Found wrong size pistons in my blown engine during disassembly!

[DXBLouie]

Reference to my previous thread: "http://forums.viperclub.org/srt10-srt10-coupe-discussions/623087-snapped-connecting-rod.html"

i finally sourced all the parts needed to rebuild me a new engine bottoms up, took the blown engine out and disassembled it.

According to the original builder, The car has ported heads, larger camshaft, lower compression pistons, stock crank and rods.
the crankshaft was balanced by Nelson Comp.

Now when i removed the heads to inspect the carnage, i was surprised to see a good 1.5mm gap between the piston and the cylinder walls!
the overall diameter difference was 3mm.

sure enough, the CP Pistons were 3913R (3.913" = 99.4mm) while the bore was a stock 102.4mm confirming the 3mm difference.

what the hell gives?

the car was bought as is with a paxton supercharger tuned to put down ~900rwhp on pumpgas.

i felt a bit iffy when the builder mentioned the engine has stock rods.. but didn't expect this about the pistons.

any comments?

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[Martin]

I'm surprised you didn't lose the rings a long time ago or scuff the heck out of the cylinders as those pistons bounced around in the cylinders. It wouldn't surprise me if you lost the rod because the cylinder wasn't travelling straight up and down like it is supposed to do - 3mm of lateral travel can cause all kinds of problems at high RPMs.

 

[DXBLouie]

who said it hasn't?
the cylinder walls looked clean when we looked at them from the bottom during the initial inspection, but i can clearly see signs where the pistons were digging into the walls close to TDC and most of them have jagged edges.

basically the damage went up from the initial assessment of snapped connecting rod, damaged oil galley in the block to:

Pistons: total loss
Connecting rods: most are busted
Block: total loss
Heads: mostly total loss
list goes on

also found the oil return line from the supercharger going nowhere..
it's a straight pipe to the bottom of the car.. which explains the 2L oil consumption per 600miles which the engine builder said that sounds about right

 

[Tabs1]

You must also have been burning tons of oil.

 

[ROCKET62]

Guess putting in the wrong size pistons is one way to achieve lower compression . Sorry to hear about your troubles. Good luck with the rebuild.

 

[Tabs1]

Was this a professional shop? Wrong sized pistons, 2L of oil per 600 miles, oil drain to bottom of car, sounds like a personal garage build after a few too many beers.

 

[Martin]

Isn't Dubai one of those countries where they jail you for life for crimes like that? I know you can't even make out with your girlfriend on the beach without getting executed (or something like that)

 

[DXBLouie]

Was this a professional shop? Wrong sized pistons, 2L of oil per 600 miles, oil drain to bottom of car, sounds like a personal garage build after a few too many beers.

it actually was built by a highly professional shop (or so i thought)..
it's one of the most sought after names too... i'm confused to be honest.

Martin: it aint that bad down here.. we have liquor stores, bars, world class nightclubs, etc
Having sex on the beach will get you fined and locked up for a few months..
they're not big on PDI here
it's basically a PG13 environment, with R rated areas everywhere, always accessible to westerners and non-muslims.
i like it.. they live and let live (unlike other uptight places like Saudi, etc)

look it up

 

[SquadX]

ok, I am confused, I thought you could get away with a 5mm gap because that was in spec. Are you saying the gap was to tight because it was scratching the cylinder walls or to loose? I just had my engine rebuilt (swapped pistons for forge) and I am sitting at 5mm gap which is inspec.

 

[Greg Good Cylinder Heads]

Reference to my previous thread: "http://forums.viperclub.org/srt10-srt10-coupe-discussions/623087-snapped-connecting-rod.html"

i finally sourced all the parts needed to rebuild me a new engine bottoms up, took the blown engine out and disassembled it.

According to the original builder, The car has ported heads, larger camshaft, lower compression pistons, stock crank and rods.
the crankshaft was balanced by Nelson Comp.

Now when i removed the heads to inspect the carnage, i was surprised to see a good 1.5mm gap between the piston and the cylinder walls!
the overall diameter difference was 3mm.

sure enough, the CP Pistons were 3913R (3.913" = 99.4mm) while the bore was a stock 102.4mm confirming the 3mm difference.

what the hell gives?

the car was bought as is with a paxton supercharger tuned to put down ~900rwhp on pumpgas.

i felt a bit iffy when the builder mentioned the engine has stock rods.. but didn't expect this about the pistons.

any comments?

