Dega500

Hey guys,

I bought a 91 L98 engine with approximately 78,500 miles to use in my 80 model Vette TPI swap. I'm wanting to look things over good and at least replace the seals and gaskets before dropping her in but I can't get the darn cylinder head off. This is my first time working with aluminum heads and I'm just a little afraid to use brute force to try to get it off. I've even tried lifting the engine assembly (just enough to put a little tension on it) while attached to the head with my cherry picker and smacking around on it with a dead blow hammer and it wont budge. There aren't any hidden or secret bolts that aren't obvious that I may be missing are they?

Any suggestions are welcome!

Thanks, Mike

cv67

Sometimes the bolt near the oil drains down in the corners can be missed
Count how many bolts you have out(should be 17 ea I think)
If youre positive there are none you missed you can stick a prybar down a port and lift up you wont hurt it

Dega500

Thanks, I took 17 bolts out of it. I have used pry bars in the ports on iron heads before, just scared to use on aluminum.

Masterspykiller

Wow, I have a 1991 L98 and I removed the heads myself awhile back.

Finding the 17 bolts (yes, exactly) required me to peek down into the end chambers for the last 2, but after those were out, it did not require enormous effort to separate them.

I liked your idea of lifting the unit from several bolts into the head so the weight of the block exerts force on the adhesion. I would ADD my suggestions to this method of exerting separating force.

I am just throwing out some ideas, I have never had this situation myself:
Is there some kind of solvent (brake cleaner or carb cleaner?) that you might try to spray around the edges of the head/block joint to seep in and maybe loosen whatever adhesion exists? I realize most RTV and gasket making products are immune to petroleum solvents, but that's all I can think of.

Can you let the block sit in direct sun for a few hours? If it is hot enough, the aluminum and steel will expand it different rates, without the bolts in, it just might be enough to "crack" whatever kind of seal has been created.

I also realize you want to re-use the block and heads without re-machining the surfaces too, so you don't want to scratch the milled flat surface of the heads (less likely you'll scratch the block, but possible). Maybe a thin razor knife and carefully work it around the complete circumference of the head to separate it from the block? Even if you can only insert it 1/4", collectively that might release enough of the adhesion for gravity to overcome the rest.

I do NOT suggest using a propane torch to "really" heat up one or the other because you may have fuel in one of the cylinders and/or oil in the block, the extreme heat in one place might warp the head or block, and I just don't know enough to suggest that risk.

With respect to CuisinartVette, I would use the pry bar only as a last resort. Those aluminum heads are not indestructible.
Good luck!
M

ghoastrider1

The time honored way to break loose a head is removing all the bolts, then using the starter motor to turn the engine over.Compression does the rest.Its always worked for me.Problem is, I have never tried it on Alum. heads.

cudamax

Both are stuck or just one? I'd say check and make sure you took out 17 of them. Blow some compressed air thru the spark plug hole. One of those with a rubber nipple and do it in a cyl that has both valves closed and do it with the motor hanging on the head on the engine hoist about an inch or or less off the ground over a skid

Dega500

Thanks guys, I had already thought about cranking her over. Problem is, engine is on an engine stand with the flywheel removed. I will try the compressed air although my compressor is pretty weak. I have a brand new one ordered but it's still a week out. Won't hurt to try at all though.

DanielRicany

Try hitting the intake side of the head with a rubber mallet.

Dega500

Thanks but tried that. Maybe I just need a bigger hammer!!!

DanielRicany

Maybe somebody used steel shim gaskets on it....

cudamax

Get a Hair dry or 2 of them and start heating up the head. Get it hot enough, it will pop

Dega500

Thanks for the ideas everyone. We'll get her off soon!

DanielRicany

Pull the engine and throw it off a cliff. It'll probably come off then...

nutz4c4

Probably stuck on the dowel pins..Steel pins into aluminum,maybe a little bit of corrosion.Agree on the pry bar method..just don't go all apechit....on reassembly use a little anti sieze on the dowels.

Masterspykiller

DAMN! Two days I ago I installed the heads on my new build. Didn't anti-seize the dowels. GREAT SUGGESTION ..... for next time.

LANDSHARK1

There are no hidden or secret bolts holding the aluminum head on so look again and make absolutely sure that you have all the bolts out. I'd say chances are good that you missed one.

Once you are absolutely certain, get a wooden handle like a long hammer handle and coming from the side of the other head, opposite the one you are trying to remove, leverage the head (you are trying to remove) from below using the other head or front end rail (where the intake manifold seals) as a fulcrum or pivot point. Push down so that the head pops up and off the dowel pins.

I had the same problem as you before and that's what it took to get the head off. Keep in mind that although they are aluminum and way lighter than iron heads, they are not featherweights and in some instances, you may need quite a bit of force to break the initial seal.

You can also carefully stick a wood handle (I like wood on aluminum...less chance of damage) into one of the intake ports, but I don't like this method for fear of bending a valve stem.

Also, is this just on one side or is it both heads? If it's just one side, you likely missed a bolt.

Dega500

Thanks everyone. I'm just working at getting the one head off right now. If I can't get it off with an amount of force I feel comfortable with I'm going to bite the bullet and set engine back on the ground, bolt the flywheel back on and try to pop off with compression.

jake corvette

Use the air compressor method and introduce compressed air into the combustion chambers and chances are it will break loose. If it were me I would install a couple of head bolts screwed about three turns into the block to prevent the cylinder head from flying across the shop once it breaks loose.

If that fails when using the average home air compressor which generates about 100 PSI, then you might consider using a grease gun instead. Get or fabricate an adapter of some sort so you can introduce grease into the combustion chamber through the spark plug opening. Most grease guns will exert thousands of PSI - seen 10,000 PSI advertised - and that will most definitely get it loose.

The grease gun method also works well in getting frozen pistons to move in the bores.

Be sure and wear approved eye protection.

Get back and tell us what you did.

Good luck -

Jake -

DanielRicany

I also just installed my heads right before reading about the anti seize... If they get stuck, I'm going to throw it off a cliff like I said earlier. Haha.

DanielRicany

So, are you saying to use the grease gun with no grease in there or with grease? If you're talking about grease... well... that'd be a lot of grease...