Over heated = blown head gasket = warped heads ???

[Astro4x4]

So I overheated the engine taking the kid to school in London yesterday. Seems like the rad has/had some blockage, so I gave it a good flush and got some redish brown gunk out (love DexCool) Now here's the problem - it runs great and smooth when cold but once warmed up to operating temp, it feels like I'm losing a cylinder and get a nice hot coolant smell from the engine bay. Good news is the exhaust doesn't smell sweet or blow a bunch of condensation. I'm going to do a compression test, etc, etc, and figure I probally at least fragged the intake gasket. I changed the oil soon as I got home and figured that between the synthetic oil and the oil cooler my engine was saved.
Now, should I replace the head gaskets when I'm in there, even if the compression test says I'm good.? I'm leaning towards, "yes" and check head and deck for warpage too. So what say you? Anyone have a similar experience.

[Someone]

sounds expensive... what year is the van again?? a motor swap may be cheaper and easier than head gaskets.. I would start with the intake gaskets as they are less than half the job of the head gaskets... just check your compression and make sure there is no coolant in your oil. no matter wich gasket is leaking if it is causing it to run rough it must be burning it... I think?

[Smiliesafari]

If you're up to the head gasket job it's not a bad idea. Especially if it's a high mileage motor. At the same time you can check for cracks.

[Astro4x4]

Well, I'm in. The good so far - head gasket on drivers side is (was) good with the exception of a serious build up of gunk around the coolant holes. Cylinders still have a nice cross hatched pattern in them for the most part. Not too much sludge on the head.
The bad - one of the rockers was tweaked to the side so that instead of contacting the valve on center between the guide shoulders it was riding on the shoulder. So 1 screwed rocker and 1 screwed intake valve. We'll see what tomorrow brings when I pop the passenger side head off. Glad I decide to rip the heads off to od new gaskets after seeing the coolant sludge build up that blocks some of the smaller holes in the gasket. I'll try to get the pics uploaded later tonight....I need a hot shower and a cold beer right now.

[GEJ]

While you have the heads off-might want to consider taking them to a machine shop to check the valve guides,do a valve job,fresh valve seals,and check the valve springs.I had a yr ago a guy trying to chase a drive ability problem on my van tell me about bad valve springs.Told me he talked to a service manager at a Chevy dealership that had the same problem Ran fine while cold,but from time to time(not always) it wouldn't idle worth nothing once hot.No codes either.Well the service manager did compression checks and never found anything wrong.They took off the heads and did a valve job and put on fresh valve springs.Problem never came up after that.Didn't find anything with the valves during that valve job.Service manager figured that the van had a bad valve spring in it and the spring didn't have enough pressure as long it was hot.While they tried to check that with a compression check,the time it took to get the spark plugs out allowed the spring to cool enough to show good.Said he found a second van and did the same thing with a valve job and new valve springs to repair that one too.The manager thought it might be possible the 4.3's had a run on bad springs.

Point being once you overheated yours,it could involve the valve springs/valve guides-etc and you don't want to go thru all this work without being sure everything is in good shape.Taking longer to get it back together and costing just a little more,but done once.

[Astro4x4]

Passenger side head was clean as a whistle for some reason, very, very little sludge on it compared to the driver side head. I think perhaps the engine had some work done on the pass side head shortly before I bought it, and since I've been running synthetic since the day I brought it has stayed really clean. The springs, retainers, even the machined surfaces are still nice a shiney, almost like new. Found a burr on the stem of one exhaust valve and another exhaust and an intake valve with a pit in the top of the stem, but mysteriously the rocker arms for all are in mint condition.
Looks like I had a wee bit of coolant getting into #4 cylinder, however the fire ring on the gasket is still in good shape, so I'm thinking warped head
Well, going to take them to the machine shop to have them checked for flat and Magnafluxed for cracks.

[Mr_Roboto]

You can do a rudimentary check with a set of feeler gauges and a metal straight edge. It will probably even be visible to the naked eye. Can check the block this way too.

[Astro4x4]

For the love of God, don't do the head gaskets with the engine still in the van !!!!

[safariobsession]

For the love of God, don't do the head gaskets with the engine still in the van !!!!

Pretty tough eh? Backbreaking, no leverage! It's definitely a 2 person job. Resting the head on a wood board (1" x 4") on top of the block works pretty well so you can slide it around before setting in it in place.

[SoCalli V8]

I recommend having a complete valvejob done while the heads are off, then you will have the comfort of knowing that they are in good shape when you put them back on, preventing you from having to do this whole PITA job again, plus you may pickup some lost hp also......

[Astro4x4]

Had the valves and seals done while they were in for hot tanking/ crack check. Guy made me an offer I could not refuse. This will however be the last time for this engine as I pick up a '97 350 next week. If I had not had my 4.3 problems, I would never have run across this 350, so sometimes things aren't as bad as they seem.

[SoCalli V8]

`97 V8.....<< CooL

I didn`t know your whole engine / transplant situation......

[Astro4x4]

Had a 350 a few years back that was ear marked for my '90. Sold it to neighbor kid that desperately wanted it for his pickup ](*,) But all in all in the long run I'm happy 'cause now I've got a roller block and Vortec heads. So after a freshening up, and the weather is warmer, I'm stuffing the 8

[Astro4x4]

Compression is 155 give or take on all, new A/C plugs and cap and rotor, all spark plug wires Ohm out ok, distributor is referenced to cam properly, 2 new O2 sensors because one was dead (no codes?) and STILL, darn thing is throwing a P0301 and idling like a paint shaker. Haven't had cooling system pressure checked, but temp is fine, it isn't using any coolant at all and the top end is all new gaskets. So what's next? I'm leaning towards an injector problem. ](*,)

[canadavan]

Check the coolant temperature sensor. On my 90 it is in the drivers side head about halfway back...