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Triumph TR6 - replace rings while head is off?

The head is off my 109,000 mile engine. While the head is getting rebuilt, should I push the pistons out and change the rings also? The engine was running pretty good, just maybe some worn valve guides. Oil pressure is high after bearing replacement. I figured now might be the time while I could get to them. There are no ridges at the tops of the cylinders so they could pop out. Cylinder walls look good and smooth. Can the cylinders be honed for the new rings with the crank in place? Never took a compression reading before I removed the head. I will be sticking a hotter cam in there also. By the way, when I checked the lifters, 2 were bad. One was really beat up on the bottom and the other had a large pit on the face like it was whacked with a small chisel. All lifters will be replaced anyway. So what do I do? Just do the top end or also replace the rings. I guess the rods could be rebushed also while the were out.
Steve Hazelfeldt

Steve,

At 109k that engine is probably pretty tried. My experience has been that once you start rebuilding an older engine, you need to go all the way. If you rebuild the head today, the rings will soon go because the head is now tighter and placing more pressure on them.

In adding a hotter cam you are again placing more pressure on the rings and lower end. How are the thrust washers? Crank end play?

For what it is worth, while I do know people that will hone the cylinders with the crank in place, I am not one of them. Just too many little metal pieces going places that cannot be seen.

Don
Yellowdog

Steve
In a nut shell you are asking "can I rebuild my engine with it still in the car"?
First off, you will need to remove the front end of the car if you pull the cam out. This includes the front cross brace. Yes replace your tappets (lifters). You may as well do the push rods while you are at it. Not sure here (not an engine expert like others on this BBS) but maybe both tappets and push rods require replacement with a hotter cam. Also maybe better to go to roller rockers??
You know if you replace the rings the cylinder walls must be honed. It can be done BUT! I would not want the "crap" falling onto a new set of lower end bearings. Drop the crank?
New bearings lower end (both mains and connecting rods I presume) should always include new thrust washers. Did you do this? Again, not sure if it is a good idea to pull the crank with new bearings just getting themselves nicely seated.You do not mention year of your 6. If it is before '72 then the oil pump should be replaced. Probably a good idea regardless of year with 109K on it.
Steve, just finished this entire process but my engine was out. I would not do it with the engine still in the car...IMHO
Rick C
Rick Crawford

I agree with everyone that you'd be shortchanging yourself if you don't bite the bullet and R&R the engine. You really need to tank the block to remove all the sludge and crap from the coolant and oil passages (you mentioned high oil pressure--maybe some arteriosclerosis going on in your block??)

Rick O.
72 TR6
Rick Orthen

Thanks guys for your input. Yes thrust washers were replaced. Standard size and end play was fine. also relaced oil pump recently, oil pressure is very good. The engine is a '74 and never rebuilt. Was running good before the head was pulled. The only reason I pulled the head was because I dropped a valve lock down the engine when I was putting those little rubber o-rings on the valve stems. Since the head is off I figured why not get it rebuilt and add some real valve stem seals and better valve guides. I hate to pull the engine for a total rebuild when I don't think it needs it yet. Anyone have experience with sticking new rings in with motor in car?
steve h

Make sure that the new cam followers (tappets) that ride on the cam have been hardened. There have been nasty stories that many of the re-manufactured ones where left soft. They only last a few hundred miles.

Don Elliott, 1958 TR3A
Don Elliott

Many years ago, I worked in the engineering dept at a major piston ring manufacturing company which included service engineers working with everyday garage mechanics. One piece of simple advice sticks in my memory and I've followed it every time I replaced rings. Before you put the re ringed pistons into the bores, wash the cylinder walls with hot water and detergent. The idea is to clean the pores of the cast iron. Occasionally, rings fail to seat in and seal as they should and the cleaning would help prevent this from happening. Of course, the bores should be well oiled after the cleaning, before putting the pistons in, and yes, new rod bearings as the increased ring friction will surely put more pressure on the rod bearings. That's a given.
Kyran Mackey

