Machining for cam..

need4speed · Post by **need4speed** » Fri Aug 29, 2008 9:06 pm

Has anyone used real steels 'stump puller' without any machining work to the heads?
RS reccomend that you machine 0.1" off the top of the valve guides. Just wondered if you can get away without it or if its a 'must'??

CastleMGBV8 · Post by **CastleMGBV8** » Fri Aug 29, 2008 9:44 pm

N4S

The stump puller has .465" of lift so think it would be necessary. also important to use the correct valve springs to match the cam, usually one coil less to avoid coil binding.

Also with the increased lift you will need to adjust the valve gear geometry by machining 50thou of the rocker pillars and fitting shorter or adjustable pushrods to obtain the correct lifter preload. If you don't adjust the geometry you will get excessive wear to the rockers and valve guides.

Des Hamills book How to Power Tune Rover V8 Engines covers this in great detail.

Kevin.

kiwicar · Post by **kiwicar** » Sat Aug 30, 2008 7:11 am

or you can use lash caps on the top of the valves and shim the pillers and use standard push rods. Not in Des hamills book but much less work.
Mike

need4speed · Post by **need4speed** » Sat Aug 30, 2008 7:49 am

thanks for the replies fellas. what exactly are 'lash caps'?

sidecar · Post by **sidecar** » Sat Aug 30, 2008 8:12 am

I went down the adjustable pushrod route and due to the head skimming and rocker pillar boss machining the pushrods were about 4mm too long. Someone with a lathe can do this very easily. Be aware that there is a small internal step that needs drilling out if you shorten the pushrods, there is an internal step that prevents the ball ends being pushed fully home, a drill can sort this out.

The four pushrod holes (one at each end of each head) might need a bit of filing to give the required clearance. The nice thing about the RS pushrods is that they are lighter and stiffer than the standard ones.

Pete

need4speed · Post by **need4speed** » Sat Aug 30, 2008 8:31 am

hmmm good info there. one thing that ive just noticed looking at the valve guides is that there is a kind of rounded edge at the top. Obviously machining 0.1" off the top of the guides is going to almost remove this. will this affect how the valve stem seals fit in any way??

kiwicar · Post by **kiwicar** » Sat Aug 30, 2008 12:04 pm

Lash caps are caps that fit over the top of the valve and collets above the valve cap, they are available in various thicknesses and effectivly make the valve stem longer so altering the angle at which the tip of the rocker contacts the valve, altering the geomitry if you either raise the pillers or shorten the push rod. Shortening the pushrod is an option and is alot less cost than getting the pillers machined if you have to farm the work out. Shimming the pillers and using lash caps means you can re do the geomitry without having to custom machine parts. Depends what kit you have access to.
If you are renewing the valves anyway you could buy .1" over length valves, .1" length overlength springs and not have to machine the guides and not bother with the lash caps, always more than one way to skin a cat.
Mike

CastleMGBV8 · Post by **CastleMGBV8** » Sat Aug 30, 2008 2:00 pm

Pete,

I was under the impression that the adjustable p/rods were heavier if not i will reconsider.

The idea of using lash caps to adjust the geometry hadn't occured to me but I suppose thats what there for

I 've yet to fully sort my valve gear, the new engine isn't in the car yet and has not been run.

I was going to machine the pedestals and use some Chevvy 7.950" pushrods but it would seem a good idea to use lash caps and adjustables as you can be more accurate setting the preload.

Do Real Steel do the lash caps as I've not seen them in the catalogue .

I will have to do a sketch to work out the required thickness to put the rocker in the optimum position, any idea up to what thicknesses are available.

The engine after a delay of 2 months is definitely being fitted in the next couple of weeks so need to get this sorted, I have a very good machine shop round the corner in Sidcup and whilst not being auto specialists they are very good machinists and did a good job machining an SD! front crank damper to make it into P6 spec pulley or only £15.00 so they should be able to shorten the adjustble p/rods for me.

Kevin.

need4speed · Post by **need4speed** » Sat Aug 30, 2008 3:44 pm

.....one thing that ive just noticed looking at the valve guides is that there is a kind of rounded edge at the top. Obviously machining 0.1" off the top of the guides is going to almost remove this. will this affect how the valve stem seals fit in any way??

kiwicar · Post by **kiwicar** » Sat Aug 30, 2008 7:28 pm

Real steel do them (look under chevy if you can't find them for rover, valves are the same stem) mine were .08" thick, I think you can get other thicknesses from other suppliers.
Mike

sidecar · Post by **sidecar** » Sun Aug 31, 2008 11:46 am

CastleMGBV8 wrote:Pete,

I was under the impression that the adjustable p/rods were heavier if not i will reconsider.

