Normal factory cam. .030in .030ex

 

Yes, Oger's right!

But some say they like to run the good old 30-30 cam at, (I think), .026" on both sides.

pdq67

 

Yes, Oger's right!

But some say they like to run the good old 30-30 cam at, (I think), .026" on both sides.

pdq67

Thank you oger, and pdq67 , What will running it at .026'' do ,,, Increase valve lift ??? ,, and if so is this more a race combo or street combo, I am have trouble trying to get it to run nice as a daily driver ???
thanks again

 

Standard 3.73 gears or optional 4.10s and a close ratio, M-21 tranny and as good a gas as you can put in her and that is about as good as it gets with the little motor!

Just drive it like you stole it!!

But first make sure your valve springs are good b/c I'd hate to see you float a valve at 7 to 7500 rpm!!

pdq67

 

What is the correct tappet clearences on a 302 and are there multiple options

Set them cold at .026"/.026" (only if you have stock stamped rockers), and use the EOIC method to be sure the one you're adjusting is on the cam's base circle; the "30-30" is the only cam Chevy ever made that has both intake and exhaust valves still on the clearance ramps at TDC, so you can't set them at TDC.

The factory stamped rockers aren't 1.5:1 - they're 1.37:1 at initial contact, and 1.44:1 at full lift.

There's a full report on this issue I authored on the CRG site under the "CRG Research Reports" button that explains it in detail.
:beers:

 

Specifications for the 302 Z-28 cam are .452" intake and .455" exhaust lift, 229 degrees intake duration and 237 degrees exhaust duration (both measured at .050" tappet lift) and 78 degrees of overlap (at 0.000" lift). Since this was a flat tappet mechanical lifter cam valve lash was set at 0.030"/0.030"; which gave this cam's popular name of the Duntov 30/30.

Large Dave (Big Dave to my friends)
Retired Industrial Engineer

 

Specifications for the 302 Z-28 cam are .452" intake and .455" exhaust lift, 229 degrees intake duration and 237 degrees exhaust duration (both measured at .050" tappet lift) and 78 degrees of overlap (at 0.000" lift). Since this was a flat tappet mechanical lifter cam valve lash was set at 0.030"/0.030"; which gave this cam's popular name of the Duntov 30/30.

Large Dave (Big Dave to my friends)
Retired Industrial Engineer

Hello Larger Dave. The specs are closer to 254 @.050" and .485" lift (with true 1.5 rockers) for both intake and exhaust.:beers:

 

A 30-30 solid cam is like per GM, 346/254, 114/112, .456"/.456" lashed at .030".

pdq67.

And it may be .455"/.455"!!!

 

I went back to my library and researched again instead of relying upon the web. According to Chevrolet Power volume 1 number 1 published in 1973 the specs for the 3849348 mechanical "Duntov" cam are as follows:

Intake opening point 44° BTDC closing point 89° ABDC camshaft duration at lash point 313° camshaft duration at 0.010 tappet lift 283° camshaft duration at 0.050 tappet lift 236° maximum lift at 1.5:1 rocker ratio 0.447" point of maximum lift 110° ATDC overlap at 0 and 0.010" lift 88°/0 39°/0.010";

Exhaust opening point 93° BBDC closing point 40° ATDC camshaft duration at lash point 313° camshaft duration at 0.010 tappet lift 283° camshaft duration at 0.050 tappet lift 236° maximum lift at 1.5:1 rocker ratio 0.447" point of maximum lift 120° BTDC overlap at 0 and 0.010" lift 88°/0 39°/0.010".

This camshaft was also used in the 1964 and 1965 special high performance and fuel injected 327's installed in the Corvette as well as being installed in 1967 through 1969 (and 70 1/2) Z-28 302.

Larger Dave

 

Hello Larger Dave. The specs are closer to 254 @.050" and .485" lift (with true 1.5 rockers) for both intake and exhaust.:beers:

The above numbers are quoted from my Crane Blueprint 30-30 cam card. Additionally, EO is 63* BBDC, EC is 11* ATDC, IO is 15* BTDC and EC is 59* ABDC.


Hey pdq67, a while back there was a post that had a link to Pat Kelley's website or some other place that listed the duration at different lifts. Do you have that link?

 

No, don't have it but I think Pat K. always said the old 30-30 was more like a 304 cam vs 314 per W/B/R and 346 per GM.

And I have two early Chevy Power Books and they both have SOME bad cam info in them!!

JohnZ, just what are the 30-30 cam's spec's?

pdq67

 

Somewhere along the line I picked a link to PK blog maybe that lists the measured values of a 30-30 cam. Can't seem to find it now.

Googled it and found it! http://cochise.uia.net/pkelley2/solidcams.html

Here is the whole site. http://cochise.uia.net/pkelley2/index.html

 

JohnZ, just what are the 30-30 cam's spec's?

pdq67

Chevrolet never published actual duration at .050", but if you pick the points off the factory cam drawing (which we've verified with laboriously-developed cam lift/crank-angle measurements), it's 254*/254* at .050" tappet lift, and max tappet lift is .3233", including .020" of ramp. Gross lift is a function of rocker arm design, and the factory stamped rockers are NOT 1.5:1; they max out at 1.44:1 at full lift.

:beers:

 

Thanks John,

There you go, 254/254 duration at .050" lift and almost right-on, .485" gross lift with a true 1.5 ratio rocker.

John, another question please?

Why did GM make the 30-30 cam instead of just revise the old -097 Duntov b/c imho, the little old Duntov is one sweet solid cam........

You know, make a Duntov II cam spec'ed like 238/242, .452"/.458" gross lift and still use the .012" and .018" tight-lash numbers. And hold the centers the same too.....

pdq67

 

Thanks John,

There you go, 254/254 duration at .050" lift and almost right-on, .485" gross lift with a true 1.5 ratio rocker.

John, another question please?

Why did GM make the 30-30 cam instead of just revise the old -097 Duntov b/c imho, the little old Duntov is one sweet solid cam........

You know, make a Duntov II cam spec'ed like 238/242, .452"/.458" gross lift and still use the .012" and .018" tight-lash numbers. And hold the centers the same too.....

pdq67

Additionally does anyone have the seat timing that corresponds to 346/346? The DCR program wants those numbers.

 

I use 314 from W/B/R's old cat.

pdq67