You need to ask yourself how tolerant you want to be as far as streetability in this. Bigger the intake (plenum volume), bigger the cam (lift, duration and overlap) and bigger the heads, the higher in the rpm range the power will come in at. It's not fun having a motor that doesn't make power till 3+ grand on the street, having to baby it off stops to get the car moving, trying to get it to idle less than 1000 -1500rpm. I chose to go with mid range heads on my 331 14 years ago (Canfield equivalent of AFR165's) Cam is a Ford Z303 with 1.7 rockers (112* LSA) Topped with a repop 3x2 setup (250 cfm Holleys) on a high rise dual plane. This motor comes on at 1500, pulls to 6500, levels off at 7 grand. CR is 10.4 to 1. Runs on 91-93 octane fuel (alternate between fuel ups). These heads were on a 302 previously that was topped with a Vic Jr and a Holley 650 DP carb, cammed with a B303 and 1.7's. Power didn't come in till 3 grand. Wasn't much fun trying to get moving with it on the street in traffic. The 331's a completely different animal. Tame as a kitten till you romp on the go pedal.
Okay, that makes sense. According to some more research, .200, .400 and .500 flow rates at lower rpms is more what to look at for a more street-able motor, so if I can find a good head with flow rates with those lifts with a cam that matches, and with a CC that keeps the compression rate to run on street gas, that should be the "happy" spot for a street drivable na motor. Correct me if I am wrong, trying to learn.
Don't ever buy cylinder heads based solely on flow rates. And especially if you don't know how to match(more like MATH!) them with the rest of the supporting parts. Compression ratio, trans type, gears, vehicle weight, induction, rpm expectation?.. ton's of variables. Just far too many to list. IOW.. maybe somewhere short of super elite pro-stock type stuff running rediculously narrow power bands, for a dual duty car it's generally better to have a cylinder head that is JUST big enough to support the engines volumetric demand (which is controlled by the cams rpm range).. than another geared only towards improving the engines peak horsepower. As baddad already said.. part throttle power matters too. This gives a wider powerband that hits a milder converter harder and carries shifts a little better with less rpm drop. Need TONS of information to help you design a motor combo for whatever you describe. Actual street/strip percentages needs to be factored in big time. Is it more enjoyable for you to feel like you have a street motor with race gears.. or a race motor with street gears? Big question you need to ask yourself is how much power do you want?.. and then be realistic about how much power you can actually afford? To greatly increase the power of an N/A motor you need to grow it as big as you can afford.. then from there you start spinning it faster to move more air. The faster you spin it the more expensive it will get. Main reason why turbo's are such good bang for the buck as they squeeze more air in without having to grow or spin the motor so hard. Very few mods needed in the very expensive valvetrain department.
In my opinion, go with an EFI cam with a wide LSA, combine that with a high rise dual plane, topped with a carb around 650 cfm in a mech secondary, or 700-750 cfm in a vac sec, those three components will enhance the lower rpms to give it more oomph on the street by keeping up the airflow. Don't be fooled by the EFI cam, these make a carb work even better than narrow LSA cams with tons of overlap. They really give up nothing on the top end.
EFI cams with wider overlaps are well known to be a necessary compromise for the engine sensors signal consistency so the ecm can keep up with what the motor actually wants. The rest is based on oem emmissions related requirements.. not because they're best for higher average power production. If that restriction wasn't in place there would be more cams with tighter lsa's running around the streets simply because they bring the torque in quicker and peak out slightly higher than similar grind with wider efi friendly lsa. About the only time a wider lsa cam bests a tighter lobed cam for peak torque production is when the cylinder heads are extremely efficient(such as larger valve/port race heads), usually with much larger valve to bore ratio, and/or when the duration climbs high enough that the lobes need to be pushed away from one another to regain the proper overlap window size. Call a custom cam designer and tell them what you have and what you want to do with the engine. I have cash says they will sell you something with 110 or tighter lsa vs a computer friendly 114. The weaker the exhaust port the tighter lsa needed to shore up the weakness without having to resort towards more extreme exhaust durations to get sufficient overlap periods.
