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Discussion Starter · #1 ·
I am building a 408W engine using a all forged Scat stroker kit.

The kit is using forged aluminium pistons (Probe SRS).

I will be using about two 10LB bottles of Nitrous a year (150 shot).

The engine will be used mainly for the street and occasionally some strip action.

The engine is about to be bored/honed.

What piston to cylinder wall clearance should I run.


Regards
Harry
 

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I've got an SRS piston for my 408 and the p/b clearance is .003. I'm pretty sure that's what Probe recommended at a minimum.

I'd email them and be sure though.
 

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I'd shoot for about .004-.005. I know from very recent experience that they'll rattle when cold if you go to .0055...
 

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All the ones I've done are .005 minimum. Used to run .012" on a sprint car...yes it rattled and yes it ran great.

.004 is about right for a starting point with most forged pistons. .005 is what I'm at but I use Mahle pistons with really short skirts. The KB hyperutectics in my Mustang are .015" LOL. Runs fine. .015" is a result of one too many burned pistons and not having the money/time to have the block bored. Been loose like that for....about 2 years now, beating the crap out of it every sunday afternoon, shifting at 6600 crossing the line at 7000. I always cringe when he burns out at 7000+, figuring that a skirt or 2 will break off.
 

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.005 is good, looser and they will rattle for a minute, no biggie. I have run some stuff really loose, motor loved it
 

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Hi Guys,

This post has got me a little worried. I am building a 393 Windsor to go in my Cobra replica which will be used for street & occassional track days & will be running Probe SRS forged pistons in +30" bores with Mahle moly rings. I end gapped the rings as per the Mahle instructions using a ring grinder to 0.017" top ring & 0.022" second ring. If im reading the posts above correctly I have my end gaps to tight??

Any advise appreciated



Martyn
 

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Discussion Starter · #8 ·
@martynUK This topic is about piston to wall clearance, not the ring end gap.



Thanks guys for the answers.

I will set it to 0.004" (got a mail from Probe aswell, with the same recommendations)


Harry
 

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On 2006-11-26 09:30, martynUK wrote:
Hi Guys,

This post has got me a little worried. I am building a 393 Windsor to go in my Cobra replica which will be used for street & occassional track days & will be running Probe SRS forged pistons in +30" bores with Mahle moly rings. I end gapped the rings as per the Mahle instructions using a ring grinder to 0.017" top ring & 0.022" second ring. If im reading the posts above correctly I have my end gaps to tight??

Any advise appreciated



Martyn
Yep, piston to wall not ring end gap =D

Also, .017 and .022 are much larger than .005 (2-4x), if anything you'd have been too large! =D

Cris
 
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