Cams and rockers overhaul

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Old Fogey
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Cams and rockers overhaul

Post #1 by Old Fogey » Sun Mar 08, 2009 6:46 pm

If I may I'd like to add some more info to all the great input that RR has done in this post.

http://www.ngwclub.com/forum/viewtopic.php?t=7683

The heads are where all your power is made.
The rest of the engine just transmits it, the carbs and ignition system that you've carefully overhauled and got just right enable the head to make the power but if your valves and valve train along with pistons and rings aren't up to scratch all your hard work is for nothing.

Like Randakk says on his site 'Everything affects everything'

Very important. You will note that when Reb changed the cams he also used the carrrier and rockers that came with that cam.

There is very good reason for this.

This is because the cams and followers wear into one another.
The cams are only rough sand castings before being machined and not very accurate castings at that!
If you look carefully at this brand new cam and the way the rocker sits on it you will see what I mean. (I know, poor photo)



Image



That cam lobe will wear with a ridge left on the right side. You can imagine the damage if that cam was put with a rocker that sat on the ridge!

The problem is compounded by the need to keep the tappet adjuster screw almost centred on the tip of the valve stem so, even if shims were available, you can't just move the rocker over to compensate.

I'm not sure that it is either necessary or a good idea to change the carrier as well as the rockers.
There is no separate part number for the carrier, leading me to suspect that the carrier and head are machined together and should be considered as one unit.
I know Honda's legendary reputation for quality control, so in most cases the parts will interchange without a problem, but why take the chance.

If you are forced into using the same rockers it is imperative that all wear marks from the old cam are removed first.
The pads appear to be faced with something hard, probably Stellite, so doing this takes a bit of effort but it's well worth it if you don't want your new cams wrecked in the first few minutes of running.
Using something flat, in my case an old worn Smooth file, wrap some 600 emery paper or cloth round it and gently remove any ridges or depressions on each pad. Follow up in the same manner by polishing with Crocus cloth until they look like this;


Image


OK. We've got the new/other cam and the pads are dazzling with all your polishing!

Next step is to examine the rocker shafts for wear. There will be some, on the underside of the shaft, where the rocker is pushed into it by the action of the cam and valve springs.

So get the micrometer out and .......................nah ! ! !

Just do this;

http://www.ngwclub.com/forum/viewtopic. ... 443#141443


Well, we're getting there.
What other remedial work can be done?

Due to the need to have a gap between the rocker tappet and the valve stem tip to compensate for expansion differences, the tappet is adjustable.

Unfortunately perhaps!

Very rarely do you find that the gap has been set accurately ( by the PO of course!). This could be due to a number of things;
lack of attention, inexperience of whoever is doing it or more likely, some wear .

The valve tip can become dimpled by the hammering action of the tappet adjuster. This dimple will usually be bigger than the point of contact of the adjuster. This is because the adjuster POC is often very slightly offset on the valve tip. When the engine is running this offset imparts a rotation to the valve which evens up wear of the tip, stem, valve guide and valve seat.

The correct way is to have the tip lightly reground but the home solution is as above for the pads with a couple of exceptions.
I find it easier to do with the valves held in the bare head ie. just placed in the guides without any springs, cam etc. either both inlets or both exhausts. If the head is held down on the bench they are then easy to work on.
When doing your polishing keep square to the stem and do it like the points of a compass , not all in one direction!! And remove as little material as possible
Obviously it's necessary to ensure that no particles off the emery are left so give the heads and valves a good wash off when you're done.

Yeah! finished with emery etc.!

Nope! You've forgotten the adjusters themselves!

The Honda adjusters have a slight dome on the contact face resulting in a very small POC.. Obviously, with the adjuster being held in one position, a flat will develop at that point over time.
Next time you do an adjustment you could wonder why it's taking forever to get it right.

Two choices; if they look real bad, replace the them. Cost about $5 each.

My way.
I set up the Dremel in the stand and dressed up a fine stone to a radius that looked approximately right. I don't believe the radius to be all that critical.
Each adjuster was then chucked up in a drill and with the Dremel and the drill on was very gently touched to the stone. And I do mean very, very gently. Incredibly easy to remove a whole lot of material that way.
Ask me how I know; go on, you know you want too!!! :oops: :oops:

With the adjuster still in the drill, give it a final polish with the Crocus cloth.

