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Larry's Yellow Rdstr

Well-known member
Joined
Oct 19, 2002
Messages
304
Location
Redlands, Ca.
Corvette
05 black cpe-Porsche GT3
I recently had built a 383 stroker using a 350 block. I gave the car (El Camino) to my son. The car runs very hard.
I understand you can also do a 383 stroker or a 427 using a 400 block. I have never done any research on using the 400 block. My 87 vert has the 240HP 350. It runs great but has a few miles on it (104,000)

Any comments on the 400 block, or other options using a SBC as a base.
I would like to get 375 reliable HP from the engine. The car has a 700R4 trans and the Dana 36 rear.
 

Jack

Well-known member
Joined
Dec 27, 2000
Messages
1,825
Location
Florence, SC (Timmonsville SC)
Corvette
71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
Typical 383 is a +30 overbore 350 block w/ 3.75" stroke crank (aka 400).

Typical 377 is a +30 overbore 400 block w/ 3.48" stroke crank (aka 350). Requires purpose built, but off the shelf pistons.

400 was OE in some larger GM cars & light trucks from '70-'80. Good used 400 blocks are more difficult to find than 350. NOT recommended to overbore 400 beyond +40 ... 400 cylinder walls are relatively thin.

If you want 375 reliable HP from a 400 ... simply build a +30 overbore 400 w/ 6" aftermarket rods & aftermarket reverse dome (similar to dish) pistons & 64cc aftermarket Aluminum heads ... will make about 9.7:1 CR ... this 406" combo w/ a mild cam will easily make 375-400 HP ... & do it QUITE RELIABLY.

Aside from the cost of acquiring a GOOD 400 block ... cost to build long rod 400 v long rod 383 less about $100 more ... some bearings & gaskets different.

OE 400: deck height 9.025", stroke 3.75", nominal main journal 2.65", nominal rod journal 2.1", cylinder bore 4.125", rod length 5.565".

OE 350: deck height 9.025", stroke 3.48", nominal main journal 2.45", nominal rod journal 2.1", cylinder bore 4.000", rod length 5.700".

If you find a used 400 block that still has standard-bore pistons in it ... you can be pretty darn sure it'll need AT LEAST +20 overbore ... probably +30 to clean up ... suggest you pass on any that need to go more than +40. FYI most hi-po 400 pistons are NOT available in +20 ... most are +30, +40, +60.

OE 400: deck height 9.025", stroke 3.75", nominal main journal 2.65", nominal rod journal 2.1", cylinder bore 4.125", rod length 5.565".
OE 350: deck height 9.025", stroke 3.48", nominal main journal 2.45", nominal rod journal 2.1", cylinder bore 4.000", rod length 5.700".

If going to trouble of acquiring & prepping a good 400 block, why not build a 406 and take advantage of its high torque?
JACK:gap
 
M

MBDiagMan

Guest
The 406 is basically an over bored 400. The problem with the 400 is that the blocks are very prone to cracking. That, coupled with the fact that not many 400's were built to start with, is why the blocks are getting harder and harder to come by.

That's why the 383 is so popular. The 400 crank is okay and now there are plenty of aftermarket 3.75 stroke cranks. The 350 block does not have the siamesed bores and the cracking problems. So this has proven to be a very good marriage. Additionally as you build larger and larger cube SBC's you run out of breathing capability. The only way around this is with aftermarket heads, manifolds and such. That means that you pour in even MORE money.

If you are still bent on using a 4 1/8" bore block, I think that there might be some good aftermarket blocks if you are willing to part with that much cash.

Good luck,
 

ZumZum

Well-known member
Joined
Mar 25, 2004
Messages
478
Location
Central Illinois
Corvette
1988 Dark Red Coupe
Good info Jack. If I remember correctly, I believe I've read something about some steam jackets on the 400 block that are closed off and need to be opened up. I'm just going from memory, so could be wrong.
 
M

MBDiagMan

Guest
The steam holes are already in the 400 block. They must be drilled in the heads if they are not 400 heads.

This will ease, but not totally eliminate the cracking problems found with the 400 blocks.

