Roller Rockers, 1.5 or 1.6

[Ray Hamilton]

I have a 2.8 with the 3.1 kit in it and a Holley 502 TBI with the manifold bored out, and a cam 204-214@.050 .420-.443 lift.
I was considering a set of roller rockers from Comp Cams. What gains if any will I get with these rockers? Obviously the 1.5 are stock. Will the 1.6 work with this cam? I don't have stock springs.
This set-up is in a S10 with 3.73's and 700R.

Thanks

[geoffinbc]

You will notice a difference. I did on my engine.

If I were you I would spend my first bit of extra money on headers though. They will get you more power than the rockers.

[Ray Hamilton]

Is there a set of headers out there that actually fit? I had an old jeep with a chev 229 with headers and they burnt out in a couple of years. Alot of underhood heat also.
Would you go with the 1.6 or 1.5s given the lift I have? I have the Fiero valve covers, thanks to you, so there should be no clearance problems.

[Wiz85]

Well it all depends on a lot of things on whether or not to use 1.6 rockers. Are the heads ported, what's the flow rating, which is more superior in flow; intake or exhaust port? Questions like these helps determine what setup to chose. I prefer the 1.6/1.5 setup with the 1.6 on the intake side. Though, since the iron heads flow pretty crappy as in like ~170 cfm at .450" lift on the intake side and less than 70 cfm on the exhaust side. Someone correct me if I'm wrongThere wouldn't be tons of benefit unless the heads flowed really well. Yes you will gain power, but not the most for the swap. Here's some general guides:

-1.6 rockers all the way around increases power throughout the entire powerband. Benefits from heads that flow really well both on intake and exhaust.
-1.6 rockers on intake/1.5 on the exhaust increases power in the mid-range and more overall torque. Benefits from good flowing intake ports.
-1.5 rockers on intake/1.6 on the exhaust increases power more at the top end and adds a few hundred rpms to the powerband. Benefits from good flowing exhaust.

[Ray Hamilton]

Stock heads. I would rather have mid-range, when it shifts into OD. The guides have already been ground down due to interference with the retainers and the lift. I know I won't have piston to valve clearance problems but what about spring bind?

[Ray Hamilton]

I have read that the comp cams(and other) rockers will bind upon adjustment. The socket binds inside the rocker. Ever heard of this? Is there a fix?

[geoffinbc]

I have never herd that. I have herd that the pushrod guide plate may need to be clearanced or the pushrod can bind.

[torq455]

i have them too. i wanna say i had a gain of ~12 HP. hehe--i did the front 3, then took the car out and noticed the gain. there's plenty of room for more lift. with my stock 3.1 it was one of the biggest gains, second to my 62mm TB, that i have done. no porting or gasket matching, just a stock exhaust without the converter. my goal was to gain more power without losing my mileage, and i achieved that goal! you will love them! you will need to change the rocker studs, but i'm sure CompCams can get you the right ones. otherwise, no mods are needed. the exhaust needs as much help as possible. say max flow is at .450. lift to .490+ won't hurt anything. that just means exhaust will be at max flow longer than with a lower lift, therefore giving you more total volume for that cycle. just make sure your springs can handle the extra lift.

[Ray Hamilton]

I'm excited now.

[powerdoctor]

Hey guys...

Im suprised only one of you meantioned coil bind and stress.

Your "lift" at the valve is a combination of lobe lift x rocker ratio.

you have stated that your cam is .420 (heh heh) and .443 lift at the valve.

if you take that valve lift and and run thruogh the math you will find that a .443 valve lift = a .295 lobe lift.

so a .295 lobe lift x 1.6 rocker ratio = .472 valve lift.

The stock springs on that head will have problems @ .490 lift., even though you say yours are different.

We are talking about a .063 margin here for stock springs, 63 thou does not make me feel warm and fuzzy about that at all.

Get some different valve springs....if yours cannot handle this.

watch your open rating of the springs (psi) or you will tear up your retainers and lifters, ect...

[powerdoctor]

I have heard the stock iron heads, with only the casting flash removed will flow a .650 lift.

it was in this book I believe...

[powerdoctor]

Does anyone know of any other 60 v6 books?????

[torq455]

i'm pretty sure even the 3500 heads with casting smoothed won't flow at .650! i mean they will still flow air, but that lift is well past a mild casting blend aif flow max let alone the old iron style.

[geoffinbc]

I think he means the flow wont stall until .650 lift. But even that seems like a lot to me.

[powerdoctor]

Yes...

But still, if you have a .490 lift at the valve... and you do put in a .650 lift, we are looking at a difference of only .16 valve lift

Thats only a litttle over 1.5 tenths of an inch or 4 mm, which to me is still a small amount of added lift.

Duration is what the issue to me would be... messing with vacuum and port velocity, not the "big" lift.

You could go small duration and big lift, and accomplish for the most part what a smaller lift big duration cam will do, so long as the cam grind/ timing is set for it...