TR4/4A Okay guys-so how hard is it really to freshen up a TR4 engine?

[tdskip]

Hypothetically speaking let's say you had a 60,000 mile TR four engine that was not displaying any bad symptoms but you wanted to freshen it up. Beideman would seem to be an obvious place with bearings, but "simple" enough to do rings? If rings then pistons to? Take me to school please - I am itching to dive in as I've never done any internal engine work but as many of you know I'm basically an idiot so it would be easy for me to get in over my head.

 

[TR3driver]

Changing rings isn't hard, but is a lot more work than just doing rod bearings. I wouldn't bother unless a compression test showed some degradation in ring sealing. A problem too small to show up on a compression test isn't going to make any "seat of the pants" difference either.

And yes, usually (in my limited experience), if the rings are worn until they don't seal as well as before, then so are the cylinder walls. Which for a TR4 motor means drop in a new liner kit. Only slightly more work than just rings, since you'll already have the head & pan off, pistons out of the way and so on. And if you don't have it already, you can drop in a 87mm "big bore" kit, which will definitely provide a little extra grunt. Also a great time to clean out the water jacket, since there is usually a lot of crud built up around the back.

But before tackling any of that, I would suggest checking the valve lift. If one or more lobes are significantly worn, then I'd include a new camshaft (and lifters of course) as part of your plan.

My point is, try to measure and find the problem area, rather than just throwing parts at it.

PS, the TR3 factory flat rate manual says 5.5 hours to R&R pistons; only 2 hours to R&R rod bearings. But to change main bearings, it says to add 7 hours. Unless you're a really lightning mechanic, you'll never match those times, but IMO they do give a good guideline (with some appropriate fudge factor, like twice) to how long a job will take. Assuming of course (and we all know what that does) there aren't any problems along the way.

PPS, recite after me : If it ain't broke, don't fix it !

 

[TR3TR6]

If you know of a good and reasonable machine shop, you could probably get the cylinders rebored cheaper than buying a new liner kit to the size that you want. If you end up having to do the valves, make sure you have harden seats installed for the unleaded gas. If you have 60,000 miles on the engine, like Randall said you need to run some tests. It may be ready for a complete rebuild and then you would know what you had.

 

[tdskip]

Hi Randall, thanks for the note. While perhaps not as much fun as randomly throwing parts will follow your advice. Let sm get this thing home and run all the tests and go for there, my other one had the uprated pistons and it made a noticeable difference.

Thanks!

 

[TR3driver]

If you know of a good and reasonable machine shop, you could probably get the cylinders rebored cheaper than buying a new liner kit to the size that you want.

I'd want to make certain they have experience with wet liners, though. Very few engines have them, and boring a wet liner is different than boring the usual engine block. Without the head in place, the block doesn't hold the liners firmly enough to accurately machine them. The usual method is to make up a clamping plate that can be bolted to the block and hold the liners, while allowing the boring machine access to the bores.

 

[TR3TR6]

Randall I had mine bored 40 over. The machine shop I used is run by an old timer (he might be as old as me) that really knows engines. He does a lot of the street rodder's around here. He has a large inventory of engines and engine parts which included a couple of heads that fit my TR3A. I've had no problems with my engine since rebuilding it. Then again, maybe I was just lucky.

 

[Rut]

I'm very lucky that a friend owns a machine shop, owns an MG, and he does a lot of work on wet liner diesel engines. We are currently rebuilding an MGB engine followed by a 1275 for a Bugeye to be followed by a 1967 TR4a engine. If the TR4a internals are decent enough I will have it bored, if not I will go the liner/piston route. That said, if there is severe pitting in the liners I may have them 'lined' to bring them back to the original bore if the pistons are in great shape. I know that sounds weird, but it may be the most cost effective route. Has anyone done or heard of this before? Crazy?
Rut

Just got back from the machine shop and I mentioned my comment...he was referring to the really big diesel tugboat engines regarding sleeves in liners and said I was crazy!

 

[bobhustead]

Randall's PPS "ain't broke, don't fix", underscores the proposition that if you are going in, take it all apart and machine or replace everything that's out of spec. E.g. putting bearings in a 60k mile engine is just a poor use of time.
Bob

 

[AltaKnight]

You really need to determine ring and valve condition with a compression test at least; also take a look at the oil pressure when hot at idle and at speed to determine the condition of the bearings. When I got my TR6 at 53k miles I changed all the bearing shells after checking the journals which were in fine shape, the OP improved dramatically, also changed the rings while there and he bores were in good shape, just a bit of glaze busting needed. BTW I did all that with the motor in the car, not that difficult if you don't mind being on your back underneath it for a while. None of this is very difficult if you have a mechanical disposition, but you do need decent tools and some specialty measuring tools, micrometers, dial indicators etc oh and a fair bit of patience.

