AFR 290 VS DART Pro 1 head
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AFR 290 VS DART Pro 1 head

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    280 Profile Cat W/575sci JRider's Avatar
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    Default AFR 290 VS DART Pro 1 head

    OK...first post for me in the Dyno Room. I have a 575sci that I have already upgraded blower to a stripped 871 littlefield (triangulated discharge) and have added a Whipple lowpro intercooler/manifold. I have the motor torn down for inspection/rering. I have decided to upgrade to a hydraulic roller cam and ditch the cast iron heads. I have been in contact with Bob Madera of Marine Kinetics as far as cam selection and he is recommending a few different AFR heads. The AFR 290 is available rite away (time is an issue) but will require the blower manifold to have the ports closed down with epoxy/JB weld as it is considered a rectangled oval port head (Rovel port is what it is called). I believe it uses zz502 gaskets if that helps any. These heads flow excellent and according to Bob M will fill the cylinder efficiently with the excellent port velocity. He also said that I should see a dramatic drop in boost as the heads are that efficient.

    My problem is that I am having a hard time shelling out $3391 for that set of heads when I can get Dart pro 1 rectangle marine heads for $2775 (both sets are hard anodized marine). The darts are 310/325cc intake but do not flow as well as the AFR 290...but I am forced induction, so how much that matters?...I dont know. I am also a little hesitant to do the JB weld mod to my intake to make it work. The AFRs have better number on the exhaust flow as well which seems to be an area that needs the most improvement. I would imagine that my cam would be slightly over .600 lift and the AFRs are at 283cfm there. The Darts dont flow as well in that range.

    Anybody have any suggestions?

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    I have a set of AFR 325's that have 5 minutes of run time. They were built by Dougans machine in SoCal with inconel exhaust valves and valve guides that are for blower application. The springs are for a hyd roller cam .600" gross lift. Pm if you are interested.

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    steelcomp was here
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    I wouldn't go to the expense and trouble of running those 290's on your 502 and IMO they're going to be a little small for a blown app. You're better off with a set of as-cast AFR 305's or I have Canfield 310's available. Either head has plenty of flow for what you're doing. As far as being "marinized" with the anodizing, from what I've seen, all the really critical areas that really need protection are machined surfaces that don't get anodized anyway like deck surfaces and intake surfaces. This seems to be where most of the damage occurs that needs repairing. I think the 325's listed above are a little big for what you want, but if the price is right there could be worse choices. The right cam choice can address that.
    One thing I need to add about the 325 AFR's...they come with a 2.300 intake valve and I'm not sure the 502 piston has enough clearance in the valve pocket. Something else to consider.
    Last edited by scott foxwell; 06-25-2013 at 02:04 PM.
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    Quote Originally Posted by welldigger00 View Post
    I have a set of AFR 325's that have 5 minutes of run time. They were built by Dougans machine in SoCal with inconel exhaust valves and valve guides that are for blower application. The springs are for a hyd roller cam .600" gross lift. Pm if you are interested.

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    These heads are better than the AFR 290 or the Dart Pro 1 310.

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    Quote Originally Posted by PCE680 View Post
    These heads are better than the AFR 290 or the Dart Pro 1 310.
    If these AFR heads are priced right you might really consider buying them. I agree........these are better than the AFR 290 and Pro 1 heads.

    I had really good luck with my AFR 315's, they flow good numbers.

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    First $2500 takes them, these are practically brand new. Shipping not included.

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    Default Bought the heads

    And rockers pushrods headbolts etc. Trying to decide if I should mill the heads. My cr is only 7.5:1 stock with 118cc heads with JE dished blower pistons. Would like to be around 8.5...or I can crank up the boost. If the block needed to be bored I would have changed the pistons. Any suggestions?

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    gn7
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    If you want the marine anodized heads and small port I would almost be tempted to go with the Edelbrock Marine version of the head that comes on the ZZ502. Pretty decent valves, and a smaller 110CC chamber.



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    Word has it the Zz502 "rovel" port heads flow excellent for motors around that size. The afr 290s would have worked well but I didnt want to epoxy my whipple manifold/chiller. With forced induction I was not too worried about the intake side. I bought the heads and are going to use them...just trying to decide if I should mill them

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    Quote Originally Posted by JRider View Post
    He also said that I should see a dramatic drop in boost as the heads are that efficient. ?
    I realise that is someone else's statement, but it makes no sense to me.

    In other words, If I took off the out of the box Dart 345 heads I have been running for years and put on a better flowing set of heads, my boost # would magically go down ? Makes no sense.
    If it's being force fed now how could that make a difference ?

