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Correct tension of a pinto cambelt?
ditchlewis - 5/3/17 at 11:04 PM

Took the plunge this weekend and changed the cambelt on the old mk. I have rotated the engine by hand four complete cycles and the marks all line up and no slipping.

I'm needing to fix the alternator bracket but other than that I'm good to go.... Except I'm very apprehensive .....

How do you check the correct tension on the belt? I don't want the engine to self destruct as I have sold these to my son.

Regard
Ditch

benchmark51 - 5/3/17 at 11:18 PM

I've done quite a few over the years and usually check that I can pinch the belt between finger and thumb and turn it about 90 degrees. Normally this is a non interference engine and doesn't do damage if the belt breaks.

cliftyhanger - 6/3/17 at 07:48 AM

Same advice here.

mcerd1 - 6/3/17 at 09:35 AM

quote:
Originally posted by benchmark51
I've done quite a few over the years and usually check that I can pinch the belt between finger and thumb and turn it about 90 degrees. Normally this is a non interference engine and doesn't do damage if the belt breaks.


there is a proper tension gauge you can get for these, but most folk still just use 90° twist on the longest part of the belt


btw 2.0 pinto's are normally non-interference, but if its had a lumpy cam, the head skimmed or any other upgrades like that then it will be an interference engine now...

ditchlewis - 6/3/17 at 09:41 AM

That's great. ... it is a 2.1 pinto with flat top pistons and high lift cam so not sure if it is still a non interference engine hence the trepidation.

It did slip a couple of times and I had to reset everything an add more tension on the tensioner. The only way more tension could be added to the belt is if I stretched it.

It is just that on the belt on the side of the timing drive to the cam can be pushed in a bit. There is no way to get another tooth on the belt round without as I said stretching the belt.

Will try the twist test tonight.

Thanks lads.
Ditch

mcerd1 - 6/3/17 at 09:45 AM

quote:
Originally posted by ditchlewis
it is a 2.1 pinto with flat top pistons and high lift cam so not sure if it is still a non interference engine hence the trepidation.


it will 100% defiantly be an interference engine I'm afraid...

nick205 - 6/3/17 at 10:05 AM

I followed the Haynes manual procedure when I rebuilt my Pinto (with new cam belt). The engine ran fine thereafter. If you don't have a Haynes manual I'd suggest getting one - lots of helpful info in them.

ditchlewis - 6/3/17 at 12:53 PM

Yep got a Haynes manual and followed it.

I looked at the tension meter for the pinto but at over 100 quid for a single use...... a bit rich for me.



regards

Ditch

benchmark51 - 6/3/17 at 12:58 PM

We had a gauge at a Ford dealer workshop and I don't think anyone used it more than once!

daviep - 6/3/17 at 03:08 PM

quote:
Originally posted by ditchlewis

It did slip a couple of times and I had to reset everything an add more tension on the tensioner. The only way more tension could be added to the belt is if I stretched it.

It is just that on the belt on the side of the timing drive to the cam can be pushed in a bit. There is no way to get another tooth on the belt round without as I said stretching the belt.

Will try the twist test tonight.

Thanks lads.
Ditch


This statement worries me that something fundamental is wrong, for a belt to slip it must be hanging off like a piece of string.

It sounds as if your cam timing is possibly 1 tooth out. To check is simple, when you turn the engine over using a spanner on the crank when you stop at the TDC mark (make sure you stop while turning clockwise don't turn back if you go past TDC) is the camshaft 100% lined up? If yes timing is OK, if no timing is wrong.

There should be no play/slack in the belt between the crank and cam on the un-tensioned side. To tension the belt is as simple as slacken the tensioner locking bolt, using a lever/screwdriver pry the tensioner tight and then tighten the locking bolt while holding the tension, if the crank or cam move noticebly when you lever the tensioner the timing belt has been fitted wrong with excess slack between the crank and cam on the un-tensioned side. Once the belt is tensioned turn the engine over two turns and stop with the crank at the TDC mark (make sure you stop while turning clockwise don't turn back if you go past TDC). If the cam mark is not lined up at this point the timing is wrong and the belt needs to be slackend and the cam turned to the correct position.

Sorry it's so long winded, it's simple in my head but hard to describe in words.

Regards
Davie

Regards
Davie

ditchlewis - 6/3/17 at 05:52 PM

[pg]1169https://www.locostbuilders.co.uk/gallery/2cam.jpg94[/pg]


the belt cannot stretch any more and all the timing marks line up. as in the Haynes manual I turned the engine over by hand four complete cycles and on each cycle the marks lined up. there is no slack in the belt to allow the belt to slip.

the direction of play is shown in blue and just seems a bit much but this is the first belt I have changed.

ditch
[Edited on 6/3/17 by ditchlewis]

[Edited on 6/3/17 by ditchlewis]

[Edited on 6/3/17 by ditchlewis]

rusty nuts - 6/3/17 at 06:53 PM

As others have already turn the belt through 90 degrees at the cEnter of the longest run . What I would be a little concerned about is the fact you have a high lift cam and using the standard timing marks, its very unlikely to have the optimum timing . Did you line up all of the timing marks before removing the old belt?

ditchlewis - 6/3/17 at 07:14 PM

The cam as a vErnie hence no tdc marking. I marked points on the block and cam. All the points I marked lined up perfectly when I finished. .

Ditch

jollygreengiant - 6/3/17 at 07:34 PM

Getting the correct tension on a pinto always used to be simple. They originally had a blooming great spring that the long bolt used to go through with one arm resting against another long bolt and the other arm resting against a short pin. you just couldn't go wrong.

ditchlewis - 6/3/17 at 07:48 PM

Success just done the 90 degree test. It would only turn 85 degrees so I have enough tension in the belt. I will do one last check on timing marks and I'm ready to go.

Thanks lads
Ditch

mcerd1 - 6/3/17 at 08:04 PM

quote:
Originally posted by rusty nuts
What I would be a little concerned about is the fact you have a high lift cam and using the standard timing marks, its very unlikely to have the optimum timing


What he said, the whole point of the vernier pulley is so that you can deal with the inaccuracies' of the std timing marks

Terrible video quality but this is the right way to do it:
https://m.youtube.com/watch?v=yJXKzaq_5GU

ditchlewis - 6/3/17 at 08:15 PM

The vernier has no tdc marking gs. So I made my own to make sure everything lined up correctly. All markings are still spot on.

Ditch

mcerd1 - 7/3/17 at 08:56 AM

quote:
Originally posted by ditchlewis
The vernier has no tdc marking gs. So I made my own to make sure everything lined up correctly. All markings are still spot on.


I'm sure its pretty close, but less than 0.5° on the cam position can make a difference to how it performs

mind you the only way to find the perfect timing for your particular engine build is to try several different ones on the dyno - starting with the recommended timing and then maybe upto ±1 or 2° either side to that in small steps of 0.5° or less....

ditchlewis - 7/3/17 at 09:10 AM

I always thought about a rolling road session and it was on my to do list. Now the car is my son's I will recommend he gets it seto up properly.

On to the new project

Ditch.