Kevin.

Hi Kevin,

I did not actually weigh the pushrods that I fitted but I'm sure that I read somewhere that they were lighter! May be RS can tell you the weight of one of them.

There is probably very little difference if they're lighter or heavier. I Know that the standard ones are solid and the RS adjustables are hollow, obviously the adjuster must weigh a bit though.

Being a wider tube rather than a thin solid rod they should be less prone to "pole vaulting" the valve as the follower goes over the nose of the cam.

If you do buy them let me know, I explain how I fitted the ball ends without "doing in" the adjuster! (not much to it really)

Pete

CastleMGBV8 · Post by **CastleMGBV8** » Sun Aug 31, 2008 11:56 pm

Pete,

I understood that they came without the bottom ball fitted, is it the adjustor thats not fitted and whats the trick to fitting them?

I think I will definately go the lash caps route as its a lot simpler with the added bonus of havinf a larger area for the rocker tip to run on, I assume they just press on to the vale stem tip and are held in place by the lifter preload.

I checked the Real Steel Chevy catalogue and the caps are 80 thou, which is about perfect for the the cam I'm using, Crower 50232 with .488" of lift. I think I'll also get a P/rod length checker to make sure I get the adjustables cut down to the approximate correct length so as to have a bit of adjustabilty up or down.

Kevin

need4speed · Post by **need4speed** » Mon Sep 01, 2008 7:34 am

errr does ANYONE know if machining the top of the valve guides will affect the way the stem seals will fit?

sidecar · Post by **sidecar** » Mon Sep 01, 2008 9:19 am

CastleMGBV8 wrote:Pete,

I understood that they came without the bottom ball fitted, is it the adjustor thats not fitted and whats the trick to fitting them?

I think I will definately go the lash caps route as its a lot simpler with the added bonus of havinf a larger area for the rocker tip to run on, I assume they just press on to the vale stem tip and are held in place by the lifter preload.

I checked the Real Steel Chevy catalogue and the caps are 80 thou, which is about perfect for the the cam I'm using, Crower 50232 with .488" of lift. I think I'll also get a P/rod length checker to make sure I get the adjustables cut down to the approximate correct length so as to have a bit of adjustabilty up or down.

Kevin

Hi Kevin,

I'm a bit confused! You are going for the caps and adjusteble pushrods? Are you using the caps to get the gemoetry right and the rods to get the pre-load right?

Anyway, you are right, its the bottom ball that not fitted. You need to be careful that you do not damage the adjuster when fitting the bottom ball joint as it takes a fair amount of effort to fit the ball. I Drilled a hole in a piece of hard wood that is smaller in diameter than the pushrod, I then cut the wood in half so that a semi circle of the hole was in each side. The wood was used a soft jaws for my vice. (You could use a lump of ali rather than wood). Even then it was impossible to hold the pushrod firmly enough to fit the ball end so I arranged the pushrod so that it was vertical in the vice with the adjuster pointing down and firmly pressed against something hard on the bench (a large socket or something similar). You could remove the inner "bolt" part of the adjuster or make sure that it is fully screwed home with the lock nut right at the end of its travel. It is then possible to hammer the ball end into the pushrod! using a hammer sounds really bad but in fact as the ball ends are made of super rock hard steel they were not marked or damged at all during this process. I tried to get the length of my pushrods setup so that there was about 2 turns of adjustement left once the pre-load was set right.

Regards,

Pete

CastleMGBV8 · Post by **CastleMGBV8** » Mon Sep 01, 2008 10:25 am

Pete,

Yes it seems a good idea to raise the height of the valve stems to get the geometry/relationship of the rocker tip and top of the valve correct.

I was going to have the pillars machined by 50-60 thou. but fitting the lash caps seems a much simpler and probably better solution and then shorten the adjustables to get the preload in the right area with just final teaking to get the preload where it should be, say 20-25thou.

At the moment the valve gear is standard but with heavy duty tubular pushrods and I needed 50thou of shims to get the preload to 35thou which is obviously not very good.

I will need a pushrod finished length of approx 7.975" standard seem to be 8.050"

Do you see any problem with doing what I'm now suggesting.

Kevin.