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MGB-GT Engine Problem 74MGB GT

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Well???? What happened??? Did it run?? Any compression???
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<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Gary Lloyd:
Well???? What happened??? Did it run?? Any compression???
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Yea, the suspense is killing us...come on Jim, inquiring minds want to know!
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Bruce
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I'll wade in here..I'm Jim's son and have been involved here in this snafu.......While i'm a Rover guy this is the first Mg i've ever worked on.....We got the car running in the summer for first time after sitting 7 years...The cylinders were honed and the valves were lapped and rings put in...The old valves and pistons were used....However the ring gap seemed too tight and they were filed but obviously must have been too big...The motor ran good but burned oil so while doing the clutch he decided too fix that oo.....He removed the ridge from the cylinders and put new rings in again.....The cam timing and gear was never touched.....He relapped the valves and put it all back together like the first time and it didn,t start....We checked everything in the spark and fuel dept. and were stumped.....Out of desperation the compression was checked and we couldn,t believe it.....It had previously from the summer motor job been in the 100+ range across the board.......We rechecked the valve timing to no avail then roughened the cylinder bores with wet sandpaper and put it all back together without the carbs on....We did get about 5 pounds more but still the best is 40 lbs...Both middle cylinders are 25-30....He then took the head to be planed after seeing it wasn,t level and let the machine shop reface the valves and now since getting it back and retrying have no more sucess.....Still in the 30 pound range ........However he poured kerosene in the ports and the valves are leaking .......He's going to relap them again .....
I can't see how without catastrophic problems the engine could go from fairly good compression across the board to next to nothing.....

Bill Robertson

Love my Rovers
 
First off if the machine shop ground the valves, let them deal with it!! If you hand lap them in, you will void all warranty!! It wouldn't be the first time that one thing is fixed and something else lets go!! It still sounds like valve timing, doesn't it?? Sounds like you guys are having fun in Oshawa!!!
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<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Gary Lloyd:
It still sounds like valve timing, doesn't it?? <hr></blockquote>
Hi gary,
Why does it still sound like valve timing?
D

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"However he poured kerosene in the ports and the valves are leaking"
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Because the compression is down in them all and even if the valves did leak a little kerosene it should still make compression!! Also if there is a bit of a large end gap and all the rings are rotated properly, it should still make compression!! What do you think it is Dave???? One more question, when it was honed, was it honed fairly well and did any spots show up that did not show any honing??????
 
Yah, but a good hand hone and new stones can be pretty good!!! I have done it more than once and never had a problem!!! I prefer to take the block in and get it power honed, but either way should work!! But you know, if he just honed it lightly and the cylinders are out of round, that could be the problem!!!
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Gary,
It isn't exactly clear to me that all cylinders are down now. He said;
"Both middle cylinders are 25-30..."

Leaking valves don't make much compression. A leakage area of an .040" diameter hole would drop compression drastically.

It could be a combination as you say. Ring end gaps, valves, gasket. Also there is a remote possibility of cracks in the head. Either the car's or mine.

I sincerely hope that the problems get resolved before we all go nuts.
D
 
'We did get about 5 pounds more but still the best is 40 lbs...Both middle cylinders are 25-30'

I personally would like to know how much the valves are leaking!! My impression was that it wasn't much, but I could be wrong!! It just seems real weird to me!!
 
Only way the head woud affect things that badly is if there's a terribly big crack right through those 2 cylinders that's allowing seepage through the seats...I'm still saying the problem is in the pistons/cylinders/rings....why don't ya'll get a manual & set it up exactly to specs...gonna bet you've done some damage to rings/cylinders!
 
and cracks tend to leak more when they are warm!! Broken rings???? I think the motor should be pulled and stripped down and find out where the problem is!!! Other than that, it is like shooting in the dark!!
 
Do this: crank engine &, while its idling, spray WD-40 directly onto the edges of the head gasket all around head...what happens....s if the WD-4o is pulled into the enginejust curiou

...other thing is squirt a little oil down each spark plug hole & recheck compression after the oil is in ("wet" compression check)...if compression doesn't go up "wet" check versus "dry" check, problem is in block.....if it does go up, problem is in head!
 
Uh, Tony, I think you've got that backwards. The oil in the cylinders will tend to temporarily seal the rings, resulting in higher numbers "wet", indicating the problem lies in the cylinders, rather than the valves.
But, I know you know that.
That's why I try to proofread my posts, as the old grey cells just ain't what they used to be!
Sounds like a song title.
Jeff
 
Took the head back to machine shop today....The valves were all leaking .......middles bad.....Anyway they have addressed that and one is still leaking ....Dad has ordered new valve springs also since they were old and to me are not providing enough tension.......He also has got 2 pistons out so far and rings are good and rotated properly.....They have too big a gap though so he,s ordered new ones again.......He's very frustrated and i must admit it has got me puzzled also.....We'll have to wait till the end of the week for the head, springs rings etc......It has to be be right this time...

And i thought i had problems being an owner of 3 different Rovers
 
One too many Corona's...was just given permission to ride one of the 25 replica's of the Peter Fonda 'Easy Rider' bike this weekend..excited....hope the weather clears up!
 
The good news is the car is up and running again......All is right without the exorcism dad thought it might need......A quick look back reveals the valves not sealing properly along with the head being warped lost us all compression.....after being machined and planed it still was leaking so it went back and was righted.....With new valve springs and a slight burr on one valve stem....it sealed perfectly.....I helped dad and after a few other misadventures it fired right up and while i only checked #1 cyl just to see what it had (110) i assume all will be in the 100,s now.......This has been quite the misadventure and was really wearing dad out but happy to report that MG now stands for Might Go......if it wants to
Thank you to all that offered advice for what turned out to be a real adventure in what could go wrong will........
Now the B is running i'll concentrate on my Rover 2000TC rebuild........Somehow i know it will go smoother

Bill Robertson
1967&1969 Rover 2000TC's
1948 Rover 75 P3
 
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