1.5 ratio rockers or 1.6?

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75greenduster

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I'm getting ready to order a set of crane gold rockers and can't decide whether to get 1.5's or 1.6's. I decided after the bottom end of the motor was already together that I wished I would have gotten a little bit bigger cam. The motors going in a Duster that will be a weekend cruiser with very little strip time. I plan on running 91 octane.

360 bored 30 over
9.5:1 comp
align honed to the ARP main studs
crank ground 20/10
eagle sir rods
windage tray, dbl roller timing chain
Comp XE274H 274/286 at .05 with 1.5-.488/.491 with 1.6-.521/.524
heads are 587's with 2.02 intakes installed, bb, gasket match
Eddy RPM AG
msd distributer and 6AL
carb probably holley or eddy 750
headers 1 5/8 or 1 3/4 havent decided and probably 2 1/2 in ex with flows and an x pipe
4 speed
probably 3.91 gears

Suggestions are greatly appreciated.
 
your right - it could have used the next cam size up - but better too small than to big for street use.
If you go with the 1.6s (and I would) you will have to grind/bore the pushrod holes (especially the intakes) to get enough clearance for the pushrods as the pushrod is now closer to the rocker shaft and the angles change from the lifter to the rocker pivot.
650dp speed demon carb will give you great throttle response for the street.
Don't know where you are located, but if you do much driving when the temp is 60*f or less I would consider the RPM Performer. The airgap is a good intake - but waiting to get some heat to the carb so it will idle is a bit of a pain at times. :drinkers:
 
Well if your heads and springs are up to it, the 1.6's will give you the more lift and duration you're looking for. Watch the coil bind and make sure your heads can handle it though.
 
mostly lift change right?

the duration will stay the same..
 
Thanks for the responses guys. Changing the ratio will not change the actual duration but will change the effective duration...this much I am certain of. The valve lifts faster so airflow gets underway quicker.

383dart. You talk about grinding for clearance. Just to make sure I understand, the 1.6 rockers work by shortening the pushrod side of the rocker arm? If thats true it would make sense that the holes would have to be clearanced. I'm kind of confused though why intakes would need it more than the exhaust.
 
Anyone else have an opinion? Would that give me too much cam for my motor and give it extremely poor street manners? I'm still looking for more feedback.
 
I would not get the crane rollers. Get the Crane ductile iron. They are bullet proof. They will last forever. Get 1.6 on the intake and 1.5 on the exh. That is what Jim at Racer Brown recomended for me. 378 inch 340 with a Mighty 650.. Call Don at FBO. He can hook you up.
 
70Barracuda said:
I would not get the crane rollers. Get the Crane ductile iron. They are bullet proof. They will last forever. Get 1.6 on the intake and 1.5 on the exh. That is what Jim at Racer Brown recomended for me. 378 inch 340 with a Mighty 650.. Call Don at FBO. He can hook you up.
Click to expand...
Is that with a single or dual pattern cam?
 
It's a dual patten cam, specs are advertised.

The 1.6 rockers will not degrade streetablity. Just prep the head and match the springs to the new lift.
Dependent of head flow balance, different rocker ratios can help.
 
I'm one of those who think the right cam will help more than rocker ratios. It has been shown that a quicker opening will aid the entire power curve, but in some cases, this will jus cause geometry issues with "non std" ratios. You can get as high as 1.7 and 1.8 in exotic brands, butt he gains would be marginal, and there can be serious rocker to valve tip alignment and sweep issues with them. 1.6s arent that far off, but you will want to double check the sweep accross the valve stem tip, in addition to the pushrod clearance thru the head. I havent seen any issues with Crane (aside from the adjuster hardening deal a couple years ago, and the usual descrepancies in true ratios), but I'd consider them "budget" decent arms. The Cats and the like arent even worth considering IMO, defiantely better with sintered iron than them.
 
I too run the ductile iron rockers from Crane. Have for years and zero problems with them. They are a good solid rocker for the money. And I like the 1.6 ratio, it 'speeds' up the rate of lift and gives back some of the lift lost in the offset between the lifters and the pushrods not being in plane (small blocks). Terry.
 
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