guesses of the HP of this combo

chevy 454, 60-over
8.6:1 CR
Edelbrock performer intake
HEI
Jet-recalibrated 800 CFM Qjet
2" x 31" headers, 3.5" collectors (a little big, I know... long story)
2.5" dual exhaust w/ H pipe
Flowmaster series 70 mufflers
Comp cams XE262H, 218/224 @ 50, .504/.510 lift, 110 LSA
Stock 049 heads, 250/177 cfm flow.

Any guesses? I think it should be a little more than desktop dyno suggests. I'm pretty good with the dyno software and usually its pretty close, but it seems low this time.

Curtis, I think the biggest thing holding you back is your compression ratio. That could easily be a 450HP setup with 10:1 compression. As stands, I'd guess 345ish hp, with may be 390ish ftlbs, how close?

I agree that the compression is not so great, but this is a cross-country cruiser, so cheap gas is a must. I could have milled the heads for about 8.9 and just been careful with timing, but it wasn't worth the extra few horses.

Your guess was actually lower than desktop dyno. I plugged in 10:1 and it gave me about 30 more horses over the 8.6, but I'd rather get that power elsewhere.

Here is dyno2000's simulation.

http://www.curtisandkim.com/454dyno1.jpg

Its about 365 hp and 482 tq. I was hoping (with the nice fllow of the heads) that I could get 400-420.

That is the thing that bothers me... 250 cfms of flow is enough to support 450, but when I plug in higher flow numbers, it gives me big boosts in power. When I add cam it does very little. I'm trying to figure out the weak point of this combo, (other than compression) but I think maybe dyno2000 is not so good with its canted head profiles. I plugged in flow numbers at lift to give it an accurate profile, but it still likes to reward excessive flow. :screwy:

Curtis, Do you have a graph of the airflow for the heads? Or can you post the lift/flow numbers? I agree with Random that the compression is too low. Does Dyno2000 give feedback regarding airflow requirements or only analyze the data you enter?

Curtis, Do you have a graph of the airflow for the heads? Or can you post the lift/flow numbers? I agree with Random that the compression is too low. Does Dyno2000 give feedback regarding airflow requirements or only analyze the data you enter?

It just analyzes the data you enter. If you go too far off the beaten path like using a 325* cam with 7:1 compression, it can't even come up with numbers, so a window pops up and says, "try more compression or less cam duration for this simulation." The airflow requirements and the HP they can support are pretty easy to calculate, but I use this website for that...

http://users.erols.com/srweiss/tablehdc.htm

Dyno2000 uses known physics of air's inertia, etc to calculate how much filling and evacuating can actually occur in each 720 degrees. From there it can create VE tables. From there it uses displacement, bore, stroke, etc to create a torque curve. If you know how to use it (i.e. if you read the owner's manual) it is incredibly accurate. Now that I'm familiar with it (had it since 98) I'm usually within 5% of actual dyno numbers, and I think that is pretty good considering how many variables there are on the real engine. The simulation assumes several things; a proper air/fuel mix, a proper timing curve, no detonation, etc, and those are things that the end user must make reality on the engine.

The software comes with several head choices, but not like "chevy casting 335". It comes with your choice of wedge, flathead, canted, 4-valve race, etc. Then under each of those you have choices of stock, pocket ported, or fully ported, and valves in stock or oversize, etc. They are good for a quick guess or estimate. The real way to do it is find the flow numbers (which i found on the net) and plug them in at lift numbers and then the simulation has can plot its own flow curve and use the cam numbers to plot that curve relative to the valve events, and piston speed. The cam choices are very similar. You can use some pre-canned generic choices, or use the "cam math" feature and input every detail about the cam events.

Although I agree with the compression being too low, the trade off is not worth it. Even if I launched it to 12:1, I would only be picking up 38 hp. The cheap gas is the way to go for me. I never subscribed to the "more compression is better" thing and so far I've had pretty good luck with sub-9 compression on everything I've had. It does cause throttle response and cam limitations, but I have huge heavy cars and don't usually use the big cams.

Flow numbers on the heads go like this. These values are in CFM @ 28" water, based on 2.06" and 1.72" valves. They go in .1" increments from .1" to .7", so there are 7 values.

