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Discussion Starter #1
I dd a combo i'm thinking of running, but I don't think the numbers are right.
Can someone verify?

Bore X Stroke: 4.00X3.25 (327)
Valves: Intake 2.02 Exhaust 1.60
compression ratio 10:5.1
single plane manifold (victor jr.)
Large tube headers with exhaust
Cam specs
intake lift (at valves): (i think that is what you should select for desk top dyno???)
lift:
intake: .550
exh: .600
lobe center: 108.0
over lap: 62.0
int duration: 278.0
exh duration: 278.0

I used AFR's Flow numbers for their 195cc street heads, 100% cnc'd intake/exhaust and combustion chambers.

On desk top dyno 2000 that comes out too 495 hp @ 6,000 rpm and 469 ftlbs @ 5,000 rpm

I do not think this is correct, I think the hp/tq numbers are WAY over rated.
I could probably get away with more duration on the exh side but I used the stock cam profile for duration...
 

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Sounds a little hi.
hmmm... I have a desktop dyno and the most its been off is about 7%.

327 with 495. better change those numbers to @ 50 lift.
 

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Changed it to "0.050 timing" I still think it's a little high, actually atleast 25hp off....
466hp & 408ftlbs both at 6K
I mean I hope it's right but dang, that just doesn't seem right...
 

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aj,
I have Dyno2000 and it has always seemed a bit on the "enthusiastic" side to me. The other thing is, I personally think that most of the head manufacturers might be inflating thier flow numbers a bit too. Most of the dyno software programs are good tools for playing with different cams and seeing how they affect torque and hp curves, but I would never put a lot of trust into the actual figures.
 

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Discussion Starter #5
aj,
I have Dyno2000 and it has always seemed a bit on the "enthusiastic" side to me. The other thing is, I personally think that most of the head manufacturers might be inflating thier flow numbers a bit too. Most of the dyno software programs are good tools for playing with different cams and seeing how they affect torque and hp curves, but I would never put a lot of trust into the actual figures.
I think your right
I noticed when reading the fine print of afr's flow numbers they use generous lengths of header tube and manipulate the flow numbers beyond what we are capable of doing in our cars... lol.
 

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I have tried on numerous occasions to contact them to figure out issues that I have w the program. I have never gotten a response back. Worthless program.
 

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I like it but I use my won flow numbers from the machine shop. Just call and ask if they have some aftermarket heads thevy flowed lately, or ones close to the ones your considering.
 

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I've wondered about the large tube headers? What is a large tube header? Is a large tube header on a 502 larger than a large tuber header on a 283? How do you know?
A 327 with a .6" lift 278° cam isn't going to be peaking at 6000 rpm.
 

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Mine showed it making 550 HP at 7k, 475'# at 5k.

Heads is what it bases most of it on it seems. A change to stock heads made it puny. Playing w/ exhaust made slight changes.

A funny thing I just noticed, haven't tried it but a few times so maybe I'm screwing up.... the damthing makes NO difference whether you select hyd/hyd roller/solid/sr cam if you make your lifter selections from the main page without going in and inputting 50 numbers. And that is wrong, it should throw up a flag. There can be over 40° difference for at 50 #'s in the 4 cams with the same advert numbers. Strange thing for a cam company to overlook, but it's still early and I'm probly goofing it up somehow:). Surely comp wouldn't do that.

I always wondered that too on exhaust size. 1 7/8 is huge on a small block but tiny on a bbc. I think they have a fixed "adder" percent or flat rate for each of their exhaust categories above a baseline.
 

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With my latest Comp DynoSim,, I can see differance in numbers when changing lifter types or acceleration profiles, head flow, carb size , just about anything. I do agree numbers are somewhat inflated.
 

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Mine will change from acceleration rates, but not from lifter type selection... from the main page without going into CamManager
 

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I have currently used the Desktop dyno on two small blocks that have also been on an engine Dyno and I've been within 5% Just my luck,Working on Number 3.
 

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5% all the way through the range?
 
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