Is this a common issue with custom pistons? I ordered a set of custom Diamond Racing pistons and thought I did a decent job.

So I am putting my shortblock together yesterday and get to the pistons...wrist pin will not fit it...hmmm...so I freeze the wrist pin and get the piston toasty...still no fit...hmmm. I mess with it for about an 1/2 an hour, get a set of mics out to measure...

Paperwork says .927 wrist pin diameter...my wrist pin in .928.

Ok, something was machined wrong with the pistons, I can deal with that, stuff happens.

So I call Diamond and ask them why I cannot get the wrist pin in...well ends up that I needed to have the pistons fitted for the wrist pins . I have never heard of this...off the shelf pieces do not require this I am told. Then I ask why my wrist pins are .928 and I am told I was sent the larger? wrist pins.

So I told the guy I was never informed of fitting the wrist pins and he told me the guy that sold the pistons to me was let go because of such stuff.

So I ask the guy what can I do to get this fixed...$3.50 a piston...but I have to pay shipping though.

That is where I draw the line...he admits that they let someone go because of crap like this and here I am with some pistons that I cannot use because of such crap?

Anyways...just felt like ranting....

 

Did you buy the pins WITH the pistons from Diamond? If so they should have come assembled. When you are talking about .0008 total clearance on a pin fit, you should be buying things as a unit. You also can't check them with .001 reading mics.

IF you did purchase the pistons and pins as a unit, Diamond needs to fix that for you. If you just purchased pistons and pins from them and didn't specify they needed to go together, there was a communication problem and they should still fit the pins, but expect to pay the upcharge if you didn't pay it initially. Some folks do their own pin fitting, and buy "unfitted" pistons, but you need the correct honing equipment and especially VERY good measuring equipment to do it right.

Don't try to shrink fit the pins into the pistons: they need to move in the piston and have the correct clearance within a couple of .0001s (1/10th or 2/10th of a thousandth).

My suggestion:

Discuss the problem with a supervisor @ Diamond. With everyone on the same page, you should be able to resolve the problem.

FWIW, we have the capability to fit pins to pistons, but I certainly wouldn't do it for $3.50/ piston ($28.00 total). It would be multiples of that price.

No offense, but if you haven't built engines with custom pistons or non-fitted pistons before, there is a learning curve. Knowledge is power, both mechanically (engine) and biologically (people).

My $.02

 

I bought the pistons and wrist pins from them at the same time as a unit...or I thought so..

I spoke with a higher up and he told me that he would cover shipping because it should have been caught before the pistons were shipped to me.

That is all I wanted...

I am sorta in a hurry to get this shortblock together being I travel soon, so my local performance shop will do it for $4.00 a piston with very little turnaround time.

At least Diamond offered to cover the shipping...just I spoke with a guy that did not see my point.

Thanks for the reply.

 

Ah, communication between people...the Number ONE problem in civilization.

You could also edit your "rant". A number of manufacturers lurk around forums like these. If they see a negative post which hasn't been updated when the problem was solved, they still feel bad...or mad. Remember many folks may read your original post and not bother to read the rest of the posts, and get a mistaken idea about the supplier. I like fixing the original post.

IMO, unless a supplier has a track record of poor performance, bad parts, lousy service, etc., I think they deserve a fair shake. If a supplier gets into a p***ing contest with a customer on a forum nobody wins. Either one or more often both look bad.

My $.02

 

Yeah learning curve for sure.....

Make sure you use a pin that will work with the rod as well.... It's always good to check the small end of the rod as well to make sure all the clearances are good to go there. A .928 pin with a .927 piston and rod doesn't work well, it's easier to get a .927 pin than make both the piston and rod bigger.

Bret

 

Yes, but I had to make a couple of calls to get something done...which is why I was annoyed about it in the first place.

I have qualms about building my own stuff. I take pride in my stuff when it works and when it does not...what can I learn from it

If manufacturers do read posts...good, maybe they might not just blow off guys that do it themselves off because I don't have a shop at my disposal.

I dropped the stuff off at my local performance shop....it will cost me $4.00 a piston to be honed to spec., not a bad price imo.

