Timing Belt and Pulleys

Maintenance advice to keep your Spider in shape.
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Skyebot
Posts: 7
Joined: Sat Aug 29, 2020 8:26 pm
Your car is a: 1978 124 Spider

Timing Belt and Pulleys

Post by Skyebot »

Hi Everyone,

I have a '78 Spider 1800. Recent rattling of worn out water pump and unknown age of timing belt have compelled me to change the belt and pump.

-I've pulled and drained the radiator + removed timing belt cover + pulled water pump
-I then began cleaning and (impulsively) decided to pull the tensioner bearing/spring/plate.....and pulled the timing belt.
-I also did this BEFORE turning the motor to TDC/aligning the cam pulleys to align with pointers.

I haven't touched anything, but am now concerned about putting the belt back on.

If I proceed, I thought I could clean everything up, disengage the transmission and work all of the individual pulleys to the optimal....
1. Crank pulley: TDC (likely use the timing cover mark of TDC)
2. Aux Pulley: 1 O'clock 34 degrees
3. Cams: align with pointers or cam covers.

But..... I am concerned that moving these independently will not be possible or will potentially result in clash/misalignment in the process

-Is it possible to move these pulleys individually by hand to get set up for the re-belt or is this a no-go?
-Engine appears close to TDC based on crank notch and cam pulleys so only minor rotation should be needed

I would love thoughts on this, as I don't want to mess this up terribly.

Skye
18Fiatsandcounting
Posts: 3780
Joined: Fri Mar 15, 2019 11:23 pm
Your car is a: 1969 and 1971 124 spiders
Location: San Francisco Bay Area

Re: Timing Belt and Pulleys

Post by 18Fiatsandcounting »

You won't mess it up, and you can't do any damage by turning things by hand. Here's what I would do:

1) With the transmission in neutral, rotate the crankshaft so you are 30 degrees or so past TDC on the #1 piston. You can check this with a screwdriver in the #1 spark plug hole, watching that the screwdriver (resting on the top of the piston) had traveled downward an inch or two. No precision is required; you just need to move the pistons off TDC a bit.

2) Set the camshafts so that the timing holes for both are aligned with their timing "nubs" on the camboxes.

3) Rotate the engine back to TDC on #1, using the pointer on the timing cover or the screwdriver method above.

4) Make sure your auxiliary shaft pulley pointer is 34 degrees past noon, as you mentioned.

5) Install the timing belt, check that all timings marks line up.

6) The distributor rotor should be pointing towards the #4 cylinder plug wire on the distributor cap.

7) When everything appears lined up, rotate the engine by hand through two revolutions (a safety check to make sure something won't bind).

8) Fire that bad boy up.

9) Quaff a beer or two.

-Bryan
Skyebot
Posts: 7
Joined: Sat Aug 29, 2020 8:26 pm
Your car is a: 1978 124 Spider

Re: Timing Belt and Pulleys

Post by Skyebot »

Much appreciated feedback Bryan - I see what you're doing here by moving the pistons down and out of the way of the valve gear - I'll proceed as indicated - and will update you on the process + the beers!

Skye
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