Head flow testing.

swooshdave said:

comnoz said:

For anyone who thinks 30 mm will not flow enough air I did a simple test. It is a 6 inch long piece of acrylic with a 30 mm hole through the center and a 1 inch radiused inlet and outlet. [nowhere near the optimum for flow]

On the flowbench it flowed 190.5 CFM at 28 inches which is enough to produce 64 horsepower per cylinder according to Superflow's formula. Do you think you need more air than that? Jim

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Stick a bend and a valve stem and crap in the middle of that tube and then see. :mrgreen:

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And that is the problem and that is why you need to enlarge the port leading up to the valve guide and bowl- so you can slow the air down so it can make the turn. Think of the bowl as a reservoir- you move the air fast down the straight port and then let it expand into the bowl . The fast moving air will pressurize the bowl when the piston stops drawing air at the bottom of the intake stroke. That pressure stops the air from exiting the cylinder as the piston starts back up on the compression stroke. Jim

Weird how people always think bigger is better! Overly large ports can be compared to a water at a constant pressure coming out of 2 hoses. The first hose is 50mm diameter, the second 25mm..........the velocity of water coming out of the 50mm hose is a lot less than the 25mm one.

Low gas speeds at the sort of rpm which nearly everyone uses when riding a bike, results in reduced torque, less power, and poor fuel economy. The bigger port will work a little better at very high engine speeds, but the bike with smaller properly designed ports will be so much easier to ride fast, that in the real world this slight advantage is likely to be meaningless.

I couldn't get a photo of an old dyno graph to show up so I did a hand drawing from the screen. This was from many years ago and was a fully ported RH4 head before and after I added a bunch of epoxie to the floor of the 33 mm port. A piece of that epoxie ended up going through the motor and making a mess.

Line B was before the filler and line A was after the filler.

The bike felt faster before the port filler because you could feel the hit as the power came on.
On the track the bike was much faster from one corner to the next with the filler. Note that the peak horsepower was almost the same. The test ended at 8000 rpm and the lines crossed at about 6000. Jim

I always cheated a bit toward the hi end side because willow springs was a very fast track. And then put in more torque with long intake manifolds.

It was a balancing act - pushing high RPM hsp up to the point where it was still usable. The ports did measure 32mm at the mounting surface but tapered down on the way in. They were offcenter - raised in relation to the intake manifold bolt holes

I always used long intake manifolds - prefering 9-1/2 to 10" from the head to the end of the stack. Longer than anyone else was running against me . From what I learned and you've (Jim C) said about primary waves & long intake manifolds - the intake maniold length makes a big difference. I understand that you can get significantly more low end with the longer runners - but they would be VERY LONG (need to lower the oil tank) for the ideal low end primary wave. The present wankel Norton roadracer uses velocity stacks that extend electronically according to the RPM. If you (Jim C) were seeing over 90 hsp on the dyno with 15" or so long intakes (from the head) then you could have the same relative increase on the low end if the velo stacks telescoped & adjusted accordingly.


This was my idea for bonniville - a hand lever to change the velocity stack length to suit the RPM. Think about it Ken Canaga.

Jim S

Variable stacks would likely help with the narrow powerband you get from using the first wave but I am not sure what the carburetion would do. My biggest problem I had was trying to get the carb to deliver fuel with a curve to match the big hump in the torque curve. If I gave it enough jet to supply fuel at the peak of the curve then the engine was plug fouling rich either side of it. Not sure how much of that was caused by double carburetion which would be helped with the variable stacks. Jim

This is guess work because its not been done but I thirnk a few auto racers have tried it and claimed that a strong low end was available with the very long stacks - probably about 17" or more from the head on a nort - down to around 15" for higher RPM. This is dyno work if anyone ever gets to it. I've tried a lot of things but not this. If it works as its supposed to it should carburate in the narrow range that the stacks are tuned for. This is just the thing I would love to try and brag about (or fail as most often happens) instead of blabbin about it but I'm sidetracked & buried now - trying to help someone manufacture my saxophone design. This and a radically welded & reshaped steep down draft port with long valves was my plan for bonneville.

Somewher on youtube is a vid of the variable length stacks on the Nort wankel.

