t&d 1.65 roller rockers pro's and con's

[Hotfoot]

hi guys,pro's and con's on 1.65 t&d roller rockers on ported iron heads? besides clearance on pedestals.
thanks mike

 

[ek02]

They open the valves faster, give you more lift, and are adjustable. All pros and no cons as long as you have enough piston to valve, retainer to guide/seal clearance, and the correct length push rods.

 

[bison]

The cons would be you'd need more spring pressure and less room to achieve it if you were on the edge. So less rpm with identical spring pressure. Some lobes can't be used with 1.65 rockers on iron heads. There's isn't enough spring selection with <1.75" installed that hit the required pressures on aggressive stuff without coil binding. I've made some work with PAC 1203 but used 1.55 ratio just to be able to shun the springs tighter for more pressure.


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[ek02]

Bison is correct on the spring issue. I machined my spring seats larger and deeper for a larger diameter spring and retainer that I sourced from Reed Cams many years ago to get the correct pressure on my iron headed engine.

 

[Hotfoot]

thanks, it's going to have a small atr 206/212 cam until I decide if I want to do a 4.1 someday.

 

[pacecarta]

if its the ATR 212/206 RP309g billet roller . that cam can be used on unworked heads with 1.65 rockers . still have to do the pedastil clearance for rockers and proper springs and check for coil bind and valve guide interference and youl need taller valve covers or spacers to clear the rockers

if its a flat tappet it may have .325 lift at the lobe and result will be .536" at valve and that will need work to the valve guides (cut down ) and a proper spring and retainer package

 

[turbo89]

thanks, it's going to have a small atr 206/212 cam until I decide if I want to do a 4.1 someday.

put the largest rocker ratio you can 1.65 with that cam