Took my daughter's car to test and tune last night. Its a street and strip car with a pretty fresh 440. First time out with the headers - car was suffering from bad reversion with the stock 383 exhaust manifolds.

Car was inconsistent in mph - 92 to 95 mph in 6 runs. The runs were all with very short time in between the runs. She ran a best ever 14.19 on the 6th run. My wife and I waited in the pits and she did not come back from the run.

Bottom line - when she got on the return road the car overheated (not bad - spewed some out of the overflow catch can). She also said the oil light came on and the car died.

I do have a fuel cutoff on low oil pressure, so I figured that killed it. When I started it up, it made a little racket and died. I tried again and it was obvious something was wrong with it and we definitely had no oil pressure so I towed it home.

Pulled the distributor and had resistance in the oil pump so I pulled the intake. I was not surprised to find a lifter had fallen out. I was stunned to see 2 lifters out (#2 and #4 cylinders). The jam nuts were loose on the Harland Sharp rockers.

Somehow I dodged a MAJOR bullet. Seems like no real damage. One pushrod cup is a little banged up - I will replace both pushrods (they are not bent) and I think I will go back to the Crane ductile iron rockers.

So why would 2 rockers loosen up? How could it happen at the same time? Seems too much coincidence to me. I do know preload was on the loose side.

Opinions?

I have had that happen with alum rocker arms, never with the Crane iron rockers. My solution was to replace the jam nuts with ARP 12 point nuts that have a wide flange made on them. Sorta like having a flat washer made on them. This incresses the locking surface of the nut to rocker by a bunch, with out having to over torque the lock nut. You can buy them at Summit in two different wrench sizes (7/16" & 1/2") in packages of ten. Since I went to these nuts, I haven't had one back off.
Something else, don't over thighten the jam nut either. This will can cause the nut to get loose or stess the adjusting screw to the point of breaking, and it will break right where the nut meets the rocker, then the top half of the screw and the jam nut will fall off and the rest of the screw will back out. Then the push rod jumps out followed by the lifter and you what happens next.
And yeah, I'd say you dodged a big one.

Brian

i've had jam nuts come loose as well. now days i always torque them down just to be sure. if any should come loose after that they go to rocker arm heaven.

Did you set the rockers with a cold motor or after it warmed up? If cold you should always reset them when warmed up, Aluminum expands 8 times more than steel when hot, the adjusters don't stretch as much as the rocker arm expands so you end up with a loose adjuster when cold, pretty soon your in trouble Always reset them when hot(tighten the adjuster nuts up), even the ductile iron ones

Dan @ performance only cleans all adjuster screws and puts blue (I believe) locktite on them. He did this on a set of rockers I bought from him and to this day, when I have to adjust them, they are snug even when loosened up.

Make sure the pushrods clear the heads too.

Well picture is getting clearer.

What I do know is that it looks like the preload was not properly set, and is inconsistent. The push rods are too short and the adjuster studs are not protruding thru the nut (not a good situation for keeping the nuts tight). At least 2 threads in the nut are showing.

Plan is I am sending my Crane ductile iron rockers to RAS to have brass bushings installed. They will also banana groove the shafts. Will get a new set of pushrods once I figure out the correct length for the Crane rockers. Will keep the Harland Sharps for spares for the race car.

I expected the car to go 13.75 in good weather. Friday it went 14.19 (fastest run ever) on the last run. Will be interesting to see what it runs when the valves actually open and close properly. In a very quick inspection found an exhaust rocker not only did not have preload, but had 0.040 lash!

On the pushrod length most of the pushrod makers and rocker arm manufacuters will tell you to shoot for between one and three threads exposed on the adjsuter screw under the rocker arm body That works real well for me

Can always use a thick lash cap to add threads above the rocker..but for that setup I might run a clean set of stock rockers...

If you had them loose on the pre-load, you probably floated them. Be sure and check rod bearings, because no oil on top means no oil on the bottom. Watch r.p.m.s in burn out.

We can bush & radius the tips for $15.00, $6.00 extra for new adjusters & 12 pt nut.

I emailed them on monday about bushing a set of TA rockers and Tuesday they responded with the above price...to give ya an idea.

oh...when they bush the rockers do they remove much material from the rockers (thus weakening them in their weakest area)? Or do they just turn down the shafts to fit the bushings?

Cab,

You know plenty more than I do about building racing engines and getting down the strip, but whoever put the "8 times" into your head was DEAD WRONG!

Here are coefficient of linear expansion for:
aluminum 12.3
cast iron 6.0
steel 7.3

Units for all are millionths of an inch per inch per degree F.

So that means aluminum expands 2.05 times as much as cast iron and 1.685 times as much as steel. This is part of what I do for a living, and I take it seriously.

These numbers are facts. You can talk about "8 times" until Jesus comes back, but that won't make it right. Whoever told you that misinformation in the first place should be ashamed of himself. I'd tend to look at whatever else he said with a wary eye.

R.

Can happen with hydraulic lifters..
Usual problem is the lifter pumps up due to some garbage buildup in its bleeder hole..
Pressure builds and blows out the pushrod, then oil pressure drops qwickly once the lifter is out of the hole.

Just my $0.02...