Cam followers - Andover to the rescue?

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oldmikew said:
Steve did tell me that his pushrods require in an iron barrel half the clearance of alloy . So if you want to run a 4s or other big cam then you will get a quieter motor .
Click to expand...

That’s because of the expansion difference between alloy and iron.
Both would give the same, or similar, hot clearances.
 
Fast Eddie said:
That’s because of the expansion difference between alloy and iron.
Both would give the same, or similar, hot clearances.
Click to expand...

Yes, sorry I should have said when cold . I did run mine with carbon fibre pushrods for a while - it seemed sharper than with standard alloys which makes me suspect that pushrod flex is even with a standard cam an issue.
 
one snapped... good enough for jet engines but not Nortons, must have been made from the wrong grade !
 
Excuse me if i'm being stupid here, but if we are CNC machining cam followers in the future, couldn't this be the best opportunity to make some changes.

For example i was surprised to learn the new AN ones were slightly heavier than stock - you could easily machine a bigger pocket in the centre (like Gus Kuhn and Paul Dunstall were doing back in the day) and have a follower that is significantly lighter than the stock one.

You could also use this as a chance to drill holes in the bottom of the follower so that significantly more oil would be introduced into the mix - surely significantly helping with the wear issue.


I know radiused followers and roller followers are out of the running, as you wouldn't be able to use the thousands of cams that are out there, but surely there are some other, more sympathetic mods that could be made which would be advantageous?

We've got some clever engineering minds here, with hundreds of years of experience - and that's just the Jims!
 
oldmikew said:
Steve did tell me that his pushrods require in an iron barrel half the clearance of alloy . So if you want to run a 4s or other big cam then you will get a quieter motor .
Click to expand...

Even cutting the clearance in half the steel pushrods still make a little more noise in the spintron using cams spec'ed for .006 clearance.

I doubt you would notice the difference when in the motor.

Running the PW3 with .006 clearance and steel rods didn't make a difference that I noticed.
Of course hearing protection was needed just to enter the building with that cam at speed.
I would have had to use a Db meter.
 
gtiller said:
Excuse me if i'm being stupid here, but if we are CNC machining cam followers in the future, couldn't this be the best opportunity to make some changes.

For example i was surprised to learn the new AN ones were slightly heavier than stock - you could easily machine a bigger pocket in the centre (like Gus Kuhn and Paul Dunstall were doing back in the day) and have a follower that is significantly lighter than the stock one.

You could also use this as a chance to drill holes in the bottom of the follower so that significantly more oil would be introduced into the mix - surely significantly helping with the wear issue.


I know radiused followers and roller followers are out of the running, as you wouldn't be able to use the thousands of cams that are out there, but surely there are some other, more sympathetic mods that could be made which would be advantageous?

We've got some clever engineering minds here, with hundreds of years of experience - and that's just the Jims!
Click to expand...

Agreed -except for the oiling part. The tiny dribble of overheated oil coming down from the exhaust side of the head is useless for lubing the cam. It's best to just lube the lifter bores with it and then get rid of it -like the original followers do.

The cam is mainly lubed by the oil coming from the rod side clearances.
 
If you had a good used cam would you want to use new followers with it? Or back to front would you put in a new cam and keep used followers because they "look good"?
I ask this because AN is selling spares and would they want to be in the position of saying "all new cams require a set of new followers" ?
 
Onder said:
If you had a good used cam would you want to use new followers with it? Or back to front would you put in a new cam and keep used followers because they "look good"?
I ask this because AN is selling spares and would they want to be in the position of saying "all new cams require a set of new followers" ?
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Here is what I do.

With a new cam I would always use either new or reground followers. I would not want to be required to use new followers but a fresh follower surface is necessary.

If I had to buy a specific set of followers to use with a specific cam -I would not be interested.

Once a cam is used it is best to keep the cam and followers together as they do wear in to each other.
But if the cam is in excellent used condition I have run them with a new or reground set of followers many times successfully.

I would never regrind a follower and then put it back on the same cam without regrinding the cam also.

If the cam has any ridges, pitting or obvious wear, then installing it with new or reground followers will usually cause failure shortly thereafter.
 
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gtiller said:
Excuse me if i'm being stupid here, but if we are CNC machining cam followers in the future, couldn't this be the best opportunity to make some changes.

For example i was surprised to learn the new AN ones were slightly heavier than stock - you could easily machine a bigger pocket in the centre (like Gus Kuhn and Paul Dunstall were doing back in the day) and have a follower that is significantly lighter than the stock one.

You could also use this as a chance to drill holes in the bottom of the follower so that significantly more oil would be introduced into the mix - surely significantly helping with the wear issue.


I know radiused followers and roller followers are out of the running, as you wouldn't be able to use the thousands of cams that are out there, but surely there are some other, more sympathetic mods that could be made which would be advantageous?

We've got some clever engineering minds here, with hundreds of years of experience - and that's just the Jims!
Click to expand...


Steady on old chap. Over excited use of common sense is generally frowned upon around here...;)
 
The stock lifter design is overweight and uses flat pads. They are always going to be a problem. But they are good for lots of discussion.

Thin lightweight D shaped steel tubes with attached ends??? - dream on.
 
Once they are not a problem they can easily be made lighter, and with a small change much lighter - easily done, the flat face can be radiused, again easily done.

Despite all the discussion in years past, I did not think this was going to be easy, unlike the metallurgists in the USA and Europe who are now scratching their heads.

Sometimes it is hard to re-invent the wheel, a lot of lost knowledge. The unwillingness by many companies not to try things does not help either.

It all takes time, but will happen.
 
Why do flat tappets in automotive seem to go the distance ?

I don't recall a solid lifter being made of anything special, be it a SB Ford V8 or Ford Cortina.
Perhaps part of the problem is no crown and cannot rotate.
 
small block chevys were VERY WELL known to loose cams and lifters.

Time Warp said:
Why do flat tappets in automotive seem to go the distance ?

I don't recall a solid lifter being made of anything special, be it a SB Ford V8 or Ford Cortina.
Perhaps part of the problem is no crown and cannot rotate.
Click to expand...
 
Time Warp said:
Why do flat tappets in automotive seem to go the distance ?

I don't recall a solid lifter being made of anything special, be it a SB Ford V8 or Ford Cortina.
Perhaps part of the problem is no crown and cannot rotate.
Click to expand...

A rotating tappet is halfway to a roller tappet. Partial rolling and partial sliding contact makes them more durable.

Chevy and other auto engines didn't have a big problem with failures until the oil formulas were changed to make them more friendly to the emissions equipment. That is what forced the move to roller tappets.
 
worntorn said:
Found this old gem in some Norton Tuning notes

( snip)
Click to expand...

That sounds as if it was written by John Hudson. I know because he told me the same thing very forcefully when we were putting together parts for my Production Racer in the Exp. Shop in the factory at Wolverhampton. He needn't have bothered; John Baker (builder/tuner of the D. Rawlings sprint bikes) built my engine and he already had decided to recommend the "S" cam. It's run for years, no problem, and has proven to give strong, smooth power.
 
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