ls1 cam swap - is a case relearn needed? Won't fire..

Hi guys,

Apologies if this was mentioned out here...I've been searching and looking my butt off...but didn't really find something that fits our problem.

My buddy and I just did a cam swap on an LS1 from 2000 GTO...pretty healthy one at that.
It was stock and the timing gear and chain were also replaced (90K miles). The original chain was really sloppy. It was a tuned engine (headers and no real other go fast parts) but does have a corvette pan etc. Nothing crazy at all...

The swap went off without a hitch however we were worried about the potential timing and the crank sensor position due to the originally lose chain. The new chain and gears have really no slop, as expected. Tight timing! Good stuff...

When trying to start this thing...it popped a few times, kinda back fired a couple but would never fire up.

I have HPtuners in hand and have read many threads about the case relearn...the only caveat...this engine is in a different car, no anti-theft stuff, no smart key, just a normal key...all plain jane wiring and a stock GTO ecu (I don't know which one actually - waiting to hear back from my buddy). If that makes any difference...

I am not a tuner by any means but do play with my own racecar stuff...we're very curious as to how to get it to at least fire up and then take it to a tuner (they are backed up for 3 weeks).

I read that HPtuners can easily do this...now we're looking for the how-to!
Thanks

It shouldn't need a case learn for what you did but it likely needs other adjustments in the tune for the cam change.

But even on most cam swaps, you should be able to pedal it to life but it won't run the greatest with the stock VE/MAF settings and idle settings for a stock cam.

After posting that question...I found the following:
VCM Controls > Special > Case Learn - following on screen instructions...

Hope that's that easy...

@5FDP -

Thanks exactly what we thought...I wonder if just more throttle was needed...we were a bit reluctant to 1/2 throttle or more...it does have a cabled throttle body...

I myself did a very hardy cam swap on an LS3 a few years ago and it took serious effort to get it to run (stock tune). It wouldn't run under 2500rpm (.658 lift, good overlap - forgot the numbers). That motor is in heaven now... ;>

Quote:

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Originally Posted by fast53

After posting that question...I found the following:
VCM Controls > Special > Case Learn - following on screen instructions...

Hope that's that easy...

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Why are you afraid to give it more than half throttle? Under no load, it would take a mechanical failure to cause a problem if you revved it up. You said you did a cam swap, if its a big one, you are gonna need to bump your base running airflow table a few g/sec and put your desired idle at 1000 just to get it running. From there, you can start roughing in your fuel and spark and then go back to the RAF table and start tuning that. Big cams can be a real PITA to tune idle so keep at it. Its gonna want more spark and less fuel along with a bump in air.

Thanks for the info...
Not overly scared to pop in throttle...it didn't feel like it wanted to pop over...the loud pops (backfires) kinda indicated that we were pretty far off of timing (that's from my old school days I guess).

I gather the case-relearn is still a valid start or will it help at this stage? We'll be hooking it up tomorrow evening to try your suggestions...

Minor update...2004 GTO LS1 and ECU...if that matters. VATs are deleted...

So I've looked at my HPtuners VCM 3.0.5, scanner and editor...
Where can I find the VCM Controls > Special > Case Learn...or does it have to scanning the car and then it will pop up?

I'm not sure it will matter. Doesn't the engine have to be warmed up before it can do a case learn? I may be wrong, but I thought it had noticed that before

Yes, case learn needs to be done fully warm and able to run against the limiter cleanly. Case learns are not needed for simple cam swaps.

OK...it does make sense...
I'm wondering that the issues we are seeing is due to the worn out gear and chain. He had it tuned recently...few months back.

He got the urge for the cam swap and while we were in there, we had no choice but the rip the gears and chain out. They were really lose.

We are looking at it later tonight....and from what we have both read, it may take considerable throttle input to get it to run...is that a valid statement?

You should be able to pedal it enough to stay running, if its popping and backfiring, you better check cam timing if the timing chain is that bad.