205s will support well over that. I like your thinking here though, give yourself a pretty healthy motor and have a majority of parts that can be switched over when you build a windsor
440 is actually a very conservative number, too. I've seen them do waaay more than that.
When I first contacted Mike, he was a little hesitant to sell me the 205s to put on my 302. He was worried that they were on the "too big" side, and that if I went with a cam that had too much duration/overlap, it would probably be an absolute dog down low. But once I talked to him about my plans to run a "tame" duration cam with big lift, and that the heads would eventually see boost and/or a stroker, he warmed up to the idea.
AFR205s actually have significantly smaller ports than the TW205. I think you're talking about an engine dyno, because it would take more than box-stock AFR205s to put 600 to the tire n/a.
Chris
Honestly Chris, I think the head velocity thing is a stumbling block in a lot of people's thinking. I think that you do have to maintain some amount of velocity in the intake port, but what you have to consider is, what exactly is not enough velocity? If you read about what some cam designers and cylinder head porters say, they try to nail down what is too much velocity. Terms like "sonic choke" come into play. But "not enough" velocity? It's just this kind of voodoo thing that is hard to define, and for whatever reason, people would rather err to the side of "smaller" parts.
The more homework I do on the subject, the more I think that we (SBF guys) limit ourselves with this thinking. I mean, a significant amount of aftermarket LS heads are flowing the the 350cfm range. Ford put heads on the Coyote that flow 300cfm, and some of these aftermarket porters are already cranking out heads that flow around 340. Hell, FRPP sells a basic CNC 3V 4.6L head that flows 272 on the intake. That's like an AFR 185, but on an even smaller engine!
And here, pushrod 5.0 guys are still using heads that barely manage 250cfm. At some point, you've got to ask yourself, "why?" I understand flow numbers are NOT everything, but this stuff has really got my gears turning.
I also see magazines do dyno tests, and sometimes they stumble into some really revealing results. And I know you don't race dynos, and a magazine article is only worth what their advertisers paid them for it, but this stuff has got me thinking, too. MM&FF recently did a dyno test of a series of Dart Pro-1 cylinder heads, and long story short, the biggest head they tried, which supposedly flowed 325 on the intake, had the EXACT same powerband as the smallest head they tried (on a 306), up to about 5800rpm, where the bigger head started to walk away. Hmmmmmm, so it sounds to me like the bigger head gave you your cake, and let you eat it too? Again, 'ol NikwoaC's gears are turning.
Article for reference:
Cylinder Head Comparison Test - Muscle Mustangs & Fast Fords Magazine
I don't know, maybe I'm completely off base here, and this thing won't turn the tires over in wet grass. if that's the case, you guys can all point and laugh. But if not, if the engine ends up being the animal I think it might be, I hope it gets some other people's gears turning, too.
I hate to see the inside of your head. I just buy parts and slap 'em together, hope for the best lol
Just a thought....
You had mentioned that you are just doing a hone and a re-ring. Isn't your block an 86 vintage with flattop pistons, with no valve relief's? I thought the limit that you could go with those pistons was in the .500" range before you come into PTV issues?
That is the only thing that I have seen that stands out to me.
Good luck on the build!
Dart Head Test 302
RPM 195 210 225
2,800 159 171 168
3,000 186 189 187
3,300 217 222 221
3,500 237 241 239
3,800 267 266 266
4,000 283 281 281
4,300 305 301 301
4,500 318 311 311
4,800 336 325 328
5,000 346 341 340
5,300 366 361 361
5,500 374 372 371
5,800 383 387 385
6,000 389 395 395
6,200 386 399 399
Great discussion. As you can see in my comments, I'm not thoroughly convinced that port velocity is a big deal. One of my early mentors, Ed Curtis, is very much in the port velocity camp, and has forgotten more than I'll ever know about engines. It's hard for me to get away from his ideas on the subject.
About all of these other heads for the other engines you're referencing, how did the cross-sectional area or port volume compare? All you mentioned was flow numbers. It's obvious that you want the most flow you can get, but conventional wisdom says you're going to pick a head that's somewhere between the area where your engine doesn't need more flow to fill the cylinder and where the additional cross-sectional area simply slows the port velocity.
I don't think you'd argue the fact that some engines produce in excess of 100% VE. How does that happen? The only ways, in my mind, is by taking advantage of the inertia of air and taking advantage of helmholtz tuning once the cylinder is full and there is no longer a positive pressure differential from the atmosphere or ambient air pressure, and what's in the cylinder. The inertia of the air is what pushes the VE over 100%. It stands to reason that the more inertia that air has, the more it will fill the cylinder.
From your article:
That actually looks pretty conclusive to me. Clearly the 195cc head outperforms from 3800-5800 RPM. Honestly, it feels like the writer was biased in his assessment because he doesn't seem to recognize this in his conclusions except to say that the smaller headers made the difference. I would submit that the cam was still fairly healthy and not optimal for the smaller heads even on the 302. Again, I would like to see seperate optimized combinations including the cam. Get a specialist like Ed Curtis who believes in port velocity, and then get a guy who espouses your beliefs to build optimized combos including heads/cam/and intake and have them shoot for a 6000rpm shift point with a 302. Who would come out on top? Right now my money would be on Ed, even if you matched him up with someone of equal skill.
Now, you're not talking about a huge amount of loss - only about 8hp at 4800RPM. Still, if you're shifting at the stock limiter, the bigger heads are behind. That little headed car looks like it's going to win by around a car length. 3800-5800 is nearly the entire powerband.
Fortunately for the author's argument, they didn't get around to testing the 170cc heads on this motor.
how much did they charge you to port match that intake?
a guy with a wife who wants to go to bed, that's a change
you guys lost me at your velocity talk, I'm waiting for something I understand - pictures