Existing CAM Timing Question

[RRoller123]

I am in the process of replacing the timing belt/tensioner and front seals and have a question. The EXISTING timing looks fine with the exception of the exhaust Cam, and I am wondering if it is normal or if it has always been off a tooth? So far I have removed the radiator and associated plumbing, removed the hood, did a basic engine front degreasing, and rotated the engine to #4 piston TDC.

Here are the existing timing pictures:

CRANKSHAFT:



AUX SHAFT:



INTAKE CAM:



EXHAUST CAM:



Everything lines up well except for the Exhaust Cam. Is this amount of misalignment normal? Or is it off a tooth?

[djape1977]

either your engine is something i havent seen so far, which i doubt, or aux shaft position is way off, it should be at aprox 2 o'clock, pointing at bolt that holds distributor, and last 10 times i changed timing belts on fiat twincams i used markers on top of cam housings to line up camshafts, not the cam cover holder plate. also, markers for lining up crankshaft are on cam cover.

by the way, it's perfectly possible to have exaust cam off by a tooth and engine will appear to work fine, but only to someone who had never driven a fiat twincam powered car. line it up correctly and you'll be amazed at difference in power output of the engine

[boogiedude]

either your engine is something i havent seen so far, which i doubt, or aux shaft position is way off, it should be at aprox 2 o'clock, pointing at bolt that holds distributor, and last 10 times i changed timing belts on fiat twincams i used markers on top of cam housings to line up camshafts, not the cam cover holder plate. also, markers for lining up crankshaft are on cam cover.

by the way, it's perfectly possible to have exaust cam off by a tooth and engine will appear to work fine, but only to someone who had never driven a fiat twincam powered car. line it up correctly and you'll be amazed at difference in power output of the engine

The picture was taken with the camera at an angle. That is the correct bolt to have the aux shaft pointed at. The timing belt tensioner bearing bolt

[RRoller123]

The Aux shaft timing is not incorrect, as per my manual. The mark is supposed to lie on a line directly between the pulley bolt and the bolt holding the tensioner, which it does.



The crankshaft timing from '79 on is by this pointer, not the plastic timing belt cover, (probably changed for warpage and parallax reasons) so this is also correct:



The CAM housings have casting marks on the backside that coincide exactly with front pointers, so they are correct as well. I use the front pointers because it is much easier to see.

Here is the backside intake cam pulley casting mark aligning properly with the hole:



And here is the backside Exhaust Cam pulley mark and casting indicator. It indicates the exact same reading as the front pointer:



So my original question remains in force. Is this a normal difference between the two Cams? It seems to be too much to be explained by belt stretch.

[So Cal Mark]

it's difficult to get the marks exactly with the pointer unless you have adjustable gears. If it's off one whole tooth, it's wrong. If it's less than a full tooth, it could be the head has been resurfaced or the belt has stretched

[RRoller123]

Thanks, Mark. I only know the history back 12 years so it is unlikely that the head was resurfaced, but certainly it is possible. Looking at it, it seems like maybe indexing it by a whole tooth might get it closer, but probably move it a little too far to the other side. Maybe at last belt change they just picked one side or the other? A compromise? Anyway, I guess it is a moot point as a new belt is going on shortly. I will use the casting index marks on the cam covers. Just wondered if this much misalignment would cause performance issues? The car presently runs fine, plenty of low end torque and smooth all the way up the range.

[djape1977]

i stand corrected.
i never realised that cam cover holder also marked cam timing

[RRoller123]

No problem! Do you think I will see a difference in performance with the exhaust aligned closer? I have no experience with this type of engine tuning (i.e cam timing effects) but I would expect that having delayed exhaust action, even 1 tooth on the belt, would have some noticeable effect?

Pete

[djape1977]

last year a customer brought a 1970 spider with 2 liter engine upgrade to my place for a clutch replacement. i test drove it and my first question was "ok, i'll change the clutch components, but have you noticed that something's wrong with the engine?" - reply was "no, why?"
it was starting good, runing smooth tru RPM range but there was no power. maybe 60bhp at most. i found that timing was off by a tooth at the crankshaft. after i was done with it it was burrning 205/60/13's in the rear in 1st and second gear as long as i would hold pedal to the floot.

when customer came to pick it up he said that in 4 years he owned it it never produced anything near that power and that he wasn't even aware that a 124 could be that fast.

all in all, try to re-set the timing belt so that marks are close as possible to ideal, if you can't get it to allign, get a new timing belt. if that doesn't help, adjustable camgears are the way to go.

[RRoller123]

Thanks, the belt going on is brand new, just waiting and waiting and waiting here in New England for the rain to stop. We went from terrible drought all late Winter/Spring to absolutely no drought now. Made up a 7"+ rain deficit in about a month!

Pete

[narfire]

One tooth off on the gears is noticable after you correct to close as possible. I noticed the difference on my 2L a few years ago when I had the same thing.

[RRoller123]

Excellent! Let's hope this is the case on mine. Still waiting for the rain to stop... day after day here....

[djape1977]

when replacing the belt, allign everything, tighten the tensioner then rotate the engine with a wrench so that crankshaft makes at least 2-3 full rotations and then re-set the tensioner. rotate clockwise.

[RRoller123]

Yep, will do, that procedure is indicated in the manual I have. Funny how much digging it took through 2 manuals to find which way to rotate the engine. Clockwise on the Crankshaft as viewed from the front. Sometimes the smallest, but most obviously important things are the most obscure!

[giuliot60]

Hi Pete. How did this turn out?

I'm attempting to replace some parts on my dizzy, but I'm having trouble seeing the timing mark on the crank pulley. Similar to your but mine doesn't have a mark. So I'm searching for timing posts.

I'm learning that timing can have a huge effect on the car's performance and was wondering how you resolved you exhaust cam line up issue?