It is typical for the top of a power adder piston to be ~.050" - .055" smaller than the bore.

 

[Martin]

it Martin: it aint that bad down here.. we have liquor stores, bars, world class nightclubs, etc
Having sex on the beach will get you fined and locked up for a few months..
they're not big on PDI here
it's basically a PG13 environment, with R rated areas everywhere, always accessible to westerners and non-muslims.
i like it.. they live and let live (unlike other uptight places like Saudi, etc)

look it up

I know - I have friends who went out there on contract and never came back. I just have to give them a hard tiime because I'm a little jealous.

 

[99 R/T 10]

If you need a replacement engine:

Message - ViperClub Classifieds

Or if you just want a Block and crank:

Gen III bare block and crankshaft - ViperClub Classifieds

http://www.viperalley.com/classifieds/showproduct.php?product=4475&sort=2&cat=500&page=1

 

[Tabs1]

It is typical for the top of a power adder piston to be ~.050" - .055" smaller than the bore.

So thats about 1.3- 1.4mm

 

[Greg Good Cylinder Heads]

Yes, less than half of what he has now.

I'm curious to know what the piston skirt to bore clearance is.

 

[DXBLouie]

i'm emailing the engine builder to see his take on the matter...

 

[Viper Specialty]

First of all, 3913R is the forging number, it has nothing to do with the actual diameter of the pistons.

In order to know what really happened here, we would need to see the original piston spec sheet, as well as the block specs when it was assembled. It is possible that the pistons started to wear and rock, which would increase the wear rates at the top and bottom of the pistons, and it may be confusing the numbers here. Also, chances are, if CP spec'd the pistons themselves, they made the skirts too short and the clearances larger than needed right off the bat- adding to the problem.

If you get into a bind, let me know... we can build and ship you a short-block, the RIGHT way.

 

[DXBLouie]

Dan, the car has 5k miles so far.
the engine has 2k miles since it's been built!

you can see scuffing on both sides of each cylinder wall, where the pistons were tilting during their movement due to their size mismatch.

4 pistons have cracks exactly where the scuffs are.
some are missing pieces
one of them eventually snapped a connecting rod which i believe happened after it got stuck on its way down..

the pistons are CP 3913R.. can you pull up the specs of these by that number?

the engine builder now claims that my pictures "seem to show the piston rocked to one side which exposed the ring which is normal even for a stock engine"
i think that's BS.. especially on a supercharged engine that's meant to put down 900rwhp (which it did.. till one pistons started smacking into the sparkplugs, and everything went downhill quickly thereafter.)

 

[Viper Specialty]

Dan, the car has 5k miles so far.
the engine has 2k miles since it's been built!

you can see scuffing on both sides of each cylinder wall, where the pistons were tilting during their movement due to their size mismatch.

4 pistons have cracks exactly where the scuffs are.
some are missing pieces
one of them eventually snapped a connecting rod which i believe happened after it got stuck on its way down..

the pistons are CP 3913R.. can you pull up the specs of these by that number?

the engine builder now claims that my pictures "seem to show the piston rocked to one side which exposed the ring which is normal even for a stock engine"
i think that's BS.. especially on a supercharged engine that's meant to put down 900rwhp (which it did.. till one pistons started smacking into the sparkplugs, and everything went downhill quickly thereafter.)

-Chances are that the engine failed from a combination of overpowering the connecting rods, and excessive clearances, however they may have been caused- and it certainly looks like cylinder wall wash-down and/or incorrect prep may have been a factor as well.

-You most certainly can rock a piston to expose part of the top ring when the engine is cold, especially if it is a forced induction engine with forged pistons. Forced induction engines run larger clearance above the rings to deal with the extra heat, and forged pistons as a whole run larger clearances due to thermal expansion even at the skirt. If the pistons were really undersized 3mm, I doubt the engine would have made it 10 miles before losing peices of the skirt or rings... not to mention is would have had an insane amount of piston slap noise that would have been impossible to overlook.

