bbc rocker ratio question 1.7 vs 1.8
 

when 1.7 AND 1.8 rockers are run on bbc does the 1.7 go on the exhaust valve or the int? i have crane gold roller rockers how much play should there be on the pin to roller tip that rides on the valve? thx for info. ratman

Re: bbc rocker ratio question 1.7 vs 1.8
 

Just depends on what you are trying to acheive, which one are you trying to improve. Might want to make sure the extra lift doesn't bottom out your springs, or cause the valve to hit a piston.

Re: bbc rocker ratio question 1.7 vs 1.8
 

or put the bottom of the retainer/locks into the top of the stem seal.

THere's no rule of thumb.
Whichever side is your weak side gets the additional lift. Optimally, your cam will be staggered to fit your application, but the rockers give you tweak-ability.

Re: bbc rocker ratio question 1.7 vs 1.8
 

the motors are 577ci n/a's with big brodie heads, flat top je pistons. there were crane 139741 cams in the motors i stepped it up to a 139661 crane hyd roller.741 was 234/242 @ .050 vs 256/264 @ .050 741 is 610 int/632 ex vs 661 632/632 lift. where would you run the 1.8's? and why? thanks, ratman

Re: bbc rocker ratio question 1.7 vs 1.8
 

springs are good for up to .650 lift, and i have plenty of piston to valve clearance.

Re: bbc rocker ratio question 1.7 vs 1.8
 

#1) The 1.8's will put your lift up to .670" which means a different spring setup.
#2) "plenty" of piston to valve will STILL need to be rechecked during assy.

which heads? as-cast 305cc? or cnc 325's?
What exhaust you running? Dry or wet? Mufflers?

My gut is to stick with 1.7's on both. No new spring issues, pushrod length issues... If you just HAVE to run the 1.8's, then I sorta think you should put them on the intake side. If you run mufflers or wet headers, then maybe put them on the exhaust side.

that's my thoughts.

Re: bbc rocker ratio question 1.7 vs 1.8
 

I agree with mcollins and would not run them in this application. You have plenty of cam for the motor and will not likely see any gain from the 1.8's not to mention other issues mentioned above.

Re: bbc rocker ratio question 1.7 vs 1.8
 

the motors came with the 1.7 and 1.8's in them and crane 139741 cams.

Re: bbc rocker ratio question 1.7 vs 1.8
 

im running lightnin dry headers.

Re: bbc rocker ratio question 1.7 vs 1.8
 

A 741 is a split pattern cam that favors the exhaust to make up for deficiencies in the GM heads. Your Brodix heads are running a heavily improved exhaust port, so your new cam choice while still a split duration cam, has equal lift on both sides. This is a good thing for your heads.

I bought a motor once that came with an edelbrock SP2P intake on it, a 1.5" open phenolic carb spacer, and a 780 Holley with stiff springs in the secondary vacuum pot. Just cause it came that way doesn't mean that it was a good setup (I may still have that crap in storage somewhere if you want to try it)...

Re: bbc rocker ratio question 1.7 vs 1.8
 

mcollinstn, i just put both sets of the crane roller rockers on ebay. i gonna buy 2 new sets of scorpions in the morning. i actually put the heads on one motor and yanked them back off. i bought these motors used from tommy at chief and freshed them up they came out nice so at the last minute i decided to stick some stanless int and inconel ex valves in it. the engines were built by engine experts and i was suprised that they DIDN"T already have stainless valve in them. i mean who builds 700hp 577 ci motors for marine app with non stainless valves? thanks for your advice, ratman

Re: bbc rocker ratio question 1.7 vs 1.8
 

If you have the money to spend, you might want to look at shaft rockers.

Re: bbc rocker ratio question 1.7 vs 1.8
 

i went all oout on the blower motors mark at mer is building he did too olds, these 577 n/a are back up power so hyd instead of solid on this one. i shouldn't have anytrouble with 139661 cams, new springs from tommy at chief he uses these in all his hyd roller motors, new morel lifters, good moly push rods, and now new 1.7 scorpion roller rockers. it should hold together ok. don't plan on turning it much over 6k