Cam Install.

[jimes]

Hello again gents,

I'm currently in the midst of a rebuild with the aim of making it to a show on the 26th of this month (50 years of the spitty!)

 

I have a new cam to go into my mk3, and i've never done this before.

 

It is a "High Torque" cam from Jigsaw (made by Newman cams)

 

the info I have on it is:

 

duration= 270

 

lift= 435

 

and "install figure" =108-110 after TDC.

 

I've been watching videos of americans putting cams into V8 engines, but they all seem to have much more info than I do , like numbers on where the valves start opening and when they close.

 

I'm a bit lost as to where to start.

If i simply line up the cam the same as the original timing marks, is that how it's supposed to work?, straight in like that?

What does the install figure actually mean?

 

Any answers, especially pointing out anything obvious that my newbie brain hasn't grasped, will be much appreciated.

cheers,

 

-Jim

[JohnD]

It's so long since I used the magic "install" number that I may get it wrong. Basicly, you set the cam to full lift on inlet valve, No.1 cylinder, and the crank to the magic number of degrees before TDC. Even with a dial gauge, find full lift and TDC can be tricky, find TDC with a 'dead-stop' in the bore (TDC is in the middle of the two stop positions) and full lift in the middle of the two positions where lift seems to stop. You need a degreeing wheel for both tests. Then, fit the sprocket and chain.

 

Check, or fit, by using the 'equal lift on overlap' method. Because a six is three two cylinder engines with each pair firing on the alternate stroke (and a 4 is two pairs) No. 6 (or No.4) cylinder will be between four stroke cycles when No.1 is on the firing stroke. The inlet and exhaust valves will be opening and closing respectively, and at the same rate. So at TDC, if the cam is set correctly, the two valves should be at the same height. A job for a dial gauge or a good Vernier gauge, and if they are 'equal lift' then the cam is correctly set.

 

If you have the OE cam sprocket, use the method in the Workshop manual, lingi up the marks on cam and crank sprockets, but I have to ask - you have gone to the expence of a new camshaft. Why rely on an old, worn cam sproket? Look at it closely - I'll bet the teeth are asymmetrical, becasue they are worn. This will cause the timing to vary more than it should.

 

John

 

PS Dead stop in use

Edited May 5, 2012 by JohnD

[spitNL]

Hi Jim,

 

Is there a grind number on your camshaft?

On Newman's site I looked for a cam with your specs, but the only one with 0.435" lift is the TRIS/300/435 PH4.

This cam is described as a race camshaft with 300deg duration and a powerband of 4000-8000rpm.

You can check the other specs over here:

http://www.newman-cams.com/pdf/triumph.pdf

To me these specs don't say High torque?

If there is a grind number on it, maybe Newman can tell you more.

 

As for timing the cam up, if you're doing it for the first time it's very easy to make a mistake.

So I'd suggest the following procedure.

1. Check TDC using the dead stop method John's described and mark both stop positions. (rotate the engine forward and back)

TDC is exactly in between the 2 marks.

If you've got the flywheel on you can mark it on this.

2. Fit the cam using the original timing marks.

This will get your cam reasonably close.

3. Fit the degree wheel, rotate the engine to TDC and zero the degree wheel.

4. Now using the degree wheel check at what position full inlet lift occurs.

Note: only rotate the engine in it's normal direction, otherwise timing chain slack will throw off you readings.

If you get a very odd number, check again, it should be very close to 110degrees.

(Some degree wheels can be confusing in being divided into four 90degree segments, two 180degree segments, or counting down in engine rotation direction)

You want full lift to occur between 108and110degrees.

If you've double checked and sure it's off, advance or retard the cam.

Course adjustment can be done by taking the chain off, turning the cam one tooth and putting the chain back on.

Fine adjustment is possible by turning the sprocket over.

 

One last remark; If it is indeed a PH4 and you want to keep it, I'd advise advancing the cam to 104-106.

