Head flow testing.

You mean 3.50393700787402 INCHES . :mrgreen:

It really doesn't matter what size the engine is. The port size needs to be matched to the valve size and flow ability.
A 1.5 inch Norton intake valve will flow enough to create good velocity in a 30mm port.

Of course a stock 30 mm port will not support this velocity . Jim

Got enough data yet Jim?

Ok Jim that helps my concepts on flow equation side but I'm conflicted/confused on heat flow side with sustained boost. Two-3 dilemmas I'm trying to balance that I'd love your thots on. No. one is finances that's my doing. Other ones'; who in their right mind would want to run around with dynamite boost blasts just to commute and torque about some here and there on-off road sanely on 87 octane and preserve expensive tires. Plus the heavy TTI Drouin needs is like lugging big ass battery only needed to start on.

So what valve size for 10:5 CR, hog nostril CHO, Norris D drag cam with just single 34mm Miki carb to tame its starting, idle and off idle lug response?
Would the smaller valve tend to spray in more turbulent mix at low rpm draw in's with the set ups 7,7-ish dynamic CR late intake closing? Not interested in much extra power unblown just decent big block normalish Cdo power band to 70's rwhp w/o detonation on 87 octane. Restricting flow packing in higher rpm might be a boon compromise to actually live with in real life.

OR what valve size with 50+% more still burning mix heat blown past exht valve to dissipate thru seat and guide and not glow plug pre ignite or detonate? Heat flow is Peels main limiter when boosted though head defects.
Main concern is not the unblown performance beyond easy use spunky behavior > But the rare deadly serious sustained boost heat tolerance where the octane allows full pressure max burn spark timing for minutes at a time.

If turns out a non issue then for sure could afford bigger valves and get best of both worlds.

With a blower the valve or port size is not so important. You can get enough air to blow a Norton to kingdom come with stock sizes.

With a D cam and 7-1 compression- low speed performance is going to be non-existant. I will build no cylinder pressure without boost and with that much overlap any low speed boost is going to blow right through.

So the centrifugal supercharger will start about 4000 and the cam will tune at about 5000. From there to boom will happen pretty fast. Jim

hehehe JIm, being its for hobot's Ms Peel your description - prediction is music to my ears and exactly what I hope for unboosted, a pussy cat down low that will roar decently over 4000 to redline. When Peel in prime with std head I was often about to or was spinning out on slow sharp Gravel turns until 120 tire fitted with lowish pressure. On THE G what little throttle seems fine can suddenly>YIKES. The snap backs though are addictive hook up self saves.

If for some reason wanted to launch w/o Drouin from a stand still or just creeping, I know how to rev up and feather or drop clutch in lower gears. I may get the best of both worlds with just some easy switch outs to enjoy either. The slight other benefit of the small valves would be rpm tolerance on boost which may have to be reached into lower gears to dice it up with the elites Peel's got in her sights that wheelie too easy to put down the Pow of Peel with tucked low front. I can not think about decent power bands w/o translating into actual use, especially leaned to disappearing traction, front or rear or both. I will be pleased if blower fill in eliminates much engine drag on let offs. BTW Powerarc has rev limiter as i've 2 Nortons that human hand not fast enough to back off in time.

Matt Spencer said:

You mean 3.50393700787402 INCHES .

Click to expand...

The question here perhaps should be
- did Norton make the stroke at precisely the 89 mm or the 3.503 inches quoted in the workshop manual ?

Don't forget to add in the +/- .25mm depending on who was running the machine and if they had a hangover that day.

Maybe the question is did the machinery operate / measure in inches or mm ??
And someone did the conversions after ....

comnoz said:

It really doesn't matter what size the engine is. The port size needs to be matched to the valve size and flow ability.
A 1.5 inch Norton intake valve will flow enough to create good velocity in a 30mm port.

Of course a stock 30 mm port will not support this velocity . Jim

Click to expand...

That statement could have come from the 'Riddler in a Batman episode. :lol:
On a stock (RH1) 750 (with attention to detail on assembly) there could be a 'driveability improvement with porting ?
2000 to 6000 RPM ?

Time Warp said:

comnoz said:

It really doesn't matter what size the engine is. The port size needs to be matched to the valve size and flow ability.
A 1.5 inch Norton intake valve will flow enough to create good velocity in a 30mm port.

Of course a stock 30 mm port will not support this velocity . Jim

Click to expand...

That statement could have come from the 'Riddler in a Batman episode. :lol:
On a stock (RH1) 750 (with attention to detail on assembly) there could be a 'driveability improvement with porting ?
2000 to 6000 RPM ?

Click to expand...

Sure, widen the port about 1-1.5mm at the guide and blend it to the seat. Deepen the bowl a bit but watch out for the spring seat. Don't do anything in the straight section between the guide and the carb.

