Tin Indian

Here is one for the cam gurus here.

Lets take 2 identical lift and duration cams here.

#1 has an LSA of 114 and an IC of 110. That cam would have 4 degrees of "built in" advance

#2 also has an LSA of 114, but an IC of 112. That cam would have only 2 degrees of "built in" advance.

Assume they both dial-in right on the money as per the cam card, so they will just go in dot-to-dot in the motor.

What advantage does the 2 degree built in advance cam have over the 4 dergree / or vise versa?

Thanks,
Ron

verbs

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Kimchee and Rice:
<strong>Here is one for the cam gurus here.

Lets take 2 identical lift and duration cams here.

#1 has an LSA of 114 and an IC of 110. That cam would have 4 degrees of "built in" advance

#2 also has an LSA of 114, but an IC of 112. That cam would have only 2 degrees of "built in" advance.

Assume they both dial-in right on the money as per the cam card, so they will just go in dot-to-dot in the motor.

What advantage does the 2 degree built in advance cam have over the 4 dergree / or vise versa?

Thanks,
Ron</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Isn't it vice versa??? Don't the extra degrees of advance bring the powerband lower in the rpm range?? I thought that was the purpose of the extra advance.

My question is, if advance brings the powerband to the lower rpm's just like a tighter lsa, does extra advance ground in affect idling and emissions just like a tighter LSA does???

If not, then why wouldn't everyone run 114LSA's with 6 degrees of advance ground in <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />

MelloYellow

verbs:
I keep pondering the same thing. With the 114 having such a high peak power, why hasn't anyone gone with SIX degrees advance via grind or dialed in with a Cloyes Adjustable?

I'm considering trying the 6* myself. I don't like spinning the engine so high. 4* ground here and thinking about dyno'ing another +2* with the Cloyes to bring the power down a bit more.

Anyone think I'll lose any peak power?

<small>[ July 12, 2002, 07:17 PM: Message edited by: MelloYellow ]</small>

Tin Indian

Well, you folks have asked the million dollar question. In fact, I read a post the other day where Mellow was just talking about this same thing. Good topic

Maybe one or more of the real cam savvy folks here can shed some light. It certainly deserves some interaction here.

Verbs.... Know doubt about it...Your correct... "Vice Versa"
Wonder if that is actually a legit word or just slang?

Come on cam experts.... Lets talk cam advance. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

Ron,

verbs

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Kimchee and Rice:
<strong>Verbs.... Know doubt about it...Your correct... "Vice Versa"
Wonder if that is actually a legit word or just slang?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Isn't vice versa Italian or Latin or something like that?? I don't think it's slang <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

This should be a great topic IMO....

GET IN HERE CAM EXPERTS!!!

<small>[ July 12, 2002, 10:50 PM: Message edited by: verbs ]</small>

Miles in Michigan

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Isn't vice versa Italian or Latin or something like that?? I don't think it's slang <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">It's Latin. The original pronunciation would have been more like "wee-kay ware-ka", but those crazy romans pronounced "cicero" as "kee-kir-o", so what do they know?

Two latin words: vice, a form of the noun "vix", meaning "place". Versa, a screwy form of the verb "vertere" meaning "to turn".

Why did I sqaunder my youth taking latin instead of machine shop or engine building classes?!?! <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />

Cam experts, where are you?

ChrisB

It is a bit easier to look at it from the viewpoint of valve opening/closing events than trying to generalize based on trends.

A wider lsa is going to make the intake close later as well as open later - and the exhaust open sooner and close sooner (keeping everything else constant).

Advancing or retarding the cam will cause all the valve opening and closing events to happen later or earlier.

It's not just a matter of "shifting the powerband" up or down - there will also be effects on the pumping effeciency of the motor itself. Which works best for you will depend on your specific setup.

Chris

Tin Indian

Which do you think would give the best low rpm part throttle response.

in-traffic snappy throttle response?

Tin Indian

Good link...
thanks

SStrokerAce

iTrader: (2)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Kimchee and Rice:
<strong>Which do you think would give the best low rpm part throttle response.

in-traffic snappy throttle response?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Less duration and smaller LSA.

My thoughts on the LSA and Cam Advance are this:

A high LSA is usually a result/fix of a overly large duration. The LSA is larger to create a better idle quality and driveablity. If you lessen the duration then the overlap will be reduced therefore you can run less LSA to gain even more torque. When you advance a cam 6 degrees to get the optimim tune out of an engine you really have the wrong cam in there. What you really change with the advance is the Intake Valve Closing point. That is the single most important point in cam timing. If you instead work with the LSA and duration in the begining to get the proper intake valve closing point you will have the same amount of HP as a larger duration cam and much more tq below HP peak. Advancing a cam should only be done to make up for chain slack or camshaft twist in operation. Other than that it's a bad way to fix a to large of duration cam in the first place. That's just my thoughts.

Bret

Tin Indian

Bret... Thanks,

I am planning on ordering a fairly mild cam (from what I see some of these folks using now <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" /> ) 220/220 .561/.561 114 LSA from Comp Cams. I am just putting it in dot-to-dot with the stock timing gears and a new Jwis single chain.

Car will have "Stage" ported heads milled .030" with 2.02/1.57 valves and 918 springs, LTs, LS6 intake, and an old Yank 2,800 converter.

I just dont know what IC to tell them to grind in.
110 for 4 degrees advance
112 for 2 degrees
or something else

Sure do like snappy part throttle response and a quick reving engine though......

<small>[ July 14, 2002, 03:38 PM: Message edited by: Kimchee and Rice ]</small>

AzzHauler

iTrader: (3)

So optimum advance would be 0? And how do you go about finding out when you want the intake valve to close? Big street torque is a winner for me.

