1.56" Intake Valves With Web 312a Cam & 4" Radius Followers

motorson said:
I have that combo in my bike with no modification of the intake valve. It seemed to lack torque down low so I mentioned that to Jim and he recommended advancing the cam 5 degrees. (Info in the INOA manual) Now it pulls real hard from about 2500 rpm. It will pull from 2000 but pulls hard from 2500. Mine runs out of breath at about 5500 and makes maximum HP at 5300. (42 rear wheel HP on the dyno)
Click to expand...
My cam sprocket has two more keyways broached into it at random positions. When I fitted the two into one exhaust pipe I tried advancing the cam, and ended up with the cam 12 degrees ahead of standard. My motor pulls like a train. Somebody else on this forum also mentioned that advancing a standard cam gives much more torque.
It stands to reason, that when Norton were building a road bike with that cam, they would set it to operate a bit milder than what is possible.
If your motor runs out of breath at 5,500 RPM, it is probably due to the exhaust being a bit restrictive. My motor pulls hard right through the usable rev range and straight through the top. I am always in danger of over-revving it. The tail pipe on my 2 into 1 exhaust has a cross-sectional area, the same as the sum of that of the two header pipes.
 
Last edited:
Many owners say their bikes pull like a train. I see that on other sites too.
Some will even say that their bike pulls like a freight train, which I think is intended to mean the bike is extra powerful.
I had a hunch my 850 accelerates faster than a freight train and it turns out that is correct. Even the BSA will accelerate faster than pretty much any kind of train, 0-60. I guess a bullet train would leave it behind for top end. But even those aren't terribly impressive for acceleration figures.
But pull like a freight train?
0-60mph in 15 minutes? We need to aim higher.
Trains can't even do hills, 2 degrees slope is max climb. A train wouldn't even register on dyno hill.

Glen
 
Last edited:
worntorn said:
Many owners say their bikes pull like a train. I see that on other sites too.
Some will even say that their bike pulls like a freight train, which I think is intended to mean the bike is extra powerful.
I had a hunch my 850 accelerates faster than a freight train and it turns out that is correct. Even the BSA will accelerate faster than pretty much any kind of train, 0-60. I guess a bullet train would leave it behind for top end. But even those aren't terribly impressive for acceleration figures.
But pull like a freight train?
0-60mph in 15 minutes? We need to aim higher.
Trains can't even do hills, 2 degrees slope is max climb. A train wouldn't even register on dyno hill.

Glen
Click to expand...

I don't know about you, but when I say my bike "pulls like a train" I'm referring to one of these

1.56" Intake Valves With Web 312a Cam & 4" Radius Followers
 
I think when people refer to pulling like a freight train they're talking about torque. In that case it's hard to beat a freight train for torque.
 
Got em beat with the BSA.
It only has about 30 ft lbs but even with me on it that is 1 ft lb moving just 23 lbs.
A poor old coal train has only 1 ft lb torque to move 566 lbs.
If I had a coal train I would be sending the heads to Jim Comstock asap.

Glen
 
worntorn said:
Got em beat with the BSA.
It only has about 30 ft lbs but even with me on it that is 1 ft lb moving just 23 lbs.
A poor old coal train has only 1 ft lb torque to move 566 lbs.
If I had a coal train I would be sending the heads to Jim Comstock asap.

Glen
Click to expand...
1.56" Intake Valves With Web 312a Cam & 4" Radius Followers
 





This one starts at 4:01, gets right to the good stuff.
 
worntorn said:
Got em beat with the BSA.
It only has about 30 ft lbs but even with me on it that is 1 ft lb moving just 23 lbs.
A poor old coal train has only 1 ft lb torque to move 566 lbs.
If I had a coal train I would be sending the heads to Jim Comstock asap.

Glen
Click to expand...
Might work if you have a Deltic or similar as prime mover, but steam or electric, I don't imagine Jim's magic has a lot to offer....
 
Good point.
Why do people brag that it "corners like it's on rails?"

I go pretty fast thru the Fraser Canyon corners on the Norton.
The trains go way slower and they keep ending up in the river. Seems "corners like it's on rails" isn't very good at all.
I haven't ever gone in the river on the Norton (yet)

Glen
 
Dan1950 said:
After some input from fellow forum members familiar with this set-up and an email conversation with Jim Comstock it seems like valve clash will not be an issue running this combination.

Now I need to find a competent machinist that can do the work before spring of 2023.

Not looking for extensive porting, just open up the bowls a little and clean up the area around the guides.

Any suggestions on someone stateside that can do the work?
Click to expand...
Contact Lief Lewis 805-272-8417
 
worntorn said:
Good point.
Why do people brag that it "corners like it's on rails?"

I go pretty fast thru the Fraser Canyon corners on the Norton.
The trains go way slower and they keep ending up in the river. Seems "corners like it's on rails" isn't very good at all.
I haven't ever gone in the river on the Norton (yet)

Glen
Click to expand...
A roller coaster.
 
worntorn said:
Good point.
Why do people brag that it "corners like it's on rails?"

I go pretty fast thru the Fraser Canyon corners on the Norton.
The trains go way slower and they keep ending up in the river. Seems "corners like it's on rails" isn't very good at all.
I haven't ever gone in the river on the Norton (yet)

Glen
Click to expand...
Rails have no give, they are precise. Now imagine a 1973 Cadillac going around a tight corner. All over the place.
 
I can outrun the old Caddies too but they seem to mostly stay out of the river.
I'm sure the Engineer on this train was grinning and saying " She's cornering like she's on rails" just before the big sploosh.
I don't want to come across as down on trains, they are a great invention.
I'm just saying we need a new analogy to represent great acceleration and terrific handling.
I'm not sure where this train thing came from, but I'm sure Al has written at least 500 times now that his 850 pulls like a freight train. I might be guilty of making that claim a time or two as well before looking up freight train 0-60 and freight train 1/4 mile et.

The next thing will be someone bragging that their bike has modified very powerful brakes and now it " stops like a freight train!"
Thinking about it, that analogy does fit a couple of bikes I've owned.

Glen
Screenshot_20220902-180755.png
 
Last edited:
Much better than the freight train thing.
If I had a freight train I would avoid racing you.

Glen
 
You must log in or register to reply here.

Similar threads

acadian
A65 head modifications
Replies
6
Views
1,057
Matt Spencer
M
Dan1950
  • Locked
Bigger Valves for the RH 10 Head?
2 3 4
Replies
71
Views
4,040
gortnipper
gortnipper
jseng1
  • Locked
Setting up valve clash clearance with race cams and big valves
Replies
4
Views
1,674
jseng1
jseng1
jseng1
  • Locked
Narley High HP ports made easier
Replies
10
Views
2,321
jseng1
jseng1
jseng1
  • Locked
Narley ports for High HP Nort roadracer.
2
Replies
38
Views
4,901
Doug MacRae
Doug MacRae
Back
Top