I asked a question a few months ago and got great advice, so I am hoping for another helping answer. I am rebuilding my first 350 in my k1500. Is is cost-effective to replace the crank shaft, or just machine it? Is it also necessary to replace the harmonic balancer and flexplate? The truck only has 90,000 miles on it, and it is a work/tow truck. I an changing almost everything else in and on the engine; intake, exhaust, pistons, cam, heads, etc. Any help would be great. Thanks.

 

I was looking to this tread for the same answers regarding the harmonic balancer and flexplate. I got a new block and heads, but am wondering if I could put a smaller diameter harmonic balancer on the engine. Seems like summit has a package with balancer and flexplate for about $110, but the balancer is smaller than what I took off the old engine. Summit lists that it's compatible with engine from 1967 to 2000 so not very specific. What will be changed when you change the balancer? Vibrations only? Would a smaller one necessarily create more vibriations? Isn't weight an issue also?

 

Ok first of all as far as the crank it all matters how much it has to be machined. If it is over .030 then i would say replace it. It is not worth keeping a part that has been machined smaller especially if it's the crank. Cams ok Crank i just say no.

As far as the harmonic balancer it already has 90,000 on it so just replace it cause most likely you wont get another 90,000 out of it.

For the flexplate i would look at the teeth to make sure the starter is going to have plenty of grip on that sucker to make sure it is going to last at least 100,000mi , since most rear mains go out by 100,000mi anyway, also i would check and double check around the bolt holes to make absolute sure you have no stress marks/cracks at all since this would cause it to break thus making you pull the tranny premature. Another thing you might do with the flexplate is get it magnafluxed at a local machine shop to make sure there aren't any cracks. I've never done it but im sure it wouldnt cost much.

Scany, buy it if they say it works then it works the diameter and weight doesn't matter at all the only thing that matters is if it fits your application and that it dampens the vibrations this isnt done with weight or diameter but the compounds in the rubber inbetween the two weights. Again if they say it works then it will and if it doesnt then send it back.