NikwoaC's "Commitment Issues" Engine Build

Discussion in '1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-' started by NIKwoaC, Mar 12, 2011.

  1. 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 :nice:
  2. He's right to question your judgment. I wouldn't choose a TW205 or the cross-section equivalent AFR225 for a 302. Those are the kind of heads that are right at home on 351-408Ws, even higher revving ones. With your future plans, though, you won't have to waste time and money on another set of heads and an intake.

    I'd love to see a side-by-side comparo of AFR165s on a 302 with a custom cam and tune, and then a monster head like an AFR225 or TFS TW205 with a custom cam and tune. There's always a lot of talk from some about how you can correctly cam a big head to do just as well on a small motor. I think I'm in the port-velocity camp, though. I believe the AFR165s are going to outperform the big head through most of the powerband, and if limited to 6000 RPM, I can't imagine that the big heads will make up for it on the 1/4.

    In any case, you're right about the conservatism. I'm always that way on here because I don't like to tell someone that they can actually go 500+rwhp, which is the case with these heads. In fact, the general rule of thumb is that you can make 2 crank hp for every CFM the heads flow. If I remember right, these are 320-ish CFM heads. Nevertheless, to get that power from a street combo, you'll need a lot of cubes to keep the powerband low, and the idle tolerable.

    It'll be fun to see the car come alive in the upper powerband, and to see how it does down-low. Even LS motors at 346 c.i. with the same type of valve angle don't typically go bigger than a 205cc head on a stock shortblock.

  3. They seem to be right at home on my 410w (AFR 205s). Supposedly made around 600+ on the dyno, wont know the real number until next month but you guys may be right that a smaller head would be at home on a smaller cube engine like a 302. But considering his plans for a bigger motor in the future, he'll make plenty good power on this setup to have fun until the other motor gets done. Im all about not buying things twice. Especially considering the cost of a set of heads like those. Matched with a custom cam, i think it will turn out to be a pretty healthy motor. Start of the thread, i thought he was just going to do a refresh and drop it back in for now, definitely think you'll obviously be much happier this way. That and i love a 4eyes car so you cant really go wrong :D
  4. 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.

  5. The parts look great nik. I was considering using those TW205s or the "fast as cast" 195cc on my next project... I don't think you'll be disappointed in the direction you're going at all. Looking forward to seeing more.
  6. 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. :nice:
  7. I hate to see the inside of your head. I just buy parts and slap 'em together, hope for the best lol
    Cory Berg likes this.
  8. Yeah FWHP not RWHP. Sorry for the confusion

  9. another good read and helps further the debate beyond velocity but port volume, intake runner length, etc..Brodix LH 17 Degree Cylinder Heads - Muscle Mustangs & Fast Fords Magazine
  10. Haha, sometimes, I hate it too. I overthink this stuff. A LOT.
  11. 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!
  12. Yea, it's an '86, and yea, it has the flattop pistons. There are a lot of misconceptions about piston to valve clearance, but suffice to say that peak lift has nothing to do with it. PtV happens when the piston is at TDC between the exhaust and intake stroke, so it's really more of a concern as to what your valves are doing at that point. The exhaust valve is closing and the intake valve is beginning to open, but neither is anywhere near its peak lift. This is the overlap period, so generally speaking, cams with shorter duration and less overlap have less problems with PtV clearance, regardless of what peak lift is. The cam that is going into this engine has a good amount of lift, but pretty short duration numbers. Shouldn't be a problem.

    It also has a LOT to do with your cylinder head design and valve placement. The Twisted Wedge design is very forgiving with PtV clearance.
  13. 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.
  14. I see what you're getting at, Chris, but check out how the two bigger heads actually "outperform" the smaller head UNDER 3800rpm. Wouldn't conventional wisdom tell us that this is the opposite of what we're seeing? Honestly, I think that MOST of the variation in numbers we're seeing under ~5800 RPM are simply fluctuations in environmental variables. For the most part, we're looking at a HIGH of 3-4% difference in power numbers up to 5800 rpm. It's a crap shoot, the numbers are too close to make heads or tails of it. That is, until 6000rpm, when the bigger heads start to run away.

    I'll have to continue this discussion later, the wifey is nagging at me to go to bed. Later dudes!
  15. 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
  16. This is what's killing me right now...go with higher velocity 205's or larger volume 225's ......:bang:
  17. It's still is going to come down to velocity , port volume and runner length. a head that is too big is going to have a lack of low end-mid range torque, I just don't see any other way around it and really show up on the track. a head that flows a certian cfm could have a different port volume from a head that flows the same cfm but they both make different power. higher port velocity + higher air speeds fills the cylinders faster, so even though a given head flows X cfms it's port may be larger than other head flowing the same cfm's and thus producing slightly less hp due the drop in velocity. OK next.
  18. how much did they charge you to port match that intake?
  19. $150 was the charge on the quote. That covers any fitment issues, milling, whatever. I guess they mock it up on a production block with the heads and a set of gaskets and make sure everything sits OK.
  20. I do have more pics for you guys, but I need to upload them. I painted the block, timing cover, oil pan and bellhousing in an engine enamel cast iron grey color. Looks pretty decent. I'll get on that later tonight or maybe tomorrow.