Have a great day,
 

Jack

Well-known member
Joined
Dec 27, 2000
Messages
1,825
Location
Florence, SC (Timmonsville SC)
Corvette
71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
AFAIK the aftermarket 400 blocks also have siamesed cylinder liners cast in (aka jackets) ... siamesed liners in & of themselves are not a problem ... and no, you cannot open up the siamesed liners. OE 400 blocks have steam holes in top of decks ... mated to small steam holes drilled into heads ... usually necessary for street use ... a race-only car doesn't the holes drilled into heads. 400 is more sensitive to poor fan/radiator/cooling system maintenance than 350. But if all parts of system are in good & clean working order the 400 is not a problem. When they are allowed to overheat ... the block tends to crack around its steam holes. Otherwise, not a problem. Seems counterintuitive, but OE 4-bolt main 400 blocks are a bit weaker than OE 2-bolt 400 ... the OE 4-bolt 400 is a bit weaker in the main webbing and can crack if a lotta HP is put on it. Same NOT true in regard to 350 block. Good OE 400 blocks are available but not nearly so as 350.
JACK:gap
 
B

Black Bart

Guest
If you build a 406 DO NOT block the steam holes other than the large ones at the top and on them install a plug then drill 1/8 inch hole in them. Be sure to install the plugs before you have the block decked so it will not need decked again. The cracks that people talk about are at the large holes and the plugs will cure that. I have been running a 406 for the past five years at a power level that most would not believe with zero problems.
If you drive a good 406 just one time and you will throw rocks at your 350.
Find a good engine builder that has experience with them or if you are going to do it yourself spend some time searching the internet for info.
Their are several sites with detailed info and forums like this also.
But these forums have so many mythes being circulated that if you are not careful you will get some info that is worth just what you payed for it nothing.
The aftermarket blocks are much better but at the power level you are talking about a Gm production block will be fine. Their are blocks available for $100:00 bucks but hard to find. Some people will ask you $500'00 for one at that price you should consider a aftermarket block they run around $1800'00.
Horsepower is nothing more than a mathematical equation. A dyno can only measure torque and torque is what makes a car accelerate. The 406 is a torque monster you will love driving it.
Here is a site to get you started.
http://chevyhiperformance.com/techarticles/148_0306_406/
 

Larry's Yellow Rdstr

Well-known member
Joined
Oct 19, 2002
Messages
304
Location
Redlands, Ca.
Corvette
05 black cpe-Porsche GT3
Thanks Black Bart,
The 406 sound like an incredible engine. I had heard the term 406 Chevy but never had an idea of what they are capable of. My son tells me the 383 stroker I had built is scary fast 0-80 mph, if he can keep the back end of the El Camino planted. I should not have as much of that problem with the 406 Corvette. I can't fathom over 500 lb torque. My old Dana 36 rear end would have to be changed, and the trans built stronger.
Rather than looking for a good 400 block the Coast short block sound like a much better way to go.

Thanks again. Sounds like the beginning of a new project.

Jack, thank you too. I always read your posts.
 
B

Black Bart

Guest
Larry if you go with a 406 and have traction problems get a set of 11X17 rear wheels and Goodrich G-Force KD tires for the back. These are not as sticky as drag slicks but they will hook awful good and still give reasonable mileage.
I have them on mine and really like them.
With the supercharger plus nitrous my 406 put 917 lbs of torque to the rear wheels.
Everyone loves to hear a screamer but they don't last very long. For street driving a larger engine that makes a lot of torque at a lower rpm will run just as fast and last a lot longer. For your stated goals the 406 would be a perfect swap and it don't require any butchering of the frame or body component's. You can just drop it in and at a later date if you want to put the car back stock just pull the 406 and drop the 350 back in it.
Do a lot of searching their may be better alternatives than the builder on the site that I posted I just put that up to get you started.
If you are running a 700-r you should consider having it beefed up before dropping in the 406 but if you don't make a habit out of mashing on it you should get by for awhile. Good Luck and happy horsepower.
 

Larry's Yellow Rdstr

Well-known member
Joined
Oct 19, 2002
Messages
304
Location
Redlands, Ca.
Corvette
05 black cpe-Porsche GT3
Black Bart,
I just go off the phone with my son in northern Calif.. He knows an old machinist who has many Chevy engines Hes gonna check if the guy has an unbored 400. Slim chance, but you never know. He could'nt believe the numbers your 406 is putting out. I'll keep the board posted. My 87 has the 240 HP engine, so I'm used to blinding speed and neck snapping acceleration. LOL.
 
B

Black Bart

Guest
Larry's Yellow Rdstr said:
Black Bart,
I just go off the phone with my son in northern Calif.. He knows an old machinist who has many Chevy engines Hes gonna check if the guy has an unbored 400. Slim chance, but you never know. He could'nt believe the numbers your 406 is putting out. I'll keep the board posted. My 87 has the 240 HP engine, so I'm used to blinding speed and neck snapping acceleration. LOL.
You probably already know this but your mention of what is in the car now reminded me.You will have to replace the intake manifold. If you try to run that intake on the 406 you will have one hell of a good tow truck engine lots of low end and nothing upper end.
Here is lots of good info for you.
Spend some time here you will be better prepared to do this project.
You know knowledge is power.
www.rollingthunderz.com
Send this to your son he may like it. www.villagephotos.com/pubbrowse.asp?folder_id=1535340
 

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