valves

I've been told, correctly or incorrectly, that with the old leaded gasoline there was a tiny lead buildup which was soft enough to form a complete seal at each closing. That prevented valve blow by and burned valves.

With the unleaded fuels of today, or propane, listen to what these fellows "in the know" have to say about rotators.

When I worked for an LPG dealer, we always had rotators installed anytime a valve job was done. Well if they weren't already in place that is.

There is the Rotocap type, where the valve uses special keepers shaped like "C's", along with a Rotocap- a hardened steel cup that fits on the top of the valve stem. The action of this is when the rocker arm presses down on the Rotocap, the keeper is released by a few thousandths of an inch, allowing the valve to rotate a fraction of a turn.

The other type of rotator is the "positive type", where there are little ramps and springs in the valve spring retainer that rotate the valve a little each time the spring is depressed, also.

The purpose of either system is to rotate the valve to make it wear evenly, prevent "hot spots", and this action probably helps keep particles and buildup from lingering on the seat, which could cause the valve to burn.

As to your question, you make no mention of the type of engine you are ordering a kit for, which would preclude any guess as to whether your engine has rotators or not. You will have to disassemble it and check for yourself.

In some cases, engines that did not use rotators from the factory could possibly have been changed over during a previous rebuild.

If you are getting a complete valve kit, with valves, retainers, keepers, and possibly rotators you may be given the choice of either kit... rotators or not, and it would be your choice, depending on cost, but if you are just buying the valves, you will need to verify which you already have, to match the parts up correctly.

Are you doing the work yourself, or do you have a machinest lined up... he could probably tell with one glance what you need.

Some valves rotate by the fore and aft position of the lifter against the cam and others use a mechanical 'rotator' up near the tip of the valve where the retainer is.

This is what they are asking you....Does the valve use a mechanical rotator or is it just a plain valve, spring and it's keepers riding via the push rod down to the lifter which in turn is actually doing the rotating.

I know that sounds clear as mud.

Look down the lifter bore...if the lobe of the cam seems to be off-set (front to back) to the lifter bore, then you probably don't have a mechanical rotator. The cam lobe is 'turning' or 'spinning' that lifter as it lifts it.

However, if the lobe of the cam seems to be directly in line with the lifter bore, chances are the engine uses a mechanical rotator.

Boy!! That is hard to explain!!

The valve has got to rotate either way; if it always landed in the same position, it would soon become out of shape and burn.

Well, I tried,

Allan

Yes, you are correct. Thanks for bailing me out on that one..... whew!!! :>)

Allan