Cobrainbound

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2003 cobra coupe 65000 miles. Had the engine rebuilt in fall of 2020 (it had a leaking intercooler and no compression on cylinder 8). I was not given a full parts list but what I was told (that I remember) was replaced: every seal and gasket inside the engine, pistons, intercooler, plugs, wires, valves/seats, hardware and oil cooler assembly, and tuned. There may be more but I moved shortly after and the company changed hands, so I never got a full list. The car has a stiegemeier ported Eaton, 2.76 upper, jlt cai, aem wideband, x2 DW300c fuel pumps, Deatschwerk 60lb injectors, and a 90mm MAF. The car has sat for a few months and now on cold start I am getting a white cloud of smoke and the smell of fuel. I pulled the plugs and they are all varying degrees of black and some are wet with something, not sure. I looked down into the plug holes and the "new" pistons have varying degrees on black build up. I dont seem to be losing oil or coolant and I cant take it back to the shop that rebuilt it. I spent over 16k having it rebuilt and am lost were I should start looking into the problem. Any ideas or help would be much appreciated. Thanks.
 

Cobrainbound

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It does seem to run good and afr is good, I hear a ticking noise somewhere underneath but I believe it's the exhaust manifold. Looking through the plug holes the pistons look very black like carbon buildup, maybe blow by?
 

Roush6018

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ok i will help out with your problem with what i know about the 2003 COBRA MOTOR.

if your original problem was no compression cylinder 8, these motors are very strong and your engine repair shop may have only replaced the #8 piston. you have 65k miles on all 7 of the other pistons so they should be black on top.

you smell fuel and see white smoke. you hear a ticking noise.

this is not a very good sign and can be very hard to find out where the problem is with this engine. i did run some 60lb fuel injectors with my 2.76 pulley and made good power, but it did smell like fuel at slow speeds and idle because the motor is getting more fuel than compared to stock injectors even with my tune. i am running stock injectors now.

the white smoke is a problem with the motor burning motor oil or coolant.

to fix this issue will require you to install a new set of spark plugs and fill up the gas tank, then drive around 100 miles and then pull the spark plugs out and see if any have brown spots or are wet from burning oil/coolant in that cylinder. if one spark plug is dirtier then the problem is inside that cylinder. make a note of the cylinder that failed.

also , i recommend do a oil change and fill the oil to the max full line, then drive 1000 miles on the same oil and the level should not change. if the oil level does drop more than 4 to 6 millimeters on the dipstick after 1000 miles then this means you have worn oil rings on 1 or more of your pistons. or a oil leak somewhere.

it took me a very long time to get my 2003 COBRA to run good. i have been able to enjoy it about 8-10 thousand miles since the last rebuild and i am pretty happy with it.

to me it sounds like your shop did rebuild the motor for the problem you were having, then letting it sit for so long didnt help, now, it might have a new issue that was not present when the intercooler let go and caused the engine damage.
 

01yellercobra

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If you have an O/R mid pipe you're going to to smell gas. Especially at cold start. Was it tuned before the failure or were all the parts added after the rebuild? How was the engine broken in after the rebuild?

I'd start with a compression check and possibly a leak down check. Make sure things are sealed as they should be.
 

Cobrainbound

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If you have an O/R mid pipe you're going to to smell gas. Especially at cold start. Was it tuned before the failure or were all the parts added after the rebuild? How was the engine broken in after the rebuild?

I'd start with a compression check and possibly a leak down check. Make sure things are sealed as they should be.
I have stock manifolds and mid, just an slp catback. It was tuned after rebuild, fuel pumps, injectors, maf and cai added after rebuild but before tune. I can't remember how many miles I drove it for the break in but I followed the instructions of the shop, no long idling, changing the rpm while driving, no pulls or hard acceleration, mixed city and highway and had them change oil after breaking in, at least 1000 miles after rebuild before tune but not sure exactly. I'll see if I can get some compression tests done this month and change the oil and plugs.
 

TerminatoRS

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How much white smoke are we talking about?

Mine will puff out a bit on cold starts if it's been sitting for a week or so. It's done it ever since the 60lb injectors went in so I figured it's unspent fuel probably from a leaky injector (I bought them used). It goes away almost instantly and then runs great. No coolant consumption whatsoever. Oil consumption is minimal. Stock unopened motor with ~84k on the clock.
 

01yellercobra

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I hate when shops say no hard pulls or acceleration. The rings need pressure to seat and that doesn't happen at part throttle.

I would start with a leak down. My guess is the cold start might need some work. But if it's not using any fluids I'm sure it's fine. There were black deposits on the pistons as soon as you started it up.
 

Bullitt1448

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White smoke is generally coolant or water, could be some condensation. Overfueling is generally black smoke
 

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