[promptcritical]

My Bullet SFT cam card gives lash adjustments at 024 and 020, hot I figure. Can I set them hot, then let the car cool all the way (like over night), check them cold, and then adjust to the cold numbers with the motor cold from then on?

Also, I have HS 1.65 rocker arms. Do I need to compensate for the difference between the 1.5 and 1.65 ratios?

Another question ( sorry for the scope creep). When checking for vacuum leaks, what is best, or good, to use to spray around and what exactly am I looking for with whatever I use. Increase in rpm, decrease in rpm? I saw a guy using a propane torch once.

Thanks,
John

[STEELCITYFIREBIRD]

My Bullet SFT cam card gives lash adjustments at 024 and 020, hot I figure. Can I set them hot, then let the car cool all the way (like over night), check them cold, and then adjust to the cold numbers with the motor cold from then on?
>Yes, a common practice.

Also, I have HS 1.65 rocker arms. Do I need to compensate for the difference between the 1.5 and 1.65 ratios?
>NO

Another question ( sorry for the scope creep). When checking for vacuum leaks, what is best, or good, to use to spray around and what exactly am I looking for with whatever I use. Increase in rpm, decrease in rpm? I saw a guy using a propane torch once.
>BEST-A smoke test machine works best and is safest.
>GOOD_Propane works well,but is flammable, as is carb cleaner, anyway.
About a 2' x 1/4" id hose and a one handed operable (normally off for safety reasons) on/off push button valve setup works well to locate and pinpoint leaks.Try to keep cylinder with discharge at top/upright.
Idle will usually smooth out and increase with the added propane fuel @ the leak.Propane is heavier than air so it will "puddle", keep that in mind,cooling fan usually clears it away unless you are putting down way to much

On FI vehicles it helps to disconnect the tp sensor so the engine will be running in open loop,and not compensating/adjusting idle for the vacuum leak when using propane.

I have a very old Rotunda/OTC? unit that looks similar to this.

HTH, LUKE

[gtofreek]

If using iron heads, they won't change a whole lot. With aluminum heads, the lash will increase by about .007" on a Pontiac when hot. So, with aluminum heads, I set them .007" less when cold, then check them hot to see where they are.

BTW, there is no such thing as a stupid question if you learn something from it.

Originally Posted by promptcritical

My Bullet SFT cam card gives lash adjustments at 024 and 020, hot I figure. Can I set them hot, then let the car cool all the way (like over night), check them cold, and then adjust to the cold numbers with the motor cold from then on?

Also, I have HS 1.65 rocker arms. Do I need to compensate for the difference between the 1.5 and 1.65 ratios?

Another question ( sorry for the scope creep). When checking for vacuum leaks, what is best, or good, to use to spray around and what exactly am I looking for with whatever I use. Increase in rpm, decrease in rpm? I saw a guy using a propane torch once.

Thanks,
John

[blykins]

Just check 'em hot. If you're quick, you can roll through all 16 before the engine cools.

As for rocker ratios, if you really wanted to get anal about it, you multiply the lash ramp number by the rocker ratio, so anally (is that a word?), your 1.65's would get a hair more lash.

Un-anally, don't worry about it.

[gtofreek]

Originally Posted by blykins

Just check 'em hot. If you're quick, you can roll through all 16 before the engine cools.

As for rocker ratios, if you really wanted to get anal about it, you multiply the lash ramp number by the rocker ratio, so anally (is that a word?), your 1.65's would get a hair more lash.

Un-anally, don't worry about it.

Yeah, because most people don't know the lash ramp number.

[promptcritical]

Thanks guys. Paul, I learn from reading this forum all the time. Ported iron heads by the way. Brent, I'm pretty un-anal, but I'm slow so it takes me while to get the valve covers off an plugs out and then run the valves. Luke, is carb cleaner an ok way to go then if I'm careful?

[STEELCITYFIREBIRD]

Yes, not real precise for pinpointing smaller leaks, but it will get the job done.
What do you think your likely chasing?
A gasket, vacuum hose/accessory or casting porosity leak? If you think the porting may have got too deep. Remove PCV valve (if equipped) and plug it and put a few blasts of carb cleaner into the crankcase.
------------Engine Guru's
Cam card lash # is the minimum, hot correct?
And you can run more, but not less than specked?
I was taught to set valves correctly hot, and then to establish a cold baseline based on that setting for checking/adjusting. Eliminating the possible temperature variation. An speeding up weekly maintenance (circle track background). Is that outdated or improper?

I guess I'll search how the lash ramp number and rocker ratio effects static valve lash.
Anally....I'm not searching that, unless you want to explain one...or both!

[STEELCITYFIREBIRD]

"BTW, there is no such thing as a stupid question if you learn something from it."

Great attitude, I totally agree!

[blykins]

Cam card hot lash is not minimum. I've ran tighter than spec many times. The lash can be adjusted to "fine tune" the cam and if you lash it tighter and the engine picks up top end, you can have a good feeling that the engine would like more camshaft duration.

I really don't like to go over the spec, as that actually *decreases* the effective duration of the cam, plus it's easier for the lifters/cam/valves to take a beating.

