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Discussion Starter #1
Hi all..

Recently had the head redone and at the same time stepped up to some new to me reground cams. Supposedly they are a Shankle regrind. I measured the lift of the lobes and came up with 9.8, somewhat disappointed as they were advertised as 10.1 or a euro grind. The duration looked similar although I cannot tell with the naked eye but certainly tame. The cams never came with a cam card so I dont know what the lobe centers are.....Centerline sold them to me used.

Anyways, my cam caps have more than one mark etched in them for set up. Regardless, I set them up to 102 degrees for both intake and exhaust. Am I maximizing my cam set up. Should I back off on my intake setting ..?

I have what seems like a detonation problem, and it really shows itself at part throttle and more when the car is colder not hot (unusual). I have rechecked the timing and made sure TDC was actually TDC when i had the head off with a dial indicator.
Can I have detonation probelms from my settings?

Car has good looking cylinders and pistons... 9:1, Spica, and single point Marelli, the mixture looks good, and running 89 octane here in Cali.

Other than that the car pulls well and I am happy with the power, but dont want to retard the timing any more as it feels really soft when I do.

Suggestions are more than appreciated :)
 

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Your description of the problem does sound like detonation. You do seem to know what you are talking about however so its a tough one to help with.
Its nt a loose chain is it?
Can you get another opinion on the "detonation"?
 

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Detonation Problem

I had similar problems with my Alfetta. Do you have the Marelli distributor? If so, I found the advance springs were too soft and letting the advance kick in way too soon. I experimented around and found that the springs and (modified) weights from a 'recurve kit' designed for a GM HEI distributor cured the problem. Still have the correct maximum advance, it just comes in slower.
Good Luck. :) :)

Larry G
 

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axis_powers said:
I have what seems like a detonation problem, and it really shows itself at part throttle and more when the car is colder not hot (unusual).
Yes. Very unusual. Detonation is usually caused by an ignition source other than the sparkplug. Like a piece of carbon glowing red hot which means the symptons get worse with a hot engine, not a cold one.
I'm with MrC on checking the t/chain tension although Larrys suggestion about the advance curve is good too.
Was there detonation before the head work?
 

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Discussion Starter #5
Thanks for the replies

Yes, I checked the timing chain tension when I first heard the noise and was very tight. After that backed of the timing and the detonation sound went away leading me to beleive there is a timing error. Although it was way too retarded(sorry for the pun ;) to drive.
That is why I am wondering if the camshaft timing could be the error?
Funny, the detonation on this motor sounds different than most cars, it has a metallic sound just like the sound of a loose timing chain!

Larry's idea seems the most plausible yet, I will look into some new springs for the dizzy.

PJ
No detonation before the headwork, and I cleaned up the tops of the pistons pretty well before the head was put back on. What plug should I be running, maybe I should move down one heat range. Car doesnt burn any oil.

Overall, Is 102 degrees on each cam sound reasonable?

Thanks
Shawn
 
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Shankle cam AL6205 regrind 10.1 mm lift (.397) recommended lobe centers is 100 if that's of any help. assuming that AL6205 is what you have. the late 2000 euro's are 99.5
 

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axis_powers said:
Overall, Is 102 degrees on each cam sound reasonable?
Yes, that's resonable. I think every Alfa alloy L4 on the planet will run reasonably well at 102 degrees. But, as alfa of-course points out, tweaking is most definately permissable. Like the 118 degree intake timing on the early '80s VVT cars for emissions. Anyway, I've never experienced a cam timing change to either cause nor eliminate detonation. The t/chain has been eliminated as the cause and since there was no detonation before the cam change, that would seem the rule out the distributor/ignition timing as well.

My next thought is that since the SPICA pump does not react to engine mods, perhaps the new cams have increased the volumetric efficiency of the engine enough to lean the mixture.

What sparkplugs are you using and what do they look like?
 

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I once had a knock problem, when I was tuning the max advance mark to the injection timing mark.... Stock motor...

Rather embarassing, as I looked at it at least 3 times before I figured it out...

Is that possible?

Eric
 

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Discussion Starter #9
Reset timing to exact specs, as it was off by about 2 degrees.... not much.
Also got a new (functional used)T/A and reset the rod lengths and mixture. detonation has stopped the the degree it was before, but the car is so loud that I cant quite tell in the upper rpms.
She is certainly mechanically noisy! but I love it. I feel like I lost a bit of the power she had but maybe now I can play with the cam timing a bit.
I still think maybe I should get the Marelli on the distributor machine and check the advance curve.

Anyways, thanks for everyones help and suggestions
Shawn
 
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