PLANT PROTECTION

iTrader: (6)

My new combo will be running shortly, AFR 180cc comps, Superram, LPE219. A cookie cutter combo with one small difference, 1.7r rockers. This changes lift from .560 to .598, also increasing average lift and ramp rate, all seemingly good things. What I am worried about is the rockers changing the 'magic' between the SR and 219 by changing the valve timing that the engine actually sees, .050 at the valve will have more duration with 1.7s. Here is how I see it:

Pros:
-Increased max lift, .560 to .598, especially good with the comp port
-Increased avg lift, gotta peak higher on the same seat-to-seat duration(for the most part)
-Increased ramp, basicly the same reason as avg lift

Cons:
-Altered valve timing from 'ideal'?
-Lower rocker mechanical advantage of the 1.7s, pushrod cup moved closer to the fulcrum leeching more HP to open the valves

Will the positive effects of 1.7r rockers outweigh the negative effects? Also, I'm no engine expert, so I may be off base on my pros and cons, I could be over thinking this. Thanks for any input.

3.8TransAM

One thing I would be very wary of would be valve spring clearance and pushrod clearance. 1.5 to 1.6 is usually okay on anything performance orinetated to begin with.

Going to 1.7 might push spring clearance and or pushrod clearance.

Also check to see that the rockers are actually maintaining a even(middle) path on the actual valve stem.

I've never been real found of puching a lot of lift on the street, I try and keep it in the .500 to .550 range and less, just for reasons of durability and reliability. U can get around this, but I serioulsy recommend running all premium hardware(im assuming u have it, seem to be a well thought out setup)

"Ideal" cam spec is more influenced by the head design and intake. So maybe a litte more being that you have the SR might help you out there.

Best bet would be to actually get it running and tuned and then try it out on a dyno and quanitfy the differences. Not alll engines like 1.6 or 1.7 rockers. Might like it on intake only or just exhaust.

When do I get to see it?

later
Jeremy

KiLLJ0Y

iTrader: (1)

will that even work with stock valve covers?? i wouldnt think so..

LT1guy

iTrader: (1)

When I bought my 97 SS, it had the LPE 219 cam in it with 1.65 Crower rockers, all under stock centerbolt style steel covers, for .577 lift. Durability was fine, it just didn't work well in a T56 equipped LT1...I changed it for a GTP 6 with 1.6 Comp rockers (.568/.592, 236/242), which was much better with my combo. Never tried it with the LPE cam, but with the larger cam I ran stock centerbolt magnesium Vette covers, with the oil drippers broken out.

HiTech5

iTrader: (4)

Valve springs!

You WILL NEED titanium retainers and an aggressive spring. Something with seat pressure around 140 and open pressure in the 350 -360 range at max lift.