does anyone know what is the max lift I can run on stock 14101081 heads with the stock springs?

thanks

 

With stock springs? Keep it under .500 lift to be safe.

You can measure the spring compression, keeping a minimum of .060" between the coils, to find out how much lift the springs will allow. You also need to make sure the bottom of the spring retainer doesn't hit the top of the valve guide/seal. The rockers need to be checked to make sure they have enough travel without hitting the rocker stud (not a problem with roller rockers). Lastly, piston to valve clearance needs to be checked which is difficult without a camshaft.

Too many factors to give a real yes or no answer or a specific lift number.

 

the cam Im looking at will be .500 (313) with 1.6 rockers...do you think that would be ok?

thanks

 

I wouldnt do it unless you either have the rocker arm studs pinned or you mill down the boss and install screw in rocker studs. I've seen stock pressed in studs pull out with only .468 lift

 

It's not the lift directly that pulls the studs out but the spring pressure. By increasing the lift, you're also increasing the spring open pressure.

 

will a local machine shop know how much to mill down the bosses for .5 lift as i dont have a problem replacing the studs...they are cheap and im sure the labor wont be that much.

thanks again
Buzzman1

 

When you start modifying factory heads for performance, it can be a lot cheaper to just buy aftermarket heads with all the modifications already done.

 

If you have not ported the heads pretty extensively, 500 lift on un ported 081 heads is a total waste. It's not going to make more power

 

You can go .460" lift on stock heads safely. .470" is pushing it and anything higher than .480" is a no-go.

However, any time you replace the stock cam with something bigger you should replace the stock 20-year-old springs and the valve stem seals too. With Manley part number 22410-16 springs and 23652-16 retainers you can get stock heads to accept a .525" camshaft but no higher. You run into retainer to seal clearance above that point.

 

i know this is an old thread but why start a new one - it will show up on new posts.
if you add a .050 shim and .050+ offset retainer - will this increase all the figures by that amount - so that a safe lift with a zz4 cam at .474/.510 acceptable - with proper springs and pinned heads?
and does anyone know the difference between a 10 degree and a 7 degree offset retainer? and what is the stock valve stem size for the 081 heads - i cant find that. and when they talk about lash caps are those just the caps on the top of the springs?
whoever said building engines did not require math - lots of math. i feel like i should of been an engineering major instead of studying law.

 

yes, offset locks and shims will gain you clearance.
10* has more holding power. more angle to grab. 7* is stock. Not worth the upgrade IMHO until you have LOADS of spring pressure.
use the offset locks and shims, set it all up, and MEASURE IT. dial indicator, feeler gauges, dial indicator, and you're set.
valve stem = 11/32", like every other small block chevrolet.

 

thank you very much. i will have to do that or pay to get the darn things shaved and screw in studs and i am a cheap sob and just want to pin the studs and raise the springs enough to handle a mild street cam.

 

JUST AS A NOTE i AM RUNNING ABOUT .470 LIFT FOR MONTHES W/NO ISSUES