 

Remember we are lucky to have these pieces today as cheap as they are...

If a motor was simple and everything went right that would be a miracle in itself. Lots of times you have to fix and adjust things to get them right, the more motors you build the more of these things you will run into. It's actually one of the things that makes doing engines interesting, is the problem solving to get the motors done correctly.

bret

 

$32 represents a lot less than an hour of shop time. What clearance did they say they were going to use? .0006? .0008? or ?? I'd ask them to explain how they measure the piston pin bore and the pin itself. If they don't talk in "tenths" or .0001 inch with bore gaging reading in "half-tenths" or .000050 ("fifty- millionths") increments, you might not want to trust your expensive custom pistons to them.

Oh yes, ask them what temp. they will have the parts when they measure them. Aluminum expands about twice as fast as steel with temp. The standard is 68-72* F. Honing and handling the parts warms them quickly. FWIW the difference between 68F and body temp expands that pin bore about .00025 and the pin about .0001. If you are trying to hold the pin fit to say .0008-.0010 (.0002 tolerance), the thermal growth will mess up your measurements.

You really should match an individual pin to an individual piston. Remember that the tightest sliding fits and the tightest tolerances in an engine are the pin to pin bore in the pistons. Much tighter than bearing fits.

Piston manufacturers know all about this, but I have found few engine shops whose operators understand these things, even if the shop has the good equipment, and actually calibrates it before use.

I'm in the precision machining/grinding/honing business. What I see in engine shops sometimes scares the stuff out of me. I'm not saying you'll get a bad job for $32, but quality work costs money because it costs time.

Good luck to you.


"You don't always get what you pay for, but you rarely get what you don't pay for."

"Caveat emptor"

 

Diamond racing wanted $3.50 a piece does it for many people.

Diamond racing told me .0005" clearance.

I know my local guy said half a tenth and he wanted all my wrist pins.

Thanks for your input and I trust my local engine guy.

Never knew the tolerances for the wrist pins were so tight.

Learning more everyday.

 

Another hold up...when I ordered the pistons, I told them piston ring sizing of 1/16", then below that, wrote STD for the compression ring and STD for the oil control ring.

They sent me a 1/16" top, 1/16" second and 3/16" oil control...which would be fine if the had not made the piston 1/16" top, 1/16" second and 3.0 mm oil control ring.

I having a challenge finding a 3.0 mm oil control ring now for a 4.030" bore.

I went with Diamond because I "heard" they were a good piston...shoud have just stayed with Ross.....

Felt like bioching a little...

 

I am not saying who is "wrong" here, I don't have all the facts. And most likely no one is "wrong" but there was just poor communication. However, a point I have often made here to neophyte engine builders may be instructive. I advise buying the entire rotating assy. including crank, rods, pistons, rings, bearings, balancing, and pin fit from the same outfit. Write everything down, including the name and date/time of the person you spoke with. Keep a copy of your written order. And so on. Buying parts piecemeal is an invitation to this sort of problem. These things can happen to anyone, and as has been stated, there is a learning curve.

Rich

 

There is no learning curve when it clearly states what I wanted.

I built enough motors to know when a company drops the ball. They tell me the guy that took my order is no longer with the company because of issues such as I am having. That is there problem, in the mean time, I have pistons that I consider a step above crap.

I ordered by pistons, wrist pins, and the rings from them. I have my custom piston order form where it clearly states what I wanted...the reason I ordered this stuff from them was to avoid the issue I am having...

I called Thursday about this...know what I am told...to call back "Tuesday"...hmmm, another weekend that I cannot build my motor...what the guy should had said was let me next day you the right stuff because of the mess up.

When I mess up...I own up to it.

 

Pin fit is a separate operation and needs to be ordered separately. Diamond's order form, as other custom piston manufacturer's, clearly has a line item for pin fit as can be seen here: http://www.diamondracing.net/orderform.pdf That's why I suggested people put their order in writing. Makes it easy to see who made the error. Helps prevent neophyte or expert mistakes. Anyone can make one.

This post is for the information of those reading the thread who don't already know. If you already know, great! I have no idea who made the mistake referred to in this thread and I don't care.

Rich