Steve-Measuring the bores and the crank might be the deciding factor as to pull the engine and overhaul it vs just replacing the rings. If the bores are round, not tapered, and not worn enough to warrant reboring, and the crank doesn't require regrinding, then new rings, bearings, and a valve job might make sense. The swarf created by reaming the ridge and glaze breaker can be contained by rags at the bottom of the bore, maybe some magnets, followed by a carefull inspection and through cleanup. Not as kosher as removing the engine and hot tanking, but I am sure most of us have done it and still slept well. In the old days, (before my time, of course), crankshafts were even re-ground with the engine in place by an auto machinist that made housecalls. Definitely something I would not be comfortable with.
Berry Price
BTP Price

I think replacing the rings is a good idea, you'll wish you had done it if you don't. Maybe coat the rags covering the crank with grease or spray upholstery adhesive or something else sticky to catch as much of the silicon and metal as possible. A lot of the metal dust you make will stick to the oil on the hone stones. Clean them often. It will be a pain, but should help you sleep better. Wash the cylinder walls with detergent and a brush (I hesitate to say a brush because they tend to fling stuff everywhere, but get into the hone grooves), oil and wipe until it wipes really clean. Maybe tape over the block/head mating surface. If you were paying your mechanic to do it, you probably wouldn't get such a good cleaning, but since it's your baby, I'm sure you'll be careful.

Or pull the motor, whatever you think is best. It's kind of hard to paint the block while it's in the car. And you can clean and detail (paint?) the engine compartment too.

I'd never heard of mobile crank grinding before, sounds interesting.
Tom

Guys, thanks for the great ideas. I think I'll remove the pistons first and measure the bores to see if they are still round before proceeding any further. If they look good I'll try replacing the rings and maybe have the small ends rebushed. The bearings were replaced about 4000 miles ago so I'll take a look at them and see how the crank is holding up. Yes it's not as good as a full fledged machine shop rebuild but I think I'll still be able to sleep at night. What have I got to loose by trying this? I figure at the worst I'll be out a set of rings and a gasket set.
Steve Hazelfeldt

Steve and all.... This type of "overhaul" is actually an old used practice in the past. As a kid I watched my uncle machine many crankshafts while still in the engine in the car. There is a machine made that does this and actually does a very nice job. Problem is cleaning out the oil-ways in the crank. As far as honing the cylinders (actually glaze breaking) it is still done a lot and is not a problem. We normally use thick plastic sheeting and wrap up the crank and seal it as best as possible. Also tape the oil feed holes for the camshaft. This way you can hone away and still do a very good job of cleaning up with soap and water, which as stated is the best procedure. Another thing to check is timing chain stretch. Only pull 1 piston and check for roundness and taper. My bet is you will find an issue with 100k miles and the cylinder will be egg shaped. If it is pull the engine! Steve
Steve Yott

Thanks for the advice Steve. Anyone have any idea what the limit is on the out of round measurement? Just popped out all 6 pistons today. They came out pretty easy. My friend has a bore measurement tool. Do I measure front to rear and side to side and check it at top and bottom of piston travel? Hope to check in the next few days. Timing chain was replaced about 100 miles ago. It was at max stretch.
Steve Hazelfeldt

Hey, Steve. I think if it's out of round you'll find it most pronounced near the top and on the sides. If you decide to pull it and need a hoist there's one in my garage.

Brent
Brent B

Thanks Brent! I should know by the weekend if I need the "Big Kahuna".
Steve H

Great news! Just measured the bores. They were all within .001. I was impressed at how straight everything was and each cylinder was identical. Looks like I'll try and just re-ring it. Thank you everyone for your help. Next question. Should I keep the compression stock 7.75 in anticipation of a supercharger?
Steve Hazelfeldt

Steve
Good news. You still need to de-glaze the walls. No answer on your question.
Rick C
Rick Crawford

I think you should keep as much material on your head as you can. It may warp some day.
Tom

This thread was discussed between 14/09/2005 and 17/09/2005

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