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Finally pulled the head...

wkilleffer

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Hey everyone,

I finally got a chance to pull the head on my 1974 MGB. Some of you may remember my earlier post about having odd compression test results on the #3 cylinder. It's been awhile since that first post.

Well, I pulled the head, but don't really know enough to know if there's anything visibly wrong. I didn't *see* what looked like a burnt valve, but they don't always look like anything's wrong. It would be too much to ask for a crack in the head to be visible.

But I took some pictures of what things looked like, and I can take more. It could just need a new head gasket, but who really knows.

I posted the pics here:
https://www.flickr.com/gp/51995051@N00/95Ciim

Please check them out and tell me what you think. Am I correct in thinking that once the engine is ready for reassembly that I'm going to need to clean off all the carbon?

Thank you,
-Bill
 

DrEntropy

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On the mating surfaces. Have you any photos of the head gasket?

Best guess is you will need to haul the head to a machine shop for disassembly, inspection and pressure testing. It ~appears~ that there was oil being introduced in what I guess as #2, the others don't appear to be horrible. Likely valve seating issues from "crud" in the chambers, affecting the valve seating. Just a tired engine, nothing catastrophic.
 

tony barnhill

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<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Just a tired engine[/QUOTE]
From the photos I thought the same thing, Doc....then I remembered he said the engine only had 5,000 miles since rebuild - the photos don't seem to support such low mileage...& there are a couple that look oil contaminated.
 
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wkilleffer

wkilleffer

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I can't remember the exact mileage figure on the rebuilt, but I'm quite sure it's less than 15k and probably less than 12k. I'll try to dig it up tomorrow.
 
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wkilleffer

wkilleffer

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I can get a pic of the gasket tomorrow. Think it's composite, but not sure.
 

DrEntropy

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P'raps valve guides not replaced? It exhibits something more like 50K. That #2 is definitely eating oil. Whether rings or valves would have been a leak-down test determined cause.
 
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wkilleffer

wkilleffer

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It took me a bit to learn how to tune it right, and I may still be learning. Can't help but wonder if my learning curve caused some of this.
 
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wkilleffer

wkilleffer

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Ok, here are pictures of the head gasket:
https://www.flickr.com/gp/51995051@N00/38t659

I'm still looking for a receipt from the engine rebuild. It was done at least six years ago, but no more than seven. Judging from the other maintenance information I have, this was done about 11k miles ago. Something that makes it difficult is that the odo has not always worked properly. But I still doubt that the engine has gone too many more than 11k miles.

Funny that #2 cylinder looks like it's shipping oil. It checked out perfect on the compression test. But its valves on the head are the dark ones. #3 was the one that was so much lower than the rest, and #4 was a little low but not unacceptably.

Thank you,
-Bill
 

jlaird

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If it was mine, which it is not of course. I would rebuild it. Rings, bearings, and have the head and valves worked.

You are going to spend about 150 for parts and the same for machine shop work. Good investment.

Machine shop, clean head and leavel same or check and seat valves with new what ever is needed.

Check crank for size and grind or polish as needed. Check cylinders for size and hone as needed.

New oil pump would be nice.

Enjoy.
 
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wkilleffer

wkilleffer

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So, a rebuild is something I can do myself, at least in theory? What's it really like to do one? I'm not a pro by any means. Not uncomfortable with tools, but not equipped with everything either. Only have so much room in the one-car garage.

But doing it myself won't break the bank with labor charges. Think I could get it done for $400 or less including machine shop if I do it myself?

One thing's for certain: I can't lay out the cash to have it done again. At least not now due to being in grad school. But I don't want it to sit. Seems more cars die awaiting surgery than do actually undergoing procedures.

This hasn't made me overconfident in my mechanical abilities, but on the same note, I'm no less confident in professional services either.

Thank you,
-Bill
 

jlaird

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Of course you can do it. You have us to answer questions and no telling how many have been done by the folks here.

We all started with the first one. It is in fact easy, think clean and go a step at a time.

Parts you will need:

Upper and lower gasket sets

Cam bearings

Main bearings

Rod bearings

Rings

Oil pump

Check the priceing in the Moss catalog and save some through Tony for example

Check with your favorate shop for priceing of:

Rebuild head check level and do so if needed maybe guides.

Tank block and replace freeze plugs

Measure and hone cylinders to make sure all is good for pistons and rings.

Measure and polish mains and rod bearings to make sure you get the right bearings. Hopefuly the crank will not need ground.

Install cam bearings.

Any good shop will have the specs and can help with advise on sizeing rings and bearings.

With a bit of luck and some sweat you should be under $400 for a fresh over.

Specific questions, this is the place to ask.
 

mikespain

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Hi,from the fotos you've posted- the block,the bores and pistons look in quite good condition,(overbored to +0.020),the deposit(although a bit oily) on the pistons seems quite uniform for all 4 so I would not suspect ring failure(very very rare that all 4 pistons have ring problems).The head shows definite signs of seapage outwards around cylinders 2&3.Seems that it is running slightly rich on 3&4 and too rich on 1&2.From the fotos of the head gasket there is a blow between cylinders 3&4 and outwards from cylinder 3 and possibily a slight blow between 2&3.This would explain the figures obtained in the compression test from your previous post.So if it was mine,I would get the head completely checked ,trueness/flatness of head face and resurface it if needed,valve guides and valve stems for excess wear,-valve seats and valves for pitting and correct seating,and replace the head studs which could have stretched causing the failure of the head gasket.then bung it all back together tune it properly (valve clearances,ignition and mixture)and enjoy it! Mike
 

DrEntropy

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Arm yourself with information. Bentley workshop manual, check out this page for some good info:

https://www.1978mgmidget.com/manuals_and_booklets.html

Biased toward Spridgets but good basic data for much of what you're doing.

