replacing burnt pistons

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SIZEMOREMK

Junior Member
Had an overheating incident the other morning that we thought was the result of overheating due to frozen thermostat.

Turns out both HGs are blown and some pistons are burnt, but the shop says that it looks like I had been having a good bit of detonation and that the theadgaskets were probably leaking for some time; also said the bearings showed signs of detonation.

I have never had what I thought would have been an indication that my engine was detonating, never heard or felt anything... The car had no knock sensors, but I believe I will be having them put some knock sensors back in it.

My tune was suppose to have been pretty conservative, as this is my daily driver... Really need to find root cause of the detonation.

Anyways didn't mean to run with those details, but I have a question on replacing pistons:

The guy says that the bores look like they could be re-honed and just put new pistons, rings, and bearings in it.

It has been some time since I have rebuilt an engine, but a decade or more ago I was under the impression that one didn't simply just swap in new pistons.

The couple of machine shops I dealt with years ago needed the pistons in-hand to properly size the bores due to manufacturing tolerances and such.

Have the piston manufacturers tolerances improved over the years?

I am kinda concerned about piston to wall clearance.

Or am I just worrying too much, and is putting new pistons in used bores normal?
 
Sorry again for your situation but, this is concerning to me. When I sold you the car it was running so rich that it was pathetic. I can't imagine detonation running that rich. Did DR run it lean on the tune? How long was that DR tune in your car? I thought that you got it retuned straight away?
 
It must be something unrelated. I had the car tuned by DR the morning after I got it, then I had some gears and blower pulleys swapped and retuned at MO's. I know it was right when it left there. Jeff showed me the fuel pump duty cycle and I have a wideband in the car that matched what the shops wideband read.

I hadn't logged the wideband in awhile either, the car was running so good that I got comfortable with things. I really wish I had looked at the AFR at WOT recently... Would have been nice to know if things were leaning out...
 
On the piston question, it's just a matter of measuring all 8 bores and comparing to the piston specs.
I've run new pistons in a honed standard bore block many times.

With your heat issue, I'd have your macninist run a dial bore gauge down each cylinder to ensure they are not tapered beyond his suggested tolerance.
Taper would require reboring the cylinders.

Having the pistons in hand is essential to place best matched diameter piston in each finish honed cylinder.
Part of 'blue printing' an engine, rather than a backyard rebuild.
 
SIZEMOREMK said:
I hadn't logged the wideband in awhile either, the car was running so good that I got comfortable with things. I really wish I had looked at the AFR at WOT recently... Would have been nice to know if things were leaning out...
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You can't ever get comfy with a supercharged car. Ever
 
Gentleman. I do not know how to post an original topic on this forum. So apologies to the topic provider.
I recently purchased a 2003 Marauder 1/10/15. The vehicle is in excellent condition. However I just had a state inspection done and the check engine light came one when I was given the vehicle back. There is and light skip in the engine timing noticed now. Also when I accelerate, it's and light rumble in the transition from 2nd to third.
Please remember,this was not evident prior to state. Any information would help Gents.
Jimmy
 
jimmy.scales.33 said:
Gentleman. I do not know how to post an original topic on this forum. So apologies to the topic provider.
I recently purchased a 2003 Marauder 1/10/15. The vehicle is in excellent condition. However I just had a state inspection done and the check engine light came one when I was given the vehicle back. There is and light skip in the engine timing noticed now. Also when I accelerate, it's and light rumble in the transition from 2nd to third.
Please remember,this was not evident prior to state. Any information would help Gents.
Jimmy
Click to expand...
Jimmy
your question will get lost in this thread. go back to the forum main page, pick a section like shop talk, in there at the top left of the pages is blue button 'new thread'
go for it and good luck
 
If your engine is out and apart rebuild it right, these things are way to expensive to try to patch one back together. Get a good set of forged pistons, replace the rods, bore the block, balance everything, NEW TIMING COMPONENTS...this is not going to be a cheap venture...but to do it right and not have to worry about it again will be worth its price.

Detonation affects parts over the long term, your gaskets may have saved you form a hole in the side of the block. Powdered metal rods are not long for the world when they are run under knocking situations. Damage could very well be already done and just waiting to bite you...Just my opinion...
 
Curless said:
If your engine is out and apart rebuild it right, these things are way to expensive to try to patch one back together. Get a good set of forged pistons, replace the rods, bore the block, balance everything, NEW TIMING COMPONENTS...this is not going to be a cheap venture...but to do it right and not have to worry about it again will be worth its price.

Detonation affects parts over the long term, your gaskets may have saved you form a hole in the side of the block. Powdered metal rods are not long for the world when they are run under knocking situations. Damage could very well be already done and just waiting to bite you...Just my opinion...
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It was a MMR 600 with forged rods and pistons. I believe he is getting the same pistons again from MMR. Will also replace timing components.

Apparently heads are warped too, so I guess the machine shop will determine if the heads should be replaced or if they can be straightened and milled.
 
SIZEMOREMK said:
It was a MMR 600 with forged rods and pistons. I believe he is getting the same pistons again from MMR. Will also replace timing components.

Apparently heads are warped too, so I guess the machine shop will determine if the heads should be replaced or if they can be straightened and milled.
Click to expand...

I believe that I gave you the paperwork from MMR. Is their any warrantee on anything?
 
MMBLUE said:
I believe that I gave you the paperwork from MMR. Is their any warrantee on anything?
Click to expand...

Yessir, I have all that, the warranty was for 1 year but problems due to detonation wouldn't be covered.

I still haven't verified the root cause of the problem... I'm gonna be worried until I can determine the cause. It's possible the fuel pump started to go and leaned out at some point. In the future I will do a better job of monitoring my wideband.
 
SIZEMOREMK said:
Yessir, I have all that, the warranty was for 1 year but problems due to detonation wouldn't be covered.

I still haven't verified the root cause of the problem... I'm gonna be worried until I can determine the cause. It's possible the fuel pump started to go and leaned out at some point. In the future I will do a better job of monitoring my wideband.
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this is where watching your fuel pressure gauge for blips could save you.
it may lean out for such short time that a/f wideband won't go mad lean,
but seeing fuel psi waver, or not rise when you mash the throttle should make you stop boosting immediately and garage test your fuel system.
ask me how I know.
 
any chance your fuel filter is clogged, or you pump was dying? it might have created a lean situation and without the knock sensors it detonated because the computer didn't retard timing as it should have, because at WOT your fuel table is commanded and not controlled by the sensors like at part throttle so your knock sensors are really the only saving grace at WOT, and with these cars there is so much sound deadening stuff its hard to hear when something in the engine is going wrong especially at WOT. I would hate to see you get it back together and the same thing happen.
 
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