Help required please - V8 Cam Followers

[Pilo-Wedgebits]

Hi guys,

Just having the V8 rebuilt at the minute by a mechanic friend of mine and he says its worthwhile replacing the cam followers.

There appears to be various sets available though, the 3 I have found are as follows:

1) High Rev Lifters
2) Bleed Down Lifters
3) Standard Hydraulic Followers

Any of you chaps got any experience as to which are the best and any recommendations.

Thanks

Shaun

[ed_crouch]

The Rhoads high rev ones claim to stay "stiff" (ahem) up to higher engine speeds. Basically, as the engine speed approaches 6k, the standard lifters start to bleed down to reduce valve lift and act as a sort of rev limiter.

By fitting the high rev ones, you are getting a little more torque at the top end (as long as the rest of the engine is up to it), but you will LOSE THE REV LIMITER!

Ed.

[TVR 3X]

You can easily add an electronic over-rev limiter that can be adjusted or totally removed for the odd track day.

I think mine is Micro Dynamics <http://www.cars-gb.com/microdynamics_m.htm>

Russ

[rev-erend]

Best - well the hi rev lifters..

But the question is - whats the cam .. if its a low lift cam .. well no point in fitting hi rev lifters.

I'd give an expert like v8 developments or v8 tuner a call and discuss.

[adam quantrill]

If you are replacing the cam then yes, get a new set, in fact it's compulsory.

If not, then no, don't bother, unless one or more lifters have a problem, like a pitted face, or square wear pattern. Even then, only replace that lifter, and leave the rest alone, as they will be bedded into the cam.

[GreenV8S]

The idea behind Rhoads lifters is that they collapse when the valve is open. At low rpm this has the effect of reducing the effective cam duration, which can be useful if you have a leary cam and want to drive it gently. The disadvantage is that they sound like a bag of spanners. Unless you have a really strange engine you shouldn't consider fitting these.

Normal lifters suffer from a problem called 'pumping up'. The lifter is designed to adjust itself to maintain a small valve clearance. At high rpm the lifter is relatively lightly loaded at peak lift and the lifter can gradually winch itself out, reducing the valve clearance. If this happens then after a few seconds the lifter can open so far that the valve doesn't close fully, which will result in a very noisy engine and loss of power. If you drop the revs the lifters will gradually close back to their normal positions so it isn't a major problem. However, if you fit high rev lifters they're less susceptible to this problem. This is well worth thinking about if you're expecting the engine to spend much time over 5000 rpm. Regardless of which type of lifter you go for, it's important that you set the preload. The preload determines how far the lifter can extend when it pumps up, so it's important that this is not excessive, but it must be enough to allow the lifter to accommodate wear and thermal expansion in the engine.

Hope this makes sense.

[TVRleigh]

Just to add a spanner to the works, you could allways go solid lifters, but then you would need adjustable rockers, pref roller ones.

[Wedg1e]

TVRleigh said:

Just to add a spanner to the works, you could allways go solid lifters, but then you would need adjustable rockers, pref roller ones.

...or you can fit adjustable-length pushrods.

My engine runs a high-lift cam and standard hydraulic lifters and will go well past 6000rpm for short bursts, though it has to be questionable how much extra power you get by so doing. So I don't, generally