Can Modern Roller Rockers Help That Old-School Engine?

Colin
By Colin Wood
Aug 19, 2020 | engine, Roller Rockers, Pushrod

Pushrod engines are pretty uncommon these days (looking at you, Dodge), but quite a few older cars in some of our stables may still use the old-school way of opening and closing engine valves.

Getting more power out of these older engines can be pretty easy nowadays with advent of modern power-adders, but what if getting more power was as easy as upgrading the roller rockers?

We collected three different sets of roller rockers to see if changing the ratio can make more power. See the results for yourself over on Classic Motorsports.

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Gearheadotaku (Forum Supporter)
Gearheadotaku (Forum Supporter) GRM+ Memberand UltimaDork
8/19/20 5:28 p.m.

Well that was an eye opener...

It's so often that Dyno charts on speed parts start at 4000 rpm or higher. Unless you're building a dedicated race engine, I'd like to see a chart that starts at 1000rpm and goes to 7000 or red line. Now you have the complete picture.

ShawnG
ShawnG UltimaDork
8/19/20 5:47 p.m.

Funny, old fashioned rockers manage to last for hundreds of thousands of miles but nobody seems to be able to tell me how long it will be until I have to go digging for needle bearings in the oil pump.

I'd bet dollar per horsepower, these are near the bottom, along with ignition upgrades.

Robbie (Forum Supporter)
Robbie (Forum Supporter) GRM+ Memberand MegaDork
8/19/20 10:26 p.m.

Yeah, a different ratio rocker is one thing. But just adding a roller to the end of the valve?

 

Vigo (Forum Supporter)
Vigo (Forum Supporter) MegaDork
8/20/20 9:38 a.m.

Part of adding a roller to the end of the rocker is about not excessively side-loading the valve stem as the rocker tip sweeps farther across it when you increase valve lift, which accelerates guide wear. And without a roller contact point on the tip of the rocker arm, when you increase cam lift you can often get to a 'bad angle' between rocker tip and valve stem which puts all the surface loading into a tiny area which accelerates wear there too. I mean if you think about a valvespring having like 300 lbs of open pressure and all that 300lbs being applied to a ~5/16" or smaller circle which is the the valve stem, and then reduce it to only a fraction of that space, and then make that contact point grind side to side as it goes up and down, it makes sense why roller tips become a big durability upgrade when you increase both valvespring rate and cam lift. 

 

Tony Sestito
Tony Sestito PowerDork
8/20/20 9:52 a.m.

I opted for roller rockers on my Pontiac 400 build about 12 years ago after reading that people were seeing up to 20hp gains swapping from standard rockers. While I found it hard to believe, I went for it, since I needed to buy rockers anyway (my heads didn't come with any). I will tell you this: MAKE ABSOLUTELY SURE YOU LOCK THEM DOWN CORRECTLY!!! Check them all, and then re-check them again!




I dodged a huge bullet when this happened; the pushrod was still straight, valves were OK, and nothing came out for air. I bolted it back together, checked them all again, and it's been fine ever since.

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