If you have a big cam and you have the option of a 112LSA or a 114 LSA is it going to affect anything other than the thumpity lope or street manners? Is the power going to be the same?

 

112 peaks sooner
114 spreads out the power

 

When you say one peaks sooner and one spreads it out, do you mean for example the 112 may quit making power at 6,200rpm and the 114 may peak at 6,800?

 

you got it!

 

Yes, but the rate of "quitting" differs from cam to cam. Some taper off fast, others hold that peak for quiete some time (regardless of lsa).

In exagerrated terms, on a dyno graph, the 112's curve will look like a steep mountain while the 114's will be more of a hill. Imagine squeezing that hill in photoshop horizontally and you get the mountain.

 

Also, on larger duration cam designs, power is made further and further up the rev range. A lower LSA will keep peak power under 7K rpm for our use, otherwise, there's no use in having a cam peak at 7200rpm (altough it will make even greater power) if our stock bottom end can't go there.

 

The cam I have is a Comp XE-R 232/238 .595/.605 on a 114 LSA. I have a set of PATRIOT 64cc LS6 style heads that I had TESTED independently at a shop in N.C. and they flowed 305cfm @ .600 (and leveled off at 306.6 @ .650) and I forgot what on the exhaust. I'll get a flowsheet when I pick them up. FFHP (where I bought the heads/cam) said the car should make somewhere around 450RWHP with the better bolt-ons, according to the cars they have done with the same setup.

I'm just trying to figure where its going to be making that power and how running nitrous is going to affect the curve with that cam.

 

My guess would be somewhere in the 6500+ range.

 

What is the ICL on the cam???

 

Ah! Yes....

 

I'll look at the camcard and see.

These are the other HP mods the car has to accompany that H/C package

90 FAST intake
90 FAST TB
FAST fuel system ?Racetronix pump setup
85mm MAF
Edelbrock 1 3/4" stepped to 1 7/8" HVMC LT's & Y-pipe
Mufflex 4" catback w/ flowmaster
U.P.
160* Tstat
NX 85mm MAF system.
Comp pushrods
Comp R lifters (goes on with cam)
LS6 oil pump (goes on with cam)
Timing set (goes on with cam)



non HP mods

Textralia w/aluminum flywheel
4" carbon fiber PST driveshaft
Moser 12 bolt (4.10's)
Full Suspension
All 4 QA1's

 

112.0 Intake Center Line

 

With those lobes (XE-R) that puts your IVC at 48* (.050) and your IVO/EVC events more biased towards the intake. I would say the 6500rpm guess was dead-on... Also, assuming your are using a factory composite head gasket (.054 compressed) your DCR is 8.10. If you can get a Cometic .045 head gasket it will bump your DCR to 8.28, not much but big cams need all the help they can get down low.... Advancing the cam will raise the DCR (and low-end power) but you will loose some peak power… I am assuming you are about .007 out of the hole...

 

According to the cam card:
Intake 4 BTDC 48 ABDC @ .050
Exhaust 55 BBDC 3 ATDC @ .050


So if I do go from the standard to the cometic, will it possibly introduce and PTV issues? What would be the SCR if DCR would be 8.28?

Thanks,
Jeff

 

OOPS!!!

I used the wrong lobes on the info I gave your earlier. The XE-R lobes you are using are #3726 (intake) and #3729 (exhaust). I have re-run the numbers and below is what you have:

Assuming .007 out of the hole and .054 composite head gasket.

114lsa +2 (ICL 112), 64cc chambers
DCR:......7.96
Static:...10.67

114lsa +4 (ICL 110), 64cc chambers
DCR:......8.10
Static:...10.67


Assuming .007 out of the hole and .045 Cometic head gasket.

114lsa +2 (ICL 112), 64cc chambers
DCR:......8.13
Static:...10.91

114lsa +4 (ICL 110), 64cc chambers
DCR:......8.28
Static:...10.91

On the clearance issue with a cam of this size the only way to be absolutely sure is to measure (clay, mock-up, what ever)...

Sorry for the confusion....

 

You dont have to appologize to me, you obviously know more about that, than I do. I just appreciate all the information and the time you took to type it all.

Thanks,
Jeff

 

Ask you cam manufacturer to grind your cam on a 117 degree LSA.

 

Why?

 

That would put his DCR at approximately 7.35 ( ) and the IVC at 50* (.050), resulting in no power in the low rpms and the peak power so high in the rpm range you would not want to spin it that high...

 

Me Too... Why???