I can't see the head gasket well enough to really have an: "Ah-HAH!" moment but the "coke" build-up seems a bit excessive for 11K miles.

The bores appear to have a nice cross-hatch still in evidence, the 0.020" oversize shows so I can't doubt the rebuild. I go back to the possibility you have valves not seating properly with guides/stems not right (out of tolerance). I'd be for doing the head first, check guide-to-stem clearances and valve seats. I wouldn't be ripping into the bottom end so quickly. Head disassembly/reassembly requires some special tools but is do-able "on the floor" so-to-speak. Measauring the bits and reaming guides, cutting seats is better done by a competent shop. They can properly pressure test it as well.
 

Mickey Richaud

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wkilleffer said:
So, a rebuild is something I can do myself, at least in theory? What's it really like to do one? I'm not a pro by any means. Not uncomfortable with tools, but not equipped with everything either. Only have so much room in the one-car garage.

But doing it myself won't break the bank with labor charges. Think I could get it done for $400 or less including machine shop if I do it myself?

One thing's for certain: I can't lay out the cash to have it done again. At least not now due to being in grad school. But I don't want it to sit. Seems more cars die awaiting surgery than do actually undergoing procedures.

This hasn't made me overconfident in my mechanical abilities, but on the same note, I'm no less confident in professional services either.

Thank you,
-Bill

Hey, Bill -

I did it - built the B engine and the TR8 - and if I can...

Find a good machine shop and have 'em check everything out. I've used Revolutionary Performance in Mt. Juliet, just east of Nashville. https://www.revolutionaryperformance.com/ Good guys. I know they're a "fur piece" from you, but they may know of someone in your area. Drop my name, if you like.

Mickey
 

vping

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I've set up shop in the back room of the garage and a Friend will be showing me all the in's & outs. If I can I will try and do a Photo shoot & write up on it.
 

tony barnhill

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Yep, you can do it, tain't hard

...now, I'm gonna take a different position than most folks (& its just my personal position)....you're in college, you probably don't have alot of extra cash (if you're like me when I was in college), you know your engine was rebuiilt recently....here's what I'd do (& saying this might loose me some sales if you decided to go with me but its another plan):

Disassemble & clean everything
Mic the cylinders/pistons & check ring gaps
Survey the bearings/bearing surfaces & torque-check them with plasti-guage
Look closely at cam bearing surfaces & cam lobs for damage/wear
Guage the oil pump for tolerances

Then, when everything checks out (which I'm gonna bet it will!):
Have a machine shop check the head & do a 3-valve grind
Hone the cylinders & reinstall the original pistons/rings/bearings
Reassemble everything

USE FELPRO HEAD GASKET

Enjoy!!

That's called an "engine refresh" - you only replace those items that are damaged or broken during disassembly....if you do it correctly & everything's within tolerance, you'll get enough driving time to get through graduate school & get settled in your new career.

There might be some wear on the bearings (I doubt it) - if so, replace them; you might break a ring removing them - if so, replace it.

Be careful to install the pistons/rings in the proper direction; keep the push rods in their original places.....it ain't rocket science.....just follow the directions in the Bentley manual & what advice guys offer here once you determine the direction you want to go.

Were it mine, that's what I'd do were I in your position (oh, wait, that's exactly what I did while I was in college - got 5 more years out of that engine!)

Now, let the chastisement begin..........
 

Bugeye58

Yoda
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Been there, done that as well, Tony. I see nothing wrong with the scenario at all. That's pretty much a mid season refresh on a race engine.
One small item I'll add: Make sure the lifters go back in their original positions. They mate themselves to the cam lobes, and should always go back in the same hole.
Jeff
 

davester

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I have a different opinion from the rest. Since you have the head off, have a machine shop go through it...evaluate/lap the valves, evaluate/replace or knurl the guides as needed, level the head. I would then just bolt it back on and see how things go. If the compression is good you are good to go, and won't have expended much time or money.

If the compression is still bad, you could go ahead with a complete overhaul (doesn't seem necessary in light of your recent rebuild info though, and I would still recommend a leak-down test before tearing into things). If that is the case, it won't take much time to tear the head off again to get to where you're currently at. Bear in mind that doing a complete engine teardown and reassembly is a heck of a lot of work, and you will have many questions at every step. It will take you a heck of a lot longer than simply R&R of the head. I don't understand why you'd do such a thing if it was not needed. If you love to spend your time bashing your knuckles and ripping engines apart in a cold garage, then go right ahead. Personally I'd rather spend that time tinkering or driving.
 

jlaird

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I think I would have the head and valves done and try it. Cheep enough. In any case you will only be out a head gasket as no matter what the head will need redone.
 
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wkilleffer

wkilleffer

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Alot of this seems to involve dropping the pan and taking the pistons out. A scary scenario if ever there was one for me. Have to get myself under there somehow. That also involves having to time the engine from scratch, which is daunting to say the least...

A great deal of what Tony said is borderline Greek to me, but I'll maybe figure it out...

I did label all the pushrods, so they'll go back in the right holes...

Now, Mikespain mentioned being able to tell where the blown places were on the gasket. Now, the dark place on the head between cyls 2 and 3 is pretty plain, as is the oily buildup. How do I spot the other?

Thank you,
-Bill
 
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