Probably because we don't see many Yates headed motors around these parts. LOL It's like this. High angle heads like Fords 20° and Chevy 23° are layed over so far you end up with a wedge shaped chamber which is very shallow on one side. Cut the head too much and you start eating into the intakes seat and flow goes downhill on that short side radius portion of the valves curtain. Going from a fast moving port and dumping directly into a large cylinder kills pressure recovery on that portion of the valves curtain area. Not good at all. Conversely, take a racing head with the valves stood up at shallower angles 10-12° and the short side of the chamber gets significantly deeper which helps pressure recovery, aiding in greater flow in that toughest turned area of the valve curtain. Can also mill a hell of a lot more material off the shallower valve angle heads firedeck before getting into the valveseat. Biggest problem with smaller chambers is that they kill flow in trade for more power from increased compression ratios and generally require higher lift cams. On the flip side you can blow out the combustion chamber walls to gain more dry flow(flowbench glory).. but the quality of flow around the entire valves curtian can take a dump on the running motor. This is because all that extra long side flow(roof flow) slams into a cylinder wall and centrifuges fuel right out of the moving air. Pressure recovery, which most never really understand of even know exists, also goes to hell with blown out chambers too. It's all a compromise. Bigger high flowing chamber with less quench area plus a very tight volume pop-up piston that kills the flamefront just to increase compression?.. or moderate dish with moderately sized chamber to arrive at some happy medium. Usually best to stick with well known and proven recipes and not overthink it too much since most compromises are built around the factory port locations and cylinder bore size anyways.
Okay that makes more sense.... The more of the angle, the closer the one side of the valve will be to the piston where if its not as angled, the valve can open farther due to less angel.... If I am thinking about this right being half asleep
Yep.. exactly right. By standing the valve up straighter with shallower angles it rotates the closest point of piston to valve contact to a "flatter" horizontal plane. Google shallow valve angle racing heads and you can easily see how the shallower valve angle really changes the combustion chambers final design shape as the amount of distance between the valves edge and piston improves enough that smaller piston valve reliefs may now be used. And most importantly, it deshrouds and points induction flow away from the cylinder wall and locates the valves more centrally within the bore. That's a nice side effect because smaller/much shallower valve reliefs means less flame front disturbance/fewer flow impediments, higher static compression capability, more piston crown thickness/mass(added durability), etc.. etc. Here's a link to the heads I have been "fiddling with" for my Comets future roadrace motor. http://mooregoodink.com/barmaid-piece-with-cutaways/ The next best "affordable" head I would be "fiddling with" would probably have to be Trick flows 11R head design. That heads chamber design follows the same trend as the valve angle is shallowed up from stock. Problem there is that they take a specific piston when you get into valve lifts much beyond .500" valve lifts. Always some tradeoff involved any way you go. Here's the P38 compared to another 20° aftermarket performance casting.
Well at least im starting to understand, from what I have learned recently, I kind of had it narrowed down to the following: Twisted Wedge® 11R 205 AFR 195 AFR 205 The AFR 205 According to Spec allow for an additional 0.11" of lift, But at the same time the AFR heads are at a 20 degree angel compared to the twisted being at 11 degrees with the same valve size but im thinking that's because they are 2ccs larger in the chamber which allow this... But with this build being na and going for more compression for power, the 56cc seems to lean more toward what I need.... I think.
Sounds like you already have the block and probably here nor there at this point.. but a big bore motor would have helped build compression without needing to work so hard building compression. Ideally you dump that kits uni-tard(4 relief) pistons off on ebay and get yourself some proper pistons with typical 5 or 6cc valve reliefs. That 11cc dish is killing you by about a full point of compression. The other thing you need to keep in mind is that the piston material used in the average cookie cutter stroker kit is going to be another power limiting factor. The 347 pistons typical 1.090" compression height is moving way down on the durability chart and standard more brittle forged 4032 material may not take the added heat of high rpm racing compression power levels over the long run. Sounds to me like you may want to be in 2618 alloy territory to gain temperature tolerance on those lower mass pistons. Otherwise you can only build as much power into the combo as the existing parts will allow. May need to rehone those cylinders for the looser running clearance 2618 alloy though. Then let's not forget you have weaker I-beam rods too. This proverbial snowball will get away from you if you're not careful. lol Have you installed the rotating assembly into the block yet? Here's a quick cookie cutter combo done thousands of times: easily nearing 525 horses @ 7,200 rpm.. maybe even more on Saturday and Sunday cruises! lol Current 347 CID shortblock combo.. BUT.. with NEW 5cc relief 2618 pistons will get you close to 11.5:1 static AFR205 Heads(competition ported version) flat milled to around 54cc's 8.2" deck height Super Victor Intake w/ 950cfm Holley 4150 double pumper Solid roller cam similar to: 248/254 @.050" nearing .700" lift(or slightly beyond) 1-3/4" primary/3" collector header with tuned collector extension dumps for the track 4.30 rear gear behind a moderately lightened unibody chassis = low 11/high 10 second time slips. Won't idle around town worth a damned.. but it'll be fast. Ooorr.. change the piston over to a 20+ cc dish(around 9.5:1), leave the head milling out of it,and squeeze the motor to make it think it's bigger than it really is. Less cash on valvetrain and easier on the entire drivetrain from an rpm related durability standpoint.
