I just had the short block of my 1990 4.0 rebuilt due to cylinder damage from a leaking head. The shop to take some material off the deck due to warpage, probably from overheating. It's now nice and flat, and I was test fitting the new heads on it.

I found that if I set the heads onto the cylinder with no gasket, the tops of the pistons just touches the heads, enough that the heads lift just a little. So the pistons poke out of the deck a little, but I haven't measure that poke yet. What's the best way to measure this?

But if I put a gasket on the way it should be, there is no contact. I haven't torqued it down yet, so I don't know if there will be contact after the gasket is compressed.

What is the minimum clearance I should have between the top of the piston to the head mounting surface? I guess I'll also have to find the compressed thickness of the head gasket. What are my options if I find insufficient clearance with the head gasket? Shave the tops of the pistons?

thanks in advance

 

Slowly building it up in between interference from work.

With the heads and lower intake manifolds installed, I tried to run a leak test of the cooling system. I connected a heater hose between the two heater nipples, with a presta valve adapter for a bicycle pump, and connected hoses between the radiator and the engine.

I found leaks in two of the hoses, as well as the radiator cap. But even after replacing those, the system still could not keep pressure. I guess the dynamic seal on the water pump must be "weeping" , and I wonder how much is acceptable.

Right now, the air pressure drops to a few pis in a matter of minutes. I'm worried that under pressure, the coolant would do the same.

 

I guess you could raise the pistons one at a time to TDC, then slide a few tapered Popsicle sticks in the gap until it's more or less even, and check the gap with feeler gauges.
The V8 guys seem to like .040" as "quench" distance, so I suppose this smaller engine could get away with .030"?

 

The head gasket compressed height is right around .04", so I think there's enough clearance. thanks.

 

Hope the experienced engine experts can weigh in on this.

Investigating a bad knocking sound, fearing the worst being a rod knock. Dropped drive train, pulled engine, dropped oil pan expecting to see shards of rod bearings, but only saw a little bit of metal dust in the pan. So checking the rod bearings found most of them looking new, but the bearings in cylinder 4 seem to have a little streaking in them (right side of picture):

https://photos.google.com/share/AF1Q...Zycm5RNTZTeWZB

I can just catch my finger nails on the streaks on the journal. Is this something I should worry about?

C1 bearings look much smoother (left side), though the journal also has a couple of lines in it.

 

I don't think the minor journal damage is the source of the knocking.
When dismantling a high mileage engine it's common to find crankshaft damage like this, which might have been present for twenty years. Consider it a "high performance oil retention groove".

 

Thanks Beanscoot.

The cause of the knocking noise was something really stupid, and if I had seen it earlier, I would have save myself many hours of pulling and disassembling the engine, then looking forward to re-assembling and re-installing the engine.

This was part of a conversion from automatic to manual transmission. After seeing that the bearings were fine, I started looking to see what else would have made such a racket. I say a lot of metal flakes on the front side of the flywheel, so I looked at what it could have been grinding down. It turned out to be the aluminum cover plate between the engine and transmission.

https://photos.google.com/share/AF1Q...Zycm5RNTZTeWZB

There is a contoured passage pressed into the plate that protruded far enough to touch the flywheel. So I plan to cut out a chunk of that to clear the flywheel. It would be easier that trying to find the manual version of that plate.

 

Interesting. I have a chewed up aluminum separator plate from a small block with nasty smearing of the metal, probably from the same cause.

 

Well, I found the actual cause of the knocking noise I heard on my freshly rebuilt engine. It was one of the NEW lifters I bought to replace the originals. Its plunger had completely collapsed, leaving a gap of over 1/8" between it and the pushrod, or 3/16" between the tip of the rocker and valve stem.

The top of the plunger is a little cup that the pushrod sits in, and it has small bleed holes. It sits on top of another little cap with a ball restricter, which sits on top of a spring that pushes against the bottom of the plunger bore. I saw this with the other lifters that were not jammed, but on this one, the lower two parts were stuck in the hole. I'm guessing this happened shortly after the engine was first started, as the noise did not start immediately with the engine.

I should have been wary of the parts, as in the set of 12 new lifters that I bought, 4 of them would not slide into the lifer bores. It seemed the locating "nub" on the side stuck out too far to fit into the bores, so I ended up re-using some of the old lifters. Now I'm going back in to replace all the new ones with the old lifters.

The brand of the new lifters is Evergreen, made in Taiwan, bought as a part of an engine kit kit from eBay. Never again. I will waste 2 set of head gaskets and bolts because of this.

 

Nowadays just about everything new is suspect. Although typically Taiwan made parts are actually better than most.

I had a Toyota camshaft and lifters reground locally a few years ago. If the original stuff can be reused or refinished it's going to be better!