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alfa 2600 camshaft timing with weber set up

15K views 63 replies 13 participants last post by  DPeterson3 
#1 · (Edited)
Hi All,

The standard 2600 inlet cam timing is 20 degrees before TDC and 70 after BDC

All other alfa engines 1300/1600/1750/1800/ 2000 CC with weber ,dellorto and solex double sidedraft carbs have inlet cam timing between 34-41 degrees before TDC and 58-61 after BDC.


Is this for the solex 44PHH and also for weber 45DCOE9 ??

I can't find a different cam timing for the weber 45DCOE9 set up in my alfa 2600 documentation/data sheets .

I think the engine performes better with inlet cam timing between 34-41 degrees before TDC and 58-61 after BDC with the weber 45DCOE9 set up.

Does someone have experience ?

rgds Franco
 
#2 ·
Hi all,
I changed today my standard 2600 inlet cam timing
( 20 degrees before TDC and 70 after BDC )

to 30 degrees before TDC and 60 after BDC

with nice results : better response on acceleration between 1500-3000 rpm and above 4000 rpm the 2600 goes like a Ferrari ............

rgds Franco
 
#3 ·
That's great! Thank you for posting the results -- I can't wait getting to the point where I can try this myself.
 
#6 ·
FYI, to address some off-BB questions: The cams for the 2600 SZ are the same as for Sprint/Spider (106.01.03.200.00). So far, I have not seen any information that would suggest different timing settings.

The only significant difference between 2600 SZ engines and Sprint/Spider engines are the engine mounts (the engine is placed 8 mm lower on 2600 SZ).

BTW: It's a myth that these cars were supplied with Webers as factory standard. Webers were optional the same way they were optional on Sprint/Spider. Most cars seem to have been sold with Solex carbs but quite a few were converted to Webers.
 
#8 ·
It seems like a fair number of sprints came with Webers (including the 2600 sprint raced by Elio Zagato), but I don't know of a single spider that came from the factory with Webers.

The Webers were also an option on the OSI 2600 berlina...but I don't know of any that had this option! (54 OSI's were made, only 2 are know left, both at the Alfa Blue Team in Italy)
 
#9 ·
2600 Piper cams

For reference I have a set of 2600 cams made by Piper in the UK - they were described to me as 1750 profile cams for use with Webers.

Inlet Open 30 degrees BTDC Close 70 degrees ABDC
Exhaust Open 70 degrees BBDC Close 30 degrees ATDC

as attached

Due to fit at Christmas

nb approx 7 OSI's left - two in Germany

Ian
 

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#10 ·
Hi All,

theoritical these "1750 " cams with 1750 webers carbs must give the 2600 about 180 PS ??

1779 cc x 1.5 = 2668cc and 120PS x1.5 = 180 PS

My car with the 10 advanced standard inlet cams and weber 45DCOE 9 goes from 0- 100km/H < 9 secs but I think the "1750" cams gives better result.
 
#11 ·
Piper cam query

Ian (RedMerlin)
Were the piper cams new or did they grind (reprofile) a spare set. Just wondering as I am way off the point where I need to worry about cams, but its all useful info for the (hopefully not too distant) future!
(apologies to Franco for thread hijack!)
Regards
Bryan
 
#13 ·
Questions for Franco

Hi Franco,

I have read this thread (and other Weber related threads) as I am seriously considering changing out the Solex's on my 2600 spider.

You seem to be having good success with your Weber set up, and I have some questions that I hope you can answer:

It sounds like you have gone with 45DCOE9's. Can you tell us what the sizes of the variable parts are (venturis, main jets, Aux jets, Emulsion tube, Air correction, Idle jet, Slow(start) jet and pump jet (to name a few!))?

Also did you only adjust your inlet cam 10 degrees advanced, or did you also adjust your exhaust as Adrian did (inlet cam advanced one hole, exhaust retarded one hole).

Are you running the original Solex manifold or did you de-siamese it?

Thanks,

John
 
#15 ·
2600 into the 21st century (kind of)

Thanks very much Franco,

An original Weber manifold, thats cool!

In my fascinating journey into Alfa arcana, and my attempt to bring my 2600 spider in the 21st century (without scarring it permanently) there are a couple things that many people seem to agree on: 123 ignition, new coil, and a GM alternator. Iridium plugs seem like a good idea too. I hear power, rather than armstrong, steering would be nice, but believe that is a bridge too far...

I also plan to change out the Solex carbs for Webers, and I am trying to get a consensus on the best approach to fit them to a 2600, but am not having much luck!

Many people advocate modifying the Solex manifold, but some have reported good results without any changes. All seem to agree the original Weber manifold/set up is best - however this seems to not be a valid option...

Some like DCOE 40's and some like 45's (I understand both can work).

The procedure for determining carb and venturi size seems a bit of a black art, as when I extrapolate from the graph on page 2 of the "Selection and tuning of Weber DCOE Carburettors" pdf (attached) - I get a venturi size of 40, giving a barrel size of 50! (interestingly I see OK parts offers a 50 DCOE...)

When I look at another graph which uses cylinder capacity (see below) I get a venturi size of 34mm using a per cylinder capacity of 433cc.

Franco tells us he has had good luck with 33mm Venturis on otherwise standard 45DCOE9's (through an original Weber manifold).

Adrian (in other posts) advocates 40's with 33 venturis, or factory standard 45's (36mm venturis) through, I believe, an unmodified Solex manifold.

So what to do?

I guess I'm leaning toward buying three new 45DCOE 152's, and see how they go through my unmodified Solex manifold.

I am also leaning to following Franco's lead and advancing the inlet valve timing 10 degrees

Thoughts from the brain trust?

John







I
 

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#18 ·
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
 
#19 · (Edited)
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
 
#20 ·
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
 
#23 · (Edited)
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
 
#24 ·
Hello John,

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
 
#25 ·
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
 
#26 · (Edited)
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
 
#27 ·
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
 
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