adjustable push rods

Seight-V8 · Post by **Seight-V8** » Sat Jan 17, 2009 3:35 pm

hiya all,

Got loads of questions today...lol

next one on my list.

Anyone know the amount of adjustment in adjustable pushrods from real steel.

Whats the smallest to the largest lengths that you can adjust them too.

Reason is....

Had loads of problems with the heads i have...and still very unsure as to whether my rockers should be shimmed to improve the rocker geometry.

My rocker geometry looks better if i shim 1.75mm under the pillars.

Havent check preload yet...as still need some pushrods.

Just dont want to find out the i might need longer ones.

cheers

scott

sidecar · Post by **sidecar** » Sat Jan 17, 2009 4:51 pm

The RS pushrod adjusters are virtually screwed in all the way on a standard engine. I'm suprised that you want to shim up the rocker shafts, the normal thing is to lower them. I ended up using the RS pushrods and I still needed 4mm taking off them before the ball end was fitted. (My heads have had 70 thou off them and the heads have had 1.5mm macined off where the pedestals sit). There is an internal step inside the pushrods, if you shorten them the step needs to be drilled a bit deeper

The pushrod holes at either end of both heads needed ovalizing, the other holes were OK.

Pete

Seight-V8 · Post by **Seight-V8** » Sat Jan 17, 2009 7:21 pm

hiya,

i know that my heads have been machined 1mm under the dimension in the manual.

But when my rockers are resting against the valves, the angle doesnt look right.

If i put 1.75mm under each pedastal...then things look better.

Still struggling to understand about rocker geometry and what the best setting is.

If adjustable rods are about closed when standard...then if i need to add 1.75mm to each pedastal...i should have enough adjustment.

Havent even got to valve clearance & lift yet.

scott

CastleMGBV8 · Post by **CastleMGBV8** » Sat Jan 17, 2009 8:15 pm

Scott,

I would agree with what Sidecar (Pete) said.

The rocker gear geometry in a standard engine is not ideal but is probably ok for an unmodified engine that will spend it's life not exceeding 5000 RPM.

On a performance build with modified heads and a performance cam with a lot more lift with an extended rev range, the rocker gear really does need optimising to achieve the correct relationship with the rocker tip and valve stem, Des Hamill's book goes into this in some detail.

If the cam has more than .450 of lift you need to either machine the seats that the rocker pillars sit on by 60 thou.or do as I did and remove 60thou from the Pillar bases, if you machine the pillars you will remove almost all of the area that provides the oil feed to the rocker shafts and this must be machined back into the bases to maintain the oil flow.

Once this work is done you will need to assemble the valve gear with a checker pushrod to establish what length the pushrods need to be, take several measurements as there will be some variation.

As pete said, even the adjustable pushrods will be too long, which is one of the reasons they come with the lifter end unassembled ,to allow for fitment of the correct ball to match your lifters and the length to be adjusted.

You also have to be careful how you reassemble the the rocker gear, if you have the manual it will tell you how to do it, but to be on the safe side if you make sure the oil holes in the rocker shafts are pointing down towards the centre of the V you will be ok.

Probably not what you wanted to hear but there is only one way of doing it right.

I think I spent as much time optimising the geometry and setting the preload as it took to assemble the rest of the bottom end!

Kevin.

sidecar · Post by **sidecar** » Sat Jan 17, 2009 8:52 pm

You really must dry assemble the engine with weak checker springs fitted, colour in the end of the valve stem with engineers blue, you can then slide the rocker from side to side so that the contact point marks a line across the valve stem. Do this with the lifter off the lobe and again with the cam at max lift, you can then see where the contact lines are. Lowering the pedestals moves the low lift contact nearer the edge of the valve which is not great but what it does do is put the contact line further away from the edge of the valve at max lift. This is FAR more important as the spring pressure is very high. I filled an old lifter with candle wax to make it solid when I was doing the checking.

I would not worry about 1mm being taken of your heads, that's barely a clean up compared to mine!

Sorting out this sort of stuff makes the difference between an OK engine and a really good one! (it just takes ages!)

I really, really suggest that you buy Des Hammill's book, it's all in there!

The pre load is easy to setup with the adjustable rods, once you have done a few with 20 thou wire you can workout that you can take out all the play by carefully turning the adjuster then just turn the adjuster a number of flats. (3 from memory gives 20 thou which is what I set mine to, not 40 to 60 as RS state!)

Pete

Seight-V8 · Post by **Seight-V8** » Sun Jan 18, 2009 1:57 pm

thanks guys,

Just what i needed....got plently to keep me busy for a while now.

Didnt think in the begining that i would need to go this far...but like you say it will be worth it in the end.

I've learnt many new things this time round.

cheers

scott

ian.stewart · Post by **ian.stewart** » Sun Jan 18, 2009 3:23 pm

Dunno if you noticed, last week I posted up a link for pushrods available in length increments of 0.05" once you work out the size you need It may be worth looking atand not too expensive either. Real Steel used to sell a kit for making fixed length pushrods.