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Old 10-06-2009, 05:29 PM
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Street 400 SBC (406) ideas

Okay, so I've got a 1970 C-10 with a 350 in it. Ideally, I think 350-400 horsepower would make me happy for a long time. The caveat, however, is that I'd like to achieve decent mileage and reliability, do it cheaply, and run it on 87 octane. For all of these reasons, I think a 400 is my best choice. I think a 375 horse 400 will be much easier to live with than a 350 making the same power. I'm not interested in building a 383.

My design goals call for a horsepower peak of arond 5000 rpm, with maximum rpm's of 5500, although I will be plenty happy if either of those numbers winds up lower. The only real trouble I've run into is that the selection of available, affordable pistons is limited, and, obviously, I need to keep the compression ratio in check to run 87 octane. So, here are two possible combos; I welcome all input.

Engine 1:
-0.030-over 400 block (4.155 bore)
-3.75 stroke stock crank
-5.565 stock rods
-Speed Pro 12.5 cc dish Hypereutectic pistons
-Edelbrock E-Street 70cc heads
-10.0:1 Static Compression
-0.045 quench distance
-Comp Magnum 270H installed straight-up (single pattern, 270 adv, 224 @ 0.050, 110 LSA, intake close @ 65* ABDC)
-7.9~8.0:1 Dynamic Compression (depending on calculator used)
-Edelbrock #7104 Performer RPM Q-Jet manifold
-QuadraJet carb
-1 5/8" Headers, 2.5" duals
-HEI


Engine 2:
-0.030-over 400 block (4.155 bore)
-3.75 stroke stock crank
-5.565 stock rods
-Federal Mogul 24 cc dish cast rebuilder pistons
-Edelbrock E-Street 70cc heads
-9.0:1 Static Compression
-0.045 quench distance
-Comp High Energy 268H installed 4* advanced (single pattern, 268 adv, 218 @ 0.050, 110 LSA, intake close @ 60* ABDC)
-7.2~7.5:1 Dynamic Compression (depending on calculator used)
-Edelbrock #7104 Performer RPM Q-Jet manifold
-QuadraJet carb
-1 5/8" Headers, 2.5" duals
-HEI


So, what do you guys think? I liked the Hyper pistons, with a smaller dish and more quench area, but it seemed like I would need more cam, installed straight-up, to keep the cylinder pressure in line, and this would probably negate most benefits from the higher compression... although, the cylinder pressure in #1 will still be higher. Will it run on 87 octane? Will it be happy at 1600 rpm on the highway with a 700R4 and long gears?

Which engine is better for my goals? Neither? What would you change, and why? Perhaps someone could crunch the numbers in a desktop dyno for me...

Last edited by benwantland; 10-06-2009 at 05:39 PM.
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Old 10-06-2009, 05:59 PM
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Quote:
Originally Posted by benwantland
Okay, so I've got a 1970 C-10 with a 350 in it. Ideally, I think 350-400 horsepower would make me happy for a long time. The caveat, however, is that I'd like to achieve decent mileage and reliability, do it cheaply, and run it on 87 octane. For all of these reasons, I think a 400 is my best choice. I think a 375 horse 400 will be much easier to live with than a 350 making the same power. I'm not interested in building a 383.

My design goals call for a horsepower peak of arond 5000 rpm, with maximum rpm's of 5500, although I will be plenty happy if either of those numbers winds up lower. The only real trouble I've run into is that the selection of available, affordable pistons is limited, and, obviously, I need to keep the compression ratio in check to run 87 octane. So, here are two possible combos; I welcome all input.

Engine 1:
-0.030-over 400 block (4.155 bore)
-3.75 stroke stock crank
-5.565 stock rods
-Speed Pro 12.5 cc dish Hypereutectic pistons
-Edelbrock E-Street 70cc heads
-10.0:1 Static Compression
-0.045 quench distance
-Comp Magnum 270H installed straight-up (single pattern, 270 adv, 224 @ 0.050, 110 LSA, intake close @ 65* ABDC)
-7.9~8.0:1 Dynamic Compression (depending on calculator used)
-Edelbrock #7104 Performer RPM Q-Jet manifold
-QuadraJet carb
-1 5/8" Headers, 2.5" duals
-HEI


