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  #31 (permalink)  
Old 04-07-2015, 12:36 PM
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Every time I've done that it was from too much boost and not enough ring gap. The dents are from the pieces of piston and ring getting squished.

Kevin

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Old 04-07-2015, 10:26 PM
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Again, when those pieces made it out of the chamber, they were probably smashed here and there with the valves. Not to add fuel to the fire but your more than likely going to need a valve job. If the heads are nothing to write home about it, you may be better off finding another set to put the money in.

I don't know if you mentioned what you were putting it in but a junkyard LS motor may be a much better option. I'm a Ford guy but those motors work really well.
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  #33 (permalink)  
Old 04-12-2015, 03:40 PM
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UPDATE: Removed the damaged pistons today. Going to see about purchasing another set. I am trying to identify what pistons these are, so I'll know what pistons I must buy. I know the piston has to match the rod length, which I don't know that either. What is a good way of determining the rod length? A ruler?? LOL. The rods don't look damaged at all so I shouldn't have to replace those.

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  #34 (permalink)  
Old 04-12-2015, 03:44 PM
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Quote:
Originally Posted by Rick90lx View Post
Again, when those pieces made it out of the chamber, they were probably smashed here and there with the valves. Not to add fuel to the fire but your more than likely going to need a valve job. If the heads are nothing to write home about it, you may be better off finding another set to put the money in.

I don't know if you mentioned what you were putting it in but a junkyard LS motor may be a much better option. I'm a Ford guy but those motors work really well.
I swear to you' an LS swap doesn't look too bad right now. It's just that darn wiring that gets me! I tried to do an LT swap on a 91 Camaro I had once. The wiring gave me such a headache that I sold it all. Price isn't the problem. If I just had someone to do the wiring, I would definitely drop an LM7, LS1, or LQ9 into my Formula.
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Old 04-12-2015, 03:48 PM
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. Expensive CP/Carillo forged pistons... over $100 each...

http://www.summitracing.com/parts/cnn-s1303/overview



. Carillo rods and forged crank, also?
.
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  #36 (permalink)  
Old 04-12-2015, 04:12 PM
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The rods didn't have any markings on them that I can see. I don't know about the crank either. But $100 each definitely isn't going to happen. I'm replacing the full set with flat top or dished pistons. Hyper pistons probably since I've read that forged pistons aren't necessary for NA engines under 500hp. I've never dealt with pistons before so this is all new to me.

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Old 04-12-2015, 04:27 PM
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. Might not be the right pistons... dome height says lots higher... unless it's been cut... is compression height correct?


. Compression height is center of piston pin to top of main part of piston... gives a hint of rod length...
.
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Old 04-12-2015, 07:14 PM
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Quote:
Originally Posted by BuzzLOL View Post
. Might not be the right pistons... dome height says lots higher... unless it's been cut... is compression height correct?


. Compression height is center of piston pin to top of main part of piston... gives a hint of rod length...
.
One of the previous replies said that they looked to be 7cc dome pistons so that's what I've gone with. I've never dealt with pistons before. I plan to run 64cc aluminum heads and want 9.5 or 10.0 compression at a MAXIMUM. So dome pistons are off the list.
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Old 04-12-2015, 07:18 PM
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. The #1303 pistons at the link I gave say .450" dome... which is almost a 1/2" high... maybe somebody got them used and had them cut down... but didn't put enough ring gap on them... or they give a choice of dome size at same part number...
.
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  #40 (permalink)  
Old 04-12-2015, 08:50 PM
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Looks like a 5.7 rod from here.
Calipers are good enough. Your choices are 5.56", 5.7" or 6". Measure from the parting line on the cap to the center of the pin. I'm guessing 5.7 here cause the 5.56 doesn't get into the oil ring and the 5.7 will just touch it and the 6 will be half way into the expander of the oil ring requiring a support rail.
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  #41 (permalink)  
Old 04-12-2015, 10:20 PM
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You need to take the mess to a machine shop to have it check - rods, block and crank. They'll measure your rods, check your bores, measure your crank and check to see if it needs a line bore for free - possibly, but cheap at least. Personally, I would not put that back together without getting the rods and crank checked at minimum.

