Speed Pro Hypereutectic piston clearances?
Thread Starter
Burning Brakes
Joined: Sep 2006
Posts: 1,202
Likes: 3
From: MD
Speed Pro Hypereutectic piston clearances?
For the engine builders out there, what piston to cylinder clearance do SpeedPro Hyper pistons in a 350 use? I've looked around the 'net and found minimum clearance specs from .0008" to .0025". What do you guys hone your hyper piston cylinders out to? It's gonna be in a primarily race engine with 11:1 compression.
Safety Car
Joined: May 2006
Posts: 4,290
Likes: 140
From: Salem NH
For the engine builders out there, what piston to cylinder clearance do SpeedPro Hyper pistons in a 350 use? I've looked around the 'net and found minimum clearance specs from .0008" to .0025". What do you guys hone your hyper piston cylinders out to? It's gonna be in a primarily race engine with 11:1 compression.
I just used a set of speed pro hypers in a motor I built for my plow truck.
Standard bore, the pistons were about .003" over, after power honing the bore I think we ended up with like .0010 clearance or something damn close.
-- Joe
Safety Car
Joined: May 2006
Posts: 4,290
Likes: 140
From: Salem NH
We power honed the block on a Ck-10 to about 4.003-4.004ish to clean up some issues with the walls. This made the block "out of spec" for cast pistons, but where the speed pro hypers were about .003" larger than a standard bore cast piston and wanted a tighter clearance, it actually worked out just perfect.
(I would have used cast pistons, but it was cheaper to hone the block and run a hyper than bore it .010" over and run cast!)
I think we ended up with .0010" clearance which was 'just right' according to speed pro. I used the H423NP:
http://www.northernautoparts.com/Pro...tModelId=10713
Motor is about 9:1, and has two purposes. Pushing snow, and pulling a boat. Not sure i'd use hypers in a race motor, and I wasn't overly impressed with the quality but again, it was cheaper than using cast because I didn't have to pay to bore the block.
-- Joe
Thread Starter
Burning Brakes
Joined: Sep 2006
Posts: 1,202
Likes: 3
From: MD
Joe,
That's the same thing that was done to the stroker in my vette. Saves money, and the block has more meat for future rebuilds.
These pistons are goin into a 355 so I have to bore it. Just making sure before I send it out that I get the right specs. Speed-Pro's site says 0.0010" which is really tight (one-thousandth) but I guess I'll run with it.
That's the same thing that was done to the stroker in my vette. Saves money, and the block has more meat for future rebuilds.
These pistons are goin into a 355 so I have to bore it. Just making sure before I send it out that I get the right specs. Speed-Pro's site says 0.0010" which is really tight (one-thousandth) but I guess I'll run with it.
Safety Car
Joined: May 2006
Posts: 4,290
Likes: 140
From: Salem NH
Joe,
That's the same thing that was done to the stroker in my vette. Saves money, and the block has more meat for future rebuilds.
These pistons are goin into a 355 so I have to bore it. Just making sure before I send it out that I get the right specs. Speed-Pro's site says 0.0010" which is really tight (one-thousandth) but I guess I'll run with it.
That's the same thing that was done to the stroker in my vette. Saves money, and the block has more meat for future rebuilds.
These pistons are goin into a 355 so I have to bore it. Just making sure before I send it out that I get the right specs. Speed-Pro's site says 0.0010" which is really tight (one-thousandth) but I guess I'll run with it.
What scares me is when folks bore the block .030" over, then start looking for a piston. heh
-- Joe
Le Mans Master
Joined: Jul 2001
Posts: 8,183
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From: Santa Maria, CA
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Le Mans Master
Joined: Jan 2002
Posts: 9,036
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From: Edmonton AB
If left long enough, the wrist pin boss lets go as a result of cracks that
form when the skirt collapses. Overheating is a common cause of
skirt collapse - even forged pistons are not immune.
.
Advanced
Joined: Jan 2005
Posts: 63
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From: Southgate Mi.
I'm sure glad that I decided to look in over here today!! I've been trying to decide if I should pull my painfully assembled 383 short block apart and have it bored out another .001 over.
After seeing this I'll stick it back in, and take it easy for a while.
I had put it together w/KB hypers, and took them out aftere talking w/Russ Hayes (Speed Pro piston engineer). He'd told me to go ahead and use the .001 piston to cylinder wall clearance. He said with the coating it would be fine.
After seeing this I'll stick it back in, and take it easy for a while.I had put it together w/KB hypers, and took them out aftere talking w/Russ Hayes (Speed Pro piston engineer). He'd told me to go ahead and use the .001 piston to cylinder wall clearance. He said with the coating it would be fine.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Be really careful in the piston to wall. I know the Keith Black hypers have a history of failure when the clearance is set too tight. Those expand an awful lot and need more clearance than you'd normally see.
One member posted he went to his machine shop and was shown baskets of failed KB hypers. P/W was set too tight and the engine died.
Jake
One member posted he went to his machine shop and was shown baskets of failed KB hypers. P/W was set too tight and the engine died.
Jake
Thou and a half for KB hypers is a little safer but still "tight".
Racer
Joined: Nov 2002
Posts: 420
Likes: 0
From: palm harbor fl
hypers in lt1 is about .002 clearance,hypers use tight clearance and they don't expand like forged making them quiet,which is what the factory wants I would not use them in a performance engine ,just my opinion.
