1.7's or 1.6's

[Cwalk]

Most of the people here have 1.6:1 roller rockers. Why not 1.7:1's or 1.72:1's? I see people often using Cobra heads but not using the same size rocker as a Cobra? In the Cobra it proved the combination does make a few more horses and increase the air flow into the intake. So if you are using a more free flowing intake? Why not a bigger rocker?

 

[MAC'n89Blckstng]

1.7's may be too much lift for many applications. I have an E303 cam with 1.7's and I'm actually losing power from having them. I have too much lift for my heads. 1.6's are the stock ratio. People usually get them for the valvetrain durability.

 

[bubba-dough]

Its all aboout the cam being used. Also piston to valve clearance.

 

[BlownFiveLiter]

Figure the lift at the valve on a Cobra is .479 I/E with the factory 1.7 roller rockers, but only around .450 if you were to use a 1.6 rocker. Now figure you were to take say... an E cam and run it with 1.7 rockers like MAC'nBlckstng is doing. The E cam is rated at .498 lift I/E with 1.6 rockers, but when you use 1.7s, your lift increases to .529. Some heads may benefit from the increased lift, but you may run into PTV clearance issues or hurt flow velocity with that much lift. You need to take all aspects of a cam into account, including lift, duration, and lobe separation if you want to have the best cam suited to your particular application.

 

[25thmustang]

I have 1.7s, but also have a stock cam. Another thing you can play with is shimming them, and to get the ultimate combination some people stagger them intake to exhaust. You run whats best on your combo!

 

[Strype]

1.7's require the pistons to be notched unless used on a stock cam...

 

[Cwalk]

I have 1.7s, but also have a stock cam. Another thing you can play with is shimming them, and to get the ultimate combination some people stagger them intake to exhaust. You run whats best on your combo!

The heads Im getting are 210's from D&D motorsports. I have a Trick Flow stage II cam. The heads are supposedly good for .652 of lift. The cam says it has .542/.563 with 1.6 rockers. So I think I should be able to make good power with my 347. Im shooting for 450hp NA.