400 cracked block?

[TBMG270]

Buddy of mine has this 400 laying around he told me I could have. Gave it a once over and noticed it looks like it's cracked. Only its real shallow and looks awfully uniform to be a crack. I'm not entirely sure so figured I'd get some other opinions on it. Was also wondering if anyone's used a 400 in place of a vortec 5.7? I have a 96 k1500 with the 5.7 and a 5 speed. Originally auto but I solved that problem already. Oil cooler line blew out on me about a month ago and leaked all the oil out. Spun a few bearings and destroyed the cam, so I bought a short block from a local yard and that one also had a spun bearing. Took it back and they gave me an entire motor this time from a truck that was wrecked. Everything looked in great shape and couldn't feel any play in any of bearings, cylinder walls were nice, had good compression. Decided not to mess with the bottom end and just swap over my head's an intake and whatnot. Got it running and seemed alright. Made 40 psi oil pressure cold. Once it was warm it dropped down to around 20-25 psi at idle. Driving it the oil pressure would drop when accelerating and rise back up once I let off. Still stayed around the 15-20 mark at the least. It ran for 2 days and it was barely driven at all those 2 days. Last time I drove it it had 15 psi or so while driving. I pulled in my driveway and came to a stop and the oil pressure fell below 5. Shut the truck off and let it cool, went to verify oil pressure with a mechanical gauge. 30+psi on startup and fell below 10 when it was warm. Once it got warm this motor also started knocking. Go figure. I'm running pretty low on funds right now and need to fix this thing as cheap as possible. The yard won't warranty the motor a second time and most places around me want around a 1000 for 150k+ mile motor. I can't afford to spend that much at the moment and was thinking I might be able to get away with using this 400 if I could. I do have a tbi 350 laying around that ran when it was pulled but it's out of my old truck which was wrecked and became a woods beater. I've overheated it countless times and it spent more time at WOT and 5k+ rpm than it did at idle so I'm a little hesitant to use that one. It was always low on oil too because the pan leaks. I tried to blow it up numerous times and it refused to quit. Still don't know about throwing it in my daily tho.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

 

[94K3500PROJECT]

400 would be perfect IF you spend the money to do things properly.
Needs a roller cam retrofit and then swap everything from the Vortec over.
I have to assume it’ll need a tune.

I intend to swap a 400 based Vortec head/TPI intake setup into mine

 

[SAATR]

That's a casting mark left over from where the main webbing was machined. Certainly not a crack, though it could be a stress point that could develope into a crack if the engine makes enough power.

 

[RCSB91]

id take it to a machine shop and have them check it out..

 

[b454rat]

like mentioned, take it to a GOOD machine shop and have em check it out. 400s are awesome engines. I'd rather build a 400 over any other SBC. I'm actually gonna be building one for my 96 Yukon, using all the Vortec stuff. Really want to go full roller, but don't have an additional grand to spend on the retro kit. Can still make a **** ton of power with flat tappet. What ever heads you use, make sure have the steam holes drilled into them.

 

[TBMG270]

400 would be perfect IF you spend the money to do things properly.
Needs a roller cam retrofit and then swap everything from the Vortec over.
I have to assume it’ll need a tune.

I intend to swap a 400 based Vortec head/TPI intake setup into mine

Yeah I figured a tune would be in order. I need one anyways for the manual trans. And any reason the flat tappet cam can't be used? I know roller is the better option but to be frank this truck is a piece of **** lol I'm not shooting for big numbers here and I've spent WAY too much money on this thing already. As for swapping everything over, I'm assuming the 4x reluctor fits on the 400 crank? And timing cover would be just like making it work on a tbi 350? Also would their be any balance issues? I'd like to keep my brand new flywheel if possible.

 

[TBMG270]

like mentioned, take it to a GOOD machine shop and have em check it out. 400s are awesome engines. I'd rather build a 400 over any other SBC. I'm actually gonna be building one for my 96 Yukon, using all the Vortec stuff. Really want to go full roller, but don't have an additional grand to spend on the retro kit. Can still make a **** ton of power with flat tappet. What ever heads you use, make sure have the steam holes drilled into them.

Alot of people seem to love them. Met a few guys that loathe them as well. I don't care I just want the truck to move under its own power without making noise other than the obnoxious exhaust. Could you elaborate on the steam holes? And another thing, from what I've seen online most people bore these out like .030 at the most. This one happens to be bored .060. will this cause issues with a mostly stock setup? Theirs no cam in the motor so I'll have to figure out what to do there, I'd use my factory vortec heads and intake. JBA shorties into factory size exhaust no cats and some sort of ****** flowmaster. Have 2.5 inch to put on down to 3" single out. Just need a muffler. I'd love to put a TPI setup in it. That was my plan with the 350 and try to make as much torque as I could but the baseplate is so expensive. For that money I think I'm better off with a marine intake or aftermarket with external fuel rails.

 

[b454rat]

Because of the siamesed bores there’s not much room, so there are steam holes to help cool. I think, not an expert lol, but I know have to have em or will overheat. Again a good machine shop will understand. .030” is max safe zone. Anything over will get warm, .060” is DONE. I had one that was .040” and was hard to keep cool. Everything sill bolt up, timing cover, heads, etc, but need to use the 400 balanced with about 1/4” cut off from the end, where it slides in the cover. The reluctor wheel goes on first then balanced. Mine is ready to be put together, just need money. I have it bookmarked at home, an engine builder/magazine built one, nothing special, Vortec head, old school cam, small headers, 750, dual plane, made 428 horse n 525 torque. All down low. I’m putting a Ramjet intake n maybe the Whipple supercharger, dunno yet....I had stock 400s that ran friggin awesome, like a big block, lil cam n headers sakes em up.

 

[Madscientist]

It's not the bore size that make an engine run hot. .060 over is pushing it on the comfortable zone as these do have thin cylinder walls. Everyone says they are problematic but I've never had issues or personally know someone who has. I've ran a .030 409 casting 400 block 16psi with a 671 blower. Made 832hp on an engine dyno. Had zero problems! If your overheating. It's your coolant system. not enough timing with run hotter, too small of a radiator. Poor airflow. I would take it to a machine shop and have them check it out. If it checks out, use it. You can reuse your top end, need the steem holes drilled. (Little holes between the cylinders in the castings. Aids in cooling and prevention of hot spots)

 

[884x4310ci]

400 sbc need a specific balancer and flexplate\ flywheel.
As it is externally balanced. So your new 350 flywheel will not work.