Welcome to our resource for MG Car Information.
Triumph TR6 - ENGINE REBUILD
|Just finished stripping my 71 engine. Took messurments of the crankshaft journals and the can lobes. dont really know what to look for. How much can they be off and still be reuseable.|
Also, what should my next step be. This is what i think i have to do:
1) have engine block magnifluxed for cracks.
2) have machining done to the block, hone cylinders, centre hone block, check rods for trueness etc.
3)regrind cam and crank
4)get new valves and seats for head
5)plane head and top of block
is there any thing else i should have done?
Thanks in advance
Lionel Caledon East Ont.
|Balancing is highly recommended.|
|If you're just planning to have a great touring TR, as opposed to racing it, you might want to ask others here if they usually magnaflux a block for a TR6. If it doesn't cost much, then go for it.|
If they soak the block to get rid of all the rust and crud in the water passages, ask about the chemical they will use to do it. Some chemicals are so agressive that they will eat away all your core plugs. Worse still is if it only eats a small hole in one or more of the core plugs - then you'll lose you coolant and it'll really be hard to fix that after it's all back in the TR.
Why do you want to re-grind the camshaft ? Has it got real heavy scratches or obvious wear marks ? I've driven over 150,000 miles and never had my camshaft out the block.
By "check rods for trueness", do you mean the con-rods ? You will want to "roll" your push rods to see if they are still straight.
When you go for the inserts in the head, you only need to have them put in for the exhaust valves if you want it to be a lead-free head. When I had mine done, the machine shop told me they would supply the inserts themselves because they had the tooling to machine the cast iron head correctly for their own inserts. You don't want an insert to come loose and drop down while you're running. BANG! I've driven over 27,000 miles since I had mine done no problem. Do as I did. Change all the valve guides as well as all the valves. Make sure that the valves are for lead-free gas.
Balancing consists of making sure all six pistons plus conrods and bolts all weigh the same weight. Dynamic balancing of the engine should also include the flywheel, clutch lining and the clutch pressure plate.
Skim the head but why do you want to plane (skim) the top of the block ? How much do you want him to skim off ?
Don Elliott, 1958 TR3A
|Thanks for the feedback.|
I thought all connecting rods had to be checked for trueness.
The push rods i thought had to be checked by the machine shop.
I also thought that both the head and the block had to be skimmed so that the mating surfaces would fit perfectly.
I know the block has to be cleaned and i also thought is was false ecomomy not to check for cracks.
My crank had bearnings break up on rod no. 2, not only is it scracted but i took measurments and there is quite a bit of difference between this one and the others. It was worn down abit. i am hoping regrinding and putting in oversized bearings will make it useable.
ps. do people reuse the cam followers or does one buy new ones.
|When I re-did my TR3A from 1987 to 1990, I redid the engine too. New pistons, wrist pins, ground the crank and new oversize bearings. The original con-rods went back in. The original push rods were not bent so they are still there.|
I also put in a new timing chain and tensioner.
As long as the top of the block is clean of all gasket residue as well as goo residue, it should be OK. To have a machine shop skim the top of the block, you'll have to remove the head studs. Hope they come out OK. If you get them out, buy and install new ones. Mine are the originals.
I bought new head nuts that the racers use - from Ken Gillanders in Temple City, Calif. e-mail:- BFEKENG@aol.com These are 7/8" high with 14 threads instead of the original nuts which are only 1/2" high with 10 threads. The higher nuts hold the torque better. I've had mine off a couple of times and still re-used them. With the head off, run a new nut down the threads at the top of the head studs. If they run OK, the studs are not over-stretched. If the nut is hard to go on, it may mean you need to change your studs too.
I replaced two of my cam followers. After you take them out, they should have a circular pattern on the bottoms where they rub on the camshaft lobes. Their centerlines are offset to make them rotate. If they look like they have a hollow effect or curved groove across the bottoms, they were not rotating on the cam lobes. Two of mine were like this. I lapped the "spirals" off the bottoms with 600 grit wet/dry paper on flat glass. If you buy new cam followers, you will want someone to check the Rockwell hardness of the new ones as well as some of the old ones. The new ones should be as hard as the old ones. There was a rash of cam followers a few years back that were not heat-treated and caused a lot of grief to many who re-built their TR engines.
Take out the oil pump and check it for wear. If you buy a replacement, make sure you ask for one with a drilled cross pin. Some are only knurled on the OD of the pump shaft and the "knobbly" pump part is only press fitted onto the shaft. If it comes off, oil pressure is gone in a second. Also, to put a knurl on the shaft, they use soft mild steel and the shafts wear prematurely and the steel shavings get into the babbitt in the bearings. Mine was like this from 1990 to 1995 (43,000 miles). The original pumps as shown in all the parts manuals show the cross drilled dowel pin. These have the shaft made of hardened steel and they last for years.
