what do you think is the way to go on a 402/408/414/418 cubed motor? I understand this is just speculation...... I am just curious as to what yall think would be considered the norm for this application.

L92 heads
L76 Intake
Kooks Longtubes
SD Tune
Non-Daily driver with weekend trips to the drag strip.
Non-valve spring killer
6500 rpm rev limiter

 

why don't you do what any rational person would do and call a professional and have them figure it out for you? you're not a cam designer, let one do it for you.

 

that is what I am doing..... the fella building my engine is also designing my cam..... I am just waiting until January/Feb to get the ball rolling... in the meantime without a set of heads in the hands of the right fella...... just curious what "others" think.

so......

 

billy is building the engine and specing the cam?

 

The cam choices don't make much sense to me. Why are the LSA's ever increasing on the larger duration cams? I guess to make them idle better? All it does is push the peak power the motor is trying to make higher and higher and it will fight against what the intake manifold is trying to do unless you go single plane, sheet metal or individual runner which you won't be doing any of on this application. I vote to keep the LSA down and the duration as well but a slightly larger split than what is normally seen on LS1/LS6 style heads.

 

if you read more neither will much of anything else this guy posts...

 

the point of my post was to start a discussion. thats it.

 

go with one of the 2 first choices if you want it to be tamer. hell it might just make more than youre expecting too with it being "mild."

 

What do you think of the cheatr cam? Very close to stock LS7 advertised specs.
Dont forget the size of the valve will act as though you have a lot more duration. Valve size is almost 10% larger. So maybe a 220 will act as a 240!
I think lift will be your friend and of course the all important overlap..
Then crutch that Exhast to compensate.

 

so what you're saying is that im irrational for going out and doing it myself?









stop looking at the LSA and start looking at the valve timing..

 

im actually using an ls7 cam so well see how it does. even with just 1.7's its gonna be ~.550 lift. im not expecting anything astronomical but somewhere close to what partick made with a smaller motor and more expensive heads.

 

I did much this same thing but I didn't do an either or thing. I read, listened and then approached several people who had proven themselves "pretty smart" about cams. They made the suggestions and explained why they suggested whatever cam. I got general cam specs from some very knowledgable people. I listened some more and made a leap of faith and had BRE design a cam for my build. BRE took into account the entirety of the head's flow - not just peak numbers and built lobes that would support that. It's not as simple as XE-R, LSK, XE and duration that going to make it work. They then spec'd the SCR to achieve the DCR compatible to the cam. Again, this cam is only for "my" car the way "I" want to use it.

Sometimes you have to listen carefully and trust your gut. I think it worked well for me. But to be honest, it could have bombed big time but I was willing to take one for the team going into unknown territory.

My $.02

 

theres "good enough" for some people. others just have a different approach to get whats right. hell, im sure i run the risk of my setup completely bombing for not tailoring the cam to the heads/compression, but im sure the cam i chose will do fine for what i have at the moment.. i can always get a custom one later when i have the rest of the setup i have planned and the cash too.

 

Moving that LSA around greatly affects the valve events...

 

.............................. 0.006 0.050 0.200
......Intake Duration - ID 288 236 163
....Exhaust Duration - ED 306 254 177
Lobe Center Angle - LSA 110 110 110
..Intake Centerline - ICL 110 110 110


...Intake Valve opens - IVO 34 8 -28.5 BTDC(- indicates ATDC)
...Intake Valve closes - IVC 74 48 11.5 ABDC
Exhaust Valve Opens - EVO 83 57 18.5 BBDC
Exhaust Valve Closes - EVC 43 17 -21.5 ATDC(- indicates BTDC)
...Exhaust Centerline - ECL 110 110 110
................... Overlap----- 77 25 -50 degrees


12:1 static compression will give approx 8.86:1 dynamic


just a best guess, but i am no cam designer

 

Bigger.

 

Something along the line of 224/240-116+0, .590/.570" lift w/ 1 7/8" headers.

Brian
HiTech Motorsport

 

How can you make any kind of power with a lobe seperation like that? I'd bring that down (make more overlap) and crank that lift up with some LSK lobes but that's just me.

 

How does a 500" ProStock motor make power with a 120-122 deg lobe sep? As the head becomes more efficient, less overlap is required to make power. Too much only draws intake air right out the exhaust during overlap.

Brian
HiTech Motorsport

 

Could even be as high as 118LSA.... the Pro Stock guys do it for a number of reasons, one being that the RPM is so high in those motors that helps put the valve events in a decent place and the ICL is put where it needs to be based on where it needs it for intake inertia.

The overlap is also a good point, but on a Pro Stocker the overlap has a lot to do with durations of 275-285°@ .050" on the intake and 305° @ .050" on the exhaust..... Thats why they use a 118-122°LSA. A street car with a well tuned exhaust system is another deal all together and reguardless of how good the heads are or valves flow centerlines and overlap still have their place, just have to watch out WHERE that is with these cams.

Bret