SStrokerAce

iTrader: (2)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Kimchee and Rice:
<strong>Bret... Thanks,

I am planning on ordering a fairly mild cam (from what I see some of these folks using now <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" /> ) 220/220 .561/.561 114 LSA from Comp Cams. I am just putting it in dot-to-dot with the stock timing gears and a new Jwis single chain.

Car will have "Stage" ported heads milled .030" with 2.02/1.57 valves and 918 springs, LTs, LS6 intake, and an old Yank 2,800 converter.

I just dont know what IC to tell them to grind in.
110 for 4 degrees advance
112 for 2 degrees
or something else

Sure do like snappy part throttle response and a quick reving engine though......</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">that's not a bad call on a cam. I would almost look at the Hammer Cam 222/222 .563/.563 at 112LSA strait up.

It's hard to say what the IAC should be without getting a cam ground in the specs you listed then putting it on a dyno and getting an adjustable timing chain and dialing it in. I would not get any ground in and go with an adjustable set up if you really want to get on a dyno and spend the time getting it where you want it. Then again the chassis dyno accuracy/repeatablity is going to make it hard to find which cam setting is best since the difference could be very small.

Bret

SStrokerAce

iTrader: (2)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by AzzHauler:
<strong>So optimum advance would be 0? And how do you go about finding out when you want the intake valve to close? Big street torque is a winner for me.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">That's my theory is that optimum advance is 0. If you have the cam right you don't need to move the cam.

"And how do you go about finding out when you want the intake valve to close?" -- You ask someone who knows how to find that out for you. That's the best answer I can give. The long version I don't think I have the time to write. That's like writing an SAE paper on the subject.

ChrisB

I would agree that if you end up running something like 6+ degrees of advance/retard you probably need another camshaft.

But at the same time I wouldn't agree that 0 degrees is something you want/need to shoot for. Yes, you can change the duration, lsa to effect the valve events - just as advancing/retarding will also. But as mentioned above each of these changes is going to have different effects on the valve events - and you do need to keep the valve open to get air in and out, so at some point you can't simply just make the duration smaller - and narrow lsa's just aren't as friendly with these computers/emissions stations.

Advancing/retarding the camshaft is a easy way to play around with your setup without spending the money. I agree - I would rather see the cam ground to the specs you want, but money is an issue for almost all involved. I probably wouldn't go much farther than +-4 degrees advance/retard, but again, that's just a personal opinion.

The problem with coming up with general trend answers to questions like this is that it is all highly dependant on the setup of the motor. But to a small extent you can, *in general* achieve a little more cylinder pressure at lower rpm's by advancing the camshaft - at the expense of higher rpms - and vice versa for retarding.

the tricky part when trying to work it out on paper is that it's almost impossible to take the entire lobe profile into account with the tools we have available - and even keeping the adv or 0.05 duration constant you can have large differences in valve events on different lobe series, independent of lsa, ic, etc. changes.

Honestly trial and error is the only real method available to distinguish between similar cams. And to be honest a few degrees here or there isn't generally going to be a night and day difference.

Chris

SStrokerAce

iTrader: (2)

Chris,

I agree with alot of what you said that's a good post.

My experience is that if you can advance the cam 2 degrees and the duration is not stupid high then you can just lower the LCA down 2 degrees and get a better result. If you have to run a larger LCA to make the engine idle and work at low RPM then the cam duration is too big and it's a fix to a problem rather than the right cam.

Bret

Dom

iTrader: (2)

http://www.geocities.com/d_payton1/cam_info.html

Maybe this will help some.

<small>[ July 14, 2002, 01:01 PM: Message edited by: Dom ]</small>

Ragtop 99

iTrader: (7)

A lot of people grind in 2 degrees of advance just to account for timing chain stretch as the miles build-up. For the average person running a stock type chain, up to 4 degrees advance is not a big deal. I agree that 6 degrees is more than I would use.

The 220/220 114 will be a good drivability cam on the street. Good idle, low cam surge, easily pas emissions, and rev nicely to 6300/6400 shift point. For drag racing, the 112 LSA would improve your 60' given the low stall. It would help with highway throttle response when the converter locked and the car is below 2000 rpm. When the converter is unlocked, you'll be at 2500 rpm or more if you get on it, in which case the 114 LSA cam will do just fine.

FWIW, my first cam was 218/218 114 .563 112 I/C.

Tin Indian

Ragtop 99...

I was seriously considering a 218/218 .563/.563 114 LSA exactly like your first cam.

Do you think you really gained that much after switching that cam out for a more aggressive grind? Or were many other things done to the engine at the time of the switch to make it difficult to just judge the cam?

thanks,

Oh, BTW, the 220 cam I said I was going to order is almost exactly the same as the 218 (well, 2 degrees more duration). I wonder if there would really be much of a difference in idle, surge, throttle response, and WOT/high rpm power (218 vs 220). Again, I will be using headers with cats, ported heads, and an LS6 manifold.

I know a 224+ cam will make more power, but I would rather go "light" on the cam just for near stock driveability in commuter traffic, etc.

<small>[ July 15, 2002, 11:36 AM: Message edited by: Kimchee and Rice ]</small>

Ragtop 99

iTrader: (7)

Too many things changed when I went to the 224 cam so i don't have a valid baseline. TR says the 224 is good for 5 RWHP peak over their 220 cam, so figure you are not giving up a ton with the 220 cam. I think the 220/220 114 is pretty nice compromise between power and drivability.

Probably only 2-3 average RWTQ between a 218 and 220 cam. I doubt you could tell the difference in drivability. If you were going smaller than a 220/220 114, I would actually go down a 216/216 112, maybe 113 LSA. That would be very torquey and still idle smoothly around 800 rpm. Top end on a 112 would probably be done early, so a 6200 rpm shift would be all you would need.