Hi all. I have finally saved up some cash to complete the rotating assembly in the 406 sbc, but I came across an issue when I went to the part store to get some pistons. The guy at the speedshop was concerned about piston-to-wall clearance issues depending on how the machinist oversized the block and what grain of honer was used. He mentioned that cast, hypereutectic, and forged pistons all have different clearance specs, and putting a hypereutectic into a bore milled for stock pistons might cause bind-up. Also, the coarseness of the honing will determine whether moly rings are to be used or not. Here is where my problem gets worse: the block was machined a year ago, and naturally the machinist can't remember my exact block and what he did to it. I DO, however, recall telling him I planned on using hypereutectic pistons in there (he actually asked) but I don't recall any talk about rings. Now, what might you suggest I do to go about determining what pistons/rings to put into my bore? I don't really feel like paying a machinist again, heh. Is there some way of measuring the bores with a vernier caliper or something and matching up the result to the desired piston? Also, is there a visible difference in coarse grain honing and fine grain honing?

I most certainly would appreciate any advice or help offered, as the parts man obviously isn't too keen on selling me pistons blindly.

Thanks a ton in advance,
BW

Are you sure the cylinders were finished honed? That is usually done with the pistons in hand.
You can have the bores measured for a small amount of money. That will at least tell you what size they are now.

Oops, I neglected to mention the 30 oversize. Very little info is on my receipt except for the oversize, the hot tank, acid flux, and the cam bearing/freeze plug install.

At any rate, I take it my only real option is to go back to the machinist and have him do a measure up? Man, I hope it doesn't cost a load, the parts alone are becoming rather costly. http://www.camaros.net/forum/confused.gif

[This message has been edited by BreathWeapon (edited 05-29-2002).]

Buy the pistons of choice, and take them back to the machine shop with the block. Have them custom hone each cylinder for each piston, and make sure to stamp them to keep them straight.Also, the hone pattern is different, depending on the choice of rings. Tell the machine shop the kind you are going to install. Chrome-moly, etc.

Like Toby said most shops won't finish hone a block without the pistons in front of them to mike. Hopefully the machinest left them undersize otherwise you are stuck. Most of the time the machinest will put what the finish hone type was on the bill take a look.

I was hoping to be so lucky, but the bill just says ".30 oversize" and lists the various cleanup proceedures. I think I'll take the block back to the machine shop and see if they can measure the bores to determine what step to take next. Thanks for the advice.