4 pot cam shaft/valve timing

[RogerH]

Hi Folks,

I'm trying to set the valve timing on my 4A engine.

I have a new camshaft, new cam sprocket and new crank sproket.

 

I can find TDC (piston stop part way down the bore). I have a timing degree wheel.

 

Initially I used the original cam and crank sprockets to set the cam in the correct place (they have the original factory marks)

With the cam positioned, the sprocket is removed and the new sprocket fitted.

 

However this is easier said than done - things move.

 

Also the WSM shows the valves opening and closing at 17 BTDC and 57 ABDC.

This is all well and good but the valves are ramped up to being fully open and the beginning of the ramp (cam) is vague.

It isn;t 1 or 2 degrees about 17/57 but could be anything.

 

Is there a more snappy way of doing this.

I haven't got the head on at present so the other method of balancing 7/8 are awkward.

 

Any advice welcome

 

Roger

[Lebro]

Don sent this a while ago in your TR4 engine rebuild post

 

Roger, if you haven't seen it yet, here's Mark Macy's writeup on "degreeing a cam".

http://www.macysgara.../cam_degree.htm

 

Basicaly use a dial gauge to find exact piston TDC, then again on a push rod to find cam TDC. Then use crank mounted angle gauge to set the two correctly.

 

Bob.

[TriumphV8]

It is not recommended to measure the timing at beginning and end of lobe.

Also at the top of the lobe is not good place to measure.

Lots of crank degrees perform poor lift of valves there!

 

With that two ways of keying in are possible.

 

First the easy way if inlet and exhaust are symmetrial:

At TDC both valves must be open same height

 

The second way:

Advertised duration is 17 + 57 + 180 degrees = 254

Spread is 254/2 - 17 = 110 degrees

 

110 degrees is the max lift point of cam.

As we can not measure that precise we measure

at a position where the valve opens or closes quickly.

 

Lets say we take 50degrees (110-60) after TDC and 170 degrees (110 + 60)

and at those points the lift must be the same.

If not the came must be repositioned and measurement must be done again.

 

Do not forget to clamp something at the chain at the spanner side and

approach the measurement points from real crank rotation.

[RogerH]

Hi Bob,

I did read Don's post and have tried it this morning.

The problem is as Andreas has stated - trying to see where the cam starts and stops is very very vague.

 

However possibly using Macy's tappets and Andreas's method I think I may be able to sort things out.

 

The annoying things is I know I have done it right but can't demonstrate it.

 

Roger

[Rob Salisbury]

Hi Roger, Dave Vizzard, in his book Tuning Triumphs over 1300cc gives a very good description of how to find the point at which the clearance ramp finishes and the valve opening point begins, you need a dial gauge and a bit of fiddling but I've used his method many times and it , to me, seems easier and more logical than using the max lift method. Just google for the book it's on the interwhatsit.

Cheers Rob

[john.r.davies]

Roger,

I think that a TR4 will have a "Symmetrical" cam shaft and so will be easily timed by the Equal Lift On Overlap method.

On which, as it happens, I have just submitted an article to Wayne, for TRaction Technical pages.

 

In one sentence, set TDC on No.1 bore, and the valves on No.4 to equal lift, the exhaust closing and the intake opening, as the cylinder ends on four stroke cycle and starts the next.

An added bonus is that this allows you to check the timing with or without the head on.

 

I'll gladly send you a 'proof' of the article if you PM me your email address.

John

[Nigel Triumph]

Roger,

 

I recently faced the same problem when timing the cam while rebuilding my GT6 engine.

 

Measuring TDC by putting a dial gauge on top of a piston, rotating the crank and watching when the dial gauge stops turning isn't very accurate. At the top of the stroke, the crank turns several degrees with very little discernible movement of the piston.

 

A better method is to set No.1 piston at the top of the bore and fit a 360deg protractor to the crank nose and with the piston 'apparently' at TDC set the protractor pointer to zero. Next zero a dial gauge on the piston crown.Rotate the crank anticlockwise to get one full rotation of the dial gauge and mark the protractor measurement. Now rotate the crank clockwise to take the dial gauge back to zero then on full gauge rotation further. Mark the protractor again. True TDC is at the midpoint.

