Reason for using a "slow" ramped intake lobe?

[lada ok]

Why does some person design a cam with 0.026 " lash
Is he an idiot, .. or is he anticipating the use by of idiots

The thing is, having 0.026 " seems like a dreadful waste to me .... you can have an identical cam with 0.006 " lash and gain 0.020 " lift
Although one advantage with large lash ramps is the ability to ' tune ' a cam to a particular track / situation
So maybe he's smarter than I think he is

[RL]

Why does some person design a cam with 0.026 " lash
Is he an idiot, .. or is he anticipating the use by of idiots

The thing is, having 0.026 " seems like a dreadful waste to me .... you can have an identical cam with 0.006 " lash and gain 0.020 " lift
Although one advantage with large lash ramps is the ability to ' tune ' a cam to a particular track / situation
So maybe he's smarter than I think he is

Odd-ball lash is pretty common when dyno testing. It gives you an indication of which way to go with a cam. ie if it makes more power with bigger exh lash it might tell you the exh lob is too big and to drop a rocker ratio, like this engine has.

To me this just seems like someone has been doing a lot of testing.

Slow ramp and large lash seems counter intuitive, but maybe he found something with less lift because the port was air limited and a restriction. Maybe the lifter suddenly jerking open late does something.

[lada ok]

Why does some person design a cam with 0.026 " lash
Is he an idiot, .. or is he anticipating the use by of idiots

The thing is, having 0.026 " seems like a dreadful waste to me .... you can have an identical cam with 0.006 " lash and gain 0.020 " lift
Although one advantage with large lash ramps is the ability to ' tune ' a cam to a particular track / situation
So maybe he's smarter than I think he is

Odd-ball lash is pretty common when dyno testing. It gives you an indication of which way to go with a cam. ie if it makes more power with bigger exh lash it might tell you the exh lob is too big and to drop a rocker ratio, like this engine has.

To me this just seems like someone has been doing a lot of testing.

Slow ramp and large lash seems counter intuitive, but maybe he found something with less lift because the port was air limited and a restriction. Maybe the lifter suddenly jerking open late does something.

Yes good thinking, and I agree wholeheartedly, ... there's more than one way to skin a cat

[houser45]

Heck with it Im going to run the darn thing, Is .008 the tightest you could run the lash up too on a iron block, alum head race engine? I may start at .010"?

[Biteme]

I don't see how the lash is related to the aggressiveness of the lobe. 2 different things.
And an aggressive lobe doesn't always make more power than a slower lobe.
And you can have a lobe that's fast opening up to say .200 valve lift, then slow up to peak lift, hold it there for as long as possible, then drops off the nose of the lobe quickly, then gently sits the valve back onto the seat

So to classify a lobe as sluggish or aggressive based on its lash is wrong IMO.

[lada ok]

Heck with it Im going to run the darn thing, Is .008 the tightest you could run the lash up too on a iron block, alum head race engine? I may start at .010"?

YEAH GO FOR IT
set the lash to say 0.020 " cold run up engine till pretty warm, stop and recheck lash check the difference ... eventually you'll be able to check it hot or cold and know your not less than 0.000"

[houser45]

The only reason I know its not a very aggressive lobe is because I called the grinder who had it on file and gave them the serial number, He said it wasn't a very fast ramp and I would benefit by having it reground to a more aggressive lobe. The lash setting is wrote on the cam card, He knew what lobe was by the serial number. All of the companys newer or more modern lobes run a lash of .012" He said I could run the lash at .012 instead of .026. So answer this, why does some of iskys tried and true ascs roller camshafts run a lash of .024" intake and exh, and most of the huggins, bullet and comp stuff use .008 to .014 lash? Is the isky rad645 outdated by modern standards?

[BigBro74]

the reason the lash spec doesn't really matter much is the lash ramp design is what that spec is based off of- your engine doesn't care what the lash is, it just cares when and how much the valve moves.

besides- a slower, more gentle intake lobe may run way more rpm before valvetrain crash than a real fast lobe, given about the same or maybe even less spring.

it may also be way easier on parts!

how many laps do you plan on running this engine before freshening?

if you tighten the lash way down your'e gonna' think theres something wrong with your induction system, from my experience engines with real tight lash are not as responsive-partly (mostly) due to the extra (and usually unwanted) duration without much lift.
JMO- run it

[Biteme]

I wouldn't tighten the lash down too far. All it does is make the valve spend more time in an area where there's not enough lift for significant flow.

[user-23911]

Lots of lash means lots of noise.
Noise is lost energy and ends up with lots or un nessecary wear.
You don't want noise if you've got EFI and a knock sensor.

My own cams, I've plotted them out, degrees vs lift.
Comparing a factory mechanical roller cam to a factory hydraulic roller cam, the mechanical cam will have a more gentle opening ramp in order to take up the lash slowly.
With a hydraulic cam, it doesn't matter because the lash is zero.
But the closing ramps, they depend on the load on the springs, which need to heavy enough to so they don't float at high revs.

[Stan Weiss]

The only reason I know its not a very aggressive lobe is because I called the grinder who had it on file and gave them the serial number, He said it wasn't a very fast ramp and I would benefit by having it reground to a more aggressive lobe. The lash setting is wrote on the cam card, He knew what lobe was by the serial number. All of the companys newer or more modern lobes run a lash of .012" He said I could run the lash at .012 instead of .026. So answer this, why does some of iskys tried and true ascs roller camshafts run a lash of .024" intake and exh, and most of the huggins, bullet and comp stuff use .008 to .014 lash? Is the isky rad645 outdated by modern standards?

Just what does that do for you? How do you know anything about the lobe design from the lash ramp design?

Stan

[Cogburn]

Another possibility is how fast power drops off past say 8000rpm, some guys like to be able to turn a lot of rpm for slide jobs, passing, lots of restarts. On a short track with restarts turning 9200+ at times is not unreasonable. I've seen some engines that make good power and win races at bigger tracks won't turn much more than 8400rpm period.

[RL]

Heck with it Im going to run the darn thing, Is .008 the tightest you could run the lash up too on a iron block, alum head race engine? I may start at .010"?

If it's a successful engine with that cam, it's probably ok, if not, probably chuck it.

It's the aggressive exh lobe that makes me think there is something to it, because he could have easily pick an aggressive int to match it.

If it's just the guy's theory and doesn't have success, or he swapped out the good one before you got it, I would maybe question it.

Drive-ability is a big part in traction limited racing. We had an engine where we found massive mid range torque with a different fuel curve. At the track they guy couldn't handle the extra torque and would wheelspin constantly, so he put the fuel curve back. He wasn't too bright because he could have used the throttle properly, or used a taller gear, but it was easier for him to use full throttle out of corners. Maybe the cam does something for drive-ability.

[houser45]

okay here is the cam card info, I know it doesn't tell much but I will roll it on the Cam pro when we get the computer up and running again and report what it rolls.
Int. Exh.
dur. at .050 266 272
Lobe lift .446 .430
Lobe sep. 106
timing events at .050 31 open 55 close int. 66 open 26 close exh.
seat duration at .020 299 302
valve lash hot .024 .014

[modok]

I'm not sure what part is of this is slow ramp. The acceleration phase is usually all done before .050 lift. At .025 lash there's nothing gentle about it.