Cambelt issues

[Dynion Araf Uchaf]

I am having a bit of a 'mare trying to fit a cambelt with the correct tension on my recently rebuilt 106 GTI engine.

In theory it is simple to do, I can lock the cams and pin the crank at TDC easily enough.

I can also fit the belt so that it is tight ( but with a tiny amount of flex) all the way around and particularly between the twin cams. I've tried various methods, from leaving the pulley bolts loose so that the pulleys can move a little but the cam remains locked, to fitting with every thing tight, but the end result is the same.

I then tension it up by adjusting the tensioner to suit.

However when I hand crank the engine to rotate it, it belt gets 'loose' between the cams (around 1 turn of the crank from tdc), before then going tight again. Now I appreciate there may be a little movement, but what i am seeing is more than a little. I'd be worried that the belt would slip as it currently stands.

Can some one give me some pointers as to what I am doing wrong, I've been fiddling with it for hours!

[Krikkit]

Have you followed the "proper" method per the Haynes to equalise the tension across the belt? First time I did it, it seemed counter-intuitive, but worked fine every time.

[Dynion Araf Uchaf]

Yes, many times.

[steveo3002]

never worked on that car , but try turning by hand several more times see if it sorts itself out

[Dynion Araf Uchaf]

I have hand cranked it several times.No improvement. I did notice however that it goes slack at BDC. I know it will a little anyway, but the amount was ridiculous, So I decided to tighten the belt in that location as well. Which has sorted the problem out ( 95%) or at least I wouldn't be worried about it. The cams are still aligned when the engine is at TDC. However I am not willing to start the engine until I can work out if this is actually ok, or I can do the Haynes method properly.

[Krikkit]

What's new in the engine? I assume when the belt was going slack it was through the idler side on its way up to the inlet cam? Are you running standard timing gear?

I'd fetch it to mid-stroke to get the pistons clear, cambelt off, rotate the cams and see how they feel in case something's binding up.

[Dynion Araf Uchaf]

The engine is standard spec however new valves, stem seals, skimmed head and de coked bottom end also skimmed, honed bored oversized piston (0.5mm) honed cranked , new bearings , new rings. So essentially a 0 mile std 106 gti engine.

By studying and following the Haynes manual I have got the belt tight at tdc with a bit of slop at bdc. With belt off cams and crank turn smoothly.

It’ll run, belt looks a little sloppy when wizzing round but better than it was, but it won’t idle.

I am now thinking that the new valves and 3 angle valve seats have fractionally changed the cam timing.

I think I still have some work to do?

Edited by Dynion Araf Uchaf on Sunday 18th June 13:32

[Krikkit]

Hmmm, odd. When you built it up did you check the valve clearances?

By the proper method it doesn't make sense you'd end up with slack in points of the belt unless something is hanging up, the tension should be fully equalised after the first set of turning it over

[Dynion Araf Uchaf]

I didn’t build the head and block only assembled them and added the alternator etc.

The company thst did the head did say that the original valves were needing a fair bit of work to form a seal again.

I think I may take it to a rally prep company near me for final checks.

[rigga]

Dynion Araf Uchaf said:

The engine is standard spec however new valves, stems seals, skimmed head and de cokes, bottom end also skimmed

I am now thinking that the new valves and 3 angle valve seats have fractionally changed the cam timing.

No skimming the head and block has changed the cam timing.

[Dynion Araf Uchaf]

Does that mean the cam has to come out or is there some other adjustment I can do. I am aware that the cams and crank can be pinned, and have done that but now you’re saying that may not be the correct timing. If so how to adjust?

[gazza285]

rigga said:

No skimming the head and block has changed the cam timing.

These use adjustable cam pulleys? With the cams and crank locked, the belt is tensioned, then the cam pulleys are tightened, so the skimming and decking should not affect the timing. That is my understanding.

[Dynion Araf Uchaf]

gazza285 said:

These use adjustable cam pulleys? With the cams and crank locked, the belt is tensioned, then the cam pulleys are tightened, so the skimming and decking should not affect the timing. That is my understanding.

There is some adjustment. And this is the process I have been following.

[louiechevy]

If you've still got the original belt and tensioner that came off I would be tempted to try them back on and see if the tension is OK with them, if it isn't something has changed if it is maybe try another new timing kit.

[Dynion Araf Uchaf]

It is the original belt and tensioner. Both were new last year and fitted on the engine before the rebuild. I probably need to share a video of the ‘movement’ to see whether I am over reacting

[louiechevy]

Well that's my idea up in smoke!

[Dynion Araf Uchaf]

Anyway after much dicking about I think I have finally sorted it. Unfortunately just not 100% sure how I did.

The belt is now tight in all the usual places both Tdc and bdc, and there is no slop or pinging up of the belt between the cams. Ran it up , well started it with the pump relays removed and that showed the the belt wasn’t bouncing up and down, well a tiny bit but I think they all do a little. Then fired it up took it to 7500rpm and only one piston came through the block. So am calling that a win.

Actually it seems to run as Peugeot intended so now I think I can get it off the axle stands and take it to a track day.

[Krikkit]

Great stuff, shame you don't know what's fixed it!

They definitely have a bit of idle flap as standard, long as it runs up to the limiter cleanly it's all good