Technical Valve lash

I have been doing it wrong with cold lash clearances! Hot lash settings when done cold should be tighter to start then they losin up when hot? example hot lash setting at 12 thous should be 4 thous more(16 thous) at room temps? I thought the cold lash should be loser then when metal get hot it expands and the lash would get tighter! My head hurts!! Pete

 

Pete, you example sounds correct to me. I have found this to be the case. Set valve gaps a couple of thousands wider than what is called for in hot setting spec. When engine warms up parts valves will expand and close gaps. Setting them cold is good for first start up, but finish setting them when warm if that is what is called for in the specs.

 

Always, set them cold, not wrong..!

Just about EVERY race engine in the world...gets the lash set...cold ! Go ahead, I dare you. Go to ANY race, anywhere in the world. Road race, Indy car race, drag race, boat race, motorcycle race, piston driven aircraft race, off-road race...anything with poppet valves, the valves set...cold (or mostly cold)...period.

Hot is a pain. To do it CORRECTLY... warm to running temperature, set one, "maybe" two cylinders. Rewarm the engine, set one "maybe" two cylinders, And so on.

Within a couple of minutes, hot engine parts start to cool. Which cool the fastest ? Cooling changes everythings dimensions ! You have cast iron or aluminum (really bad hot !), stainless steel, bronze, titanium, various high grade steels, solid parts, tubing parts, thick sections, thin sections, etc....ALL cool at their "own" rates.

Cold is cold...no dimensions to change while setting the valves.

In my 70+ years, no one's been able to convince me hot is better, but I AM willing to change, IF someone can come up with a better routine than the rest of the internal combustion world, (and not take 8 hours to complete the task !).

Mike

 

Do um cold. warm it up good, check one and see how much it closed up. Then you know what to set them at next time.

 

Started setting cold in about 1968 , setting warm is just .....silly ! IMO
The directives say " lash when hot" doesn't say anything about " adjusting when hot" ...

 

All Honda car engines from the 2000's at least it is factory recommendation to clearance the valves COLD only.

 

So setting them cold,If the hot lash number is .016" then the cold setting should be .012" ? cast iron block and heads ,004" tighter. cast iron block and alum heads, .006" tighter. alum block and alum heads .008"-.012" tighter, According to the video? Pete

 

I've always set 'em cold, one hole at a time (using a remote starter switch to bump). Little on the loose side, worked for me since.... way back. The guy that showed me had some Wallys, so good enough for me!

 

I've checked both on my slant six Dart. Last time, I adjusted them with the engine hot and running and then checked them cold the next day. Factory specs (hot) are .010 intake, .020 exhaust. I think I set them a thousandth looser than specs with the engine running; the next day, the average was .013 cold intake and .025 cold exhaust. Therefore, the lash was .002 greater on the intake and .004 greater on the exhaust with a cold engine.

 

Aren't they saying the opposite on the video? tighter when cold then the lash gets looser when hot? Am I having a senior moment? I always sent the lash cold a few thousands looser, They are saying the opposite. I'm confused!! Pete

 

can someone please explain this !!?!!

seems to go against everything I was ever taught about setting valve lash .

and wanting a tight setting ?!
Again always told you should be on the loose side of the setting .

I only know of a couple engines that give you hot settings , majority are all set cold .

 

OK! So here is my question, The cam card for my flathead KiWi cam(L100) states .016" for both intake and exhaust. Does not state hot or cold. According to the video those numbers on cam cards are hot setting, so should I set at .012" then when it gets to operating temps it should rear .016" ? Its a flathead and more work to check hot settings. My point is I set the lash at .016" cold and to me are noisey ! Pete

 

I'm like a lot of you guys. I always thought that the lash tightened up when warm. I never verified it for myself. When we started sprint car racing, I bought a 1 year old, refreshed 410 C.I., 875 HP, solid roller cam, all aluminum engine from a well known WOO racing team, built by Gaerte Racing Engines. We were told to set the lash to .000" cold. I questioned this. Gaerte told me about the lash growing with heat. Yeah! I had been doing it wrong for 40+ years!

 

Yes, set them tighter when cold, clearances will open up when hot. I believe most cam companies list solid cam clearances based on hot.