Also, if you are running 64cc heads and pop up pistons, then you compression will be higher than 9.5:1 if the quench is acceptable - you need to rethink your piston purchase. What are you doing with the cam?
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  #42 (permalink)  
Old 04-12-2015, 11:03 PM
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Quote:
Originally Posted by BuzzLOL View Post
. Expensive CP/Carillo forged pistons... over $100 each...

http://www.summitracing.com/parts/cnn-s1303/overview

. Carillo rods and forged crank, also?
.
You need to put your glasses on Buzz, or get a bigger monitor LOL

Those are certainly NOT CP forged pistons,...... it is obvious by looking that they are just cheap cast pistons, could be plain old cast $10 each cheapy's , or could be a claimer hypereutectic....but they are NOT forged, there are casting lines everywhere on them, casting numbers, cast waffled surface in the side reliefs, cast mark in the center on the dome, etc.

Looks like they are probably a 5.7" rod piston, but measure center to center on the rod bores to be sure, choices would be 5.565", 5.70", 5.850, and 6.00"...roughly an 1/8" difference in each length so a good eye can do it with a machinist steel ruler or even a clearly marked plastic ruler....even easier with a pair of calipers.

With a 64cc head you will definitely need a dished piston for pump gas in a 383.

At the very least you will want to have the crank crack checked(magnafluxed). I wouldn't expect it to be hurt, but it has to be checked to be safe, as a crack here will be invisible to the naked eye but catastrophic when it causes failure.

The rods with the broken pistons should also be checked for straightness, to make sure one didn't get slightly bent when it was mashing up those big chunks of piston.

If you are going to try to go over 450HP when you rebuild this, a forged piston is good insurance.
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  #43 (permalink)  
Old 04-13-2015, 10:25 AM
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Quote:
Originally Posted by ericnova72 View Post
You need to put your glasses on Buzz, or get a bigger monitor LOL Those are certainly NOT CP forged pistons,...

. Didn't even now Carillo or CP offered pistons... too rich for my hobby projects... just put the part number off OP's pistons into search and it popped up... interesting the part number was the same?... kinda like China copying something and not knowing what the writing says... but then the problems popped up with all that...
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Old 04-13-2015, 12:01 PM
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if you're serious about salvaging this mess i'd take it straight to a competent shop and have it all looked at. the amount it costs to check and fix the rods you'd be ahead to buy a new set.

the piston damage looks like a butted top compression ring from improper end gap during assembly. perhaps those pistons are Hypereutectic, if so the top compression ring would require a larger end gap than the 2nd compression ring. for instance, when using a KB hyper piston you can download a master sheet that provides a simple equation that will calculate necessary ring end gap. some of the determining factors would be compression ratio and intended usage. the top of a hyper piston apparently takes on more heat and sort of reflects it back into the combustion chamber, the effect of this is a greater loss in ring gap than that experienced by the 2nd comp. ring. (or something to that effect). the ring gap factor should be rechecked for every piston in this engine as i would suspect them all to be wrong.

you can run a carburetor on the LS engine. there's an intake/ignition box kit that will control the spark and provide you with a carb intake, they're a package deal.

like these:
LS Carb Intake Kit Edelbrock RPM Intake MSD 6012 Ignition Quickfuel 750 Carb | eBay

Holley 300-132K, Holley LS Single Plane Intake Manifolds Carb & EFI | Holley

just be sure you have the correct reluctor on the engine. up till 2005 they're 24 tooth, 2006 and later they're 58 i believe, it'd be easy to figure that out.

i dont know what you've got in this thing already but it could turn out to be a small money pit.
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  #45 (permalink)  
Old 04-13-2015, 02:25 PM
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Ben S.....the KB Signature Series Hypereutectic pistons have that special larger top ring gap requirement because KB moved the ring pack higher on the piston, making the top ring closer to the top of the piston, (where heat is higher causing the ring to expand more from heat)......it is not because of the hyper material.

Most other company's hypers, like Speed-Pro/Sealed Power, Summit brand, Federal Mogul, Mahle, UEM/KB "claimer", etc have the rings in a more or less "standard" location and have no special ring gap needs, other than allowances for nitrous or forced induction or circle track/endurance race use getting a larger gap.

I still believe that the ring end gap "was" probably perfectly fine on this engine....had it never been run on pump gas, with the too high compression for pump gas causing detonation, which turns into runaway heat in the cylinder/combustion chamber.....and that is what caused the ring gap to close up and break the piston, as those pistons are just an ordinary cast or hyper, they are not KB Signature's with the high top ring placement.

I've seen it many times before....the result of uninformed home "engine builder" parts combination, with no real math or volume calculations done for the compression ratio, just "estimates", or "so-and-so said" or outright guessing on the compression ratio.

That's my educated reasoning on what the OP is looking at on his engine stand.
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