I'm (still) rebuilding my engine. The heads have been decked, but I recently ran into an external coolant leak through the head gasket whenever I reassembled the motor. I haven't pulled the heads yet to determine where it's leaking from, but I suspect that it may be coming through an improperly-sealed head bolt. If that's not the case, then the only other possibility that I can think of is a warped block.

The engine was overheated two years ago, so I know it's a possibility. A blown head gasket is also the reason why I decided to rebuild the motor in the first place. I told my machinist to deck the block when he had it, but he never did it. I overlooked that and never noticed until I was reviewing some pictures I took during assembly.

Is there an easy way for me to check if the block is warped with the engine still in the car? I had thought about using a straightedge with a light behind it, noting how much light entered through any gaps. Can I do it a better way?

 

that will work, but to get an accurate measurement use a feeler gage. if you have a a repair manual it should have specs in it for how much is too much.

 

precission straight edge and feeler gage, should be less than .005 or so out of flat. i'd say someone really dropped the ball if you wanted the block decked and never got it done at the shop and if you never noticed it when you got it. i always have a block surfaced at the very least when it's at the machine shop. if it's leaking without running i'd guess you have a big problem. did you use sealer on the head bolts?

 

Yep, it's leaking when the engine's off. Not as bad as when it's on, but it's still occurring. I don't actually get a puddle when the car is running because the coolant burns right off, but if I let it sit while warm it'll pool up. When cold, the coolant kinda oozes out.

Yep, I used thread sealant on the bolts. They're brand new bolts that came with sealant already on the threads... fairly thick, too.

I pulled the head today and I cannot find one trace of anything bad on either the head, the block, or the gasket. Everything looks just fine; the head gasket looks properly compressed, too. I did find that the head bolt closest to the leak was one of the easier bolts to remove, but that may have been because I removed them in the order I put them on (standard SBC pattern). I'm positive that I torqued them down evenly; I'm a nut about that and triple-checked. The Fel-Pro gasket I used also stated that re-torquing was not necessary, so I don't think the bolt backed out or anything.

 

shin or coated gasket? to leak cold you either did something wrong or have a problem. the fact that it over heated would lead me to suspect a crack or warpage.

 

yes was it magnafluxed???

 

did you check your frost plugs to see if one of them was leaking? Also check the plugs to see if antifreeze was leaking into a cyl.

 

I used Fel-Pro blue Permatorque head gaskets... I guess that would be a coated gasket? They were definitely not flimsy metal like some that I've seen.

The machinist told me that the block was magnafluxed and that there were no cracks... but I didn't actually see him do it.

The frost plugs are all new, but I looked at them and I never saw any leakage. The plugs look fine, too. I don't think that any coolant was entering the cylinders.

 

I took a few pictures of the head gasket. By letting them sit (dry out?) for a few days, coolant marks are now visible. This is a shot of the gasket at the location where the engine was leaking. It looks like the lower water jacket may be the culprit.



A shot of the head at the same location.



Finally, the block. It sure doesn't appear decked, does it?



I guess this rules out any possibility of a leaky head bolt. Could a warped block still make a gasket leak here, or is there a better chance of mechanic's (my) error? I also took a picture of another cylinder at the same water jacket. What is that black border around the compressed portion of the gasket? Is that coolant seeping out around the base? Notice how it appears to stretch into the cylinder. I was able to wipe the fire ring clean, but the head gasket remains dirty. The black thing on top of the water jacket area is just a piece of dirt; it wasn't on the gasket when I pulled it apart.

 

use the straight edge with feeler gauges in a grid pattern across the entire surface while paying close attention to the water passages the thickest feeler gauge that will go under the straight edge is ure warpage

 

Perhaps he has figured out if the block is warped or not in the last 15 years? You think? MAYBE?!? WTF.

GD