Full aouto head
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norton73 said:
comnoz said: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.
Flow
Velocity
trident sam
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norton73 said:
That would be easy for me.
The only head I couldn't sneak past my missus would be George Clooneys :shock:
norton73 said:
That would be interesting on the short stroke...
Comparing my Maney stage II porting to the Fullauto with Comnoz porting on the dyno.
The stage II 750 now has 72 Rear wheel Hp unfortunately just 3 runs on dyno as ignition broke down so didn't get to set advance and the right jetting
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With fitting the head to a short stroke motor, it is not simply a matter of one plus one equals two. If the head is designed to give max in a rev-range from 4 to 7, you might not get the result you might expect when you run it at much higher revs - the inlet ports might need to be larger, then other things change. From long-stroke to short-stroke, the mindset is different.
acotrel said:
It has been shown a lot of times from tuners that there are different ways to go to flow a head. Both smaller valves or with larger valves port size and flow/ velocity. Axtell got som great figure with his std valve size. However the porting in respect to some areas should always be similar except for size of the port depending on carburetor bore size valve size and bowl area.
The full auto head will be thoroughly evaluated in regards to short stroke power band, cams, bore size and maybe even I would keep smaller size of valves as this might actually be beneficial. The Maney stage II is a good port job that can be done better but still the 750 short stroke with that head leaves 72 rear wheel Hp without any mods from my std setting 28 deg advance and 300 main jets . It will be interesting to see what the full auto with much better port geometry and matched combustion chamber would do on the dyno with the same bottom end, carbs and exhaust.
Fast Eddie
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Swetune said:
Indeed that will be VERY interesting to see the effect of the FA head with all other parameters remaining the same.
I did that with the Comnoz head job on my RH10 head and was staggered to see a 9bhp gain and much healthier curve everywhere from 3000rpm onwards.
Please keep us all posted.
Brooking 850
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Nigel, what was the end output of your RH10 head and did Jim put in oversize Vv's?
Regards mike
Regards mike
Fast Eddie
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Brooking 850 said:
Details are in this thread Mike: engine-build-prep-t18461-165.html?hilit=Cylinder%20head%20testing%20Dyno
'Befroe' spec of bike was: JS1 cam/ follower/ spring kit, JS rods and pistons at 10.5:1 CR, nice squish (forget exact measurment), 35mm FCRs, cNw manaiflod, Tri spark, cNw coils and leads. Standard RH10 head and valves.
'After' spec is: as above plus, followers ground to 7/8th radius instead of 1 1/8, 3mm OS re-angled inlet valves, 1.5mm OS exhaust valves, Comnoz port job, Comnoz valve springs.
Actual peak figure was 64.6bhp @ 6300 rpm, with a very flat power graph from 6000 to 7000.
There was significantly more power from 3000 upwards.
I was very surprised by this to be frank, the improvement way exceeded my expectations.
N
nortonspeed
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Fast Eddie said:
The factory short stroke 750 engine with RH7 head and Omega domed high compression pistons is a perfect match regarding the shape of the combustion chamber hemisphere (without squish band). As a matter of fact the shape of the RH7 head hemisphere in combination with the domed pistons work like squish. Using the Full Auto head (or any other Commando head with a squish band) in combination with Omega shaped piston heads will not work because the gasses will be trapped in the outer space between hemishere and domed part of the piston. So this combination will either need machining the head (reshape the squish band) or another shaped piston head so that the gasses will be squished towards the centre in stead of (partly) getting trapped :!:
Fast Eddie
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grandpaul said:
Don't know about roller lifters.
Remember we are talking JS1 cam kit here, therefore BSA lifters.
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Fast Eddie said:
Can't prove it now because it's gone! But that is somewhere on a par with my 750 short stroke with standard Fullauto, standard valves and a PW3, 34mm Mikunis, separate exhausts. It showed around 60 at 6500, but the motor was fresh so it wasn't revved any higher and there was up to another 1000rpm to peak power and then some more rpm to be had! So maybe what we lost on the head we gained on the cam, who knows.
I have only run it once with it's Webcam 86c and assymetric ground followers. Haven't been to the dyno, but at Cadwell it 'felt' strong in the mid range but ran out at lower rpm than I expected.
Of course neither the gearing nor jetting hadn't been optimised for the changes, no time to do that before the belt drive failed!
Lets see if I like it with the cam retarded a little next week! But road circuits are new to me so to be honest, just getting round will be enough for that weekend.
To be honest I have the impression that the standard Fullauto set up works well with a short stroke and I don't see me big valving it. For one at 63 and retired I am not likely to ride enough to ever do it justice!
I did have an original fully hemisphered short stroke big valve head with matching Omega pistons in the '70s, ex Thruxton cam, but that was built into an 850 and ran on 36mms with 34mm ports! Still pulled like a train in the mid range, but topped at 6800rpm, it was definitely faster than I was, and I was 40 years younger.
Fitted in the same frame however!
Fast Eddie said:
F Eddie thats what I´m getting at. If the FA head is a good bolt on it would be interesting to compare on the dyno withste stage II Maney. I´ve been looking at the II a lot and it looks good but the Hp of my engine does not entirely come from the port job. The pistons are flat CR about 10.5 or 11:1 and it has been welded in the combustion chamber and to my experience on a lot of similar welding it results in at least 5-10 Hp with a correct matched exhaust.
I´ve run my bike in the Nordic Championship this year and although It was a a couple of years ago I raced and Im not a top driver the machine leaves Ducati 900 and Triples behind on the straight.
I would however like to have a port job on the FA head and probably the same valve size as Steve stage II but i´m thinking on steeper valve angles which would help valve geometry and maybe actually fill up between the valves to get a flatter combustion chamber. Reangling the port as well similarly would help flow into the head.
Done it for test on a RH4 head which is now getting welded together for completion.
Nortonspeed your comment is spot on. There will be no squish if you don't use correct dome for correct combustion chamber. But you could use flat squish and complement with angle squish on the dome just as long as you don't trap gas cause that could actually cause it to detonate in the pocket.
Problem in using flat pistons you loose compression but with domed you have to be very careful getting it correct and still have an ok flame travel.
You will see that if you may keepi the advance low and not loose power. That´s the receipt of a good combustion. Compare 4 valve chamber or 5 valve or other more modern engines
Problem in using flat pistons you loose compression but with domed you have to be very careful getting it correct and still have an ok flame travel.
You will see that if you may keepi the advance low and not loose power. That´s the receipt of a good combustion. Compare 4 valve chamber or 5 valve or other more modern engines
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