1949 MG TC Engine Rebuild and other stuff

[Steve Simmons]

My latest project, like I need another one right now!

tc.jpg (52.45 KiB) Viewed 43687 times

Lets see...
MGB GT = hit by suburban
MGC GTS = Two 3/8" holes in tire
'39 Ford = Under restoration
MGB = engine on floor
I'm running out of cars!

[Stewart]

What happend?


That was the 3rd thing so you should be safe for a little bit.

[Steve Simmons]

Oh, this one was planned. I gave myself a deadline of February 11th to get the V8 back in the truck so that I could start on the TC. It needs a bunch of work - head job, new clutch, rebuild gearbox, rebuild shocks, rebuild water pump, new u-joints and some other stuff.

[gorms68]

You holding the MGA in reserve? Oh yeah you still have the oldest truck. Just plan your trips well in advance so you arrive on time

[Steve Simmons]

I guess some updates are due. I haven't been taking many pictures but here are a few y'all may find interesting.

After taking the head off, I found lots of "yuck" in there, especially a large amount of carbon build-up in the intake area. I had some peculiar symptoms with this engine and finally found out why. Whoever rebuilt the engine last time left all the valve stem seals out, and then assembled the spring assemblies incorrectly so rather than deflecting oil, they were literally scooping it into the valve guides. I lapped a few valves myself and then decided there was more damage than I was comfortable lapping out, so I tore the head down and delivered it to a machine shop to be cleaned and ground.

XPAG Cylinder Head

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Next I rigged up a hoist to pull the rest of the lump out of the car. Worked pretty well, but I have some ideas to improve it for next time. I think it will be better than a "real" engine hoist when I'm done.

Pulling MG TC Engine

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The top end also showed a bit of yuck so I set about cleaning that up. There is some scoring in one of the cylinders but I've decided that I would rather not do a complete rebuild, and compression was good in that cylinder anyway, so I'm going to ignore it.

XPAG Engine

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Here's something you may not have seen before. Pistons with positive deck clearance, PLUS a raised center section of probably 3/16". This gives a rather large compression boost but watch those valve clearances!

XPAG High Compression Piston

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Moving down to the bottom end, the first scary thing I found was more than half of the cotter pins missing from the rod and cap nuts. Thank goodness they all stayed tight! Most of the bearings looked fine, but one showed corrosion and light scoring on the crank shaft. At this point the damage has been done and will not continue to get worse, so I will most likely leave everything as-is. Maybe I'll replace the rod bearings, but that would be as far as I'd go. Again, I don't want to so a full rebuild unless there's a strong reason to do so!

XPAG Engine

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The camshaft looks ok but I will measure that when I pull it out, and since I got a great deal on some timing gears I'll replace those at the same time along with a new chain. It won't be long before I'm on the reassembly stage, but I still have to replace the gearbox and rebuild the drive shaft before I can drop the lump back in. I'm trying to get this all done in the next two weeks, work permitting.

[Larry Kluss]

Nice progress, Steve. Love the hoist!

[Steve Simmons]

This weekend's progress isn't huge but I've moved forward. The first order of business was to finish disassembling the lower end enough that I could get the new bearings in and install a new rear main seal conversion. I also wanted to make sure there weren't any broken rings, and pistons are easier to clean when they're out of the engine anyway.

XPAG parts

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There was a lot of carbon on #3, which had the worst sealing valves of the bunch. But the big surprise was two stiff wrist pins, and on those two pistons there was a lot of scuffing. Number four was the stiffest of the two by far, and that's the cylinder with the most scoring on the walls. I plan to test the pins while hot to see if they loosen up, and if so I'll have to decide if I want to leave things be or dig deeper.

EDIT: Bad news, pistons are pretty bad, looks like I'll have to bore it out and buy new, larger ones.

Scored pistons

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The most time consuming project was cleaning up that ugly black engine block, getting it masked off and then painted. It was a nasty job that spanned many hours but it was really worth it in the end. I ended up using two coats of primer, three coats of paint and three coats of clear coat. The color isn't perfect and it isn't original, but it's a fairly decent period-correct shade.

Note the brass engine tag that my lovely wife helped me polish, using her own special cleaner. I was skeptical but I have to admit that stuff is great!

Block stripped and cleaned, and masked for paint

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Block primed and ready for paint

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Block painted and clear coated

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[gorms68]

That looks great Steve. You may want to start driving with the side panels removed from the bonnet!

[Larry Kluss]

Making progress, Steve. I love a clean engine. Too bad they never stay that way.

[tannyo]

You might as well dig deeper. Then you'll know it's all good and you can trust the engine. If you leave it, you'll always wonder if it's going to go bad. Nice job on the paint and engine plate, BTW.

[Steve Simmons]

Oh, I've dug more than deep enough at this point. I've overlooked some things and I may have to bore the block, which could means boiling it out, which means boiling all that nice paint off.

EDIT: Disaster! A whole day scrubbing, masking and painting wasted! Why? Well... my refresh has turned into a full-blown rebuild. I really, really tried to not let it get here to this point, but here we are. The current status of the build is...

New pistons / rings / pins
New rod and main bearings
Crank being ground
Camshaft being re-ground
Lifters being re-surfaced
Head boiled out and surfaced
Valves and seats re-ground, new valve seals
Rebuild water pump
Rebuild oil pump
And last but not least, my beautifully painted block is being boiled.

The block has been sleeved but there's room to take another 10 thou out of it, so that will be done IF new pistons can be found in that size. If not then I may be able to hone and stay +10 and live with some light scoring.

I also found that at some point, someone machined the radius off my crank journals. That means I will never trust it to survive more than one more grind. Thanks a lot, mystery mechanic!

