Thread: I can't decide what engine to build....need advice

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408 SBC Low RPM Grunt motor. 415 HP, 475 FT/LBS. (For cruisin' and gettin' out of the way )
We're gonna use World Sportsman II heads on this motor, 'cause we've got 'em. They're not the best choice to make horsepower, but for a cruise motor and makin' torque, they ain't that bad. Thing is, they don't flow as well as some other heads you could use on this motor, so trying to prop them up with more static compression ratio and more cam to try to make a horsepower motor is fruitless. Better to optimize what you have to work with and make good torque, then use a gear to take advantage of it. I went to several sources to find some "real" flow figures for these heads. Brzezinski has flowed a bunch of 'em on a SF600 and averaged 'em out, so I went with their figures. I just don't trust figures from the manufacturer as much as I do from an independent company that has no axe to grind. On the DynoSim, these heads stall and nose over at 5000, so I optimized the cam to use this to advantage and make a torque motor out of it. By the way, I tried 11 different cams before I found the one I liked for this build. One of them made 460 ft/lbs at 2000 rpm's, but the hp was nothing to write home about.

Sportsman II flow figures from Brzezinski:
0.100" 64 60
0.200" 130 107
0.300" 186 126
0.400" 214 139
0.500" 230 147
0.600" 233 148

Block: 400 CID Chevy, casting 509, bored +0.040". In my opinion, it is detonation and/or rpm's that kills parts. With this build, I would be totally comfortable using the 2-bolt main caps as is. Nominal block deck height on a virgin block is +/- 9.025". The stack of parts used in this build is 9.008". Most available 400 gaskets will be around 0.040" compressed, so you would want to cut the block decks about 0.017" to zero deck to generate a 0.040" squish with a 0.040" gasket. Or you could cut the decks 0.012" for a piston deck height of 0.005" and use a 0.040" gasket for a squish of 0.045". Your choice. Measure very carefully before cutting anything.

Crank: 400 Chevy, 3.750"

Rods: 5.7" rod of your choice. Since this will be a low-rpm build, I might just use production 350 rods with ARP bolts and the big end re-sized and grind the head of the bolts for cam clearance. Scat I-beam capscrew rods will not have any clearance issues at the cam.

Pistons: 18cc D-Cup Hypereutectic, Keith Black #KB147+040, 1.433 compression height, 5/64, 5/64, 3/16 rings. If necessary grind rod bolt heads for .030" clearance at camshaft. Grind block at pan rail if .030" clearance is not present. Check stock rod balance pad-to-piston clearance, underside of piston. Pay careful attention to ring end gap information from KB. If I have to use a dish piston, I like the KB's because of the D-Cup configuration on the crown. It leaves a generous flat pad on the crown to mate up with the underside of the cylinder head to generate excellent squish.

Heads: World Products Sportsman II cast iron. 200cc intake runners, 72cc chambers, 2.02" intake valves, 1.60" exhaust valves. I suspect you could help these heads out considerably by doing a little bowl blending, precision 5-angle job on the seats and a couple of shallower cuts on the backsides of the valves. I don't know this for a fact, I'm just thinking out loud.

Intake manifold: Dual-plane, high-rise such as the Edelbrock RPM, Weiand Stealth or Professional Products Typhoon.

Carburetor: Vacuum-secondaries 650 CFM of your choice. This motor made a little more hp and torque with an 800, but the driveability (throttle response) and fuel mileage would probably discourage me from using it. If we used heads that flowed better, then yes, definitely I would use the 800.

Headers: Long-tube, equal-length headers of your choice. With this motor, it's a toss-up between 1 5/8 and 1 3/4 primary size. Use what you have. 1 1/2" long-tubes or shorties will be down 38 hp and 41 ft/lbs on this motor combination.

Rocker arms. I used 1.5 rockers for this build. It is said by some that you can pick up 15-20 hp by using full roller rockers over stamped steel ones because of the reduced friction. It is also said that full rollers will lower oil temperature and that makes sense to me. My DynoSim makes no distinction between them, so I can't change that part of the build. I figured you already have 1.5's, so I didn't want to spend any of your money. I did use 1.6's on the sim just to see what would happen. 1.6's will pick up 4 hp and 6 ft/lbs. Hardly worth the trouble and/or expense, taking into account the additional stress generated at the lobe/lifter interface.

Camshaft: CompCams solid, flat tappet, installed advanced 2 degrees. This motor with this cam (advanced 2 degrees) at this static compression ratio should run detonation-free on 87 octane swill as long as the motor is built with a 0.035" to 0.045" squish and the ignition timing is optimized. I might use a 2-piece front cover on this build so that I could try different offset bushings on the cam dowel pin, advancing it and retarding it to tweak the motor after I got a good feel for the baseline power. Some will say that if you have to advance or retard the cam, you've chosen the wrong cam. I don't agree with that. Usually, you can't find cams with only 2 to 4 degrees difference between them from the same manufacturer, so you use the cam that comes closest to what you want the motor to do and tweak it a couple degrees either way to get what you want. That's my take on it anyway. Use extreme caution on the valve springs with a flat tappet cam. You don't necessarily have to use a Comp cam, but you should talk with the tech guys at whatever grinder you choose to make absolutely certain you're using the correct valve springs on your heads for the cam used. The springs that Comp recommends for this cam are shown on this cam card.....
http://www.compcams.com/Cam_Specs/Ca...?csid=220&sb=0

Static compression ratio: 9.42:1
Dynamic compression ratio: 8.00:1

RPM HP TQ
2000 158 414
2500 198 417
3000 252 441
3500 312 468
4000 361 475
4500 394 460
5000 415 436
5500 371 454

I might be thinking of using a little taller gear with this motor than I would with another build that makes more hp at higher rpm's. 3000 r's with the 3.08 gear and a 28" tire makes 81 mph by my calculations. This would put the converter past stall and deliver 441 ft/lbs to the pinion. Oops, just went back and read that you have a 700R4. I believe the OD on that box is 0.7, is that right?