383 or 406 sbc

[Trev1981]

i want to build a new motor for my 1984 Blazer i can't make up my mind if i want to do a 383 or a 406, i have to keep all the smogstuff on it so the cam and carb will be mild. What do you think?

[KWTMECH]

You have access to a good 400 block?

[Trev1981]

i have a few leads, one guy wants $500 for a std bore

[Wheel28]

Originally Posted by Trev1981

i have a few leads, one guy wants $500 for a std bore

Is $500 the going rate in Cali? If so ouch! Here in Tx I wouldn't give more than $150 for a 400 block and usually pay less. Imho go with 406 you can't beat cubic inches, but a 383 is usually easier to build. A 350 block is easier to find and the 383 crank kit is not to bad pricewise.
Will

[mj]

406

[bowtied_micky]

without a doubt go 406. goto the bookstore and find a book called building big inch chevy small blocks. In the back they build a very mild 406 with vortec heads and it gets in 500s for tq and the 400 for hp. They show dyno sheets.

micky

and 500 bucks for a 400 block? that has to hurt, I can get them from my machine shop for 250 and they have been checked.

[44boggers]

a 383 is no easy to build than a 400, i runa 383 witha truck avenger carb and it kicks ass, i push 460 ft lbs and 450 hp, why are you keeping all the smog equiptment?? oh i see cali. anyways you can find some nice stoker packages for a 350 which will give you some good power

[BenDover282]

ya im in cali so the smog stuff must stay but i might be moving to Montana and if i do the smog stuff will come off and a EFI kit will be going on

[BenDover282]

sorry i posted at my friends house (trev1981)

[cj8scrambld]

I like the 400's....they can make gobs of TQ. Hell, that is why they were produced in the first place.

[4x4koko]

406

[trkklr77]

383, any 350 block
still is a 400 crank
any head without moding it
stronger cylinders

406, any head can be used BUT you have to drill steam holes in them!!!!
not as common block
will over heat like a m/f if not cooled excesively.

[odin544]

Originally Posted by trkklr77

will over heat like a m/f if not cooled excesively.

BS. it wont over heat anymore than any motor that has an insufficient cooling system. they have a bad rap for overheating because of morons not drilling steam holes in the heads and such.

[44boggers]

everyone has a 400, stroke it man. 383

[bowtied_micky]

the only reason a 406 overheats is people not drilling the necessary steam holes in the heads. If those holes are drilled there will be no problems with heat..

micky

[2manyprojects]

400 block, 350 stroke crank . Use long rods and let it bark. Builds more power and torque with the longer rods than the 350 block and 400 crank. Last's longer with less side loading of the pistions.

[4x401cj]

Originally Posted by bowtied_micky

the only reason a 406 overheats is people not drilling the necessary steam holes in the heads. If those holes are drilled there will be no problems with heat..

micky

Where exactly do the holes get drilled?

[Rock Ape]

The 383s i have built never made the power a comparable 406 did!!!!I am in the process of building a 406 with 6.0 rods right now for a street rod project!!!!I cant wait!!!!Go big!!!!

[cj8scrambld]

I would go 400 long rod as well. As far as making more power, it does/can but I think it is marginal. Long rod motors are less sensitive to detonation as it offers a longer dwell time.....again as with the long vs. short rods there are other factors that play into that. I like the 400 because of it's significantly larger bore, it can make any head flow better due to unshrouding the valves by the nature of the larger bore. I would think 350/400 built comparably, the 400 would offer more downward push on the piston (comp ratio being equal) due to the larger surface area. Go 406, you won't be dissapointed.

[trkklr77]

Originally Posted by 2manyprojects

400 block, 350 stroke crank . Use long rods and let it bark. Builds more power and torque with the longer rods than the 350 block and 400 crank. Last's longer with less side loading of the pistions.

377's are a race high rpm motor for dirt track type stuff, where the rpms stay high and dont need to low end grunt much. still a good combo but the 383/406 will out pull it any day from the line.

[trkklr77]

Originally Posted by 4x401cj

Where exactly do the holes get drilled?

they are between the cylinders at the narowwest point top and bottom.

[axisT6]

Uh, not to hijack. I am in the process of building a 406, and when the block was prepped, the steamholes were plugged. Will I have a heat problem?

[odin544]

Originally Posted by axisT6

Uh, not to hijack. I am in the process of building a 406, and when the block was prepped, the steamholes were plugged. Will I have a heat problem?

yes more than likely you will.


any competent machine shop can drill the holes for you.


from AFR's website:
400 BLOCKS:
Steam holes are recommended for all 400 block applications (GM blocks only). Use a 400 Gasket as a template and drill the three holes, nearest the spark plug side of the head, straight down. The other three which are very near the head bolt holes should be drilled at a 30° angle away from the bolt hole. The center hole will intersect water about 1" down and the two outboard holes to a depth of 2 1/4". Use 1/8 drill.

[trkklr77]

Originally Posted by axisT6

Uh, not to hijack. I am in the process of building a 406, and when the block was prepped, the steamholes were plugged. Will I have a heat problem?

yes, there is no water flow between the cylinders without them!!!!!!

350 and small sbc use a seperate tube to make each cylider wall, the 400 all of the cylinders are connected together "siamiesed"