Cams feel tight

Keith,

Love the way you set up/sort out heads.  Mine was perfect  ;)  (although now back on the bench, as the rest of the 3c is being fettled, hopefully to a good enough standard to come close to the head).

Vince - I have always used old 1950s gauges & tools, but needing metric, I bought some 150mm Mitutoyo calipers a few years back (the mechanical ones). Absolutely bombproof, easy to use and accurate. Cheap too (about ?35).

Pete
 
The barrels were top faced when I had them rebored. Lost the 0.1 recess on the top of the sleeve. I think he said he took 8 thou off.
I reckon the top face of the head is bent. Something is going on though. The cracks in the corners at the cam tunnel, even though they have been there for many years, have only just shown up since the head refurbishment now having a a slight ridge across the crack on the cam cover face. Not torqued all the way down yet, 15lbf across all the studs. The cams are true.
The guy I had do the head and barrels is probably the most competent engineer in Perth, that I know of anyway and been around going back to the 70s. I gave him the head, cams, cam bearings so he would have had to set them up when doing the valves as the head came back shimmed. The head hasn't been faced.
I'll torque it down to final spec and see if that makes difference. At this stage I think I'm better off lowering the centre cam bearing to achieve alignment. What's the best way to remove metal from the bottom of the bearings when one doesn't have a mill??
In reality it's probably only half to 1 thou.
Fuck'n Laverdas!!!! My BM doesn't give me this much trouble!!!

Thanks for your input guys.

Vince, I have 2 Rabone Chesterman combination squares I use for general stuff and keep my Mitutoyo combination set for engineering purposes. I have 3 Mitutoyo verniers, 6", 8" and 12" as well as micrometers and dial gauges. I have some Moore and Wright stuff that my father gave me. All good stuff and would never buy chinese measuring equipment or tools in general.
 
Dellortoman said:
I got a slightly uneasy feeling when I read the title of this thread  :D

Cam
Click to expand...

As soon as I saw the title I felt queasy. At first I thought Rob had been careless with his missing apostrophe then had great relief when I read the first post.
 
Did some measuring today, it seems that the head is higher in the middle by 0.05mm, just enough to slightly bind the cams.
I rechecked the cams and total run out was half a thou on both shafts.
I think the best way to go is to remove 0.05mm from under the centre cam blocks.
Without a mill, any suggestions on the best way to go about it??
 
Rubbed on fine grit wet and dry mounted on a dead flat steel backing ??
 
You could use a plate glass mirror as a flat bed for the wet and dry paper too.
 
Hi Stefan, torqued down to 25lbf on the 9mm studs and 18 on the 8s before measuring.
I played with a piece of ally last night using a 1" chisel and scraping was able to remove .1 with hardly any effort so will go with that option cause I can see what I'm doing and have a better chance of keeping the surface square and flat.
At the end of the day they are only cam bearings and easily replaceable.
Think I'll start looking for another head as this one I have lost confidence in.
So who's going to produce a nice billeted head for these motors then?, not that I can afford one at the mo unless I get a real job again. ???

Thanks guys for your input
 
Cam fitting update. So I removed 0.08mm off the bottom of the centre cam bearings. I used a scraping technique to remove the ally and finished off with 400grit wet/dry on a flat blade. Got it to within 0.005mm.
Reassembled and torqued down, the inlet feels like it should but the exhaust cam started tighten up once the torque figure reached 20lbf on the M9 studs. So I removed another 0.02mm from the centre bearing. Reassemble again and once again it start binding at around 20lbf.
Now for something weird, I removed the centre bearing and retorque the cam down and once again the cam started binding at 20lbf.
I'm now thinking the outer bearings are moving out of alignment under torque. Could it be that the head being slightly banana like is causing the outer bearing to bind on the cam?
The inlet is now perfect when fully torqued down so why is the exhaust being a pain in the arse?

The other thing I noticed, the bottom half inlet cam bearing measured 10mm while the exhaust measured 10.45mm.
 
Rob,

Before final torquing, give the camshaft a firm clout with a copper or lead mallet.  This must occur next to a bearing and perpendicular to the head and will help align the bearings.  This method of freeing off the cams is mentioned in some of the original factory workshop manuals!

I use a normal hammer and a sturdy alloy drift and often helps with stubborn cams that show the symptoms you describe.  If the guide slots in your head and the spigots at the base of the bearing blocks are less than ideal, the cam blocks can rotate slightly off-line while torquing down.

piet
 
Well, after Piets sledge hammer suggestion, I hope you haven't taken too much meat off! :o :o

Good luck Rob, this sort of shit shouldn't happen to the nice guys of the world!
 
Piet, so I gave the cam a good wack with mallet and ally drift. Cam still tightens up when the torque reaches 18lbf. At 25lbf it's way too tight to ignor :o It's got me fucked!! Something going on with the outer bearings I think.

Hey Chris, this head has been 1 step forward 2 steps back from when I first dropped it off at the engineers for refurb.
 
Rob, get some bearing blue, and smear that around the towers, then re-install, give the cams a few turns, rip'em out and that should alert you to where the binding is happening. Let's see where the problem is.
 
Once torque reaches 18lbf the the cam starts binding, at 25lbf it's way too tight. If I release the torque on the centre bearing it's still binding. Re torque then release the torque on #1 bearing, still tight, re torque and release on #3 and the cam frees up. I removed the centre bearing and re torqued the 2 outers and the cam was binding again. So something weird is going on with #3 I reckon.
I reckon this head is cursed, it's pay back time for years of abuse I suppose!

Hey Chris, I have bearing blue, it crossed my mind earlier if I should use some!
 
do you have any brass shim material, can shim below the bearing to see if it is too low
or use an old feeler gauge

 
Hi Red,
Don't have brass shim less than 0.25mm! but I did have a piece of 0.04mm feeler gauge that I sectioned and raised the #3 bearing. Retorqued to 25lbf and the cam felt less bound, not far off acceptable.
I find it hard to believe that going from 18lbf to 25lbs on that one stud is enough to bind the cam. How do I get around this problem? It's got me fucked!!
 
motoddrob said:
Hi Red,
Don't have brass shim less than 0.25mm! but I did have a piece of 0.04mm feeler gauge that I sectioned and raised the #3 bearing. Retorqued to 25lbf and the cam felt less bound, not far off acceptable.
I find it hard to believe that going from 18lbf to 25lbs on that one stud is enough to bind the cam. How do I get around this problem? It's got me fucked!!
Click to expand...

Don't despair Rob, it sounds like you are very close to nailing it!
Obviously something (the cam shaft) is bending or distorting when you hit the magic number.
Same problem as finding a 'soft foot' on a motor when trying to laser align it. progressive tightening and loosening each foot until you find the one that sends the numbers crazy, then shim that foot up until it doesn't matter if it is tight or loose - numbers stay the same.

This is what you have done, it is no. 3. Now you need to shim it until it makes no odds whether nuts are tight or loose. A coke/beer can cut up into strips will act as a shim temporarily and then use a micrometer to get the overall thickness when you are done and stick a stainless/brass one in.

I fixed a hinge link field fence manufacturing machine with a coke can once, no shims in the stores the tight bastards!!!!!

Fine tuning - as Chriskay said, engineers blue.
 
You must log in or register to reply here.
Back
Top