The International CBX Owners Association

Hi guys, okay I aborted the valve seat damaged head. Now the focus is on another one, this one has 2 journals on the right exaust cam that got damaged from a tower installed backwards " arrow pointing up " resulted in a heat seize, changed the 2 towers # 8 and # 5, I sanded the journals and buffed them with a dremmel tool, plastigauged it and showed .003 and about .004 on the other. Any other things I can do before using this. # 6 & 7 towers and journal did not suffer any damage.
One more thing, has anyone ever sanded down towers to get a closer tolerance, my intentions are to correct a very noisy start up when cold, It obvious to me it's an oil delivery problem,
as it warms up the ticking goes away, the cams were out of range on the lobes and on the towers, used chains and worn cam joints, the valve were set at .003 to .004, oil pressure sits @ 64 psi. I'm installing new chains now, different cams and cam joints, and finally this head with new seals, it should take care of my concern.
Thanks for any inputs

Marc
81 CBX

The ticking when cold may come from the Oldham couplers between the cam halves. They may expand when warm and sit a little tighter than when cold if they are worn.

Mark, My advice would be to research another head on e-bay. It is possible to build up towers/caps & have them line bore to tolerance but you "may" find it quite expensive...If you have lots of surface area you can actually "dimple" the area ( it raises the metal) with a center punch & then have them line bored....
I remember ( somewhere in the dark haze of my mind) that someone was actually machining & inserting shell bearings to save heads ....

Hello Marc.
Have you considered using LOTUS TWINCAM camshaft bearings to reclaim your head. They are universally available off the shelf. they are standard split shells. steel backed with white metal lining. The od is 1.125 and id 1.00 Each engine set comprises 8 off at 0.75 wide 2 off at 0.5 wide. It is a relatively simple job to line bore the head. it can be a diy. job if you can get a simple boring mandrel and some guide bushes turned up. The camshafts can have their journals turned as they are usually not hardened.
It would be straight forward to lower the cam cap and re-bed it to the camshaft using " engineers blue" and a good scraper. I have just done this repair to number six cap, someone had fitted an odd cap without bedding it to the journal.
Regards,
Dave.

Hi all, turns out that my ticking when cold was from my pistons.
I assumed the machine shop followed my instructions with piston to wall clearances at .002 but they had their own conclusions and bored them at .0075
My fault for not double checking and no excuses. I was only able to register 155 psi of compression in all the cylinders, turns out after my check that I had .014 ring end gap.

Needless to say, I need another block to bore for these 2nd over pistons.

Thanks for all the input previously.

Marc

Thanks for the valuable feedback Marc, good luck & keep us posted....

What did the shop have to say about not doing what you told them to and turning your cylinders into a useless block of aluminum?

With respect to your piston noise and clearance issue: Are the pistons you are fitting cast or forged? The 0.002" clearance is about right for cast pistons; the 0.007" is about right for forged pistons. The forged pistons are more for racing than street. They will slap when cold: need to be brought up to temp. Forged are stronger, good for racing loads or high output street machine being run hard. Cast is better for normal street use, overall. If you are running forged pistons on the street at normal street loads, you can, also, expect a bit more oil consumption. All this not to advise one or the other: just to show the pros and cons and some of the characteristics of each.

As I have learned from somone much more knowlegable than I (Mike Nixon), my recommendations relative to piston fitting were off-base. The clearances are considerably tighter than I mentioned. Still, with forged pistons fitting looser than cast. Consult your supplier/manufacturer is likely the best advice.