Its been done many years ago..............David Vizard a UK tuner covered the effects of ram tuning in a book published in I think the 1970's.

The info may be available but it needs to be applied to a Norton.

Note that the diameter of the stacks would have to be smaller than the as usual oversize velocity stacks in order to be effective for the long primary wave stacks.

Be interesting to see the results of your development work in this area.

jseng1 said:

The info may be available but it needs to be applied to a Norton.

Note that the diameter of the stacks would have to be smaller than the as usual oversize velocity stacks in order to be effective for the long primary wave stacks.

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For what it's worth I just used an online calculator that you entered the intake length in a box, and it told you the RPM range that the harmonic would be in.

The dyno results matched it very well. ( On my BMW)

Generally if the intake is longer then the ID can be larger as well d/t the column of air inertia helping to slam it in against rising piston pressure wave. Here's generalized summary I hope applies to Ms Peel with too much cam for decent street use/idle. Peel will be run in on a carb on a long stalk and Drouin intake is about 18" long but 40 mm ID.

ence the power curve of the engine. The intake runner diameter influences the point at which peak power is reached while the intake runner length will influence the amount of power available at high and low RPM.

A larger diameter intake runner, relative to the diameter of the intake valve, will result in improved engine breathing at high RPM and will take peak engine power to a higher RPM but will have little low RPM power. This may be good for a modified race car or a drag car, but will not be good for a turbocharged car with a large turbocharger. For a good responsive modified street car or a rally car you would want an intake manifold runner diameter that is approximately 80% the size of the intake valve diameter on a two-valve cylinder, or the same size as the intake valve diameter on a four-valve cylinder, as this will produce better port velocity and more intake inertia. For a high performance modified race car or a drag race car you would want an intake manifold runner diameter that is approximately 90% the size of the intake valve diameter on a two-valve cylinder, or approximately 110% the size of the intake valve diameter on a four-valve cylinder.

In terms of intake manifold runner length, a longer intake runner produces better torque at low RPM, while a shorter intake runner produces better power at high PRM. Generally, an intake manifold runner that is in the region of 200-300 mm long will sustain power at high RPM but little power at low RPM while an intake manifold runner that is in the region of 300-400 mm long will start building power from low RPM but will run out of power soon after peak power is reached. But note that the intake port on the cylinder head forms part of the intake runner. Thus the intake runner length is measured from the intake valve seat to the intake runner bell mouth, and not from the end of the intake manifold.

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http://www.custom-car.us/intake/intake-manifold.aspx

Ms Peel's Combat head was put on Manney 920 cylinder by Ken and will need this oil drain put in, by Ken I hope.

Kevin Cameron of Cycle World did article "Hot Metal" discussing the heat and temperature loads and flows, especially heads. Mentions the weak hot spots between valves or valve and plug hole 'bridge' for one thing but also that larger exhaust ports ID give more surface area for heat to transfer from exhaust blast, so narrow-ish exhaust ports help avid some od the 40+% or so heat absorbed from there.

There is hi temp Al specific epoxies now and not very dangerous if it fails, just blows out the muffler. I'd like to try D shaped exhaust ports on Ms Peel. I've studied the wisdom from cozmos and seen photo's so wondering if I could DIY or best farm out to expert willing to do it righer. Exhaust flow assist is more important in boosted applications that force feed intake into low pressure. My main interest is the insulation by the epoxy and the faster speed of heat out the headers. To power for what I want Peel to do means detonation-heat excess is a lurking boogaboo.

Cameron mentions oil jets in the last paragraph but no details.

Epoxy doesnt work for long in exhaust ports, but Ti putty from ITW is fine used for inlet ports. Exhaust ports need to be welded, but on a head such as the Norton there is no real point in altering the exhaust, as this will make little difference.

I have seen and had to correct what welding does to distort crank cases so really don't want to go that route. Extra exhaust flow would just be icing on the thermal insulation cake for Peel here. I'd thought about metal splatter filling but don't know if practical or not and metal conducts heat well. Its just another straw I'm scratching at to stuff in Ms Peel's bale to make even your gross exaggerations you taunt me with on past Peel performance cause your jaw to drop at how conservative your think on what possible in push rod air cooled obsolete rubber buggy.

