Hi guys,
I have a firebird that im trying to sell, it has the 5.7 v8 tpi. i know without a doubt that it has a blown head gasket on the passenger side. I know that when you do a head job you always have to have a machine shop rebuild and shave the heads before reinstalling them. However that would run me about $400 here locally and with a perfect running engine im not going to get more than $800 for the car. Is it really nessesary to have the heads machined, or than i just replace the head gaskets and put the heads back on?

 

Most mechanics would probably tell you that you have to have the heads shaved. But not always. I just did a valve job and lapped my valves and did not have the heads decked, and everything is fine. You only need to have them decked if they are warped beyond their tolerance. You would have to check them when you get them off to see if they need to be decked. I am guessing that with a blown head gasket, they may need it. But ya never know. Good luck!

 

Cool thanks, Is it bossible to lap the valves without removing the spring and retainer? In notherwards lap the valve while it is still fully assembled?

 

Only if you're Superman. You need to be able to spin the valve in the seat to lap it, and you need to open the valve to get the lapping compound in there.

On the machine work, Skirtz is correct. Head shaving or decking(done to the block not the head) is only necessary when the mating surface is warped beyond the tolerance. You will also need to make sure the head is not cracked, and that there are no grooves worn into either the head or block surface from coolant being forced through the break in the head gasket.

 

I definanly dont have the means of bringing the block to a shop to be shaved. I was always under the empression that the heads were shaved. I assumed the head gasket blew and that the heads were ok cause the car hasnt overheated in years. The car was just running normally one day when all of a sudden there was a lose of power and the engine shook when you gave it gas, but was still able to start and drive. when we pulled the #4 spark plug out a stream of water came out. So we figured the gasket just went. Are there special gaskets that could be used if the head is warped but still within tollerance, like a failsafe gasket?

 

I have actually had my heads decked as well. They can only deck a head so much though. no special gaskets that I know of. Just pleeeeease dont try to "double gasket" it. that wont work either.

 

How long has it been since this happened?? If its been a few years and you didn't drain the coolant, you probably have a rusted cylinder and the engine will need a complete rebuild.

 

nah, this just happen within three weeks ago. if i have to take the heads to a machine shop then i dont want to be ripped off but at the same time i dont want to look like i dont know what im talking about. besides lapping the valves, what esle would the macine shop do that they wanted $200 per head for? Can I just walk in and say i want the head ddecked and checked for cracks and that's it?

 

If there are no signs of oil leaking into the cylinders, there is no reason to have anything done to the heads other than to have them checked for flatness and cracks. You'll also want to have them check the valve seats to make sure they haven't recessed into the heads, and that the valve guides are not excessively worn.

If the heads need shaved because they aren't within spec then get that done. Same with the valve seats and guides.

Valves and chambers can be cleaned up easily enough at home. You can lap the valves yourself if you want, its not difficult but if they are sealing properly then there is no need to lap them.

One thing I would also do is replace the valve stem seals. They should cost less than $20 for the set IIRC, and are so easy to do that its one of those things that should be done any time the heads are disassembled.

 

I strongly believe she's sealing properly, cause even when i removed the #4 spark wire and injector, she can still squeel her tires running on 7 cylinders. When i pull the head im going to check for oil in the cylinders. Is there a old school way to check for warpage on the head?

 

A good METAL straightedge at least 2" longer than the head when placed on the diagonal and a good set of feeler gauges. Stand the straightedge on head straight across and select the feeler gauge that is the same thickness as the warpage limit for the head(I can't recall the number off the top of my head but its something small like .004" or so). Try and push the feeler gauge between the edge of the straightedge and the head surface at each end and between each cylinder chamber. Move the straightedge back so it runs across the middle of the chambers and try again with the feeler gauge. Then move the straightedge to the back of the cylinder head and across it diagonally in both directions and repeat with the feeler gauge. As long as you can't push the feeler gauge under the straightedge at all your head is fine. If it slips under the straightedge then the head needs shaved.

One other thing I forgot to mention earlier. If you do need to have the head shaved, then you will probably need to remove and replace the alignment dowels in the block. Shaving the head will misalign the chambers with the cylinders and prevent a good seal with the new head gasket. You can buy offset dowel pins to retain the proper alignment of the chambers to the cylinders. The machine shop should be able to supply you with the proper pins.