Also I've posted this before.

The early carrier had one oil hole slotted but the other two were simple holes

Image


The later carrier has larger deeper slots on all three oil holes and on mine there was noticably less in the way of scuff marks on the journals.

Image


This would be a very worthwhile modification in my opinion to any early carrier. It would be relatively easy to do with a Dremel, the slots needn't be all that accurate or flat sided as their only purpose is to get more oil further round the journal.

Now you can put away all the emery, drills etc. :lol: :lol:

Well, don't just sit there looking all pleased with yourself!

Time to assemble the darned things.
Exhaust rockers go into the carrier on the side with the cam oil hole or slots in.


Again Reb's thread covers the rebuild in detail.

I would only add two things.

Most Important!

You must coat the cam lobes, pads and journals with a moly grease and oil the oils seal lips on assembly. No ifs, buts or maybe's

This orifice is the pressure feed hole for the oil to the rockers, shafts and cams. The oilways also run round all the carrier bolts.

Image


We don't want to loose any pressure to these so apply a smear of sealer (only a smear or you run the risk of blocking up one or more of the small oil holes in the shafts) on the carrier pedestals and also around the outer diameter of the new ( they are, of course, new, aren't they?) cam oil seal(s) before bolting the the cam carrier down.
Last edited by Old Fogey on Sun Apr 26, 2009 3:36 pm, edited 2 times in total.
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Roady
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Post #2 by Roady » Sun Mar 08, 2009 9:09 pm

Very nice tutorial, Old Fogey.

Our ShopTalk page certainly is getting meaty and beefy.

Keep up the excellent work. You might even get to ride it someday. 8)

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Post #3 by ElPiloto » Mon Mar 09, 2009 1:31 am

You have just been promoted to Grand Master Engine Builder.

I am facing the UK and saluting you.

Congratulations. Excellent write up and photos. 8)
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Old Fogey
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Post #4 by Old Fogey » Mon Mar 09, 2009 8:56 am

Thank you so much for your comments, guys! :oops:

Praise indeed coming from the likes of you fellas.

I just welcome the opportunity to pass on to others some of the accumulated knowledge that clutters up what passes for my brain as I have no-one that I can do so to directly.
--------------------------------------------------------

'The Swan' complete rebuild album - See the result here!

ENGINE REBUILD TIPS - Stuff you won't find in the manuals!


"Impossible Is Just a Level of Difficulty!..."
If I'd wanted you to understand, I would have explained it better! (Johann Cruyff)
I’d give my right arm to be ambidextrous! :-D

click the banners below:
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( Seriously, you haven't read all 115 pages of the WinGovations website ?? :shock: )

AXL Stubbs
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Re: Cams and rockers overhaul

Post #5 by AXL Stubbs » Thu Mar 25, 2010 1:34 pm

We don't want to loose any pressure to these so apply a smear of sealer (only a smear or you run the risk of blocking up one or more of the small oil holes in the shafts) on the carrier pedestals and also around the outer diameter of the new ( they are, of course, new, aren't they?) cam oil seal(s) before bolting the the cam carrier down.


Can you tell me what kind of sealer you used? I've got some "High-Temp RTV Silicone Gasket maker" Any issues with that?

I was also planning on using the same stuff between heads and heat shield/timing cover, and points cover. instead of getting the the complete engine gasket set.

Thanks in advance!
AXL Stubbs
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Old Fogey
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Re: Cams and rockers overhaul

Post #6 by Old Fogey » Thu Mar 25, 2010 3:50 pm

On the outside of the engine there is no problem using that; done it many, many time myself. On the inside, yes you can use it but as I wrote, a smear is all you need! It take a minute amount to seal between two matching machined surfaces and yet folk insist on trowelling the stuff on thick, with the result that the squeezed out excess gets everywhere inside the engine, clogging up oil ways, filters etc.
It would actually be better not to have used anything at all rather than that!
--------------------------------------------------------

'The Swan' complete rebuild album - See the result here!

ENGINE REBUILD TIPS - Stuff you won't find in the manuals!


"Impossible Is Just a Level of Difficulty!..."
If I'd wanted you to understand, I would have explained it better! (Johann Cruyff)
I’d give my right arm to be ambidextrous! :-D

click the banners below:
Image Image Image

( Seriously, you haven't read all 115 pages of the WinGovations website ?? :shock: )


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