BTW part of Peel hay bale is all surfaces exposed to combustion are ceramic coated even behind valve ears and exit ports. Will be creeping up on mixture burn and opening up to peek in now and then before next heat raising stage. Does help a bit to keep the gases hot and thin as possible leaving the head.

Improperly carried out TIG welding will certainly result in distortion, and I would avoid anyone whose welding can distort a crankcase!

Carbon, before ya come to such blunt conclusions of welding crank case distortions, this is Ms Peel so about everything you know is wrong, including my own HARD learning curves. When 1st got Pre-Peel Combat, It ran so good I could get the leap ahead of the over cammed for road work drag only Sportster with wheelie bars in my current Avatar. But It leaked and smoked, so with online hand holding decided to just renew the basic wear parts and sent cases to DynoDave for cam bushes and line boring >>> he discovered a crack in the stress risers of square cut seats of the case mounting flange. I did not see this crack myself, as it was so fine a line it made spider cobweb silk look as thick as blunt magic marker. Dave's terrible eye sight raised my own threshold of observation eduction no end. So ground out each one pretty good then took to muffler-welding shop, with barrel mounted and room space heater to keep the whole thing fry pan oil burning hot to lessen distortions. The welder knew what he was doing, at his first cranking up the gas shielded welder, the rest of the crew on other jobs jumped up like solders manning battle stations as large and small doors shut tight and fans shut off - so not to blow the shield gas away. He melted into the cases way beyond what I could of imagined while gritting teeth. I had weld helmet on too and he'd point out 'new' cracks he found *UNder* the surface then melted beyond them to fill back up in a piled up bead. These cracks only showed up as finest dark lines in the bright melt at limit good eyes could resolve. Case distorted for almost 1/16" wavy gaps in the sealing seam. This took over a week of hours a night and most of all weekend - Pounding and Banging and Pounding and Banging ditto ditto etc. with welding sag hammer and drift to mold the seal back to almost perfect, Then another week of grinding a radius and polishing out the peck holes that were on same scale as if a tooth pick jabbed in chewing gum or putty, UGHHHHHH. Never again please.

Maybe head exht port fill in weld would not distort to matter but I'm too pensive the risk ain't worth the possible slight gain in exit flow and metal would not help the heat blast conduction I'm more concerned with in Ms Peel on 'hi' boost burning almost 3x's what stock engines can and almost half again more than elite racers. Epoxy seems way to go someday as failure just blows out on the road. Peels CHO head had factory hogged out ports too big for 750 Combat, till it hit 6800 rpm >>> then another piston worth of power came on & a few hundred rpm later valves floated with crank jump roping, front lifting and drive train dissolving. Ms Peel is only about 5 more grand short of bullet proofing top to bottom though.

I have welded up quite a few crankcases, and not had any distort yet. If you know what you are doing with this type of job, its not something thats particularly difficult to do, but lots of people dont have much of a clue and end up having big problems.

Carbonfibre said:

Epoxy doesnt work for long in exhaust ports, but Ti putty from ITW is fine used for inlet ports. Exhaust ports need to be welded, but on a head such as the Norton there is no real point in altering the exhaust, as this will make little difference.

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Check the difference between a standard Norton exhaust port and one of Jim's design and tell me that it won't make much difference. The standard Norton exhaust ports are the wrong shape and far too big as they are.

Yes it makes a pretty large difference , particularly at higher engine speeds. The hard part is you will not see much difference on a flowbench. I built a tester from a 2.5 gallon air tank with a flange welded on to fit a Norton head. I would pressurize it to 150 PSI and then open the exhaust valve with for about 200 ms with a motor and crank setup. Then I would measure the pressure drop in the tank. At high flow velocities such as you see in an actual exhaust port the differences in shape make a large difference in how much air could escape. The dyno definitely agreed. Jim

Carbon, Ms Peel cases had at least 18 inches of weld, Most of that right next to the seam. Regardless I'd rather try the epoxy first with some stakes to hold it for awhile.

How would I access having Ms Peels exht. ports configured for more exit flow?
Again not so much for extra power but for less heat and detonation proneness.