My dilemma 1.7's or 1.6's

[Rev]

I recently bought a new CC Exe 268 H (268/280 H - 224/230 @.050) to replace my old 268 H (218/218 H @.050) cam. As recommended, I am checking the valve/piston clearance. I'm doing it with both the dial indicater and the modeling clay method ( my machine shop doesn't like modeling clay).

To make a long story short, it looks like I will have plenty of clearance with my existing 1.7 rockers giving about .540 I / .544 E lift with the new cam. With the 1.6 rockers I'll have .5.09 / 5.12 lift.

I already have the TF 1.7 rockers from my old set up. I have 1.6 TF rockers on back order from Summit. I guess my question is, do I really want the .540 /.544 lift even though I can get it without clearance problems.

It would save me $240 returning the 1.6 TF rockers to Summit. I've heard that around .500 is a good top limit for valve lift limit on street driven flat tappet cams.

I can have either the 1.7 rocker .540 / .544 or the 1.6 rocker .509 / .512 lift as I choose. Do I really want extra wear with the 1.7's as apposed to the 1.6 .509 / .512?

That's my dlleimma. Any advice appreciated.

Rev

[Capri306]

What heads are you running there, guy?

BTW, 1.7's require more force (from the lifter and pushrod perspective) to open the valves, thus creating more valvetrain drag. I'd rather save the friction and put the torque the engine is producing to something more useful, but if that much more valve lift is going to give you more power (again, head and driving characteristic dependencies), mebbe you should go for it.

[~The Jester~]

Unless you're looking for "all-out everything you can get out of it" performance, I'd go with the 1.6's. IMHO in your situation the valvetrain strain/friction just isn't worth that extra little bit of lift you're gonna get. Valvetrain geometry is SOOO critical, and it's the biggest horsepower stealer in your engine. The extra .1" of lift (at the rocker tip) is probably going to steal more horsepower than it'll make for you. You'll have more reliability, and less chance of turning a pushrod into a pretzel. That, and you'll save yourself some beans by returning that stuff to summit.

Just my $.02!

[tmoss]

I was advised by Ed Curtis to use 1.7 rockers over 1.6 rockers due to the good ramp rates on the early 5.0 SD cams - similar to the quick ramps on the XE cams. You'll get better cylinder fill with a quicker opening valve. MY car is a street car first and Ed understood that when he gave me the advice. Won't be a HUGE difference, but may be 5-10HP. And, my heads were prepped and set up with springs for the 1.7 rockers also.

[Rev]

Actually, it'll cost me $240 to use the 1.6's that I just received from Summit. I had the 1.7's for my old 268 H (218/218 @ .050). They gave .485 lift with that old cam. I am thinking that I should use the 1.6's anyway and just try to sell the 1.7 TrickFlow RR's. Even with my TFTW pocket ported heads, I'm thinking that the .509/.512 lift will be enough for my purposes and might save some valve train wear and tear in the future. Thanks for the responses.

Rev

[Dark_5.0]

I dont think the 1.7's would help at all with the heads you are running. So save the $240.00 for gas.

[Chevyguy]

I would be concerned about the max lift of the valvesprings as well. Did you check the P/V clearence with checking springs??

[Rev]

Originally Posted by Chevyguy

I would be concerned about the max lift of the valvesprings as well. Did you check the P/V clearence with checking springs??

Yup, I used checking springs with the dial indicater and also with modeling clay to check piston / valve clearance. I have plenty even with the 1.7's (.175/.250). I did have weak valve spring pressure at the seat (about 80 lbs). That induced me to order new CC springs, retainers, and locks for another $160. The new springs are supposed to be good for .600 lift without coil bind so that shouldn't be an issue. I think I'm gonna go with the 1.6's even though it'll cost me an extra $240.

Rev