rocker ratios

Dangerous Doug · #1 (**permalink**) 01-06-2012, 10:09 PM

Considering a freshen up on my 302, and replacing the World Product Windsor JR. heads I currently have with AFR 185's. Thought I'd go with some Scorpion roller rockers, and am considering moving from my 1.6 ratio rockers to the 1.7 rockers to get more lift and duration from my not-quite-lumpy-but-not-quite-mild cam. I don't know the spec's or type of cam.

Anyone using 1.7's on their 302? Does this put too much stress and wear on the camshaft lobes? Do I need beefed up push rods? Do the AFR 185's handle the angle shift on the push rods with the contact point on the rocker shifted toward the pivot point?

Curious if anyone has experience and advice. Thanks, DD

RICK LAKE · #2 (**permalink**) 01-07-2012, 04:49 AM

Dangeous Doug Doug DEPENDING on the camshaft. You can go from a 1.6 to 1.7 ratio. Here's thing you need to check
Coil bind of the valve springs. I know guys running in the .060" clearance. IMO this is way to tight. Specs on most setup like to see .100" clearance. Running .080" is OK but over revving, missed shifts can bend pushrods and do other internal damage.
Rocker arms, spend the money and buy a good setup for your motor. Harland sharp, Jesel, PWR or T&D. Get full roller setups not just tips. Scorpions are made by Dove. Have seen 55 gallon drums of the them at the place last visit.
With running a higher lift rocker need to know if the valve has again enough clearance to not hit Mr. Piston. Again need about .080" clearance min.
Last Valve springs, can they control the added lift and rpm. Depend ing on the camshaft you are only talking about adding .020"-.050" total lift.
The other things are this. If you are looking for more power, start with porting and gasket matching heads to intake. Have the intake manifold flow tested and have all the ports matched for cfm's. Some manifolds are from 10-40 cfm off in range between cylinders. Joe Craine does a wonder ful job on this service.
Next exhaust, If you are running side pipes, the loss of 10-60 HP depend on size of motor. A higher flowing muffler is needed to get the added power you want. Down side is noise.

The last thing, Doug if you are happy with the way this motor runs and has power, leave it alone and built a PURPOSE BUILD motor for your crazyness. This way you have a spare bullet for your car. Shop hard, 302 are a dime a dozen. Best thing is to stroke one to a 347. This will wake up the car. Hope the driver is up on his game plan. Rick L.
Ps 4 info parts missing, max rpms of motor, size of camshaft, HP looking for, age of motor. Compression test and leak down of motor will tell you if it needs a rebuild. You might just need new valve springs. Some thing to think about.

bobcowan · #3 (**permalink**) 01-07-2012, 12:30 PM

That swap is pretty popular. So popular, in fact, that Ford did it for the Cobra motor. It not only gives you more valve lift, but it increase the duration just a smidge - like 2-3* on both ends. I did it to a stock Dodge 5.9l gas engine, it made a noticable increase in power, and improved gas mileage a smidgen.

The question is, will it work with your combo? Without knowing exactly what you have, it's a WAG for anyone. You'll just have to get out the dial indicater and do some research.

blykins · #4 (**permalink**) 01-07-2012, 02:21 PM

I wouldn't have any issue with swapping.

However, I would check:

1. Piston/valve clearance
2. Pushrod/pushrod tube clearance

olddog · #5 (**permalink**) 01-08-2012, 09:03 AM

Quote:

Originally Posted by blykins

I wouldn't have any issue with swapping.

However, I would check:

1. Piston/valve clearance
2. Pushrod/pushrod tube clearance

I will add:

3. Make sure the push-rod length is correct to get the roller tip centered on the valve.

Gaz64 · #6 (**permalink**) 01-08-2012, 01:27 PM

If you don't know who makes the cam, I'd be wary of doing such a change.

The increase rocker ratio x the increase valve spring pressure = more load on the cam lobes.

Personally I would be doing a camshaft change with associated matched components.

vector1 · #7 (**permalink**) 01-08-2012, 06:37 PM

i would look at changing the cam first for the new combination, that might dictate which ratio to use, might be able to use the 1.6 and end up with a better cam. i have asked a well known engine builder about changing the ratio on a crate engine and was advised against it as the gain wasn't worth it.

CHANMADD · #8 (**permalink**) 01-08-2012, 06:47 PM

Its inexpensive enough to try it and see if it makes any diffs...I am sure it will...as said above you might have to change pushrods.. 0.100" longer to get the valve contact rightl.

Dangerous Doug · #9 (**permalink**) 01-08-2012, 10:08 PM

Thanks, guys. Good feedback. I am cautious about the cam in terms of stress and the impact on clearance with the added lift. Hhhhhmmm...

DD

blykins · #10 (**permalink**) 01-09-2012, 02:53 AM

No worries with "added stress." I use 1.7's on almost everything...cast cores, billet cores, you name it. It's a roller, right?

As for the benefit, it depends on how your heads flow. If they max out at .500" lift for example, then increasing the rocker ratio to get .550" lift may not net you anything at all.

Without a dyno, you may not know if you gain anything, but it wouldn't hurt anything to give it a shot.