View Full Version : TR4/4A Piston Liner Protrusion TR4

09-24-2008, 08:52 AM
I've got the head off my TR4A, and I'm not seeing any protrusion on one of my cylinders. Number 2. Instead of .003 to .005, I'm seeing what appears to be "zero" on this one. Very smooth to the block. The others are about .003, maybe even a bit less. I'd guess .001 to .002, but it's hard to use those paper thin feeler gauges.

Is this critical on the "apparently low" one, or will the head gasket take up any space or issue?

Also, does anyone replace pistons, rings and liners with the engine still in the car?

I'm not actually intending to go that far, because then it's rods, pins, thrusts and bearings, too, and I've never done that myself. One day I may tackle all of that, or sooner if someone tells me (or convinces me) I should. The car runs strong, and good. I'm just replacing a head gasket I never should've used, and noticing things along the way.

Thanks all.

09-24-2008, 09:15 AM
It's probably normal. The head is supposed to compress them into the block for a snug fit so they don't allow water into the oil.

Geo Hahn
09-24-2008, 10:06 AM
Well, ideally there should be a protrusion as this helps assure that clamping forces against the gasket are very strong around the edge of the cylinder.

I can see where your prior (solid copper) gasket might have had a problem with this. The stock crushable gasket may have a better chance at dealing with the absence of a protrusion.

Since (I think) the problem that has you removing the head was not attributable to this lack of protrusion perhaps it is not unreasonable to live with it.

The good news is... everytime I R&R the head I get better at it (or at least quicker) though I suppose this is not an exercise you want to get a lot of practice with.

09-24-2008, 10:07 AM
Disagree. The liner needs to stand proud .003-.005 to compress the head gasket to make a good seal. I suggest pulling the liner and replacing with a new FO8 gasket - you'll need to pull the adjacent liner as well. FO8 gaskets are avaiable in oversize (thicker) also.

If it has the original steel gaskets, they may have rusted. So try to get copper replacements. Might as well both FO8's (all 4 liners) while the head is off. Do not mix up your parts.

09-24-2008, 10:55 AM
Uh... getting those out while the pistons are in there and while the engine is in the vehicle sounds like it's going to be next to impossible.

.005 is, well, practically nothing, especially considering the thickness of the head gasket (.080). It was my understanding that it was the "plastic covered" Fo8 gaskets that were compressed, not the head gasket. But I'm certainly not the expert.

09-24-2008, 04:51 PM
This issue just came up on the team.net list - I agree, those liners must stand proud. Tony Drews with his racing and rebuilding experience certainly advocated it.


09-24-2008, 05:01 PM
IMO you will almost certainly have trouble later if you don't get the proper protrusion now.

You can leave the pistons in the liners while you pull the liners, if you want; but you'll have to take the big ends apart. And I wouldn't put them back together without new bearing inserts (although there's really no reason you can't if you want to).

I have changed bearings, pistons, liners, etc. many times with the engine still in a TR3/A. The motivation is stronger with a TR3, since removing the front apron to pull the motor is such a PITA. But if I was confident that I wouldn't decide to do the crank, clutch, rear main seal or camshaft (etc); I would probably go that way even in a TR4A.

Rod bearings and thrust washers are easy, no need to be afraid of those at all. Make sure everything is scrupulously clean, and double check the clearances. Pistons are a little harder, but still easy (you'll need a ring compressor). Front & rear main bearing inserts are a little trickier (I finally built a special puller to get them out) but still not bad.

The bad things about pulling liners with the engine in the car are:
1) Laying on your back with vital fluids and crud falling into your eyes while pounding on the liners.
2) All the crud from the water jacket falls down on the bare crankshaft journals (so wrap them well with clean rags before and clean diligently afterwards).

My "liner removal tool" is a 12" length of 1" water pipe, with a iron cap on one end and a hexagonal/flat brass cap on the other end. The brass is important to keep from chipping the edge of the liner. Just like removing a wheel bearing race, you work your way around the liner, giving a few taps in each spot. I use a "mini sledge" that is only 2 or 3 pounds, as I have trouble controlling a larger hammer for the length of time it takes.

I like Permatex #3 "Aviation Form-A-Gasket" for the Fo8 gaskets, and the felt packing around the rear main cap. Hylomar for the front sealing block, pan gasket, etc.

09-25-2008, 12:08 AM
Good advice but I've got questions. If I'm leaving the crank in place, will I be doing anything with the main bearings? What would I do to "main bearing inserts" or "thrust washers"?

I could check end float perhaps?

I like that pipe method of getting the liners out. Do you reuse your liners when you remove them?

If I have "low" or worn liners, and decide to buy a new piston and liner set, I'd just be tossing the old liners away I imagine.

Also, the end bushes for the connecting rods probably need to go to a machine shop, unless there's another way to work with them.


09-25-2008, 12:47 AM
If I'm leaving the crank in place, will I be doing anything with the main bearings? What would I do to "main bearing inserts" or "thrust washers"?Up to you. Both can be replaced without removing the crank. The thrust washers are easy, just drop the center main cap and poke the two upper inserts out with a piece of wire or something.

Getting the upper main inserts out is a bit trickier, but not especially hard. What I do is take one of the lower inserts and flatten it out (hammer on a block of wood) then use it as a drift to start the upper insert out (driving on the non-tabbed end, so the tabbed end comes out). Then pinch the tabbed end tightly against the crank with a thumb and turn the crank to walk it out.

Another method is to bend a cotter pin and stick it in the crank oil hole, so it forces the insert out as you turn the crank.

