alfa 2600 camshaft timing with weber set up

[franco-veloce]

Hi John,

I have a set of 3x NEW weber 45 dcoe 9 for sale

the webers are sold
rgds Franco

[johnrdm]

Thanks Franco - can you pm me or email me (john@dnaprods.com) with a price.

Where are you located in the world?

I am in LA.

John

[Redmerlin]

Before you buy new Webers or secondhand- check they are right for a 2600 - I don't actually know what is right - but I can post what mine are when I check.

There is another post on the BB about problems with flat spots on Webers when fitted to a 2600. Something to do with having 1 .2 or 3 progression holes under the throttle butterfly - this differs for different applications.

I have also seen two cars which run dellortos , these run well but with a converted mnifold.

In this modern age someone should fit a mega-squirt electonic injection system or similar . These are now available for straight 6 jags and should be easy to convert Then you can use the Solex manifold . dial in the fuel settings required and have a better result than any carburettor system.

You can probably do this for a similar cost - ie 3 webers fully rebuilt £ 1,000 plus de-siamised manifold say £500 = cost of a megasquirt conversion

And Yes - Alfa did fit fuel injection in atleast one 2600 - I have seen two pictures of this - in an old Alfa plus magazine

[johnrdm]

Thanks Redmerlin - I'd like to know what Webers (and their internals) you have, and if you have any drivability issues.

I read most (all?) of the weber related posts and am still confused! One brave owner drilled an additional progression hole himself...

I did consider the fuel injection/distributor-less ignition/megasquirt option, but decided against it in the end - although I would be interested to see the factory injected car.

I am thinking of going the Pertronix Ignitor II route (with Flamethrower coil) first (rather than the 123 distributor route) as my distributor looks in very good condition and the Petronix system is cheaper - do you happen to know which model I should get. Or is this false economy?

John

[2600sprint]

I advanced my inlet camshaft 10º (6 holes=9,6º to be precicely) yesterday, with good results. I run 40mm Dellortos and a desiamesed solex manifold. The exaust camshaft is currently retarded 4,5-5º. (Yes, the large 27mm nut is stuck). Will a proper adjustment make any difference?

Thanks / Erik

[franco-veloce]

Yes,

a proper adjustment of the jets /venturi etc will give more power

rgds Franco

[2600sprint]

-Yes it did!

I turned my exhaust camshaft "forward" to its proper timing, and yes, the engine performs better!

Thanks / Erik

[johnrdm]

Hi,

I just want to make sure I am understanding the 10 degree advance adjustment correctly, as it sounds like members are finding this change advantageous, and I'd like to try it without damaging my motor...

The inlet cam is the only one that is adjusted.

The adjustment is 10 crankshaft degrees advanced from normal.

This means I need to loosen the large locknut, remove the lock bolt and turn only the inlet camshaft 6 holes counterclockwise (looking from the front of the engine), and reinsert the lock bolt and tighten the locknut.

This 6 hole adjustment on the cam corresponds to 10 degrees of crankshaft rotation.

Is that all correct?

6 holes sounds like a lot, as 10 degrees on the crankshaft corresponds to 5 degrees on the camshaft (cam rotates once for every two crank rotations)...

John

[2600sprint]

YES, The inlet cam is the only one that is adjusted.

YES, The adjustment is 10 crankshaft degrees advanced from normal.

First, check that both camshafts are ajusted to their original position.

This means I need to loosen the large locknut, YES, remove the lock bolt, YES, and turn only the inlet camshaft 6 holes counterclockwise. NO, CLOCKWISE. All shafts rotating clockwise (looking from the front of the engine), and reinsert the lock bolt and tighten the locknut. YES

This 6 hole adjustment on the cam corresponds to 10º of crankshaft rotation. NO, There is an error here. 6 holes on the camshaft corresponds to 10º on the camshaft.

6 holes sounds like a lot, YES, as 10º on the crankshaft corresponds to 5º on the camshaft (cam rotates once for every two crank rotations)...

I obviosly made an careless error here, but I checked for valve/piston conflicts before cranking, and yes, it works. Possibly the engine would benefit from a camshaft retardment from my current +20º advance back to +10º.


Thanks / Erik

[johnrdm]

Thanks Eric,

Appreciate you going over that.

So three holes clockwise would be the go?

Is there a measurement from the TDC position markings on the cams that I could use?

Would it be: diameter of cam (in mm) at markings, multiplied by Pi (3.14159) divided by 360 (= distance of 1 degree in mm) multiplied by x 5?

Perhaps that is the 3.5 mm Franco mentioned?

John

[2600sprint]

No problem, John,

-YES, three holes clockwise would be the way to go.

Is there a measurement from the TDC position markings on the cams that I could use? -YES, but it is very hard to messure acurately.

Would it be: diameter of cam (in mm) at markings, multiplied by Pi (3.14159) divided by 360 (= distance of 1 degree in mm) multiplied by x 5? -YES

Perhaps that is the 3.5 mm Franco mentioned? -YES, but probably more like 2.

It is more convenient (and precise) to calculate the desired angle in # of holes.

It is advicebly to mark the camshaft and the chainwheel before adjusting, so you are sure of the original position.

Thanks / Erik

[Sputnicker]

This is a great discussion. Thanks to whoever discovered that the original cam timing might be less than optimal. Thanks to Franco for being the first to try the new timing and report back. Thanks to Eric for his detailed description of the procedure. Thanks to John for asking the same questions I had.

I still have two questions:

Erik - Did you change your settings back to 3 holes (5 degrees at the camshaft)? If so, was there a noticeable difference in performance?

Franco - How did you calculate the 3.5mm and where are you measuring it? Are you sure you have 10 degrees more advance on the crankshaft (5 degrees at the cam), or is it 10 degrees on the cam?

Thanks,

Barry

[2600sprint]

-No, I haven't, but I will. I'll let you know.

Thanks / Erik

[franco-veloce]

dia camshaft 40mm x 3,14 / 360 = 0.35mm per degree

X 10 degrees = 3.5mm

this is based on cam and not cranckshaft

rgds franco

[Sputnicker]

Thank you Erik and Franco.

If I understand it correctly, it seems that both of you have made the same adjustment and experienced a performance improvement. Each of you advanced the inlet camshaft by 10 degrees, which equates to 20 degrees at the crankshaft. If the standard timing started out as 20 degrees of crankshaft advance, you now have 40 degrees (not the 30 degrees Franco reported on 6 August). The spec sheet earlier in this thread (with Piper at the top) says that advance is measured in crankshaft degrees (which makes sense to me). Franco's initial post says that other Alfas have between 34 and 41 degrees. So it seems that the adjustments you have made are still within that range (at 40 degrees), but on the high side of the range.

It appears that there has been some confusion about camshaft degrees versus crankshaft degrees, but the 6-hole/3.5mm adjustment at the cam seems to be an improvement, regardless. We still don't know what the optimal advance is, but it seems like 40 degrees is better than 20 degrees, based on the experiments from Erik and Franco.

Please let me know if you disagree with any of my assumptions or conclusions.

Regards,

Barry