[Steve Simmons]

Current status: No more shiny paint.

On the bright side, the machinist mentioned that this is the toughest paint he's ever seen. It spent TWO DAYS in the tank and the paint still wouldn't come off. Guess all that careful work paid off... or rather it will again.

[Larry Kluss]

Consider the first paint job a dress rehearsal.

[max71]

Might as well put a blower on it to make the whole thing worthwhile.

[VWNate1]

You didn't detail why the block needed boring nor why the crank needed turning.....

As a Mechanic , I live to read how other approach this kind of meat & potatoes work....

Too bad about the DPM ~ it seems 60 % of most repairs , is un doing the DPM damages .

[Steve Simmons]

The bores had a slight taper to them, and light scoring in two. It wasn't TOO bad, but two of the pistons were shot so rather than buy the same size and risk having to replace them again on the next rebuild when it would surely need to be bored, I just went ahead and did it now. It only costs $35 or so to bore the thing.

I was at +10 before but I could only find high compression pistons in +30 so I went ahead and bumped it up a bit since the block had been sleeved already anyway.

The crank had scoring on two of the rod journals so those were taken down from 20 to 30 thou under. The mains were fine at 20 thou already so we didn't touch those. I also had the rear flange micro-polished in preparation for a modern lip seal conversion to replace the old flaky rope seal. I don't expect a 100% leak-free engine, but combined with the lip seal at the front as well, it should be much tighter than it was.

Today I finally had time to paint the block (again) and also the head. I ran out of clear coat and had to drive as quickly as a Model T could, to get more. I waited too long and shot it in the dark so the last coat of clear ended up hazy. I'll look into polishing it up this weekend in hopes of saving it so I don't' have to sand and re-clear.

Prepped...

XPAG Engine

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Primed...

XPAG Engine

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Painted...

XPAG Engine

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This isn't my piston, but it's just like the ones I pulled out. I found a set of NOS AE / Covmo locally so those will be going in soon.

High Compression Piston

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[VWNate1]

Thanx ! .

How much taper ? .

Also , what will the CR be now ? .

Last time I remember , a 'T' Model went about 45 MPH wide open and with the mixture rod screwed in home after reaching full velocity....

I assume (hope !) you're added drum brakes to it ? .

[Steve Simmons]

This is an MG TC, not a Model T! I know, I have too many T's around here. True, the Model T will go about 45 wide open, downhill with a tailwind. The TC however will reach about 80 MPH before running out of gear. And yes, the Model T does have rear wheel drum brakes, as well as the original transmission brake connected as a backup.

The bores had about 1 thou taper if I recall correctly, maybe slightly more on one or two. That combined with wear and scoring put me over the edge about it.

[VWNate1]

YOU'D said you drove the 'T' Model to get more paint......

You're really picky ! I once overhauled a '57 235 that was in my old '46 Chevy shop truck , it had .014" taper and three cracked pistons , my buddy who was a lifetime Chevy Master Mechanic told me to just replace the pistons and stuff , not to worry about the taper ~ it turns out he was right ! I drove that truck all over the Western United States hauling parts & flat towing cars , it ran like a champ and didn't smoke nor burn oil , it didn't even have any piston slap , much to my amazement .

I finally (& stupidly) got bored with it after 15 years of hard , daily Commercial Service and sold it , still running perfectly .

Your TC is going to run like new again !

.

[Steve Simmons]

Oh, duh, I get it now! The Model T never had a chance to get to 45 MPH. Wasn't enough runway between me and the auto parts store. I did have it "floored" though!

The TC takes the wife and I on multi-thousand mile road trips along lonely back roads. The last thing I want to do is skimp out on a few hundred dollars and end up broken down. Not a lot of room in the car for spare parts unless I leave the wife home!

[VWNate1]

Right ;

I too Tour a lot in those old beaters you see me rattling along in.....

[Steve Simmons]

Today's project: Rear oil seal

In an effort to contain the engine oil within the engine, I'm converting the front and rear rope seal setups to modern lip-type seals. The rear involves replacing the original seal retainer with a custom aluminum piece that will house the one-piece modern seal. I've run into an interference issue with the rear main bearing cap, so I'll have to set up the mill to run the flange on the cap down a bit.

In order to check alignment with the rear flange of the crankshaft where the bearing will run, I had to first fit the crank to the block, but the supplied center bearings had to first be fit for end float. I did this the old-school way, using sand paper and a surface plate. The crankshaft flange was micro-polished while at the machinist to make sure it is nice and smooth for the seal to ride on. There are still a few imperfections but I don't think they will pose a problem.

[gorms68]

Very nice Steve. When you are done this can be your new daily driver. Should purrr.

[VWNate1]

# 1 : please explain to me why you're a Camera Operator instead of a Journeyman Mechanic ? .

I have a buddy who works like you , he builds engines for Honda N.A.'s racing and makes *very* good $ plus enjoys the work a lot .

# 2 : what will the CR on this engine be ? .

I'm sad to hear a lazy Machinist screwed up the previous crank grind , I've seen that happen on Porsche 356 cranks and they'll crack where the radius wasn't done properly .

This is a Terrific thread ! (note clever use of BRG there) .

Keep up both the excellent work and the posts with pix .

[Steve Simmons]

Well, because I don't know what I'm doing! Thanks for the words of encouragement though. If Honda needs more guys to pay a fortune to, let me know. I don't HAVE to be a cameraman.

Best I've been able to figure, compression will be approximately 9.1:1.

Chris, the TC has acted as daily driver once before, for a short time. It makes a fine daily driver really, except that it isn't the best for long distance freeway commuting. When you're in a hurry to get to work and you're driving 60-65 in the slow lane, it can be a drag!