I am currently in the process of building the motor for my 87 z. I am wondering if any of you dynosim wizards can help me out. I am trying to look into the difference of power two different cams make. My specs are:

383 ci
3.750" stroke
4.030" bore
6" rods
10.9:1 comp
Edelbrock victor Jr heads (i have the flow chart for them if you need)
2.08 intake valves, 1.65 exhaust
Eelbrock victor Jr intake
Barry Grant 750cfm race demon with mechanical secondaries

The two cams I am looking at are:

comp cams custom grind solid roller: 254* intake @0.050 106* LSA
260* exhaust @0.050
0.661" lift intake
0.651" lift exhaust

comp cams xr292r: 254* intake 110*LSA
260* exhaust
0.582" lift intake
0.588" lift exhaust

I am looking to see the difference in power curves between the two cams and to see what kind of power I should make. Thanks in advance for all your help!!

 

Anybody????? Does anyone have any other cam recomendations? It will have a 4.10 gear with 27" tires and a 3500 stall. i'm building it mostly for the track with the occasional drive on he street.

 

what are the actual valve timing specs on the custom... as the could be anything hence "custom"

 

I listed all the specs for it. Intake duration is 254* at 0.050 with 0.661" lift, the exhaust is 260* at 0.050 with 0.651" lift with a 106* LSA

 

those arent the important specs... those are the fast specs to distingues cams i am talking about actual valve timing IE IVO/IVC EVO/EVC...

it looks like their custom cam would be better... but that means nothing...as it will be impossible to tell if you can even run their cam without major Problems... if you dont know the IVC

 

Unfortunatly I don't know the cam timing, I thought you were just talking aboult the specs earlier. I havn't got a timing card with it as I havn't ordered it. I'm just trying to decide wether it will be worth the extra money getting the custom cam ground, or wether I should just stick with the off the shelf cam. Any power estimates. I am hoping for 500+
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And what major problems are you talking about? I will be degreeing in the cam when the motor is assembled, if that's what your talking about.

 

sorry but i dont think you are anywhere near 500 hp... low 400 is a maybe...

what i was talking about was in relation to your compresssion ratio... with a high static compression and a big cam... it is okay do to the usually late closing of the intake valve on the compression stroke... this is why i asked for valve timing as you can use the valve timing to come up with your Dynamic compression or effective compression... that is what is important not so much your static compression... as the late IVC will allow some of the air in the cylinder to escape before it closes and actually makes compression


i was saying it was dangerous do to the fact that it can cause horrible detonation problems...

i thought comp charged the same price for a custom cam as they do for an off the shelfer

 

Either cam will be "OK", even if the rest of the car isn't set up very well.

The "custom" one will be "peakier"; you'll get a higher torque and HP curve, but over a narrower RPM range than the other. The XR292 will have lower peak outputs but over a somewhat broader range, that will extend to a slightly higher RPM. Maybe 5% peak, 3-500 RPM difference.

The choice will depend on how heavy the car is and what trans is in it.

With a 700, the XR will probably be better.

3500 converter stall is WAY WAY WAY low for optimum racing results. I'd be looking at 4500-4800 on up.

If this is a steel-bodied car (3200 lbs) my choice would be the first cam; 999 springs set up at 1.900"; steel roller rockers & stud girdle, or shaft-mount rockers; converter 5500-5800; shift at 7200; T350 or Glide. NOT a 700. If it's lighter you could maybe get away with a little less converter. I'd be expecting something in the mid 500s of HP; 545-565 or so, peak at 6600-6800. Peak torque around 450-475 ft-lbs at 5800-6000.

Yes you'll need to concenrate a bit on getting some traction.

The "extra money" is peanuts. Hell, not even that. Your first night at the track, something will break, and it will cost several times as much. Just get what's best and don't worry about the $25.

 

Ya, I do agree with you that the stall is too low for an all out race car. The problem is that I do want to take it out on the street from time to time. I live about 30 miles outside of the city meaning it would have to do the occasional highway jont as well. Would I not have problems with the tranny overheating on the highway with a 4500 to 5000 stall? I am planning on spinning the motor pretty high and the car weighs in at 3250 LBS (with the iron headed motor I originaly had in it). From your great explaination I think I will go with the XR292. I will be running a th350 trans and moser 12 bolt. I am hoping to hit low 11's on the motor and possibly spraying for 10's. I've already built the chassis with a 10 point cage, subframe connectors, full spohn suspension, coil-overs, tubular a-arms and k-member and so on.... I think once I get the suspension dialed in traction shouldn't be the issue. What do you think about running that high of a stall on the street? I phoned Art Carr and there the one's that recommended a 3500 stall. ANd I'm not worried about money, I know how racing goes!! What would you think of the first cam but ground on a 110 LSA? Maybe widen the torque a bit over the 106.

