Using Desktop Dyno as a comparison tool for 351Cs?

[nosaj122081]

I've been planning my Cleveland build as of late, and have been using the Engine Analyzer 3.0 as my means of comparing different buildups.... I'm concerned about its accuracy though (either that or the accuracy of "popular opinions") as some, if not ALL, its results are surprising me. I know its power numbers are optimistic, but I'm curious to anyones opinion on the programs accuracy when it comes to different components on essentially the same motors, most notably heads.

EA seems to pretty much HATES 4V-port heads... I'm either going with a 393 or a 357, and in both cases with my particular engine EA didn't like the 4Vs AT ALL, ported 2Vs made better average and peak torque and horsepower numbers; open chamber 2Vs on the 393 for 10.5ish:1 and Aussies on the 357 for 11:1. I manually put in head specs that I got off various head flow and figure charts, so they are as accurate as I can get. With either a Crane F246 or a Comp 284B (almost identical cams), the motors I set up made power from most to least in this order: 393 2V, 393 4V, 357 Aussie, and then 357 4V.

Anyone have any input on the EA's accuracy when it comes to head comparisons? It definitely surprsised me and went againist alot of popularly held beliefs. Anyone else use this program with surprising results or notice that it doesn't like 4V heads? Or is it telling me the truth?

 

[Hack]

I don't know anything about the program, but when you put 4V heads, are you putting the complete package to run at screaming high rpm? From what I understand, the 4V heads want to run waaay up there, like over 8k? And are you using 4V closed chamber heads? I don't know much, but I've read a fair share of threads where people call 7,000 rpm much too low an rpm, for instance. I've read advice saying just go with 2V heads if you don't want to run the motor over 7k.

I would be surprised if you want to use the same cam with a 4V as a 2V. Your cam probably isn't nearly wild enough for a stout 4V.

Those are my w.a. guesses. This is why some people say that the 2V heads are better for a street machine. They make a lot more power in the 1-6,000 rpm range. That's what I've read anyway.

 

[nosaj122081]

On the 393, the 4V heads I'd be using would be open chambers, theres no off-the-shelf piston that makes reasonable compression with closed chambers and has a quench pad on it. Really the only way I'll be using closed chamber heads is in the form of Aussies in a stock stroke application. I don't want to spin the motor high enough to make the 4V's useable on a 357 (7k is as high as I'll go), but I figured the 393 would bump the RPM range down a decent amount, but even that liked the small port heads better and made a much nicer looking curve.

The cams are both 246/256 duration at .050 lift, from what I've gathered pretty much one of the most popular C cams duration-wise regardless of heads. Any larger cam with either the 4V or 2V heads make higher peak power numbers but drag the average numbers down.

 

[SadbutTrue]

i would experiment with hack's suggestion... ie make a 357C with a really, really wild cam and the 4v heads and see if thats where the 4v head's power band really is. But yeah, the 4v flows a ton, but heads fromthe 60s and 70s weren't as versatile as todays.... either they'd flow a ton and be kinda weak down low or they'd be torquey and have decent midrange, it was tough to find heads that did both. If you're only revving to the mid 6s though, a set of ported 2vs might make all the power you'd need.

 

[nosaj122081]

The program more or less seems to be telling me that with a motor that revs to 7000 that even on a stroker the 4V heads lay down in the sub-4000 range, even on a 393 they seem to make power from about 4000-8000 RPM. From what EA states, the 4V heads almost ALWAYS seem like a bad idea for a street engine, a ported set of 2Vs make better numbers period in the sub 7k range regardless of what cam its paired with.

 

[Hack]

The program more or less seems to be telling me that with a motor that revs to 7000 that even on a stroker the 4V heads lay down in the sub-4000 range, even on a 393 they seem to make power from about 4000-8000 RPM. From what EA states, the 4V heads almost ALWAYS seem like a bad idea for a street engine, a ported set of 2Vs make better numbers period in the sub 7k range regardless of what cam its paired with.

That's what I would expect from what I've read. Also, the open chamber heads are supposed to not be great. A lot of people run custom-ground cams as well. I guess you can run quite high compression with pump gas and a ton of cam overlap. The overlap effectively reduces the compression at low rpm.

If you want to talk to someone with actual experience with Clevelands, try this forum.
http://www.corral.net/forums/index.php?s=

There's a big block/cleveland forum in there. There are people who race their Clevelands. People don't post very often, but they seem to know what they're talking about.

Good luck.

 

[dodgestang]

I tried using those crap software packages for my Stroker.....they aint worth the price you aren't paying for them.....The best I was able to do was produce numbers 'close' to my peaks, but the curves were so far off from real life...it was all just garbage.

The 4v will not 'lay' down for you. My car has an awesome acceleration curve from stop till I stop it from fear with a nearly flat torque line for a good 3k+

 

[Hack]

I tried using those crap software packages for my Stroker.....they aint worth the price you aren't paying for them.....The best I was able to do was produce numbers 'close' to my peaks, but the curves were so far off from real life...it was all just garbage.

The 4v will not 'lay' down for you. My car has an awesome acceleration curve from stop till I stop it from fear with a nearly flat torque line for a good 3k+

Hey Nick,
I was scoping your website and noticed you've dynoed your 408C. Would you care to post torque/horsepower vs. rpm by thousands?

 

[dodgestang]

You mean like this?

Or this?

 

[Hack]

hehe, that'll do. The 408 makes some real good power!

Do you run a 3,000 rpm stall converter? I don't know anything about dyno runs, do they always start at such a high rpm?

 

[dodgestang]

Yes I have a 3k stall in the motor. Its also an Auto....so you have to start with the car in 3rd for the 1:1 ratio.....with a chassis dyno you ussually always see the charts start up above 2500 or so....at least in my expereince anyway