402 BBC rod problems
Maybe off Corvettes,I have a '70 402 #3909854 block for my '70 Nova SS. I ordered a kit from Calif to rebuild the block.Anyway I have 7/16" rod bolts and they are hitting the pass side of the block in a big way.I had this assy balanced and would like to use it as is.The 7/16" rods/bolts are bigger and about .220 longer than the std 3/8" rods that I have off an old 454.The crank is the 6223 396 crank and I'm using KB pistons. My question is: how much meat is on the bottom of the cyl wall before I have a problem? Do I need to use the 454 3/8" rods. I have a die grinder,but all 8 rods/block will have to be worked.I need to remove about 1/4" or so on the block.........
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Re: 402 BBC rod problems
Paul-----
I think you mean GM casting #3969854. This is the 1970 402 block. There never was a block of GM #3909854.
As far as the rod bolt interference goes, no Chevrolet 396, 402, or 427 was ever manufactured with 7/16" rod bolts EXCEPT 1969 L-88/ZL-1. So, no 402 block was ever designed to accommodate rods with such bolts. Notwithstanding that, I believe that most 396, 402, and 427 blocks can be clearanced to accommodate rods with 7/16" bolts. However, it may depend on the rods being used. If you're talking about GM rods with 7/16" bolts, I think it can be done. As far as other rods, I'm not sure.
We'll need clem to weigh in on this one. I'm sure he's been "down this road".In Appreciation of John Hinckley -
Re: 402 BBC rod problems
you must have aftermarket rods i would think as i never saw any problem using GM BBC rods with 7/16" bolts. i must admit i never used the GM 7/16" rod bolt rods in a bore smaller than 4.250. i have had to clearance early blocks when using a 4" 454 crank but not the amount you are referring to. are these cap screw rods not the thru bolt like the stock GM BBC rods ?Comment
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Re: 402 BBC rod problems
I had to grind a little on my 5439 block when I went to 7/16. Wasn't much but it was most necessary.Comment
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Re: 402 BBC rod problems
The rods are after market with standard 7/16" ARP bolts in them. I can take a little of the bolt after installation,but I would rather cut on the block if possible.I was trying to assemble an engine for the Nova and thought that a kit would be easier as I had no internals for the 402.Joe is right the block is 3969854,I was was bummed today as I was engine building until I hung #1 and #2 piston in the hole and tried to move crank.How far up in the cylinder can I safely notch?.....I can see a very little of the botton skirt of the piston when it is at BDC........Comment
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