Valve Lash Repair - Lash Logic

At this point it might look like all the roller lifter problems have gone away. Unfortunately, that's not the case. Very often-and mostly with crate-style motors-the pushrod, spring, or both will go into a small, but significant, resonance. This momentarily causes the valvetrain components to separate. At this point, the hydraulics will do exactly what they are supposed to do: take up the clearance. Result-the lifters pump up a little and hold the valves off their seats. Believe me, this takes a big chunk out of the power. At this point, although a hydraulic cam is not supposed to have lash, we have a big lash problem. If the lifter is set right at the top of the travel, it will collapse. If it is set at the bottom, it will pump up (don't you just love these hydraulic rollers and the guys who make the rules that insist you have to run them?).

So what are the fixes? If springs can be changed, then go for stronger springs and about 20 pounds more seat preload. This should stop the component separation. Now the plunger can be set close to the bottom and the desired results noted. But before doing this, check that the oil is free to pass through the lifter in the normal way to lube everything. I have seen some lifters that at the bottom of the travel shut off the oil, thus burning out pushrod ends and rocker bearings.

Let's say you have a crate motor and cannot change springs or preloads. Then you are snookered unless you did what we did last year when running our No. 64 car at Hickory Motor Speedway. This was a Late Model car powered by a crate motor. We hired an oil specialist to brew us an oil with some long chain polymers to seal the lifters better. With this oil, we lashed the lifters at the top of the travel so they had about 0.002 (two thousandths) clearance. Typical results produced an 8hp increase, although when tested against some super race oils intended for solid followers (flat or roller), the difference was as much as twice that figure.

These high-tech oils were doing exactly what they were supposed to do-be super slippery and zip through the engine clearances like a knife through butter. The result was those less than perfect hydraulic lifters collapsed even more readily. I did not call all the high-performance oil blenders out there, but of those I did reach, none (at the time of writing) had hydraulic roller cam-specific oil. This means if you want some oil like I used, you will need to do your own research or call Ultra Pro Machining.

OK, so much for roller hydraulics. At this point, flat-tappet hydraulic cams will look like a walk in the park. For these to work, make sure you are not using fast bleed-down lifters. What falls into the fast bleed-down category could be a set of cheap lifters that are supposedly stock replacement. My advice is to buy from a reputable cam company such as Comp, Crane, Crower, or Isky. Make sure you are getting the slow-bleed lifters when you order. Next, adjust the lifters so there is about 0.002 clearance when the plunger is at the top of the travel. From here you should be good to go.

Look through any auto manual and you will find a chart giving the order in which the valves need to be lashed in. It usually goes like this: Adjust No. _ when No. _ is fully open. This is OK, as it usually means the least number of turns of the engine to get around all the valves. But firing orders vary and often it is difficult to remember what order all the valves should be done in, so here is a universal method that works best.

First understand that cams are not perfect, and although lobe base circles should not have any runout, they often do. Add to this that some cams can have relatively long tappet ramps, and we begin to see a need to make sure the lifter is positioned on the base circle before any adjustments are made. Here's how to achieve this. First turn over the engine to the point that full lift is seen on the valve to be adjusted. Now rotate the engine one full turn. The lifter is now right in the middle of the cam's base circle. Now adjust the lash to the required amount.