pistons regularly melt down

[sky1]

Hello all. I am the owner of an Ultima Can Am with an engine of 383 horses
and a supercharger. I am having great troubles with it, since I bought it
(18 months ago). The pistons regularly melt down, causing a car breakage,
whereas the ignition timing and the carburation are well timed. It happends
altough I do not push the engine. I generally drive at a RPM between 2500
and 4000, with slight and rare picks at 6000. The engine comes from
“American Speed”. I am looking for other owners of this type of engine ? I
would like to know if they have encountered such problems ? I want to start
a legal procedure against them and need some back up on other owners having
had equivalent troubles with American Speed engines... I sincerely hope you
can help me. Expecting your helpfull answers...

[Boosted Ls1]

I can't comment on the legal position but if you keep getting melt down then somethings wrong. It could be ignition or fueling or to high compression for the boost you are using. You need to establish what your basic compression is and take it from there.

It's really important to look closely at the pistons as they themselves may be a good indicator of the fault. Until you diagnose the problem you can't say who may be to blame.

[Allen-GTR]

I would look at the boost vs compression ratio first. the spark timing/detonation would take longer for catastophic failure IF you didn't notice it outright. Generally, you would know if you have a detonation problem right away. Based on your comments it sounds like you have been thru this more than once. I would say the engine builer who did the work could tell you by looking at the pistons. Those two failures cause a significantly different result on the pistons/rings...

Allen

>> Edited by Allen-GTR on Friday 6th August 00:06

[Stig]

How on earth did you fit an AS Supercharged engine into a CanAm?

[P15TON]

To be fair to the engine builder, you should take a good look at your installation, which is just as, if not, more likely, to be at fault.

>> Edited by P15TON on Friday 6th August 15:09

[bogbeast]

and only 383 on a supercharger. thats pretty low.. even my poxy engine makes more than that

[bogbeast]

and only 383 on a supercharger. thats pretty low.. even my poxy engine makes more than that

[htsd]

Given that a mild tune SBC can give you 400HP no worries (HSV Commodore GTS, last gen Corvette which are factory engines with emission controls and everything) then I would say that 383 is damn low- unless its an at-the-wheels figure.

Melting pistons sounds like you're leaning out dramatically at higher revs. Did you upgrade the fuel system to handle the higher inlet pressures and the higher fuel demand? If not then your boost will overcome the fuel pressure in the line resulting in low flow, low power and lean running. I'd get it on the dyno with someone who knows what they're doing and a lambda meter. I know I'd get damn sick of rebuilding an engine every time I gave it stick! And given what others have said about AS engines I wouldn't suspect it was their fault...

[andygtt]

suspect 383 is the engine size not the BHP....

I'd personnely suspect the fuel delivery in the car, another owner had this problem here, I'll give him a private nudge to see if he can respond to you.

[gtrclive]

I think he Means 383Ci, remember the guy is in France. He wrights better English than I do French.

This sounds like a Leaning out/ Lack of fuel problem. Do you have a full Screen or Short screen ?

Any Pictures ?

[mkoch1]

Stig said:

How on earth did you fit an AS Supercharged engine into a CanAm?

might be a vortec style blower.

mark

[DUBLE PUMPER]

Ian eccles has had this problem with a 7l ford engine 550ps built specifically for him by a UK man. It has been rebuilt several times and run for ages on a dyno without any problems, put it in the car and a few miles later off it goes again. The top of one of the pistons usually falls off.
It has now been reolved and it would appear to have been a water pump problem. Too much speed causing the pump to cavitate thus reducing the acttual flow substantially. He has changed pulley ratios to bring the pump speed back in line with normality.

[adequatespeed]

Ian's engine builder also said the cam could have been a poor match for the engine leadign to mixture and indiction problems at high speed.

Probably better if Ian posts on this one though as there were many things changed at the same time to fix the problem

[eliot]

Yep, buy yourself a wideband lambda guage or get it onto a rolling road with a Lambda hooked up.

Eliot.

[B1 ECC]

Both Double Pumper and adequatespeed have valid information and if asked what cured the problem I could not give 100% answer.
De-tomaso Panteres suffered from piston breakage which was traced to hotspots on the engine due to over efficient water pumps causing cavitation at higher than designed engine speeds.( I have addressed this problem) The other area was the camshaft, although a Ford Motorsport part, my engine builder was never happy with the cam configuation as in in his opinion it created to much "compression pressure".
After five failures I decided to change the Piston manufactuer, lower the compression ratio slightly, the camshaft configuration I left to my engine builder and the "Crower" computer, with the brief that it must peak at 6500 rpm.
I now have an engine that produces over 500 bhp and has done over 800 track miles.
Question----Have I cured the problem?
Answer------I'll tell you after the next track day!

