Rockers and Rollers

[jonclancy]

I decided to have a quick squint at my donor engine (the one out of my Project X Midget) and got all excited to see solid rockers under the cover. All the other rockers I have on my XI engine or spares bits are the pressed steel items.

"Ooooh, forged!", I thought. "Maybe got an EN40 crank in there - it is a '68 after all...".

But, it is a rebuilt engine (I knew that, and obvious by the engine number), so the chances of that are slim.

Seems I have sintered rockers from the A+ Series (and very late A Series). Maybe Mini items. Slightly less than 1:1.25 lift, apparently.

What do you gent run? Rollers, forged, pressed, 1.3/1.5. Just wondering out of idle interest.

All five pics here:

http://s94.photobucket.com/user/jonclan ... t=3&page=1

Cheers

Jon

[Westfield 129]

Swiftune roller rockers, 1.5:1 ratio, bushed rather than rollerized fulcrums. This saves a couple of hundred USD. The RHD's engine has Mini Spares rockers, which use the spacers, washers, springs and the adjusters from the original rocker setup. Saves a few quid, but I prefer the Swiftune parts, as they are a complete rocker, shaft and tower assembly, ready to install out of the box.

My experience with the pressed steel rockers is that they break, even when not being used with a high lift cam.

There are 1.5:1 forged rockers, and you can also install new bushings into the forged rockers to get a 1.5:1 rocker ratio to match any of the better performance cams.

My preference is for the roller rockers, as they promote longer valve guide and seal life (less side load on the valve stems). Roller bearings or bushings is OK, depending on the size of the magazine in your money gun. I also use Iskendarian cam followers and Iskendarian pushrods. If you are running a milled head with around 21cc chambers, you may need to shim the rocker shaft pedestals to get the right geometry.

[jonclancy]

My money gun is a single shot, small-calibre, black-powder musket.

[erictharg]

Echo what Jan says. Valve train is the most highly stressed part of an engine. Roller rockers help a lot, reducing friction, mass and side load on the valves. I also agree that you shouldn't waste your cash on those that have rollers on the shaft bore - only needed on the tip. I use MED's. They seem well made and competitively priced. Anecdotally both the pressed and sintered rockers are OK for modest performance upgrades, but roller rockers are one of the first thing I'd spend money on. The 1.5 ratio also helps get a bit more lift from an otherwise modest cam. If you do run 1.5's remember to open up the valve clearances by an extra c.15% to maintain the same clearance at the cam.

[jonclancy]

Thanks chaps - all useful info, stored away.