Race Engine Forum UK

Looking for some information here!

I am interested in making some valve tappets or the buckets that go on top of the valve/spring assembly. I would like to convert to a shim under tappet setup. My main goal is to decrease mass. I would like to know the following:

What material are these typically made of?
What kind of tolerence is there?
Hardness?
Manufacturing techniques?

There are a few companies that deal in parts like these, however I can't get much information from them. In addition to that, I cannot afford to buy anything from them. ($100+ per tappet!!) I think making them would be a great project and a good opportunity to test my skills. I have also been thinking of various coatings to use to decrease friction between the cam and the tappet, maybe something with a higher porosity to hold some oil...

Please let loose any ideas here!

Hello Jason

May I say - my strong advice is not to make these in volume yet, because you must have stringent QC protocols in place, without these claims over failure could cause you the most terrible problems. They are a very 'at risk' part in all overhead cam engine.
For your own use and for people you know and trust that's another matter.
I will give you the details but only privately by mail, please do not publish.

FWIW the adoption of solid buckets (with shim under) on many engines is a pointless conversion, only making shimming twice as time consuming and difficult. I have run DOHC and SOHC with quite heavy shims to over 12,000 rev/min with my race springs - and never experienced valve float due to excess valve train mass. The GC NHRA 2 liter 200bhp unit ran OE shims in the 4-4.50mm thickness range for two years.

As you know Jason - but just for everyone else - my posts are not intended to be 'lectures' BTW. I don't mind what anyone does, so long as I don't have to fix it after!!

GC

oh definately not for production! too high a risk for now. I am hoping to cut the mass significantly so I can run weaker springs as to rob less power. is this correct thinking? also do you think there is room for reducing the friction?

i'll be sure to send you the remains of my failed experiments!! ;) (at least in picture form)

I know the math here. FWIW my 'triple springs' are way softer than standard up to about 10mm lift. Can you run softer than standard with lighter buckets, well, maybe, you'll have to examine the valvetrain mass vs acceleration on the range cams you are considering. The worst problem you have to understand and cope with on racing engines is not mere F=m x a spring rate matching, but the spring inter-phase harmonics. These are awful on ordinary springs, pairs or single. The best springs these days are interference dual or triple (self damping), or at least rising-rate if space doesn't permit dual spings ( a lot of Japanese engines).

Is there any power gain from softer springs? My balanced answer is yes if they control the valve properly. Any energy loss that is minimised means more at the flywheel, maybe not always measurable as a single entity, but it all adds up.


GC

The tappet thing has always been rolling around there also and seems like it would be a fairly simple/complex job and a good opportunity to test my skills and implement some coating technologies.

As for the springs, seems like an interesting problem to play with. It will keep me on my toes for a bit-- I need a library here!

I am currently a student of physics and math which I chose because I didn't want to specialize! This is also the reason I am probably not going to attend graduate school, I won't focus on one problem for 3-4 years. Lately (since attending the F1 race last weekend) I've been considering building my own engine from scratch.

Hi, I found this site through my interest in building Peugeot race engines. With the help of a local valve manufacturer, I've designed long stem competition valves for 16V XU engines which allow the use of under bucket, top hat shims. I thought this was a neat way of converting from hydraulic to solid and saving some weight along the way. Peugeot race engines are a very small market in Australia, so I needed to keep costs down. The sketch below shows the general idea. The internals of the hydraulic bucket are thrown away. The shim makes contact with the bucket in the original place of the hydraulic piston. I'm also happy to share my shim mat'l and heat treatment processes via email.

Coincidently, I discovered Kawasaki Z900/Z1000 engines also used 7 deg. x 7mm collets. So the new larger diameter, longer valves also have single collet grooves allowing the use of the Z900 collets. It gets better. Z900/Z1000 are big business drag bike engines in the USA. So there's plenty of cheap parts available. Titanium retainers and quality interference double springs are very cheap. So it's possible to shed 30g very cheaply and reliably.

What about changing to buckets/small shims because one needs the actual width due to high lift camshafts?

Also, from lifting the std Fiat Items and comparing them with a regular Alfa "Nord" lifter I could probably shed well over a kilo in weight in a 16v engine by going to shim-under-bucket. And that weight is pretty high up/forward in the car and moving...

Mats, hi

you don't need bigger diameter shims on 8v or 16v TC up to any cam lift I know.
It is - in my view - a very bad idea to get rid of the tappet-on-the-top really, just makes shimming twice as time-consuming, and if you change the cam and the solid buckets are worn on top you have to replace them. It's a fantastic system that, with the right valve springs - you're not going to see an valve train mass problems.

As for going faster by losing that weight, my advice is - go on a diet.

GC

Well, about the weight you're right of course.
If it's about saving time shimming the valves I have to ask, how often do you re-shim the engines you run? I have had loads of Alfas (Nord and 8v TS) and have never had to change any shims. Driven hard and often, measured regularly.

I'm just thinking, in an effort to build a very hot engine, would it not be beneficial to use as light valvetrain components as possible? To use the std items seems like cutting corners to me. Alu/titanium retainers and a very heavy tappet/shim on that, doesn't seem right to me.

Mats, hi.

As I said - It's a fantastic system that, with the right valve springs - you're not going to see valve train mass problems.

You have to be running very high rpm to justify the cost of lightweight parts like that, no-one does it just for the sake of it. Me, I have enough trouble trying to convince people to spend the money on say, balance their crank flywheel during rebuild. And I've run OE caps and buckets to engine speeds most people will never see in their lifetime.

If you have a high budget race engine and you can get titanium or alloy valve caps, then use them if you want. Of course lightweight is better, but you have to watch the design and keep an eye open for wear. As with any racepart - lightness costs...

As for the shim & bucket, I used standard buckets and shims on the GC 2 liter 46/40 and 45/40 valve NHRA (short oval)units with 12mm valve lift. These engines, as I have said many times on the site, ran to 9500 consistently on every short oval event, over and over. I did other units in the mid 90s, 1600, 1800 hydroplane eg., that ran even higher.

I recommend road cars reshim after 500-1000 road miles from build, as for race engines after first race and check periodically. They should not really move. If they clearances are getting bigger or tighter there is a problem in there, valve and seat or cam/shim, so it's a useful check.

GC

Ok. Cost vs benefit it's not worth it, got it.

I'm new to the Fiat engines so I really haven't read all the stuff there is to read yet.

I was referring to the 16v engine by the way, don't know if that makes a difference.

Relatively speaking it makes even less difference on the 16v Fiat, the valves are about 60 gm compared with 80gm or so on the 8v.

GC

What do you mean, the valve/tappet weight ratio should be larger then I guess since the valve is lighter? One complete tappet with shim is about 175 gram from my measurements, that is just incredibly heavy compared to a stock 8v Alfa bucket + shim.

The 16v and 8v Fiat have the same valve springs - so what I mean is that the overall weight of the valvetrain mass is less on the 16v with the same bucket, ie: less need for light parts.

GC

Oh, I see. I hope you don't mind the Fiat-newbie questions. :)