GM 3100 head question

[Cougar281]

I've got the heads off the 97 Lumina parked in my driveway (appears to have been a blown HG or two); I had the heads checked and they measure out to .006" to .007"; spec calls for max warpage of .005". Think they are close enough to where once torqued down properly they'll be ok?

 

[Vrabel]

I would get them cut. They're prone for popping gaskets.

 

[Dave50mod]

You should resurface them and change the bolts

 

[Mike]

Head gasket leakage prone, new to me. I've only ever had a problem with intake gasket leak at the head to intake water port. You know, the neoprene grove in side the plastic with the plastic cracking out. As far as clearance? Who measured and how were they measured?

 

[Vrabel]

did a bunch of them over the years when I used to work at a shop. good idea to replace the little coolant lines under throttle body while apart

 

[Cougar281]

The story behind the motor is the car was "aquired" by my friend's MIL from her family; They had done some kind of engine work, and I'm guessing HG's where done, since when I pulled the heads, only about half of the bolts felt as tight as they should have been; Anyway, it came into my hands to try and work on after the upper radiator line broke off, spilling all the coolant. Originally, I thought that was all that was wrong, until I got the new radiatior in and had combustion gas in the cooling system pushing coolant out the overflow.

Replacing the bolts is a forgon conclusion; My main concern with resurfacing them is once that's done, won't I have to shim the rockers to maintain proper clearance?

 

[Vrabel]

no, not necesary

 

[Cougar281]

They where both high in the middle.

 

[Mike]

If they were both the same, this makes me wonder if the straight edge is really straight.

I'd be more worried over a cracked head than a leaky gasket causing the pressure in the coolant reservoir. Rockers are adjustable so you're good.

 

[Cougar281]

How can I tell if one is cracked? I've looked them over and nothing stands out. Like I said though, when I removed the head bolts, about half them took almost no effort to break free; other heads I've removed, all bolts required roughly the same effort to remove and two or so sharp cracks accompanied each bolt breaking free; the ones that required little effort didn't "crack" when I broke them free.

 

[Vrabel]

did u see any obvious signs where it was leaking? any trace marks on head gaskets or intake gaskets? is there coolant/oil mix? or just excessive coolant pressure?

 

[Mike]

How can I tell if one is cracked? I've looked them over and nothing stands out. Like I said though, when I removed the head bolts, about half them took almost no effort to break free; other heads I've removed, all bolts required roughly the same effort to remove and two or so sharp cracks accompanied each bolt breaking free; the ones that required little effort didn't "crack" when I broke them free.

Before you pulled them, it would have been cool to check the torque of each one. But, torque-to-yield bolts are pretty fussy.

Most common crack locations are between the valves ( not many that I've seen only severe overheating ) and from the combustion chamber to coolant passage ( should see a hair line crack ). One I have in the scape pile has a crack from exhaust port just under the valve to coolant passage. Clouded the sky with sweet coolant smell and white smoke.

Best thing to do would be to have a machine shop clean and check them.

 

[Cougar281]

Here are hi-res pictures of the gaskets; I'll admit, I really don't know what I'm looking for, but in the first picture, the area that I circled sure looks like evidence of of combustion gasses getting out of the HG. The location of the "soot" pretty much corresponds to where the "loose" head bolts where.

I know the "best" thing would be to have them machined, but is it possible or even likely that they'd be ok if they don't get machined? With the thickness of the HG (Looks to be around 1/16"), I'd think it could absorb .003" (if they where .005" or less they'd be "ok", but being between .001" and .002", they're out). We pretty much want to get the car running and wash out hands of it.

 

[Vrabel]

personally, i'd send them out check and shave. and if high milage and keeping, replace valve seals. they're in the head set anyway.

 

[Cougar281]

Don't plan on keeping it for terribly long; Just want it running decent for as little $$ as possible. I really don't know how many miles are on the motor as it's not the original.

 

[Mike]

Don't plan on keeping it for terribly long; Just want it running decent for as little $$ as possible. I really don't know how many miles are on the motor as it's not the original.

Do you plan on buying new head bolts? All the money you spend, no matter how little, will be a waste if you don't clamp the heads properly.

 

[Cougar281]

Do you plan on buying new head bolts? All the money you spend, no matter how little, will be a waste if you don't clamp the heads properly.

Of course; As I said in an eariler post, replacing the head bolts was a forgon conclusion. Without machineing the heads, it'll cost about $200 to put it back together with all new gaskets and bolts.

 

[Mike]

Of course; As I said in an eariler post, replacing the head bolts was a forgon conclusion. Without machineing the heads, it'll cost about $200 to put it back together with all new gaskets and bolts.

Oops, I remember reading that. Sorry

Good luck.

 

[Cougar281]

Ok, got the heads resurfaced. One question on installation. Mitchell says to "Apply GM Sealant (1052080) to head bolt threads". What kind of sealant is this? Locktite? RTV? Is it nessicary? Last two head installs I did (4.6L Ford and 3.8L Ford) didn't get any sealant on the threads and both are still running strong.

 

[Vrabel]

loc-tite thread sealer, looks like pipe dope, same stuff.