-The 9313R is only a blank forging code, it means nothing when finding out how the pistons were made. You need the original spec sheet. [All of our CP Viper pistons are made from a 9313R forging]

-There is NO WAY that engine should have been allowed to make NEAR 900rwhp on stock rods. No way, No how. Your problems likely started from detonation, cylinder wall wash down, and the stock rods. The washdown killed your walls and scuffed your pistons, leading to excessive oil consumption and detonation, though Detonation likley started with the tune. Detonation then cracked your pistons and weakened your rods, and overpowering ended up taking out your connecting rods. Those rods were never intended to handle anything near 900rwhp, especially with heavier pistons attached to them while being pounded by detonation.

 

[plumcrazy]

Who is this engine builder ?

 

[Viper X]

Had something like this happen to me once ..... and as usual, Daniel is correct.

Throw in a lousy tune and a poorly set up fuel system on top of overpowering stock rods and poor piston clearances and this is what you get ..... a very expensive repair.

Be careful who you buy from .....

Dan

 

[DXBLouie]

the engine was built by Heffner Performance.. which is surprising as they're quite a reputable company.

 

[Viper Specialty]

the engine was built by Heffner Performance.. which is surprising as they're quite a reputable company.

There is no way in the world I would expect Heffner to say that build was good for 900whp, though this does further confirm my hunch that the engine was probably assembled with the correct clearances originally... Are you sure there is not some miscommunication or crossed wires somewhere here? How many hands were in the cookie jar on this build? Who did the tuning?

 

[DXBLouie]

i have emails from jason heffner confirming the engine had "ported heads, larger camshaft lower compression pistons, stock crank and rods. The engine would have been marked by Nelson because they balanced it."

we got the car in as is.. it's always been running pig rich btw.. we're talking AFR in the 10s leaning up towards low 11s at high RPM but that's about it.

 

[AZTVR]

There is no way in the world I would expect Heffner to say that build was good for 900whp, though this does further confirm my hunch that the engine was probably assembled with the correct clearances originally... Are you sure there is not some miscommunication or crossed wires somewhere here? How many hands were in the cookie jar on this build? Who did the tuning?

we got the car in as is.. it's always been running pig rich btw.. we're talking AFR in the 10s leaning up towards low 11s at high RPM but that's about it.

I guess the questions still unanswered are: Did you commission the engine build? Was the engine build designed for the power that you were making? i.e., did the builder know exactly what boost was going to be involved, or did he build the engine based on a buyer's lower budget and input on what the usage would be? Who did the tune? If it was too rich, was running it that way part of the problem?

Since the engine builder is one of the most respected, we might not be surprised to find that you are the second owner of the car after it was assembled, and that you are not fully aware of what happened to the engine during the first owner's usage.

 

[DXBLouie]

The car was bought straight from Heffner fully built and supercharged.
Jason confirmed it's tuned for 14PSI boost on 93 octane, and made 900rwhp when dynoed before being sent out here.

 

[Fast Viper]

The car was bought straight from Heffner fully built and supercharged.
Jason confirmed it's tuned for 14PSI boost on 93 octane, and made 900rwhp when dynoed before being sent out here.

Heffners a stand up guy with awesome builds! Is he trying to resolve this with you and is he offering a warranty on this car?

 

[DXBLouie]

no word from Jason about compensation yet as we're still trying to piece together how it failed.

i came here to get some feedback and not to call heffner out on it.

Please feel free to ask for any kind of info and pictures to get to the bottom of it.

 

[DXBLouie]

Well.. still chasing my tail here.
no luck with the builders as they're trying to sell me the spare parts needed for the rebuild now.

i got a new block, crank and heads.. got everything machined and ready
the block is bored by 0.030 over.

i'm on the lookout for a full set of pistons, connecting rods, main bearings, gaskets, etc.

 

[Viper Specialty]

Well.. still chasing my tail here.
no luck with the builders as they're trying to sell me the spare parts needed for the rebuild now.

i got a new block, crank and heads.. got everything machined and ready
the block is bored by 0.030 over.

i'm on the lookout for a full set of pistons, connecting rods, main bearings, gaskets, etc.

Can supply them for you without a problem... just tell me what it is you are looking for.

 

[DXBLouie]

Can supply them for you without a problem... just tell me what it is you are looking for.

I already did
I need pistons, connecting rods, main bearings, gaskets and billet main caps

Please pm me your quote