The V8 Owners Forum -

Right new topic! Need some help please ppl!

I am going to be using Real Steel's Blower cam, which has .480" max lift (seems a lot!!)

My heads are the later 14 bolt EFI ones, before the neoprene seals came out (and no I would NOT rather have newer heads as the combustion chambers are so much smaller!- Need the low compression for obvious reasons!) I am also using composite head gaskets to further lower the compression ratio.

Am I right in remembering that in Des' book he says that these 'mid' period heads have the most capacity (in std form) for valve lift?

So my question(s):

1st, will I have to mill a little off the top of my valve guides or can anyone tell me how far they should stick out so I can measure them?

2nd, with the composite gaskets being (.5mm?) thicker I guess I should machine down my rocker pedestals or the bases where they sit- but this will undoubtedly upset my geometry- so would it be less hassle to get some adjustable pushrods, and how strong are they? Don't have much faith in tiny threads in thin tube having to massacre double valve springs at 6000+ RPM!!!!

Oh, just to get this off my mind too- 3rd, double valve springs will go straight on won't they? i.e. no machining required?!

Help much appreciated as always guys, TC.

The only way to know if your valve train components are going to clear each other is to mock up and measure, sorry but unless it's so near standard that it is just a change of valve springs you need to measure it. a set of checker springs are about £5 and make things easier.
You are going to have to mock it up to check your geomitry any way. Try and avoid ajustable push rods if you can as they are heavy. Your first go at sorting the geomitry should be with lash caps, they are cheep and can be bought in different thickness' and you don't have to machine anything (shin the odd 5 thou with pedistal shims), then try a checker pushrod and get "cusom" length ones if you have to.
point 3, don't know, there are many different "double valve springs" so can't say.
Mike

kiwicar wrote: set of checker springs are about £5 and make

They are free if you have an old rocker shaft with the springs still on it! Cut each spring in half otherwise they are a bit too "springy" !

I agree, you've got to measure this stuff, it's a PITA but then so is wrecking your valve train!

As Mike and Sidecar say. You will have to do the testing re valve lift from the cam and valve clearance.

The heads will take stock double valve springs no probs. But if you are going with a Blower cam from RS I can be pretty safe in saying that you will need to skim some metal off the valve guides. I binned my stock double springs and used the stronger RS double springs. These need to be set to the correct fitted height so they have the correct amount of tension to keep the valves closed for higher power applications. They also need to be fitted with the RS caps and colletts. FYI...While I had my old style heads at RS, they machined the valve guides to take the modern seals.

Adjustable push rods... I have them on my latest build. And they aint all that for what I do with my car. I should have stuck to shimming the pedestals. I bought the kit and had to spend money having them trimmed to length and had the insides opened out to take the right size ball end for the Rhoades lifters. Cost of rods, ends and machine work was over 200 notes. Cost of a couple of shim packs about 30 notes.

A quick way to check without having to use check springs is to take the max lift of the cam and then multiply by the rocker ratio so you know how much the minimum distance should be between the top of the valve guide and the bottom of the spring cap. Take a valve spring off, refit the cap and collets and get someone to hold the valve shut while you stick a vernier in the gap between the top of the guide and the bottom of the lip of the cap on the valve stem.
I did this with my early heads. I had the heads skimmed 10 thou as well. I used comp gaskets too.

Back then I didnt consider the possible issue of valves fouling the pistons with this amount of lift because I didnt know any better. But luckily it was ok. I raced that engine for nearly 3 years before going 4.6 on the new build.
But what I did do was to make sure I set the preloads to 20 thou or a bit less. I dont mind a bit of tappet hiss at idle.

Using comp gaskets will slightly lower the CR, but you aint worried about that are you? It also gives you a few thou extra to reduce the risk of valves fouling the pistons.
Dont bother messing around with milling the pedestals or pedestal bases on the heads. Keep that all standard as you may well cause more problems than you want to get involved with.

So to summarise:
The blower cam from RS is a nice little jobbie. I'm on my 2nd.

Make sure you have enough gap between the top of the guides and the bottom of the valve cap shroud.

