but it's still assembled. I do have a 1957 crank out in the shop that maybe we can compare measurements off of or post comparison photos if someone doesn't have a definitive answer to this problem.

Tom

 

[Viking427]

There IS a difference b/n 283 cranks. You probably have a later 62-67 "nodular cast iron" 283 crank. You'll need a 57-67 "forged" 283 crank. In 1962 GM began casting 283 & 327 blocks with extra clearance in the main webs and cylinder barrel bottoms to accomodate the new "nodular" cast iron cranks. These "new" cranks were cheaper for GM to build but not as dense as forged cranks. Therefore, they required heavier (ie. larger) counterweights to balance the engine properly. The 327 blocks also had additional clearancing for the extra 1/8" stroke.

Interestingly, your 3876768 number is listed in several sources as forged AND cast AND both ...depending on the reference source. However, the sheer fact that its a 283 crank that doesn't fit into your 61 283 block implies to me that its the cast crank.

BTW, the 58-61 (& possibly 62-67) 283 blocks are thick castings and can take a .090" or larger overbore if you check for core shift. Just don't try "clearencing" the 57-61 blocks for a cast crank (or any larger "stroker" crank for that matter) or you'll hit water !

 

[studiog]

All 283's are not created equal.

I found the answer to my own post so I guess I will reply to it in case someone else runs into the same problem. Seems there are early and late 283's. The late 283's are factory relieved at the bottom of the bore to accept the larger crank counter weights of a cast crank. The ealy 283's are not relieved and will only accept the smaller counterweighted forged crank. I also found out that the late 283's will accept some 327 cranks. Learn something new every day.

 

[studiog]

Thanks

I guess I got some replies after all. Thanks everyone for the response. I am new to this forum and I think it is great. Thanks again
Gary S.