comnoz said:Fast Eddies RH10 head before and after a street port job with 3mm oversized intake valves.
I use JBweld on a roughened floor in BSA A65 ports. Never had a problem. Only inlets naturally.Gday All,
this is a very intersesting thread, keep it up!
Just wondering has anyone tried an inlet port insert to build up the port floor! Perhaps this could be made from pressed stainless and held in place via the manfold bolts and a devcon type product to hold in situ along the port floor?? :?:
That's fantastic to see. I've been trying to figure out why a ported head on a stock A65 650 makes so much difference both in response and top end. The response is really nice and instant. I have vacuum cleaners and measurements based on a std BSA port being 109cfm and basing calculations on it. The numbers are just what it gives and probably optimistic, but the relationship is indicated. The red and the green line are through a 34mm PWK. I have stuff to make something to measure port velocity which I can compare when I get time.Well here are flow results from Ken's Maney stage 3 head. Big flow numbers for sure. Huge ports and 1.690 inch valves for big inch high RPM use only. The red line is the Maney head . Green is a standard Fullauto and blue is a RH4 that has been flowed by persons unknown. I went all the way to .500 lift although few cams lift beyond .420 or so. Jim
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Here are the velocity numbers. They are what matters if you want a wide powerband.
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I've been using a manometer with plastic hose in the port to get an idea of velocity. Hope I am doing it right. Vizard has a chart reading up to 38"w which equals around 400fps. That approximates speed if the bench is testing at 28"w... in theory. Depending where I put the hose end I can get 34" 380fps just in the manifold, 40" 420fps in the port and down near the guide 52" probably 450fps? But that's beyond his graph. It varies depending where it is, it seems fast on the short turn, not that I can see it so well and the hose in there probably affects it.So now that I identified a problem with my prior velocity readings and corrected them -here is the flow tests with the 1.5mm oversize intake and a little work in the valve guide and bowl area.
Nice improvement for a steetbike running a .400 lift cam.
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I think what that refers to is related to the Spitfire head of 1968 #68-915 they had special ports deeper and wider in the bowl. There is a detailed engineer's drawing. It meant a Spitfire with 9-1 comp and 32 Concentrics could make 56.5hp. The factory did not extend that improvement to the standard models, only those Spitfires. The different head didn't even make it into the parts book, the 68-701 was still listed. In 1970 Umberslade engineers built an engine with head ported to 'the drawing', I expect it was that one. Looking at a '71 head in the bowl area, it isn't that noticeable without measuring, but it is as that Spitfire drawing. It's not great but measures around 120 or 122cfm an improvement on the 68-701's 109cfm. The '71 head used the 30mm carbs.Mark writes: " I've been trying to figure out why a ported head on a stock A65 650 makes so much difference both in response and top end."
I have read that the A65 head responds well to work on the ports because they were never built in the factory to the original design specifications. This might be part of the answer.