Lash Caps [Archive] - Chevelle Tech

: Lash Caps


Sandy
Apr 6th, 06, 9:27 AM
It looks like I have to remove the Comp Cams lash caps off my BBC because they are "riding" on the keepers.

The overall thickness of the lash caps is 0.191 inches. This is made up of 0.082 for the effective cap thickness sitting on the valve stem and 0.109 for the depth the valve would need to go into the lash cap.

The distance from the keeper to the valve stem end is only 0.070 - 0.080 as measured on a few valves. So there is about 0.030 - 0.040 air between the valve stem end and the lash cap.

Has anyone else had an engine assembled with this problem ? Is it normal for there to be insufficient valve stem to properly hold the lash cap and still have a some clearance to the keepers ?

Are keepers with special recess for lash caps the normal installation or is this a fix ?

jbird
Apr 6th, 06, 10:37 AM
It looks like I have to remove the Comp Cams lash caps off my BBC because they are "riding" on the keepers.

The overall thickness of the lash caps is 0.191 inches. This is made up of 0.082 for the effective cap thickness sitting on the valve stem and 0.109 for the depth the valve would need to go into the lash cap.

The distance from the keeper to the valve stem end is only 0.070 - 0.080 as measured on a few valves. So there is about 0.030 - 0.040 air between the valve stem end and the lash cap.

Has anyone else had an engine assembled with this problem ? Is it normal for there to be insufficient valve stem to properly hold the lash cap and still have a some clearance to the keepers ?

Are keepers with special recess for lash caps the normal installation or is this a fix ?
The keepers I normally see do have a recess built into them for lash caps. But not all of them do. The shop I use uses the type with the recess with and without lash caps.

blazerbob
Apr 6th, 06, 11:42 AM
I've learned that you don't need lash caps unless running titanium valves. Need to check your push rod length to see if correct for valve train geometry. And of course the right size valve keepers-either 11/32 or 3/8!

GOSFAST
Apr 6th, 06, 1:52 PM
It looks like I have to remove the Comp Cams lash caps off my BBC because they are "riding" on the keepers.

The overall thickness of the lash caps is 0.191 inches. This is made up of 0.082 for the effective cap thickness sitting on the valve stem and 0.109 for the depth the valve would need to go into the lash cap.

The distance from the keeper to the valve stem end is only 0.070 - 0.080 as measured on a few valves. So there is about 0.030 - 0.040 air between the valve stem end and the lash cap.

Has anyone else had an engine assembled with this problem ? Is it normal for there to be insufficient valve stem to properly hold the lash cap and still have a some clearance to the keepers ?

Are keepers with special recess for lash caps the normal installation or is this a fix ?

Hi Sandy, it's really not an uncommon problem. It comes from tolerances between vendors, both with the valves AND the caps. Most racing valves have a .225"/.250" down keeper groove, and some have a .290", etc. The lash caps also come with different depths. Dave Crower has some "shallows", #86121S @ .055", and Comp's #621 are up around .130". The deeper the cap sits on the valve the less chance of it coming off.

We had made a collet setup years ago to be able to trim the height on the deeper caps to get to a desired length. For this reason we no longer use the Crower part number or any shallow ones. Thanks, Gary in N.Y.

P.S. You can grind those very carefully if it's a close fit, but you have to be careful not to "overheat" the piece. ALL these issues are what consumes much time when you do this for aliving. We try to "standardize" many components we deal with to keep the labor at a minimum. Doesn't always work out that way however. Wait till you try to fit (almost) 1.000" lift on SB's with the available valve notches and fairly huge cams, this is fun!

Sandy
Apr 7th, 06, 12:41 AM
Thanks for the responses.

Valve are the .225/.250 stem to grove distance.

My first inclination was to eliminate the lash caps, put back the two springs I removed, put the girdle back, make adjustments, get valve covers back on and drop the motor into the car. The easy way with minimal effort.

BUT......... lash caps are a good thing on a solid roller with high spring pressures, the old keepers have been beat on long enough and should be replaced with correct new keepers with recess for lash caps. Also chance to check all springs and install correct retainers. A lot more work, hopefully will be worth it.

Just checked some recessed keepers and found the depth of the recess to be 0.080 which is about 0.040 more than I need.

Try to eliminate as many modes of failure as possible.

I guess I should ask the question if anyone has had bad experience using lash caps and recessed keepers.

GOSFAST
Apr 7th, 06, 8:04 AM
Thanks for the responses.
I guess I should ask the question if anyone has had bad experience using lash caps and recessed keepers.

Hi Sandy, one more item I should have mentioned yesterday is the fact that there's usually a better "contact" pattern when using the caps. Many times it's hard to get the rocker arm wheels exactly where you want them. The increased surface area helps the situation by providing more "contact" area. Thanks, Gary in N.Y.

P.S. Quite a while back we were running into a situation where the rollers on the rocker arms would actually leave an "imprint" in the tops of some aftermarket valves, the lash caps do prevent this totally. And as was mentioned above, when using "Titanium" valves we usually don't incorporate the "hard" tips in the ends of them and this makes caps a must here! You can the rockers directly on these (Titanium's) as long as they have the hardened tips. As for the shop using the caps without the "recesses", it usually means they needed "adjust" slightly the installed height. We also use these on occasion, no problems.

Sandy
Apr 7th, 06, 10:56 PM
All of a sudden the dilemma becomes crystal clear.

My current retainers and locks are the 7 degree variety.

Just had a chance to see some 10 degree locks. They have a lot more meat on them than the 7 degree locks and have lots of space for the recess for the lash caps.

So new retainers and 10 degree locks with the lash caps and we are in business again.

I gotta wonder what engine builder would use too small of retainers with 7 degree locks, with the lash caps hammering on the locks with a solid roller ?

furball8994
Apr 7th, 06, 10:59 PM
All of a sudden the dilemma becomes crystal clear.

My current retainers and locks are the 7 degree variety.

Just had a chance to see some 10 degree locks. They have a lot more meat on them than the 7 degree locks and have lots of space for the recess for the lash caps.

So new retainers and 10 degree locks with the lash caps and we are in business again.

I gotta wonder what engine builder would use too small of retainers with 7 degree locks, with the lash caps hammering on the locks with a solid roller ?
Not one i'd ever deal with again!!!!!!!!!!