View Full Version : Reusing a Cam

05-16-2006, 04:53 AM
I have the cam from the TR3 engine sitting on my work bench and just looking at it, it looks like one I would have just gotten in from a vendor. All the lobes have nice, er, "lobes" and the gear has no visible wear or chips. How does one determine if a cam is reusable and can cams be overhauled, added to, or otherwise brought up to specs, assuming it is even out of spec. Are there nationally known "cam shops" that do such? I am aware of Crane and the likes but wasn't sure if they took work in like this. And would they have the specs for my cam, which at this point I don't even have.

I can't even find an engine shop close to home that will take various parts of my engine in for work. Every time I mention words like "line bore" or "British" they get glazed vision, mumble something and walk away. Think they have me pegged?



05-16-2006, 07:05 AM
I'm sure it's frustrating, not being able to find someone willing to work on your car, but it's better than finding someone who'll take your money and not do a proper job of it. So you still have your hard-earned $ and no one has messed up your TR. It's all good.

What do you really need to have done? Do you have a factory shop manual? It will give you measurements that will help you determine the condition of every part of the motor. Unless the motor was destroyed I'm not sure how much machine work is needed on a 4-cyl TR that's simply worn. What have you got going on that you think you need a machine shop? Line bore? Did she spin a bearing?

05-16-2006, 12:38 PM
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 (https://www.bpnorthwest.com) and TRF www.the-roadster-factory.com (https://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 (https://www.tsimportedautomotive.com), Ken Gillanders www.britishframeandengine.com (https://www.britishframeandengine.com), www.bpnorthwest.com (https://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 (https://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.


05-16-2006, 05:20 PM
Thanks Alan,
As usual, you have given a complete and thorough explanation. I asked the time and you told me how to build a watch. Right now, I needed those watch-building guidelines.
I am in the process of tearing the entire engine down. All I have left to do is get the cam bearings out and remove the
piston sleeves. I have already ordered the 87mm sleeves (Mahle) from TRF. If the engine does not work out, I know I can sell the new sleeves for what I will have in them. My big thrust is to have the crank Magnafluxed and if ok, I will have it hardened and improved. The block will be checked out in a similar manner. If all the major components are reuseable, I will proceed, over the next 6-9 months, to building a very nice engine, mildly hopped up (probably use SU carbs) and will keep a sharp eye out for the rest of the car.
The tranny is waiting patiently to be sent to Quantum, but only after the engine is a sure thing.


05-16-2006, 05:40 PM

05-18-2006, 12:33 PM
alan is right (of course). the lifters are usually the main problem. with new lifters you DO NOT reuse the cam without it being re-hardened. so you always have the cam reground anyways before you re-harden (just prudent). a good cam shop can do this no problem. they may even have the original profile on record as well (my local guy does-been in business since about 1949). the edges of the cam lobes will be chamfered slightly so the cam will not chip. my local guy parkerizes the cam and regrinds lifters and hardenes as well.some guys nitride the cam.look at a sample of their work.not all regrinds are equal.ask questions. there are lots of these shops out there.not just the big names.

05-19-2006, 08:53 AM
Thanks Rob and Alan,
I have seen a few well-worn cams in my day and the one that came out of this engine looks awfully good, no chips on any teeth and the lobes look quite good. Of course my eyes aren't micrometers and I could well be looking at a worn-out cam. It would be nice to reuse as many parts on this engine as possible, for posterity and economy and originality. Even the sleeves look good but that remains to be seen after close measurement. I really want to take the sleeves out so I can completely clean out the entire block. Cleanliness is next to godliness.


05-19-2006, 03:16 PM
Bill what I am doing on the tr3 engine I am building is putting the cam shaft back in after a good cleaning. It sounds like it was in about the same shape as yours. I showed to a couple of machinists that do not have a vested interest in LBC parts. The guy just gave it a good visual inspection and said put it back in with new bearings. He felt the original was a better cam than an after market. Hey Bill I am kinda of curious, on your engine did it have a shim for the starter motor?

05-19-2006, 06:00 PM

on your engine did it have a shim for the starter motor?

[/ QUOTE ]

Heck, I don't remember. I just pulled it off and let things fly as they may. My plan is to use a high-torque starter, when I get to that step....


05-25-2006, 04:19 PM
one last point,
if you re-use the cam,as is, AND the lifters are ok and NOT MIXED UP, then you could re-use.the lifters that came out MUST stay with the same matching lobe (they become a matched set after break-in).if the lifters have to be replaced,then you need a cam re-grind and hardening.

05-25-2006, 04:24 PM
Thanks Rob. I'm making a list of all these little pearls. Much obliged.