383 vs 400 sbc
Thread Starter
Racer
Joined: Oct 2011
Posts: 318
Likes: 3
From: NP Nebraska
383 vs 400 sbc
I built a 383 with hydraulic lifters, flat tappet cam, and vortec heads last fall. I did it on a limited budget so it is by no means a high performance engine but it was a definite improvement over the crate 350 that the PO had in it. I am thinking about replacing the tranny and rear diff to have an overdrive with a little more boost off the line (I have the TH350 and 3.07 rear).
I have the opportunity to buy a sbc 400 and build it now that I have a little more in the budget. What are the limits to the 350 block vs the 400 block when building a moderate street build (say $3-5000 budget)? I have heard some bad things about the 400 block regarding cooling, etc. Will the 400 mount with the 700r4 or 200r4 as well as the 350 is supposed to? Obviously I have looked at the various engines at Jegs and Summit but I would like to do it myself. Any serious roadblocks for the shade tree builder with the 400?
I have the opportunity to buy a sbc 400 and build it now that I have a little more in the budget. What are the limits to the 350 block vs the 400 block when building a moderate street build (say $3-5000 budget)? I have heard some bad things about the 400 block regarding cooling, etc. Will the 400 mount with the 700r4 or 200r4 as well as the 350 is supposed to? Obviously I have looked at the various engines at Jegs and Summit but I would like to do it myself. Any serious roadblocks for the shade tree builder with the 400?
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
A 4bolt main 400 block is as stout as a 4 bolt main 350- difference is the main bearing diameter and steam holes in the deck between the cylinders. The siamesed cylinders can develop hot spots at the top of the cylinder between the bores. Since the bores touch, no way for coolant to circulate. THe steam holes allow coolant to flow into the heads (they also have to be either 400 specific or drilled. You can drill them by using a 400 head gasket as a template. No trick there. The other difference is the 400 is externally balanced- there is an additional weight on both the balancer and the flywheel/flexplate. There is an available plate you can install between the crank and flywheel/flexplate that allows you to use the 350 parts, other than the balancer. Or have it internally balanced.
Your second question- if a trans fits a 350, it'll fit a 400
I know a guy that has all of the internals for a 400 for sale- he used a 400 block and is going to some "way-out-there" cubic inch SBC.
Your second question- if a trans fits a 350, it'll fit a 400
I know a guy that has all of the internals for a 400 for sale- he used a 400 block and is going to some "way-out-there" cubic inch SBC.
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
There isnt a whole lot of webbing material in the 400. Flip the blocks over sometime and compare.
Unless youre spinning the 400 way up there you should be fine with a 2 or bolt main 400. They can make a reliable 450-500hp
They make tons of torque everywhere youll notice it over your 383.
Have a 509 block in the garage one day Ill put together
Keep it under 6, 6200 and they can live along life.
Some put much more to them some last some dont.
Unless youre spinning the 400 way up there you should be fine with a 2 or bolt main 400. They can make a reliable 450-500hp
They make tons of torque everywhere youll notice it over your 383.
Have a 509 block in the garage one day Ill put together
Keep it under 6, 6200 and they can live along life.
Some put much more to them some last some dont.
Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
If you've already got a 383, really not seeing much difference going to a 400. As with any build, really a combination of the right parts, head work, and how the whole package is dialed in. Know a couple guys running 406's, and can't say I'm at all impressed. Knew a guy with a 406 in a 71' Camaro, and that thing flat out flew though, easily revving to 7000 rpm. Don't know what he did in the build, but did something right. Don't think I'd be to worried about the siamesed bore, as currently have an LS7 car, and ain't no one going to say this ones slow. Think I'd stay with what you've got, with maybe some head work. With the rear you have, think you're on the right track with a 700R4 tranny. As you already know, 3.05 1st gear, and probably about 2000 rpm on the highway in 4th lock up. Done these on a few cars, and well worth the trouble.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
TQ is a direct math function of cubic inches. So Pauldana's 383 topped out at 430 foot pounds. The equivolent build on a 400 or 406 ci would be 460 to 470 foot pounds.
People have been hot rodding the 400 small block for over 40 years.
People have been hot rodding the 400 small block for over 40 years.
Drifting
Joined: Dec 2005
Posts: 1,360
Likes: 3
From: NORTHEAST
Not very fond of the 400 SBC they seem to be a problem child over a 350 block because the 400 has weaker decks, weaker cylinder wall near the bolt holes weaker webbing do the bigger bores.
Here is a link to a guy that was working on a junk 400 block and he was wrned what the out come was going to be. He sure wasted alot of money and time.
http://www.stevesnovasite.com/forums...d.php?t=185248
Here is a link to a 383 I built which developed 501 ft lbs of torque.
http://www.chevelles.com/forums/showthread.php?t=106715
Here is a link to a guy that was working on a junk 400 block and he was wrned what the out come was going to be. He sure wasted alot of money and time.
http://www.stevesnovasite.com/forums...d.php?t=185248
Here is a link to a 383 I built which developed 501 ft lbs of torque.
http://www.chevelles.com/forums/showthread.php?t=106715
Drifting
Joined: Jun 2010
Posts: 1,781
Likes: 15
From: Oxford Ohio
Don't be concerned with the heat at the center bores. You can plumb fresh water directly from the water pump to between those cylinders. Tap and thread the casting hole boss in the center of the side block wall, (a few have the plug hole there instead of the boss, then weld a bung in the plug for that hole)you can buy from Jegs or Summit a threaded spacer to go under your water pump. Plumb the fresh water from there.
