406 Stroker help

[SB406]

A smallblock 400 has the same external dimensions as a 350 and a 305. However, it basically has 396 pistons in it, forcing GM to make 'siamese cylinders' meaning that there's no cooling jacket between cylinder walls. There are extra steam holes, so if you use 350 or 305 heads, you will need to get the steam holes added to the heads. Also, make sure that you use head gaskets for a 400, and NOT a 350.
I've NEVER had a problem with my 400 overheating. But, like stated above, I have a good radiator, a large fan, and a good water pump.

[watahyahknow]

the longer 6 inch rods are made to get the sideway pressure from the skirt of the piston to the cylinderwall down and to keep the piston futher up inside the cylinder on shorter strokes and away from the counterweights of the crank on longer strokes they usually need special pistons wish has the small end hole closer to the top

try and find someone who has a stash of old hot rod magazines and start reading those , they have an enourmous amount of tests comparing the different options and info in them .

[bigjimzlll]

If you use a 5.7 or 6" rod it will take a different piston. With the longer rod the pin is raised in the piston. The advantage of a longer rod is that the piston will be lighter(good thing) and there will be less side loading on the cylinder wall(longevety). It does not change the "stroke" so it will not be a stroker.

The problem with a 6" rod is the pin is in the way of the oil ring. It takes a support to go across the pin hole. No big deal...but it is troublesome to some.

I would go with a 5.7" eagle or scat rod(175 bucks). These are good pieces and by the time you rebuild stock rods with good bolts you have almost that much into them and they are 30 year old forgings.

[slammed71]

I got it, i'm an idiot but the way to learn is to ask....! So let me rephrase that last question. If I were to put a 4.00" crankshaft would I be able to tell much of a difference in power? Thanks for your help guy's!!

[bigjimzlll]

Originally Posted by slammed71

I got it, i'm an idiot but the way to learn is to ask....! So let me rephrase that last question. If I were to put a 4.00" crankshaft would I be able to tell much of a difference in power? Thanks for your help guy's!!

Lets just say....yes...but I would not do it in a stock GM block. Also to really maximise the power you would need very big heads.

I run a 406 in my truck (.030 overbore) and it has all of the power you would need.
check out this video of my truck..(caution..there is some swearing at the end)

Click here to watch in-caragainst-cop-car


I would stay with a 3.75 stroke, 5.7" rods and depending on your heads a piston that will give you between 9.5-10.5-1 compression ratio

[Billla]

Originally Posted by slammed71

I got it, i'm an idiot but the way to learn is to ask....! So let me rephrase that last question. If I were to put a 4.00" crankshaft would I be able to tell much of a difference in power? Thanks for your help guy's!!

It's always a learning curve There's a lot of information coming at you on this thread. The bottom line is that strokers add CID, and CID = +HP, +TQ. The bore/stroke ratio and rod length also play a part in this, but IMHO to a minimal degree in engines making <= 1 HP/CID FWHP. The more you stroke, the more expensive it becomes - and the more radical (read: expensive and unstreetable) the engine becomes.

A 4.00" stroke and 4.125" bore gives ~427 CID. For a street engine that means maybe ~30 HP or 30 ft-lbs TQ; more if you're making over 1.5 HP/CID. IMHO, not worth it at all - if you're looking for more than 400 CID of displacement a BBC is an easier and not that much more expensive swap.

[slammed71]

That's bad@$$!! What do you have done to yours?

[watahyahknow]

Originally Posted by bigjimzlll

Click here to watch in-caragainst-cop-car


I would stay with a 3.75 stroke, 5.7" rods and depending on your heads a piston that will give you between 9.5-10.5-1 compression ratio

thats one healty sounding engine think the .30 over would indeed be the best idea .

did you use the stock cast crank in that motor big?

[bigjimzlll]

The 406 I have is as follows:
gm 400 block with splayed main caps
eagle 4340 3.75 crank
eagle 6" H beam rods
wiseco flat top forged pistons
54cc CFM 210 cc intake aluminum heads
12.5-1 CR
comp solid roller cam shaft
super vic intake
custom 950HP holley
I figure it makes right at 580 HP. I have a 5200 rpm ATI converter thru a th400 with a trans brake. To a ford 9" with 4.86 gears

[57sailplane]

ttt

[ABHaulR]

you can increase the rod lenght, but you need to check the deck height
so as to not cause the piston to valve damage. you can get pistons in
different pin locations for rod lenght, compression, stroke. you need to
check all before you decide to build an engine.
Dwayne

[ADay73]

I have a stock 400 sbc that I am actually now looking into having rebuilt/built to a 406. How much should I putaway for this to be done? I have never had an engine rebuilt and am not sure how much it may cost.

[Billla]

Originally Posted by ADay73

I have a stock 400 sbc that I am actually now looking into having rebuilt/built to a 406. How much should I putaway for this to be done? I have never had an engine rebuilt and am not sure how much it may cost.

It all depends on what you find during teardown. Are you rebuilding it yourself or having it rebuilt?

If you're doing it yourself, staying primarily stock and all the key parts are reusable a basic overhaul is around $1500 but a better budget is $2500 as it leaves some room for a few upgrades. Taking it beyond stock leaves the budget completely open - it's not hard to spend $10K+ more on a hot build. Decide on what you have for a budget and work backwards - always.

Same thing if you're having it rebuilt - decide on what you want for HP/TQ and budget and have that number ready when you talk to the shop. You can't always get what you WANT with a fixed budget, but you will end up with better matched components. I always wince when I see someone that spends a ton of money on the shortblock and then run out of money and choke the whole thing with lousy heads, intake and carb...or have zero dollars for a quality tune after installation.

[Billla]

Originally Posted by bigjimzlll

I figure it makes right at 580 HP

That is a serious racing beast Pictures?

I know this is always a hard question and ignore if you don't want to answer, but what kind of $$$ did it take to get to almost 1.5 HP/CID? I'm guessing that's a $12-$15K engine...

[bigjimzlll]

Originally Posted by Billla

That is a serious racing beast Pictures?

I know this is always a hard question and ignore if you don't want to answer, but what kind of $$$ did it take to get to almost 1.5 HP/CID? I'm guessing that's a $12-$15K engine...

I guesstimate 7500.00. There is no way I would sit down and figure it out though.....my heart and all...
heres a tire spinning 10.99 pass

Click here to watch spinning-1099-pass

Theres some pics here
http://imagehost.bizhat.com/gallery.php?id=9385

http://imagehost.bizhat.com/gallery.php?id=12678