Ironembraced

My '98 vette just got finished getting a 2006 iron block 6.0L installed today, the mechanic tried to start it, and it won't fire up. It is definitely a 24x engine, same as the previous engine. The previous engine ran fine when it was pulled, besides a massive oil leak and spun bearings.

He says there is both spark and fuel, but he is by no means an expert on LS1's. It's not throwing any engine codes. He seems to think it has something to do with cam timing and the previously tuned PCM. I have plans to take the vette to a tuner in the city next week, but I need to figure this problem out before it gets trailered over there. My tuner says that there is no way the old PCM or camshaft is to blame for the engine not firing up. My only guess so far is that the spark plugs are the problem. I am going to the mechanic tomorrow morning to have him replace the spark plugs and help him look for a solution.

Here is what I have currently installed on the new engine currently:

Comp Cams LSR lobe
317 heads - ported / milled
stock 6.0L bottom end, somewhere around 10:1
LS6 intake manifold
42lb green injectors
Racetronics fuel pump
Vararam B2
85mm MAF
new iridium plugs / new bosch wires


This is what was on the previous engine that the car was tuned for:

forged 408ci stroker , 243 heads, anywhere inbetween 8:1 and 9:1 compression
custom cam grind 235/235 .581 112 LSA
cam timing advanced +4 degrees.

Everything else above stayed on the new engine. Can anyone out there offer any advice or ideas? I just bought this corvette a couple months ago only to find out on the drive home from out of state, that the engine had been destroyed. I am completely new at this stuff. Any help is greatly appreciated!

dodson55

iTrader: (18)

Did you use the 98 cam and crank sensor or the 6.0 sensors I think that 97 and 98 are different then 99 up but double check me also did he check to see if the injectors were pulsing just because it is getting fuel to the rail does not mean it is getting in the engine it sounds like to me maybe the cam or crank sensor is not hooked up or might be the wrong ones

Ironembraced

Using the same sensors the newer block came with. They should be the right version, but you gave me a great idea. If all else fails, Ill have the sensors from the old block installed on the new block. Thank you

Unertl42

iTrader: (63)

I agree with Dodson55. Be smart about it, the newbie thing to do is throw money at it hoping that $100 bills will miraculously make it work. We've all done it, the sensors need to be double checked, make sure you getting fuel pressure at the rails, and pull a plug and make sure you're getting spark. Remember, Fuel, Air and Spark are what's needed for that baby to run.

Rick364ls

iTrader: (1)

any chance exhaust valve hit? 317s millled to 10:1 may be close. I am no pro at these yet but just a thought. i am debating a tsunami with milled 317 and think it will hit. i know tsunami alot bigger but ya never know

garygnu

check for any loose ground wire.

usmcz28

iTrader: (3)

Why have a "mechanic" unfamiliar witht these engines do the swap in the first place, that seems to be the first mistake.

mark21742

Will it try to fire then die off? Have him put fuel pressure gauge on the rail and try to start it....one of my friends just did a cam swap on his 03 vette. It would fire then die off.....he had fuel pressure when he turned the key on, but the fuel pump wouldn't kick back on after the car fired...for some reason the fuel pump relay was not grounding....they hot wired the relay and then it ran great....I don't know if they found out why it did this, but it looked like everything was wired back up right

chrisdacarnut

iTrader: (1)

Something isn't plugged in.

Ironembraced

I must have misunderstood the mechanic yesterday. It DOES "fire up", but it barely idles and back-fires violently until dying seconds later. The RPM gauge works, and there are no engine codes.

The mechanic seems confident that the engine is just getting to much fuel due to a the aggressiveness of the original camshaft and the timing.

But I called my tuner, he says he has never ran into a problem like this with back firing etc.

Now I am getting a little bit worried...

Anyway it will be another week before I can get it trailered to the city.

Ironembraced

Wow, I really hope not, but I wouldn't know what it would sound like if it happened. The heads were only lightly milled by a local machine shop.


I never said he was unfamiliar with LS1's, he has done plenty of them. He is just not an expert with tuned PCM's etc. He got his start building carburated racing engines with his dad, I am assuming he isn't a complete dummy.



Yeah sort of, except it idles rough and backfires and then dies. Could the fuel pressure still be the issue in this case? I wouldn't think so..

1madss

iTrader: (10)

Did you need to move the cam position sensor to the front cover? ( I can't recall if the '06 6.0 use the front mounted cam sensor or not)
If so and the tach does not work, you might need to swap the 1st and 3rd pins on the sensor extension.

Ironembraced

The cam sensor is in the original location in the back of the engine behind the intake manifold. The tach is also working.

I guess I need to find out if a wild camshaft tune (or a shorter piston stroke) could have actually caused this. If not, then I am out of ideas.

NVR_SPDS

iTrader: (39)

I personally dont think the tune is to blame here. In my car, I went from a 234/230 and full bolt ons, to a 224/224 and stock manifolds cats on the same tune. Fired right up, and idled just fine after it figured out the idle.

After i dropped a valve, on the 224 tune, i added AFR 205s, and a 224/228 cam with the same result. Fired right up.

In my wife's car, i went from a stock longblock, 231/237 to milled 799s, 227/230 on the same tune, and she fired right up and idled easy.

chrisdacarnut

iTrader: (1)

It's more than likely the tune if it is firing up but won't idle... Unless you happened to bend some valves...

suspect2001

sorry i can't give you immediate advice, but since your coming to oklahoma city........try giving Corwine Performance a call. talk to the owner Shane. he's all about LSx engines, plus i get my truck custom tuned through Shane by Glenn Lapinski. Glenn does awesome tunes.

Cowine Performance
405-793-1166
2412 Regency Pl
Moore, OK 73160

Rick364ls

iTrader: (1)

Guy did not mention car started at all guess my valve theory went out window. Just thought to make 10.0:1 would require alot of milling

Ironembraced

Ouch, why did you drop a valve on the 224 tune? How was the engine running before it dropped and how long did it take to happen??

I have been worried about dropping a valve before the engine swap even began, because I've got flat top pistons with alot of lift and milled heads.

Ironembraced

So the cam & heads might not be the issue, but what about losing stroke going from a 408ci to a 364ci?

remauto1187

iTrader: (1)

Had a older firebird with a v6 do this. But it idled perfectly and as soon as you started to load the engine and got around 25-35mph it would cough, kick, sputter and even backfire. It was a bad fuel pump. I tested the pressure at the rail and it checked perfectly in spec at idle. Rev up and it would fall like a rock to around 10psi. New pump and it ran great.