Using the heat wrench to install timing belts

April Fool's day isn't for 4 months...

 

...and, who said stiffer was better

 

My question pertains to the ponderables where almost no publically available information is available::

Lets assume the belt grows by a couple dozen thousandths in length when hot. The belt is now easier to twist (around pulles and other impediments) and easier to install. But your cam timing error grows unless you let the belts get completely back to ambient temperatures before setting valve timing.

Every new set of belts should be accompanied by a resetting of the cam timing. This is done with a dial indicator on a valve, and a degree wheel on the crank. If the belt is not at the correct length the numbers in the WSM are assuming, then you won't be hitting the numbers as close as you went to the effort to obtain.

First order read: clever instalation trick, don't hurry through the rest of dialing in the cam timing.

 

Why? I'll bet a whole lot of engineering went in to make that NOT happen.

 

How hot do the belts get when the engine is running?

 

Mitch, we can always count on you to overthink things!

I'd say that (1) the belt is very thin, with a lot of surface area, so it will cool to room temperature faster than you can degree the cams and, as pointed out by others, (2) the belt operates at an elevated temperature, so setting cam timing at room temperature is, in fact, an error, but (3) perhaps Ferrari sets the valve timing specs taking belt stretch into account! so... (1) the belt will cool down and be at room temperature.

I was going to go on about thermal expansion of the pulleys, and science out the how far the belt could allow the pulleys to move in cam degrees, and how much the head would expand, and tolerances in the drive (and, for some, the variable timing mechanisms) and we could carry on having all kinds of fun for days, but it's early.

I _DID_ google up a product brochure for a timing belt supplier and they claim the belts to be "thermally stable" but caution about thermal expansion and material selection of the drive system materials.

 

That's a great idea. I usually throw mine in the dryer on high for 5 minutes. Takes all the wrinkles out! (Seriously.....DON'T DO THAT)

I would expect the belts to have nearly zero expansion because once they are on and the engine is turned over a few times to make sure they are seated correctly and the tensioner has the correct tension, the locking bolt is tightened on the tensioner and there is no more tensioner movement that would place more or less tension on the belt. Ferrari doesn't require an adjustment after a certain number of miles, so I would expect nearly zero stretch in the belts.

 

LMAO

 

Mitch you don't have to worry about this if sand off the writing on the belts before you install them.

 

The valve timing error, from the foremost cylinder to the rear most cylinder, is greater than the "delta T" error from the belts.

The torsional resistance on the cam from the valve springs retards the rearmost cylinders at high rpm.

Don't forget to account for this, and have new cams ground with offset timing. Any serious motor builder will do this.

 

Uhhhh...

Was it Xaviera Hollander ?

 

LMAO!

 

ZING!!!

 

Believe it was Pfizer Labs (Viagra)

 

You cannot "engineer" a violation of basic physical laws...but then, logic would hold that:

1: being in the sun will not change the number of teeth in the belt. So they have to be in the correct position as per the teeth and the grooves no matter the temperature.

2: being run in the engine will get the belts at least as hot as sitting in the sun for a few minutes.

3: as stated above, the valve timing should be checked and set if needed.

 

LOL.

 

A timing belt is not going to change dimension very much, if at all with temperature. The kevlar cords within the rubber prevent this. The aluminum of the engine block and cylinder heads expand a much larger amount from room temperature to operating temperature than the belt does, causing the belt tension to get tighter.
Ducati uses the same type of timing belts on their motorcycle engines, and the difference in belt tension from cold to hot is huge.

 

What brand of microwave oven would you recommend for us wanna-be mechanics??