Max piston to wall clearance, TRW Forged 2316

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Baxter61

Baxter61

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I have a .030 over 340 block that needs to be honed and a set of 2316 TRW forged pistons Id like to put in it. Whats the max piston to wall clearance you guys recommend or have run with this type of setup? These are the older pistons and this is a budget build so trying to avoid boring and buying new pistons if possible. Thanks! :burnout:
 
I always say as long as they aint swappin holes they're not too loose. Loose is good up to a point on a performance engine. Just make sure the ring end gap is right and you'll be good. I've even gotten .005 over rings and file fit to worn cylinders. Been some of the best runnin engines ever.
 
I recall a few posts in FABO on this. You need more clearance for forged pistons since they expand more, which is one reason they are best for "race only" applications. You might hear some piston slap in daily driving. If having it honed at a machine shop, leave your pistons with them to check the fit. I have read about shops knurling the skirts to raise the metal slightly to get them tighter, but that may lessen the life. I would only do that on rare and expensive pistons like 273 HiPo.
 
I think at .030 over they wanted .0045" but it's been a while since I've used them. It should be on thier website. Personally, if it's more than .003 over what they recommend it would probably drive me crazy with noise even when warmed up. Also, you want to make sure if they are used that you measure the piston propperly, and measure the bores properly with a dial bore gage or you may find it's a lot larger than you think.
 
Thanks for the replies guys. I measured the pistons and bores out and Im pushing my luck as is. The reason I ask for the max clearance is Im going to be on that end if I hone this thing out, and that hone is gambling that I can even get the walls clean enough and stay within spec. Most of my clearances would be .005 if I installed them as-is right now so Im thinking I have maybe .002 to .003 to play with in honing the walls. I reckon they'll rattle pretty good when cold, maybe even when warm. Thoughts?
 
If you don't hog them out too much you will be ok, forged pistons grow so its not a problem.
 
... shouldn't 030 over pistons measure 4.068
... bore to 4.070 for proper clearance?
 
Baxter61 said:
Thanks for the replies guys. I measured the pistons and bores out and Im pushing my luck as is. The reason I ask for the max clearance is Im going to be on that end if I hone this thing out, and that hone is gambling that I can even get the walls clean enough and stay within spec. Most of my clearances would be .005 if I installed them as-is right now so Im thinking I have maybe .002 to .003 to play with in honing the walls. I reckon they'll rattle pretty good when cold, maybe even when warm. Thoughts?
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If you're really intent on re-using these pistons and keeping the budget down, I recommend dingle ball honing the block and throw in a set of iron rings and call it good. I wouldn't knurl the pistons - it doesn't last.

My friend ran in the high 12's in his Road Runner with a worn-out 383 that he honed and ran with .008" taper in the bores.

FWIW - my 340 has the same pistons you have with .004" clearance and they don't make noise.
 
Im not intent per-se on using them, just trying to use what I got if I can. If need be, I'll sell them and hopefully the next guy can use them. I ran the dingle ball through the block last night and there's still more rust spots than Id like to see. That's why I was going to take it in and see if they'll hone out. I know the right thing to do would be to bore and get new pistons but like I said, just trying to use whats on hand. If I go with these Im going to end up with .007 to .008 and was just curious if that would be safe. I can always spray the motor to heat the pistons up and close that gap if needed! haha
 
If the bores are straight and not tapered (which is really going to cause the power loss) then you can simply roughen the bore with either a dingle ball hone using gear lube for lubricant or the cheapie way I do it: use green scotchbrite on a flex hone, lubricate with WD30, and do it enough to clean up the bore. you're not enlarging the entire bore, you're simply scoring the walls a little so oil can be captured and the new rings can seat. If you really score it up, you went too far.
 
Remember too, forged pistons are cam ground. In other words, they are oval or eliptical when cold. This is why they make more noise when cold. When they warm up, they conform to the bore shape better. I would rough up them cylinders and run hell outta them. I bet it will be a barnstormer. Just remember, if a STD ring mics the ring end gap too big, get some .005" oversize rings and file the gap. It's the ring that seals, not the piston.
 
I would run them,I would not worry about .008 with forged pistons,I have run them at that before and have run cast pistons close to that,just warmed up good before beating them.After all your not going to put that many miles on it the short summers around here lol!.Is this for the green duster?,we could relive some times with that car and a certain road.
 
lead69 said:
I would run them,I would not worry about .008 with forged pistons,I have run them at that before and have run cast pistons close to that,just warmed up good before beating them.After all your not going to put that many miles on it the short summers around here lol!.Is this for the green duster?,we could relive some times with that car and a certain road.
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I agree run it at .008 I wouldn't be concerned with forged pistons, my hyperutectic pistons are close to that and has ran great for over 10 yrs, and actually runs better than it ever has.
 
Adrain, Im not saying this is for the green car, but Im not saying it isnt! I would be very interested to see this "certain road" from the past.

My thoughts have been to just run em, Im just glad I can get some confirmation from this group! haha
 
Baxter61 said:
Adrain, Im not saying this is for the green car, but Im not saying it isnt! I would be very interested to see this "certain road" from the past.
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Get it runnin and you can find out in a few Months!.None of the guys that would join in would remember the car from back in Kims day except for me.
 
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