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Building a ´71 SCJ now - take two

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Post  gcj April 11th 2021, 12:42 pm

Hi to all who responded to my initial posting on this engine.

We chose the Pertronix distributor, I went with the Clevites and we bought a Powermaster starter. The plan then is to install an MSD box with a built in retard, rev control; the works. This engine has obviously seen its share of battles in the past. It was originally installed in a dark green ´71 Mach with a 3.91 trac lock gear.

But, now we have a more serious issue to discuss.

Upon beginning the short block assembly it is clear that the rods have been balanced in the past. The pads on the rod clamps have been ground down to a differing degree, some almost ground off completely.

Additionally, the lower halfs (clamps) have been renumbered. The machine shop has thus altered the location of all of the rods except nr. 8.

I bought a clean 4U 429 crank since the original was damaged. Then I replaced the original L2366 pistons with a set of the same, except .030 over.

The question I have is this: Which numbering sequence do I use; the original or the custom one? (considering the original pistons and crank are gone)



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Post  BOSS 429 April 19th 2021, 12:04 am

You need to go get the balance checked, of crank, rods, pistons, dampener, and flywheel

rods might of been moved around for other reasons, take it somewhere and get it checked
BOSS 429
BOSS 429

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Post  dfree383 April 19th 2021, 7:11 am

Have it rebalanced

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Post  pmrphil April 19th 2021, 8:08 am

The position of the rods should not matter if they were balanced and rebuilt previously. But the pistons will be a different weight, and the crank is not balanced to the parts you now have. As was stated, you need to have the assembly balanced (again).


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