inlet sleeves

I've come across a nice piece of pipe 32o.d.x28i.d. and thought this could be used to sleeve my inlets that are 33mm.
I'm looking for advice from those who have done this,
will the pipe be ok as it's steel?
will the difference of 1mm between the pipe and the inlet bore create a problem when it's in the inlet tract?
does anyone have any pictures of such a device, or designs to copy? I read on here that some of the old Dommies came with removable sleeves.
My instinct says to use an inlet gasket as a template and make a steel plate then weld the pipe to it so when it's bolted up it's pretty solid in the inlet, I'm sure some of you have tried this, is it even worth the effort?

cheers Paul.

Having just phoned a friend who has two sleeves as fitted to 650ss heads in the factory at one time. He thinks they were fitted to increase acceleration. The sleeves are split and in a spring steel and were simply pressed into the inlet ports..they were not going anywhere as the valve guide area was in the way. I have always believed they were fitted to increase gas speed into the combustion chamber and increase overall performance but what do I know....... I do know 650SS heads with original 28mm bore inlets are rare as most clever sould bored them out to 32mm over the decades and a 500 or 650 does not need 32mm inlets ......in my opinion that is although I do have some flow test results for a 650SS head big valved and big ported. The lump still sits in my loft unused after 40 years.....but I had it done BEFORE i read the books......
Might be worth looking in ' Performance Tuning in Theory and Practice ' ( A.G. Bell )( ISBN 0-85429 275 6 ) to see what he says regarding port sizes etc for your size of engine before going further.....

If this is a 750 you will probably find a nice increase in power on the street. Steel will work fine but I would taper the outlet a bit to reduce the step. I have installed quite a few sleeves over the years in heads that someone had gotten carried away with in there porting efforts. I have used aluminum that I shaped in the lathe and JB welded them in.

As a matter of fact -my EFI streetbike has sleeves in the intake ports. It was the test pig for the Fullauto intake port and I had a pile of different shaped sleeves that I tried. Jim

brxpb said:

I've come across a nice piece of pipe 32o.d.x28i.d. and thought this could be used to sleeve my inlets that are 33mm.
I'm looking for advice from those who have done this,
will the pipe be ok as it's steel?
will the difference of 1mm between the pipe and the inlet bore create a problem when it's in the inlet tract?
does anyone have any pictures of such a device, or designs to copy? I read on here that some of the old Dommies came with removable sleeves.
My instinct says to use an inlet gasket as a template and make a steel plate then weld the pipe to it so when it's bolted up it's pretty solid in the inlet, I'm sure some of you have tried this, is it even worth the effort?

cheers Paul.

Click to expand...

Thanks for the replies, I know it's not a common subject, Jim, I don't suppose you have a photo to hand do you?

I made an insert today which is simple to do, but I have two questions to those in the know, how close should I go upto the short side radius, and should I taper the insert out or radius it at the valve end of the tube, what would work best?
Thanks in advance
Paul.

Why did Nortons stop fitting these inserts into the inlet ports then ??

Later 650's didn't get them, nor the Atlas ?
The early 650's would have had the std cam, not the sports SS cam too ?

Anyone got dyno charts to demonstrate where the improvement was if the sleeves were fitted ?

Well Rohan I'll tell youif it's worth bothering in a week or two, I only got to pull them out and chuck em if they're no good, do you know the answer to my query?
It was results of the 28mm heads in Jim's testing that got me curious.

How are you going to test it though.
Seat of the pants, or dyno charts ?

The FACTORY hotrod 850 that Norton Villiers had in 1973 - the Rawlins Baker effort
- had big ports all around, and went like snot. A 142 mph Roadster, and quite streetable.
I can't help thinking this small port thinking is a different evolutionary path.

But those dyno charts might be interesting, its often said there is more than one way to skin a cat.