Sounds like you have all the bases covered now it just looks like getting heads with a good set of roller rocker arms and a cam that will set all those parts in motion some hardened push rods and a hardened oil pump drive shaft and your off to the races. I run 2 1/2" exhaust but it dumps before the rear end. When you get it going down the track you might want to try disconnecting your front sway bar for a little extra weight transfer
Any well designed heads will make good power on that combo. No need to get crazy with port sizing if you're running a dual plane that will cause higher rpm flow loss. Just depends on the cam and how high you want to spin it. Also keep in mind that dual planes in unported form will not be the best choice for N2O usage because they have minor fuel distribution issues in as cast form. N2O just makes it worse. With a plate system you'd want to add another open spacer to help out in that regard. Might not fit under the hood at that point though. Try to keep chamber size a bit smaller in the sub 60cc range(no larger than 58cc or so to hit a true 10.5:1 SCR) or you'll kill a bit of needed compression ratio that any healthier cam will prefer. The dual plane can save you some there.. but not completely. Have you researched the various heads and looked at the designs? Anything in the premium castings will be more than adequate for most. Nice thing about the AFR's is the smaller diameter/lighter weight LS style valves.. but you can do that to any head with the added cost of guide liners. I converted my RHS 165's to LS style valvetrain relatively cheaply and Trick flow is using them on some of their castings as well. Beehive springs are also a worthwhile upgrade if you want to spin the motor higher too. Oh yeah.. forgot. I'm with Mike here. 2.5" mandrel bent piping is more than adequate for this level build. 3" wouldn;t be advisable because this motor won;t be making over 450 horsepower and you'll kill some throttle response and torque just to gain a few more ponies up top. In that case the dual plane will snuff it out anyways. Not worth it at all on a smaller motor running pump fuel compression. N20 would love it.. but this ain't built to be a bottle baby all the time anyways.
Glad to see that some of my thinking is aligned with yalls. I knew the dual plane would hurt top end, but I don't intend to keep it WOT all of the time anyway. I've been thinking that 58cc chambers would be best, with less than a 200cc runner. My only reasoning for the 200 runner is that most as cast won't flow that much volume anyway. 185 or 190 would be ideal I guess? What valve train and what cam specs would y'all recommend? I really am thinking of not spinning much over 6500 to be conservative. I don't think I'll need to push it much harder to enjoy it, lol. What times are you guys seeing similar setups run? I'm not bench racing, just curious. I'd like to run somewhere in the 11's. 12's were my goal before but I think I can squeeze a little more out if I play my cards right. Thanks for the tip on the sway bar.
If it were me, I would choose a 185-190 AFR or TFS 11R as has been suggested. I can't think of two better choices for the $$$. Both will pull our cars easily into the 11's with the right set up, even with a 302. IMO, headers are a big problem on these cars. The Hooker 6901 was not designed for the Maverick/Comet (that's my story and I'm sticking by it). Opinions vary on the fit. Some say they fit perfectly while others have to hammer the @#$% out of them, either out of necessity or plain old rage. They do have port sizes that are close to matching the larger TFS or AFR exhausts, however. The Hedman long tubes fit much better, but were designed for the smaller OEM exhaust ports. Modern high flowing aluminum heads were but a dream when the Maverick/Comet headers first came to market.
1& 3/4 tubes with at least 2in pipes if you can make them fit,3in collector.1& 5/8 tubes might be OK if you don`t spin over 7500.
Even if you could squeeze 1.75" primary pipes in that bay.. why would you need them on a 331 CID street compression moderately cammed build like this? Too big a primary on a smaller short stroke moderate compression motor kills exhaust velocity and blowdown length.. and then you're forced to run a merge style collector with a smaller choke id just to create a large enough depression to pick that too big primary back up and reduce reversion level to where they would have/should have been with a smaller and correctly sized primary that was better sized to the motors spec's in the first place. What many don't realize is that a 1.625" diameter pipe(depending of course on layout.. length and # of bends and radii severity) can handle about 70 horsepower PER cylinder of exhaust flow. Not to mention that it creates a much better transitional matchup to the head. Intentional or header mfgr forced port to flange mismatches may help create anti-reversion dams for mismatched and old-school parts with less than optimum cam choice.. but not preferred by top builders for optimum flow out of the heads exhaust port with the much better parts/cam combo's we have to work with these days. Horsepower to horsepower for another similarly powered larger stroke/CID motor.. shorter stroke/smaller CID engines will tax the headers less below peak power and usually prefer smaller primary and collector sizes to improve gas velocity(reduces combustion chamber/manifold reversion and also aids scavenging effect)/average power production/overall fatter powerband. Especially important for street cars that spend most of their time below peak power and helps shift drop/rpm recovery to improve ET's when you want them.
Check with bb466,he will tell you how to get Hooker 6208 supercomps in this body.He ran them on his last combo,a 408,went 9.80s n/a,they are what I am going to use on my 410.