Engine 2:
-0.030-over 400 block (4.155 bore)
-3.75 stroke stock crank
-5.565 stock rods
-Federal Mogul 24 cc dish cast rebuilder pistons
-Edelbrock E-Street 70cc heads
-9.0:1 Static Compression
-0.045 quench distance
-Comp High Energy 268H installed 4* advanced (single pattern, 268 adv, 218 @ 0.050, 110 LSA, intake close @ 60* ABDC)
-7.2~7.5:1 Dynamic Compression (depending on calculator used)
-Edelbrock #7104 Performer RPM Q-Jet manifold
-QuadraJet carb
-1 5/8" Headers, 2.5" duals
-HEI


So, what do you guys think? I liked the Hyper pistons, with a smaller dish and more quench area, but it seemed like I would need more cam, installed straight-up, to keep the cylinder pressure in line, and this would probably negate most benefits from the higher compression... although, the cylinder pressure in #1 will still be higher. Will it run on 87 octane? Will it be happy at 1600 rpm on the highway with a 700R4 and long gears?

Which engine is better for my goals? Neither? What would you change, and why? Perhaps someone could crunch the numbers in a desktop dyno for me...
Engine 1 with some tweeking!

Engine 2 does not have enough compression to take advantage of aluminum's greater rate of heat transfer to the cooling system. You want an engine that runs the dynamic compression into the 8 to 1 range, especially with aluminum. The lower the compression the higher the cost both in lost mileage and power. Aluminum easily will carry a full ratio or more against that of cast iron for the same octane fuel. With the modern fast burn chambers of the E-Street head, these should be happy with 87 unleaded. The 270 degree cam of engine 1 is probably unnecessary, the Comp 268 or better for your RPM goals the 262 would be fine. The 262 would bolster low to mid RPM torque and has surprisingly little loss of top end power against the 268. Longer rods would improve the mid range and make the engine even more tolerant of running at what is essentially lugging RPMs without getting into detonation.

Bogie
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Old 10-06-2009, 06:13 PM
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Originally Posted by oldbogie
Engine 1 with some tweeking!

Engine 2 does not have enough compression to take advantage of aluminum's greater rate of heat transfer to the cooling system. You want an engine that runs the dynamic compression into the 8 to 1 range, especially with aluminum. The lower the compression the higher the cost both in lost mileage and power. Aluminum easily will carry a full ratio or more against that of cast iron for the same octane fuel. With the modern fast burn chambers of the E-Street head, these should be happy with 87 unleaded. The 270 degree cam of engine 1 is probably unnecessary, the Comp 268 or better for your RPM goals the 262 would be fine. The 262 would bolster low to mid RPM torque and has surprisingly little loss of top end power against the 268. Longer rods would improve the mid range and make the engine even more tolerant of running at what is essentially lugging RPMs without getting into detonation.

Bogie
I can see that longer rods would have some advantages, but that's an expense I'm not going to add, and I like having a piston with a greater compression height, to avoid oil ring troubles, and to aid long term longevity.

I like the idea of a smaller cam, but I think I'll already have plenty of torque, and my rough calculations of the effects of a smaller and/or more advanced cam installation kind of scared me, due to the dynamic compression quickly looking unsuitable for 87 octane. Anyway, it's all food for thought. This build is a few months off; today was the first day I've really penciled anything out. Thanks for the input!
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Old 10-06-2009, 06:16 PM
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Bogie mades some great points and that 400 will like a lil more compression! and a longer rod!
Heres a few pics of my 406 going together

1970 400/406
4bolt srp studs
Internally balanced Scat 3.75 crank
Scat 6" rods
Mahle Forged flat tops with 2 valve releifs
7 quart pan melling select pump
Cloyes true billet double roller with torrington bearing
CSR billet pump
SFI dampner Billet Specialties pully
Lunati solid roller 243/249 @.050 595 " lift
Pro-Filer Aluminum heads 210 cc 2.05-1.60's
1.5 lunati roller rockers
PP Huricane ported to heads
750 Mighty Demon 1" Billet HVH 4 hole spacer
MSD Billet ignition components
Smooth runner fender well headers
3" Magnaflow exaust





Last edited by PRO 48 fleetline; 10-06-2009 at 06:28 PM.
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Old 10-06-2009, 09:20 PM
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Looks like a great engine, PRO, but your idea of a budget and mine are two completely different things.
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