The rotating assembly has not been installed yet, nor has the block been worked yet. So By dropping lets say $500-600 on a set of pistons. Save the money from milling along with some for upgrading the springs and retainers which is about $400 alone on AFR's website. Sounds like it would come out cheaper (not worried about money so much) but also for the longevity of the motor/ rotating assembly and due to the fact of the I-Beam rods. The wisest decision sounds like going with dish piston, but at the same time wouldn't the dished piston while losing compression, also draw back its power? This is 95% race car 5% driven 1/8 mile up the road to work With only 1 red light to stop at if that... My 72 Maverick is going to be more of my driver that's just a basic build (rebuilt 302 with edelbrock estreet heads, F303 cam, performer intake and performer 650 carb)
What I meant when I said "squeeze it" was to open the dish even further to kill off some compression and supercharge or turbo it. Depending on boost levels.. 8.5:1 - 9.5:1 compression will keep peak cylinder pressures in check and help the motor live on moderate octane fuel. So, lower compression allows higher boost levels for greater net gains. Then your next weakest link will be those I beams. With a compression style race motor spinning some decent rpm you risk snapping the lighter i-beam around the little end during tension(sudden stop at TDC/end of the exhaust stroke). With a lower rpm but more heavily loaded piston(dependent on boost/power levels) you risk bending or breaking rods in the beam and big ends shoulder area during the power strokes rod compression phase. Quickly get into H beam territory if you really want to spin it or make bigger boost/more power. Now that we see a 95% drag car requirement to factor in here.. what power level do you want to reach? The other important question is how much do you want to spend on other supporting chassis, transmission and driveline components? That factors in too since 700 horse turbo motors usually don't stay running very long or go all that fast if they keep breaking all the supporting parts or spinning the tires too hard. The more power you make with the engine the more you'll need to spend on everything to make it survive the abuse. I've been exactly where you are many times, even on my latest build, and the best advice I can give is to figure out EXACTLY what you want out of this motor before you buy any more parts. Otherwise you end up losing some extra cash by selling off some of the parts that you already invested in when you finally figure out they don't fit into the newest engine plan requirements. IOW, don't hamstring your choices towards overall power or engine component choices just because you have x style pistons sitting there waiting to be used. If those pistons don't work or hold you back from the goal?.. sell them and buy some new ones that will do what you expect of them. Same with rods or any other key component. Remembr that an engines largest potential power gains are found above the deck.. and overall durability is found below.
I will share with you my 347 build. Stock 5.0 roller cam block .030 over Scat cast crank and scat I beam rods Probe forged pistols flat top 5cc valve relief Block milled to to have pistons .005 out of the hole. Out of the box 58cc AFR 195 cnc comp ported heads. Out of the box Edelbrock RPM air gap intake. Around 11:1 compression Custom FTI cam 210-215 psi cranking compression Out of the box 850 preform carb just adjusted for best idle. 1 3/4 long tube headers MSD ignition and distributor Timing set at 34* all in by 2500rpm Runs on pump 93 72 maverick 2940lb with me in it 4.30 gear, 28x9 slicks With a 4 speed toploader Launch at 3500 shift at 6250 1.44 60ft 1/8 mile 6.77 at 102.8mph With a c4 4300 stal converter Launch 2700 on a 2steep shift at 6100 1.41 60ft 1/8 mile 6.84 at 99mph Current converter is to loose on the top end
This car actually has had a back half welded in even tho its not a 4 link and is still running on the leaf spring. It has a 9" under it, it is set up as a 28 spline and currently has a twisted axle tho. I have not decided on a trans yet, car was a manual, but I was thinking about going an automatic. Front suspension is still stock. Ill see about getting some pictures up of what I have. Have to go to work now, ill elaborate a bit more in a little bit.
