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Costa P Costa P is offline
Slippery slope skier
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Join Date: Sep 2010
Location: South Africa
Posts: 179
Hi Jim,
thank you for your feedback.

I am very familiar with the work you did on your 930 heads....your post provided much inspiration, motivation and guidance before I attempted this myself (refer to my post #48)

Originally Posted by Costa P View Post
......Valve guides protected with plastic tubing as per Jim Fairman's post
made some more aluminum dust.........
I agree with your view regarding leaving enough material around the valve guides. The photo of the inlet port (refer post #49) still has the plastic tubing around the valve guide. At a glance, it appears that I have removed material right up against the valve guide.

Originally Posted by Costa P View Post


Here are some pics with the tubing removed:

....In fact I was very paranoid to not remove too much around the valve guides. If this area becomes too thin, it could cause problems in future when you need to replace the valve guides! (cracking etc).

I have decided to go with a 37mm size inlet port.....large enough to improve breathing but not too large to sacrifice low-mid range. Ironically, this size was a result of the max port size limit on the plastic CIS blocks....which I dont plan to use anymore!

My ports were cut in a milling machine. I only blended the transition by hand. I didnt have that much material to remove, which is why I was able to cut dry and not have trouble clogging the tool.

In your case, you had to open them up from dia 32mm to dia 40mm....thats quite alot of material to be removed. Which explains the need for WD40, scraping the flutes of the burr etc etc

Lastly, very valid points regarding the adjustments required to the AFR.
Which is why, very early on, I made the strategic move to upgrade to EFI
Costa P
'85 930 Grand Prix White ...the oil leak rebuild which mutated into MoTeC EFI+twinscroll GT35R+twinplug+ ...

930 rebuild The revival of my mothballed project
Old 11-26-2016, 10:26 AM
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