Dont forget to include enough clearance here to allow for the thickness of the rubber washer seal as well, otherwise on startup they will just get cut off by the spring caps and you will end up with very tiny seals and some loose rubber rings floating around inside the springs.

Add to this clearance measurement 30 thou as a bit of insurance.

Set tappet preload to 20 thou max.
If you check all the tapets one by one you will find the "mean" gap with no shims. Then work out what pedestal shims you need to get you into the safe 15 to 20 thou band that you want.

I know this info may well vary from stuff you find in the books. But I've found this method actually works on my race engines with very good results and a reasonable margin of safety.

I'm no expert. I've just learnt the hard way from day one with my Rover V8's. I've got quite a big box with bent pushrods, melted pistons, flattened spark plugs and other damaged components from my R&D years.

Disclaimer!
I'm no expert. Your investment may go down as well as up. Just like your pistons if all is well

Perry

Excellent thanks Perry, (& Pete & Mike!)

I shall get my cam & lifters etc & go from there, am I right in thinking that when mocked up a 10thou gap under a pedestal will make approx 15thou preload when bolted up?

I was intending on using the RS cam as previously stated, and Crane DV springs and retainers from V8T as they are cheaper and still a renowned make obviously! Also like the look of the HD pushrods from V8T? Look strong, simple & light... if someone can confirm!
http://www.v8tuner.co.uk/product.php?id=80

Also Perry do you run the blower cam dot to dot as such or advanced/retarded? I am only going to use about 6psi boost and real steel may be able to tell me when I order it but a second opinion is always good!

Thanks all, TC

The V8 Dev website shows a good method of setting up the preload with shims. I personally think that shims make a fairly poor geometry even worse but each their own I guess!

TC
Sorry to tell you this but from my experience the crane double springs will not fit straight on. The inner spring fouls on the support around the valve guide causing coil bind on the inner spring. When it binds you bend a few pushrods.

I had to have the guide support machined away and that cured it. I have a bit more lift on my cam than you are using so you might not have the same problem. Hopefully you wont but bear it in mind mate.

Steve

Thanks Steve- can someone tell me which- if any- dvs & retainers will go on a std head?

topcatproduction wrote:Thanks Steve- can someone tell me which- if any- dvs & retainers will go on a std head?

I don't think there will be any. The outer spring has to be pretty much the same diameter or it wont sit on the seat that is there. The boss at the seat is fairly close so it keeps the spring in place so there is virtually no space left for a spring to sit inside even allowing for the slightly thinner coils due to being lighter poundage. The original rv8 heads had double springs and the spring seats were different for this reason.
Its not a huge job to machine them but it does take time and thats what costs in machine shops. Unless you can find someone with a CNC and the program already done, possibly one of the big Rover guys like V8 dev or Real Steel.

TC
I run the cam at normal setting.

Does anyone know what type of cutter is needed or how they reduce the diameter of the centre 'post' around the guides for fitting DVS'?

End mill and rotary table.

katanaman wrote:End mill and rotary table.

Well price first- then price for rotary table! Making up a jig to hold the seat square on to the tool would be fun too!

With the valves all in there are one or 2 stems that are slightly higher than the others- is there anything that can be done i.e. grind the end of the stems down a little or do the lifters just have to take up the extra?

I am still tempted by adjustable pushrods but aside from the price the fact that they have a measley fine thread that looks ready to strip also puts me off! Especially with double springs...

TC
John Eales charges 40 quid to machine a pair of heads so the valves guides are lowered to suit the cam, and this includes reprofiling the tops of the guides to take the knock on type seals. He is doing a pair for me next week.

If your valves stems are different heights. Some of the valve seats are worn more than others. Not unusual!!

You need to take the lowest valve stem on each head and use this as your datum for setting pre load and shimming etc... Its not ideal, but it will work ok.

The valves which sit a bit higher will have a tad less lift. The main thing is to make sure that you maintain your min safe valve to piston clearance on the valves that sit lowest in the heads. I think its about 68 thou.

Perry