Aligning Cam shaft and Crank...Suggestions?

[LearJeff]

Everything was complete. My 1974 TR6 Total Rebuild Project (body off, from the ground up) was finally done. There she sat this past Sunday (June 11, 2006) on all four shiny new wheels. Our crowning acheivement, the 4-wheel discs proudly peeking from behind those sweet 16" Panasports! The first scheduled test drive was yesterday (Monday) morning. I couldn't be there for it but stopped by after lunch only to discover, much to my dismay, that Steve had removed the hood, the radiator, the front crossmember brace, the steering rack, the valve cover, the fan and pulley assembly and the timing chain cover...this didn't look good.

Steve reported that during the test drive, when put under any kind of load at all, the engine spit and sputtered, coughed and burped and basically all but gave up the ghost. Of course, we had idled the engine several times in the shop prior to the first test drive and it ran just fine. Even brief runs to 3500 and 4000 RPM sounded smooth and powerful. And remember, we're talking about a complete teardown and re-build with mostly new innards here. Steve's buddies next door at the engine shop did all the work and they have always done excellent work for him in the past. Upon closer examination of the timing marks (after removing the previously mentioned stuff) it appears (possibly?) that the cam shaft and crank were not properly installed/aligned at the shop. The Haynes Manual is mostly pathetic regarding this topic, with its cruddy pictures and ambiguous text.

A couple of folks at Moss were very helpful yesterday, but I was hoping someone here might be able to refer me to a good printed resource or offer up their own words of wisdom. Thanks!

 

[piman]

Hello Jeff,

a quick and basic check for most engines, set the engine to TDC no. one cylinder, with no. 4 (or 6) cylinder rocking on the valves. Turn the engine back and forward about TDC and you should see the no. 4 valves opening and closing. You are looking for both inlet and exhaust valves to open at an equal angle from TDC. In other words at TDC both valves should be open slightly an equal amount. Another way is to set the no. 4 valves with a wide valve clearance say 0.040" greater than stock then measure the clearnce at TDC, both should be the same (Given that stock clearance is equal in and ex)

Alec

 

[Bruno_69z28]

Here's a link to cam timing.

https://www.ridgenet.net/~biesiade/camdegree.htm

The triumph cam sprocket has four different locating points. It's been a while but I think each locating hole is aprox. 4.3 deg.. Did your cam come with the spec. for cam timing? I set mine at an extra 2 deg. advance to compensate for chain wear. You will need a degree wheel and a dial indicator to check your timing the right way. The
Bentley manual will get you very close.

 

[vettedog72]

Sounds like your saying the motor runs smoothly at idle and runs up in no load RPM's smoothly but missies under load. I hope he checked the ignition including the plugs, wires, points, cap., etc. and the fuel system including the floats and fuel pump and gasoline quality for freshness or water.

 

[Guest]

Jeff,
Are we dealing with a completely stock engine here, just a total rebuild? Just curious. What seems strange if the fact that they were able to crank it several times, and then run it up to 4000 rpm. A real long shot but if the cam setup was totally off, it is possible to crank one of these engines and have her run at high rpms and erase a new cam. Ouch! Your vendor (Moss?) would have given your engine guy all the specs for the new cam. New chain, sprockets, etc., right? Could be that the cam is set properly and something else has gone bad, like the distributor has lost it's setting or bad head gasket. I, for one, would be a little hesitant to crank a new engine and run it at that high an rpm, even for a short while. Others see it differently. Just check your spec sheet and make sure that TDC is really TDC as Piman said; you probably don't have index marks on your new sprockets anyway so you will have to transpose from the old sprockets.

It could be so many things.

Bill

 

[Bruno_69z28]

Jeff

In my post I was referring to a TR-4 motor (sorry). I don't know if the TR-6 motor cam sprocket has the same design. Cam Timing is the same for all motors and should be done even if there are timing marks on the sprockets. There can be a wide range of timing. This small amount of timing can give you more torque or more horsepower depending on which way you time the cam. My new cam sprocket from Moss was not machined properley. I only had two choices for cam timing. I didn't want to wait another week, so I used the old one. It actually gave me less chain flex than the new one. Since you have the motor pulled apart, just check the timing, and if it's on, you can try other fixes.
With new cams you should always start the motor, confirm oil preasure, and run the motor up to 2000 rpm's for 20 min. to break in the cam. The cam won't get enough oil splashed on it at idle.

