Re: Rocker Ratio 1.7 vs. 1.8
 

Hi Guys,
I ran the add 0.028" of lift through desk-top-dyno and it would seem like the +8 horsepower is not worth the switch.
How much of a gain is there from going for stamped to roller? 5-10HP?

Yes, I have thought of the ZZ502 cam. But Mark at Precision told me that cam is not a vary good cam for an MPI engines with only 8.7:1 compression...
Also, I have the short captain call risers.

Re: Rocker Ratio 1.7 vs. 1.8
 

I would go with rollers either way, there stronger an much more precise

Re: Rocker Ratio 1.7 vs. 1.8
 

You'll never regret buying a good set of roller rockers (ie. Comp Cams stainless magnum version) if only for the piece of mind. I've broken/cracked most other aluminum body roller or stamped steel versions.

I now rev freely with no worries :drink:

Re: Rocker Ratio 1.7 vs. 1.8
 

The correct way to figure is take lobe lift times rocker ratio.

Example:
DUR:
248 IN----254 EX @ .050

287 IN----292 EX Ad.

Lift:
.663 IN---.680 EX

-----------------------------------------------------------------------
Lobe lift :
.390 IN---.400 EX

1.7 ratio .663 IN---.680 EX
1.8 ratio .702 IN---.720 EX
1.9 ratio .741 IN---.760 EX
2.0 ratio .780 IN---.800 EX
-----------------------------------------------------------------------
All cams are advertised with the lift amount for the rocker ratio the motor had stock. A small block chevy will sometimes have a cam with more lobe lift than a big block cam, but be advertised with less lift because of the factory ratio of 1.5.

Advantages to more rocker ratio is quicker valve movements in the same time frame so valve velocity is increased. The motor thinks it has a more agg. camshaft. The obvious reason is more total valve lift.

If you ever change anything in the valve-train you must figure valve geom. (pushrod length) at the very last. Nothing wrong with running more rocker ratio, but must check V to P clearance and pushrod length.

All cams are figured this way, it's just easier for them to give you the total valve lift for the stock rocker ratio when advertising.

Re: Rocker Ratio 1.7 vs. 1.8
 

Good Point!
I had not thought about that one... :cool:

Re: Rocker Ratio 1.7 vs. 1.8
 

Make sure you have enough clearance between the valve and the piston still.........