I have an Lg4 with the stock cam and stock heads. What would be a good set of roller rocker arms to use with my engine in order to get another 10-15 horsepower? Will I need new valve springs?

Here is a set of cheap full roller aluminum arms with stock 1.5 ratio.
http://store.summitracing.com/partde...5&autoview=sku

Here is a set of slightly more expensive full rockers with 1.6 ratio.
http://store.summitracing.com/partde...6&autoview=sku

I think the summit ones are good because of the stock ratio and believe that i won't need new valve springs. Will I get more performance out of the crane 1.6 ratio ones?

 

I would think that you'd get better performance from the 1.6's, but you would have to modify your heads because the pushrods would be at a different angle. This is what I've been told anyway. If you use the 1.5's (stock ratio I believe) you wouldn't free up 10-15 horse just from the reduced friction.

 

You can add 1.6rr with a stock cam and not have to worry about the geometry of it,,, you may need self aligning rockers.. about $250-@350

 

Josh, while roller rockers are great on a modified/race motor they do little or nothing on a stock motor. Especially fof the $$$s spent. Replace the stock cam and lifters with a performance cam and pick up double the power.
More work but way more power increase.
Something like Summit #K1102 cam+ lifter set at $82 really wakes up a stock 305. Now adding a split ratio 1.6 in 1.5ex rocker set will give you
.447 in .442 ex lift with the summit cam. Now you are "cooking with gas".
In order to run a 1.6 rocker on the LG4 heads you must elongate the pushrod guide slot towards the rocker stud as the push rod gets moved closer to the stud with the ratio change. I do this by hand with a 5/16" rat tail file in a drill.
make the slot longer, not wider.
The Summit roller rockers are very good. They are made for Summit by Scorpion. I have a set here. You can buy this rocker in a split ratio set.
Different part number, anodized blue. same rocker.
Do the cam first. add some simple drop on stock diameter hi perf springs for max rpm performance. Comp 981 lunati 73943 isky 205D. set the installed height at 1.70"
if you port the LG4 heads and add headers and better exhaust, your 305 will rock. a moderate compression ratio increase will help too. (shave heads+ thin shim head gasket).
Do all this together and you'll have a whole different opinion of the 305 SBC.

 

I suppose so. I didn't really feel like ripping my motor apart for a cam swap. What is split ratio rockers???

 

A "split ratio" is when you use different ratios on the intake and exhaust valves.

 

ah ha i see. When i do a cam swap (if ever) then i am definetely going with roller rockers and roller lifters. Thanks.