Technical Zero valve lash for solid lifters?

Thanks for your input guys.

I find it fascinating how much different (and often opposite) opinions (like in "I did this for 35 years, and it always worked perfect") one can get on a question, that should have one simple answer based on physics and engineering 101.

After doing some research and asking a lot of people with much more experience than I have - here and elsewhere - my bottom line is:
It depends. Engine and valve train materials/combination (iron/aluminum) seem to play the main role in the question, if the gap is growing or shrinking on your engine. As you can see in that Power Nation video that Pete posted above, in that particular engine (iron block/aluminum head) it is definitely growing. But there are probably a ton of other variables in play.

After all I was just looking for best practice and maybe a better/smarter way to set lash.

There is still a lot of stuff I'm trying to wrap my head around (like the question of zero lash setting at cold).
I was told it would wipe my cam in no time - thought that lash only exists, when there is no pressure on the lifter in the first place (base circle) - as soon as that gap is taken up you have zero lash during the whole valve event anyway etc.

I mean solid lifters are around forever and I'm pretty sure somebody had the same thought before - so there is probably a good reason for having a lash when cold. I'm just trying to really understand all this in depth, instead of just blindly following the rule book.


Frank

 

Frank , Hydraulic lifters don't wipe lobes because they have zero lash, so it won't do the same with solid lifters.

Hydraulic cams have different lobe shapes to solid cams to get the same duration and lift at the valve
If you fit hydraulic lifters to a solid cam you will increase lift and duration.

As a bit of an experiment, do a compression test on 1 cylinder [cold], then zero lash it and do a compression test again [cold]
The extra duration [caused by the tighter ramps] should bleed off some cylinder pressure , so the compression should go down.

Then run the engine till it gets hot, and do a compression test again [this time there should be some leakage]

 

I’ll do the cold vs hot setting like the video, but won’t be until January. We’re working an extra day a week (night for me) through Xmas. This will be on an L6 (valves in block) Plymouth engine. I’ll recheck the clearance before, but pretty sure set them at .010 and .012 (I/E) cold. The manual calls for .014/.014 cold if I recall (initial to fire it up) and .006/8 and .008/.010 or similar hot settings.
I don’t discount the video, they showed it plain as day. But as you mentioned, I’m thinking it’s the Aluminum heads as a factor.
I’m****uming if temperature is the same, Aluminum must expand more than cast iron and maybe steel (pushrods/lifters/valves) expand more than cast iron? But I’ve never had valve in head engine with solid lifters.

 

The coefficient of expansion of aluminium is about double that of cast iron so there isn't a direct comparison of iron /iron head and block and aluminium / iron, other than they're all expanding.

Chris

Chris

 

So that means per degree in rise of temperature, aluminum will expand more than cast iron.
Ok professor. How about steel v cast iron?
Heck, I’m gonna Google it anyways

 

Seems to be a few folks lashing out here. Sort of a gap in opinion. I like when topics like this lift our moods. So far we have a duration of 2 pages, and we gotta be getting curious as to what degree will this advance or retard our overall view on clearance. It seems knowledge runs hot and cold sometimes doesn't it? Like opening a valve, then we hope it doesn't stay open too long cuz it might cause burnout. Best to take a seat now and then to cool off if all this intake becomes exhausting. I mean, none of us wanna be off our rocker. We just push our rods to the limit once in a while. I hope nobody taps out, feels like they got the shaft, or pulls on their lobes while seeking an overlap in shared knowledge.

Signed;
Bumpsticks Anonymous

 

I have, aluminum head on cast iron block, camshaft in head, no bearing inserts, directly acting upon solid lifters.
The lash when cold was significant, 15 thou'. Up to temperature it was about 7 thou' which is a considerable change given how few moving points were in the system (much the same as a flat head engine, just inverted).

The expansion rates of that engine were evidently addressed because it used bolts with a higher than expected elastic value to secure the head.

 

On a L6 cold I set them +.003” on the hot setting called for and forget them. It’s a PITA to open the side cover (s) to check them unless it was on a test stand.
Everything I have said I do it for all iron parts. Aluminum heads are different different on an OHV or OHC engine.

 

Hard to trust someone with 97 pens in his pocket!

 

I gain about .003. Big block Ford, aluminum heads, roller rockers. Cold lash is set at .015.
My Boss 429 only gives a cold lash setting (.013). No idea what a hot setting would be as it takes 45 minutes to remove all hardware to access the rockers.

 

Why not adjust them hot if the engine designers put that in their manuals? Avoid the controversy and do what they say to do.....

 

One would think that this would have been the only thought when considering how to handle this.

There seems to be an undercurrent of thought that automotive engineers 50-90 years ago were just banging rocks together, and had no idea whatsoever of what they were doing.

People even tell me that I don't know what I am doing, and I was designing automobile parts for a major manufacturer, just prior to writing this post.

 

You are too kind......there are many on this forum who firmly believe engineers are******s. Wait for the responses......

 

I didn't even realize there was a problem setting lash on solid lifters? I've always just set them to spec, and put the valve cover back on. Somehow it has worked without any problem for my engines.

 

It is not just here.

I recently had a field technician demand that I tell him who I thought I was insisting that I knew what the specs were for a newly introduced part.

Mind you, he worked for the same company as me. I told him to go look at the internal documentation, but to not read it, just to scroll to the bottom and read back the name of the author to me.

He's still working toward ending his performance improvement plan.

Hubris leads to nemesis.

