Rocker Arms... a good upgrade?.

[TranceRx7]

Hey, Since this is my first post.. I should just like to say hello to everyone.

I have a 87 Mazda Rx7 with a early 80's Chev 350 in it. The motor is .030 over, flattop pistons, headers, weiand stealth intake, weiand elec. water pump, Holy 4160 600cfm carb, 882 heads, .447/.447/.222dur camshaft, k-motion valvesprings.

Anyways, to get to the question... I was thinking on purchasing a set of Roller Rocker Arms, or Roller Tip Rocker Arms... But I dont know much about them... I'd like to get a 1.6 ratio, as I dont find my motor lacking at the higher RPMS (isn't changing the ratio of your rocker arm almost the same as changing the lift on your cam?.).

The other issue I have is weather it is worth it to get a nice set of Aluminum Full Roller Rockers 1.6, or be cheap and buy steel Roller tip rockers 1.6. Think I would notice much differenece in performance between these?.

Any help or advice would be much appriciated. Thanks a lot.

Chris.

P.S. Anyone know what kind of H.P gain would be expected from this upgrade?.

[MrPbody]

Chris,
Depending on what exactly you're after, changing rockers can gain you some. Your .447" lift will become .477" lift using the 1.6:1 ratio. Duration @ .050 will increase ever so slightly.
Comp Magnums have proven to be very good quality. Whether or not going to a "true" roller rocker would help more, is a matter of considerable debate. Two things that are not in question: Roller rockers (true or "tip") will typically give you power gains, both from increase in ratio (imitates more cam) and the accuracy of all cylinders having equal lift/duration, as stock stamped rockers can vary as much as .050" or more, in manufacture.
Are they worth it? You bet. Do you need high dollar race rockers? Probably not. Another issue is with aluminum rockers. Aluminum has a propety known as "work hardening". That is, with all the heating/cooling cycles, the aluminum tends to get progressively harder. This can be good to a point, but beyond that, they become brittle, and can fail without notice. The more modern alloys are much better at resisting this, but it can still be an issue. The alternative is steel rollers. Big money...
I would guess an increae of about 4-5 percent in power. WARNING!!! Be sure to check for both coil bind AND valve-to-piston clearance. You're probably okay on the valve-to-piston with only .477 lift, but coil bind, especially if you have rotator caps on the exhaust, is a very real issue.

Jim

[TranceRx7]

Great reply. Thanks. . Anyone else?.

[Mr. Horsepower]

hey hows it going?
to answer your question. Yes it will increase your lift as the reply above stated. you will also notice a change in throttle response. They give less friction and the less friction makes more power. If you would go with 1.6 true rollers like from crane cams you will get anywhere from 15 to 30 horsepower gains. I think you would be impressed with the upgrade.

[MagicRat]

Good posts. Mr. Pbody is correct about the aluminum roller rockers. The older designs can fail in as little as 10 hours of use,depending on the cam profile and valve springs. They are truly race-only pieces. The steel versions are, of course much more durable.