TR2/3/3A TR3A Engine Cubic Capacity?

[hit_n_miss]

On the General Specification page in the "Practical Hints" manual it lists two different values.

Cubic Capacity: 2138 cc
Brake H.P.: 105 hp

Special Order: 1991 cc
Special Order: 100 hp

Is there any way to tell which displacement a given engine has short of pulling the head and measuring the bore?
My engine number is: TS/30597-E

Thanks!

 

[titanic]

Arnie-I think you have the sizes reversed. The stock size for the TR3A would have been 83mm pistons and 1991cc. Special order would have 86mm pistons and 2138cc. This is the same size used on the TR3B and TR4. But by now, most cars are probably using 87mm pistons (and liners) which give 2187cc. I don't think it is possible to tell what is fitted without removing the head. Increasing the bore size will also increase the CR.
Berry

 

[Geo Hahn]

I suppose a crafty (and determined) fellow could also measure the bore from below.

 

[hit_n_miss]

Thanks Barry. At least they were consistent in that table. They listed 86mm pistons as stock and 83mm pistons as optional. When I first read that it struck me as odd that one would "special order" a lower HP engine, but as a TR3 newbie I just went with it.

 

[titanic]

Arnie-I think the 83mm pistons&liners were an option for TR3Bs&Tr4s to allow the cars to compete in the under 2 liter class.
Geo-I thought about that approach, but thought the rod would be in the way.
Berry

 

[TR3driver]

We've debated that entry in PH 6th ed several times, with no clear consensus. My personal opinion is that there was a plan to make the 86mm standard for the TR3A, but it didn't actually happen until the TR3B. However, the 86mm liners were clearly available much earlier, as they are listed in the SPC.

But by now, there is a large chance that the engine doesn't still have the factory liners anyway. For a long time, you couldn't even buy 83mm liners; and 87mm were cheaper than 86!

Looking up from below would work I think, if you know what the liners look like or can measure the thickness of the liner edge. 83mm liners have a much thicker bottom edge than the larger ones do (89s are really thin). But that is still an awful lot of work. Might make more sense to try to measure the displacement through a spark plug hole if you really have to know. Speaking of which, why do you have to know? I forgot to check while I had the head off, so I still don't know what's in my current TR3 and I've been driving it for 6 years now.

 

[titanic]

I can remember a J.C. Whitney catalog from the early 70s that had a "Big bore kit" (87mm piston&liners) for about $49.95-even included the head and fig.8 gaskets.
Berry

 

[TR3driver]

I can remember a J.C. Whitney catalog from the early 70s that had a "Big bore kit" (87mm piston&liners) for about $49.95-even included the head and fig.8 gaskets.

Yup. They used to have a storefront in Chicago, called Warshawski's, that would honor the catalog prices if you brought the catalog in with you. Must've been around 1975 when I went in to buy one of those big bore kits. They said they were out of stock; but had one that had been returned which I could have for cheap because the gaskets were ruined. It had been returned because two of the pistons were marked .0004" smaller ('F' instead of 'G' or something like that), but I didn't think that would make any difference. It didn't either, the engine I built with it ran like a scalded rabbit. I would love to build another one like it someday, but I foolishly forgot to record the specs on the "3/4 race" cam that I used. And no one makes that cheap JCW header any more either.

 

[hit_n_miss]

Randall, it's not a "need to know" question, but rather curiosity. Years ago I drove MGBs and a Fiat 124 Spyder. This is my first TR3. I received the Triumph Factory Records Certificate that I had ordered and observed some differences. My white TR3A with the red interior left the factory as British racing green with a black interior. OTOH, I did suspect that as when I removed the fiberboard boot liner to get at the hinge bolts I could see that the petrol tank was BRG not white. Some of the wear on the interior really suggests that it's been in the car for quite a while. I wonder if the body was from a "donor"?

At some point in its life the engine has been replaced. It left the factory with engine number TS/30597-E. It currently has engine number CT/13353-E. Does either engine number say anything about the vintage or characteristics of the engine? Does anyone know where the body number might be stamped?

It's beginning to remind me of my grandfather's hammer that I still have. I've replaced the handle three times and the head twice.

