Rhodes Lifters (RV8) and head skimming

[Chassis 33]

Hopefully just a quicky, do you go about checking and setting the pre-load on Rhodes lifters in the same manner as standard lifters on the RV8?

Also, (and this could save me a days work) when the engine was built some considerable care was taken by the builder to get things "right", eg cam timing, lifter pre-loads etc. However...I'm in the process of getting the heads skimmed as a result of an air lock cooking a head gasket and warping the heads, is it possible to shim out the rocker pedestals by the extra amount in relation to the amount skimmed from the head (taking into account the rocker ratio) or is it not as simple as that and I have to start from scratch?

Regards
Iain

[GreenV8S]

In principle I guess it should be that simple, but you need to be careful about the various mechanical ratios. Chances of getting it bang on at the first attempt pretty slim I'd have thought!

[Chassis 33]

Cheers Peter, other than the ratio across the rockers what other ratios do I need to look out for, the cam etc has remained in situ?

Regards
Iain

[stevieturbo]

Pre-load is done in exactly the same way for Rhoads, as normal lifters.

I found easiest way to measure was with the bent wire style spark plug gap tool, measuring at the lifter circlip itself.

Do ensure lifters are not pumped up when you measure though.

[TVRleigh]

You should not have to worry about the ratio as the head and rocker shafts are on the same plane, you only need the ratio if you want to convert the lifter gap to rocker height with is 1.6 - 1

how much was the heads skimmed. if it was just 10 thou then that will in 16 thou on the lifter. (so you may not even need a shim) depends on you setting before as they have a tolarance of 20-60 thou

Also smallist shim in the kit is 20 thou that will give you 32 thou on the lifter, or 16 if you have had the heads skimmed my 10 thou

[v8 racing]

TVRleigh said:

You should not have to worry about the ratio as the head and rocker shafts are on the same plane, you only need the ratio if you want to convert the lifter gap to rocker height with is 1.6 - 1

how much was the heads skimmed. if it was just 10 thou then that will in 16 thou on the lifter. (so you may not even need a shim) depends on you setting before as they have a tolarance of 20-60 thou

Also smallist shim in the kit is 20 thou that will give you 32 thou on the lifter, or 16 if you have had the heads skimmed my 10 thou

Not quite the case, the more you skim the more you lose the 1.6 ratio, its basicaly doing the same as putting a longer pushrod in the engine so you are losing the arc the rocker arm swings in, in fact all the rover v8's actually need longer valves to make the 1.6 ratio correct, if it was me i would go with the adjustable pushrods

[Chassis 33]

Thanks for the advice folks. Any advice on how far to go with the skimming, obviously it will affect the compression ration and the like and obviously I need to go far enough to remove the warping. Its a 9.35CR 3.9l "intermediate" engine and looking back through the comprehensive service history I got with the car theres nothing to suggest the heads have been skimmed previously.

Rob did you get the email I sent this morning?
Regards
Iain

[TVRleigh]

v8 racing said:

Not quite the case, the more you skim the more you lose the 1.6 ratio, its basicaly doing the same as putting a longer pushrod in the engine so you are losing the arc the rocker arm swings in, in fact all the rover v8's actually need longer valves to make the 1.6 ratio correct, if it was me i would go with the adjustable pushrods

You are correct in away but the heads and rocker steam are about about 3" and we are talking about 10-30 tho so I don't think its going to afftect the ratio that much as its about 0.1% or is it 0.01% it's too late to calc. also a longer push rod is at the end of the pivot, and shimming the whole pivot, and shimming affects the pivot centre.