350 or 400??

Discussion in 'Trucks and Trailers' started by 3/4tonTodd, Dec 21, 2000.

  1. 3/4tonTodd

    3/4tonTodd LawnSite Member
    from Iowa
    Messages: 127

    I've been putting together a list of stuff I need to replace the engine in my truck when the time comes that I have to do this (I think it's going to be within the next couple of months, but I'm hoping to hold it together at least until spring!!)

    The truck originally came with a 400 in it, and now has a 350. I've been looking exclusively at the 350 for the replacement, but last night I got to thinking about putting a 400 back into it. Good idea or bad?


  2. Jeff's Classics

    Jeff's Classics LawnSite Member
    Messages: 78

    Personally, I would stick with the 350, unless you have a deal on a 400. The 350 internals are generally cheaper if you need to replace them, though the crank, rods, and pistons should be in good shape either way. The biggest problem with the 400 in my opinion is that the middle cylinders (3&5 and 4&6) are siamesed, meaning that there is no water jacket between them. This has caused cooling problems for some folks in the past. Depending on your driving habits, the condition of your cooling system, and the climate you live in this may not be a problem. Don't you live in Houston, though? That's where I am located, and with the heat and traffic I'd avoid the 400. Also, the 400 was generally a low performance truck and passenger car engine. You never see 400 SS vehicles out there, they never made one. I think they are all 2-bolt blocks, not that it's a big deal for a nice driver, but the 350 is at capable of comparable performance for the same or less money.
  3. 85w/350

    85w/350 LawnSite Member
    Messages: 244

    I may be just a big fan of a 350 but I also agree with the last post...In my opinion stick with the 350 much cheaper parts and really easy to find. Just as much power probably about the same in gas mileage and the few people that I know with 400's in their trucks did have cooling problems in the summer down here in louisiana until they really put time and money into upgrading the cooling system. Keep it easy and get all the performance you could want out of a 350.
  4. 3/4tonTodd

    3/4tonTodd LawnSite Member
    from Iowa
    Messages: 127

    Thanks guys!

    I didn't know that about the 400 water jacket. I haven't yet driven this truck hard, though sometime in the future I'm planning on dragging a bass boat behind this thing, as well as taking it off road. Based on what you said, I'll probably stick with the 350.

    Oh, and I don't live in Houston yet - I'm in Iowa (under almost 30 inches of snow in the last two weeks). Me and the other half (and the wee little one) are considering Houston when I get done with college, so if you hear of any openings for a mechanical drafter, let me know!

    Thanks again

  5. John DiMartino

    John DiMartino LawnSite Silver Member
    Messages: 2,555

    While it is true that the 400SB has siamesed cylinders,my experiences with them have been excellent.They will not take an overheating very good,the 350 takes it better,but I had one in my 77'burban and i put one in my 81 Suburban after the 360 got tired.They are strong torque motors,great for a truck,and in 71 and 72 they had 4 bolt mains in some applications,not that they matter much .I ran a basically stock short block,.030 over and a Compettion cam 260H,with edelbrock performer intake and hooker headers,and a tweeked Q-jet.This thing grunted big time,and while the 350 will rev higher,there is no denying the 3.76 stroke and bigger bore,just more power everywhere,at any speed.I could pull a gear higher in most situations without even laboring.its your choice,Im just saying i had good luck with them,you do need a good sized radiator and to run the 400 though,since it does generate more heat than a 350,naturally since its making more torque.
  6. Alan

    Alan Member
    Messages: 1,185

    I've never had a 400, but looking at the specs it seems that they will make Rat torque while keeping the light weight of a Mouse. I missed out on one a few years back and when I get around to building my ultimate plow truck I'll definately try to find one to stick under that hood. I'm not knocking the 350 by any means, the 350 in my GMC 5500 is one impressive engine, as was the one in my 78 K10. I'd run one if I had it, but some day I want to mess with the big small block.
  7. Chuck Smith

    Chuck Smith LawnSite Senior Member
    Messages: 849

    I have a 400 in my 77 K/20. IT came with one from the factory. I replaced it with a built 400 motor. I never had a problem with cooling, even in the summer with the AC on with either 400. The truck came new with a 4 row radiator, the same one that GM used with 454's in these trucks. Use a 4 row, and cooling shouldn't be a problem. Oh, and my truck has a factory oil cooler too, which I am sure helps, as well as an aux. trans fluid cooler. John D is right, major grunt!

  8. mike reeh

    mike reeh LawnSite Member
    Messages: 229

    Id go with the 400. I will be doing a 400 build up in 2001 and my 77 K20 has a factory 400 in it... great motor. yeah siamesed cylinders in the middle but its not a problem with a decent cooling system. my truck has the heavy duty cooling system and the temp guage has never even FLINCHED in 100+ weather with the AC on. the real problem with the 400 is not that it creates so much heat, but that its more prone to damage when it does overheat. In fact one time my ignition system was pretty messed up and it DID overheat.. didnt get into the red but it was definately too hot, and it survived.

    john dimartino said it about the 350 revving higher.. the 400 will not make a lot of power at higher rpm but man it runs strong up thru about 4K.. probably higher with aftermarket stuff (mine is 100% bone stock).

    as for the 350 being cheaper, if you can get the block and crank, its all the same after that.. Heck I already got the 400 block and crank sitting in storage that Im gonna use, didnt pay a dime for it.. if I could pull that off, anyone can :)

    good luck and keep us posted
    mike reeh
  9. OuTLaW

    OuTLaW LawnSite Member
    Messages: 14

    Todd, just a thought you might want to look into. Why not have the best of both engines and build a 383?? 350 block and a 400 crank. I just finished the rebuild of an l98 in my vette. Bought the stroker kit for what a good crank kit would've cost and got even better torque than the l98. Mileage is the same as the 350 and no overheating yet. Its been in the 70s here in so. cal. but the temp stays at 175 in traffic. You can do the same thing with a real 400 crank but you'll have to get your local machine shop to cut the flange off and get your block clearanced. The 400 flywheel and harmonic have to be used as well. If you get a new crank that was intended for the swap you can use the 350 parts on it.
  10. 3/4tonTodd

    3/4tonTodd LawnSite Member
    from Iowa
    Messages: 127

    Actually I'm considering a 383, and here's the short version of that. The guy that owns and runs the machine shop here in town has one for $650 with 28,000 miles on it. The thing is, he built this motor for his own van. As one of my co-workers put it "Can you imagine how much care he put into that?"

    Thanks for all the advice guys!


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