ridiqls

Def will update. Going to spend the day tomorrow to finish the diagnosis and go from there. Hoping and willing it doesnt have anything wrong with the bottom end.

Now that I know how to find TDC on Cylinder #1, I'm guessing to get TDC on the other cylinders, you turn the crankshaft pulley clockwise 90 degrees and that should put the next cylinder in the firing order (I think #8) at TDC right?

So you really only need to find TDC once and then just count the number of 90 degree rotations for the rest of the cylinders?

97rebuiltZ28

I am of no help here, sorry, but maybe shoebox can help. This article talks about which valves are open and closed at what positions the balancer is at. “http://shbox.com/1/4th_gen_tech2.html#adjust_valves”

ridiqls

Thank you, I'll read the article.

I got curious so I just compression tested the #8 cylinder. Got 205psi with a very strong first crank. Thank god. If there's a problem with any of the cylinders, I just don't want it to be #8 because it would involve more troubleshooting and trying to get a hose on there sucks.

Injuneer

The problem is the LT1 harmonic damper hub is not keyed to the crankshaft, so there is no guarantee the arrow is accurate.

ridiqls

Injuneer

It’s not a balancer, just a damper, so precise assembly isn’t critical. No guarantee the assembly at the factory was perfect. Definitely no assurance if it’s been removed and reinstalled.

I had a “completely eliminates the Opti” system (Electromotive Super Direct Ignition/Opti-Eliminator) that affixed a 60-tooth crank wheel to the damper/hub. Electromotive required that the crank hub be keyed to insure accuracy. In their development work, they saw the unkeyed hub move under severe engine operation.

Aftermarket dampers, like the ATI that I run are always keyed, and the rim of the damper is marked a full 360°. We added a timing pointer to insure we could locate TDC and check timing with a light.

One way to check. Bring #1 as close to TDC on the compression stroke as possible. Drop a valve (remove lock/retainer) on top of the piston, and use a dial indicator on top of the valve stem to determine the range of rotation where there is no movement of the valve. TDC will be at the midpoint of that range. A degree wheel on the crank hub will help.

If the only reason you want to locate TDC is the leak-down test, you don't need absolute accuracy. Both valves have to be closed and the volume being pressurized should be small.

TopGear

My guess is that the plastic piece inside the hose is actually part of the valve, and it just stayed in the hose when it broke off the valve. That's exactly where mine broke a few years back (although it was the factory piece).

ridiqls

Thanks, I'll keep this in mind. Right now I'm going to have to finish the compression test and if it's off, I will do a leakdown test.

Actually just pulled the hose off right now and it's like a plastic lining inside the hose. not an OEM hose, just some jerry rig deal. The real parts just slipped right on no problem.




OK, I am in the middle of doing a compression test and my forearms are shot. They're all cut up also...

Driver's side took about 10 minutes total for all 4 plugs, no problem.

Passenger side, I have completed cylinder #8 and #4. I have been trying for the last hour to thread the compression hose into the spark plug holes of #2 and #6. They will not go in. I can reach and I can feel the hose inside the spark plug hole but I cannot get the thread started due to not getting the orientation right. Even tried using the compression hose adapter to make it longer.

Any tips on how to get that thread started? I don't think #2/#6 can be reached from the bottom. I might have to pull the alternator off for #2.

ridiqls

UPDATE:

Cylinder 1: 205
Cylinder 3: 195
Cylinder 5: 207
Cylinder 7: 195

Cylinder 2: 163. Wet Test: 195
Cylinder 4: 205
Cylinder 6: 120.
Cylinder 8: 205


So I guess that's bad news. Cylinder 6 was the biggest PITA to reach. I'm not going to bother wet testing that one or doing a leakdown because Cylinder 2 appears to be bad. Adding oil bumped it up from 160-165 to 195 (normal range) so signs point to bottom end/rings.

If I'm wrong in my assessment please let me know I'm still new to this.

Based on this diagnosis, I am guessing my options are to swap the motor, or rebuild.

Rebuild is tricky because I'm not 100% familiar with all the parts that the engine even consists of. But I will look at that book posted by Injuneer on building a Chevy motor and maybe look at the possibility of doing it myself. I've never done an engine rebuild so it would be quite an undertaking.

So far I've been quote for an engine rebuild from 2 different places:
Shop 1: $1500-1750, bench work only. If they pull and install the engine, around $2700-3000.
Shop 2: $2000 for rebuild. Re-Surface heads, check springs, 3 angle valve job (?) new seals, new rings, new pistons.
Mobile Mechanic: $1000-1500 to rebuild, not sure if it's labor only. Would include pulling motor out and installing



Thoughts?

ridiqls

Leakdown test confirms leaking from the rings. Will be pulling the engine to rebuild it.

Debating between a 383 or just doing a mild cam in stock from and porting heads.

DrewHMS97SS

From memory, the cost difference between a 383 and 355 rebuilds is negligible if the rods/crank are going to be replaced. Other than needing to meet some requirement in competition, I cannot imagine why you wouldn't go 383. If you are on a budget, and the crank and rods are good, then stick 355.

ridiqls

I'm not sure what the condition of the crank and rods are actually but I will once I pull the engine. The benefit to 383 is it passes smog easier from what I heard so you're able to go a bigger cam with cleaner emissions.

DrewHMS97SS

I have no clue about a 383 passing smog easier. For mine (ODB2) in Nevada, I just have to have gone through a full system cycle (roughly 25-50 miles, not show codes or visible smoke. More displacement typically equates to more HP as you are able to move more air/fuel.

ridiqls

I'm in the middle of pulling the engine, I still have to disconnect a few things, assemble the 2 ton engine hoist and pull it out.

But I want to do an estimate beforehand.

I'm looking to do just a refresh of the factory setup and add a small cam while I'm in there. I wouldn't even do the cam but since it's pulled, I might as well.

Based on the compression test and the fact that at least 1 of the cylinders has bad rings (air leaking through oil pan/dip stick hole during leakdown test)... what are the components I would need to do a basic refresh?


I'm thinking new rings and bearings and just cleaning and checking tolerances on the rest of the parts including piston heads and reusing them if they're still good. And new valve springs, lifters to support the slightly larger cam.

I also want to know what else I need to do because I might have someone local do it for me (shadetree mechanic who works on LT1s a lot) but I want to establish what needs to be done if I hand it over so I don't overlook anything.

Chimera96

^^...you are not really going to know what all you need until the block is stripped and mic. There may be some glaring visual signs (scuffed cyl walls). Machine shop may say just a hone and re-ring....or say they need to bore .030 over to clean up cylinders so you would then need new pistons. Crank may just need a polish...or a grind requiring -.xxx bearings. No real cost difference in bearings but some costs to grind crank down.

Then things like re-sizing the rods and installing new ARP fasteners or just getting new rods

So until the motor is completely stripped down and a machine shop has it you won't know the full depth of what needs to be done