Verbs,
Now you know why Denzss and I said you were way over cammed. Glad this thread has been helpful.

Chris

 

http://www.wfu.edu/%7Erollins/piston/

 

Agreed it would take a great head like Absolute 2.75 to pull that off with the 230ish sized cam. For heads that flow less it would take more cam to spin as high.

Really all depends (for the calculation) on what the heads will flow with the intake in place.

 

Hmm what are your heads flow with the intake in place? If they are TEA 2.5 w/intake I think there was a post show 270 to 275 with an unported LS6 intake. That would seem like 230 sized cam but I'll do the math and see what I get.

218 is too small unless your flowing like 330 thru the intake which isn't likely.

verbs set up

346/2*7200 divided by 1728 = 720.83 cfm needed

720.83/8 = ~90.1 cfm per cylinder

Guessing Verbs heads will flow 275 thru the intake

90.1/x = 275

x=.3276

720*.3276 = ~235.8

Calculates out to around 236 intake duration cam. Based on the E to I ratio being around ~70 to 75 percent (guess) for the heads in question I'd go single pattern or with ~2 degree split. 236 seems like a reasonable starting point. If the heads flow less than I guess with intake you'll need more cam if your spinning to 7200 rpm based on the ghetto math.

236/236 or 236/238 would where I'd start my guessing for Verbs application.

Of course if Verbs was using one of WAR's GMPP LS1 intakes it might flow (after porting & port matching) way more air than the LS6/LSX does. I think that the applicaiton were we will find some real ability to use our heads to their full potential with smaller cams than we currently do. Of course the valve job will have to be tailored to work with the WAR LS1 intake.

 

Here are my flow numbers from Jay on the heads we are running, with no intake, and LS6, and an LSX...


AS AS AS
LS6 LS6 LS6
225CC 225CC 225CC
No intake LS6 LSX
Intake
Lift
.050 - - -
.100 69 - -
.150 - -
.200 155 152 154
.250 - - -
.300 212 204 208
.350 - - -
.400 259 243 251
.450 280 260 269
.500 301 272 280
.525 - - -
.550 313 281 290
.575 - - -
.600 323 293 299
.625
.650
.700

Exhaust
Lift
.050 - - -
.100 - - -
.150 - - -
.200 117 117 117
.250 - - -
.300 160 160 160
.350 - - -
.400 206 206 206
.450 213 213 213
.500 222 222 222
.525 - - -
.550 228 228 228
.575 - - -
.600 231 231 231
.625 - - -
.650 - - -
.700 - - -

 

J-rod,
Let me know the rest of the particulars and I will work on a stick.

Chris

 

212, 259, 323 What size bore and valve??
You only dropped 24 cfm with the LS6 @600.- what would average (run of the mill ported LS6 heads) be with an LS6 - 50 cfm? Thank you.

joel

 

2.05-2.08 Valve (I forgot the exact size, I need to go back and look). Bore is stock 3.9.

As for flow drop, etc... Depends on the heads, etc... Thats why Jay does so well is that he checks this, many folks don't so you get a port that works open, but may not work with the intake in place.

 

I used a few different numbers than you; I figured with a port matched LSX intake my heads would flow about 290cfm through the intake, and I would spin to 7000rpms.....

346/2*7000 divided by 1728 = 700.81 cfm needed

700.81/8 = ~87.6 cfm per cylinder

290 thru the intake

87.6/x = 290

x=.30207

720*.30207 = ~217.5 or about a 218


OR

346/2*7200/1728=720.83CFM

720.83/8=90.104 cfm per cylinder

again, 290 thru the intake,

90.104/x=290

x=.3107

720*.3107=223.7 or roughly a 224 cam.


Interesting how spinning my car an extra 200rpms creates a jump from a 218 to a 224 cam. . Seems like a big jump to me.


To say I was overcammed was really just a guess since no one knows what my heads flow through the intake.....I'll know this in the next day or two.

 

290 thru the intake is very serious airflow...I agree if you get that type of flow it calculates out to a much smaller cam than I listed.

I also agree it's pretty amazing how much more cam is needed for an extra 200 rpm based on the ghetto formulas.

Looking forward to seeing the flow data with the LSX intake.

 

J-rod, you have some specs in your e-mail.

Chris

 

Verbs,
Your 200 rpm. I refer this to the "Threshold". Any engine has a point at which the induction goes from a positive, easily fill the CID, to a Negative, start to strain to fill the CID. When you hit this "threshold" number the camshaft numbers jump dramaticlly because now the cam is working beyond the capabilities of the induction system. This is common in NHRA stock, limited circle track, restrictor plate engines, etc. To keep the effiecency up, the cam has to grow.

