Max Gross Valve lift, Stock Heads

[Jerryl]

I am not understanding the hyper interference issue.
I have run hypers +0.030", with a 212/212 FT, around 0.445 lift, 980 comp springs, stock HG's, decked block/heads, for a few years without any issues.

It is not just about lift, but about XX lift at a given piston location.
Only one easy way to find out;
Time the cam with a degree wheel, check for clearances, and re-check again.
Than walk away and recheck again a few days later.

 

[84BuickGNYorkPA]

I used play-doh to check clearance on my build last yr. What ever you do before you torque the heads down check them for piston to valve clearance with something.

Chuck

 

[WkillGS]

I wonder how long of a duration on the exhaust side would allow the piston to actually hit the valve? The intake valve should never be open to hit the piston at TDC right?

It is not just about lift, but about XX lift at a given piston location.

Yes, thats it!
Valve-piston clearance is at the minimum between 15 degrees BTDC and 15 degrees ATDC while the intake valve is closing, AND the exhaust valve is opening....generally referred to as the cams valve overlap. Either valve could be a problem.
Cams with tighter lobe separation (107 to 110 degrees) or lots of duration are the ones that will give the most problems with v/p clearance.
CAM INSTALLATION is also very important.... if the cam is installed too far advanced or retarded, one of the valves may have clearance issues.

Only way to know for sure is to measure v/p clearance, either with the clay method, or with a dial indicator, degree wheel, and a solid lifter.
If only one valve has clearance problems, you can usually advance/retard the cam a few degrees to optimize v/p clearance between the intake and exhaust valves.

 

[turbobob924]

I did not have to do anything on mine.

I found my old cam card. I do have a 212 cam not the 216 like I thought!

Total lift on the 212 cam is .456

A 218 cam has .469 total lift.

.489 seems pretty high to me?

I would be more interested in making sure the lobs clear the cam bearings when installing.

There will be no issues with the pistons since there is a pretty good dome in them there hypers.

 

[jdpolzin]

I thought .489 was pretty high as well but thats what it is on the cam I want to use. I now have four cams to choose from but this one seems more appealing to me!

 

[turbobob924]

Damn that must be a custom grind cam or something?

I hope the heads have plenty of work to take advantage of it

 

[jdpolzin]

Damn that must be a custom grind cam or something?

I hope the heads have plenty of work to take advantage of it

It is a custom ground cam. Problem is right now I dont have my heads worked yet. I'm bolting on stockers with Kirban springs until I get my port work done to my spare set of heads.

 

[87GN_70GS]

Depending on what intalled hiegth the springs were installed at and their solid ht measurement, you may have coil bind issues. I would have the machine shop check that out as well.

 

[jdpolzin]

Depending on what intalled hiegth the springs were installed at and their solid ht measurement, you may have coil bind issues. I would have the machine shop check that out as well.

Thats a good point. At what lift do you start to have problems with coil bind? I'm going to run a set of Kirban 100# springs with this cam. The cam card doesnt give me a spring recomendation.