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Author Topic:   Replacing rod bolts - can I without resizing big end?
posted March 16, 2004 02:01 PM
Just like the question says - can I replace the rod bolts without resizing the big end? I've heard both ways - from never as it will cause bearing misalignment and sieze, to no problem...

Anyone have expierence either way?

FWIW - this is on my budget/backup 355 and was going to replace the rod bolts when freshening up this year as they've got 4 seasons on them now.

- brian

posted March 16, 2004 02:13 PM
any competent machinist will tell you that when you replace the rod bolts you should resize the rods. the only reason to remove the bolts is to resize the rods. if the bolts are suspect, i'd venture the rods are suspect as well.

posted March 16, 2004 10:00 PM
thats not always true outlaw alot of guys just put good bolts in stock rods bacause they are the weakest link i know i do anyway

posted March 17, 2004 05:10 AM
if you 'hammer' in the new rod bolts with one of those blocks that fit in the vice for installing rod bolts, i give you a 90% chance that you will distort your rod big end..resulting in rod bearing failure

posted March 17, 2004 07:38 AM
The bolts that are on the rods are stock rod bolts. I was going to install upgraded rod bolts in them - that's why I was asking. I was planning on doing some head work or swapping to a 64cc head to bump the compression up and was thinking I might want to swap the bolts out as a preventative measure...

I've got a press and was planning on pressing the bolts out and the new ones in, trying to keep the pressure around the bolt hole and not distort the rod.

posted March 17, 2004 10:12 AM
Originally posted by sideways:
[B]Well if your gonna try it no matter what is said then heres what I'd do.Change the bolts and then have the big end checked for roundness.That way ya know.I asked the same question and I chickened out.

I'm still not decided - I was merely stating that I wasn't planning on just "banging" the bolts out and had thought about the best way not to damage things... Obviously if I used a 5 lb sledge and put the rod small-end down on the concrete and beat the bolt out I wouldn't expect it to stay round... I merely wanted to note the method I was thinking about using and get a discussion going on it.

For measuring roundness - would a caliper with a .001" resolution be good enough to measure for out of round?

posted March 17, 2004 11:39 AM
Dont skimp on this....if you replace the rod bolts, you MUST have them resized. I am sure many will say "we never have and never had a problem", but come on people, resizing after installing new rod bolts is one of the basics of motor building!

posted March 17, 2004 11:41 AM
For no more than a set of reworked stock rods cost from JR Motorsports/Midwest/Speedway, I think I'd just go that route.

posted March 17, 2004 12:04 PM
i dont think i could sleep at night if i didnt resize rods after installing new bolts.
at least have them checked...they will be out of round.
most placed like to see no more than 2 tenths out of round...that .0002 so at caliper that goes to .001 will do you no good.



posted March 17, 2004 12:30 PM
Most aftermarket rod bolts are made of better material than stock bolts. That alone will cause the bore to distort when it's torqued up from the additional clamping force.

posted March 17, 2004 08:00 PM
I've seen it done on a stocker with the rods still on the crank,it did ok but i don't recommend it.

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