HELP AFTER REBUILD!!!

[PotatoC570]

ALL,

Last year about this time I toasted the motor on my 99 cobra.

I went through a full rebuild, forged rods, pistons, clevite bearings, 03 head swap.

I did everything myself and got it running. Up till I blew it up the motor would stall from time to time. Now when i drive the car it stalls out after going from high rev to low. I originally thought it was an O2 problem because the heater circuit was cut but I fixed that. Now, when it stalls out It will not fire up until my foot is flat on the floor and then it smells like the motor is getting flooded. I did not have the motor tuned since the rebuild with the new heads, knock sensors have not been tuned out yet.

I am 6k into this rebuild and I am getting frustrated with everything.

 

[SilverNotch]

Had similar issues mine was the mass air. Dirty cleaned it. Plus the canned tune I had would stall at stop light. Did both it was fine.


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[PotatoC570]

Had similar issues mine was the mass air. Dirty cleaned it. Plus the canned tune I had would stall at stop light. Did both it was fine.


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I will try to clean that out, it did sit in a barn for a year. My tune is still factory.

 

[DSG2003Mach1]

did you change compression? that will screw up your load as well. I had my car dialed in dead nuts and when the motor had to be rebuilt (oiling failure) we dropped compression a tad and when I put it back together it wouldnt hold an idle. I chased my tail for quite a while sure it had to be a vacuum leak or something, it was tune issue the whole time (from the drop in compression it wasnt seeing enough load @ idle so it "hunted"). Id get it to a tuner asap or at least send some datalogs

 

[01yellercobra]

The stalling is probably the IAC. They can go bad randomly. When you did the rebuild what exactly was done? When you say new heads do you mean rebuilt back to stock or ported and polished?

 

[PotatoC570]

did you change compression? that will screw up your load as well. I had my car dialed in dead nuts and when the motor had to be rebuilt (oiling failure) we dropped compression a tad and when I put it back together it wouldnt hold an idle. I chased my tail for quite a while sure it had to be a vacuum leak or something, it was tune issue the whole time (from the drop in compression it wasnt seeing enough load @ idle so it "hunted"). Id get it to a tuner asap or at least send some datalogs

I did put in very slight dished piston to accept boost easier in the future.

 

[PotatoC570]

The stalling is probably the IAC. They can go bad randomly. When you did the rebuild what exactly was done? When you say new heads do you mean rebuilt back to stock or ported and polished?

I put forged internals in with slightly dished pistons to accept boost. I put 03 heads that were rebuilt to stock, no porting or polishing. Just strapped them on. It'll run at idle but once I put it in neutral to coast to a light it will stall on me.

 

[DSG2003Mach1]

id get the tune taken care of before banging my head off the wall chasing a ghost

 

[PotatoC570]

id get the tune taken care of before banging my head off the wall chasing a ghost

Take it to a shop, or get a tune from Bama or SCT to fit my needs?

 

[01yellercobra]

I guess it depends on how much you decreased the compression. It could be a combination of factors. I'd make sure things are good mechanically. Then if it's still an issue you'll need a tune as DSG suggested. What's your current compression?

 

[PotatoC570]

I guess it depends on how much you decreased the compression. It could be a combination of factors. I'd make sure things are good mechanically. Then if it's still an issue you'll need a tune as DSG suggested. What's your current compression?

Not a clue.

 

[DSG2003Mach1]

dear god stay away from Bama unless you wanna build it again. I would think you could find a reputable shop near PA to go to. Personally Id rather go to a shop where the tuner and can put eyes and hands on it in the event its not a tune issue they can help you diagnose or possibly repair on the spot.

 

[PotatoC570]

dear god stay away from Bama unless you wanna build it again. I would think you could find a reputable shop near PA to go to. Personally Id rather go to a shop where the tuner and can put eyes and hands on it in the event its not a tune issue they can help you diagnose or possibly repair on the spot.

There is a guy locally who does everything from Audi to Mopar with a dyno. I'm thinking about giving him a call to see what he would recommend. That way if it is a tune issue, he could put one into the car. But, I am just trying to get it to a point where I can take it to work and not get myself stranded some place.

 

[01yellercobra]

Not a clue.

You have the specs for the pistons you installed don't you? And I'm guessing you installed stock style head gaskets.

 

[01yellercobra]

Take it to a shop, or get a tune from Bama or SCT to fit my needs?

SCT is just the software used. The shop would use SCT or Diablo to write the tune. There are others, but those are the main ones used for our cars. SCT is the more popular software.

In your case I think taking it to a shop would be your best bet.

 

[PotatoC570]

You have the specs for the pistons you installed don't you? And I'm guessing you installed stock style head gaskets.

Here are the pistons that are installed

https://www.summitracing.com/parts/SLP-H831CP

 

[Nightmare302]

Here are the pistons that are installed

https://www.summitracing.com/parts/SLP-H831CP

You won't be running boost on those pistons as they are the same thing as stock hypercraptic.

 

[01yellercobra]

Well, the first issue I see is that you went with a hypereutectic pistons. Those aren't good for boost. Which leads me to believe you didn't change the rods either. So I definitely wouldn't run boost.

Second, those are for a SOHC truck engine. IIRC the 2V's have much smaller combustion chambers than the 4V. So the pistons have a decent dish to bring compression down. So you're probably in the low 8:1 range. At which point you've changed the compression so much you need a new tune as DSG has suggested a couple of times.

 

[PotatoC570]

Well, the first issue I see is that you went with a hypereutectic pistons. Those aren't good for boost. Which leads me to believe you didn't change the rods either. So I definitely wouldn't run boost.

Second, those are for a SOHC truck engine. IIRC the 2V's have much smaller combustion chambers than the 4V. So the pistons have a decent dish to bring compression down. So you're probably in the low 8:1 range. At which point you've changed the compression so much you need a new tune as DSG has suggested a couple of times.

Forged Rod and crank

 

[PotatoC570]

https://www.summitracing.com/parts/esp-428135545933

https://www.summitracing.com/parts/esp-5933f3d