[davefiddes]

Good to hear you are finally getting to the bottom of your engine problems Ian. It sounds like it's been a bit of a nightmare for you. Sounds like it might have been the combination of the bits you changed that were causing problems rather than just one thing.

Hope it keeps going well!

[sky1]

To mkoch1 , Gtrclive, andygtt, htsd, bogbeast, P15TON,
Stig, Allen-GTR, Boosted Ls1, adequatespeed, eliot, davefiddes, B1 ECC :

Thank you guys for responding so fast and I am sorry for having taken so
long to answer as i have had internet connexion problems recently.... Sorry
about that.... Indeed there was a mistake in the first mail, 383 is the size
of the engine... The translator is not me and is not a car specialist....
Sorry for that also... to answer to all... Yes, an AS supercharged motot
fits into an Ultima Can Amwith few modifications. I will soon send to
whoever whished to get some, few pictures of the inside and outside of the
car, so that you can see by yourselves.
The exact configuration of the engine is:
- 383 ci chevy brutus supercharged 8.0 comp with a carb demon 750 carb
W/76/83 jet
- horse power is 630 HP
with a supercharger of :
- 142 Weiand cam 7QTS
Other technical informations are :
- to get the engine inside, I had a hole done within the rear bonnet, with a
big scoop, in which was moreover installed an air filter.
- and secondely on both side of the rear bonnet, I have had installed two
scoops in order to cool down the engine.
- furthermore, after the first breakage, I have had installed a fuel/air
analyser. This analyser indicated then that the ratio was good. The fuel
pression is also ok and the fuel pomps were bought from Ultima themselves,
for engines going over 600 HP.
- the spark timing is also fine (32 total timing@3000rpm)
- the oil temperature is ok = 70° C on the road
- the fuel filter also comes from Ultima

To give further indications on the breakage, it is always the same pistons
that melts down. So to ensure that the problem was not coming from me or the
timing of the engine, I also had a fuel analysis done by specialised center
for fuel and oil analysis.

The problem with AS is that they don’t assist me in searching the breakdown.
It is important to underline that the engin,e sold to me by AS, was
specifically build for me... without surpercharger, but including the
possibility to install a supercharger. The firstproblem I got with this
engine was that the cylinders glazed... AS thus exchanged this engine...
They had it completly rebuild and at this step, they decided to install the
supercharger.

Since then, they don’t assist in any diagnosis of the new arising
problems... I am tired of rebuilding the engine... It will be the third
time, this time and be sure that the team working on it in France, is a good
one, they are specialized on race tracks (AC Cobra, Ford GT40, lolaT70 –
endurance racesin Europe)... so no problem on that. I am also sure that
ignition is well timed...I had it checked several times and had a gaz
analyser installed to verify this.

My engineering is questionning the pression ratio or a conception problem
on the pistons themselves (ref. of the pistons : SRP40D)...

Once again thanks for your answers. Hoping to get further assistance and
comments from you and/or surpercharged engine owners and/or AS engine
owners. To be continued.... Best regards.

[bigmack]

Sorry to hear about all your problems with the engine. Just out of curiosity, which pistons are melting? Usually, with overheating, the #7 and #8 cylinders go out first. You certainly have tried to monitor what is happening. If the fuel supply is good and the Air Fuel Ratio is sound(this needs to be around 11.5:1 to 12:1 A/F ratio on a forced induction engine at Wide Open Throttle (WOT)), then this would leave timing and engine oil and water cooling. I'm not an expert on turbo or blower engines, but I seem to recall a formula for retarding the timing depending on the amount of boost you are running. Others on the site can probably remember it for me. 1 to 3 degrees of retard per pound of boost? You might try installing an adjustable timing retard dial. Its tough for me to hear engine pinging on this car, and a knock sensor isn't going to do much good on a high performance chevy. You really need to adjust the timing and check the power output on a rolling dyno. Have you thought about coating the tops of the pistons and cylinder head combustion chambers with a ceramic coating? Its sort of a new thing that is gaining popularity. Sorry that I don't have an answer for you. How are you running the engine? Track days? Drag Strip? Driving around town?
Good luck and let us know what you find out.
Cheers!
-Mack

[hemon]

Hello everybody,
here is the real owner of this Ultima can am with supercharger.Excuse me for my language because my girlfrien isn’t here to translate....
First i want to thank all of you for your answers. It’s very kind of you to try to help me.
I still thinking about my problem and i don’t find the sure answer...
I have again a question and i hope you all could answer to it : do you know the octane number of the un leaded gasoline in UK and in USA (RON & MON) ?
In France, we have a gasoline called SP95 and SP98. The octane number of the one is in fact 87 and of the second one is 88.
Thank you for answers
Fab

[Boosted Ls1]

Please post pictures of the damaged pistons. That could help a lot with providing a diagnosis. Don't the french guys know what the cause is? Have they seen the broken pistons?

Boosted.