Valve Lash Caps,when Are They Needed?

[rusty duster]

I am building my first roller cam motor and was wondering if i needed lash caps.The motor in question is a 540 inch stroker;720 lift cam;440-1 heads;comp springs#996.When i bought the cam and springs nobody mentioned lash caps.I sure would appreciate hearing from any engine builders out there.

[jelsr]

Lash caps are recommended at anything over .650 lift.

[pishta]

caps make your valve stem bigger so the roller tip or the rocker tip wont "roll" off it at large lifts

[biggerhammer]

they don't just widen the tip of the valve, they also add to the overall height of the valve, so be sure and check your geometry to avoid any problems

[sanborn]

Lash Caps are a rocker geometry "Correcting" tool. They are used to get the tip of the rocker in the correct position on the top of the valve.

The rocker should be .025" to the intake manifold side of the valve centerline at rest. As the rocker goes through its lift motion, the tip moves past centerline to the exhaust manifold side of the valve centerline and at full lift, the tip should be at approximately .025" to the intake manifold side-the same place on the valve it was a rest.

All this sounds easy, it isn't. In order to get this, sometimes the rocker shaft must be raised/ lowered and in extreme cases relocated(especially on W2 or race heads).

If you have a rocker tip about to run off the tip of the valve, you have a disaster waiting to happen. Don't use them unless you have to. They do come off!

[b-1ken]

I have two 499 B-1 engines, one with lash caps and one without them. The one without the caps is the engine that I built for myself in 1997. It has an advertised lift of .765" with T&D 1.7 rockers. I have run that engine for 6 seasons, and I've had no real problems with the valve train (exception is a broken valve spring about once a year and a broken exhaust rocker.). The engine with the lash caps was originally built by Koffel. The one thing I don't like about them is if you have a problem they can fall out and then you really have a lot of clearance and the pushrod will fall to one side. If you use them, you better carry spares because if you lose one putting on the rocker assembly you're screwed. Believe me, it can happen. This season I am building a new engine with Titanium valves and I have to use them on that and I hate doing it. Normally, under these conditions I'd buck the consensus and go my own way, but not this time. Not yet at least.

[67ster]

The only time I use them is on a titanium valve . I have seen them used to "correct " sloppy geometry .

[sanborn]

Maybe I am wrong about this; but, every titanium valve I have ever owned or seen has a hardened steel tip on it.

The only time I have ever used lash caps was to correct poor rocker geometry. And even then it is considered a "temporary" fix.

[DartGT66]

I have used them. Don't actually have a particular reason for it; I have never checked the rocker geometry in any of our engines. If nothing else, they make removing the valve easier because the tip is "protected" by the lash caps. I have not had problems with them, if everything is fine in the valvetrain there is no way they should get off between the rocker and stem. If that's the problem, I would say that you have the vavles bouncing in the seats or something like that. However, everytime something has broken in my valvetrain (two rockers, one adjuster) it has been a fun "who finds the lost lash cap" game. I have lost one completely, never found it even during the tear down.

[b-1ken]

sanborn wrote

Originally posted by sanborn
Maybe I am wrong about this; but, every titanium valve I have ever owned or seen has a hardened steel tip on it.

Hmm ... this IS interesting. When I read your post (sanborn) I immediately ran down the hall and got out my Titanium valves and checked them out. Upon close inspection, it is apparent that they DO have inserts. I can see a slightly different color starting just below the lock groove. I checked that area with a magnet and the magnet didn't stick at all. I know that not all steel alloys are magnetic, but I thought this one would be. I bought an extra stainless steel valve as an emergency back- up and that valve IS magnetic (entire valve)- (only austenitic stainless steels are not, like 304, 316 etc.). There is a tag on the box that states "Titanium and custom stainless steel valves require tip protection unless a steel inserted tip is already installed". Maybe I'd better call Manley and ask, but sometimes the manufacturer (or in this case retailer) is only guessing as well. I'd rather not use lash caps if I don't have to. I've seen too many of those friggin' things laying on the head under the valve covers. Also, their a pain in the ass when it comes time to put the rocker assembly in place leaning over the fender at the track (fall in the weeds).
Thanks for the insight. Ken B.

[rusty duster]

thanks for all the replies,you guys have really shed some light on something i was not familiar with.Right now i am thinking on not running them and keeping a close eye on the valve tips & lash adj. Called comp cams twice and got two different answers. I usually check the valves every time i go to the track,so if something does start to go wrong maybe i can catch it in time.Just cant wait to put my foot down on 800 horses!

[6 packin]

Hey
I have seen them in use before, But whats the installation process? Do they just simply push on/ Or do they get pressed on? How tight do they fit the valve stem.; I check on a set but all I could get is .060,.080 thickness. I would like some .020 thickness, are these avaliable? And part numbers please!

[sanborn]

Two or Three miscellaneous comments:

Again, all the Manley titanium valves I have used had hard steel tips. But, all I have used were the 5/16" stem, 5.560" long, 2.15 and 2.18" diameter. The tips are about .100" thick. You can see a distinct difference in the valve.

6 packin, they just push on, some are rather tight. I don't think a cap is made in .020" thickness-I am afraid they wouldn't hold up. But I have seen .060", .080" and .100" thicknesses. And, I buy all our valve train components from Precision Products in Asheville, NC or CV Products in Charlotte.