As for the rockers, mine are the originals. But I file off any grooves on the curved part where they push down on the end of the valve stem. If you don't, they will still work, but your feeler gauge will tell you that the valve clearance gap is OK (say 0.010") but because of the groove, the gap might actually be up to 0.020" if the wear groove is 0.010" deep.
Get more reponses from TR6 owners before you finalise all your decisions.
Don Elliott, Original Owner, 1958 TR3A (over 150,000 miles)
I don't know where your at in the strip. But too far would be a guess.
Unless your just doing a simple refresh of the engine in the car. Cylinder hone /new rings, maybe head sent out complete for work. These all depend on mileage and condition of engine.
Its almost always best to find your shop first. Experienced on these engines and reputable. Ask them what state they want it in with a good description of problems and your expectations. They will most likely want it drained of oil but intact. The engine builder taking it apart can feel problems and takes him less time in long run.
Trying to answer questions without writing a book.
Measurements can't be off period. On the crank a 6 point check of each journal is priority with a good micrometer and skilled hands. That do it on a daily basis. I have a diploma on the wall that says I passed all this in 72. But never did it on a daily basis. In reality that gave me enough knowledge to seek expert daily done advice at the right time.
If you have pulled the cam and probably have your Tappets/ followers or lifters stored in a bag or box without knowing exactly where they came from you can't re-use them. Your cam should likely be replaced as well for the price. Let them get parts yours won't warranty even from same supplier.
1: Magnifluxing won't hurt. Expensive and only done after a thorough tanking. Usually not done on street engines. Unless there is a known problem that can't be visually found. Core plugs should always be replaced. Oil and water passages cleaned.
2:A: If you have gone this far a simple cylinder hone might be a waste of money? Let them decide by there measurements. A rebore/ oversize pistons and rings may be required? And lots of bucks. These cars don't usually have high milage so a rim and hone, new rings may do the trick?
2:B: Truing the block etc.? May be required? Depending on why they find 2 bearing went left. My guesses would be.
1 Thrust washers shot. 2 Quick bad rebuild by DPO. 3 Overheated or lack of oil. 4 just plain old wear. 5 Wrist pin in cylinder worn/froze. Crank regrind and oversize definately. Let them do and assemble bottom end for warranty!!
3: As far as the head and block surface go the shop will check that and advise.
New timing chain. Oil pump definately!
4: I don't know what condition the head is in but a general rebuild is good. The machine shop will advise on what needs replaced in most cases. Don't start throwing parts at it without pro advice.
The biggest trick Lionel is finding a shop that treats it as a standard rebuild and not a high buck Brit. This is "not" a Jaguar engine. Some outfits treat it as such though because to them its a major P in the A taking up space and time waiting for parts. Some companies rebuild factory engines tractors fork lifts etc. and may be your best bet. Unless you plan on going racing or have a Gold Card just waiting for some major damage. Last time I checked in specialty shops a slightly hopped TR engine rebuild was going around 4G US?
I have probably missed quite a few things I should suggest but thats a start.
What was the problem in the first place and what kind of milage did the car have.
|my problem with my engine was do to no. 2 rod bearning breaking up. it happened 1 mile from home, i continued home (matter of pride) now matter of $. the no. 2 journal on my crank is at least 30 thou. smaller but not scraced up!|
i have decided to redue the entire engine since it is out and my car has a swap meet engine in it now, which runs ok. i am in no rush, but i am going to do it now under my own steam.
lionel 73 tr6
|Lionel - If one journal on your crankshaft is 0.030" undersize, I suggest you take it to a good engine re-build shop and ask them for their opinion. It would be an advantage for you to use a new crankshaft and you won't have to grind it for new bearings.|
If you can find a good used one, it might be cheaper but you would still have to pat for the re-grind. If you find one, use a micrometer to measure the diameters. If this used one has been re-ground 3 times, it is also undersize and can't be ground again.
Alternatively, ask about plating that journal with "hard chrome". Then the crank can be ground to accept the new bearings. If you go the latter route, ask about plating all the journals and re-grinding them all back to "new" dimensions.
Don Elliott, 1958 TR3A
|Thanks, i will be taking it in this week and i will ask the shop.|
wish me luck
|Finally got some time and took out my crank and cam. Both are regrindable. 30thou on the rod journals, 20thou on the rest.|
My question has to do with thrust washer wear. The block looks good where the thrust washers sit. Put in a new set of standard washers, put the cap back on and the washer was wider than the cap. I think this means that the block is ok. Also there is no scoring and bothe the front and the rear thrust grooves are equal.
