Camshaft Regrind

[Tom R]

Anyone know the minimum base circle you can run on 16v cams before you start running into geometry issues?
I have a couple of stock cams that are beat up on the nose a bit. Delta Cam in Tacoma can match the existing profile to the damaged lobes.
I’m wondering if they can reduce the base circle an additional 30 or 40 thousandths while they’re at it.

[GregT]

I remember Rapid Ray covering this some time back. Possibly a search may turn it up.
Alternatively - how bad are they ? Pretty well all cam grinders use a Eutectic overlay which work hardens once in place. I've had pitted and scored cams repaired by this method with no probs.
The cam followers can be built up with it too. Worth having a look to see what they look like as well.

[zed1015]

To restore the original cam profile the base circle will have to be ground in relation to the existing lobe height lost during grinding anyway to maintain the original lift figures.
Unless you are looking to gain lift it's pointless having the base circle reduced more than is needed.
If you are looking for more lift the usual method is to build up the lobe with weld and re grind whilst maintaining the original base circle specs.
This avoids issues with rocker adjustment limits and valves stem heights etc..

[Tom R]

I’ll search for Ray’s post.
The nose of two lobes on the exhaust cam is nicked up. It’s not terrible and the rocker wasn’t too beat up that I can remember…. It’s been a dozen years since I replaced all that. I’m trying to find the old rockers for Delta to hard face, but haven’t tracked them down yet. I couldn’t imagine I’d be dumb enough too throw them out.

The way I’m understanding it, they can remove enough off the nose to clean it up and still match the existing profile by removing material from the base circle as well.

I am wondering if they could then introduce an extra lift by removing additional material from just the base circle?
Or does that alter the profile in a negative way?

They also do hardweld repairs for additional cost…

[zed1015]

If they offer lobe build up, regrind and hardface ( as any respectable cam grinders should ) then you should go for that option, especially if you want to retain the stock profile.
Reducing the base circle won't alter the lobe profile but just increase lift although if you want extra lift that is noticable you may as well have all the lobes built up and reground and retain the stock base circle as this won't effect the adjusment parameters of the rockers etc.
A reduced base circle is usually only employed to allow a very high lift to be used ( as in drag racing ) where it isn't feasable with the stock base circle due to clearance issues between the lobe and head or cam cover and there is an insufficient thickness of material that can be removed to clear the lobe without breaking through the outer surface of the castings..
Also if you have a non stock grind you will likely have to fit slotted cam sprockets and degree them in for correct timing.

[Tom R]

They do offer lobe build up, but it starts getting ip there in cost.
My thoughts were to have them clean up what’s necessary on the exhaust cam’s nose, then grind additional base circle to make them more like gs1150 cams; which I believe are same duration as the early 1100 cams with an additional 0.040 valve lift.
taking rocker ratio into account…. That’d be about 0.030 off intake cam base circle and 0.040 off the exhaust when all’s said and done.

I’m wondering if taking that much off the base circle would cause problems with the rocker / valve geometry.
I know they sell longer tappet screws.
Or maybe there’s something I’m not thinking of.

I already have adjustable sprockets on the current cams I’m running set at 105/107.
The ones I want to repair have been sitting in a drawer for a dozen years and I was looking to do something useful with them.
My bike has 50k in it now and I’m planning a new top end in the near future, nothing extraordinary… just an upgrade.

[Blower]

They do offer lobe build up, but it starts getting ip there in cost.
My thoughts were to have them clean up what’s necessary on the exhaust cam’s nose, then grind additional base circle to make them more like gs1150 cams; which I believe are same duration as the early 1100 cams with an additional 0.040 valve lift.
taking rocker ratio into account…. That’d be about 0.030 off intake cam base circle and 0.040 off the exhaust when all’s said and done.

I’m wondering if taking that much off the base circle would cause problems with the rocker / valve geometry.
I know they sell longer tappet screws.
Or maybe there’s something I’m not thinking of.

I already have adjustable sprockets on the current cams I’m running set at 105/107.
The ones I want to repair have been sitting in a drawer for a dozen years and I was looking to do something useful with them.
My bike has 50k in it now and I’m planning a new top end in the near future, nothing extraordinary… just an upgrade.

You can use oil cooled motor rocker arms. Oil cooled motor camshafts have smaller base circle diameter.

[Tom R]

Good to know. Thank you. I mailed them off, We’ll see how they turn out.