Topic: Blown Head Gasket?

[donkeykong]

I blew a head gasket ...now I am going to replace the gasket and also get the head resurfaced.  I am thinking abot getting the head completely redone, Since I am going to have it off and all.  My question is I have been hearing conflicting opinions.  Some say do it and some say it might mess up up the blcok and piston rings .  So should I just get it resurfaced and put it back together or get the works done.

[krawlr]

I've heard of it happening on high mileage cars. I've done more head gaskets than I care to remember, never happened to me. Resurfacing the head is the big risk factor anyway, it raises the compression. I would inspect valve guides and seats to determine if the head needs gone over. If it's been overheated it should also be checked for cracks and I'd replace the valve guide seals.

[BigMike]

Yes, krawlr knows his stuff, and I was going to ask how hot the engine got?

If it got into the red, then it might have warped...

Mike

[donkeykong [OP]]

I saw it start to rise. I was on the freeway but there was no traffic, so before it got to the red I killed it and cruised to the side.

[BigMike]

Well, regardless you should check it with a straight edge and if its more than .002" warped, then resurface it. The book calls for .004" or more I think, but Marlin says anything over .002" he would resurface it.

Mike

[donkeykong [OP]]

Is there any way to visually check the piston rings when I remove the head.  Also does marlin do rebuilds of heads or maybe the shop next door, and what would be the price on it.

[BigMike]

No you cant see the rings, but you can check the cylinder walls which can give a good indication of piston to wall performance.

If the intake/exhaust side of the walls are smooth and look polished, but the front/rear side of the walls look normal - sort'of rough, no real patterns - then you've got either lose pistons or your pistons have gotten very hot. In either case what's happening is piston to wall interference. This lets you know how hard the engine has been run.

I suppose that if someone has let the engine detonate for many many miles under big work loads - like towing a trailer up hills - then the piston rings could be beating their way out the tops of the pistons and will eventually break the piston cap and you'll have ring deposits bouncing around through your cylinders. This is what happened to my Stage One engine.
Also, another way to check for long term detonation use is to pull the
oil pan and inspect every connecting rod bearing. If the bearing have pits on the bottom and the top of both bearings, then the piston has been experiencing violent combustions which is typically due to predetonation. If they have pits, just replace them. I mean if its running ok, you dont need to rebuild any thing. Just get it all back together and retune the whole engine. Make sure the timing is ok to prevent any future detonation. I've replaced rod bearings on many engines that were just beginning to rattle and they are still running strong.

I've attached a picture of my piston that gave way after my redline in 5th gear at only 11psi boost with a passenger in my car doing 146 MPH in the diablo mountain range outside of paso robles. Later that week one morning my engine sounded like rocks were in the cylinders. :sob: Death to the original HIPSI...  

[BigMike]

Here are the ring deposits that I recovered from the front end of my catalitic convertor.  :unhappy:

[BigMike]

And here is what the cylinder looked like from the top.

The stamp marks are from the ring pieces getting smashed between the head and the piston. And you know what, I had these stamp marks and 2 other pistons!! But this was the only bad piston! So somehow the deposits either back tracked into the intake manifold, moved to a neighboring cylinder, bounced around a bit, and then exited the engine. Amazing. At the time I had a real P.O.S. TRD 4-2-1 header that had long pipes so theirs no way they could have gotten sucked back in from the exhaust side. I think like cylinder #4 was untouched, but #2 and #3 had simular markings in them. Incredible!

[donkeykong [OP]]

Thanks for the Info. I am going to take the head of tonight and check what everything looks like and If nothing looks to bad on the block I will get the head done.

I will try and take notes on how to remove and install the head and write up for the *Tech Guide* forum.

[79coyotefrg]

 :smack:i hate it when that happens,  

if you have the head decked only .005" it shouldnt move your compression ratio more than a couple of points,  like from 8.5 to 8.7 or 8.8, now combine that with  a taller piston and you'll be buying 90 octane gas

[BigMike]

You know its all minimal if nill. Besides, your leaky valves drop the compression to 8.0 anyways. who knows-

static compression is alot different from actual use