 

Well, 'cause it's easier said than done, literally. Mopar flatheads have a hot spec, hot and some even insist on running. If you're not familiar, the valve/lifter covers are below and behind the exhaust manifold. And on my 56 they omitted the access panel in the splash shield so you either have to be a contortionist or completely remove that shield which is a real pain. It also helps to be a masochist as there will be pain from the manifold. Double difficulty if you're running dual exhaust as the second added outlet and pipe really mucks up the access.

Me, I just add a little .002-.003, to the cold clearance, set them on the engine stand and install it. If it ticks, maybe redo them after some run time, but cold!

The question of expansion is really difficult for me to grasp. Everything grows when at operating temp, including the block. So how much do the think the spaces from crank center to cam center and cam center to head mounting surface change? Seems to me those would be the biggest contributors to lash change, esp on flatheads.

 

That’s a good portion (test stand) of why it’s going to take me some time to do it. I’ve got the engine on a frame with casters, but need to build the rest of it. The last L6 I made a WAG and set the valves .004/.005 looser cold, but never ran the engine. My buddy who wound up with it didn’t remember if he redid the valves or not (was over 15 years ago). Actually I picked this engine up from @HSF , he crawled under his car, hot and running and adjusted the valves. 50? Mopar I think.

 

Pretty much...I prefer to use the specs provide by someone that has been grinding cams for 60+ years., rather than the know-it-alls floating around in cyberspace...
My cam ground to the information I provided about the engine: iron block/alum heads, roller rockers Etc.

 

@MikeLawless pointed out O.T. VWs gain clearance in valve gap with temp increase. This is inversely proportional to the 'norm' in our cast iron engines.
To fortify Mike's observation, I too raced the little bugs (years, including drags) and with our Formula V. (open wheel formula racer with strict 40 H.P. stock engine)
As competition was very tight, any advantage was taken advantage of: Get to the track, start and warm engine.
When at operating temp, shut off and remove valve covers. Make hot setting at factory cold specs, .004".
Advantage was valves opening at closer specs, making the 'mild' cam act 'wilder'.
After our heats and main event, covers were removed and valves loosened up for weekly storage.

 

Anyone who's spent notable time with engineers know that the field has its share and then some. Like not knowing why they can't put an intake manifold bolt thru a spinning cam. Have to have a sample nut to get bolts for things. I've built a lot of drag race cars. We were putting cages in abuse test vehicles. "Hey! You stop right now and listen to me! I want this bar to go..." and in a hissy fit manner addressed me like it was my 1st ever, and he knew better. When his rant was done I handed him a sketch I shared with my crew, "You mean like this right? Me and the boys got this, no worries." Then he was mad when a tig welded custom bent 10pt cage wasn't installed and ready to deliver 2 hrs later with only me and 2 others. Yeah, some engineers ARE******s. Gives the good guys skid marks. I have a few horror stories.

 

Maybe this should be broken down into four schools of thought
# Automotive design engineers, who do it for a living
# General engineers who understand the basic principals of mechanics and thermodynamics
# Non engineers who are just overthinkers
# Folks who use Google a lot.

 

Google is a savior in so many cases. I can learn about something in 30 minutes, that was put together by those who spent many years in school and work in the field.
Someday this internet thing is going to catch on.

 

Short story (I hope) about when engineering is 1st and foremost. I was doing a hot rod 2 stroke, and the advice of the time was to gut the existing airbox, to remove the "shelf" that held what appeared to be a cpl inverted nuke towers. "They inhibit airflow and have to be removed" is how it read. I tried it, but as luck would have it my latest monthly mag was in the mail that night and had an article about speaker engineering, and how it related to airbox design in these engines. I was leaving to test my new mod the next night and grabbed my removed shelf to take along.

I cracked the throttle and was rewarded with the sound of a wounded bull moose, and a hot rod 2 stroke that wouldn't pull a sick****** off a piss pot. Where it previously topped out at around 105 I had a hard time getting over 80.
Seems those cones actually use the reverse pumping noise to compress the existing air in the box to not only cancel noise but to give an above atmosphere pressure condition too. There are indeed some smart engineers out there. Speaker cones, airboxes, supercharged with noise. Who'd a thunk it.

 

After spending about a decade as a mechanic I saw the perspective from the mechanic's side of things. It often seems that engineers in equipment design often forget about the poor sap that has to service a machine when something breaks. Something that should be a simple job can end up taking multiple times longer to do, and require exponentially more blood, sweat and tears that could all be eliminated with a simple re-engineering. I've also seen engineers from the OEM come into a shop with a lot of hubris to help with something that has everyone stumped, and be reduced to a mumbling nincompoop by the end of the day, as they too failed just like the mechanics they felt so superior to when they arrived.

We used to say that at one time some engineer came home from work early and caught his wife in bed with a mechanic, and from that day forward every engineer's mission was to make life a living hell for all mechanics....

 

In the world of two-strokes (where I get hopelessly lost!) wasn't there also a modification that was known as "stuffing" the airbox or crankcase?

 

I don't know about that, but it was common to pinch the fuel return line to boost fuel pressure in the injectors for a nice boost in power...

 

Thank You!! I'm so out of touch!!! Pens equals trust!!! Good to know!!! Pete

 

I just set solids at whatever the spec sheet says lash should be.

 

That's called tunnel porting when you mod the crankcase. In production the inside of the case is just machined as needed. If you carefully increase volume and smooth out the transition areas you effectively fill the cylinder more.

Some are rotary valve (Rotax) and some are reed valves. Its simplicity personified in some ways but the dynamics are hard for us when we're so used to 4 cycles and cams and lifters and such, none of which applies. Not to stray too far, but the theory has massive power merits when applied right, and I'll submit that a good understanding of both 2 and 4 cycles is worthy research in the quest for power and efficiency.