steel or aliminium rockers?

[Will Reeve]

I've just unearthed a spare set of cylinder heads in the garage. These are fitted with aluminium rocker gear.
My original engine has steel rocker gear.
The new engine came with only one side having rocker gear (it was an eBay purchase, it's aluminium!)
My question is what is the best rocker set to use, the steel which has served me well in the old engine, or the aluminium which looks in good condition. I will strip down and check for wear but they all look OK.
I presume aluminium is lighter and allows higher revs but not so strong to push dual springs and wears quicker?

[sidecar]

I've just unearthed a spare set of cylinder heads in the garage. These are fitted with aluminium rocker gear.
My original engine has steel rocker gear.
The new engine came with only one side having rocker gear (it was an eBay purchase, it's aluminium!)
My question is what is the best rocker set to use, the steel which has served me well in the old engine, or the aluminium which looks in good condition. I will strip down and check for wear but they all look OK.
I presume aluminium is lighter and allows higher revs but not so strong to push dual springs and wears quicker?

As far as I know the standard ones are the ali ones, the steel ones are after market ones. Maybe Federal Mogal or something like that. Or they could be Volvo jobbies

The ali ones are OK with all the valves springs and will run to around 6200-6500 before they become dodgy. (As does many other components around the same revs)

You need to be really careful when buying steel or ali replacements, many brand new ones are a very sloppy fit on new rocker shafts, this ain't good news for the oil pressure or anything else.

Are you sure that your steel ones are not in fact just oil stained ali ones?

[spend]

Ally is fine, its just the small steel rocker pads can fall off.. Obviously solid steel does not have this problem but is heavier.

I'd go out on a limb and say that hot engines might be contributory to breaking the bond between pad and arm? Always seems to be at the back of the engine from what I hear.

[Will Reeve]

Tested the steel ones with a magnet! I've not had them hand in hand but I guess the weight difference is considerable. What am I looking for when assessing a rocker set?

[Will Reeve]

Steel:



Ali:




Both sets "look" OK. Decisions...decisions!

[sidecar]

Steel:



Ali:




Both sets "look" OK. Decisions...decisions!

Yep they are steel!

[sidecar]

How radical is the cam that you intend to fit and what sort of RPM are you going to run the engine up to are the normal sort of questions that would help you decide but equally it is still confusing.

A radical cam with a rapid opening rate will put more load on the rockers so steel would be better. But steel is heavier so you need stronger valve springs which places more load on the rockers and pushrods....round and round the problem goes!

One thing that may decide for you is the condition of both sets of rocker gear. The RV8 seems to chew this stuff up so I'd check out the condition of the shafts and the holes in the rockers that the shafts run through. If the rockers are sloppy on the shafts then the whole lot is knackered. Check out the the cups and the pads on the ali rockers to.

Of course if both sets are in good condition then you are back to square one!

[Will Reeve]

Thanks guys. I am building a stock 3.5, lightly ported heads, new Piper 270 cam, new lifters, new push rods and pre-load shims. Quite happy with a 6k rpm rev limit.

The steels were out of an engine with adjustable push rods, Rhodes lifters and a Viper cam, not sure if the valves were double spring will have to check.

I am veering towards the ali. set as long as they are Ok wear wise.

[sidecar]

Thanks guys. I am building a stock 3.5, lightly ported heads, new Piper 270 cam, new lifters, new push rods and pre-load shims. Quite happy with a 6k rpm rev limit.

The steels were out of an engine with adjustable push rods, Rhodes lifters and a Viper cam, not sure if the valves were double spring will have to check.

I am veering towards the ali. set as long as they are Ok wear wise.

If the ali ones are in good nick along with the shafts then they will last for ages, they knacker up when people don't change the oil.

I run a Piper 285 RPI cam with ali rockers and double springs. (Biggers valves too). I run standard lifters from RPI. (Preload set to 20 thou)

Why don't you run the adjustable pushrods, they are much better than shims?

[Will Reeve]

Holes in the heads are too small and I don't want to drill them in-situate! Ironically I've just removed one head to have a look at the cylinders. I was just going for a standard build really. Turned into much more than I was bargaining for!

[topcatcustom]

If the ally ones are used- slide a couple off the shaft and examine the shaft for wear. The minute iron filings in the engine oil from general wear embed themselves in the soft ally rockers around the shafts and wear the shafts down just like emery cloth. If the shaft shows signs of wear- you may as well chuck the rockers as they will just chew through any other shafts you use them on.

Steel ones- as mentioned it appears that a lot of aftermarket rockers (all the steel ones) fit poorly on the shafts as the holes are too big and are often too sloppy to be used.

I'd examine both sets and weigh up which is best based on the above info!

[SuperV8]

I would say go with the Ali if they are in good nic.

Check for wear on the bottom of the shaft.

Might find the thread below usefull.

http://www.v8forum.co.uk/forum/viewtopi ... c&start=15

Tom.

[ppyvabw]

Holes in the heads are too small and I don't want to drill them in-situate! Ironically I've just removed one head to have a look at the cylinders. I was just going for a standard build really. Turned into much more than I was bargaining for!

It's possible to drill the holes whilst the engine is together if you are careful.

Smear grease over the valley to catch swarf. A greasy rag stuck down in the middle to stop any getting in to the engine and a helper with the hose bit on the hoover. Tape over the ports.

[sidecar]

Holes in the heads are too small and I don't want to drill them in-situate! Ironically I've just removed one head to have a look at the cylinders. I was just going for a standard build really. Turned into much more than I was bargaining for!

It's possible to drill the holes whilst the engine is together if you are careful.

Smear grease over the valley to catch swarf. A greasy rag stuck down in the middle to stop any getting in to the engine and a helper with the hose bit on the hoover. Tape over the ports.

I found that I only had to do each hole at either end of each head, all the other holes were OK. I did not drill mine, I made them oval with a rat-tail file.

Also it depends on the diameter of the pushrods, mine are from Real steel, I think that they are made by Crane.

Pete

[Will Reeve]

Well. On a quick check I noticed that the little notch on the rocker was pointing down...bad news it should be pointing up.
Disassembly revealed:



Quite a bit of wear on the shafts, you can feel it with a finger nail.

Rockers are from 1978, look like a rub with some 1200 grit will bring them up OK. Advisable?