Bill

 

[Terry_Geiger]

Were you running with the air cleaners on or off? If you have the gasket reversed on the air cleaner it will cause eventual starvation of fuel. Symptoms are the car will run fine with no load but when you load it the engine will literally run out of fuel because the gaskets are on backwards not allowing the fuel bowl to vent and take in sufficient additional fuel from the fuel pump.

 

[LearJeff]

Thanks for all the great feedback you guys. I just ordered the Bentley Manual today and it will be here tomorrow!

As far as initial start-up and break-in, it was started and run for 15 min. at 1800 RPM, four separate times. Oil pressure comes right up as soon as it fires up. On the fifth start, it was run at idle for 5-7 min. until Oil temp stabilized. Then, the throttle was "blipped" to 3,000 RPM and then ran at 3,000 RPM for about 3 seconds. Then the same procedure was done at 4,000 RPM, but only for about 1-2 seconds.

The engine is mostly stock with some VERY minor upgrades. Not even upgrades so much as improvements. New cam shaft, new sprockets, new chain, new pistons, all new gaskets, new valves and springs, new plugs, new wires, new coil, new cap, rotor, condensor, points, new SU Carbs, new fuel pump, new (and better than OEM) racing-style fuel filter, etc. etc....Fresh Gasoline (high octane---the good stuff)...

I found a member post here that described in detail a procedure very similar to yours, piman. We did it today and discovered the engine shop had the cam shaft sprocket 180 degrees off. Ouch is right, Bill! I'm hoping for the best. I'll post here when it's back together and let you all know how it turns out! Thanks again, everyone!

 

[Guest]

Jeff,
You really should get yourself a Kent or Crane cam degreeing disk. Little plastic wheel that will show you all you need to know about the stoke of an engine and what each valve is doing, when it is doing it and why. When you get an actual mental picture of the function of the inside of the engine, you can better set up and tune your own engine, now and in the future. Understand the geometry of the crank and cam sprockets and how they affect the action of the valves will make you appreciate your TR much more. That said, you may already possess this knowledge and I am preaching to the choir. But think about this, if the engine builder did indeed set your cam wrong, then he should consider having the grind on the cam rechecked for damage as well as consider changing the cam followers. Damage to an engine can almost be instantaneous, though these little tractor motors are almost bullet proof. I would insist on having the cam checked by a cam shop before reinstalling it. But that's me. I don't mean to make a federal case out of this but he should have known better.


Bill

 

[Bruno_69z28]

[ QUOTE ]
Jeff,
You really should get yourself a Kent or Crane cam degreeing disk. Little plastic wheel that will show you all you need to know about the stoke of an engine and what each valve is doing, when it is doing it and why. When you get an actual mental picture of the function of the inside of the engine, you can better set up and tune your own engine, now and in the future. Understand the geometry of the crank and cam sprockets and how they affect the action of the valves will make you appreciate your TR much more. That said, you may already possess this knowledge and I am preaching to the choir. But think about this, if the engine builder did indeed set your cam wrong, then he should consider having the grind on the cam rechecked for damage as well as consider changing the cam followers. Damage to an engine can almost be instantaneous, though these little tractor motors are almost bullet proof. I would insist on having the cam checked by a cam shop before reinstalling it. But that's me. I don't mean to make a federal case out of this but he should have known better.


Bill

[/ QUOTE ]

If the cam was installed 180 deg. off, this would put the cam timing off by a max. of plus or minus aprox. 8.5 deg.. I can't see this as causing any damage to the cam. Since the motor was started and running, it probably wasn't off that far.

Bill

 

[piman]

Hello Jeff,

"We did it today and discovered the engine shop had the cam shaft sprocket 180 degrees off."

I have just finished a 12 hour night shift, so may not be too sharp, but my initial reaction to that is that it doesn't matter, as long as the distributor gear is timed to the right cylinder, which it must be.
Going back to the engine at TDC 1\4 cylinders. Set the cam to rocking on number 4 (lobes will be a conventional vee) and number 1 will be on compression firing stroke. Turn the cam 180 degrees and the situation will be reversed, number 4 will now be on firing, (cam lobes as an inverted vee) so the timing is still correct.

