Setting Belt Tension

I put my new belt on last night along with a new tensioner and idler bearing. While the WSM advocates the use of a Staeger deflection guage to set proper belt tension most f-chatters seem to agree that the tensioner will set proper tension by default. This seems to be reasonable, however, you will get a big variance in tension depending on whether you load the belt (by slightly turning the crank) CW or CCW before tightening the tensioner bolt. For instance, turning the crank slightly CW will create a lot of slack on the tensioner side - tightening the tensioner in this state will yield a much greater belt tension. Maybe the Staeger is not a bad idea if in doubt. Just a thought for the novice DIY'er.

 

Yes, Rifledriver was answering a post I made in the 308 section and was discussing the whole issue of proper belt tension. Although, the F355 use hydraulic tensioners and the 308 spring-loaded, I'd be curious to see what the answer to this question is.

 

A Staeger is the go, but during my apprenticeship, my tradesman (boss) told me he hadnt used one since the introduction of the hydraulic tensioner.

So I have never used one, but I grasp the basic concept of them.

Thats what I do, everytime.

 

This is what I did as well Pap - but man is there a lot of tension on the belt compared to the old one! I guess after it gets run in it will stretch. I hate guessing however...

 

Cam belts stretch, only a LITTLE bit, but they do.

And who knows how the last belt was fitted last time? Perhaps they didnt put the tension on it like you did, which is why it is a lot different?

It will be fine mate, trust me.

 

348 doesn't use a hydraulic tensioner like the 355.

Best to follow the recommended factory proceedure at TDC compression stroke cyl.#1, measurement taken with a Staeger gage at both lower belt planes, between exhaust cam pulley and idler pulley. Add the 2 values together to get your number. Increase or decrease tension to get the prescribed value. Lock it down and Bob's your uncle...


Did you check and adjust your cam phase timing????

 

That is true.

I was really directing that post towards the 'phasing' out of the Staeger gauge when hydraulic tensioners came in.

 

PAP,

No worries, with the hydraulic tensioner the focus is on setting the geometry and dead stop clearence, the tensioner itself applies dynamic tension to the belt continuously.

Just want to be sure observers know this is not the case with the 348 as it relies on a fixed (staic) tensioner, so a proper tension proceedure must be followed.

 

Thanks, Adam. This is where I was having a "disconnect" between the 348 and F355.

BTW, are you going to become a Ferrari Tech in "paradise"? LOL

 

I thought I was going to get away without anyone asking.... No. Just lined up the marks. I bought the degree wheel and dial indicator/stand and wimped out in the end. I didn't do it this time around for 3 reasons:

1. The car is running really well - no symptoms related to timing problems
2. My engine is really dry with virtually no leaking so I decided not to even crack the valve covers
3. Not confident enough with my current skill level to do this extra step

I think I agree with your school of thought that says cam phase timing is the only true method to test for a properly timed engine and I WILL do it eventually.

 

And it is the only way to insure you wont have check engine lights, slow down lights and destroyed cats.

I am sorry to say but you are a poster child for why we very rarely give thumbs up on PPI's to owner serviced cars.