My question relates to the bearing cap. The side that faces the front of the engine is shinny. The rest of the cap and all other caps are a pale black color. Ther is also some scratches on the lower part of this cap. My crank is not worn in this area. I do not know if the crank made this cap shinny and if it caused these scratches. I dont know how the crank could do this since the thust washers were still in place, but they were in the wrong way. With the oil grooves facing towards the bearning.
|Is the engine out and torn apart?|
This is quick very late. Thrust washer worn down or lost in its previous life. Polished rear cap front face. Shifting of crank back and forth with clutch. Polish happens when clutch disengaged. Does a nice job to.
Standard set improperly installed and maybe undersized? With nice new tight bearings. Crank still shifting with clutch. Blown main bearings from taking lateral thrust from clutch. May require oversized washers which are available. Do a crankwalk test. They say 4 to 6 thou. is perfect more than 4 and under 13 is normal in the real world.
Lionel I try to do everything myself to. As do all the rest. My last post may have seemed hard nosed. Over the last 40 years I have built some real good engines Hot Rodding and some very bad ones as a hobby. What I tried to say before is that one missed thing building an engine can realy ruin a great day.
|Lionel-Just a thought about plugs.I think Triumph used aluminum plugs on the ends of the oil gallerys and some other locations. These will magically disappear in the hot solution. If the engine has been hot tanked in the past, these will probably been replaced with steel allen head plugs.|
|Yes Don all taken apart, Crank and Cam are off being reground, buying various things for rebuild that are on sale. Will be sending block in for machining if it is ok. Still yet to determine if the bearing cap, the shiny one that covers the thrust washers is ok.|
|I would seriosly (SIC?) think about having the thrust washers pinned.|
|I agree Don thats the route I will be going unless I decide on the V8. Jurys still out on that.|
I have the polish on my cap as well Lionel and the engine ran strong. Damage to the block area is the main concern. The first indication of thrust bearing failure was car on steepgrade at edge of driveway at idle would not shift into reverse. I knew all was ok in the clutch area. And everything worked fine on the level. Put on the beany cap and came up with crank mass shifting back overcoming clutch release value. Taking it apart I found a mangled thrust washer in the bottom pan.
If at some time this has happened to your engine and someone put in a mismatched set of thrusts or just tossed in the standard set without checking endplay. Bad or shifting vertical alignment piston to crank will cause major problems with mains.
Just some points to look for. Hope it helps.
|Thanks Bill, My thrust washers were in place although they were put in backwards(grooves facing each other)|
The front one was about a third worn, the back one is brand new looking. My concern is finding out if i have to get the cap fixed. I can find no block damage i have looked for scrape marks in the block and can find none. So are a few scrape marks on the polished bearing cap a reason for concern?
Here is a sight that has a lot of info. I will take a look at mine sat. and see if I can give a reasonable answer without being able to see it.
|Just got my crank and cam back from the machine shop. Had my cam made into a 270, a bit hotter than standard. Anyway, i may not get the block done for a while, need advice on how to store the cam and crank.|
Thought i would take engine lube a rub it all over both, then put them in garbage bags then wrap them in cardboard.
Wondered if putting them in garbage bags would promote rust? Any suggestions.
Shop should have returned in boxes wet???. Did they just hand them back to you? You might try the baggy thing but load bag up with Quart oil first then turn with parts in and check often. Parts precision machined will have sharp edges don't leave under the bed? If you drop or something drops on it? Most parts are returned in boxes. Shop wants them back but if you explain its a long term build some sort of deal is struck. From other posts if your looking at quite awhile I would buy a plastic container big enough to fit both. Make a holder to seperate and lift off bottom secure cover with oil. Then your safe.
|Thanks again Bill.|
A minor, but important point:
If you do have the top of the block skimmed, make sure that the shop has counter drilled the stud holes, to remove the top turn of thread. If the studs don't bottom in the holes, they impact on the last turn of thread. If this is flush with the block top, it deforms and lifts a rim of metal around the hole - doesn't do the block/head seal any good at all.
On block skimming, I agree with above (Rick?). No need to skim, unless obvious damage, history of gasket leak, or if you want a 100% racing engine, to 'deck' it and the pistons.
This thread was discussed between 16/02/2003 and 20/03/2003
Triumph TR6 index
This thread is from the archive. The Live Triumph TR6 BBS is active now.