Once you get a few under your belt, you can actually set the valves cold and get within a thou or so hot. As Paul stated, all iron combos don't change much at all, lash grows about .006" with an aluminum headed motor, and lash grows about .014-.015 with an all-aluminum engine. Based on that, you can get real close cold, fire the engine, get it hot, check them, adjust if necessary, and you should be good.

Remember, the easiest (and most accurate IMO) to run the valves is to use the EVO method. Set the intake valve when the exhaust valve on that pair is starting to open. Set the exhaust valve when the intake valve on that pair is starting to close.

Once you have that nailed down, you can zip through one bank fairly quickly and if your brain is young and sharp (not mine), you can be eyeballing other valves that are needing adjustment and hop around.

As for the lash ramp, that's built into the camshaft by the grinder. Each cam lobe design has its own lash ramp and since most cam lobe designs are universal, the cam grinder will multiply the lash ramp by the rocker ratio to get a good valve lash figure, and stick it on the cam card.

[Cliff R]

"With aluminum heads, the lash will increase by about .007" on a Pontiac when hot. So, with aluminum heads, I set them .007" less when cold, then check them hot to see where they are."

Correct, they will "grow" more with aluminum heads. I don't see quite that much with my engine, but they do open up some at least .003-004" from dead cold to fully warmed up.

I run a "tight lash" set up with a solid roller lifter on a HR cam. Started out setting them at .008", they grew to around .012", so now set them at .005" and have ran them that way for quite few years now. The valve train is very quiet, the only V-8 engine I've ever had in a car that doesn't have a "ticker" someplace for one reason or another.

I've built a number of solid lifter engines over the years, and "tight lashed" them right on the dyno. With some cams you see a nice increase in power doing this, at the same time idle quality and engine vacuum is degraded a bit. With other cams we don't see much, so it's pretty much on a case by case basis.

Quite a few years ago we tested a Comp flat solid cam in my own engine, and power jumped dramatically going from around .022-.024" lash down to .012-.014". Built another 455 and had it on the dyno with a custom flat solid Comp cam from Butler, and power hardly budged no matter where we lashed the valves at. So basically it's one of those things you just have to jump in and get dirty to find out what's going to work the best?.......Cliff

[Steve C.]

If interested. This calculator will determine what the new lash should be for the new rocker arm ratio.


http://www.wallaceracing.com/calc-lash.php


.

[promptcritical]

Thanks.
-John

[blykins]

Don't really need a fancy calculator....

Whatever your cam card says for lash and rocker ratio, just divide the lash by the rocker ratio. That's your lash ramp spec. Then just multiply it by the new rocker ratio. Badda boom badda bing.

[promptcritical]

TA DA!!

[Lee]

Agree with Brent's post (#9). I've found some nice performance improvements by tuning the valve lash. START with what the cam card suggests, then tighten the intake a thousandth or two, and retest. Find what works best on the intake, then start testing the exhaust.

My last car picked up 25rwhp in the midrange and 15 on the top end by doing this.

[promptcritical]

Originally Posted by Cliff R

"With aluminum heads, the lash will increase by about .007" on a Pontiac when hot. So, with aluminum heads, I set them .007" less when cold, then check them hot to see where they are."

Correct, they will "grow" more with aluminum heads. I don't see quite that much with my engine, but they do open up some at least .003-004" from dead cold to fully warmed up.

I run a "tight lash" set up with a solid roller lifter on a HR cam. Started out setting them at .008", they grew to around .012", so now set them at .005" and have ran them that way for quite few years now. The valve train is very quiet, the only V-8 engine I've ever had in a car that doesn't have a "ticker" someplace for one reason or another.

I've built a number of solid lifter engines over the years, and "tight lashed" them right on the dyno. With some cams you see a nice increase in power doing this, at the same time idle quality and engine vacuum is degraded a bit. With other cams we don't see much, so it's pretty much on a case by case basis.

Quite a few years ago we tested a Comp flat solid cam in my own engine, and power jumped dramatically going from around .022-.024" lash down to .012-.014". Built another 455 and had it on the dyno with a custom flat solid Comp cam from Butler, and power hardly budged no matter where we lashed the valves at. So basically it's one of those things you just have to jump in and get dirty to find out what's going to work the best?.......Cliff

So Cliff...if the cam card calls for 0.020, what would you a reasonable "tight lash" clearance would to experiment with? I know going tighter is okay. Maybe a stupid question but I want to learn

[Cliff R]

There really isn't a minimum clearance, but the take up portion of the ramp is designed by the cam manufacturer for the lash they supply on the cam card. So probably best not to deviate a lot from their numbers. You aren't chasing down a lot of power depending on how they have ground that part of the lobe, at least from what we've seen here.

I've moved a few on the dyno and saw NOTHING. You can tell when something is going to happen when you tighten one up and vacuum at idle is 2-3" less than before you did it. This shows that it added some duration and overlap to the deal.

You'll see more from this deal going to higher ratio rocker arms instead of tight lashing a solid cam that's already where it's supposed to be........Cliff

[promptcritical]

Thanks

[GRX]

1.65 rockers .... feel compelled to ask if head to push rod clearance was checked.

[Skip Fix]

I'll usally set a cylinder or two hot and then recheck when cold to tell exactly what the diffrence is.

I always wonder since by the time you get to the last cylinder the motor is cooler if that could cause a change so I like to set them cold-get burnt on hot motors less too