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Discussion Starter #1 (Edited)
Does anybody have a cross section drawing of the cylinder head?

On high rev my valve stem seals are leaking a bit, so I'm planing to prepare another head without stopping the car (GT 1300 Junior 1970).
The new head should be ported and probably will have larger intake valves. This will be a mid term project, now I'm collecting all the necessary information.

I read the Jim K. book. Regarding porting; he warns about breaking through the walls in case of excessive grinding in some areas (for example between valve seats and guide).

Does anybody have a cross section drawing or picture of the head to use as a reference?
In the Jim K.'s book there is only a very small one.
Best would be a section drawing of the 1300 engine, but sections for larger engines will help either.

Any further information or your experience about porting is welcome.
 

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Discussion Starter #3
Thanks a lot Gordon!
This will help.
Can you remember to which engine this image belongs?
 

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71 Berlina 74 GTV 17 Giulia Q4
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That is a great photo! Hope you don't mind I saved it in my Alfa folder:)

Here is a photo giving one an idea of how much meat is removed in porting the exhaust. The red is the ported dimensions over the black of a stock 2L head. Photo credit is JimK. It's a great book and cheap at twice the price:)

 

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I believe that head section is a 2L.
 

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intake pocket thickness

Problem is that castings are all different. Our head man uses a sonic tester to measure before the chips fly. If a casting flaw appears while he is grinding it gets heliarc repaired. Pricing and description of the work is on our website. Turn around is 3-4 weeks. We also have 8mm stem oversize valves, guides, retainers, etc. for all 105 four cylinder engines.
 

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Paul is 100% right. Newer stuff less so than older. All the old stuff I get to work on suffers core shifts and you just can't tell when you might run into ... air ... The sonic tester is like a metal thickness tester that can locate thin spots before you find them by accident. Always a problem in porting jobs.
The other issue here is that there are many more 2L head casting versions than the 750 /101/105 heads. I have no idea which is which, but Paul probably does, and SOME are probably better porting candidates than others!
Just my opinion as usual.
 

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In the Jim K.'s book there is only a very small one. Best would be a section drawing of the 1300 engine, but sections for larger engines will help either.

Any further information or your experience about porting is welcome.
[/QUOTE]

JimK gives measurements for 1300s in his book. You just have to look through the chapter to find them. If you don't go beyond what he's suggesting, you should be ok although, as said, when you start removing metal you always run into increased risk. You might go ahead and buy a couple of spare 1300 heads just in case.

Recently, I dug out an old head I dd back in the mid 80's using David Vizard's Theory and Practice of Cylinder Head Modification as a guide. The other day I compared what I'd done at the time with measurements from JimK's book and also with measurements from an Engine Machine head from L.A. I was surprised to find that my port dimensions were within a couple of mms of both heads. Talk about newbie's luck. :)

Here's a photo of what the valve throat of a ported 2 liter (circa 1985 or so) head looks like. The stock valve seats were counterbored .050 and used John Shankle's idea of narrow seats and oversize valves with 30 degree seats. The exhaust valves were stock. The next time I port a head I'll use seats with more radius.

If you're serious about porting your own head I'd suggest finding a place away from human habitation to do the work. The work will take you a lot longer than you might think and die grinders are very noisy. Although all the books tell you to use one, I found that using a electric drill, although a lot slower, was easier to use in critical spaces.
 

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