Pro's and Con's, Rocker Arm Ratios

[GT63]

For all of you engine builders. What are the pros and cons between using 1.5, 1.6, and 1.7 rocker arm ratios on a small block chevy?

 

[HAceT]

Good question.....I can't wait to see the responses..I heard that going from 1.5 to 1.6 that you'll get mors lift at the valve. I also heard that using 1.6 for Intake and 1.5 for exhaust it will great more power. I just never tried it. I always went with 1.5's all across or 1.6 all across just make sure the valve clearance is still good for the piston and the valve stem to lock is good.

 

[joes23t]

The changing of the ratios will chinge the Spec's of your cam. All cams are speced to a specific ratio. Some people would change there rocker to get some extra lift but I personaly would use what the cam was designed for just my opinion. Joe

 

[Brucer]

I particularly don't like to use the 1.6 rocker arms in a small block chevy. I just get the cam I want to begin with..

I have used them in the past,if your running a cam,and thinking you might want a lil bigger cam you can just swap the 1.5 rocker arms with the 1.6 rockers and it will get you a little more lift and duration.

I've heard staggering rockers will give you either bottom end or top end, depending on if you put them on intake or exhaust .. When I've used them I used all 1.6 or all 1.5 though. I haven't ever staggered them.

I read an article from some GM engineer that said there wasn't enough performance gain from the 1.6 rockers to offset the incorrect geometry, wish I could remember where I read it..

 

[speedkills502]

The 1.6 and 1.5 staggering is used a lot. Most of the time the 1.6 is on the exhaust most sbc heads have good intake flow but the exhaust is lower it will help the exhaust flow with the more lift I do think the duration will stay the same but I could be wrong. I have done this on cars I bought and felt improvement but just as was stated if you are building the motor, are changing the cam order the cam you want and run the 1.5 ratio. There is some things that need to be checked changing ratios make sure the push rod doesn't hit the head where it passes though the head. Check the rocker to see if it is riding on the center of the tip of the valve if not change the push rod length to center it and check your piston to valve clearance. If you do this you will have no problems with the 1.6 ratio I would not run 1.7 on a sbc I have seen them on dirt track motors it puts a lot of side load on the guide even with correct push rod length. If you want to see the difference just take your actual cam lift and multiple it buy 1.6 to get total lift.

 

[Screaming Metal]

yep, its best to get the correct cam for the job, but sometimes its not enough......sometimes we'll use 1.6's or 1.65's on the exhaust, as a tuning tool.....if we are hampered by header selection......ther's a lot of different ways to tune on a engine........
Thats like if you get a die grinder and cut a trench on your piston right below the sparkplug, and groove it out so that you make a trench that goes toward the the exhause valve....you can totally alter the characteristics of your engine....its almost like changing your cam.

I hope I didn't step on any engine builders toes out there.......I'll probably get bitched out about this............but its a old trick........:lol:

 

[HAceT]

[quote name='Screamin' Metal']yep, its best to get the correct cam for the job, but sometimes its not enough......sometimes we'll use 1.6's or 1.65's on the exhaust, as a tuning tool.....if we are hampered by header selection......ther's a lot of different ways to tune on a engine........
Thats like if you get a die grinder and cut a trench on your piston right below the sparkplug, and groove it out so that you make a trench that goes toward the the exhause valve....you can totally alter the characteristics of your engine....its almost like changing your cam.

I hope I didn't step on any engine builders toes out there.......I'll probably get bitched out about this............but its a old trick........[/quote]


Hey old tricks work right.....that is how hot rodding all started anyway....I like old school.

 

[GT63]

I found this article while doing my research.

Rocker Arms 101 - Everything You Need To Know - Vette Magazine

I'm currently running a SBC 355 cu in with Edelbrock Performer RPM heads and 6-71 Blower. The short block has dished forged blower pistons in it. The cam is Comp Cams blower cam AH268H that was recommended to me. I think the 1.6 rockers will wake it up a bit more. I might try it and see. I can always put the 1.5 rockers back in.

 

[blownt]

I have never seen a 1.7 on a smallblock. 1.7 and 1.75 are mainly for big blocks. I have half 1.5 and half 1.6 on mine I got from Comp Cams. Would doubt seriously if you would ever notice the diff on the street. All those tricks are for the strip but figure "what the heck".