Does anyone have any experience with cracked heads? '91 4.0l

just got heads off this afternoon, basically looked good, head gaskets looked good too , no burn throughs, etc. No cylinder ridges.

There appears to be a crack between the valves of one cylinder, haven't removed valve yet but it looks like it goes to the valve seats.

Are these things repairable? Is the head junk? cylinder looks like it was burning fine, as a matter of fact, everything (except the crack) looks fine.

Hydraulic lifters look fine and are firm. No visible cylinder wear, pshrods and rockers look fine.

ken

 

Both heads on my 94 were junk cracked everywhere. Couldn't see all the cracks until we glass beaded them. The valve seats were into the heads. You will have to get another head. We had vacuum leaks on the intake that might have caused the head damage.

Dick

 

I have had to change my heads twice and replace head gaskets once, both times I got heads from wreakers yard, the heads I have on now have done about 60th without any prob's I think the first set I got were maybe bad as well I just did not see hair line crack between the plug hole and vave port. If you get heads from wreakers yard check them very carefully before you fit them.

 

have heads hot tank dipped and cleaned...then get glass beaded or magna fluxed...there is also a dye followed by developer method for defect location...saves lots of frustration and extra work
common problem on these new thin cast engine designs

go to one of the local shops that your local racers go to...guarenteed quality work
must have local 1/8 mile or 1/4 mile oval or flat track dirt racer tracks there...

 

Hi Ken:

This is going to be a long post, so bear with me.

1) The hydraulic lifters can be disassembled and cleaned.

2) The pushrods and rocker arms, if not scored, can be reused.

3) The head bolts must be replaced with new ones for the 4.0L

4) The camshaft, if not too worn out might be reusable.

5) The timing set & chain should be replaced since they are cheap.

Now, we get to the heads themselves. The 3.0L heads are very much bullet proof, but not the 4.0L heads. The 4.0L is just a 2.8L bored out to the max, so the metal between the intake and exhaust valves is extremely thin and weak. It's a design problem for which there is no cure that I know of.

When I rebuilt my 4.0L, I disassembled the heads completely down to the bare heads and took them to the local head shop to have it inspected, shaved, and the valves cut. The owner of the head shop showed me the same cracks you are talking about, i.e. a hairline crack that bridges between the intake and exhaust valves. Three of six cylinders had the same crack. He told me that he bought more than 20 heads from the junkyard, and all of them had similar cracks. On his own Explorer's 4.0L heads, the same cracks were there even though it has never been overheated once in its life. He said that he can weld them for me, but that would be a complete waste of money since the crack would probably reappear after a couple of thousand miles anyway. By what he said earlier about junkyard heads, that would be a waste of time also. His advice to me at the time was not to waste money on "new heads" since they are most likely just welded and rebuilt versions of the same cracked heads. So I took his advice and paid him $80 to have both heads cleaned, shaved and the valves cut. I then installed the heads as is, cracks and all. It has been about a year and a half, 20,000 miles later, and I haven't yet had any problems. The van has plenty of power, good gas mileage, no coolant loss whatsoever, no oil burning, not a single problem.

I had the first CA emission test done about a month and a half ago, and here are the results:

At 875 rpm, HC (Max:100, Ave:17, Meas:8), CO (Max:1.00 Ave:0.00, Meas :0.00)

At 2675 rpm, HC (Max:170, Ave:13, Meas:6), CO (Max:1.00 Ave:0.10, Meas:0.00)

I'm not going to advise you to ignore those cracks, I'm just saying that they may be more benign than we think. However, if you intend to do any racing (ha ha) with this van, you'd better get real new heads, not the rebuilt ones. There may be some outfits that make sturdier versions of thease heads than the OEM ones.

Good luck and have fun.

 

covers 4L, when valves out check intake valve seat pads for cracks
http://www.babcox.com/editorial/ar/ar40123.htm


new for piece of mind on long trips?

 

Dear Copper,

Thank You very much, your info and insight was what I needed. Did your cracks go into the valve seat area?

Ken

 

Hi Ken:

Yes, they did seem to go into the valve seats area, but only slightly near the outer edges of the valves, not all the way across.

I was told by the guy that you can have them welded and then grounded off. I remember reading somewhere on the web that they can even be JB-welded, but don't hold me on this as my memory ain't what it used to be. I just don't see how JB-weld can hep in situations like this.

If you feel uneasy about it, I would recommend a set of new high quality aftermarket heads, not remanufactured or rebuilt. I believe that this is one of those rare cases where aftermarket products might be better than OEM. But don't ask me who makes them, since I have no idea. Best thing to do is to talk to your local head shop. If you are willing to share a couple of brews with them like I did , they might suggest something more useful than all the useless dribble I'm giving you here.

Good luck.

P.S. Make sure you check the exhaust manifolds for cracks also since you indicated in ealier posts that they could be part of your noisy engine.

 

Dear Copper,

Sir you have been very helpful, thank you everyone else too, every post has helped me here.

Ken

 

Dear Copper,
How did your cam chain/system look??

ken

 

Ken has finnally figured out he has a cracked head!

Nothing else to add, just thought the title was funny.

Sorry to hear about your 4.0L head issues.

 

Hi Ken:

My camshaft looked great, so I reused it. The timing set including the chain and gears was in the order of $30, so I replaced them just for the heck of it.

All the bearings were in great shape, so I left the camshaft bearing alone since they can be a pain to remove and install. I did replace the main and rod bearings since they are cheap and I'm already there.

The pistons are in good shape and the cylinders hardly shoed any wear at all, so I simply replaced the rings with STD sized cast iron rings. My theory is that soft rings can be worn out and replaced later, but cylinder walls are not.

As I said, the cost of the works on the heads was only $80, and everything else is rather cheap, except for the full gasket set, which costs me in the order of $150 (I'm only quoting from memory here). My final tally was between $350 and $400 for that entire motor rebuild. I thought about using all new parts, but it was an old van, and I only needed it to go for another 100K miles Did I ever mention how cheap I am?

My advice is to get the thing running as well as you can, within limits. These are old vans. There is no need to pump thousands of dollars into a van whose blue book value is less than what you are putting in. Did I ever mention how cheap I am?

I do have to admit, by the time I was done with the front end, the rear end, the engine and the tranny, it costs me close to a thousand dollars, but that's within my limit. Did I ever mention how cheap I am? And I'm willing to take that van anywhere because I know I didn't put anything on backward, unlike those drunks at the factory

 

I used some spray crack detector that I found at work (I am a maintenance mechanic in a hospital) it came in two parts a can of red stuff you spray on then let it sit for a while, then a can of white stuff, the red disappears after a while but when you spray on the white it show's up any cracks in the metal even hair line cracks, sorry but I can't remember the name of the stuff and I am not sure you can get it in the local stores, but it really was very good the last heads I got from junk yard showed no cracks at all and I have done about 50 or 60th on them with no problems, touch wood.

 

local machinist supply store will carry the two part dye fracture develper....also carry magna fluxing equip..

 

hey thanks 4wdr, do you know who makes it and what name it goes under, I used all that I found and my boss can't remember which store house he got it from, I looked though the sexuer catalogue and the granger catalogue but could not see it.? I am a bit in the dog house for using it all on my own projects.