Mixed ratio 1.6/1.5 roller rockers for L98 '128 heads

E

Enuzio

Member
Hi everyone....

I'm looking for a recommendation for a mixed ratio 1.6/1.5 roller rockers on an L98 '128 aluminum heads....
I want to use full trunion rollers with 1.6 intake / 1.5 exhaust and keep the stock center bolt covers. This is a crusing / touring car ('86 C4). Also can I ditch the exhaust valve rotators? Are they really needed? I am interested in beehive springs here.

Any thoughts on this combo? A couple of months of casual browsing on various sites have not yielded any usable inforomation.

Thanks,

Enuzio
 
the exhaust valve rotators, are NOT mandatory but they DO tend to extend the life expectancy of the exhaust valves, many guys remove them and they generally don,t experience problems.
swapping to beehive springs with smaller and lighter weight retainers tends to allow your engine rpms to increase a couple of hundred rpm before valve control issues appear,if the rest of the combo also allows the increase
stampedcvrockersa.jpg

stamped rockers are cheap and dependable but decent roller rockers will frequently allow the engine to run at reduced friction loads, 10-15 hp gains are easily available, and in some cases even more is available especially with higher spring loads or a higher than stock rocker ratio.
the COMP CAMS STEEL roller rockers are one of the most durable and easiest to fit under the stock valve covers,but be aware some center bolt valve cover heads
require NARROW BODY self aligning rockers,
scorpion also sells them

http://www.summitracing.com/parts/SCC-SCP1084-1/


ID suggest reading thru these threads for much more related info

viewtopic.php?f=52&t=1719&p=4265&hilit=rockers+aligning#p4265

http://www.tpub.com/content/recoveryveh ... 4P_158.htm

viewtopic.php?f=52&t=1716&p=4250&hilit=beehive#p4250

viewtopic.php?f=52&t=126&p=1193&hilit=louis#p1193

viewtopic.php?f=52&t=2746

viewtopic.php?f=52&t=181
 
Thanks Grumpy....

Great stuff here...any thought on mixing ratios in an engine?

Best Regards,

Enuzio
 
Enuzio said:
Thanks Grumpy....

Great stuff here...any thought on mixing ratios in an engine?

Best Regards,

Enuzio
Click to expand...


that depends on the engine combo, having mixed rocker ratios in my opinion is a good tuning trick you l;earn to use to compensate for a less than ideal cam selection, or when theres a rather obvious need to reduce or increase the flow rates, that you find during the tuning process.
in an ideal world you'll seldom need to use higher ratio rockers as selecting, a cam profile that meets the engines needs tends to reduce the valve train acceleration and stress rates to a lower level than compensating with a higher lift ratio, but the mixed ratio rockers are also used as a tuning aid and can be used very effectively to diagnose restrictions in port flow,
EXAMPLE
with experience you'll find that if a 1.6:1 ratio rocker provides a noticeable boost you've probably under cammed the engine or the ports or exhaust are restrictive, if you find that going to the higher ratio hurts power you've probably over cammed the engine or the ports, or exhaust primaries on your headers might be to large.
 
Thanks for the insight....My thinking on my application....a 1986 Convertible with '128 aluminum heads, is to stay with the stock cam and run 1.6's on the intake, to inhale better and 1.5's to keep from over scavaging the exhaust. Does this make sense? Or is it more a trial and error type of thing?

Cheers,

Enuzio
 
Enuzio said:
Thanks for the insight....My thinking on my application....a 1986 Convertible with '128 aluminum heads, is to stay with the stock cam and run 1.6's on the intake, to inhale better and 1.5's to keep from over scavaging the exhaust. Does this make sense? Or is it more a trial and error type of thing?

Cheers,

Enuzio
Click to expand...


over scavenging the exhaust is rather RARE if your not just running headers,with matched tuned collector lengths,
as a full exhaust system behind the collectors tends to reduce the headers effectiveness
but your correct that the intakes normally benefit more than the exhaust from rocker ratio increases
 
Maybe I am asking this right, my engine will have gmpp 1.6 full roller rockers. I am checking all the clearances that I can find that I need to. The one I dont know about is from the top of the rocker to the bottom of the connecting nut that holds the rocker on the stud. Some of mine look to close not touching but close. Also I still have not figured out exactly where to measure with the 12 gauge solid wire that you bend into a u then 90 the ends. Am I going to measure the bottom front of the slot of the rocker to stud? Or the backside? Thanks much.
 
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