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Ts camshaft gurus. A question of timing...

14639 Views 126 Replies 13 Participants Last post by  pyle
Hey all.
A while ago I fitted 2.0 cams in the 147 1.6 and rejoiced at a power increase.
Then the front cats fell out, mysteriously ending up in the bin, and a 2.0 variable length manifold fairy waved her wand and did her one job in life....

All is well until I remembered a comment on a thread about timing up the cams on the 1.6 block. There was a statement about advancing the cams after being set up with the timing blocks. Ala:
"I think that the best way to do this is to use the 2.0 locking tools and then attach an angle measurement tool (not sure about its english name) to the crankshaft pulley and measure 9 degrees of crankshaft advance for the inlet cam.

If you choose to measure the advance degrees on the cam instead of the crankshaft you have to measure 4.5 degrees."

Now, I've not timed cams before, is that going to be worth getting my hands dirty?

Tia. Ian.
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Discussion Starter · #5 ·
LOL.. :)
Ok, so have done lots of research and read up on cam timing, and havve formulated a plan.

Now bear in mind that i have never "timed" cams up before and this is still new to me!!

Ok, find absolute TDC on #1 and attach the timing disc to the crank pulley and bolt up a pointer to show it at 0'.
Now clamp the inlet cam using the timing clamp and slacken the taperlock bolts on the inlet cam.
Now retard the engine by 9' and tighten up the taperlock on the cam.

In my head this makes sense......
 

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it does, but it's very hard to get it right if you're going to retard the crank. otherwise use the TDC gauge and mathemathically calculate how far from TDC you need to be to get 9°... saves you a crank timing disc.

or fit a vernier pulleys to the cams and adjust there, with double the resolution...
 

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I think that, there is no need to touch the inlet cam, it already has cams phase variator which advances the cam and by thurow advancing, you risk valve to piston contact. In my point of view, it is better to retard the exhaust valve do widden the lobe separatuion angle thus increasing the overlap without ( not sure about it.. ) valve to piston contact.
Please correct me if I am wrong. :)
 

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Discussion Starter · #9 ·
My head is starting to hurt with all he reading i'm doing. Angles,overlap,advance,retard,duration,lift,duration at .050.....,.aaaaaaaaaaaargh......(pop)..... :eek:

So, retarding the exhaust timing creates more overlap which helps infill of incoming charge and exfill of burned up, fast moving nasties?
 

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Cuore_Sportivo_155

Yes, overlap helps the high rpm filling, but the engine might not idle normally. My idea is not to touch the inlet cam because it has a system which changes its position, but the exhaust because it doesnt have such a system.

P.S. Cuore_Sportivo_155 also said, he made changes to the exhaust cam position.
 

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Discussion Starter · #12 ·
I did a silly thing.....i picked up a book by some bloke called Vizard*, and i have absolutely no idea what i'm doing now!!!!
My main interest now is the statement in the first post, as to WHY it needs advancing by 4.5 cam degrees....? The duration is longer, the lift higher, my brain then started melting at the fifth cam event, the overlap that draws the intake charge in by the exhaust charge having inertia on its way out of the cylinder.......
So how much overlap does the 2.0 have as oem? And the 1.6?

Camshafts=voodoo i tells ya......:eek:

*-david 'tuning god' vizard. There aint a lot he doesnt know!
 

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Discussion Starter · #15 · (Edited)
I've still got David Vizards book on tuning BL A series engines - the bloke really knows his stuff and its all backed up by flow data and rolling road results.
Oddly enough, that's where I got into it. My mad cousin has a badass 1380gt. Only just ticked over, the cams were so mental!

I love the fact he flow tests with a vacuum cleaner :D
 

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I did a silly thing.....i picked up a book by some bloke called Vizard*, and i have absolutely no idea what i'm doing now!!!!
My main interest now is the statement in the first post, as to WHY it needs advancing by 4.5 cam degrees....? The duration is longer, the lift higher, my brain then started melting at the fifth cam event, the overlap that draws the intake charge in by the exhaust charge having inertia on its way out of the cylinder.......
So how much overlap does the 2.0 have as oem? And the 1.6?

Camshafts=voodoo i tells ya......:eek:

*-david 'tuning god' vizard. There aint a lot he doesnt know!
the 1.6 has less overlap, but I don't know how much exactly. And that will be the problem, too much overlap for a 1.6, which will cause bad mileage (unburnt fuel and air entering the exhaust and being wasted). reduce the valve overlap area (when drawn on a piece of paper) by 20% and you'll probably have to advance the intake cam by 4.5 degrees.
 
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