There was another thread about smallblocks and lash settings, I wanted to get dome real hardcore racers to respond to this.

I was playing around in Autocad where I modelled a "perfect" 45 degree lifter bore essentially parallel to the cylinder bore and the pushrod perfectly straight and on the bore centerline of the lifter in all directions going to an imaginary Perfect Rocker.

Of course it's not but I do know that pro stock racers picked up a lot of RPM by modifying the blocks and even shifting the cams and lifter bores in order to get the pushrod as short and in as straight a path as possible.

That brings us to the 59 degree which means the cams lift has to compensate for a 14 degree offset and this results in an oscillation of the pushrod as it doesn't move in anything close to a straight path from the lifter cup end or the rocker fulcrum. The loss of actual cam lift on say a gross 600" lift (1.5 rocker with a .400 lift base circle) looks to be in the .030" loss of lift...not even considering lash.

My 'Theory' is a small block 59 would benefit from as little slack as we can get away with, That oscillation "wobble" (even at 1/2 the crank speed) would be likened to trying to drill a hole with a bent drill bit. To my knowledge Hot lash measured at the valve stem for say a SB Chevy with obviously better pushrod geometry and therefore a better chance at a true "as advertised" rocker ratio would be proportionally looser on a Mopar and allow the pushrod to "rattle" more between the rocker cup and the lifter cup.

My cam is listed as .016/.018 HOT so with aluminum heads I was setting the feelers (-.006) so .010"/012", (which should be ~.008) at the adjuster but of course that will grow between the cups as the motor heats up.

I'm just wondering if anybody has run them significanly tighter and seen any better results. It doesn't "seem" like a lot of "wobbling but I'm thinking every thou you can run it tighter between the cups without binding the springs might allow it to rev easier, if not noticably higher. It's like to me the small block has an extra degree of "slop" in the system.

Back in my early 20's I had a w2 340 and I turned it 7600 with an Isky 3/8 mile circle track cam (no doubt based off a chevy) , back then i was more worried about the clutch exploding than what my Ductile iron (non roller) rocker were doing!! But after a year or so of hard use you could see those rockers really took a beating!

When I had my w9 sb, it had the same lash, 16-18. I set them 0.06 tighter. Didn’t beat up the valve train. Pretty quiet too.

On almost every motor I build with a semi loose lash cam gets .006 to .0012 tighter lash hot, I do set them tighter (.006 to .010) cold with aluminum heads and them run the motor long enough to get the heads and block near 200+F coolant temps and then reset them to .006 to .010 tighter than the cam cards calls for, on the tight lash cams, under .018 hot, I'll try from .004 to .010 on them also at the track to see what that cam and motor likes the best

Thanks Cab, I'm going to set them at .008 and let them rip figuring I gat another .004-.006 for "growth' from the aluminum heads. I used to set them at .010 I and .012 E to get .016/.018 and I just feel that's too loose for a 59 degrees, but that's probably fine for a big block (or anything with straighter geometry).

Something else I do is I run a hollow pushrod and (I presume) they fill with oil as the motor is running....so I think they have a little hydraulic dampening (shock absorpsion)...even if they are a little bit heavier, also any degree of lubrication passing through the pushrod hopefully aids in reducing the wear. i only turn it maybe 7200 max and everything seems sweet up there.

My current cam called for .014 and that is what I run it at, hadn't messed with tightening it up any. This is an all iron R1 W2 combo so I don't compensate for growth and just set them at .014 cold.

My cam is supposed to be .734 .747 at the valve with 1.6 rockers. What I measure at the valve is .645 and ,668, I do not believe this number includes lash. I measured lift at the retainer to set spring height and left a little wiggle room in case I wanted to tighten lash in the future. Pretty horrific loss that probably messes with timing a fair bit also.

So you should have ~.458/.466 lobe lift on the cam card?

....so quick math you're losing about 10% or about 1.44:1 effective which I would think would be about right for a 1.5 but not a 1.6

and I would expect the intake would be worse than the exhaust because of the Offset.

I just think you can go tighter (and probably should) on a SBM to keep the slop (I liken it to "jiggle" or a Harmonic in the pushrod as the valves are seating) to a minimum. I kinda wish I didn't sell my 48 degree R3 9.2 deck now, lol

it's amazing SBM's run as hard as they do, imagine if they just fixed the lifter bore angle to begin with back in 64

What do you consider as being "better" results?

Power wise, I will always try and lash loop any engine on the dyno. I've seen HP gains reducing it, and sometimes increasing it. Every engine was different.

A friend in the late 90's used to run up to 0.040-0.042" on his Comp Eliminator small block. Was hard on the valve train, but it was the nature of the beast back then.

That's about what I measured the last time I looked at a 59* smallblock. No denying they generally run good!!!. But they are hard on valvetrain so of-course there is something to be gained in engineering as good a 59* SYSTEM as you can. And that'd start with a gentile cam profile, which is 'inefficient'. So like anything else you'd take into consideration the entire engine like CID and valvesizes and weight etc. The feedback you'd likely get is subjective because of all the variables like rockers used and even optimization of that rocker (B3R). Generally speaking I always error on running the lash on the tight side of recommended. Then you can experiment from there. Best regards.

I just ran it last weekend at Rockingham setting them about .004 tighter at .010 I /.012 E it ran great but the car was off a couple tenths (I hadn't run the car since before Covid) but I think I had some debris in the carb because I had a top end stumble above 6000, I'm pretty sure was fuel system related. Plus I had the M/T tire pressures up around 19 psi so it was spinning just a bit off the line.