 

[TR3driver]

E.g. putting bearings in a 60k mile engine is just a poor use of time.

I'd have to say that depends on the situation. One of the TR3 manuals even suggests changing the rod bearings every 30,000 miles, as preventative maintenance. At any rate, I've done it several times and I've never been sorry I did. Invest a few hours effort to squeeze a few more years use out of the engine; while saving up nickels and dimes to "do it right". Except in my case, it keeps turning out to be 10 years and then something else happens

I haven't found time to do a proper rebuild since 1976! Hopefully that will change, now that I don't need to drive the car to work Monday, but it hasn't happened yet.

 

[TR3driver]

Randall I had mine bored 40 over. The machine shop I used is run by an old timer (he might be as old as me) that really knows engines. He does a lot of the street rodder's around here. He has a large inventory of engines and engine parts which included a couple of heads that fit my TR3A. I've had no problems with my engine since rebuilding it. Then again, maybe I was just lucky.

Just for clarity, I didn't mean to say it couldn't be done, or any disrespect for your favorite machinist. I know other people that know how to do them as well.
Just trying to point out that it might be a concern, something to ask about, since the wet liners are rather unusual.

 

[Guest]

E.g. putting bearings in a 60k mile engine is just a poor use of time.
Bob

I had one rod journal so bad it had a ledge in the middle of it so sharp it would cut your finger. It looked like the dual offset Buick V6 journals. I polished it out and put in a new set of cheapy bearnings, that was at 94K (25K ago) and it still runs great. Poor little thing knocked on start up for 10K before that. You'd be surprised how much more life you can get out of an engine if you just give it a chance.


That being said, if you don't know what you're doing, (Skip) don't mess with it and bring it to a professional. I can get away with things like this because I've been doing it all my life.

 

[TR3TR6]

I totally agree with you Randall, the wet liners are a different breed. When it comes right down to it, the old British cars in general have a lot of unusual things compared to American cars. One of the things I really like about this forum is learning all the different ways there is of doing things. There's a lot of knowledge and talent on here.

 

[tdskip]

Good discussion guys - appreciate all the considerations.

 

[MichaelG]

But before tackling any of that, I would suggest checking the valve lift. If one or more lobes are significantly worn, then I'd include a new camshaft (and lifters of course) as part of your plan.

Randal, Is there a preferred method to check the valve lift? Does it require removal of the rocker assembly?

 

[TR3driver]

You can get a pretty good idea just by sitting a dial indicator on the valve spring retainer, and noting the reading as you step through two engine revolutions. Of course you have to factor in the valve lash and rocker ratio to compare that to the cam specs, but you can compare one valve to another without doing any math. (Much like checking compression ratio, it's unlikely that all the lobes are worn evenly so most wear will show up as a variation from valve to valve.)

To get a more accurate measurement though, you need to remove the rocker shaft (which is no big deal) so you can put the indicator on top of a pushrod. Here's a photo that shows the general idea (though not of a TR motor)

Enco usually has a dial indicator and magentic base kit on sale for under $25. Looks like it's only $20 at the moment.
https://www.use-enco.com/CGI/INLMPI?PMPANO=0744455&PMKBNO=3537&PMPAGE=7&PMCTLG=01

HF has them too, but I'm a bit leery about buying precision tools from HF. At least my perception is that Enco has a little more quality control than HF, but I could be mistaken.
https://www.harborfreight.com/1-inch-travel-machinists-dial-indicator-623.html
https://www.harborfreight.com/multipositional-magnetic-base-with-fine-adjustment-5645.html

Anyway, I've been using one from Enco for a lot of years (since when they had a store within driving distance of me and HF didn't) and it still works.

 

[Geo Hahn]

I did rings and rod bearings on my TR3A in 1980 - like Randall, thought that would hold it until the dollars and time made a more extensive rebuild practical.

Last years (after 34 years on that set-up) I finally did a bit more. This time pistons & sleeves and bearings. I think the piston and sleeve set was the cheapest option (vs machining) and it certainly was a no-brainer as everything was made to go together. I got the set from Moss and with a special price it was a bargain. The whole process of pounding out the old and pushing in the new was so simple I wondered why I waited so long.

 

[TR3driver]

I can get away with things like this because I've been doing it all my life.

