stock to roller to 1:6 rockers

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roccodart440

roccodart440

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I read an article last night worth sharing.

They took a 350sb Chevy and ran it with 1:5 stamped rockers to get a base line.

They went to a 1:52 roller rocker and went 5.8/6.6 more

They went to a 1:6 roller rocker and went 14hp/16tq over the base line.


I'll post some more specifics later but this was pretty impressive to me.
 
Those results would tell me the engine was undercammed to begin with. It'll be interesting to hear the specifics of that base engine.
 
Where was that article published? If it was in a publication that had ads in it for those rocker arms, I would take the results with a grain of sand.

Certainly no throwing off on you for sharing. I would like to see the rest of it too. That's one of those things that sounds too good to be true.
 
moper said:
Those results would tell me the engine was undercammed to begin with. It'll be interesting to hear the specifics of that base engine.
Click to expand...

I'm going to agree with you in that a bigger cam would make more power I that engine but can't we say that about nearly any given combo, ESPECIALLY a street minded combo? True a cam with all the same specs and just more lift won't have any major affect if any on in manners but suppose the owner doesn't want to or can't change a cam?

Changing those rockers will give you less friction, more VT control and precision and best of all more HP and tq without hurting engine manners.

i'll post up the specifics later. It was a comp cam.
 
RustyRatRod said:
Where was that article published? If it was in a publication that had ads in it for those rocker arms, I would take the results with a grain of sand.

Certainly no throwing off on you for sharing. I would like to see the rest of it too. That's one of those things that sounds too good to be true.
Click to expand...

Hot Rod Magazine and no there was no advertisement or links after the article.
 
roccodart440 said:
.....can't we say that about nearly any given combo, ESPECIALLY a street minded combo?
Click to expand...


I don't think so. I realize it's just a computer program.....and some people don't like it, BUT my desktop dyno shows that a cam that is "too big" will lose power in the band the engine was designed for. While it may ultimately make more power "up high" everywhere else suffers.

So if you're not building an engine to make its best power at its highest RPM, a bigger cam than the engine was designed for is useless. Least that's this old crusty's opinion. lol

RustyRatRod
Copyright 2014
All rights reserved
 
roccodart440 said:
Hot Rod Magazine and no there was no advertisement or links after the article.
Click to expand...

It doesn't have to be with the article.....if there are any ads in the magazine at ALL regarding those rockers, I would be skeptical. I guess I'm just a cynic. LOL

Remember too, we're talking about the difference between apples and oranges. The Chevy heads are archaic in comparison to the worst Mopar head......IF they are using a stock Chevy head. Even the famed Bow Tie head is not much better than say an X or J or any of our stuff with 2.02s and 1.60s. So you have to take that into consideration too.

Course the LS stuff is a completely different animal. lol

I remember all too well when Super Shops was here. All they stocked was one line of Erson cams. They all had low lift. Then they'd try to push the higher ratio rocker on everybody to make a big sale. I always thought that was funny.

I am sure the higher ratio work in their element. Say if you already have a cam you want to use and you want more lift. But if you're building from scratch, I always say just pick the right cam to start with.
 
It's all about geometry.
Roller rockers would be more accurate in ratio vs a OEM stamped rocker.
A 1.6 would give more lift, but it also slightly increases the rate of the lift compared to a 1.5
Put a 1.6 on an old school reliable grind and you now have a faster ramp + a little more lift.
 
I can see where they have their place on an existing (stockish)engine, and agree with the gain due to the geometry comments, but I have to agree with the others on the magazine comments. That article is directed at chebbie guys. They're the ones that usually fall for the rockers add 40hp, 50hp main bodies, 40hp headers, 20hp flowmasters, etc cause they all running around with 650hp 327's lol.
 
Engine was a 350. Xe268 comp cam. 750 demon. Performer rpm intake. Trick flow heads.

1.5 rocker. 389hp/407tq
1.5 roller. 401/412
1.6 roller. 414/423

Knock it off with the Chevy vs. mopar crap. This test is very comparable.
 
One thing I did not mention before is a SBM lifter/pushrod angle loses around .015-.020 lift from published cam specs.
Example .480 lift Comp Cam
.320 x 1.5 = .480 - .020 = .460
.320 x 1.6 = .512 - .020 = .492
.032 difference with just a rocker swap should add HP
 
roccodart440 said:
Engine was a 350. Xe268 comp cam. 750 demon. Performer rpm intake. Trick flow heads.

1.5 rocker. 389hp/407tq
1.5 roller. 401/412
1.6 roller. 414/423

Knock it off with the Chevy vs. mopar crap. This test is very comparable.
Click to expand...

That's cool, but stop bein a butt. Nobody knew the combo till you posted it. So comparisons are natural.
 
Was just poking some fun is all.


Same lift with 1.6 , but on a milder lobe. Would this be easier on the cam/lifter/valvetrain than achieving lift solely off the cam with 1.5?
 
