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Engine Rebuild Suggestion

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TheSearcherMan

Jedi Trainee
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As there seems to be alot of people rebuilding engines in this forum, I have a suggestion. The first time you have your valve cover off, after your initial cam "run in", check to make sure all your push rods are spinning, as they should be, when the engine is running. If they are not, this could be an indication of problems later on. If a lifter is not spinning, it will certainly develop a groove from the cam hitting it in the same spot all the time. I am sure some of you mite be in for a surprise. If "they" are not going to do any quality control, guess we will have to do it for them. I would recommend you also check this in a few thousand miles.
 
I have lapped 3 or 4 of my original cam followers on the flat end at least twice when doing the last two rebuilds. I can't say if they were the same ones because there was a 17 year period and 94,000 miles between re-building the same engine.

My cam is the original one that was in the engine when I bought my TR3A new in 1958. But for the last year, I have added GMC AC Delco EOS to the oil to increase the ZDDP level for older flat tappet enginges like ours to prevent new cams etc. from wearing out in a few 1000 miles.

There have been problems for years with repro cam followers where they were not hardened and this caused pre-mature wear. The race guys buy them from some supplier who guarantees that the cam followers have been properly heat treated to "Hardness C-58 - 62 on the Rockwell C Scale".
 
I can see how one could check to see if a push rod were spinning but how the heck can you tell if your tappet is spinning?
 
Bill,

I don't think that a push rod will spin on a solid lifter engine unless the lifter spins first. Hydraulic lifters, that are spring loaded can actually help assist in the push rod turning, but that really doesn't accomplish anything. It's the lifter that needs to turn and I think that Searcher meant that, but the only way to see it is to look at the push rod.

EDIT:

I will be looking at mine next week when the valve cover is off to retorque the head and readjust the valves.
 
The lifter spins the pushrod, so if the pushrod is spinning so is the lifter. It is my understanding that the offset on the cam lobes in a TR6 are what causes the lifter to spin, thus spinning the pushrod. A flat lifter will spin in a TR6, and I am not sure there is any crown on TR6 lifters. I should have clarified that the lifter spins the pushrod, and the cam spins the lifter. The problem is that apparently, some suppliers can no longer get the cam lobe where they should be, and then they apparently blame it on the lifter holes not being bored in the right place.......I would like to know if all 12 of yours spin Mr. Brosky, when you do your adjustments.
 
Searcher,

The key, as you say is the grind radius on the surface of the cam AND the tappet. Technically, neither should be perfectly flat.

I don't know what I'll find, but time will tell.
 
I am not sure what you mean by grind radius. each cam lobe should be offset in relation to the lifter bore towards the front of the engine,this is what makes the lifter spin, in a TR6 engine. In other words, if you look down thru the lifter hole, the lobe will be towards the front of the engine, not centered. If it is not toward the front or rear of the engine, the lifter won't spin, in a TR6 engine. The lifter does not have to be crowned. This information came from a very popular supplier. By the way, you can't be PMed.
 
That's odd, my PM works for others?? Hmmm.

In any event, I was shown several new cams that have a crown or very slight (.00?") radius on the surface to prevent a dead flat contact of a lifter. This reliable source said that if both were perfectly flat to flat, the cam lobes and/or lifters would be gone in a few thousand miles or less.

I was also told that this helps to rotate the lifter.

I did not look at them under a scope or measure them in any way. His word was good enough based on what he does and his experience.
 
That was my understanding also, before I talked to the "supplier". This very popular supplier is aware of the lifter not spinning problem. So, it looks like another case of a supplier who supplies "questionable" parts. Where does that leave the ones who have this suppliers parts in their engine? This only applies to the TR6 engine.
 
Searcher,

I was looking at some cams for classic Ford and GM engines, not Triumph engines at the time. But I did start to question the supplier that I was buying mine from BEFORE I bought it and he explained the same theory to me as the machine shop did, before I got the question out.

That's why I ordered mine from him.
 
I have always been told the same as your machine shop is telling you, my machine shop with tell me the same thing. What I am saying, and I intend to find out, the supplier I talked too says its not done that way in a TR6 engine, I will check into what they told me, as I don't think they would do theirs different than the others. I suspect the cam blanks are mostly coming from the same place, and that determins lobe location, in other words, I could buy blanks, have them ground to my specs. , put it in a box, and put my name on it. This is not the first time I have run into manufacturing issues with this supplier, so, needless to say, I can't do business with them anymore. I may name the supplier, I'll think about it. I will also say this, they don't try to cover it up with me, they admit the problem.
 
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