Thread: 402

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So im looking for some more info, im sticking with building my 396/402 bbc engine. it will be bored out to 4.154 or 4.155, i plan on using Federal Mogul rebuild kit CSMHP716-611 from summit racing, it has Hypereutectic pistons with a -21.00cc dome and a 1.760 comp. distence, COMP Cams Xtreme Energy Retrofit Cam and Lifter Kit K11-413-8 which is 264/270 .510/.510, COMP Cams Magnum Rocker Arm and High Energy Pushrod Kit RPR205. I will be running stock 215 heads they have 98.4cc combustion chamber. So my question now is should i up size the valve size on the heads or leave them stock? Should i use Main and Head studs or just plan bolts? ARP of course. MSD Ignition system with a 6AL box. What size carb should i run? What intake is best? Will be running a 700r4 trans this will be a 4X4 truck running 33 inch tires and more and likely 3.73 gears. Im only looking for around 350-450 HP. Instead of the 500-500 i was before.

Thanks

If you were running 27" tires, the 3.73 gear would make sense. You are, however, running 33" tires and that will call for a gear around 4.56/4.88 or even shorter if you expect any acceleration at all.

I'd put hard exhaust seats in the heads an bolt 'em on. Larger valves will require opening up the ports and pretty soon, you'll have more money in them than you wanted to. If you want max flow, buy a set of aftermarket aluminum heads that are ready to go out of the box.

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Tech's on target as usual, with 33's and 3.73's you'll be doing only 1850rpm at 70 running down the road in OD, and your lower gears are going to be anemic. Going to 4.56's you're still only 2262rpm at 70mph, and with 4.88's you'll be turning 2421rpm. You need to look at how you want to use the truck, and pick your gears accordingly but that 700r4 has a 0.696 overdrive in it, so you can afford to go shorter on the gears and give yourself more pulling power, especially if you're wanting to off-road any.

Be careful with the idea of putting hard seats in any BBC cast iron head as the castings are especially thin around the exhaust valve on the end cylinder that would be for the #7 and #2 cylinder--------------stay with as small as possible seat od--------


And putting bigger valves in BBC means a bigger notch at the top of your cylinder for clearance

Originally Posted by 1972chevy

So im looking for some more info, im sticking with building my 396/402 bbc engine. it will be bored out to 4.154 or 4.155, i plan on using Federal Mogul rebuild kit CSMHP716-611 from summit racing, it has Hypereutectic pistons with a -21.00cc dome and a 1.760 comp. distence, COMP Cams Xtreme Energy Retrofit Cam and Lifter Kit K11-413-8 which is 264/270 .510/.510, COMP Cams Magnum Rocker Arm and High Energy Pushrod Kit RPR205. I will be running stock 215 heads they have 98.4cc combustion chamber. So my question now is should i up size the valve size on the heads or leave them stock? Should i use Main and Head studs or just plan bolts? ARP of course. MSD Ignition system with a 6AL box. What size carb should i run? What intake is best? Will be running a 700r4 trans this will be a 4X4 truck running 33 inch tires and more and likely 3.73 gears. Im only looking for around 350-450 HP. Instead of the 500-500 i was before.

Thanks

new head bolts and the stock main cap bolts are fine you can go to 2.190 and 1880 and not do any thing to the deck for cutting and go to a 2.250 intake valve and just clean up the stock eye brows in the deck check the valve relief in the piston but in the small chamber heads may not help you gain much if a lower lift cam with out any work . this is were i go in with the seat and guide machine and profile the chamber for the bigger valves and i go in to the bowls were the cutter.s i use form the 15.30.45.65.70. and on ex side a full radius with a 45 then to 70 after that just some clean up with sanding rolls to drop in the bowl of the head and open up a head for bigger valve i do not charge much more then a valve job is it can go fast with the tobin arp/sunne machine a good set of stainless steel valves 2.065.and 1.720 like PeP jet flow or a back cut stemed down and a nail head ex valve should be ok .if heads have had many valve jobs moving up to a 1800.ex and a 2.190 intake intake side will help put the valve back in the head chamber height and going to a 11/32 valve stem helps flow some . ex side you can put in hard seats your machine shop should know. but like jerry said i only cover the 45 on the Ex on some heads . i use 1 15/16 ex seat if you go to 2.000 bad things can happen on the ex side of the head could go smaller then 1 15/16 if using the stock valve or a 1.800 then you could get away with a 1 7/8 seat
. many 454 s had 215 o port heads on them fast way to get CR they can be made to work very good . cam watch what year of 396 if you have one. and not a 402 any thing pre 1967 will need number #5 cam journal to be grooved if you want oil to the lifters and top end of engine