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Discussion Starter #1
I have now a 2Liter with the 10.4 Borgo Pistons, Deves rings. 11mm Cam with 256 degree duration and now...
What should I do to the head?
Port/polish bigger valves?
Shave it?
I currently have 40DCOE Webbers now.
Are they good? Or should I go to 45's?

Oh! I have the 2 piece cast Iron Euro style header.
Should I get the steel IAP Header they have available?

Hoping for around 160-170HP fly HP. :)
 

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The first thing you should do is read the High-Performance Manual that was written by Jim K (do a search here, there's lots of references to it, I can't remember the spelling of his last name!), it covers all of the questions you've raised, and is considered essential reading for anyone building a high performance Alfa engine.

Then I suggest you plan out what you want to do, so that you're not having to continually pull the engine apart everytime you decide to do another modification. Building a high-performance engine needs a planned approach.

You also need to consider what you want to use the car for, street or track, as that will make a difference in some of the decisions you have to make.

But in answer to some of you your question above, and assuming it's for street use....

45mm carbs are preferred over 40mm if you're building a performance engine.

As far as porting the head, don't let anyone touch it until you know exactly what you want. Lots of people have ruined 2lt heads because they ported them without knowing exactly what they were doing. Generally you'll be looking to improve the dimensions and shape of the inlet port, but I'm no expert, and Jim K is, so read his book! There's a general view held that you should increase the size of the inlet valves, to perhaps 46mm, but leave the exhaust ports as standard.

If you want to shave the head, be very careful. If you're already running high-comp pistons and you shave the head, you could end up with compression that's too high for street use with street fuels, and get detonation which can damage the engine.

You also have to think about the bottom end. If you build a high-compression, high-revving engine, and ignore the bottom end, you could have some major problems. You need to consider making the bottom end more durable, and balancing it. Once again, Jim K's book deals with this.

Building a high-performance Alfa engine isn't about just bolting on a few go-fast bits. If you really want to build a nice engine that will last, you have to take a very carefully planned approach!
 

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There's a general view held that you should increase the size of the inlet ports, to perhaps 46mm, but leave the exhaust ports as standard.

If you want to shave the head, be very careful. If you're already running high-comp pistons and you shave the head, you could end up with compression that's too high for street use with street fuels, and get detonation which can damage the engine.
!
46 inlet port is HUGE ... best size for under 100hp/liter is close to valve throat area or 90% of vlave head :)

stock exhaust port is small compared to valve head size and short side of port is awfull too :)
 

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Carb throat should be 87% of intake valve head diameter to be precise, which will allow the potential to reach the maximum of 130% volumetric efficency for a normally asperated engine. ;)
... and for 120+ VE potential we need around 5000 fps piston speed or 8500 rpms ... isnt it so simple with nimbers only ;)
 

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Carb throat should be 87% of intake valve head diameter to be precise, which will allow the potential to reach the maximum of 130% volumetric efficency for a normally asperated engine. ;)
Using your numbers on a 43mm intake valve (43mm x .87= .3741), that would make a 36mm venturi or rounding up you would use a 38mm venturi in a 45DCOE. How streetable is a 36 or 38mm venturi? I can understand there is some loss at low end but top end would be breathing good. :)
 

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What should I do to the head?
Port/polish bigger valves?
Shave it?
Caesar:

You have the basics down for what you need to do. 160hp is certainly attainable on a 2L with the mods you are thinking about.

As others have mentioned, you really should buy Jim Kartalamakis' book on tuning 105 Alfas. The modifications he describes in his book are all things that he personally tested on motors he built himself. If you follow his directions, you will have a very nice, powerful Alfa motor. In particular, his instructions for modifying an Alfa cylinder are quite good. Again, they are based on his own experiments and developments with a flow bench and report what he actually ran in his car. I'm not an expert, but I have ported several heads. The last head I did is very close to Jim's dimensions (the intake valves are a bit smaller), and I'm pleased to say it worked very well, indeed.

Porting Alfa heads is lots of fun, but if you don't think you are up to that complex a project, it's relatively easy to find someone who can do a quite professional job of building a modified head for you. One thing you should keep in mind, however, is that porting heads is as much art as science. People who do this work have their own methods and secrets which may be a bit different from what Jim K recommends. You shouldn't let this bother you. If you are dealing with someone with a known reputation for building competitive Alfa race motors, that person is going to build you a good high performance head.

As for your other questions (cams, carbs, compression, etc.), there is a wealth of information avaliable to you with the forum search feature. It's really amazing what you'll find. :)

Good luck!
 

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... and for 120+ VE potential we need around 5000 fps piston speed or 8500 rpms ... isnt it so simple with nimbers only ;)
Sure it is, provided you take harmonic pulses and intake runner length into consideration :)

Engineering: it's about the math......


velocedoc said:
How streetable is a 36 or 38mm venturi?
Honestly I wouldn't know as I don't have Webers.

There really is a lot of other variables to consider and all the formula will do is ensure that the potential to achieve maximum volumetric efficency is there, not that the engine will actually do it.
 

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Discussion Starter #10
This info is great, and I just placed my order for Jim's Book on High Performance Alfa's

So I'm going to keep my eyes open for 45DCOE carbs, and I wll go the route of porting and polishing with bigger intake valves. ( So no need to touch the exhaust valve?)
Different than a Chevy! LOL :)

I'll make sure they don't shave the head too much. I need to run on atleast the 94 Sunoco over here.

What's your take on headers?

I can't Thank you guys enough :)
 

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My rule is: Never shave a head unless it is absolutely required. Cheap and nasty way to increase compression. One day, people will all be running around looking for 2 L heads that are thick enough to work with. A bit like it is with 1600 heads now. When the head is too thin, you get interference with the valve reliefs, the piston can hit the combustion chamber and the valve seat starts to distort when the head is torqued down.

Engine shops love to do it because they get a few more beer tickets in their pocket, so ask that it is done only if needed and bare minimum off.

I have had very good results (back when I had access to machinery) with converting the standard valves (if they are thick enough) to 45 degrees, 1.5 mm wide seats, reshaped backs and a nice three angle seat job blended into your port. IMO, the main benifit of the 45 mm valves that are so trendy is not the bigger size, but the better angles.

45s are the way to go.... I have run them with 38 mm chokes on on a road engine with about 175 bhp and it was usable from 2500 to 6500 rpm, with good flexibility down low.

The bottom end at this sort of tune is fine.
 

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The 2 L in my Spider is running 10.4 cr, Shankle 7 L cams and the 45s.

The throttle linkage on the install needs some sorting out, but it, as of today, has a good tune on the carbs:)--effective from 2500 to 6000--haven't tried higher.
 
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