Le Mans Master
Joined: Oct 2010
Posts: 6,930
Likes: 842
From: melbourne florida
2023 C3 of the Year Finalist - Modified
my only issue with either motor is rod angle. both motors need a longer connecting rod. i think a 5.85 rod in a 383 works out pretty well maybe a 6 inch in a 400. without a good rod angle your bore wear will be more rapid and you will leave some power on the table. i wouldn't worry about using a 400 the cooling issues are easy to deal with
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Burning Brakes
Joined: Jun 2008
Posts: 1,086
Likes: 1
From: Michigan
I had a 400 in a '77 Vette I owned decades ago. The thing I remember is what was mentioned already about the cooling holes in the 400 between the cylinders. Be sure the gasket and heads you use have all the holes that match the block.
I was very impressed with the torque numbers the car had and I regularly chirped the tires in second gear with an automatic TH350 that was in the car.
I was very impressed with the torque numbers the car had and I regularly chirped the tires in second gear with an automatic TH350 that was in the car.
Instructor
Joined: Dec 2011
Posts: 142
Likes: 0
From: Tucson Az
Ive had several 400's all with stock blocks, 2 bolts are strong enough for a street engine my current one is 406" makes 500ft lbs on pump gas and is a 2 bolt.I built a 421" way back in 1995 with 14:1 compression big roller cam etc ,shifting at 7000 rpm, a friend has it now and it still runs fine. I never had cooling issues with any of them. There are a million ways to build them but as mentioned earlier the rod ratio isnt the best, drilling steam holes, the need for a new blancer etc etc, I like them but I would upgrade the 383 with a good head/cam/intake combo instead unless you want to build the 400 while still driving the car.
Safety Car
Joined: Jan 2009
Posts: 3,736
Likes: 56
From: anchorage ak
If you want to build a 400 sbc, save the money and go with a dart shp block, new versus 30 or 40 years old, with the main priority oiling and the new block being set up for a roller cam and splayed mains, you cant hardly go wrong. By the time you did the later 2 to the oe 400 you would have as much money in it if not if not more, & it would still be 30 to 40 years older.
Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
Well, certainly can't argue with the last couple posts, as always best taking your time building a second engine, and still being able to drive the car. Always the way I've done it, as sometimes, you're just wanting to take a break from it. Then, just a quick weekend swap.
Drifting
Joined: Dec 2005
Posts: 1,360
Likes: 3
From: NORTHEAST
If you want to build a 400 sbc, save the money and go with a dart shp block, new versus 30 or 40 years old, with the main priority oiling and the new block being set up for a roller cam and splayed mains, you cant hardly go wrong. By the time you did the later 2 to the oe 400 you would have as much money in it if not if not more, & it would still be 30 to 40 years older.
Drifting
Joined: Dec 2005
Posts: 1,360
Likes: 3
From: NORTHEAST
Don't be concerned with the heat at the center bores. You can plumb fresh water directly from the water pump to between those cylinders. Tap and thread the casting hole boss in the center of the side block wall, (a few have the plug hole there instead of the boss, then weld a bung in the plug for that hole)you can buy from Jegs or Summit a threaded spacer to go under your water pump. Plumb the fresh water from there.
http://www.chevyhiperformance.com/te...cks/index.html
Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
No need to drill the block and run water lines just use the correct gasket and make sure the deck of the block has the proper holes in the decks.
http://www.chevyhiperformance.com/te...cks/index.html
http://www.chevyhiperformance.com/te...cks/index.html
arp studs on the mains with the best head gaskets you can find
Thread Starter
Racer
Joined: Oct 2011
Posts: 318
Likes: 3
From: NP Nebraska
Good stuff guys. I think I will stay with the 350 blocks and build an internally balanced rotating assembly with roller cam and improve on the heads and other aspects of the drive train. I want to have an engine on the stand that I can build while I am driving the car. Heaven knows there are enough other things I can dump money into... Plus, this is my "learning car" so I can make my mistakes and then buy a C3 with a manual tranny to perfect.
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
Links Carl put up kinda make you think.
Dart block at the end of the day is REAL good money spent up front to save in the end and give piece of mind. Did a 408 Little M a few yrs back from any angle you can easily see the differences between that and a GM piece.
makes me think about selling my 509 block.
Getting it all done to have something go right towards the end of assy would be my luck lol.
That guy did it over 3 times talk about not learning the "cheap" lesson.
Dart block at the end of the day is REAL good money spent up front to save in the end and give piece of mind. Did a 408 Little M a few yrs back from any angle you can easily see the differences between that and a GM piece.
makes me think about selling my 509 block.
Getting it all done to have something go right towards the end of assy would be my luck lol.
That guy did it over 3 times talk about not learning the "cheap" lesson.
Thread Starter
Racer
Joined: Oct 2011
Posts: 318
Likes: 3
From: NP Nebraska
So I couldn't resist picking up a SBC 400 yesterday. A guy on CL.com had a complete engine out of a '79 pickup for $100. Had a complete QJ in good shape, flexplate, and newer dizzy. I figure if I am destined to learn this lesson the hard way, I might as well do it as cheap as possible. Even if I don't think the application will improve the 'vette, I'll probably put it in a truck I'm working on.
So I need to tear this thing down and get it to the machine shop for a flux, +/- bores and decks, and have them drill the holes in the decks. My thought is that the only way to have a significant improvement over the 383 vortec is to stroke this engine in the range of 427, run a milder cam (want more low end as I'm not on the track with this car), and put in a set of heads with better flow than the stock vortecs.
I'm open for suggestions as I start to plan this out.
Thanks,
Mike
So I need to tear this thing down and get it to the machine shop for a flux, +/- bores and decks, and have them drill the holes in the decks. My thought is that the only way to have a significant improvement over the 383 vortec is to stroke this engine in the range of 427, run a milder cam (want more low end as I'm not on the track with this car), and put in a set of heads with better flow than the stock vortecs.
I'm open for suggestions as I start to plan this out.
Thanks,
Mike