So, did it blow up the first time you did it?

My first time with a TR3 motor was when I was 19. No clue what I was doing, not so much as a Haynes manual to help guide me (let alone the Internet). On top of that, the motor wasn't just worn out, it was blown up. Exhaust valve head broke away from the stem and pounded it's way through the piston and liner. The rod wound up bent by about 30 degrees, a big 'C' shape. The biggest piece of liner I found wasn't much bigger than a half dollar.

No space in the garage, and no time to "do it right", so I parked the car in the side yard, put it up on jack stands, and set about making it run again with the motor still in the car. Used head & rod from another TR3A (Dad found some abandoned projects in a barn), plus gaskets, bearings, liners and pistons from Warshawski's. Fortunately it hadn't run long enough to spread swarf throughout the oil system, so the crank journals were still OK. I was convinced at the time that the blowup was from running with a 4.10 axle and no OD, so I also swapped the axle out. In retrospect, I suspect the carbs were the real problem, and for reasons I don't recall, I swapped them out too.

This was winter in Rensselaer IN, and there was snow on the ground. So I draped a tarp over the top, and stuck an electric heater underneath.

Believe it or not, I got it running and it turned out great. I went back to school and Dad went back to driving the TR to his job (150 miles each way). I don't suppose it has covered more than 50,000 miles since then, but it was still running just a few years ago when Dad lost a wheel and tore the car up even worse than I left it.

 

[bnw]

At 60K, IMO, with no obvious problems as you said originally, I wouldn't do a thing. That engine, with normal, proper maintenance, should go at least another 50K needing nothing. On the other hand, I would be looking at hot oil pressure. If that is not up to spec, ie. 70psi at cruising, 3000RPM, hot, with 20W50, rod bearings are the most likely problem. The mains are the biggest mains I've ever seen. That's why our 3 main bearing engine lasts 10 times longer than the wimpy 3 main MGA/B. Like Randall, I've done all this over the years on numerous TR3s. I did rod bearings at .001 or .002 under for oil pressure (lasted 50K miles) and on another car, Warshawski liner kit ($94.00) in my back yard for smoking and oil consumption. In all these years, I have never known or worked on a more forgiving, stout, responsive engine. I love these cars, and this is one of the many reasons why.

 

[HerronScott]

So, did it blow up the first time you did it?

My first time with a TR3 motor was when I was 19. No clue what I was doing, not so much as a Haynes manual to help guide me (let alone the Internet). On top of that, the motor wasn't just worn out, it was blown up. Exhaust valve head broke away from the stem and pounded it's way through the piston and liner. The rod wound up bent by about 30 degrees, a big 'C' shape. The biggest piece of liner I found wasn't much bigger than a half dollar.

No space in the garage, and no time to "do it right", so I parked the car in the side yard, put it up on jack stands, and set about making it run again with the motor still in the car. Used head & rod from another TR3A (Dad found some abandoned projects in a barn), plus gaskets, bearings, liners and pistons from Warshawski's. Fortunately it hadn't run long enough to spread swarf throughout the oil system, so the crank journals were still OK. I was convinced at the time that the blowup was from running with a 4.10 axle and no OD, so I also swapped the axle out. In retrospect, I suspect the carbs were the real problem, and for reasons I don't recall, I swapped them out too.

This was winter in Rensselaer IN, and there was snow on the ground. So I draped a tarp over the top, and stuck an electric heater underneath.

Believe it or not, I got it running and it turned out great. I went back to school and Dad went back to driving the TR to his job (150 miles each way). I don't suppose it has covered more than 50,000 miles since then, but it was still running just a few years ago when Dad lost a wheel and tore the car up even worse than I left it.

I was going to reply with my story that's similar to yours Randall. I rebuilt my TR4A motor when I was 24 and restoring my first car. No prior experience with rebuilding engines and as you commented certainly no Internet but I did have the Bentley manual (and Haynes). Oh and I was doing this in an old drafty ex-barn with gravel floor and no electricity beyond my parents generator that I borrowed. It was the original engine that was at least running OK with over 100,000 miles on it (unlike yours). The factory manual is great and it's such a simple engine that it's not that difficult to rebuild and mine was still going strong 75,000 miles. I only made one mistake which I had to fix shortly after getting the car back on the road. I used a timing chain with a removable link and I believe I installed the clip "backwards". When it came loose, it took out the tensioner stud and put a small whole in the timing chain cover which was relatively easy to repair. I would say anyone with basic mechanical skills should be able to rebuild a TR3/TR4 engine.

Scott