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    I think I could run more boost but it's a real hand full right now

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    Unchained.... "boost" is psi measured at the intake manifold. If the bigger head breathes better, it will take in more air on the charge and leave less back pressure in the manifold where the boost is read at. It doesn't mean you're getting less air forced in where it counts, or making less power. It means there's less pressure in the intake. That's why "boost" is so controversial.

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    Quote Originally Posted by Unchained View Post
    I realise that is someone else's statement, but it makes no sense to me.

    In other words, If I took off the out of the box Dart 345 heads I have been running for years and put on a better flowing set of heads, my boost # would magically go down ? Makes no sense.
    If it's being force fed now how could that make a difference ?
    There was a time Mark, when I thought you had this whole boost thing down pat, along with a lot of other stuff.

    No, not necessarily. If your heads are already loading your cylinders to 100% of boost pressure, then larger or another set of "better" flowing heads will not necessarily make your boost go down. And with a TURBO things are a little different than a roots because you exhaust that drives your turbo is 100% dependent on the INTAKE to deliver MORE fuel and AIR to make a BIGGER load charge to drive the trubo even faster, and so on goes the circle.
    So if you kill the intake, you also kill the boost because you can't get as much fuel and air in the hole. Less exhaust, less turbo heat energy, less boost, and so the circle goes.

    With a ROOTS, it all about the port flow, both the intake and the exhaust port, and the camshaft timing, both the intake and the exhaust.
    Roots are positive displacement pumps, feeding a positive displacement pump. If the manifold pressure drops, that means that air went somewhere. Most likey into the cylinders. Never make the assumption that you are filling your cylinders to their max, or to manifold pressure. That ONLY happens if the heads are up to the task.



    Boost pressure is 100% a direct reading of flow resistance and NOTHING MORE. If you put a set of GM peanut ports under a 14/71 and turn it 30% over, it will have way more boost than a set of CNC well design ports of the CORRECT size, the boost will PLUMMET, but the power will sky rocket. On one the pressure is stuck in the manifold and can't get thru. The other is filling the cylinders, which ADDS to the space the blower must fill, and therefore the boost drops.

    If you cork the exhaust, the boost will climb because the cylinder doesn't complete empty, and the remianing gases take up space the incoming air would normally fill. So it backs up in the manifold just like too small of a intake port. Pull 4 exhaust pushrods out of a roots blown deal and watch the boost shoot up.
    Little different than too small of an exhaust turning a turbo that now can't spin as fast because of lack of flow to it.

    Camshaft play a huge part in boost pressure with a roots too. Other wise I would run a stock cam. After all, its under pressure

    We have been thrun this many many many times. Its real simple Mark. There is absolutly NOTHING about a N/A head that does not apply to a blower head. NOTHING!!! The head can be too big, and the head can be too small. As can the camshaft. As can be the exhaust.

    If the current heads DIDN'T lower his boost, he will have wasted his money. It would prove that the old heads were filling his cylinder 100%. at what ever boost'RPM he was running the engine. I would drop a 3 thou tomorrow if I could find a way to drop my boost 2 lbs without just tossing it out an open exhaust valve. I am not at all interested in raising my manifold pressure at all. Thats the last thing I want to see on the gauge.



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    Last edited by gn7; 06-26-2013 at 04:35 PM.

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    Quote Originally Posted by JRider View Post
    Word has it the Zz502 "rovel" port heads flow excellent for motors around that size. The afr 290s would have worked well but I didnt want to epoxy my whipple manifold/chiller. With forced induction I was not too worried about the intake side. I bought the heads and are going to use them...just trying to decide if I should mill them
    Between the fact that your compression is lower and you have a set of heads that are more detonation resistant, I would crank up the boost. It may not have the low end grunt it did with the compression a little higher, but it will be in a pretty small range in then bottom end. By cranking the speed of the blower, it will move more air sooner, at a lower RPM than it had been and help cover up the compression lose. More you open the throttle, which is the ONLY thing that controls boost on a roots, the more power it will make compared to the higher compression/lower boost.
    You will gain more full throttle power, even at low RPM, and more top end full RPM speed with the blower spinning faster.

    The THROTTLE on a roots determines the amount of boost and power, not the rpm of the engine. It may feel alittle sogging right off idle with small throttle openings, but that will vanish the instant you push on the throttle.
    If you know you have 7.5 CR, you can get away with about 1 to 1 on that blower, with pump gas and around 30-32 timing. You might get away with a little more with the chiller, but I think I would start there.



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