 

Repeat the TDC check to ensure no errors.

 

I timed the cam by finding maximum lift on No.1 inlet lobe. Start by setting the timing roughly using the marks on the sprockets. With a cam follower and pushrod in place, set the dial gauge on top of the pushrod and turn the cam to get maximum lift (not accurate at this stage). Now repeat the backwards and forwards measurements with dial gauge and protractor as used to find true TDC. This will give you an accurate position of the maximum lift point. I had to do this several times before I could get the chain and sprocket ideally located.

 

Andreas is correct that measuring the point of maximum lift isn't accurate. The backwards and forwards method overcomes this inaccuracy.

 

Simply lining up the timing marks on the sprockets gave a setting that was half a tooth out, about 8 degrees. Using the dial gauge and protractor I got the timing accuracy better than one degree. The engine's now run in and going beautifully, so I reckon the time spent here was worthwhile!

 

There are photos of this in the latest issue of Practical Classics.

 

 

Niel

[Motorsport Mickey]

^ +1

 

Old school maybe but measure No 1 inlet on camshaft until the DTI stops lifting, make note of the marks on the degree cam, carry on turning the crank until the DTI starts to drop make a note of the marks showing on the degree cam (normally within 6-8 degrees). Halve the difference between when the camshaft stopped lifting to when it started dropping and that's your max lift, does it really need to be any more complex ?

 

Mick Richards

[RogerH]

Hi Folks,

getting TDC and #1 is not a problem (I'm quite good at it now)

I have established that the old cam and the new cam are identical (Moss standard cam).

Using the old cam sprocket I have established the correct cam position.

And being very careful found the closest fixing point for the new cam.

 

So I'm happy I have a good basic setting.

 

I shall now have a play and establish the high point for #1 inlet and see what degrees it reads.

 

When I get the head on I will try the other (balanced lobe) method as above. It is also described by ST in the WSM.

 

Slowly getting there.

 

Many thanks for your input - very informative.

 

Roger

[McMuttley]

Hi Roger, Dave Vizzard, in his book Tuning Triumphs over 1300cc gives a very good description of how to find the point at which the clearance ramp finishes and the valve opening point begins, you need a dial gauge and a bit of fiddling but I've used his method many times and it , to me, seems easier and more logical than using the max lift method. Just google for the book it's on the interwhatsit.

Cheers Rob

Roger, said boook is collecting dust in my dtudy if you would like it?

[Don H.]

Roger, said boook is collecting dust in my dtudy if you would like it?

 

Tuning Standard Triumphs over 1300cc by David Vizard, Speed and Sports Publications, February 1970 is online as a b&w scan, too. No idea how long it will be there, but for now...

http://auskellian.com/paul/links_files/David%20Vizard-Tuning%20Standard%20Triumph.pdf

[Tom Fremont]

Hi Roger,

 

I dial in ~ 3 degrees of crankshaft advance on my 6-pot engine cams to compensate for chain slack to come, circa 6 degrees when they get well worn. I have always been able to get it from the sprocket bolt fit clearance, and check the final result rotating the engine in its natural direction. To get the maximum grip on the sprocket I degrease the mating surfaces, oil the bolts and torque to the maximum given value.

 

Cheers,

Tom

[RogerH]

Hi Don,

I found it from the above link but finding the info from within the PDF is a task worthy of Sherlock himself.

 

Roger

[Motorsport Mickey]

Hi Don,

I found it from the above link but finding the info from within the PDF is a task worthy of Sherlock himself.

 

Roger

Hi Roger,

 

In case you're still having problems, Page 98 through to page 102. Mick Richards

Edited April 25, 2016 by Motorsport Mickey

[Guest ntc]

Roger

 

You can change the cam timing to suit what you want, remember what i posed before it works fine with std

[RogerH]

Hi Folks,

Thanks for all your info above.

This morning I set the cam up using the TR4 WSM. Get 7&8 lobes balanced with crank at TDC.

