TR4/4A Engine rebuilding

Some questions: what size pistons and what kit would you recommend if I oversize? I really liked the County set I got from Moss. I think mine was the 87mm set. Can't recall.

Can I really determine cam bearing condition by eye or should I just replace?

I'm leery about the so-called improved lightened lifters. Any thought?

Do I rebuild on the stand? Is that possible?

Brand recommendation for bearings?

Must I really buy all new connecting rod and bearing bolts? Costly.

Just put a new clutch on and don't take chances?

Any other tips?

Re the cam bearings.
Have your old ones remetalled, then fitted, and then line bored to suit your reground camshaft.
Have your old lifters resurfaced.
New clutch and pressure plate for sure.

IMO 89mm is pushing the envelope. If you just want reliable, stick with 87 or smaller. That said, I plan to use 89 next time for that little extra 'grunt', along with a hot cam, 4-2-1 exhaust and so on.

According to the book, the difference between new and "wear limit" on the cam bearings is only .002" or so. You can't see that by eye. So either measure, just replace, or assume they are OK.

Lightening the lifters isn't going to help anything if you stick with the stock redline, and may weaken them. IMO you should stick with stock pattern lifters, but make sure they are hard enough. I'm not sure if it is still a problem today, but a few years back almost all of the lifters on the market were inconsistently hard. The smart setup was to 100% test new ones for hardness.

Should be no problem on the stand.

I've always reused rod & main bolts (after inspecting them for damage and distortion of course), never had a problem. But again, it depends on what you are going to do with the motor afterwards. If you're planning on turning 7000 rpm on the track, then ARP bolts are cheap insurance.

Likewise, I reuse the clutch if it looks good. The friction plate can be relined at significantly lower cost (and better reliability IMO) than new if necessary. I've never had a pressure plate that failed, even after almost 300,000 miles. (However, I did switch when I installed the alloy flywheel, because it wasn't drilled for the TR3 pressure plate.)

Obviously, my approach is a little different than most people on this forum. Far too often, brand new parts are defective (too weak, wrong materials, wrong size, etc.), while usually I know the old parts have served well for many years. If they are not worn close to the limits or otherwise damaged, I tend to reuse them. We've had long discussions (mostly on the Team.Net list) about defective parts, and IMO it would really suck to have a motor trashed because some stupid new part was wrong.

This photo is of a buddy's Stag motor, with only some 7000 miles on the rebuild. He was not a happy camper!


What I don't have are photos of the new clutches that have broken, fuel pumps that came apart and took out the camshaft, oil pumps where the rotor slipped on the shaft (starving the bearings), etc. But I have heard the stories!

TR3driver said:

Obviously, my approach is a little different than most people on this forum. Far too often, brand new parts are defective (too weak, wrong materials, wrong size, etc.), while usually I know the old parts have served well for many years. If they are not worn close to the limits or otherwise damaged, I tend to reuse them. We've had long discussions (mostly on the Team.Net list) about defective parts, and IMO it would really suck to have a motor trashed because some stupid new part was wrong.

Click to expand...

The better informed I become, I the more I tend to agree with Randall on this. Tom

TR3driver said:

my approach is a little different than most people on this forum. Far too often, brand new parts are defective (too weak, wrong materials, wrong size, etc.), while usually I know the old parts have served well for many years. If they are not worn close to the limits or otherwise damaged, I tend to reuse them. We've had long discussions (mostly on the Team.Net list) about defective parts, and IMO it would really suck to have a motor trashed because some stupid new part was wrong.

Click to expand...

I have learned this from Randall - quality of older parts is often superior and if they can be re-used it is a plus.

That said, I had 89's put in my last rebuild and it make a nice difference.

I use the old stuff if possible

Oh, well, some more questions (one of which might sound familiar):

a) When I pull the flywheel will it become immediately apparent whether my rear main seal was leaking;

b) In rebuilding the engine, is it necessary to remove the front engine plate;

c) I pulled my transmission. It's on my bench in neutral. It has an overdrive. When I rebuilt it last year I was meticulous, I think. It's run great ever since. But when I spin the rear flange by hand, just testing for feel, it seems a bit tight. Granted there are parts to move, and a rubber rear seal involved. But if I twirl that rear flange with my fingers, should it keep spinning for at least half a turn? Mine stops immediately;

d) I assume both the block and the head should go to a good cylinder shop for examination and new valves?

e) Is it wrong to use a head gasket other than Payen? Moss seems to be recommending a new one, and it's not a copper sandwich.

a) Usually

b) The gasket will tear when you remove the front main cap. So it's not totally 100% necessary, but probably a good idea.

c) Doesn't sound like anything to worry about.

d) Are we talking full Monty here, or just freshening? I've never bothered sending the block out, and the head only if it needs work or I want it magnafluxed.

e) AFAIK Payen doesn't make them any more (unless they started again?), so unless you want to search out NORS, you'll have to go with someone else. If you're building a street engine, I'd stick with the copper-clad composite. The solid gaskets (copper or steel) do have some advantages (mostly that they are easy to modify yourself), but they also have problems. If you do go with solid copper, get ahold of Mordy Dunst and get a can of his special magic sealant (he'll also sell you the gaskets to seal with it).

