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Heads Revisited....

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    Distinguished Member David 519's Avatar
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    Default Heads Revisited....

    OK, I've been thinking about all that was posted in the previous thread regarding the 572 and "choking it". In choosing a proper head, I'm of the mind that you need enough port flow for 110% VE at peak RPM. In reality, I think it's more like 110% VE at the torque peak, but I'm on thin ice here. Obviously I must be wrong on some point since everything you read points to using much more air flow than just 100% cylinder filling.
    The reason for my question is 2 fold, general curiosity and also I'm at the point I need to buy some heads for my new build. The application is a flatbottom drag boat destined for the 8.0 bracket class.
    My new combo is a 588 BBC (4.5 Stroke 4.560 Bore), will end up around 14.5 CR with the pistons I'm using. With that much stroke, I don't want to rev it much past 7800 or so (to high piston speed) I'm guessing my cam will end up around 280 [email protected] to make power around my target RPM. In the past I've had good luck with 110 degree lobe centers in slightly smaller combo. Finally, I'd like to get close to 1000 HP.
    Based on 100% VE at 7800 RPM, it calculates to 331 CMF. That's theory, so what's reality? Based on budget and existing components, I seem have it narrowed it down Dart Pro 1's or Brodix -2Xtra's with the Darts slightly ahead. The Dart 345's advertised flow is 397 intake, 266 ex @.800" lift using a 2.300 valve. Not bad, but the exhaust flow seems a bit low compared to intake. The 355 CNC's bump that up to 415/303 CFM.
    So is it really worth the extra $$ for the CNC ported heads? Engine Jr. thinks so. Each 20 CFM seems to be worth about 60 HP. However, it's a fairly basic program and not sure how accurate it is at these HP levels. It did pretty good with my SBC stuff, but who knows.
    So guys, help me out and let me know what you think. I know I asked a lot of questions, but any feedback will help. Thanks!!

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    steelcomp was here
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    Quote Originally Posted by David 519 View Post
    OK, I've been thinking about all that was posted in the previous thread regarding the 572 and "choking it". In choosing a proper head, I'm of the mind that you need enough port flow for 110% VE at peak RPM. In reality, I think it's more like 110% VE at the torque peak, but I'm on thin ice here. Obviously I must be wrong on some point since everything you read points to using much more air flow than just 100% cylinder filling.
    The reason for my question is 2 fold, general curiosity and also I'm at the point I need to buy some heads for my new build. The application is a flatbottom drag boat destined for the 8.0 bracket class.
    My new combo is a 588 BBC (4.5 Stroke 4.560 Bore), will end up around 14.5 CR with the pistons I'm using. With that much stroke, I don't want to rev it much past 7800 or so (to high piston speed) I'm guessing my cam will end up around 280 [email protected] to make power around my target RPM. In the past I've had good luck with 110 degree lobe centers in slightly smaller combo. Finally, I'd like to get close to 1000 HP.
    Based on 100% VE at 7800 RPM, it calculates to 331 CMF. That's theory, so what's reality? Based on budget and existing components, I seem have it narrowed it down Dart Pro 1's or Brodix -2Xtra's with the Darts slightly ahead. The Dart 345's advertised flow is 397 intake, 266 ex @.800" lift using a 2.300 valve. Not bad, but the exhaust flow seems a bit low compared to intake. The 355 CNC's bump that up to 415/303 CFM.
    So is it really worth the extra $$ for the CNC ported heads? Engine Jr. thinks so. Each 20 CFM seems to be worth about 60 HP. However, it's a fairly basic program and not sure how accurate it is at these HP levels. It did pretty good with my SBC stuff, but who knows.
    So guys, help me out and let me know what you think. I know I asked a lot of questions, but any feedback will help. Thanks!!
    According to my numbers, I get 588ci @ 7800 rpm, with 280 @.050 needing 426cfm. You don't want to max out the heads, so you need that at as low a lift as possible, preferably 50%-60%. You're looking at big numbers here. Probably something like a Profiler, Big Chief, Raptor, or something other than conventional style chevy heads.
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    Resident Ford Nut Sleeper CP's Avatar
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    Did I miss it; what intake are you going to use?

    I think Steel said it, you are going to need over 420 CFMs.

    Sleeper CP

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    David,
    To support 588CID to 7800 rpm you are going to need runner volume and flow. If your going a traditional style asymetrical BBC your going to need a a ported set of heads in the 360cc plus range. The BMF 385's from CFE have been quite impressive, a set of AFR 357's with some additional porting, and or Brodix and Dart with CNC porting.

