LT1-LT4 Modifications - Issues after rebuild




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blackta97
05-02-2012, 12:19 PM
Vehicle in question is a 1997 TA A4

Here's that back story:

I bought the car over the summer with about 66k miles. It had a misfire after it warmed up, an exhaust tick, and was leaking oil from the timing cover. I wasn't terribly concerned about any of this stuff. I drove it here and there over the summer and parked it for the winter (I live in the rust belt), pulled the motor and began to tear it down.

I replaced almost all the gaskets in the motor; head gaskets, oil pan gasket, timing cover gaskets, valve cover gaskets, you name it, I probably replaced it. I also replaced the oil pump with a stock replacement Melling, welded pick-up tube, hardened pump driveshaft. I replaced the waterpump with an autoparts store brand one, nothing special, and I replaced the optispark with a summit brand one (might come back to bite me, but I wasn't about to spend $350 on a REMAN (according to Summit's customer service) GM unit. I also replaced the coil and ICM with new ACDELCO ones.

I put the heads back on with NEW HEAD BOLTS and new felpro gaskets. I took a few days to think about my goals for the motor and ordered the GM LT4 Hotcam Kit. Never having done valve springs before, I took the heads to a local performance shop and had the valve springs put in. I talked to the owner who advised me that the head gaskets would be fine to re-use since they had never been heat cycled. I picked up my heads a few days later and installed them with NEW HEAD BOLTS.

I slowly reassembled the motor and put it back in the car. I also put Pacesetter LTs on with a Pacesetter Y Pipe, into my SLP Loudmouth which I purchased over the summer. Other mods included OTVC wires (AC Delco copper plugs gapped to .045, for those of you wondering), PCMFORLESS tune, no EGR, no AIR.

I filled it with fluids, switched to green coolant, and turned the key. Nothing. Just cranked and cranked. I started to trouble shoot the coil, icm, and opti using Shoebox's tips off his site. Everything checked out fine, so on a whim, I replaced the wire leading from the coil to the optispark, turned the key, it cranked for a second and fired. When it finally did start the first time, it was backfiring. It literally sounded like gunshots. It smoothed itself out after a few minutes and stopped.

I never drove it or put it on the road, but I managed to get it off jackstands for the first time in six months. When I put it in drive with my foot on the brake it would start to backfire again and the idle would kick wayyyyy down.


This triumphant moment was short lived. After warming up for a few minutes, the garage began to smell terrible and fill with a haze. Whatever it was, it was so strong that it made my eyes tear up. The exhaust didn't appear to be smoking abnormally. It was difficult to tell what color it was and I don't want to assume. It could have been burning off moisture in the exhaust for all I know.

I called PCMFORLESS and they were convinced that I had a vacuum leak, I started the car and sprayed around the intake with some highly flammable electronics cleaner I had. Either I didn't find the leak, or i don't have one.

A few nights later, my friend came over to help me trouble shoot the car. The first thing he did was squeeze the radiator hoses. He squeezed the one leading to the thermostat and we heard a gurgling near the intake manifold. We found air to be leaking through the bolt that also holds down the alternator bracket. When I installed the intake manifold, I RTV'd the gaskets where they met the heads, but neglected to RTV where the gaskets met the intake. Stupid me. I originally thought that the bolt might go into a water jacket (I'm kinda new to V8s) but I was wrong. After running the car for a few minutes, coolant began to leak from the bolt.

I concluded that the only possibility was a bad head gasket from being compressed twice. I tore down the passenger's side and found two of the spark plugs to be shiny clean, and two to be sooty (I've read about burning coolant and water creating a steam cleaning effect on the plugs). When I loosened and pulled off the passenger's side head, all the cylinders had coolant in them. I neglected to drain the coolant prior to pulling the passenger's side head, so it's difficult to say whether the coolant was already in the cylinders or not, but drained it before I pulled the driver's side off.

I tore down the driver's side and found nothing abnormal, no coolant in the cylinders.

I ordered ARP bolts and new felpro gaskets from Summit and that's where I'm at now. I drained the coolant and there was no oil in it. I dabbed the oil sitting in the valley with a piece of white paper and the oil didn't appear to be green.

I drained the oil and it didn't appear to have coolant in it.

I should mention that there were no head gasket issues before the tear down. I'm taking the heads to be pressure tested tomorrow so that I can rule them out entirely.

Thoughts and opinions are welcomed.


quik95lt1
05-02-2012, 12:52 PM
sounds like ur on track......i would've compression tested first before i was so quick to rip the heads off but still........when you installed the cam im assuming you lined up the dots on the timing set properly so the cam is in straight up correct? also what procedure did you use for adjusting the valves?

blackta97
05-02-2012, 07:04 PM
timing was lined up correctly, my buddy used shoebox's how to to adjust the valves


Bigtoyz
05-03-2012, 03:08 AM
I had same problem after my rebuild. But we pumped up the lifters and adjusted them. By the time to start the car it back fired and bucked. We readjusted the rockers again while running and will never adjust by pumping the lifters up. I read the idea some where so we tried it and never again. Best way is run it and set them. When they start to quite it down the pushrods will start to spin....after than half a turn and tighten the set screw. I that the CC Pro Mags very nice feature....dont have to worry about rocker nuts backing off.

But I had the guy you mention do my tune also...... for respect of others who have good luck I will refrain from comments. I then taught myself how to tune the thing.....bought a wide band o2.......and getting it pretty dialed in. Easiest way is to take it to someone who has a dyno. And once they have the drivablity down they can dyno tune it. Those guys are good at what they do. Better to have live tuning vs mail order I believe. Unless you are sending them data logs. And wide band o2 logs.

Patrick

lt1-xjs
05-03-2012, 09:29 AM
You had mentioned you didn't seal the intake properly, did you put the required thread sealant on the threads of the head bolts?

blackta97
10-03-2012, 09:46 AM
just to update this, heads were pressure tested and were fine. I put new headgaskets in it, and sealed up the intake manifold. The backfire was because the wires on cylinders 5 and 7 were backwards.

RamAir95TA
10-03-2012, 10:58 AM
just to update this, heads were pressure tested and were fine. I put new headgaskets in it, and sealed up the intake manifold. The backfire was because the wires on cylinders 5 and 7 were backwards.

90% of the time this is the problem. Always look at the easy stuff FIRST.