1.6 Roller Rockers - good idea?

[Heavy Z]

Hello, I've recently installed a comp cams XE268H in my 327 and I think a 274 would've been more to my tastes. Rather than yanking the cam, are 1.6 roller rockers an acceptable way to get more power with a hydraulic cam or do they create more wear/problems in the valvetrain? I've got edelbroch performer rpm heads and manifold, holley 650 double pumper, and stamped-steel 1.5 roller rockers. I've read some rocker tests and on paper the 1.6's look good, but maybe you guys have more real-world experiences to share on this issue.

 

Thanks,

 

Heavy Z

[grumpyvette]

in general its almost always better to just install the correct duration and lsa cam than to try and compensate with 1.6 ratio rockers, in most cases the gains are small and the problems they can cause with clearances and vailve train geometry make it a bad deal. now that being said, if the cam you running is close but just a little too low on duration and lift to match your needs retarding the cam index timeing about 4 degs AND adding 1.6 ratio rockers can get you maybe 20-25 hp more in the upper rpm range IF both your headers and intake manifold plus the intake ports on your cylinder heads can flow enough air that the cam your useing now is restricting the airflow into the cylinders

example

in my old 1968 vette

on my 383 running a crane #114132 cam

http://dab7.cranecams.com/SpecCard/DisplayCatalogCard.asp?PN=114132&B1=Display+Card

the combo of retarding the cam timeing and 1.6 roller rockers made almost 25 more hp over 5000rpm, but keep in mind that cam was really way to small for the combo, when I swapped to a crane #114681 cam

http://dab7.cranecams.com/SpecCard/DisplayCatalogCard.asp?PN=114681&B1=Display+Card

there was no gain at all!

[Kevin Shasteen]

My question I would ask you is, "Exactly what is it about how your engine performs-that you dont like?"

 

I hate to say this, as good of an engine that the 327 is, your problem may not be cam related but displacement related.

 

Your power that you want might not be found in another cam simply because the 327 is an engine that is known for its high rpm revability-not its low end torque...unless you add a turbo/supercharger.

 

Notice in grumpy's answer his 25hp gain was to a 383-which breathes very healthily (is healthily even a word?). Also your engine's ability to produce power depends on its ability to breath. Grumpy's 383 has 56cubic inches on the 327 not to mention a longer stroke for that much more added torque down low.

 

Go for the 1.6's; my only concern would be broken rocker studs w/the 327's high rev's. You may get away w/it for awhile-but wear and tear always manages to catch up to you, and at the least most likely time.

 

Your current cam's lift is under the .500 lift; I would agree w/grumpy-if you want to change your valvetrain's lift/duration, then do it by choosing another cam....not by altering the rocker arm's geometry.

 

Maybe gearing would be a better change for your needs. You have a good engine w/a great street cam. Have you considered slightly steeper gears for the little extra grunt under WOT?

 

Gearing might be the way to go; just thinking out loud! Hope you figure it all out.

 

Kevin,

(Yea,Still an Inliner)

[Kevin Shasteen]

Just looked thru last months Chevy High Perf magazine & noticed they had a 400hp 327SBC,

 

They used the stock 461 Double Hump Heads after having them professionally ported.

 

They also used Comp Cam's Xtreme Enerty Hudraulic Roller w/a Duration of 270/276 and Lift of .495/.502

 

Instead of Forged Pistons they chose to go w/KB Hyper Pistons w/small valve reliefs.

 

Their Intake Manifold was an Edelbrock Performer RPM; BTW-they said their best Dyno run was with a 1" Open Plenum Spacer under the Carb...their carb of choice was the factory L79 Holley 780.

 

This 327 seemed to pull pretty hard. It made 400 ft/lbs @ 4800rpm and 408 hp @ 5700rpm's.

 

Maybe you can swap your cam for that XE Hyd.Roller and I would still think about your gearing.

 

Hope this give you some hope-that light at the end of the tunnel is not a train about to run you over...it is the Federal Express truck bringing you a new Camshaft!

 

Kevin,

(Yea,Still an Inliner)

[Mike C]

I am not a fan of 1.6 rockers although my LT-1 does run a set. The cost on the Hydraulic Roller is significant compared to the flat tappet cam. (Over $500 for cam and lifters plus add for custom pushrods) I would consider a mechanical flat tappet such as the Comp 282S as a fine cam for your 327 to shift the power up in the RPM range. This if you do by another cam and lifters. IMO, the mechanical lifters give a broader powerband and more overrev on the top with at least as good an idle. This makes up for the trouble to occassionally lash the valves.

[Heavy Z]

Thanks Kevin and Grumpy, I appreciate your info and I'll tell you more specifically why I want to cam up, as I am very happy with my current cam. The problem isn't really a problem, but...it's soo neck-snapping responsive around town, I mostly have to throttle down so as not to look like a Duke's of Hazard extra or from complaining passengers. I'd give that responsiveness up for a cam that comes on a little later, like the XE274H comp cam. Then I wouldn't have to baby it, and power would come on like a team of hungry vultures a little farther up the rev band. I want to get some better quality roller rockers anyway, 1.5 or 1.55 if they are okay wearwise and geometrically speaking.

 

Thanks again,

 

Brett

[z ya]

Maybe some 1.52 Comp Magnums?

[Guest Anonymous]

My 2 cents.Almost every aftermarket cam company has a cam that is close to their competition,as far as lift and duration.One way they cheat each other is with ramp speed.(get the valve open to its advertised numbers quickly)Even with a mild cam,you want to run a heavier set of springs to maintian valvetrain stability.Higher ratio rockers excelerate the ramp speed even more.I have purchased cams for a different application that were made to run with a specific ratio. Make sure you have enough spring,so your cam followers can follow the cam like they are supposed to,not jump off the bump(hey,that rhymes).As Grumpy recomended,retarding the cam will give you more top end,but make sure you go the right way.Advancing it will make it run like a tractor.Most speed shops sell offset keys in different degrees(it happened again).