Valve Lash / Cam Questions

-
Jim910

Jim910

Well-Known Member
Joined
Apr 18, 2020
Messages
67
Reaction score
47
Location
Tarrytown, NY
Hello, I am going to adjust the valve lash on my 1967 Barracuda 'S', 273ci, that I just got. The previous owner installed an Insky cam when he rebuilt the engine. The Cam Card shows .020 gap for both the intake and exhaust valves. I just want to make sure that I'm reading this right being that on a stock cam the intake and exhaust lash are different. Also, could anyone please tell me what I can expect performance wise from a 273 bored 30 over with Egge pistons and this cam and a Edelbrock carb. Many thanks for any help.
Insky Cam Card.jpeg
 
I like to run a tad more on the exhaust. That cam is mild, I would maybe run .018/.020" HOT lash and see how it does. It probably could tolerate .022/.024" really well if you wanted it a touch smoother (idling), but I doubt you'll need that. Whatever you do, use those figures HOT. About the only cams I know of that set cold are MoPar Performance (.028/.032"), which ends up tighter (iron heads) when hot.
 
Type 273 valve lash or 273 valve adjustment in the search box. Lots of threads about it. Exactly the same combination I have in my 66
 
Try it .020 like it says ..then add .002 at a time or take away .002 and see if it's more or less of what you want. Spec is usually best ime.
Side note..
I like the Z-35 cam and the .555 for street strip isky grinds.
 
follow the valve adjustment sticker. Its for a stocker but the cam timing is not that far off from any other LA camshaft.
312P4452989.jpg

Youll be able to tell when the cam/rocker is at its base by looking at its motion when you turn the cam.
 
Bighead440 said:
I like to run a tad more on the exhaust. That cam is mild, I would maybe run .018/.020" HOT lash and see how it does. It probably could tolerate .022/.024" really well if you wanted it a touch smoother (idling), but I doubt you'll need that. Whatever you do, use those figures HOT. About the only cams I know of that set cold are MoPar Performance (.028/.032"), which ends up tighter (iron heads) when hot.
Click to expand...
I found it interesting that Isky recommends .020/.020 but it's enough of a gap not to burn valves. I use stock specs, get a little rattle when cold that goes away when warmed up.
 
toolmanmike said:
I found it interesting that Isky recommends .020/.020 but it's enough of a gap not to burn valves. I use stock specs, get a little rattle when cold that goes away when warmed up.
Click to expand...

Yes, they mean HOT, so it'll be looser cold. The MoPar specs of .028/.032" are cold specs, and way back I found out that setting them hot was a good bit tighter (iron heads). I used to set my 360 with J-heads and iron (Erson?) rockers at .024/.028" hot and then even tightened it to .022/.026" hot before eventually switching to 1.6 Crane rollers and defaulting to .024/.028". The old slant six 225 in the smogger days was .010/.020" hot I think, but the performance cars (Max Wedge/ Street Hemi) were cold settings if I remember correctly.
 
I use .016/.022 cold. It rattles a little when cold and quiets down when up to temp.
 
Bighead440 said:
I like to run a tad more on the exhaust. That cam is mild, I would maybe run .018/.020" HOT lash and see how it does. It probably could tolerate .022/.024" really well if you wanted it a touch smoother (idling), but I doubt you'll need that. Whatever you do, use those figures HOT. About the only cams I know of that set cold are MoPar Performance (.028/.032"), which ends up tighter (iron heads) when hot.
Click to expand...

Not so my fine feathered friend !
A lot of people , including me set tighter clearances /cold , I just reset mine cold yesterday , .006 titer when cold on alum. heads , has worked well for , for about 9ish yrs !!
 
pishta said:
follow the valve adjustment sticker. Its for a stocker but the cam timing is not that far off from any other LA camshaft.
View attachment 1715542170
Youll be able to tell when the cam/rocker is at its base by looking at its motion when you turn the cam.
Click to expand...

Or , u have a see th ru valley plate , like mine !
not only for stock cams .
Remember when that mopar sticker had 4 valve lash setting per rotation , it was for hi lift cams , now they recomend the 2 lash one for all cams --------
 
famous bob said:
Not so my fine feathered friend !
A lot of people , including me set tighter clearances /cold , I just reset mine cold yesterday , .006 titer when cold on alum. heads , has worked well for , for about 9ish yrs !!
Click to expand...

Did I not say IRON heads? On tight lash cams with aluminum heads you almost have to set them at ZERO lash dead cold so they can open up. Iron works the other way, in my experience.
 
Shall I adjust my rockers .002 looser or tighter when cold is a interesting discussion. Most all solid cam rockers are noisy/loose when started cold but the noise goes away as the engine warms up. Now, some of that could be lubrication but not after 10 min. or so of warm up. Things should be lubed up by then. Heat does cause metal parts to expand but does it cause the gap to tighten or actually get larger because of the expansion. I say tighter but I haven't checked them cold and then warmed the engine up and checked the gap again.
 
toolmanmike said:
Shall I adjust my rockers .002 looser or tighter when cold is a interesting discussion. Most all solid cam rockers are noisy/loose when started cold but the noise goes away as the engine warms up. Now, some of that could be lubrication but not after 10 min. or so of warm up. Things should be lubed up by then. Heat does cause metal parts to expand but does it cause the gap to tighten or actually get larger because of the expansion. I say tighter but I haven't checked them cold and then warmed the engine up and checked the gap again.
Click to expand...


You need to check your cold lash, fire it up, get the engine to operating temp and measure it hot.

You’ll find they get loose with heat. Not as much as an aluminum head will but .002-.004 is typical.
 
toolmanmike said:
Not too messy?
Click to expand...
Not at a slow idle and some cut down valve covers installed. Been doing it that way for over 40 years. I think it's a better method than with the engine off. You can hear each lash clearance change when you run the feeler gauge in and out. On older engines with some wear on the components, sometimes you can't get it accurate without the parts moving. You can also check for wear better by pushing the rockers a bit sideways while it's running, to see if it has a badly worn spot in the face that hits the valve. The lash sound will change if it starts to run a spot not worn. That will alert you that it would be a good idea to pull the rocker arm assemblies and check them all for wear. I've done it hot with the engine off too, and if you use a dial indicator instead of your standard feeler gauges, that works pretty good too. I just think doing it while running is better because it's in the condition that you will be running and driving the car. Either way, always check to see that the push rods are straight by spinning them. While the engine is running, you should be seeing them rotate. Always a good sign. You can also see that oil is getting to everywhere it's supposed to. There again, on engines with some miles on them, I've found many rocker arms with plugged oil passages. That can hard if not impossible to determine if the engine isn't running.
 
Thanks everyone for the advice. I going to go with spec to start (.020 hot on each) and go from there if I need to.
 
In regards to solid flat tappet cams..with lock/jam nut style.. I do it while cranking the starter, best way, period.
A friend showed me that. The most accurate imo. You put very very light pressure on the allen...then hold it firm while locking the jam nut. He was sharp. Till you're heads up at the track, it's just preference.
 
Last edited:
MOPAROFFICIAL said:
With lock/jam nut style.. I do it while cranking the starter, best way, period.
A friend showed me that. The most accurate imo. You put very very light pressure on the allen...then hold it firm while locking the jam nut. He was sharp. Till you're heads up at the track, it's just preference.
Click to expand...


Can you make a video of that because I’d love to see it.
 
You must log in or register to reply here.
-

Back
Top