 

@JohnD

TBH I don't like the 'equal lift on overlap' method as that only works when you install the cam straight up.

If you advance the cam the normal 4 degrees that method won't work.

Ignoring other factors such as asymmetrical ramps and lash if you're measuring at the valve.

 

 

Frederick

[JohnD]

No argument, Fred!

But Triumphs don't use that fancy asmmetyrical stuff, excopet for a few, a very few, exotic race cams that have been described.

And ELOE does allow you to fit, and time the cam if you don't have a magic number, the sprocket lacks marks etc.

AND, ELOE is a surrogate marker for full lift on No.1 Inlet, so you can advance it from there if you want.

IMHO, it's so much more flexible that the rigid, 'magic number' method.

 

John

Edited May 5, 2012 by JohnD

[jimes]

Thanks heaps guys,

I'm starting to understand this a lot better.

 

And John I do indeed have a new double sprocket and chain with the fancy verneer adjustable-ness.

 

I'll use your stop method for TDC.

There seems to be a bit of a discrepancy between what my book depicts as where the timing marks should be and what my original cam was set at when i pulled it out. Also the punch marks on my cam sprocket are actually the reverse of my workshop manual= a dot on the outer edge and a dot to the RIGHT of the centre of the sproket, as opposed to the LEFT which my book shows.???

 

When I had my webers tuned last year I got a call from the guy (sounding a bit confused) asking if my cam had been moved, so there is something different going on there I think.

 

Frederick the Cam is a special order for Jigsaw, the box reads HIGH TORQUE CAM, TRIS/HT6/NEW-CAM for which I couldn't seem to find the exsistence on Newman's website.

 

After I posted I kept googling and came across some very helpful info for when you are like me and don't have a Dial gauge or degree wheel, thanks to ISKY cams web sight.

 

CHECKING VALVE OVERLAP WITHOUT DEGREE WHEEL OR DIAL INDICATOR

When installing a camshaft, or when an occasion arises where it is necessary to make a check on valve timing and no appropriate instruments are available, the recommended Isky procedure is as follows:

1. Insert the camshaft and mesh the timing gears on the stock marks. Do not as yet install the timing gear cover.
   
2. Using a long wrench or lever, turn the engine over in the normal running direction. Use enough leverage to get an even, steady movement instead of a jerky motion. Rotate until the intake and exhaust valves of No. 1 cylinder are in the overlap position (both valves opened slightly). Stop exactly on T.D.C., which is marked on the harmonic damper.
   
3. Now loosen and back off the rocker arm adjusting screws until the intake and exhaust valves are just barely closed. Lock the tappet adjustment screws so that the intake and exhaust valves are at exactly zero clearance.
   
4. Now turn the engine over exactly one revolution of the crankshaft to T.D.C. on the harmonic damper. You are now at T.D.C. on the compression or firing stroke.
   
5. Take notice! Now there is a large space between the rockers and valve stem tips. This space indicates the actual amount the valves were open at T.D.C. of the overlap period (less valve lash, of course).
   
6. We will measure this gap space by probing with common feeler gauges of various thicknesses combined until we determine the gap space. After computing the gap, record the figures for both intake and exhaust in your notebook. If the amount of gap on intake and exhaust is exactly the same, you have a perfect split overlap.
   

 

My brother is coming today to help me out. Hopefully by the end of the day I'll have a result!

cheers,

Jim

[GT6MK3]

Got a printer?

http://sideways-technologies.co.uk/forums/index.php/topic/978-printable-degree-wheel-for-ecumegajolt-etc/page__view__findpost__p__13197

 

[jimes]

AH!!!

 

BRILLIANT!

 

THANKS!!!

[jimes]

Ok,

I think everything is lined up nicely!

Now I'm up to thinking about the distributor.

 

Does anyone have any suggestions of where to start?

my workshop book says 6 deg BTDC,

but, everything is different now.

 

thoughts? suggestions? conspiracy theories?

-Jim

 

 

pic related

[jimes]

oops