 

Lash settings can be played with to increase or decrease lift and duration. I have seen tuners play with this. Recommended lash numbers are just that. They can be played with, within a few thousandths.

 

Just my experience with my one solid lifter engine...I double-checked so I could set them cold in the future. Nobody ever called me an expert though...

 

I had a friend years ago use to set his solids in a sbc running. He had some chewed up feeler guages to prove it. Sooooo, my solids in my 261 should be .006 and .018. Now I should set them cold at .002 and .014? Not gonna do it. Lippy

 

Hey Lippy! Did you set your 261 at .006 and .o18 hot? If so then cold they should be .oo2 and .014 if this video is correct. I have a flathead and it would be difficult to get a accurate hot setting. Pete

 

When I was looking for specs for my 218 Lhead, I came across a cold setting for intake and exhaust both at .016, hot was (depending on use) .008-.012 intake and .010-.012? For exhaust. I posted a snip from where I found the info and @Hillbilly Werewolf posted very similar from his manual as well.

 

Pete I set them 6 and 18 cold. It's a new engine and after it's broke in I'll check them hot and see where they are at. Lippy

 

Setting valve lash hot on a flat head v8 seems impossible. I did receive a flat head reground cam with the tag stating to set clearances at .006" hot!. Just doesn't add up. Greg

 

If you look in the proper books/servoce bulletin you can find cold lash settings for most mechanical cam shafts. I like to start with a cold lash setting if I know it then warm it and reset hot.

 

I understand this is NOT a motorcycle site but if you bare with me for a second....
I have a '76 Harley and the valve clearance will get larger when the engine is hot. I stumbled onto this when I was trying to get this thing to start cold. It was just so hard to start, took a lot of cranking to fire but after it started it ran fine, and warm starts were easy. One day I checked the valve adjustment and it was very tight to the point of holding the valves open a little. These valves are hard to adjust as the pushrods are ball shaped on the ends so you cannot use feeler gauges, you tighten to no free play and back off 1/4 turn, 1/2 turn or something... On mine you just adjust until there is 0 end play (when cold) after the engine warms up you will get a little end play.
This engine has steel cylinders and alumimum heads, so I guess the cylinders and heads expand with heat more than the pushrods, rockers and valves do. Also the fact that this is air cooled the cylinders may run hotter than a water cooled car motor. But this went against the way I have always thought it also, learn something new every day. My guess is that the guy that sold it to me was trying to get the motor a quiet as he could, thinking back, the motor was warm when I first looked at it.
One more thing, this has a solid cam set up.

 

I just had to replace the push tube seals on my rather OT beach mobile, and that meant valve adjustment. VW says to let it cool overnight and go .006. As I read on that is due to the stock engines having aluminum push rods which expand at different rates than would steel. Mine has after market heads, twin springs, roller shafts and thus chrome molly rods used so my clearance had to be less but adjusted cold as well. I had to make a logical guess and put .003 on them. I will see when I warm it up today if that worked or if get to re-adjust.

I know the reference was OT but the use of different metals is not as most hot rods have performance parts installed (thus the use of the word "hot" it does not pertain to flatheads boiling over). Using factory manual specs will not achieve optimum performance IMO when the engine had been modified.

 

I just went through this exercise today as I'm breaking in a cam, so I had to do this anyways.
500 cube BBF, aluminum heads, Harland Sharp rockers, cold lash is a tight .014. I let the engine warmup to 190 degrees pulled a rocker cover off and the lash is a snug .017. The cam company wanted .016, so it's close enough for now.
Good thing is after 40 minutes of break-in run time it didn't gain any lash. Now comes the fun part of installing the heavier springs.

 

One thing to keep in mind is the OP has a FH, no pushrods, regardless of heads used, won’t affect lash.

 

So is this guy's primary qualifications his goatee and patch on his shirt? And that he said so on YouTube?
Cool. Got it. Yup.

 

I like doing it this way

 

I think I read all the posts so far, but didn’t see anyone mention cast iron vs. aluminum heads and/or block?? And the Engine Power video always had me a bit cross eyed too - seems backwards.

John

 

I do my slant 6's valves with the engine hot & running.