Remember the Triumph four hole cam sprocket can be reversed to give an option of four slightly different settings.

Alec

 

[Guest]

So Alec and Bill, if indeed the cam was set 180 off and not the cam sprocket (which would give you just a few degrees off), how would the 1-5-3-6-2-4 firing order be affected. One would have to change the firing order. The offset in the drive dog would not allow the distributor to be set 180 off, only the sequencing of the wires. Many aftermarket cam sprockets come with only two bolt holts.

Bill

 

[piman]

Hello Bill,

the firing order is set by the cam and is unchangeable. basically I was saying that the cam rotates 180 degrees per crank 360 degrees and you have two pistons at TDC every crank revolution. If you look at the cam the lobes for those cylinder pairs are opposite in phase, i.e. they are 180 degrees apart so it doesn't matter. The drive shaft for the distributor is inserted to allow the distributor to be set to the conventional position.

"Many aftermarket cam sprockets come with only two bolt holts.
"
I wasn't aware of that and my view is that it is a poor reproduction in that case. The original cam sprocket is easy and simple and gives an adequate adjustment range for anyone except an out and out racer. Perhaps the replica vendors were not aware of the subtle angle difference between the two sets of holes?

Alec

 

[Bruno_69z28]

[ QUOTE ]
So Alec and Bill, if indeed the cam was set 180 off and not the cam sprocket (which would give you just a few degrees off), how would the 1-5-3-6-2-4 firing order be affected. One would have to change the firing order. The offset in the drive dog would not allow the distributor to be set 180 off, only the sequencing of the wires. Many aftermarket cam sprockets come with only two bolt holts.

Bill

[/ QUOTE ]

Bill your right, if the cam was instalded 180 deg. off, then the distributor would be off by 180 deg.. I'm not sure if the cam or the cam sprocket was off by 180 deg.. Since the car was running, the mechanic put the distributor in right. Remember, the crank is rotating twice that of the cam.

 

[trfourtune]

just a note,
don't trust any timing marks or existing pointer. find tdc with a micrometer or dial gauge. also,use a dial guage on the lifter to determine the timing of the cam. you will need an extension to reach the lifter. any other way is inacurate and pointless. /ubbthreads/images/graemlins/hammer.gif /ubbthreads/images/graemlins/square.gif
rob

 

[Adrio]

This may be a silly question, but it has nagged me before so given the topic here I will pose it.

If the cam were installed off a tooth (so that the cam - crank timing was off) would a simple compression check not show this. My thought is that the valves would not be closed at the right time and the compresion would be low on all four.

I welcome comments and feel free to shoot me down on this if I am out to lunch.

 

[piman]

Hello Adrio,

a compression check is very arbitary, so is not a very good check of valve timing.

It is far better and easier to do a physical measurement.

Bill\Bruno,
whilst the distributor has an offset dog, the distributor drive can be installed in any position, so the fact that the distributor can only go in one position on the drive will only be correct if the drive shaft is aligned correctly first of all.

Alec

 

[Bruno_69z28]

[ QUOTE ]
Hello Adrio,

a compression check is very arbitary, so is not a very good check of valve timing.

It is far better and easier to do a physical measurement.

Bill\Bruno,
whilst the distributor has an offset dog, the distributor drive can be installed in any position, so the fact that the distributor can only go in one position on the drive will only be correct if the drive shaft is aligned correctly first of all.

Alec

[/ QUOTE ]

Alec,

Sorry, don’t quite follow. If you follow the factory manual for installing the distributor, it can only go in one way. If you don’t follow the manual, you can put it in anyway you want. The spark plug wires will need to be changed on the cap.

Bill

 

[Bruno_69z28]

Adrio,

Alec is right. Some high duration cams will give you very low compression. They build up compression with higher RPM's.

Bill

 

[piman]

Hello Bill,

what I am talking about is the drive shaft from the cam to the distributor. After re-fitting a cam, this shaft is inserted and meshes with the cam. Certainly if it is installed with no regard to dog orientation then you will need to swap wires, but in the context of this post regarding the cam being 180 degrees off, if the shaft is installed, in time, with the engine at no 1 firing the distributor will be correct and no wires need to be swapped.

Alec