Good morning.i am looking fo an anwer to y this wont work vs what people reccomend. I have a cam at .050 that is 224 232 .629 .602 115+3. It has -3.5 degrees of overlap according to the cam card actual valve events. If i move the lsa down to 113.5 and dont touch the icl i get 1 degree of overlap. Id i make the ecl 112 it give me 4 degrees of overlap will either change help this camshaft?

 

Since you would have to get a new cam to change overlap anyways, you may want to run it by whomever it is you're ordering from. Since you didn't post any information about the vehicle, the engine, or intended use, I'm guessing you're unaware that that is important information in determining what valve event changes will help or hurt. The person you orde from may be able to coax that info out of you and help you make the best decision.

 

Before I go any further, if you're asking - can I simply adjust the LSA on THIS CAM, the answer is no, it's already ground into the cam, unless you're running DOHC.

Now, if you're asking about buying a new cam with a different LSA, it really depends on your goals, engine size etc, as to whether it would help. For example, if you want the motor to rev, then opening the exhaust valve later will inhibit higher RPM breathing. Or another example, if you're planning to run turbo, you want the negative overlap. Now, if it's a truck engine, you might want to delay the exhaust valve opening to maximize torque, but you'll sacrifice breathing at higher RPM to accomplish this.

I just calculated your valve events as follows (and I actually got -2 degrees overlap, not -3.5). And for ***** and giggles, I closed up the LSA to 112 hypothetically:

........115......112
IVO - 0.........0
IVC - 44........44
EVO - 54.......48
EVC - -2........4
OL.....-2........4

Under this scenario, you'd sacrifice revving, high RPM power, and street manners to gain idle chop and some midrange torque.

Now, a completely different thought experiment. Lets just look at the valve events and ignore everything else:

Your cam card......New
IVO........0............4
IVC........44..........44
EVO.......54...........54
EVC.......-2............-2
OL........-2............+2

Notice, we only changed one valve event - the IVO, which will give you more intake duration and more idle chop and actually help you rev higher without sacrificing any midrange torque. Might even help midrange torque. You's give up a little off idle, though.

Anyway, if you convert all this to cam "specs", you get this comparison:

Your cam - 224/232-115+3
Modified - 228/232-114+4

I'll say it again, we only changed one valve event, but this makes the cam spec look completely different. Using your method of just changing the LSA, you actually change 2 or even all four valve events. In reality, the cam I just made up for ***** and giggles is closer to the cam card you are looking at vs taking the existing cam and screwing with the LSA - even though the spec looks completely different.

In general, on a third gen motor, I like to keep IVC around 45 degrees and EVO around 55 degrees. Then, let your tolerance for the motor being a pain in the *** and your power goals determine the IVO, EVC, and overlap events. Now, of course that all goes out the window once you decide you want peak power at 7400 rpm, or some such thing, but with the cam you are looking at, I have to guess either its a moderate street engine or a truck engine you are looking at.

[/soapbox]

 

Was just asking before i posted the vehicle application. Darth ahs an awesome answer. This is for a 87 regal with a l92 headed lq9 with a 2800stall 4l60 3.42 gear with a 27.1 tall tire. Drive every where. Buy time cam is ordered will have a peak speedshop radical ported l92 intake. The place the cam was ordered from told me i needed to go with 228 on the intake but on a 109 icl and i would have to fly cut cuz i milled .015 off the heads and run a .040 head gasket for 11.2 calulated compression. I know a 2800 is tight, but so far ive run a best of 12.4 at 113 at 3800lbs since i was informed i was very tight on the valve clearance i was wondering how to make more n/a power before i spray it. I have -3.4 over lap cuz the actual card says 111.7 icl and 119.25 ecl

 

Nitrous adds another factor. Typically, you need more exhaust duration vs intake duration (split) due to nitrous. Even NA, those heads tend to like a lot of split. Here is a quick and dirty thought for you on this one:

228/238-114+3

IVO - 3 BTDC
IVC - 45 ABDC
EVO - 56 BBDC
EVC - 2 ATDC
OL - 5 degrees

You should have no PTV issues. You'll need to plan on some RPM to make power with L92 heads on a 6.0. That cam will run good NA and should not hold you back when you decide to spray.

 

Thanks again darth. That wahat i was thinking to that i need more rpm. This cam is layin down about 5700. I fig i need more overlap to gain some rpm. Lil slow on the duration i am. Thanks for your input. Was thinking about calling cammotion to grind this cam. Any special lobes?

 

Nah, I'd trust Kip on the lobes. If your springs can take .625, use that for intake lift and .610 for exhaust lift. Kip will be able to make the best fit from there.

 

The ICL & ECL split point denotes the amount of advance ground in the camshaft. On a 115 LSA the 111.7 means the +3.3 of advance. 115+3. Your ECL seems off as it should be 118. To the hundredth, I would guess, your advance is 3.25. Giving you ICL 111.75 & ECL of 118.25?

 

Formula to find overlap. 224+232=456/2= 228. 115x2=230. 228-230= -2 degrees overlap.

 

No buy the events, .4 43.7 55.2 -3.5 maks the icl 111.7 and the ecl 119.5

 

Alright man. No bad blood. Good luck on finding the right cam for your combo.

 

Very good thread to help understand camshafts better. It's a sticky in here.

https://ls1tech.com/forums/generatio...-t-matter.html

 

Slofla i wasnt tryin to be an ***. When u do the math on the events that is what i get.

 

I didn't take it like that. No worries. You're right. I guess don't see decimals too much with this. Your split is 115.6 making your overlap -3.2.

Nothing I wrote was negative.