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Triumph TR6 - Engine rebuild questions

I think, based on Clive's advice, that I'm about to embark on a rebuild of the motor in my 1971 TR6. I am not competent to do it, but may help. Mostly, I rely on Clive's advice because he really knows cars and recently rebuilt his TR6 motor.

Do you guys have any suggestions of what to do and what not to do? For instance, adding the spin on oil filter adapter seems like a reasonable expense. Getting the radiator cleaned out good while the work is being done is probably a good, and inexpensive fix. Maybe changing out the transmission and rear end fluids while the motor is out would be easier for a not very competent mechanic like myself.

What stuff should I ask Clive about and what could I do myself while the motor is out?

Thanks, John
JL Bryan

One thing you should decide is if you want a bit more power out of the beast after the rebuild. If you are satisfied with the stock experience, then your choices (and budget) are relatively minor. If, like me and several others here, you decide that a performance boost would be nice, then I strongly urge you to consider raising the engine's compression in conjunction with a warm cam. You will not be disappointed.

Rick O.
72 TR6
Rick Orthen

one medium expense to consider is changing out the flywheel to a lighter unit...gains you 10% performance?
Bob Craske

Thanks. I guess I'm not really sure if I have ever experienced "stock performance" as this motor doesn't appear to have ever been redone.

Clive did some modifications to his motor, but I'll start making a list of what to ask him when he gets back from his holiday.

JL Bryan

John,
I'm just about at the same point as you regarding rebuilding the engine in my 71. I'll be very interested in Clive's recommendations as to what to do.
Bob, I do want more than the stock 105HP, but am unsure as to which mods give the greatest return with regard to cost and which will contribute to reliability and dependability. I'm most interested in maximizing the little critter's performance, but not at the expense of increasing the propensity to break down. In my parlance, I'd like to both dramatically increase the MTBF and Ao AND Performance.

Replacing all the bearings, rings, valve seats, valve stems seem to be a given. I've also considered balancing the engine, lightening the flywheel (by some means TBD), but don't have a list of do's and what you get for the do's and Don't's with what risks are invited with the Don't's. A great service to many of us would be such a list of what modifications do what and some index of difficulty/cost associated with each. Anyone have any such data already amassed that they are willing to share?
Doug Baker

Great idea, Doug. A list of do's and don'ts and some idea of the cost would be great.

For instance, some of the other things I have questions about:
1. Do we need special valves or pistons or anything for unleaded gas?
2. Is electronic ignition worth it?
3. How exactly do you improve the compression ratio and what is the risk?
4. Is there anything internal that it is wise to replace but not absolutely necessary?

Doug, I will let you know what Clive says or he might tell you himself right here. I think he has tweaked his engine when he rebuilt it so that it is higher performance.

John
JL Bryan

John, with Clive's input, maybe we'll get some response on this. I understand that unleaded gas needs the bronze valve seats, but then someone commented that at 10K or less miles/year, don't worry about unleaded gas. Again, as I understand it, as you push to the right of the performance envelope, by increasing the CR, engine life becomes increasingly shortened. I assume a fairly linear relationship with CR and engine life up to some point, then I guess it turns up more sharply. Where's the knee of that curve? Of coures, you don't want something to last forever if it's sluggish and ill performing so I'm confident that someone has the data that would offer an optimum tradeoff between CR, engine life, performance, cost and degree of difficulty to achieve. Steve Pike could probably describe those relationships and that curve off the top of his head, as can many other bright minds on this BBS. As I have pursued this adventure, I've noted the excursions I've made from stock and there are many, but nearly all very minor. Most have to do with protecting against corrosion and deterioration or comfort and convenience. Now, I'm ready for performance.
db
Doug Baker

John,

By the sound of your posting it appears that whatever you choose to do to the engine....modify or stock..you'll have someone else do the work and you are wondering what to do while the engine is out. I think.

One thing I would suggest is to clean and detail the entire engine bay. Obviously with the engine out you can do this to a level that you can't with the engine in. Of course any front suspension work would be easier with the engine out. Definately change the trans oil while it's easy. Grease or replace the drive shaft U-joint...again, easy to get at. New plastic trans cover?

For what it's worth, I rebuilt my engine and had to stay within a budget. So, for me leaving stock was the only thing and I'm quite happy with it. But then I'm more into originality than performance which of course is a personal preference. If you're into performance then now is the time to go for it.

Good luck.
Henry
HP Henry Patterson

Given the nature of the base questions, my first advice would be to get thee to your local public library. It's free and usually doesn't smell too bad. Odds are good that they will have books on hot rodding, building up motors, etc. Just forget that the title says something like "How to Hot Rod Your Small Block Chevy." The principles are the same. It will get into how to degree that cam, cc that combustion chamber, find top and bottom dead center, match ports and all the other fun stuff. Even a "stock" motor can be helped by applying the same principles.