 

[TR3driver]

The CT prefix means it was a TR4 engine, so almost certainly 86mm originally. Again, that's no guarantee now.

There is (or was anyway) a plate with the body number, screwed to the firewall above the battery. But the body numbers bore no relation to anything, except it might be on your certificate. None of the numbers are duplicated anywhere, AFAIK.

I once went with a friend to look at a TR3A for sale. After I got suspicious and started asking questions, the seller admitted that it was two different cars, cut in half and spliced together to make one car. We left pretty quickly after that. The chrome dashboard and fluorescent green brake lines were hideous anyway.

PS, even the dealers sometimes re-sprayed the cars, in order to make a sale. I doubt that would have been necessary with a nice BRG, but it is possible.

 

[Geo Hahn]

...I wonder if the body was from a "donor"?...

If a body from one car is mated to the frame of the another - which one is the 'donor'?

Since the commission number plate was riveted to the body, I would arbitrarily say the frame was a donor.

The original commission plates had fairly distinctive rivets that are not readily duplicated with your garden variety pop-rivets - in particular the center is solid:

 

[hit_n_miss]

Curiouser and curiouser! Randall, any feel for how similar or dissimilar a TR3A engine and a TR4 engine might be? I'm thinking about those occasions when one needs to order parts from Moss or others.

 

[TR3driver]

Curiouser and curiouser! Randall, any feel for how similar or dissimilar a TR3A engine and a TR4 engine might be? I'm thinking about those occasions when one needs to order parts from Moss or others.

The cylinder block itself is identical, so no worries there. The differences would be in other items, like carbs, starter, flywheel and so on. For example, your TR3A would have originally had the banjo fuel fittings to the carbs; but the TR4 would have had push-on fittings. Pretty obvious, though, so not likely to be a problem. Your pre-50K TR3A would have had the early flywheel with the bolt-on ring gear, which mates to the early, enclosed drive starter. The TR4 would have had the later flywheel with the pressed-on ring gear, which mates to the open drive starter. Hard to say which was installed, probably depends on which gearbox they used. (The gearbox bell housing was modified to clear the open drive starter.)

But all those things might have gotten mixed up anyway over the years; so I wouldn't say the mis-matched engine number really means you have to be more careful. "They're all the same" was a common mantra at the parts store back then, but they weren't all the same and a lot of "wrong" parts got installed because that was what was available. For example, the generator changed in late 59, but the later generator was commonly sold to fit the early cars (probably still is).

All of the common tune-up stuff is interchangeable, so no worries there. (Plugs, points, condenser, cap, wires, and so on.)

 

[hit_n_miss]

That's encouraging. The car was sold as having a "rebuilt engine". I think it has the banjo fittings at the carbs. I'm wondering if they might have bolted on a number of pieces from the TR3A engine during the rebuild using a new or redone TR4 block. I also took a look at the commission plate. It does not have the solid center rivets; rather they look like ordinary pop rivets.

 

[Geo Hahn]

One difference you might look at is the distributor. There will be a number on it, most likely 40480, 40698, 40735 or 40795. The difference is in the advance specifications. Here too, it makes no difference when getting parts (same points, etc) but might be worth noting whether the one you have goes with the original engine or the TR4 engine.

After all these years one has to look at what is on the engine if you're ordering and presented with a choice (e.g. valves & valve guides) to determine what is correct for the engine in question.

...The car was sold as having a "rebuilt engine"...

Of course without specific receipts for parts it is impossible to know what that might mean.

 

[TR3driver]

Of course without specific receipts for parts it is impossible to know what that might mean.

Lotta years ago, I bought a TR3 with a "recently rebuilt engine". Wound up not driving it much, bought it mostly for the OD transmission. But I did eventually move the engine along with the transmission into the 3A I had then, since it seemed to run better than my old one. Several years later I happened to take the engine apart and discovered the "rebuild" - 3 of 4 pistons looked to be original while the 4th one was a different brand!

No big deal, just amusing. I got the car cheap through a third party (a friend of mine that had spotted it sitting in a corn field) and it paid back the purchase price many times over just in fun. We had a blast driving it from TX to LA, plus I got to hang out with an old friend for several weeks. Plus I eventually sold it without the OD (and the clapped-out motor from my 3A), for several times what I paid for it.