    Best solution is as Steelcomp suggested and go Dart Chiefs or Brodix Big Dukes with the symeterical port. These types of heads are specifically built for large CID high rpm engines and will make more power then the conventional BBC asymetric head. The downfall of these is this is an expensive route to go and if you already have pistons they wll not work wth this style of head and of course an intake that you may have is not going to work either.

    Either way you are looking at between 8 to 15K for upper half to feed a 588 to almost 8000 rpm.
    Chris Straub
    Straub Technologies

    3HP is an A$$ Whooping!!! JW

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    Distinguished Member David 519's Avatar
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    Quote Originally Posted by Sleeper CP View Post
    Did I miss it; what intake are you going to use?

    I think Steel said it, you are going to need over 420 CFMs.

    Sleeper CP
    We have an Edelbrock TR-2 tunnel ram with a pair of 9375 Dominators...This years racing budget dictates me trying to make the best out of what I have. Although Big Cheifs and some of the other aftermarket style heads are a significant improvement, I'd have to throw away to many of my existing parts and pushing the budget over the top.
    So how are you guys coming up with 420 CFM? As I said before, the basic math comes out much lower than that. So what am I missing.
    Thanks!

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    If this was my engine, wants, needs, etc I'd be calling a person like Curtis Boggs at Race Flow Development http://www.raceflowdevelopment.com/RFD-company.htm

    He/ they eat/sleep/dream BBC's in all motorsport aspects. They have been a premier BBC cyl head porting company for oodles of years. Their 24° cnc Edelbrock's (not the same Ed's we see in catalogs) have been making 1000+hp even on smaller cid's. Prices aren't bad either.

    Now if you want to make a few more hundred hp than this, then, well, the exotics will be needed.

    Call Curtis Boggs, Carl Foltz (CFE - who'm makes BMF heads), or someone like them that will get the power for you with convential style heads. Don't order anything without making a call. They have tons of porting (hand and cnc) programs for an unimaginable amt of BBC build ups.

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    Quote Originally Posted by David 519 View Post
    So how are you guys coming up with 420 CFM? As I said before, the basic math comes out much lower than that. So what am I missing.
    Thanks!
    Both Chris and Scott know more about this than I do, I can tell you this from dyno info that I have been around: If you can achieve 2.1 hp per CFM you are doing something really good with your engine combination. That 2.1 number comes from a good single 4 barrel. I have not done testing with two 4's to give you a baseline.

    However, from what I know about Steel's engine and how good his build was to get 821 hp out of 467 ci with a 345 cfm head he was achieving 2.38 hp per cfm. His engine was making 1.76 hp per cubic inch so it was a Stout build by anyone's measuring stick.

    So if you can achieve 2.4 hp per cfm with a TR with two dominator's you will be doing quite well for yourself. 425 cfm x 2.4 hp/cfm = 1,008 hp.

    If you can achieve that number you are kicking ass. Just a wild ass quess from me.

    Just my .02

    Sleeper CP

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    Distinguished Member David 519's Avatar
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    Thanks to all that have contributed so far, I do appreciate it. There have been a bunch of intersting comments here and in the BEMP/vacuum pump threads.
    I've never heard HP directly related to air flow the way you guys are, though it makes sense. My last BBC, built using similar componets but a bit smaller CID, made right at 1.7 HP/CID. We did port/flow the heads, but I've lost my notes on what they were..We're hoping to come close to the same 1.7 HP/CID with this engine.
    At any rate, you guys have given me a lot to think about. We still have a lot to do, but we're hoping to have this motor on the dyno in early March... I'll let everyone know how it turns out.

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    Quote Originally Posted by David 519 View Post
    Thanks to all that have contributed so far, I do appreciate it. There have been a bunch of intersting comments here and in the BEMP/vacuum pump threads.
    I've never heard HP directly related to air flow the way you guys are, though it makes sense. My last BBC, built using similar componets but a bit smaller CID, made right at 1.7 HP/CID. We did port/flow the heads, but I've lost my notes on what they were..We're hoping to come close to the same 1.7 HP/CID with this engine.
    At any rate, you guys have given me a lot to think about. We still have a lot to do, but we're hoping to have this motor on the dyno in early March... I'll let everyone know how it turns out.
    Since you're sticking with conventional heads, I'd look into the BMF 385's. The Canfield casting is one of my favorites for custom porting, right next to the Brodix casting. I've read nothing but good about the BMF head, and you're going to need something in that range. You need to figure your CSA and do some comparisons. That Edelbrock TR might be a little bit of a hinderance.
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    Quote Originally Posted by steelcomp View Post
    Since you're sticking with conventional heads, I'd look into the BMF 385's. The Canfield casting is one of my favorites for custom porting, right next to the Brodix casting. I've read nothing but good about the BMF head, and you're going to need something in that range. You need to figure your CSA and do some comparisons. That Edelbrock TR might be a little bit of a hinderance.
    Scott,

