406 Stroker help

[slammed71]

First off i'd like to say this site is awesome! Now for my question, i'm wanting to build a 406 stroker motor. I tore down the 400 i bought yesterday and it's already got 5.7" rods in it. So does this mean all I have to do to make it a 406 stroker is bore it 0.30 over? Now I know alot of guy's are going to say replace the rod's with some H-beam's or atleast some new I-beam's but i'm not building a race motor. Now granted I want some pep don't get me wrong. As long as the stock rod's are good shape wouldn't they be good for 400-450 h.p or would you without a doubt replace them...? If i'm not mistaken a 400 came with either 5.7" or 6.0" rods, correct? Thanks for the input guy's!

[Scott Norris]

A 406 is just a .030 400,Not a stroker.400 came with 5.65" rods not 5.7"

[slammed71]

Ok, so what do I have to do to make it a "Stroker".....?

[Billla]

Originally Posted by slammed71

Ok, so what do I have to do to make it a "Stroker".....?

Not to be a smarta%%, but increase the stroke ;-) The stock stroke is 3.75, aftermarket cranks are available up and past 4.125. It's just a matter of $$$.

Why do you want a "Stroker" if you already have 400 CID? The price starts going up geometrically at this point for SBC.

[special-K]

The 400 is a stroked 350.To stroke a 350,you put a 400 crank in it.You have what you need now,the torquey small block.

[dirtball]

Originally Posted by special-K

The 400 is a stroked 350.To stroke a 350,you put a 400 crank in it.You have what you need now,the torquey small block.

+ 1/8" more bore, so you have a bored stroker
I agree, what you have is great. Not sure why everyone feels they have to have a "stroker motor". Maybe the stroker name adds power just like chrome valve covers and gear drives

[special-K]

I was going to say,"+some boring".But,to keep it simple it`s the same block(after boring a 350)with a longer stroke crank.Then there`s the opposite...the 355.A quick-revver with more bore.

[dirtball]

Originally Posted by special-K

I was going to say,"+some boring".But,to keep it simple it`s the same block(after boring a 350)with a longer stroke crank.

Tim
I knew that you know this. I didn't know if others knew it. So I thought I would try to eliminate confusion, know what I mean? Wait.......what

[67chevy2wd]

I was thinking about this the other day, if a 400 is a stroked 350 with a larger bore why do people build a 383. Does a 383 rev up faster because of the smaller bore. I just didn't understand the point.

[bigjimzlll]

A 350 block will not take a .125 over bore. The 400 block is a special block. The reason for 383's is because there a lot more 350 blocks out there.

On the original post...are you sure they are 5.7 rods?

[68Stepbed]

350: 4.000 bore/3.48 stroke
383: 4.030 bore/3.75 stroke- 350 block stroked
400: 4.125 bore/3.75 stroke
377: 4.125 bore/3.48 stroke- 400 block destroked
415: 4.155 bore/3.875 stroke- 400 block stroked
427: 4.125 bore/4.00 stroke- 400 block stroked
434: 4.155 bore/4.00 stroke- 400 block stroked
454: 4.155 bore/4.25 stroke- 400 block stroked alot!

Hope this helps.

[watahyahknow]

i remember sumtin bout the steamholes in a 400 block cant realy remember though

[68GenIII]

The 400 block has larger mains then the 350. It also has the steam ports on the deck.

[ABHaulR]

the 383 is a 350 bored with a 400 crank and 5.7 rods
the 400 uses a longer stroke but a shorter rod(not a stroker)just more cubes
the 377 uses a 400 block 5.65 rods and a 350 crank.(high rmps)
Dwayne

[67chevy2wd]

This might be a dumb question but does a longer stroke = more torque lower RPM's and a shorter stroker = less torque but higher RPM's?

[watahyahknow]

seems that way : the shorter stroke pushes down with more power on the piston (bigger surface ) but has little leverage from the stroke the longer stroke has less power on the piston (smaller surface ) and more leverage from the stroke .
and theres the reprociating weight of the crank rods and pistons , compare the stroke of the crank to a weight on a string keep the string short and spin it around and the weight feel light and you can spin it fast make the string longer and it will feel heavier and more sluggish

[67chevy2wd]

That's what I thought, so then a person would be better of building a 400 rather than a 383? You would have the same stroke but a larger bore.

[57sailplane]

hey guys

the reason more people build a 383 sbc is yes one 350s are more comon.. also the 350 is a stronger block. In a 400 cid the area between the cylenders in the block is ultra thin and to keep this area from melting down GM added two small steam holes or coolant holes at the top of the block to keep coolant sirculating close to the thin area.. thus the 400s are prone to cracking.. but a well preped 400 will handle lots of hp.. keeping it cool is key.. if you build the 400 use a 4 core or aluminum radiator and a good flowing aftermarket waterpump.. you cant go wrong with cubes..

oh and makes sure you get the block checked for cracks, magnafluxed.. you don't want to spend a lot of money on a posible cracked block

[8696steve]

400's are prone to over heating, a 383 would be the best route in my opinion, but you already have a 400, rebuild it if it needs it. Maybe add a bigger cam, carburetor and do some head work. if you have the money buy a nice set of heads. A 400 is not considered a storker motor, only if you put a bigger crank in the 400.

[SCOTI]

Originally Posted by 8696steve

400's are prone to over heating....

Only when treated like any ol' small block vs. treating them like a larger engine (which they are).

Get the cooling system up to snuff & do the steam holes in the heads. The biggest benefit of 400's is they unshroud the valves because of the larger bores while still using standard sbc brackets & hardware.

[watahyahknow]

theres a book on the market from SA : how to build big inch chevy smallblocks there should be some resepies in there for a 400 block and its a recent book.
and the one from billy "grumpy"jenkins (i believe) has a lot of info on the 400 buildup its an older book but i think the ideas for the machining and stuff are still up to date

[slammed71]

bigjimz,

I measured from the center where the piston is pressed on, to the end where the rod cap sit's and it looked like 5.7" to me. Is this strange...? I thought that's the size rod they came with..? I'm new to building my own motor's so be patient with me, doing it is the only way to learn IMO. Thanks for all the great info guy's keep it coming!

[bigjimzlll]

Slammed, The 400 sbc came with shorter rods. They are 5.565" not 5.7". What is the casting number on your block? Are you sure it's a 400? It's real easy to miss .135" with a tape measure...specially measureing at an angle, so the rods could be 5.565 not 5.7

[slammed71]

That is very possible I just measured wrong because I did check the casting numbers which tells me it is a 400. Stock 400 rods are 5.565" but every replacement rod I see is 5.7" or 6.00". If I put a 6.00" rod in it will I have to notch the block anywhere....? I thought someone told me that one time? Would I be able to tell a big difference in power if I used a 6.00" rod which would make it a "Stroker"?

[67chevy2wd]

If you increase the rod length don't you have to shorten the length of the stroke won't the piston hit the head. I was always under the impression too that a stroker had a longer stroke than normal. Like a 350 to a 383 longer stroke and shorter rods. IDK I have always been confused with the stuff not enough experince