This appeared to go well.

There is a small punch hole on the end of the cam apprx similar place to ST cam.

This ended up apprx same place as the original cam.

 

So with your advice and the words in the book I think I have surrounded the cam timing issue. I can now lock the sprocket in place.

 

I can now get on with finishing the engine build.

 

What I noticed the other day - when I temporarily fitted the head the CofG of the engine is serious;y top heavy on the engine stand. So I will need to remove the head to complete the build and refit it as the last thing.

 

Just as a small complication the woodruff key slots ion the front of the crank were machined 180 degrees out (this will be sorted for any future cranks).

I had to scratch my head for a moment to ensure that simply transfering the timing marks across the crank sprocket would be OK and it is.

On the original ST sprocket the timing mark coincides with a gear tooth. Transferring it puts it into a hollow between the teeth.

 

Roger

Edited April 27, 2016 by RogerH

[Rob Salisbury]

Hi Roger, just out of interest were Pheonix Crankshafts approached for another run of 4 pot cranks, they made a batch for Moss back sometime in the last century, I've got one in my 4A and it fitted without any of the niggles you seem to be having. Took it along to be balanced along with all my other reciprocating bits and was reliably informed that it was a forged item and needed no further balancing, just the flywheel and clutch needed light trimming ( rods were done eons ago by SAH).

Cheers Rob

[RogerH]

Hi Rob,

Phoenix do still make cranks for the TR4 etc. They are not forged but machined from the solid (something in the region of £1800-2000)

Not sure what Moss did a long time ago but forging would be a very expensive exercise.

We are trying to get to 30% of that cost.

 

I would have thought a cheaper crank than a solid billet would be a cast crank.

 

I think my new crank could have been balanced better than was actually done.

Rather than hacking lumps out of it they could have machined the webs a lot neater than they did.

Roger

[Rob Salisbury]

Wow, I see the problem cost wise!! ...... They were around the £300 mark and I bought mine during a vat free period, Moss were in Manor Rd, Richmond at the time so it was around the late 80's early 90's.

Cheers, Rob

[james christie]

Just to upset y'all. I think I paid the late Bob 'the prophet' Soden £25 for a second hand one reground to 10 thou off the journals and bearings.

But it was about 1981!! ☺️

 

James

[RogerH]

...you were robbed.....

 

Roger

[PeteT]

Sorry to be a retard Roger but doesn't all your good work fall to bits the second you put the timing cover back on when the tensioner pulls the crank and cam gears together? Must have missed something.

 

Regards, Pete

[TriumphV8]

Must have missed something.

 

 

Yes, its the last chapter of my post Nr 3.

[RogerH]

Hi Pete,

I made sure, as best as possible, that the chain on the tension side of the gears was tight.

Hopefully the tensioner will simply hold the chain in place and do no more.

 

Roger

[RogerH]

Hi Folks,

a little twist to the story.

I was away for the week-end on the Welsh Week-end bash (it was excellent) but I had a little niggle going on in the back of my brain.

Today I decided before fitting the engine/GB to re-check the valve timing. It was 90 degrees out !!!!

 

So back to square one. The cam has a timing of 17-57-57-17.

Initially I tried the WSM method for an existing cam and sprocket aligning the dots ect. This didn't seem to work too well.

A number of methods were suggested by the forum but I used the WSM method for new cam and sprocket - balance #7&8 cam lobes etc.

I thought I had done this very well - but alas no.

 

Today I had a thought about the very hairy fairy way that the lobes are centered and realised that there is a base position that should be repeatable.

The inlet starts to open at 17'BTDC.

So I set the crank to 17'BTDC and then rotated the cam to get the lobe up against the follower/valve spring etc. This is a very definite position.

The sprockets were then attached for best position.

 

Guess where it all ended up - the punch mark on the cam aligned with the punch mark on the sprocket. - why it didn;t look right the other day I don't know.

Rotating the whole assembly the #1 valves followed the timing marks pretty well.

 

I'm happy now to button it up and install the engine/GB.

 

Roger