Well, I finally got my LT1 up and running today. Ran it for about 5 minutes or so and then.... knock knock knock. Had 40psi of oil pressure at idle, 70 off idle. Let it warm up while I diagnosed a missfire and never revved it past 3,000 which fixed the missfire. The car is still on the jack stands. Put new clevite bearings in and had the crank polished before stabbing the motor. Tourqued everything with my snap-on torque wrench.

I am sick in the stomach. Anyone got any ideas on what might have went wrong?

 

Bearings had the wrong clearances? Hard to say. Either way, you're going to have to pull the engine and strip it down again.

 

UPDATE!

Well I dont know how it happened, but I had 4 rod caps loose and one that was almost off! I know I double checked every nut before putting it together. I did have to click some 5 times or more till they stopped turning. I am thinking maybe my torque wrench is out of cal and I could have stretched the factory rod bolts. I was also using the lowest setting on it and it may not be acurate that low.

Good news is that there was no damage to the rods, crank, or even the bearings. There was some scuffing on the back of the shells on the rod that almost came apart but it didnt spin even with a 1/4" gap.

So I guess I am going to pull the heads and the rods and send them both to the machine shop. They are going to surface the heads (alum) and install ARP rod bolts and resize them. So that means I need to get new gaskets, head bolts, and rod bearings.

I am going to borrow a calibrated torque wrench from a buddy of mine who works on airplanes (they have to cal all of their stuff at least annually) when I put it together. I am going to loosen and retorque my mains as well.

I didnt pull the heads when I put new bearings in it or have the rods checked so that is where all of the new expense comes from.

Just sucks and goes to show you do it right the first time. Now i am already over budget on this conversion and this ordeal is going to set me back another $500.

 

With the rods caps that loose, there's a good chance more damage was done. The pistons may have hit the heads.

I still torque my rod bolts but even ARP doesn't recommend torquing rod bolts. The preferred method is to use a stretch gauge.

 

if you have new bolts and nuts, torque them and loosen them, repeat this a couple of times. This will burnish the contact faces and give more accurate torque readings, the readings will otherwise be too high because of friction.

 

well since no ones asked... what were the bearing clearances?

 

Clearance was about .250 with the caps loose.

I'd check the pistons, too.

 

what do you mean with the caps loose?... did you not torque them down and plastic gauge them before you did final assembly?...

 

I did not plasiguage on the first assy. The machine shop checked the crank after the polish and all was in spec and I got stock size Clevite "P" bearings from the machine shop. Yeah I know, shoulda, woulda coulda do it again... hind-sight is always 20-20. I am assuming there are multiple things that went wrong with my first assy (not my first motor build) as in my torque wrench I believe was not accurate and maybe I didnt double check everything like I thought I did. Either way I am not out much money, just time. Now I am going back and doing what I should have the first time.

When I pulled the heads they were just starting to seep coolant on the ends so it was a good thing I tore the motor back down, and yes, the #7 piston (.25" clearance) was just kissing the head. Only knocked the carbon off the head and piston (no valve contact), all else was good. As soon as I heard the knock I shut it down and pulled the motor. If I had ran it any longer I would be buying a new motor or at least a bottom end.

The heads and rods are now at the machine shop. The heads are being surfaced and the rods are getting new alloy bolts my machine shop is recommending (not ARP's) and a resize. I will be putting it back together after cleaning the carbon out of the pistons and heads with some Felpro 1074 head gaskets and some stock replacement Felpro head bolts. I will be using the same rod and main bearings. My machine shop said they were still perfect and didnt need to be replaced. I will be putting a head cam package (AI or LE) on it some point in the future with a tune by Carolina Auto Masters after that since I am moving near there in a few months. I will get better ARP head bolts at that time.

I am going to use plastigage this time, use ARP bolt lube, loosen and re-torque the mains, cycle the new rod bolts a few times, use a calibrated torque wrench, double check everything, and use a paint marker to identify all double checked bolts.

 

Might as well deburr and polish those rods while you're at it...