went from 1.5 to 1.6 rocker arms
with a .520/.520 cam
would the 1.6 increase the cam lift ??

 

Of course it will. Increasing the lift is the whole point of higher rocker arm ratio's. Multiply your cam lift by the rocker arm ratio to get your total valve lift.

The question you need to ask yourself is will it make any difference in your specific application?

 

Can the springs handle it is another question.

 

You'l pick up roughly.033" lift. As for the springs, what heads are you running, if they are stock I doubt it, hard to say w/o knowing what you are running...

 

comp cam springs,
camel hump heads-plained,ported,polished,bigger valves

 

Have you run this engine with the new rockers?

 

yes i have and also checked valve to piston clearances and there is .100's

 

I was more concerned with potential coil bind and retainer to guide boss interference.
The 1.6 rockers have increased the lift from your previous .520" to .555".
That's getting up there.

 

yes i was concerned also untill i talked to my machine shop("pro stock" stock car racer, and the person who sold me the valve train (9.00 second racer"owner of the racing shop") ...the only problem i am having now is its street-ability, i/e setting at the stop lights .i cant get a decent idle

 

The addition of 1.6 rockers will not have any affect on idle quality you have another problem.

Retainer to guide boss interference generally occurs at .600+ lift unless you have VORTEC heads.always good to check

 

Sounds like the rockers are not adjusted properly.

 

It's gonna lope hard w/ that kind of lift, are you running a stall speed convertor? If not it won't idle at a stop in gear. w/ that cam you probably need to be in the 2800-3200 rpm stall speed range...

 

That sounds more like piston-to-valve clearance. Retainer to valve stem seal is usually more like .475" or so on an unmodified head, IIRC.

I wouldn't expect a cam with .555" lift to idle all that well.

 

valve lift has very little affect on idle, duration,overlap etc. play more of a role in idle...

 

True, but that thing's likely to have a healthy duration to go with the lift.

 

I'd bet it needs more timing advance...especially if it has low compression (9.5:1 or less), tight LSA and lots of duration. Shoot for 50* or more at idle and slow speed. But, if it was really good before and now it is really bad...try adjusting the valves again.

 

Yes, but you don't get that kind of lift w/o some big duration numbers...
The question is the converter, I run 583/583 lift, if I did not have a stalled converter it would barely be able to idle in gear. W/ my convertor I can idle @ 650-700 rpm all day long

 

We're using 1.6 rockers here, increasing the lift without creating the problems long duration does. My little 224 degree cam pushes the valves .500 with 1.6 arms, without a stall converter or idle issues.

 

The cam I'm running now is a solid roller at 236 @50 with .550 lift on a 110 LSA. This is on a motor with close to 11:1 compression and 8.5:1 DCR and it still likes about 15 degrees initial. My old cam (way to much cam) was a 246 @50 with .510 lift, hydraulic flat tappit, and wouldnt idle with less than 18 degrees initial timing. This is with vacuum advance disconnceted. If I had less than that, you could watch the headers glow within 10 minutes of turning the motor on as the fuel was still burning while going in the exhaust. The motor also had no power.

 

(It's gonna lope hard w/ that kind of lift, are you running a stall speed convertor? If not it won't idle at a stop in gear. w/ that cam you probably need to be in the 2800-3200 rpm stall speed range...)


Lift has nothing to do with how a cam is going to "lope" thats is based off of centerline and duration

 

Your 224 is a weenie .468 or so before the 1.5s are on it. He's already over .520 with the 1.5s, that's going to come with some duration. It's a pretty big cam however you measure it. Look at the Lunati 30121, .520/.520 and 240/240 @ .050.

I'd try it with at least 3000 RPM stall, lock the centrifugal at 34 degrees, and then give it as much non-ported vacuum advance as it wants.

 

I know.

 

How 'bout a 214/214 @ .050 .603"/.586" That's weenieER.

Jake

 

Technically, NO, Not CAM lift; not even Lobe Lift; but instead VALVE LIFT. Gotta keep all these names straight.

Jake

 

Lifter preload. It's a vocabulary thing.

Jake

 

True. Minimal.

Jake

 

214/214@ .050" .603"/.586" High lift - short duration.

Jake

 

Yeah no kidding, but w/ that kind of lift comes more duration, it's a given.... This ain't my first rodeo pal!

 

Mmm, yeah, I see what you mean.
The rocker nuts adjust the lifter preload. The pushrod length adjusts the rocker position. Cam lift pushes the lifter/pushrod/rocker. The rocker ratio effects the valve travel.

We CAN have relatively short duration and still acheive high lift by grinding a fast opening ramp with a tall nose/high lift and manipulating the rocker ratio. Good springs and a gentle closing ramp are necessary at this point. The roller trend has taken advantage of this theory.

 

One of the major benefits of recent (within the past several years) testing done by the major cam companies is they have been able to create camshaft lobes which result in higher valve lift while, at the same time, keeping the duration on the short(er) side.

They increased, what we usually refer to as the aggressiveness of the cam's lobes. The trick is to open the valve as quickly as possible, accelerate it quickly but not so fast as to cause the lifter to fly off the lobe at max lift - only to come crashing down on the closing side of the lobe. It's a fine balancing act, to be able to achieve that without going too far but the Big Boys have nailed it.

Comp's been doing it for a while with their XE and XFI lobes and Lunati is now offering lobes of a very similar design. Of course, the entire valve train has to be up to snuff to be able to repeatedly handle those lobes and, according to Comp, stock valve train parts won't cut it.

So although long(ish) durations use to always accompany high valve lift cams, the most recent cam offerings have taken a big bite out of that requirement. Of course, one can always pump up the valve lift by making changes in the rocker arm ratio.

Running Comp's MOST aggressive lobes calls for either more spring or lowering the max RPMs.

Hope this helps.

Jake

 

what is the compression you might have over cam it sound like you need at least a 10.5 to 1 to run that cam