George this is my fear. I ran 1:6's on my last 440. It was notorious for breaking adjusters. They were crane gold race rockers. It eventually ate the mpp cam.
 
GeorgeH said:
Was just poking some fun is all.


Same lift with 1.6 , but on a milder lobe. Would this be easier on the cam/lifter/valvetrain than achieving lift solely off the cam with 1.5?
Click to expand...

I know. I thought it was hilarious. If I've heard one chevy guy say "500 HP" I've heard a thousand.

IMO, no. I think the higher ratio introduces more stress in a valve train otherwise designed for a 1.5, but then, what the heck do I know?

lol
 
RustyRatRod said:
I know. I thought it was hilarious. If I've heard one chevy guy say "500 HP" I've heard a thousand.

IMO, no. I think the higher ratio introduces more stress in a valve train otherwise designed for a 1.5, but then, what the heck do I know?

lol
Click to expand...

i thought a 350 chevy could make 500 hp with just a cam upgrade .
 
RustyRatRod said:
I know. I thought it was hilarious. If I've heard one chevy guy say "500 HP" I've heard a thousand.

IMO, no. I think the higher ratio introduces more stress in a valve train otherwise designed for a 1.5, but then, what the heck do I know?

lol
Click to expand...

My thinking was, and I might be way off base, say for a given lift both being the same, using a 1.6 on a milder lobe, the difference in rate of acceleration would be from the fulcrum of the rocker to the tip, while the 1.5 on the larger cam lobe has to accelerate the lifter,pushrod, and 1/2 rocker additionally.

I either got my thinking cap on or my dunce cap, I'm just not sure lol

It's been a long time since high school physics, mass times rate of acceleration, inertia , speed, kinetic energy , blah blah blah. whatever the formula would be. Weight when speed is applied increases exponentially not in a straight scale. Just thinking would be less mass at speed with 1.6 times 16 at 6k rpm lol
 
I don't know. That's putting WAY more thought in it than I want. I just pick a good cam for the stock rocker ratio on the engine I am building and go for it.
 
roccodart440 said:
George this is my fear. I ran 1:6's on my last 440. It was notorious for breaking adjusters. They were crane gold race rockers. It eventually ate the mpp cam.
Click to expand...

Most mp cams have a pretty aggressive profile? Coupled with aggressive rocker ratio and my statements in my previous post about mass and that leads to spring pressures. Add 1.6(read as rate of lift) to mix and you might be over the spec'd springs. Just thinking out loud as many pull it off without issue
 
mderoy340 said:
One thing I did not mention before is a SBM lifter/pushrod angle loses around .015-.020 lift from published cam specs.
Example .480 lift Comp Cam
.320 x 1.5 = .480 - .020 = .460
.320 x 1.6 = .512 - .020 = .492
.032 difference with just a rocker swap should add HP
Click to expand...


The sb mopar will lose Cos 11 degrees (0.98162718344) x gross lift...difference between the lifter valley at 59 degrees and the valve train at 48 degrees...

stock rocker will lose lift due to their inaccurate ratio....
 
roccodart440 said:
I'm going to agree with you in that a bigger cam would make more power I that engine but can't we say that about nearly any given combo, ESPECIALLY a street minded combo? True a cam with all the same specs and just more lift won't have any major affect if any on in manners but suppose the owner doesn't want to or can't change a cam?

Changing those rockers will give you less friction, more VT control and precision and best of all more HP and tq without hurting engine manners.

i'll post up the specifics later. It was a comp cam.
Click to expand...

I think you need to assign a priority to the gains. Or maybe a better way to say it is what gave the payback?
Given the cam and the heads used and the results:
Stock stmped to perfomance aluminum 1.52 = 5.86hp over 1st test
1.52 aluminum performance to 1.6 aluminum performance = 8.14hp over 2nd test

How would you explain the gains on each? What factor do you feel influenced output the greatest?
 
Ok, if we can manage to keep this thread alive this long....i can give some feedback next may (beginning of racing season here). I´ll do the swap from 1.5 Rockers (crane ductile) to 1.6 ratio (mancini, HS bodies with roller tips) this winter. I´d like to open the valve a little more, with the 1.6 ratio i calculate around .580" minus losses due to geometry. I expect a little power gain, maybe a tenth in the quarter? We´ll see....

Michael
 
I think the 1st post is accurate and here's why you'll gain power in almost any engine. How much power you gain is a issue dependent to each engine.

Nevermind the mini gain in duration the rocker ratio upgrade does for you, pay attention to the increased valve lift. The valve has not open beyond the heads abilty to flow air.

Breath deeper my friends. Breath deep.
 
jimjimjimmy said:
i thought a 350 chevy could make 500 hp with just a cam upgrade .
Click to expand...

600 with carb and headers.

Seriously every chevy guy claims 500hp. A fact of life.


Geroge, good point on the MPP cams. They are supposedly cut for the bigger lifter diameter so they should be more aggressive. THe 1:6 would make it worse.
 
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