Case in point, when Nascar first inacted the "plate racing", camshafts grew and springs broke. The air flowing through a plate was only around 600 cfm, not even close to feed 358cid at 7500 rpm. So engine builders through duration at it to keep the intake valve open and "suck" up as much air as they could get. Takes about 750 to 780, ( these are figures) to keep that 358 CID at 100% VE. Well 1 engine builder thought different. He new he could make 110% VE, turn more rpm, and all with a small cam that would give good responsiveness out of the pits. So Ernie Elliot built a 308 CID engine. The restrictor plates allowed enough air for this engine to make big power. . .needless to say, Bill Elliot kicked butt and Nascar now has a minumum rule of 350 CID and a max of 358 CID.

Again matching the air with camshaft. . . critcal.

Chris

 

Chris, not to flame anyone but I've actually seen almost the total opposite with all the NASCAR people I know? I know I always see smaller cams for the plate engines and some seriously big ones for open engines.

 

Thats about the craziest damn thing I've ever heard. Who the hell would ever think building a smaller engine to run on restrictors is a "GOOD" thing? I've seen that tried before and the results were about what you'd expect. Less torque, Less overall power, peak power at a higher rpm, and a slower car. The restrictors are limiting the amount of air you can take in, period, so building a higher reving less efficient engine is only going to hurt you. You should really quit spreading ridiculous rumors like that because any real engine builder will only laugh at you.

 

Well Danno is laying down some crazy smack so I'm staying out of that! I know the engine tests he's talking about where this mythical feat was tested in depth by several other teams and only less power and slower lap times resulted. I think it is fairly common knowledge that some cheaters during the first days of restrictor racing were claiming the smaller engine thing to account for their extra RPM that was really the result of some "air leaks" that were occurring in the engine. NASCAR canned it all with the 350-358 rule basically so no one could claim that they were turning RPM with a smaller engine when in reality they had more air available. If you're turning crazy rpm now with a plate they know you're cheating!

But seriously I think Chris worked at Katech and I know a few guys there too and I know that Fritz himself said that you usually always go smaller on the cams for the restricted stuff. I know the restrictor cams I have seen at two BIG NASACR teams that have both won the WC championship lately have both run much smaller cams in their plate engines. They also have some fairly large in duration cams for the open cup engines, bigger than I would have thought at least.

 

Sorry about the earlier post, I get a little carried away when people start talking about that smaller engine for restrictor plate racing thing. It just doesn't work for alot of reasons. I mean really whats the difference? any engine is restricted slightly so why would a restrictor engine make more power if it was smaller with the same restrictors? Why not just always build really small engines with big carbs and turn crazy rpms? Some people do that but its called comp eliminator and they get crazy weight breaks and their engines are super expensive with short lifespans.

 

Well I invite anyone to call HVH and ask Joe Petelle, since he was doing the heads back then in the 80's. As for restriction on induction, I have a good grasp of it with all of the 2 barrel engines that I cam. MANY of my customers have gone to smaller CID's 331 or so for these classes and do quite well.

I never worked for Katech, but I have been involved in this stuff since the mid 80's. Who I work for now, Stef's, we make most of the oil pans for the professional race teams and do R&D work for the OEMs. Needless to say, I am confident in what I bring to the table.

Chris

 

Chris,

Like I said not a flame but I am talking right now not back in the 80s when HVH actually did NASCAR heads and people knew a lot less about making restricted power. They've learned a lot since they started running the restrictor plate stuff and they have developed it pretty well. I am talking soley about guys that are putting these engines on and off dynos in NC right now. Over 5 years ago which can't get me in trouble they ran 30 degrees less on some teams and I don't think I have ever seen much more than 15 degrees less so far on a plate as opposed to an open motor but you never know. It's interesting but nothing you can do much will make more air come through the plate nowadays with the rules so they cam the engine for the operating range that the plate dictates for the most part. A big cam just caves in the mid range and reduces compression too much.

 

Nothing could be finer than to be in Carolina...

...and have friends at shops like WAR ie Wegner Automotive Research here in good ole Nawf Carolina that actually do engines for several NASCAR teams in Cup, Busch & Truck

 

Well Erik, I was talking about in the 80's and the intro of "plates". Said nothing about what has transpired since.

Chris