Picking up a 400 SBC - Chevelle Tech
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post #1 of 99 (permalink) Old Oct 15th, 19, 4:17 PM Thread Starter
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Picking up a 400 SBC

Got an opportunity to pickup a 400 SBC tomorrow for 500 dollars.

What should I be looking for?

Motor is all together and running on a stand. It was on a airboat for a short while. Was bought from a guy who built it with a RV cam. The owner knows very little about it. It has stock heads on it and the bore is unknown.

I figure it might be worth picking up since Im thinking of building a 406 or larger for my 67.

67 chevelle malibu / SS/ custom

Currently undergoing a metal work to remove all rust, if I ever get there.

Cant decide on prostreet or cruiser with a 4 speed.
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post #2 of 99 (permalink) Old Oct 15th, 19, 4:48 PM
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Re: Picking up a 400 SBC

I have had several 400 SBC over that last few years but you can't get anything for them now with the big LS craze. Look for the 2 bolt mains as they are stronger for any kind of performance build being able to use splayed main caps. Most 400's respond well to the same add on's as any other SBC. Put some Vortec heads on it and the 400 will fly, just have to use good fuel as the compression can be close to 11. to 1 and that can get costly. I have one 400 that has some stock 80cc heads, 268 CC, Performer RPM with cheapo headers and a good carb, that motor just flat out fly's to 5500 rpm. My 12 to 1 406 has gone the best of [email protected]
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post #3 of 99 (permalink) Old Oct 15th, 19, 4:50 PM Thread Starter
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Re: Picking up a 400 SBC

Quote:
Originally Posted by 68Chevele View Post
I have had several 400 SBC over that last few years but you can't get anything for them now with the big LS craze. Look for the 2 bolt mains as they are stronger for any kind of performance build being able to use splayed main caps. Most 400's respond well to the same add on's as any other SBC. Put some Vortec heads on it and the 400 will fly, just have to use good fuel as the compression can be close to 11. to 1 and that can get costly. I have one 400 that has some stock 80cc heads, 268 CC, Performer RPM with cheapo headers and a good carb, that motor just flat out fly's to 5500 rpm. My 12 to 1 406 has gone the best of [email protected]
68Chevele - just looking to build a strong street engine...nothing more...need to run pump 93.
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67 chevelle malibu / SS/ custom

Currently undergoing a metal work to remove all rust, if I ever get there.

Cant decide on prostreet or cruiser with a 4 speed.
Aaron is online now  
 
post #4 of 99 (permalink) Old Oct 15th, 19, 5:49 PM
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Re: Picking up a 400 SBC

hi
Have block crack tested around head bolt and steam holes at least .
Sonic test bores .
Felpro do a high water flow gasket from memory that's recommended.
Always run steam holes in heads
Piston selection is better than ever re street forged, weisco pro tru street, mahle power pak . Try to use a combo with at least 5.7 length rods .
Balancing try to shoot for internal is preferable . Either use adapter bearings for 350 crank/ stock 400/ after market cast or forged steel

A pre balanced rotating assembly is best for the budget
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post #5 of 99 (permalink) Old Oct 15th, 19, 5:51 PM Thread Starter
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Re: Picking up a 400 SBC

Motor is complete right now...running on a stand...anything to look for in a running motor that is different from other SBC's?

67 chevelle malibu / SS/ custom

Currently undergoing a metal work to remove all rust, if I ever get there.

Cant decide on prostreet or cruiser with a 4 speed.
Aaron is online now  
post #6 of 99 (permalink) Old Oct 15th, 19, 6:07 PM
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Re: Picking up a 400 SBC

Hi
compression test --only an indication
leak down test closer to 10% leakage the closer to rebuild time [2-5% when new ]
oil pressure test---what is the oil grade ?

what do the spark plugs look like
colour and smell of oil
condition of coolant
Inside a valve cover is there sludge
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post #7 of 99 (permalink) Old Oct 15th, 19, 6:37 PM Thread Starter
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Re: Picking up a 400 SBC

Got those covered.