    Will these heads flow the numbers you mentioned?

    Have you built any heads for customers using these?

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    Quote Originally Posted by Morg View Post
    Scott,

    Will these heads flow the numbers you mentioned?

    Have you built any heads for customers using these?
    Yes the BMF 385's flow over 440 @ .900" (according to them) They have a 405cc as well.
    No I haven't built a set...would love to, though.
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    David519,

    I'm running a 565ci BBC in my flat. I have the Dart Pro1 Heads 325's with the 119 cc chamber. The heads have been hogged out by thy local motor guy, and I'm running the TR-2 tunnle ram with two Holly HP's. 13 to 1 comp.

    She will run 115 mph @ 7,500 rpm hear in Cali near sea level. If I head over the hill to Lake Lahonton the best she will spin with any tune up is 6,500 rpm.

    With that size NA motor you will be at the mercy of the head.

    Have you already built the short block?

    Cole Man
    Last edited by Cole Man II; 01-31-2008 at 09:15 PM.

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    Distinguished Member David 519's Avatar
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    Quote Originally Posted by Cole Man II View Post
    David519,

    I'm running a 565ci BBC in my flat. I have the Dart Pro1 Heads 325's with the 119 cc chamber. The heads have been hogged out by thy local motor guy, and I'm running the TR-2 tunnle ram with two Holly HP's. 13 to 1 comp.

    She will run 115 mph @ 7,500 rpm hear in Cali near sea level. If I head over the hill to Lake Lahonton the best she will spin with any tune up is 6,500 rpm.

    With that size NA motor you will be at the mercy of the head.

    Have you already built the short block?

    Cole Man
    Cole Man, my last boat/engine was similar to yours except it was a 509 CID. That motor made 850 [email protected] RPM and 820 lb/ft [email protected] RPM. We ran consistant mid 8.30's at 130-132 on the motor. We used a 50-75 HP NOS shot to hit the 8.0 index. With NOS, we consistantly ran in the 133-136 mph range. What I'm trying to do with this motor is hit the 8.0 on just motor. In a decent flat, you need about 950 HP to make that happen consistantly.
    This engine started as a pile of parts I picked up from an acquaintence. I got basically a complete motor less pistons and cam. It was mostly new stuff, all high quality, but not all suitable for my application. I sold off whatever I didn't want to use and starting from there. With that bunch of parts came a set of small Pro 1's. I knew 325 cc intake with a 2.25 valve they had wasn't going to be even close, so I sold them. That said, I'm waiting on pistons, but have the short block about ready to go together.
    I'm trying to keep the budget real since this is my first year back racing boats after being away for a while racing cars. And since it's a bracket class, if I come up short, I'll throw a bottle in it to close the gap. It's way cheaper than throwing $10-15k at a Big Chief top end!!
    Again, thanks all, I've been learning a bunch just following the comments.

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    David, I think realistically, and this is just my humble opinion, the idea of throwing a little nos at less HP may be your best bet. To get the HP you want is probably going to require closer to 500cfm. Even if you were to step up to the BMF's, (or something equivalent) I think your TR2 intake is going to fall short. You're in the territory of at least a Dart TR (re-worked) or a sheet metal TR intake. With conventional style heads you're looking at BIG lift numbers, expensive springs, mucho pressure or expensive high ratio rockers and without a doubt, a shaft rocker set up. Ti intake valves would almost be a must. It's not just the heads that get expensive...everything that goes with the package adds up.
    Please don't misunderstand my intention here. I'm not trying to throw water on your fire, just trying to offer you my limited knowledge and insight. I don't think a conventional style top end that's going to give you your target power is going to be much less...if any, than a Big Chief top end. If you target your HP level a little lower for now and add the nos, you can always upgrade to what you want with all engine, and not be disappointed or frustrated in the process.
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