KVH said:

c)...if I twirl that rear flange with my fingers, should it keep spinning for at least half a turn? Mine stops immediately...

Click to expand...

I just twiddled my spare gearbox with a similar result.

OK thx! I'll continue on my roll.

I agree with the others for b-e. For "a", the rear crank seal leaking should be obvious even before you pull the flywheel!

I see very little evidence of oil under the rear main seal.

Very disturbing since I'm about to rebuild my engine.

For years I've tried to hunt down this leak. Thickest oil has always been on the the rear lip of the front transmission plate/cover, so I'm puzzled. The bell housing is nearly dry.

I can't imagine the kind of leaking I had was from the pan. I'm on my third pan gasket and even had the pan at the shop.

Having said all that I'll mention two other puzzling things I noticed:

There were about two tablespoons of oil under my battery in the battery box.

What on earth? I can't figure that out at all.

More odd, when I disconnected my speedo cable from the transmission another tablespoon of oil came running out if the cable housing.

I'm lost here.

Does the oil at the trans/engine smell like 90wt or motor oil? Probably a clogged crankcase vent is forcing vaporized oil out of the valve cover/pcv and it blows back to the batt and collects in the box. Dunno on the speedo cable.
Bob

There is an seal in the tranny speedo drive gear block. The threaded portion that the cable screws onto has to come out to replace it...and that is staked and must be drilled to remove. There is also a vent hole on the top of the tail housing that may be blocked, forcing oil out the speedo drive gear.

Oil from the rear main will usually come out the bell housing hole. If you replaced the pan gasket several times, then the crank scroll seal is likely the source.

I don't know about the battery box. Is there sign of a lot of blowby coming out the valve cover vent? It may just be very worn rings...or the draft tube being plugged, forcing oil out the rear scroll seal and the valve cover vent...

With all the good help here, I've got the engine out, nicely on the stand and almost all apart. I don't like what I'm seeing so far:

a) The cam appears perfect; b) the lifters appear to be new, with a barely visible nick on only one; c) the rear main seal appears completely dry; d) none of the valves appear warped or burned; e) push rods look new; and f) the front lip of the pan, toward the center, was very wet with oil.

So, at this point it appears I replaced a few oil pan gaskets over the years trying to find an oil leak that evaded me each time. And now I've embarked on an engine rebuild partly due to that, and partly due to the PO saying his mechanic said the rear main seal was, in fact, leaking.

MAYBE I just missed that the only problem was the front sealing block area. I definitely had a short bolt in there, so that's not been the problem. I also had the torque correct. This all means, to me, that the pan must be distorted at that point. Either that, or the dry rear main seal is deceiving me. Almost all oil under my car was at the rear of the oil pan with a good bead of thick oil hanging on the lip of the front transmission cover. It's possible that all came from the front, after running along the sides. I just never saw it that way. Even when I saw oil hanging from some of the side bolts.

Oh well. I'll get new pistons and liners, and a bigger bore out of all of this. I'll report back on what I see when I actually pull the crank and examine the bearings. I'm thinking of what to tell my wife when the parts invoices appear on my VISA statement. Something like, "I've always wanted to rebuild an engine from scratch."

Years ago, while I was overseas for work, the wife called to say the oil gauge on the family chariot wasn't showing any oil pressure. After quizzing her about symptoms (no bad noises), I had her drive it gently to a service station. They confirmed it had no oil pressure, needed a complete engine rebuild, and wasn't worth it. But it still wasn't making any unusual noises, so I had her drive it home and rent a car until I got back.

Turns out, it had plenty of oil pressure all along, the gauge sender was the only real problem. But of course I didn't discover that until after I had dropped the pan (which required removing the subframe on that car), replaced the bearing shells and oil pump pickup etc. I sure felt like a chump when I fired it up after all that work and the gauge still just sat there!

PS, it's also possible for the TRactor motor to leak oil between the front sealing block and the front plate. You might want to double-check that area for any burrs, surfaces not flat, bolts wrong length, damaged threads, etc. I would install Helicoils in the sealing block.

So that brings up two more questions: First, are you saying install helicoils for 5/16 coarse bolts by drilling out the sealing block even if the sealing block looks OK (I'm not sure it wasn't leaking, but the sealing block looks OK); and Second, should I replace the entire front engine cover if mine has the classic gouging from the timing chain tensioner, a gouge about 1/32nd to 1/16th inch deep and an inch long?

Isn't there a plug on the back of the left side of the head that is prone to leaking aver time? It might account for oil under the battery (~ same level) and also could find it's way down to the inspection plate.