67 chevelle malibu / SS/ custom

Currently undergoing a metal work to remove all rust, if I ever get there.

Cant decide on prostreet or cruiser with a 4 speed.
Aaron is online now  
post #8 of 99 (permalink) Old Oct 15th, 19, 6:44 PM
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Re: Picking up a 400 SBC

I assume it is a dry set up with no water in the block. It would be nice to see it hold water and not leak thru the head gaskets or blow white smoke when it runs. Maybe you could rig up a water pressure test. I wish you were in Ohio. I have one I would sell.
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post #9 of 99 (permalink) Old Oct 15th, 19, 7:25 PM
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Re: Picking up a 400 SBC

I like the 400 small block because it make good torque, seat of the pants feel. Unfortunately the one I picked up last month turned out like this:

Now deciding if I go back to the 383 I started, or go with a 6.0 LS that my son keeps pushing me towards.
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post #10 of 99 (permalink) Old Oct 15th, 19, 7:27 PM Thread Starter
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Re: Picking up a 400 SBC

Quote:
Originally Posted by 1975TypeS-3 View Post
I like the 400 small block because it make good torque, seat of the pants feel. Unfortunately the one I picked up last month turned out like this:

Now deciding if I go back to the 383 I started, or go with a 6.0 LS that my son keeps pushing me towards.
What happend to the 400?

67 chevelle malibu / SS/ custom

Currently undergoing a metal work to remove all rust, if I ever get there.

Cant decide on prostreet or cruiser with a 4 speed.
Aaron is online now  
post #11 of 99 (permalink) Old Oct 15th, 19, 7:46 PM
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Re: Picking up a 400 SBC

Really do not know! It was a decent looking block, but I always have the cracked checked before I get into machining. I have found ones that had froze and cracked the valley near the head surface like you see here, but this crack is towards the bottom of the water jacket. I still have a good 4-bolt 1970 350 block that is bored .030 over and oiled down, I know that is a good block, but I really wanted a 400. Might get a Dart SHP block because by the time I purchase another 400 block, clean and crack check ($140 in our area), line hone, parallel deck, bore and hone I will be close to the cost of a new SHP block!
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post #12 of 99 (permalink) Old Oct 16th, 19, 5:35 AM
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Re: Picking up a 400 SBC

Hi
The reality is with a 400 block . They are only worth money if they have been bored no more than .020 bored .These days pretty rare . As we have said once u sonic test bores , crack test block and machine . An aftermarket block is only a little more . The biggest benefit is thick cylinder walls. Prevents overheating .. Resale will always be better also.

Other 400 setups
Do blueprint sell blocks only . They do sell a short.
Edelbrock sell blocks
Brodix and Dart are probably more $$
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post #13 of 99 (permalink) Old Oct 16th, 19, 6:47 AM
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Re: Picking up a 400 SBC

I love SB 400s and had one in HS. It ran hard too. If you update it, I'd look into longer rod/lighter piston set ups because the crank is already heavier than normal. The main webs crack and drop the crank into the pan when it goes bad. Lots of guys ran them dirt track while I was drag racing min and that was the biggest issue.

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post #14 of 99 (permalink) Old Oct 16th, 19, 2:02 PM
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Re: Picking up a 400 SBC

Quote:
Originally Posted by Aaron View Post
68Chevele - just looking to build a strong street engine...nothing more...need to run pump 93.
I understand completely, just use some 993 heads or the ones on my one 400 487X (X means 80cc not a special port) heads, that engine is 8.8 compression but still went really well. Best part is it ran on 87 oct.
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post #15 of 99 (permalink) Old Oct 16th, 19, 3:39 PM
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Re: Picking up a 400 SBC

I had a .030 over 400 in my 70. Forged pistons, stock rods & heads RV cam. All I can say is I really miss all of that torque.

Tighten it till it strips and back it off a quarter turn.
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