Hi Bill,
Often a used cam will have chips in the edges of the lobes and will be worn to give less than the original lift, i.e. the lobes themselves have gradually eroded down on the high point. This can be measured with precision measuring equipment, but most engine builders just have a cam reground or replaced as a matter of course.
The chips in the lobes can be repaired or ground away and, so long as there is some surface to work with on the "backside" of the lobes, the lobes can be reground to original lift specifications. There are many places that do this sort of work, but your best bet is probably to send the camshaft as a "core" to one of the Triumph specialists and they'll send you a replacement that has already been reground.
Of course, the cam bearing journal surfaces need to be in good condition too, without significant wear or out-of round (see manual and check particularly for a "gouge" down the middle where the oil enters the bearing). New cam bearings in the block will need to be sized to match, after the camshaft journal size is known. (If the block is "boiled" to clean it, also a good process, the bearing shells will need replacment anyway, along with the plugs that allow access to the bearings.) This is a job for a good machine shop.
A reground cam usually will *not* have been hardened and this is a very worthwhile thing to have done locally, again check with your local shop. This process simply helps prevent wear during initial startup (very rapid wear in worse-case scenario). A cam will "work harden" after running for a while, but the initial break-in can be scary if the cam is not hardened a bit in advance.
Many places can provide stock cams with its mild grind (roughly 245 degrees of duration, which is pretty conservative). British Parts Northwest
www.bpnorthwest.com and TRF
www.the-roadster-factory.com come to mind.
Many also provide "improved" grinds in the 260 to 270 degree duration range (also with changes in lift), which will pep the engine up a bit and is a good mod to do. Along with this, improved cam followers and slightly uprated valve springs would be recommended. These help the engine work well with the higher lift of the improved cam.
Improved cams are available from Ted Schumacher
www.tsimportedautomotive.com, Ken Gillanders
www.britishframeandengine.com,
www.bpnorthwest.com, and a variety of other sources. I'd recommend a modest upgrade, but not too much, if you want a pleasant but peppy street engine when it's done.
Keep looking for a local shop. As you can see, you'll need one! Look for "speed shops", engine builders and vintage car specialists. They will know how to do most of the work, since it's a dead simple engine in most respects. (The replaceable cylinder liners in particular make it very flexible and easily rebuilt.)
Note, even after boiling and any machining work on the block a lot of care should be given to cleaning inside the block, to insure no swarf or metal shards are left inside. Gun cleaning brushes can be helpful getting inside some of the oil passages, etc.
You will want a shop to carefully measure all the bearing journals on the camshaft and crankshaft. They will need to ream new small end bearings on the piston wrist pins and the cam bearings, too.
The block and the head need to be checked that they are perfectly level and planed if necessary.
It would be very worthwhile to have the crankshaft crack-detected and then balanced and shot peened if it passes inspection. The plugs in the crankshaft should be removed to clean out the oil passages inside. Newly ground journals on the crankshaft benefit from hardening, too, to help it live a nice long, life.
The rear seal of the crankshaft can be upgraded to the newer style, for much better sealing. This means grinding that area, too, seal kits are available from all the usual TR vendors.
The connecting rods are about the weakest part of a TR engine. They, too should be checked for any cracks, especially around the little oil weep hole near the middle of the rod. Keep them together as sets with their caps and where they were located in the engine. A machine shop can check them for straightness and twist, too. They can be lightened a little and should be shot peened, and the small end bushing will need to be reamed to fit new piston wrist pins.
Personally, I wouldn't take that engine that far apart without replacing pistons/sleeves/rings and all bearing surfaces, doing unleading work on the head (valves, valves seats... another machine shop job). The pistons/sleeves are probably 83mm in a TR3 engine, can easily be upgraded to 86 or 87mm at virtually the same cost as 83mm, to give a very nice bump in performance.
New cam followers are needed, or have the old ones reconditioned. The originals are sometimes better than replacements. Do not reuse old ones without reconditioning... if there are any imperfection in their faces, they can ruin a camshaft in the first few moments running when the engine starts up.
Pushrod length needs to be checked if there is any planing done on the head/block and to compensate for regrinding of the camshaft. Ted Schumacher and Ken Gillanders can provide pushrods in nearly any length (note, there are some TR pushrods that can be reused if nice and straight, but there are others that should be replaced because they are weak... the best are tubular with pressed in ends that allow the length to be changed, the weakest are solid with welded on ends and are a bit smaller diameter).
As a matter of course, I'd rebuild the rockers with a new shaft and bushings, at a minimum.
Back to the block, it's cooling passages must be checked to be clean and clear. The oil pump might benefit from reconditioning or replacement. The oil pump drive shaft can be uprgraded with a stronger one (recommended). The timing chain and it's gears should probably be replaces, along with the tensioner (Ken Gillanders can tell you which one to use and which one not because it commonly breaks.)
As you can see, there is a lot to think about when rebuilding an engine. Rusticus suggestion to get a copy of the service manual is right on the money. It's essential for this sort of work. I also highly recommend Roger Williams "Restoring Triumph TR2, 3, 3A" which has extensive photos and step-by-step instructions for rebuilding this engine, plus many suggestions and recommendations.
It can also be very beneficial to read Kas Kastners TR4/4A Competition Tuning Manual for simple (and more complex) improvements he made to the TR engine. the separate competition manual is available at TRF, Moss and eleswhere. His two new books go further with a lot more up-to-date TR engine building/improving ideas and data, but keep in mind they mix in the tuning of Spitfire and 6-cyl. TR engines, some of which applies, some of which doesn't. These books are offered by some of the usual vendors, but also at
www.kaskastner.com
Overall, this can be a great learning experience! If you have never rebuilt an engine, the TR 4-cyl. is an excellent one to learn on because it's very basic and easy. There are a lot of important details and procedures with any engine rebuild (it's important to use cam and assembly lube, for example), however there are various good guides. Just taking your time, near-surgical cleanliness and following directions will get the job done quite well and can be very satisfying.
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