Intake flow, starting at 0.100"
59, 124, 188, 232, 250, 264, 264

Exhaust flow, starting at 0.100"
52, 98, 128, 152, 177, 187, 192

Of course, my lift at the valve is just slightly over .500". I used all of these values though to create the flow file in case I ever need to know what the effects of greater lift might do on this engine or another.

I guess my real question here is this: If 250 CFMs is enough to support 450 hp, then how would one build a 450 hp motor using these heads? It seems that no matter what I do; cam, compression, intake design; nothing gets above 420 or so. But as soon as I simulate more flow, I'm rewarded with huge power gains.

I was close on my hp, but torque was way off, I knew you were gonna be higher on torque, but damn.... 480 ftlbs at 2k rpm? Thats diesel territory right there :)....

I have to agree with your arguement on the compression ratio. My old monte carlo could never run on anything but premium.

As far as air flow, I wish I could tell you more. This is definetely something Im unfamiliar with but would like to learn more about. Although it really only helps at higher flow (higher RPM's) the only thing I could tell you is to port match the intake to the head. One of my good friends parents is absolutely crazy for all that information and I'm sure he could help you out. He worked with a lot of top fuel teams for their head and cam designs. Would you want me to try to put you in contact with him?

Curtis, My program gave me the following numbers: Tq: 476 @ 3580, Hp: 399 @4727. I had to estimate a couple points, but it's pretty close. To achieve that, 235 cfm is required by 79 degrees ATDC. Why 235? Well, as a rule of thumb, engines need peak flow in the 72 to 84 degree range. Your engine is at 79 degrees. Flat tappet cams hit about 95% of peak lift by that point. Thus, we can estimate that you'll achieve around 235 cfm, based on the 250 @ .500 lift. It's not perfect without flow testing, but close enough for jazz. I suspect that your program is calculating that in and therefore dropping the flow and horsepower. Try leaving the specs the same, but telling it you have a roller cam. BBC engines LOVE roller cams! By switching to a roller, I got 478 and 440 (t & h). That was with 95% VE, which may be why the h.p. numbers started higher than your program...95 is a bit optimistic. Your headers by the way are just fine. They are sized for max power, but that's what you seem to be after. You won't notice a few pounds less torque anyway.

Excellent info. Here is an excellent example of why I'm confused. Look at this simulation that I created months ago when I started this project. It uses a smaller cam with roller lifters, but LOOK AT THE CURVES!!! Compare the first chart I posted with this one. This chart with smaller headers, less compression, smaller carb, and slightly larger valves; and smaller displacement makes over 500 hp, the the original chart makes just over 350. what's going on????

http://www.curtisandkim.com/dyno454.jpg

Curtis, Is everything the same? I see a different name for cylinder heads and a different airflow file name. Beyond those, I'm not sure how your program handles the differences. The roller lifters make a huge difference in area under the curve, and even a '252' cam will have more area than a flat-tappet '262'. Did you run the '262' as a roller? The valve size shouldn't make a big difference, as you have input the flow figures manually, and those figures represent the flow regardless of valve size. Your program may estimate flow velocity with the valve size, but that's not always the smallest port cross-sectional area. Compression and CID didn't change significantly. Most likely, it's primarily the cam change and the way the program handles some of your variables, assuming the airflow is apples-to-apples. Try the roller 262...curious.

When I switched this combo to roller, the curves shifted down considerably. It acted like I dropped back to a stock cam; torque peak at 1800, hp dropped to a lower peak at 4000. ???

For now I'm going to assume that the dyno software is not operating properly. There are just too many inconsistencies.

The reason the file names are different for the two simulations is because I had to reformat my hard drive in between those two simulations. When I re-entered the data for the 049 heads I just called it something else. I did double check the flow numbers and they are the same.

In answer to another question you had... When you enter flow numbers in dyno2000, you base them on a valve diameter. That way you can estimate how the combo would change if you added larger valves. Otherwise you would have to estimate all new flow curves on your own.

Basically, I think I'm going to use my experience combined with what you two have given me and guess that this engine should be a 380-400 hp engine.

I wonder why dyno2000 is crapping out on me???

Thanks guys.