Rocker Ratio?

[BenBaron]

hi guys,
Im looking at roller rockers at the moment and am unsure as to what to go for.

Ive got a 72/73 351w block that Im rebuilding that I intend to use with a roller cam conversion and a stoker kit poss to 408.
Im undecided about which heads to go for yet but thats another question later on.....

What I need to know now are your thoughts on rocker ratio and and advice on which ones to go for (not too expensive...)


cheers

Ben

[Clois Harlan]

When I built my SB Ford I contacted the Ford Racing Tech line and I told them what I was doing and what I expected. They suggested going with the 1.7 : 1 ratio roller rockers. I never had a problem and was very pleased with the overall performance of my engine.

Alum Edel heads
Ford E roller cam w/ 1.7:1 Roller rockers (I think I would go to the B cam next time).
Performer Rpm manifold W/ 650 Holley
MSD Ign

Clois

[What'saCobra?]

Had a FORD factory crate 351W, 385hp, alloy heads, MSD billet and module, 750HP Holley, factory cam...nice.

Installed 1.7 ratio roller rockers, replacing 1.6, brightened up engine considerably, still idles OK.

Definitely a no brainer...do it now.

Plugs may need orienting to preferred setting as a safety measure. No problem.

[BenBaron]

hi Guys,

thanx for that, looks like I'll be doing that then...

"Plugs may need orienting to preferred setting as a safety measure. No problem." - what do you mean by that?


cheers
ben

[What'saCobra?]

Yep. Here's the thinking.

If you are using a standard single post racing plug, before installing, mark the orientation of the side post of the plug tip on the white ceramic outside the plug with a fast drying paint, so you can see where the side post is from the installers point of view, even though the plug is now being twisted into the plug hole.

Turn the plug by hand only, alloy heads I hope, until it seats and you cannot hand turn it any further.

Then use your rubber inserted plug socket and your choice of ratchet driver to bed the plug down, until the ID mark on the plug ceramic is at the top. Sometimes you have to move plugs around to find where they will not be either too loose or too tight when the post mark is on the top. Sort of a fiddle.

This makes the side post at the top in the cylinder, slightly further away from the piston for safety. Some engines like this orientation for starting and a wee more power.

Be careful, don't use too hot a plug that reaches down too deep into the piston displacement area. A racing plug will do nicely, with few drawbacks, but not none.

For instance, I currently use NGK R5671A-9 racing non-resistors and they are just great in my 351 crate, standard 385hp engine.

Your kit sounds similar. If you use a non-FORD or other cam, I don't know if the pistons will clear the 1.7 rocker-ratio driven valves.

Drawbacks:
A cold racing plug can be fouled by excess accelerator pump gas if you pump it too much, making starting more difficult. No big deal, just learn to start your engine with the minimum amount of pumper gas you need, particularly when very hot or very cold.

You must use a good CD ignition system and the only one for me is the MSD, which includes your rev limiter of choice. Weak ignitions don't really like cold plugs on the street, where you start up and shut down fairly frequently.

Get used to changing them from time to time. Not a big deal, but also not be ignored forever either. You will know you need them if it is popping backfire through the carb when starting or you get lousy starts and it takes a mile or so to clean them up and you get a good clean pull. (We used to call this an Italian tune-up on the Ferraris years ago, nothing personal meant, just the Ferrari way with the lousy dual Magneti-Marelli ignition system, quirky multiple Webers and cold plugs.)

As usual, be careful, ask for help from your local hot rod/drag racing FORD dudes and get lots of opinions. I cannot gurarantee your engine is the same as mine, so act accordingly; that is, get more input.

Have fun, enjoy yourself and send me a prayer or two if you get a minute.