400 to a 350

[jbirdbobio]

Thinking of buying a 350 crate engine and transmission. The 400 that is in my 76 K10 has not been started in 20 years, stored inside and still moves free. If I go this way does anything have to be changed. Seems basic I know, just wanting to know my options. Thanks

[jocko]

Hmmm.. My 400 in my 76 K20 was swapped for a 350 before I bought it and I wished I still had the 400! Ha. I don't think there is much you need to do for the swap - most crates accommodate multiple mounting bracketry for a/c and p/s, etc. Jeg's usually has the best deals on GM crates if you wait for one of the frequent sales. I really think the 350 is a better engine, but I kinda wish I still had the 400 just to be original. I know, it's silly! I'd note dipstick side and make sure you don't have any interference problems. And, depending what you're converting from, you'll need to have trans cooler lines, fill tube access, etc.

[87Skier]

Externally they are identical for gen I small blocks (1955 to ~1998). Vortec engines were the only oddballs. They came with roller camshafts and different intake manifolds.

If you buy a crate engine with Vortec style heads and roller cam to put in there, you can buy your trucks engine mounts to bolt to the engine. Some aftermarket engines come machined for lever operated fuel pump, but all the factory vortec engines never came machined.

You have to watch out for the Camelhump heads and anything off a corvette, because those usually had weird accessory drive setups that require lots of work. Any other car/truck accessories will bolt up to all Gen I small blocks.

Keep in mind that Chevy didn't go roller cam in trucks until mid 90's, so if you get a roller camshaft you have to swap out the gear on the distributor, or you risk chewing something up.

[geezer#99]

And you'll need a different flywheel or flexplate. Depending on tranny.

[Dead Parrot]

IIRC, the 400 is balanced different from the other SBCs. You will need a non-400 balancer.

[El Dorado Jim]

Originally Posted by geezer#99

And you'll need a different flywheel or flexplate. Depending on tranny.

x2,the flywheels and or flexplates are balanced differently for a 400 and will not work on a 350... and I think you will be happy with a new crate engine, the 400's were not that good, I had one and didn't notice anymore power, they can run hot also, the cylinders are siamesed, no water jacket between them...

[slotard]

If you're going with a crate engine I'd strongly consider going Vortec (with carb). Modern oil has less ZDDP because it's harmful to catalytic converters, and therefore flat tappet cams don't last as long. It also has less drag and therefore better power/mileage for the same lift profile... and you can get away with more radical profiles without killing the cam.

Vortec heads flow great, better than any other factory heads.

I'd also consider going 383, but that really depends on what you want.

[geezer#99]

Here's the best bang for your buck in a crate!
http://www.jegs.com/i/Chevrolet-Perf...30282/10002/-1

[MikeB]

If the truck hasn't been touched in 20 years, that engine might be in OK shape, assuming spark plugs were left installed, along with air cleaner, oil filler cap, and breather. I'd first try to turn it over with a fully charged battery after changing the oil & filter, and squirting light lubricant of some kind in the cylinders. If it turns over OK, that's a good start. Then actually getting the thing started is gonna require fresh gas and probably some carb work.

Speaking of gas and carb, before turning the engine over initially, I'd disconnect the fuel pump output line and let the pump push whatever comes out of the tank into a bucket, not the carb. And then you'll have to drain or suck all the gas out of the tank.

[jbirdbobio]

thanks for all the replies, much appreciated. MikeB do you really think it could fire up. I have put miracle oil in the cylinders. Seems as though compression is good. It was always inside.

[Dead Parrot]

No reason it shouldn't start if you do a little pre start prep work. I would lift the distributor cab and blow all the fuzz, and dead spiders out. Dark quiet places just call to small spiders. Assume that whatever is left of the 20 year old gas in the gas tanks is bad for your motor and carb. For a quick test, disconnect the rubber fuel line from the frame to the fuel pump assuming this is a normal mechanical fuel pump/carb setup. Then pour a small amount of gas down the vent on the carb. Not down the venturis, but the vent. On a QJet, it is the small upright pipe in the middle. 1/2 of a cup is about right. You are trying to fill the bowl in the carb without flooding the intake. This way, the carb will work normally for a few seconds. If it starts, it will run a few seconds before the gas in the carb is gone. With luck, your next project is to clean out the stuff that used to be gas that is left in the tank(s).