MGB cylinder head not sealing on recon motor. Page 1 / 4

nzoomed, Jan 16, 1:22am
We have had alot of trouble getting a cylinder head to seal on an MGB 1800 engine. We initially thought the problem was because the engine had been sitting around for 10 years after being assembled and the gasket had squashed up and not sealed without being run. But the second head gasket has done the same thing with water spraying out between the block and head, we removed the head and sprayed a copper spray onto the gasket and re-fitted, this time it was better, but still we have noticed gas bubbling around the head studs and the engine slowly overheats, but not as bad as the first time, as the cooling system was pressurising under the gas pressure, but its still not right, both the block and head had been machined perfectly flat, so unless there is an undetected crack in the head, i dont know what the problem is, our torque wrench is accurate after testing it.

twink19, Jan 16, 1:55am
could be a crack in the head, have you had the head pressure tested

dave653, Jan 16, 2:03am
Do the studs have enough thread to allow for the thinner head! I had to shorten two bolts after having my head shaved the last time.

nzoomed, Jan 16, 2:10am
yes we are sure the bolts have enough thread, as we suspected that, i suspect there may be a crack, but for the head studs to be venting gas, suggests the head is not sealing.

elect70, Jan 16, 2:33am
Retightenafter initialrun & see if it improves ,good qualitygasket !

toyboy3, Jan 16, 3:45am
did you lubricate thehead nuts with clean oiland both sides of the washers when screwing the head down !

thejazzpianoma, Jan 16, 3:50am
No, not necessarily the case, all it takes is for the crack to intersect with the stud hole and those holes are of course a stress point which may even have been where the crack started.

kenw1, Jan 16, 4:37am
Before you start clean head and top of blockand check with crack detector spray, that might show up any problems.

Have you checked the head/block contact with engineers blue! without a gasket in place.Check studs for length against specs, may have been stretched.Are you torquing it up in the correct pattern and amount of torque.Have you tried a brand new head gasket !.

Last thought, have you tried a compression test on all cylinders, that might give a clue as to location of problem,

intrade, Jan 16, 5:02am
sounds like a shonkey rebuild to me. either the block or the head is banana shaped. engeneers straight edge will tell post 8 methode will also tell if its a banana

40wav, Jan 16, 6:47am
If its been sitting for 10 years, could it have rusted up inside and now the flow of water could be blocked by rust flakes etc which would then cause excess pressure which is finding its way out! Or the gasket doesn't have a hole where there should be one, causing same issue! Good luck mate, bloody frustrating, things like this.

nzoomed, Jan 16, 8:05am
Everything was clean when we had the head off, no sign of rust or anything, the whole engine had been chemically cleaned before assembly anyway. it sure is fustrating, i too thought about a hole missing in the gasket, but i checked that, and all holes were accounted for.

snoopy221, Jan 16, 8:10am
we will get them to check the block surface later, i don't have a precise enough straight edge to check it with.

Why oh why do you previously state the block had been machined!

snoopy221, Jan 16, 8:12am
Incidentally composite gasket!
or copper gasket!

petermcg, Jan 16, 8:17am
I am wondering what is the composition of the head gasket, like copper or laminated. Are you sure it is the right gasket, as one of a smaller cc engine may have a smaller pot hole and the piston will hit it,, causing this problem. Also it does not matter how good your torque wrench is,, it is in the way that you use it, When doing the final stage in the tourqe down, go over the nuts or studs several times, pulling up to torque and making sure that the bolt has stopped tuning. I also agree that if it is a thin head gasket that retourqe after a run is a good Idea, with the engine warm,, now you say it is overheating and pressurising,,,they are two different things,, the leaking gasket will cause the pressurising and blowing out of the gas and water,,,and the lack of water will cause it to overheat, this sounds like the case. I would assume your block and head are straight as you dont sound to unproffesionall,,,,so there is maybe something wrong with head gasket. There are other ways that can cause your engine to overheat but I dont think they apply here. The fact that you have seen water coming from the area between the head and the block,, also points to the head gasket,,, a crack would be more noticable by bubbles in the radiator, and I dont think they would cause the leakage around the head bolts and also the gasket area,, but if you do find a crack if its not in to bad a place you could maybe try some sealer,, also make sureyour radiater cap is OK.

smac, Jan 16, 6:18pm
Also check for flatness around the studs - the block can 'pull up' over time. Holes should be countersunk ideally.

petermcg, Jan 16, 8:34pm
Yes this is correct especially when the block has been decked. The studs may be stretched,, There is two origonal equipment part no for the head gasket, one is for engines that have been bored. And depending on which head is used the commpression ratio could be quite high. Are the OE washers still fitted to the engine.

supernova2, Jan 16, 9:19pm
Did you put antifreeze in the engine - if so that could be your problem.Cast iron head and block should be run in without antifreeze.

I'm guessing here but I would think the OE gasket would be a copper laminate.Is it possible that you have fitted it upside down (end for end)!

Have you had a Tkey test done!What happens if you run it wothout a rad cap!

Other option is chuck some irontite or chemiweld in and see if it stops.

smac, Jan 16, 10:08pm
Y'what now!!

nzoomed, Jan 16, 10:09pm
Copper gasket, the first gasket we had on it was a composite gasket though.

nzoomed, Jan 16, 10:14pm
The first time we had the motor going, it was bubbling in the radiator big time, after putting on the new gasket and spraying it with copper adhesive, it appeared to be OK, but after running the engine for linger, we noticed it leaking around the studs and very slightly out the front of the engine.

nzoomed, Jan 16, 10:17pm
Im going to remove the head this week and have a closer look, the way it leaks points out to a leaky gasket, but we cant rule out a crack until giving it a through test, i do wonder if the head studs have stretched.

kenw1, Jan 16, 10:39pm
Please let us all know what you find as the problem.

Never ever in my life heard that about running Cast iron block head without antifreeze, they would not last a day in the winter in the UK, and blown blocks do not make happy people.

wiseone58, Jan 16, 11:04pm
These engines had a reputation for cracked heads.

petermcg, Jan 16, 11:06pm
I am also going to suggest that you may want to remove the head studs from the block, when you have the head off,, some new head studs would be ideal here,,#do not replace them with bolts#,, if you remove and refit the studs,, maybe with some sort of sealer on the thread,, but when refitting them do not tighten them to much,, make sure that they dont bottom out as the expansion rates of the head stud and the block are different,, this can lead to a problem when the engine is warm and go away when it is cold. Dont forget to check for the countersunc affect on those holes, you should be able to do this carefully with a stone in a drill maybe. The copper sealant is a good idea for the gasket. re using the same gasket is risky but it is worth trying.

petermcg, Jan 16, 11:27pm
5 ft lbs is what is suggested for the head studs into the block. I could source a head gasket, there around the $45.00 mark,, but a set of good ARP headstuds would be 10 times that price, I dont know if this will be any help to you or not.

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