Army,

i cant add anything technical, other than to say stick with it. you've gone too far not to have it perfect.

retracing the steps of past 'mechanics' is horrible. i had a similar experience with the transmission on the 82.

I agree. You've done some nice work so far.... I hate seeing little things like this 'throw a rocker arm' into your plans.

And not to be a ninny.... but you should just remove the chaos completely from this equation. Keep the rockers, and scrap the rocker towers and dowels. They have been torqued down with foreign stresses on them - aluminum is soft.

If you can't get them where you live, I have a set lying around if you can cover shipping from 'merica to your pond.

Thanks a lot jt20 - I've done some more investigative work and I'm now thinking that the problem perhaps has more to do with the camshaft not being in the correct position.

Why?

Because I've been playing about with the rocker arm towers today and I keep on getting consistent results. No matter which bit I swap about the alignment is always pants. The rocker arms are all between 20.05mm and 20.12mm in width. The rocker arm towers are all within 0.08mm width of each other - amazing but true!

Whereas the camshaft seems to be more askew when you compare the lobe positions with the nuts on the top of the valves. I know that this is a bit of a dodgy comparison as the valves probably aren't 100% vertical - well it must be difficult to get that perfect - when I lapped the valves into place I noticed an ever so slight variation in the position of the contact between the valve and the valve seat on some of the valves... that indicates some variation - I mean there has to be a little tiny bit of wiggle between the valve stem and the valve guide - it is a clearance hole.

Anyway I've set up a DTI on the end of the camshaft (back end of the engine) and measured the deflection of the camshaft for a full rotation - it was only 0.05mm which doesn't suggest any misalignment. This is yet another dodgy measurement as the end of the camshaft is quite roughly finished - well it isn't polished!

So I plan to visit the engine builder next week (as soon as I can) to see if he can check out / find a replacement first camshaft tower for me.

To be continued.

Thanks to everyone for their continued help and interest.

I haven't read the entire thread but seeing this pic I have a few questions:

Was all fasteners torqued to spec when photo was taken?

Have you checked the flatness of the top of the head with a straight edge?

Have you checked the flatness of the towers base on a flat surface?

http://www.peachparts.com/shopforum/...1&d=1296743888

This raised a big red flag for me. And I have more bad news (you must be sick of me by now!), but I must say it.

ANY perceptible wiggle in the valve stem means you need new valve guides and consequently a total valve job. - which also, consequently requires some machining of the head surface. Sure, you can skimp a bit... but I have made the same mistake and I am now regretting it (and correcting it).

If there is any variation in the valve stem, the seal on the valve seat is lost, resulting in poor compression and the inability to accurately adjust your valves - when the time comes.

I promise, it will only get worse. The valves will become ovalized as will the seats in the head. The chattering / vibration of the stems in the guides will exacerbate the wear of the guides and continue this process.

This, in my experience, is the source of many rough running engines. People attempt to fix other things because these engine CAN run smoothly, but uneven compression happens differently when the car is running as opposed to when you do a compression test at 200 rpm.

I hope I have not ruined your day.

Additionally, up until this point I was under the impression that the rockers were out of perpendicular with the camshaft..... you are saying otherwise.

Could you please take some pictures from a bird's eye perspective on the head in your free time (if you have any left)?

Or, at least a picture of the sight that is truly troubling you.

About the camshaft...


Can you spin it freely with the towers bolted down?


Rocker failures are know to snap camshafts when they occur. Perhaps your set of cam towers was deformed from a previous episode?

Yes yes and yes!
 

Short answer - yes yes and yes!

Long answer - this picture happens to be the start of the problem when I discovered that the order in which the groups of rocker arm towers were incorrectly positioned on the head. That has now been rectified - after a bit of bad language and threats to the safety of someone who lives on this side of the water... see post # 31

I completely agree - I've obviously given the wrong impression. The head has been refurbished by a machine shop over here. The valves were re-ground (2 replaced) and the valve seats were re-cut after the new valve guides were fitted. (Full story here http://www.peachparts.com/shopforum/showthread.php?t=276144)

I'm trying to point out that the fit between the valve stem and the valve guides is a clearance fit. So it will "wiggle" - albeit a very very tiny wiggle.

The problem of tilted rocker arms running with their edges grinding into the cam lobes is gone - this was rectified by positioning the rocker arm groups correctly.

Group of two => sits over cylinders 1 and 2

Group of three => sits over cylinders 3, 4 and 5

(Just as you said)

If you try and fit the group of two over the back cylinders you get the arched effect which then means the rockers are tilted...

The problem now is that whilst the rocker arm surfaces are in parallel with the cam lobes they do not sit correctly in line.

Just like this:-

http://www.peachparts.com/shopforum/...4&d=1296932072

See for example the last set of rocker arms on the right hand side of this picture (over cylinder 3)

http://www.peachparts.com/shopforum/...6&d=1297160370

The cam does spin freely.

The axial clearance is within limits and when you turn the camshaft the end of the camshaft appears to run true... only a deflection of 0.05mm

I'm hoping that the front camshaft tower is slightly out of whack - or that it is too thin - otherwise I'm back scratching my head again.

Thank you bringing me up to speed and clarifying.

I am unsure of how much discrepancy in this direction is acceptable, but I have never seen it mentioned in the FSM. I am going to wager that yours is permissible, but I will supply data.

I have a rebuilt head coming way and a beautiful set of unscathed rockers to mock up for you. That, and pictures of my engine.

Keep in mind these engines were probably designed in the 60's, and the rocker towers do not use the most precise means of locating themselves in relation to the cam.

I mentioned that the towers might be deformed due to the bending of the mounting dowels... perhaps you should roll one of the dowels on a flat surface?

good luck, hang in there.

FSM spec for tower:

Width of rocker arm bearing bracket 24.07-24.20

Which photo is correct? The one with two stanchions at the rear, or three?

It goes with the group of three at the back (over cylinders 3, 4 and 5)...

...and the group of two on the front (cylinders 1 and 2)

Strangely it isn't specified in the English translations of the FSM - but if you look through the parts catalogue you'll see nice drawings of it!

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Sorry for the confusion - in my defense it was part of the original problem - which has now moved on to something slightly different.