Either way, only do one main bearing at a time, so the crank remains supported by the other two bearings.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]I could check end float perhaps?[/QUOTE]Sure. That's an essential part of replacing the thrust washers, to be sure you are putting in the right size.<div class="ubbcode-block"><div class="ubbcode-header">Quote:]I like that pipe method of getting the liners out. Do you reuse your liners when you remove them?[/QUOTE]Depends on why I removed them. The removal doesn't hurt them, so they could be reused. The ones in my "now wrecked" TR3A have been removed at least 3 times that I know of (I bought them used).<div class="ubbcode-block"><div class="ubbcode-header">Quote:]If I have "low" or worn liners, and decide to buy a new piston and liner set, I'd just be tossing the old liners away I imagine. [/QUOTE]Although it's possible for them to be defective; generally a "low" liner is caused by something else. So you may be able to reuse them if that's the only problem. Also, it is soetimes possible to rebore worn liners for oversize pistons, which can be cheaper than replacing them.<div class="ubbcode-block"><div class="ubbcode-header">Quote:]
Also, the end bushes for the connecting rods probably need to go to a machine shop, unless there's another way to work with them.[/QUOTE]I've never had to mess with them. Perhaps I've just been lucky, but they don't seem to be a common problem area.

09-25-2008, 01:15 AM
You're saying you can replace all three main bearings on the crank, leaving the crank in the block? Can you please explain the "tab" again?

Any more info on "low" liners? Crushed Fo8 gasket? Two of mine really are level with the block, down there. I can see blackened surfaces from the combustion rushing across the top surfaces of the liners and block.

PS So what about the Cam? If I remove the distributor and the timing cover, does the cam just slide right out? What do I look for on my old Cam while it's in the block to decide whether to even bother with it. I don't want to succumb to my neurosis and go after everything all at once.

09-25-2008, 06:39 AM
Each bearing insert has a locating tab, that fits into a corresponding slot in the block, cap or rod. Hopefully this image from the Moss catalog will illustrate. I forget offhand which side has the tabs, but you can see them with the caps removed. The end that has the tab has to come out first, and then when you replace the insert, the other end has to go in first.

Probably it would be best to experiment a bit with one of the caps and it's old insert, to appreciate better how it slides into place.

Don't forget to smear the face of the insert with oil or assembly lube before putting it in; and be careful to keep everything as clean as possible. It only takes a tiny piece of grit to spoil things in a big way.

Also, I always like to double-check the clearances with Plastigage. Tear off a piece and lay it across the cap (with insert already installed). Install and torque the cap, then remove it and compare the crushed Plastigage to the chart on the package to see what the clearance is.

09-25-2008, 07:02 AM
For the liners, first inspect them and decide if you're going to replace them. Then do a trial assembly after cleaning, with new Fo8 gaskets. I think there's a good chance that is all that is required. If they are still low, then you can worry about how to bring them up (like thicker Fo8 gaskets).

But of course there are no guarantees for any of this stuff. You might get in there and find that a journal is scored or the block is cracked or any number of reasons that the engine has to come out after all.

09-25-2008, 07:18 AM
I've never done a cam in the car; but to remove it you'll also want the fuel pump, sprocket and front bearing out of the way. It doesn't just slide out (or in) either, the lobes and journals want to catch on the block. On the bench, it's not too hard to reach inside the block to support and guide it; but I'm not sure how easy that would be with the engine still in the car.

Perhaps someone else has done a cam in-situ?

Best way to judge cam condition (besides visual inspection) is to measure the lift. Get a cheap dial indicator &amp; magnetic mount ($20 from Enco) and check motion of each valve (before removing the head) or each lifter (with the head off). Compare them to each other, or the published cam specs if you have them.

09-26-2008, 10:36 PM
I did my 4A engine many years ago while in the car, pistons and liners and had the head done, previous owner had done the bearings so left those alone.

Not to hard really, chain auto stores will loan you a ring compressor free (you may have to leave a substantial deposit though).

Make sure you get everything clean for the figure eight gaskets, and everything else for that matter.

I worked in an apartment garage with a simple set of handle tools, not compressed air or anything fancy--but I sure had a lot more power and energy in those days!

Geo Hahn
09-27-2008, 10:56 AM
Randall (TR3Driver)... I did forward to Kentvillehound (I really must ask him about that name) your recent message from the Triumph list describing your technique of soldering 20 ga wire to the head gasket around each cylinder. I thought that was a creative and useful alternative for a 'driver' that has no need to be torn down other than an inadequate liner protrusion.

09-27-2008, 11:12 AM
No problem, Geo, but I think I should point out that I went that route only after pulling it apart and satisfying myself that the block was mis-cut.

I kind of hate to admit some of my DCO stunts (we won't talk about the shims behind the rod bearings) but that engine held up amazingly well with what were intended to be only stop-gap measures.

10-02-2008, 12:10 PM
Sometimes the liners are STUCK. You may need the block stripped and out of the car to have them pressed out with a hydraulic press (do not hammer bottom of sleeves) you need a steel plug to go in and over the sleeve to press them out. You could put on a stock head gasket temporarily, but i would plan for a complete tear down.
I like everything to be super clean before any kind of re-assembly so the engine would need to be hot tanked, magnafluxed,and clean clean clean. Don't mix-up any parts, none. Might need to deck the block also.before you dis-assemble, measure measure measure-top of sleeve to centerline of crankshaft for each cylinder, top of each piston to top of sleeve, thrust clearance on crank, all bearing clearances. inspect every single part, all. make sure to heck cam and lifters, rockers and rocker shaft for wear-typically bad.
then you know what you have.