New Crate Motor "Knock"

It did sound like a piston slap from your original posts. Probably an out of round skirt, did anyone measure up the old pistons?

Bob

 

The KBs are 135s which have a centered pin, where as the replacement Probe ones have an offset pin.

 

Thanks for the details.

I wonder if an engine expert can chime in to explain the reason for the offset pins

I'm getting ready to buy a set of SRP flattops for my 355 & I didn't even know that was an option

 

I want to thank all concerned for an educational bit of detective work that will certainly be kept in mind when I rebuild the chevy mouse motor for my '48 coupe. I had thought of going the 383 route but with all the variables involved, this being a conservative driver type rod, I'm forearmed with enough knowledge to avoid big cube blues and will definitely think long and hard about piston/pin choices, and go the forged route. Thanks for airing out what was definitely a pain in the brain for timewr, who is definitely 'the man' when it comes to patience and perseverance. I wish that you have many care free miles after being 'knocked' around.

 

Very interesting that you found the KB pistons seem to be the culprit. I also have KB pistons in my 331 stroker and as I mentioned in my earlier post, the engine rattles quite a bit. I spoke with Scat and KB and they told me it is because the pistons are so short that they slightly rock in the bores.

But the motor makes good hp, is not using any oil, and I have put a bunch of miles on it, even long trips. So I just live with it and tell people I am running a solid roller cam.

Don

 

I am still trying to get the crate engine manufacturer (BluePrint) to pay some money toward the repair of their brand new motor.

They say " Send back the pistons and, if we can find a "manufacturing defect" with the pistons, we will pay you some of the costs."

Its going to cost me at least $150 to send the pistons from Oz to USA and I know they will not manage to find a defect. The main problem is it has a center pin not an offset pin.

What's the saying .... "throwing good money after bad".

 

Yep, that's a crate engine for ya!

But hey, everybody's got to have one 'cause there the best thing to use.

I always have my engines built. I may pay a tad more than a crate engine but it's cheaper in the long run.

 

learn something new everyday send them back packed with shit

 

thanks for several more reasons not to use KB pistons. btw, my results have been the same .