408 stroker rod bolt interference?

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bricud

bricud

Cuda's Cuda
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I am in the process of assembling my 1973 LA 360 block to make it a 408 stroker. I have a Molner forged rotating assy with H beam rods. I noticed after putting in the first two piston assys that the clearance between the rod bolt head and the block is very tight. About .040 on the first one and about .02" on the other. This is between the head of the rod bolt and the bottom of the cylinder. Anyone have this issue? Do I need to remove things and remove some block material? What should the clearance be? Thanks.

rod interference.jpg
 
This is common on stroker motors. .002 and even.040 is not enough as crank and rods "grow" at speed. This is why many of us have a good machinist in our back pocket.
 
a little clearance job would be ideal. It should be simple enough with a die grinder or dremel. I would test fit all the pistons and mark the block as appropriate rotating the crank a few times. Disassemble, have at it and then clean everything. If you can control all the metal shavings best you can. Containment or vacuum. Stock rod bolts probably would have cleared just fine but you got the good stuff they protrude out a bit more.
 
It will clearance itself the first time you hit 6k rpms …lol

Worth the time to disassemble and clearance then a good wash . But while it is assembled mark where the bolts come close to the block with a grease pencil or such .
 
Sounds good. I'll be taking it apart and make take the dremel to it. Any idea how much clearance is good? I was thinking more than .10. I don't want to find out the hard way...
 
Sounds good. Now my biggest concern will be cleaning it properly without taking it back to the machine shop. I'll take time to cover everything close to the area I am working and vacuum and/or wash it when done.
 
Power wash the bare block , blow it dry and a couple cans of WD40 then wipe it down . You can never wash a block too much .
 
Agree with the 1/16th inch. We use a "zip tie" as a gauge. they are about 60 thou thick and add a kink/ bend near the end of the tie. Here's some more tools that make it easier.
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bricud said:
I am in the process of assembling my 1973 LA 360 block to make it a 408 stroker. I have a Molner forged rotating assy with H beam rods. I noticed after putting in the first two piston assys that the clearance between the rod bolt head and the block is very tight. About .040 on the first one and about .02" on the other. This is between the head of the rod bolt and the bottom of the cylinder. Anyone have this issue? Do I need to remove things and remove some block material? What should the clearance be? Thanks.

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My 340/420 with K1 4.00” crank and rods had the same issue. My machine shop took it back apart and clearanced it as needed.
 
It could be worse. I bought an early stroker ‘ kit’ (haha) and the pistons hit the crank. No warranty.
 
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