Guide boss porting tool-prototype

[johno]

Hi guys, iv been racking my brain for a while now thinking, as surely some of you already have, that there should be an easier way to finish 'Cast-in Guide bosses' that also gives excellent flow results!! Well i think iv solved the problem, or im at least close to it, with a special tool iv invented!! Check out the results on this VN 5ltr. EFI head!! Only takes half an hour to apply and increased std. flow from 134cfm @ 10" to 138cfm @ 10" / 0.650" with absolutely no other work or changes what-so-ever!!! Still not sure whether i should patent the tool & market it or just keep it to myself?! Heres what they look like finished!!

[Greg]

Nice job Johnno, they're an ugly guide boss to start with. How do you go with the exhaust one? I normally bore them for a press in guide and remove what's left but it's quite a job.

[johno]

The actual intent was for the tool to shape the boss like an EFI insert, as you may have found this shape provides minimum restriction to flow. I'm still testing different cutter shapes and have yet to apply it to the exhaust side but i'l have to be careful around the back side of the guide boss as the factory did'nt leave a lot of metal here (walls only 4.5mm thick), should have an exhaust boss done by saturday to post. What sort of numbers have you gotten out of these heads GREG?

[Greg]

From memory around 270 intake and 205-10 exhaust @ 28" with a 2" intake and a 1.65" exhaust @ .550". They are a head that could do with some port filling on the intake, I'm just a bit suss of epoxy in a street engine.

We did have a pair at just under 300 on the intake but that was opening the entire port to the top of the injector notch and was a pair of the D port group A heads to begin with using 2.080 & 1.65 valves I'm pretty sure. I wish I had some photos, the exhaust was very good, just can't remember the numbers.

[johno]

Were they actually grinding the injector notch out of them? The head I'm working on is std. valves & chamber and iv managed to get them flowing 141cfm @ 10" 0.600" lift, without too much effort using the guide-porting jig. From this i had predicted that a 2.02"in valve would pump it out an extra 15-20cfm @ 10" T/P. I was close, by your figures! Thanks for that extremely useful info mate!! :;):