what's acceptable for wrist pin clearance on a floating

Posted By: brads70

what's acceptable for wrist pin clearance on a floating - 10/31/11 01:18 AM

Hi all!

I just bought a 451" stroker kit and when I measured everything up I got .0018" on one rod and the rest were around .0015" The pin rocks in the rod. Sure doesn't give me a warm fuzzy feeling? I'd me more comfortable with .0005" to .0008" max? That and the grinding on the sides to " balance" the rods? Some are ground right into the shoulder on the rod bolt. My good buddy that builds stock car engines for a living looked at it and just shook him head. This is gonna be a street engine with a hyd roller cam.

Posted By: JonC

Re: what's acceptable for wrist pin clearance on a floating - 10/31/11 01:21 AM

I'm no expert for sure, but I don't see a really good place to grind for balance on those rods. That's probably the best spot. But I think I would take a little off both sides and not a lot on one side.

Posted By: RapidRobert

Re: what's acceptable for wrist pin clearance on a floating - 10/31/11 01:25 AM

No good. Call em up & request a return authorization.

Posted By: brads70

Re: what's acceptable for wrist pin clearance on a floating - 10/31/11 01:47 AM

Ya that's the plan, mailing them back tomorrow.

I gotta eat the postage , but better that than a new set of rods.
Thanks all for the replies!

Posted By: RapidRobert

Re: what's acceptable for wrist pin clearance on a floating - 10/31/11 06:37 AM

Brad who was the source of those rods? I'm in the market for some 7.1's and dont wanna to get burnt

Posted By: Cab_Burge

Re: what's acceptable for wrist pin clearance on a floating - 10/31/11 07:18 AM

The needed (proper to live) wrist pin clearances will vary depending on the application, that being said I don't know any machine shop or racers that use .0015 wrist pin clearances to the pistons or rods

I would much rather see .0008 to .0012 than .0005

I have seen wrist pins galled up due to to little clearances ,never saw a wrist pin galled up due to excessive clearances, bent yes, but not galled up

When it comes to clearances in a Hi Po motor a little bit looser is usually way better than a tiny bit to tight

Posted By: moparniac

Re: what's acceptable for wrist pin clearance on a floating - 10/31/11 10:26 AM

Quote:

Ya that's the plan, mailing them back tomorrow. I gotta eat the postage , but better that than a new set of rods.
Thanks all for the replies!

Well that's good they are gonna take them back! Eating postage in the end would be much cheaper i would presume! Great catch and atleast they are making it right!

Posted By: brads70

Re: what's acceptable for wrist pin clearance on a floating - 10/31/11 12:16 PM

Quote:

Brad who was the source of those rods? I'm in the market for some 7.1's and dont wanna to get burnt

I don't want to " throw them under the bus" as they said they will replace them. I figure everyone screws up now and then. The difference is admiting it and making it right. That seperates the men from the boys!

Off to the post office today....

Posted By: CompWedgeEngines

Re: what's acceptable for wrist pin clearance on a floating - 10/31/11 02:16 PM

Off to the post office today....

There is a big difference in " screwing up every now and then" and just plain horrible workmanship. They performed the latter on that job. Not only that, but if they had a clue, they would NEVER balance a rod like that, putting hundreds of stress risers right down the side of a bolt hole on a connecting rod. Thats work of a 10 year old. They simply didnt care, hoped you wouldnt notice ( or knpow the difference) or just hired a 10 year old in their shop. Ok, so they dont know how to balance, THEN they decide to send rod pins out with almost DOUBLE the accepted and needed clearance? Why you would protect them I dont know, but thats your call. I'd get my money back and deal with someone who actually knows what they are doing, unless of course, " best price" was what this purchase was about.

Good luck on the next set.

Posted By: brads70

Re: what's acceptable for wrist pin clearance on a floating - 11/29/11 01:54 AM

Well I got my new replacement rods. Muscle Motors came through in the end!

I'll fit the pins myself as they don't quite fit the new rods. I weighted them and they are all within 1.5 grams , so I have no idea why the ground the sides like that?

Posted By: mr_340

Re: what's acceptable for wrist pin clearance on a floating - 11/29/11 03:00 AM

I wouldn't grind on the sides of the caps like that to balance them. My machinist is balancing a set of Manley I-beam rods for me and I ran a simplified Hemi rod under tension. I found the cap area at the parting line and 90 degrees to that on the center of the cap to have high stress areas. I found similar results in a technical paper online on rod stresses.

Attached picture 6941088-HemiRodunderTension.png

Attached picture 6941088-HemiRodunderTension.png

Posted By: Rick_Ehrenberg

Re: what's acceptable for wrist pin clearance on a floating - 11/29/11 04:27 AM

FSMs always called for "light thumb push" at room temp., and that's always worked for me!

Rick

Posted By: BeEtLeJuIcE !

Re: what's acceptable for wrist pin clearance on a floating - 11/29/11 05:22 AM

Quote:

I would much rather see .0008 to .0012 than .0005 I have seen wrist pins galled up due to to little clearances ,never saw a wrist pin galled up due to excessive clearances, bent yes, but not galled up .....

There was a post(with pics

) here 4 or 5 months ago with the bushing BEAT OUT of the small end ....probably due to Xcess clearance.

I have put together a couple of floaters ... NOTHING looser than .0009.

Posted By: lahatte

Re: what's acceptable for wrist pin clearance on a floating - 11/29/11 05:29 AM

Rick, is that thumb push with oil or without?

Posted By: Performance Only

Re: what's acceptable for wrist pin clearance on a floating - 11/29/11 06:49 AM

Quote:

Well I got my new replacement rods. Muscle Motors came through in the end! I'll fit the pins myself as they don't quite fit the new rods. I weighted them and they are all within 1.5 grams , so I have no idea why the ground the sides like that?

glad to hear you got that taken care of.

how does the weight of the new rods compare to the ones you sent back?

Posted By: brads70

Re: what's acceptable for wrist pin clearance on a floating - 11/29/11 10:00 PM

They were within 2 grams of the old ones. And they are all within/less than 2 grams now , so thats good enough for me, no need to do anything except fit the wrist pins IMO....and check the big end for size.

Posted By: lilcuda

Re: what's acceptable for wrist pin clearance on a floating - 11/29/11 10:24 PM

Quote:

Well I got my new replacement rods. Muscle Motors came through in the end! I'll fit the pins myself as they don't quite fit the new rods. I weighted them and they are all within 1.5 grams , so I have no idea why the ground the sides like that?

I wouldn't let MM work on my lawnmower engine. Long story...

Posted By: lilcuda

Re: what's acceptable for wrist pin clearance on a floating - 11/29/11 10:28 PM

Quote:

Rick, is that thumb push with oil or without?

And who's thumb are we talking about? That kind of "spec" is great for a backyard guy with stock parts, but in a performance application you have to measure the clearance with the proper equipment.

Posted By: BeEtLeJuIcE !

Re: what's acceptable for wrist pin clearance on a floating - 11/30/11 01:33 AM

Quote:

Quote:

Rick, is that thumb push with oil or without?

And who's thumb are we talking about? That kind of "spec" is great for a backyard guy with stock parts, but in a performance application you have to measure the clearance with the proper equipment.

So right ...