Cam Timing

[newguy]

Alright Boys and girls

Gunna pick your brains.

Have just put the head back on, have not torqued her down yet though, the the number piston at top dead center, and the valves are closed on number one ready to fire.

Thing is at 0 Degrees on the front pulley, lined up with the timing mark on the timing cover
As shown here


The cam marks are like this. it is not a tooth out, but just behind the marks.


Im guessing that this should all line up 100%
Now my head has had a skim maybe two, im not 100% sure.
How much difference is this going to make if it is not spot on?
We thought we could slot the timing sprocket so we can adjust the cam etc?

And with the came lined up 100%
Shown here


The Front pully is 16Degrees or so before top dead centre.


What should i do?

Me and my dad thought it should be fine and i should just carry on putting her together.

I guess most of you have come across this before.


Please shead your thoughts as i would like to have the motor and box in the car at the end of this week!!!

Cheers Stew

[Keith CANSDALE]

You need a Vernier camshaft sprocket (= adjustable)

[newguy]

i know i could get one of those.
but how insanely important is it to have bang on?
How big of a difference is it going to make?
i could just mod mine to make it adjustable.

[iandollysprint]

i know i could get one of those.
but how insanely important is it to have bang on?
How big of a difference is it going to make?
i could just mod mine to make it adjustable.

I would get a vernier. Sprintspares one is excellent. You could mod your own by elongating the holes, I did this on a BMW M635csi and it worked fine, in fact thats what the BMW works teams did on the old M3's. It cost me 90 quid to get both done (twin cam on the BM).

With you being 16 degrees out on the crankshaft I would investigate further though as a head skim is unlikely to create such an error. Perhaps the chain is just one tooth out on the cam shaft sprocket? I know on the BM you only had to be 2 teeth out on the camshaft sprocket and valves would hit pistons when rotated It will depend on what cam you have in the sprint as to wether or not this will happen. It's just that 16 degrees out seems a lot to me. Did you rotate the crankshaft backwards to get the 16degrees because this would have created slack on the the straight chain length from the camshaft sprocket to the cranksprocket which may have slewed your results.

Good luck with it

Ian

[newguy]

yes i did go backwards on the crankshaft.
I will check that the valves do not hit, i do not think that they should.
I will go in the right direction tomorrow and check it.
If it turns out to be a problem i can fix it while it is in the car.

[iandollysprint]

yes i did go backwards on the crankshaft.
I will check that the valves do not hit, i do not think that they should.
I will go in the right direction tomorrow and check it.
If it turns out to be a problem i can fix it while it is in the car.

Remove your spark plugs when you rotate it so the only tension you feel when rotating it is the valves when they hit the pistons

From your photos (first couple) I would say you were OK, it was just the 16 degrees out that worried me.
Also when you release the cam sprocket from the cam you may inadvertently slacken off the cahin that goes to the tensioner. If you do this then the tensioner will come out to try and take the tension up and then when you go to refit the camshaft sprocket it will not fit. Be careful. You then have to remove the front cover to set eveything up again. Don't ask me how I know.

[newguy]

how do you know of this?

haha

[Mad Mart]

The straight run of timing chain on the right (looking from the front) should be taught when timing. Forget about the slack on the left hand side, this is all taken up with the curved chain guide & the tensioner once you've got the timing marks lined up. I reckon if you were to get the timing marks spot on on the crank pulley then move the chain one tooth, it will line up correctly.

[sprint95m]

I agree with Mart.

[Jon Tilson]

So do I. You are a tooth out mate...

The procedure is allign cam, align crank....fit sprockets. straighten chain to tight on non tensioner side...do it all up and release tensioner. Turn a few times and check alignment. It should be spot on. If its out then you are a tooth out.

Also align the jack shaft on marks or ignition timing will be a bitch...

Jonners

[newguy]

Thank you for your response, we thought it was to far out to be a tooth out.
What i will do is while the chain is on get the cam timing marks lined up, release the tension undo the chain, get the crank pulley in the right place and re apply the chain.
What does the jackshaft pully line up with.

Thanks for your response


I think i may have not had the timing marks on the head lined up when i put the head on.

[sprint95m]

In another thread somewhere, did you mention using a Haynes manual?

If so, what head tightening sequence does it show?
If my memory is correct, Haynes showed a different tightening sequence to the one used by BL.
I would use the BL version because I have successfully used it myself.


Jackshaft pulley position does not matter at the stage you are currently at, because you fit the distributor last (so you can then determine which is No.1 terminal and fit the leads accordingly).

[djw113uk]

Just in case.....
We had one that didnt line up... turned out that the "damper" in the front pulley was shot. That allowed the outer "pulley" to turn whilst the centre stayed still... or vice-verse. We carried on, (confused) with TDC correct on the head, and pistons 1 and 4 at the top, ignoring the crank pulley. Engine ran fine.
...... We eventually worked it all out when it came even looser and knawed all the timing pointers away!

[newguy]

Thanks for all of your inputs, i will correct the timing mark on the cam timing, then remove the timing chain, set the crank pulley to 0 degrees, and re apply the chain.

Will report back tonight.

[Jon Tilson]

There is an alignment mark on the jackshaft pulley. Oberving it will help ignition timing later but as Ian says it is adjustable later as the dizzy can go in on numerous teeth.

Jonners