From a bottom end standpoint, proper machining, balanced components and good assembly practice are the the best things you can do. Learn to use Plastigage on your bearing installs. In selecting a camshaft, don't go too wild. Make sure that you use something that makes power in usable street RPM ranges if it is intended for a street car. Besides, the TR6 motor has a long stroke so it is easy to get to piston speeds that are too high. No point in a cam that doesn't make power until high RPM if you're never going to go there. Degree that cam, just don't throw it in there. You can use cam advance or retard to slightly alter the powerband. About the only thing in the bottom end that I can think of that you might be able to reuse might be the oil pump. Even that is iffy. If it is one of the later production styles they have a better pick up than the early ones. If not worn, I would probably reuse a late style. If it was an early style or if it was worn, it would be replaced.

The head is key, that is where power resides. Match those ports at the head/manifold interface. The Kastner book has a good set of instructions on opening up the ports. So does the Vizard book (on the TR6 CD as I recall). Here is your primary place to adjust the compression ratio, with the engine block being the next place. You will need to determine the swept volume of the cylinders, the volume of the combustion chamber and the volume of the head gasket. Take those volumes and add then together with the piston at BDC and then again at TDC. A pretty easy task with the flat top pistons in the TR6. That is your compression ratio. The head is the most common place to go. Determine what combustion chamber volume would get you to the desired compression ratio and calculate from the combustion chamber planar surface area how much thickness needs to be removed from the head. This is another area not to get too wild. For street use, I do not like to go above about 9.5 to 1 given the current state of pump gas. Get much higher than that and you have to think about running octane boosters, racing fuel etc. Depending on how much material is remover from the head, you may have to either shim the rocker shaft stands or go to shorter push rods to get proper action with the rockers and the valves. I like valve stem seals, others do not. If you want to run them, get the guides flycut to accept the seals. Spring selection is typically driven by the camshaft selection. From a no-lead standpoint, the stock valves are fine, but you will should have hardened seats and bronze guides installed. Those are available from "the usual suspects."

Electronic ignition is nice, but not necessary from a performance standpoint. The primary advantage of the Hall effect units (Pertronix) or the optical units (Crane)is that they are set and forget. A multispark box such as those from MSD or Crane along with a hot coil should be considered if you are looking at things from a performance standpoint. For myself it is Pertronix and an MSD-6AL.

As far as pulling the motor goes, on the TR6 I like to just go ahead and pull engine and transmission as a unit. We remove the bonnet and get as much ready to come out as possible while the car is on the ground. Then we get the car up on stands and remove the front wheels. The front is then positioned as low as possible while still able to get the engine hoist under the frame and adjust the cars angle by raising or lowering the rear. If you get the angle of the car right, you can pretty much finish out by removing the mounting bolts and pull the engine and transmission out level from the car, especially if it is a non-overdrive car. Installation is the reverse. Beats having to pull things loose, then try and adjust the angle of the dangle while things are hanging from the hoist.
SteveP

It's the valve guides that should be bronze or some material specific for lead-free as noted in the catalog of the supplier. Replace all 12 of them in a TR6 engine. If the engine is as you say, possibly never re-built, you should also change all the valves.

For lead-free operation, the exhaust seats will need to be bored out and replaced with steel inserts. Note that only the exhaust seats need to be done. When I had mine done, I offered to buy and supply these seats to the engine re-build shop that was going to do my job. He told me that he would prefer to use the seats he had in stock because his cutters to bore out the cast iron around the exhaust valve seats would give him the correct press fit diameter. I have read elsewhere where the new seats were not a tight press fit and shortly after the lead-free re-build of the head, one of the new seats came loose, fell down and rattled all around the valve and the head, bashing up the head and he had to get a new head.

No one wants that to happen.

I have driven over 40,000 miles since the lead-free inserts were done and have never yet had to adjust the valve clearance gap. But I still check them every 5,000 miles to see.

Don Elliott, 1958 TR3A
Don Elliott

........balance EVERYTHING, crank/con rods/pistons/flywheel/timing gears/drive shaft[VERY important]/glove box door/ignition key etc.etc.No increase in power, but the smoothness is not to be believed!! re the driveshaft........keep in mind that it spins at crankshaft rpm in 4th.

Good luck

Dale
Dale

Check any clutch components for wear. i.e. crosshaft bushings, pins on the fork, collar & the release bearing,etc.
If the hole is oblonged where the slave cyl. attaches the the cross shaft it would be a good time to take it out a have it welded closed and redrilled. I know a lot of the guys say that a low clutch is inevitable on a TR6. I can assure you that if you take the time to repair every wear point your clutch it will be the same height as a North American car. Mine is. When the engine is out is a good time to take care of it. You will be happy you did.

Doug C.
Doug Campbell

This thread was discussed between 08/06/2005 and 09/06/2005

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