You can't do much with the short side radius without adding material but you might want to knock off any square corners there. Jim

I replaced my "C" head with an RH1
The C head had bad guide geometry and was generally rough and was/is not worth reviving. I found the RH1 with what seemed to be factory fresh seats and the exhaust thread were perfect. The bad part is that quides were the old atlas type that did not take seals.

I sent it to Jim to take care of the guides and seat the valves. When it returned, I machined .040 off the face and lightly shaped the intake ports to match the 32mm carb adaptors only going 1/2 to 3/4 of an inch in.

The performance of this head is fantastic. I really believe it is an improvement and the integrity certainly is better.

I did something right today. I finished up the porting on an rh10 head that I was building for a short-stroke racer. I pretty much did my normal port work with a 3mm oversized intake valve with one difference. I recently had a custom cutter made to change the shape of the seat down where it meets the aluminum in the port. The intake runner is still 30mm and just lightly cleaned up.
I had to go over the calibrations on my flowbench to make sure it wasn't lying. Here is the intake flow graph in comparison to a big valve Fullauto head that I did recently. The green line is the Fullauto head and the blue line is the RH10.



It took a lot more time to get the rh10 head to flow like this than it did for the Fullauto head but this puts the rh10 head among the best I have tested. The velocity is down slightly in comparison to the Fullauto but not bod.

Now I have to try the new cutter in a Fullauto head. Jim

Now you went and did it Jim. You can use mine if you're really curious.
Bill G

Bill G said:

Now you went and did it Jim. You can use mine if you're really curious.
Bill G

Click to expand...

That was the plan.

Jim, with the modifications you have done to this head, what would your expectations be for power output thru the range? Will it be better than stock most everywhere or just near the top rpm?
Here I am thinking the rest of the hypothetical motor would be stock except bumped compression with one of the JS thin head gaskets that should give about 9.5 to one.

Glen

worntorn said:

Jim, with the modifications you have done to this head, what would your expectations be for power output thru the range? Will it be better than stock most everywhere or just near the top rpm?
Here I am thinking the rest of the hypothetical motor would be stock except bumped compression with one of the JS thin head gaskets that should give about 9.5 to one.

Glen

Click to expand...

Hi Glen,
I'd advise careful measuring of everything that you have before making firm plans around CR.
My 850 was actually only 8:1 NOT 8.5:1.
According to my calculations, if I used the 3 thou rings and even left out the base gasket, I'd still only achieve 9:1.
Hence I went the high chomp piston route.
Just my own experience.

worntorn said:

Jim, with the modifications you have done to this head, what would your expectations be for power output thru the range? Will it be better than stock most everywhere or just near the top rpm?
Here I am thinking the rest of the hypothetical motor would be stock except bumped compression with one of the JS thin head gaskets that should give about 9.5 to one.

Glen

Click to expand...

Glen,
As long as you don't change the cam or the intake tract diameter, then the RPM range will not change with the big valve conversion. It will make more power from the torque peak up. Jim

Bigger valves only help power if valve size is the limiting factor to intake flow. On other hand should not hurt anything but 'high' rpm d/t extra valve mass and less heat area transfer of seat rim per valve volume. Ever hear anything about heat factor limits in famous hot shot Nortons? If cam profile closes intake valve late [plus exht. valve open too] then engine acts like low dynamic CR lazy dog down low that don't need much octane either. Bigger valves would tend to give less mix spritzing turbulence down low also, sort of like blowing thru a pinched drinking straw same volume over time as a more open water hose. A static CR of 9:1 may only be 7:1 with a race cam shorting compression stroke length down. Long stroke engines like Norton's, slow the piston to linger longer near TDC with valve over lap which also tends to lower the draw in [suction pulse] pressure difference to fill and stir.



Can not discuss much but generalities w/o the full combo of CR, valve size, porting, cam profile + stroke and rod ratio with octane available for spark time setting and weight of craft with gearing and type of use intended. Can't ignore the induction system and the exhaust system either - as I found out in spades, can wake up a boggy engine like putting a fire cracker under a sleeping big dog. So ya'll please continue experimenting on your dime for the rest of us to learn from.

https://www.google.com/search?q=comress ... &source=hp

https://www.google.com/search?q=comress ... 3Aofficial

Bill G said:

Now you went and did it Jim. You can use mine if you're really curious.
Bill G

Click to expand...

OK Bill, you will like this.

Here is your big valve Fullauto head as it was -the lowest violet line.

The RH10 is just over it with the light blue line.

The green line is the big valve Fullauto with the new cut in the bowl and some hand work to blend it in. It gained a lot of high lift flow but lost some at lower lifts.

The blue line is after a small back cut on the valve. The bar has been raised.