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Old 09-09-2005, 12:14 AM
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1.5 vs 1.6 roller rockers?

Hey guy's, eventually ill get my motor up and running soon, that is if i ever get finnish with wireing the dash board together. But a buddy of mine told me that he has a set of 1.6 roller rockers, that he would unload real cheep if i wanted a set for my 350sbc. So i thought idd post to get some oppinions. I already have a set of 1.5 stamped steel rockers with a roller tip, from summit on the motor right now. The motor is a 9.0:1 c/r, .030 sbc 350,with KB hyper flats, sitting .010 in the hole, WP s/r torquers on top of a set of .028 GMPerformance head gaskets. A Comp EX270HR cam with (.495 in -.502 ex) @ (218 in -.224 @ 50)(1600 - 5400 rpm range). The P/V clearance was twice as much needed with this cam. So i know i can go with a set of 1.6 rockers if and when im ready for a set. The ? is, is it worth the effort to use a set of 1.6 rockers in my case. The motor is in a 76 C10 swb PU,with a saginaw 3speed, and 3.42 gears, 28" tall tire.

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Old 09-09-2005, 01:39 AM
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The only reason I can see to buy 1.6 rockers is to increase cam size because you bought the wrong cam in the first place.
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Old 09-09-2005, 01:43 AM
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I switched to 1.6 personally and liked the results. A lot of it depends on the head flow. The S/R's are pretty decent heads, you can probably get a little more flow out of them with that extra cam lift but it's not guaranteed. I have never personally heard a good reason why 1.6's would hurt power so I don't think you have anything to lose.

Sounds like your piston-valve clearance will be good but don't forget to check coil bind, as your lift will go from .502 to .535.

Good luck.
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Old 09-09-2005, 01:46 AM
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Quote:
Originally Posted by bracketeer
The only reason I can see to buy 1.6 rockers is to increase cam size because you bought the wrong cam in the first place.
This makes sense and it seems that most people who build their combos planned from scratch always use 1.5's.

However... The reason I decided to go with 1.6's was because in the hydraulic flat tappet cam category, I couldn't find anything with the kind of lift I was looking for without have excessive duration for my street needs and powerband. Now once you're talking hydr. roller or solid roller, plenty of lift is found with most durations.

Just my view on it, but I am no technician or pro engine builder.
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Old 09-09-2005, 09:26 AM
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ThanX (KNanthup) for the heads up on coil bind, but the springs i went with are a set of beehive springs from comp, that work with roller cams. Not real sure of the allowed lift at the moment, but i do know that they required a .100 longer valve to get the installed height right.
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Old 09-09-2005, 11:26 AM
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1.6 rockers are a good idea on motors that have heads that continue to gain substantially in flow beyond where the lift of your current cam is. As mentioned before, if you want a cam that will act in a lower powerband, ( so you have to go with less duration) but you want to try to take advantage of your heads, 1.6's would be a good idea. I have a friend that had a 383 built that had heads that really started to take off around .450 -.500 lift. He wanted to stick with a cam in the high 230's to low 240's at .050 to keep the cam in the powerband that he wanted. All of the hyd flat tappet cams in that range had around .500-.510 lift. In his case, 1.6 rockers took his lift from .500 to .530 which was better for the heads while the duration stayed close to where he wanted it. A case where 1.6 rockers would be a bad idea is with a set of heads like the vortecs in some cases. Those heads drop off in flow above .500 lift. If you have a cam with .490-.500 lift and put a set of 1.6 rockers on it, the fact that you are now getting .530 lift could hurt performance.

Take a look at this, and compare the powerband, lift and duration of the xe274h cam to the xe294h and then the xe274h with another .03 lift but similar duration. As an example I think the xe274h cam with a set of 1.6 rockers would be a much better match for your engine than the xe294h but both cams would have the same intake lift (xe274 w 1.6's=.520 xe294=.519)

http://www.compcams.com/Technical/Cu...ML/128-169.asp

Your flow numbers, scroll down
http://www.chevyhiperformance.com/te...98/index4.html

Adam

Last edited by firestone; 09-09-2005 at 01:08 PM.
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Old 09-09-2005, 01:46 PM
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Quote:
Originally Posted by firestone
1.6 rockers are a good idea on motors that have heads that continue to gain substantially in flow beyond where the lift of your current cam is. As mentioned before, if you want a cam that will act in a lower powerband, ( so you have to go with less duration) but you want to try to take advantage of your heads, 1.6's would be a good idea. I have a friend that had a 383 built that had heads that really started to take off around .450 -.500 lift. He wanted to stick with a cam in the high 230's to low 240's at .050 to keep the cam in the powerband that he wanted. All of the hyd flat tappet cams in that range had around .500-.510 lift. In his case, 1.6 rockers took his lift from .500 to .530 which was better for the heads while the duration stayed close to where he wanted it. A case where 1.6 rockers would be a bad idea is with a set of heads like the vortecs in some cases. Those heads drop off in flow above .500 lift. If you have a cam with .490-.500 lift and put a set of 1.6 rockers on it, the fact that you are now getting .530 lift could hurt performance.

Take a look at this, and compare the powerband, lift and duration of the xe274h cam to the xe294h and then the xe274h with another .03 lift but similar duration. As an example I think the xe274h cam with a set of 1.6 rockers would be a much better match for your engine than the xe294h but both cams would have the same intake lift (xe274 w 1.6's=.520 xe294=.519)

http://www.compcams.com/Technical/Cu...ML/128-169.asp

Your flow numbers, scroll down
http://www.chevyhiperformance.com/te...98/index4.html

Adam
Very good resource there. They do have the flow chart for the S/R's too. Check out the flow at lift and tell me if you think that extra lift will get more flow in
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Old 09-09-2005, 02:18 PM
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Rockers

I want to know if you can put 1.5's aluminum roller rockers on the intake and 1.6's aluminum roller rockers on the exhaust?
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Old 09-09-2005, 03:39 PM
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Quote:
Originally Posted by LivenInTheFastLane
I want to know if you can put 1.5's aluminum roller rockers on the intake and 1.6's aluminum roller rockers on the exhaust?
Sure you can. A lot of guys do that to help the exaust side flow if it's weak (which on sbc's it almost always is). You can buy split ratio sets directly from the manufacturer.
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Old 09-09-2005, 04:40 PM
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It looks to me like your heads are still gaining in flow from .500-.600 lift, so I think the extra lift from the 1.6 rockers can only help you.

Adam
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Old 09-09-2005, 11:27 PM
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I switched to a set of 1.6 from 1.5 and did notice a difference in power. This allowed me to have a more lift and a just a little more duration while allowing my motor to have the same vacuum
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