brazky75

Guy I work with has 400 small block that he would sell me says something about being the last year they had the big valve heads? Is there any advantage of having 400ci over 350ci and what difference does this have with the ability to bolt up to every thing in my 75 like will the same headers work th400 tranny and so on. What is it worth as I would still have to go through the motor.

The Money Pit

The short of it is the 400 will bolt right in,and apples to apples parts "should" yield about 50 horse power over a similar 350.

If you want to ramp up the power,just keep in mind a bigger engine will need bigger parts,like cams,carbs,and heads.

American Boy

The 400 has bigger bore and bigger stroke. That translate in more low end torque and less rpm to get the same hp (or more hp for the same rpm). I ran the two type of engine in a 3800 lbs camaro and I loved the 400. With a mild setup, it loved to ignite the tires at 2000 rpm.

You'll need the flexplate and damper from the 400 since it's externaly balance.

I'd go with the 400.

Stephan

Daves76

400 is a good engine. The one thing you need to make sure of is that the 400 block don't have water passages between the cylinders, it has steam holes. Make sure that the heads you use have these "steam holes" there or you will have to drill them out (not a big deal to do). Also make sure the head gasket set you get has the holes in them as well. Beefing up the cooling system a bit is not a bad idea either to make sure it stays cool.

Dave

L88Plus

Have the block checked out by your machine shop before you buy it - they're notorious for cracking on the deck between bolt and steam holes and the bores. A 2-bolt is stronger than a 4-bolt, the outer bolts weaken the webs in the 400's.
If it's good, get after it. A pair of 200cc heads, 750dp and good intake, hydraulic roller in the 230 range and you'll shred tires like a recycling facility.

jackson

All the 400 I've scattered had small valve heads ... but I dunno why that'd be of much concern anyway because most folks that build up a 400 don't use OE heads ... more often than not the OE 400 heads aren't worth T&E to refurbish ... I'd say that even if it were a big-valve OE head.

More important 400 aspects are:
How much has it been bored? ... 0.060" is max ... beware some 400 can't even take 0.060".

is it 2 bolt or 4 bolt main? ... may seem counterintuitive, but in 400 2 bolt is preferred. But if it's not gonna be a race motor it really don't matter much.

because of it's large bore, it cannot use most 350 head gaskets ... there are few head gasket thickness options for 400 ... count on decking the block.

400's have short 5.565" rods ... most folks prefer & get$ longer rods.

400's long stroke (3.75") make more torque than a 350.

both 350 blocks & 383 cranks (same 3.75" stroke) are cheap & plentiful ... usually a good bit cheaper to build a 383 ... 383 performance close to that of 400.

What your co-worker's 400 is worth has much to do with what its bores look like & if it's 2 or 4 bolt main. If it's already at 0.040" over & has lotsa cylinder wear ... it ain't worth fooling with.

-edit- 400 blocks real popular in sprint cars ... lotsa sprints around davenport ... surprised there'd be many GM 400 left that haven't been bored to max.

73VetteKS

I would go with the 400. I built one in '75 that I put in a '74 CJ5 Jeep with a Muncie and Alum Flywheel, Angle Plug heads, headers, Edelbrock intake 700cfm carb, cam’ed it to peak about 5000rpm. It was one of the most enjoyable builds. I only used 1st when off-roading where I needed to go slow. With the low-end torque it generated, I didn't need 1st for the street. I have a 400 in the shed that I have plans to build once I retire in a couple of years. Collecting parts now.

Just make sure it has the mounting holes in the front for accessories such as the power steering pump. I think there were some years of the 400 that didn't have the holes taped for accessories.

As mentioned, you will need the correct flywheel, and you will need the correct balancer. The 400 is externally ballanced like the 454.
-Jim

Durango_Boy

The 400 I bought a few years ago hadn't been bored at all. I had it bored +.020 so I now have a 405. I think Sam's 400 was bored fresh +.060 when he got it, and it's a 412.

I have yet to finish my LT1 topping of said 400, but I'm anxious to feel what it's like in a Vette.

markdtn

No substitute for cubic inches, no doubt. Aren't there issues with the power steering pump hitting the balancer in some applications?

Durango_Boy

Maybe with an 8" balancer and a large diameter power steering pulley...but that's not an issue with serpentine.

LT1-405

brazky75

From what I found out at work the motor came out of an el camino the transmission is with the motor and has a shift kit in it. Supposedly it jumped time when it was in the el camino and they couldn't get it to start. If he quotes me a price what would be an acceptable range

gorrilla

the only real problem I ran into when installing my .060 overbore 400 in my 75 was that there were no holes drilled or tapped in the block for the power steering pump. Please ensure that they are there BEFORE you install the motor. we had to remove the engine and drill and tap holes in the block so we could mount the power steering pump.

Belgian1979vette

If it was a block out of an automatic, and you have manual, check for the hole where the rod of the clutch goest to. If necessary drill it before putting it in the car.

Bee Jay

I too have a line on a cheap 400. How hard is it to make a stock 400 internally balanced. Will a stock 400 take a 4" stroke crank to make 427? I always wanted a 427 Vette. Hey, DB, that serpintine belt system looks like what I want to do, but I have no AC, and only one alternator. Alternator, short water pump, crank, and Power Steering. Can I use the Alternator as my tensioner? Where should I get the four pulleys?
Bee Jay

Durango_Boy

I don't think or have never heard of someone changing just pulleys, so if you're wanting to get into serpentine you'll want to get the proper GM brackets and water pump. It's really a very easy swap. The A/C can be deleted with a pulley found on Ebay. Your power steering pump will work once you change pulleys, and you can run without the smog pump. You'll need a CS style alternator, and you'll have to use a tensioner for the belt. If you ever watch a serpentine engine run you'll see the tensioner is never static...so I don't think using the alt will work for you as a tensioner. The reason you need a new water pump is because with a serp belt the water pump would be turning backwards and it wouldn't cool your engine.

lars

A stock 400 makes a good truck engine and a lousy Corvette engine - a well-built 350 will take a stock 400 any day.

The 400 makes an outstanding starting point for a fantastic high performance engine, but you need to fix some of its problems:

The 400 is a low compresion smogger motor with really lousy heads. You need to install a good set of heads.

The 400 has rediculously short rods that are not conducive to a perfromance application. Replace the rods with 6-inch rods.

Use the lightest pistons you can afford and get the compression up into the 9.5 to 10:1 range with a good cam.

Most 400 blocks do not have the holes drilled in the front of the block for the 350 power steering pump bracket. You have to drill and tap them.

400 automatic blocks do not have the hole drilled for the clutch Z-Bar - you have to drill and tap.

Once you fix these problems with the low-compression smogger truck engine, you get an engine that really screams. But I wouldn't waste my time swapping a stock 350 Vette engine for a stock 400 truck engine.

Me80C3

400 blocks tend to crack at the steam ports, also the heads. Personal experiance!
IMO, pull the crank and drop it in a 350.

Alwyn678

YIKES SCARY

Me80C3

FACT!
Been there.

Durango_Boy

C'mon...the words "Tend To Crack" and "Fact" cannot be used together. If it was a fact like you say it is, then all 400 blocks would crack around the steam holes. This is not the case. I have been around plenty of 400s throughout my life, owned one, played with two more, and NEVER seen one with these cracks.

I cannot say it doesn't happen because some people have experienced cracks like you describe. Just don't scare someone away from an engine possibility because you have had bad experiences with them.

Maybe elaborate a little as to your applications. Did you race or drag with these engines? I tend to believe that a well maintained 400, that's kept cool and cared for would not crack.