 

That thing would be no fun at all to drive on the street.

 

No it won't be, I will agree with you there. But the street isn't what it's being built for. I just want to be able to drive it to the odd show n shine and down the blvd on cruise night.

 

I just dont see how your will get 500 HP out of that... not saying your wrong sofa maybe you have some personal experience

but i plugged this stuff into DD just for an abouts

 

For one, an XR292 isn't a hydraulic roller.

 

I will be honest, I've built many street motors but nothing this radical. Those power numbers seem low to me. But I am just going on power numbers I have seen from known combinations (i.e. magazine builds). I know super chevy built a 355 with the same heads and intake but with a little smaller cam (248 intake, 254 exhaust) and made 512 hp at 6300rpm (it was one of there danger mouse builds).

 

Yes, they're way low because DD assumes that a hydraulic cam starts to die off quickly above 6000 RPM. If he modelled it correctly as a solid roller it would be more accurate.

But looking at the low RPM numbers, you can see what will happen with a 3500 converter. You'll have something that an LO3 can spank off the line.

 

actually i set it up with the solid roller but changed it hydrualic to see if it would change the lifter accel rate which it didnt...

 

here it is with the solid roller... which i had originaly used

 

It's not the lifter acceleration rate that's the problem. What were the numbers like as a solid roller?
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You're using lash-to-lash timing events as .050.

 

yeah you were right ape

here it is with the correct seat-seat timing form comp well .015

still not close to 500hp though

 

Something just doesn't seem right with those charts?! With a 215cc head, big cam and single plane intake it should be makeing peak power way higher than 5500rpm. Unless I'm reading those wrong. Aboult the 3500 stall, going with those charts wouldn't a 3500 stall work best? It would put me right at the start of the torque curve where it is best to launch. Torque gets you out of the hole, and horsepower carries you down the track, does it not? With the higher stall it will almost put me right at the end of the torque curve would it not? I am new to building a car from ground up, so please enlighten me if I'm wrong!!

 

well give me your flow#'s so i can compare and re do the sim

 

Flow #'s are:
intake/exhaust
0.100 67/64
0.200 123/111
0.300 173/145
0.400 219/180
0.500 255/198
0.600 275/206
0.700 284/210

 

okay i have changed the flow # those are much higher than some of the other # i have for those heads... have you had anywork done to them when did you get them?

 

I got the heads about 3 weeks ago from Summit. i got the flow numbers off of AFR's website actually as they were doing a comparison to say how much better there heads are that they claim they did there own flow bench testing on. So I am going to assume that they wouldn't give inflated flow #'s about a competitors head!!

 

i wouldnt think so either... those might be a little low if anything but deff 500hp...

DD2003 has a few bugs and isnt the end all... it is sorta just a "semi" educated guess

 

A semi-educated guess is better than a non-educated guess!! Can I bug you for one more thing. Can You try running it with a smaller cam? Like the 242 intake, 248 exhaust (I can't remember the grind # off the top of my head). Thank you for all your help!!!! :hail:

 

okay here it is with a 242 .050 / 250 .050 solid i dont have any specs for a solid roller that small it is also a .470 lift rule cam so i will make any adjustments you want

 

Ok here are the cam specs for the one I was telling you of:
grind # Xr280r solid roller
242* intake 248* exhaust with 0.570" lift intake and 0.576" exhaust with 1.5 rockers and a 110 LSA. Can you also test the custom grind cam I listed in the initial post or do you need the cam timing specs? And also try with 1.6 rockers for the tests? Wow, I almost sound like my wife with asking can you do this all the time!

 

okay here it is with the XR280R with 1.5s and 1.6s

 

And One last thing, can you test the smaller cam with a performer rpm air gap and an hsr. I want to see what the power difference between the single pland and dual plane to the tunnel style injection. And that is the last thing I will bug you for!!! I thank you for all of this! I'm glad I joined this site, what an amazing amount of info!!

 

okay air gap/ tunnel ram

 

Wow, thank you very very much! I think I am going to run the 280 cam with the hsr or possibly the performer rpm if I can't figure out what to do with the carb sitting in the it's box! But I think the air gap chart looks like a strong engine that with the right chassis tuning could get me in the high to mid 11's which would be perfect and still have the driveability on the street!! And the bottom end is all forged with h-beam rods as i was planning on more rpm (short block is already machined, balanced, and assembled), so maybe I'll even spray it down the road and deffinitly hit the low 11's! That would make that 3500 stall work perfect, and also I may even be able to get away with a 3:73 gear with that much torque!! Thank for doing all this, you have really opened my eyes!!