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Head gasket / noisy engine

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RandallRK

RandallRK

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My 100-4 BN1 recently started making progressively louder noise from what sounds like an exhaust leak. I was not able to locate an obvious leak so I started going over the various systems. I *think* (dangerous) that I located the issue but would appreciate help diagnosing it:

Plugs are sparking, timing is good, fuel seemed to be okay but plugs on #3 and #4 cylinder seemed slightly wet. As I was going to check compression/valves with the plugs out, I got 'shot' with a spray of coolant/water out of the #3 cylinder! I'm guessing this means the head gasket has failed. What I want to know is- would a failed head gasket ALSO be the cause/source of the LOUD exhaust/valve sound I'm hearing (or do I have to two seperate problems)? If it makes a difference, I recently flushed the cooling system and replaced the water pump/fan.

If it is the head gasket, I seem to remember Dennis Welch being mentioned as a good source for new one- is that the consensus?

Thanks in advance,
RK
 
Randall,

Water/coolant will not compress so you could be hearing a knock from the engine as it attempts to compress what liquid is in the chamber that will not leak back via the gasket or through the rings - yikes.

Pull the head, inspect the gasket for any tell tale signs, replace the gasket and see if that takes care of the noise you are hearing. The Moss or the DWM gasket will work, the DWM one is expensive but works well with a good flat block and head.

In cases like this always best to start with easy stuff like pulling the head off prior to any more involved things like pulling an engine. Focus on the head issue first the exhust leak may not be an issue after all.

Make sure all the valves are OK on the head and check the oil for coolant as well.

Good luck
Michael.
 
mjobrien said:
Pull the head, inspect the gasket for any tell tale signs, replace the gasket and see if that takes care of the noise you are hearing.
Click to expand...
While the head is off, I'd check both it and the block for warping.
 
The 100 head has a reputation for cracking. The head gasket may be leaking but you could have cracks in the #3 combustion chamber or the intake valve gallery. With the amount of water you describe, there is probably erosion damage to the valve seats in #3 as well.

While the head is off I suggest you take it to an automotive machine shop for magnaflux and if she passes do a valve job. Most shops can also pressure test the head to find internal water leaks.

Hopefully, you have just lost a gasket, but while the head is off, look further so you don't have to do it again.

Good luck!
 
With the head off I agree having it inspected and might as well have valve job while it is off...very rarely is it "just" a gasket..

Pete
 
Okay, I'll tear into it and see where it goes- I think the noise is likely from the knock as you suggest rather than an exhaust leak. Unfortunately, I had to run the car to evacuate it during the fires here in Santa Barbara last month (at least the house survived).

I'll check the other item while I'm in there as I enjoy doing it the right way. Thank you all for the advice.
 
One more question before I get into it- how best would you check for warping of the head/block? Would a simple visual inspection be sufficient or is there a more accurate method?

Thanks.
 
All you need for a quick and dirty check for warpage is a piece of machined bar stock that is smooth and true, a good machinists 12 " ruler would work for home purposes, and feeler gages down to .001". Make sure there is no rust or debris on the edges of the surfaces to be checked, put the straight edge against the surface and see if you can fit a feeler gage under it. Do this in lots of places and different directions to get a rough idea if it is warped. A machine shop probably wouldn't charge much to do it more accurately with a dial indicator set-up. You won't be able to just see this kind of warpage with out a few aids.
 
We saw this in the 100-4 we have in for repair now.The lore says you need to torque the head several times after rebuilding,get the Welch gasket it is a nice item,and have the valve seats cut for the triple angles as current cars have.Watch out to properly align the oiler tube in the rocker shaft or you will lose oiling.Welch also offers whitworth/sae head bolts,they are very desireable,and he also offers the proper nuts to finish the job.Not cheap,but they work perfectly and represent value for the $$$.We also added the Welch heat shield to this car,it is supposed to help hot starting.go ahead and order exhaust and intake gaskets,valve cover gasket and sealer gaskets for the fixing bolts.
 
Okay, a couple LONG months and I now have the head rebuilt and Welch head gasket, stud/nut set. I've heard to use Permatex gasket sealer with the Welch gasket but when it came, the package said to just use it DRY...

which way to go?

Thanks,
RK
 
When the manufacturer is well respected and has more Healey experience than almost anyone who reads this site, I'd be inclined to do what they say. E-mail them and ask why dry?
 
Just dry and make sure the correct way up, it's clearly marked.... I have had mine of and on three times :wink: works great. Make sure all the surfaces are clean. Ideally machined flat but I had used prior and it worked fine.

Good luck,
Michael.
 
Great advice, thanks. Sometimes it's just good to hear it! I'm glad I had the head checked/ valve job done (at the recommendation of this group), so I'll take this advice as well.

Thanks again for the input.

RK
 
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