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377 engine - how does it work

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by bajaviking, May 15, 2002.

  1. bajaviking

    bajaviking 1/2 ton status

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    One of my mechanic friends is saying that he will help me build an engine and he suggested that we could try to build a 377(supposed to be a 400 block with a 350 crank if I understood it right) since he has heard good things about the performance. Does anybody here run one of these and if so what is your opinion.

    Let me know the pros and cons.
     
  2. Z3PR

    Z3PR Banned

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    I've never had one, but I've seen them befor. They're the left overs from a 383 build. I personally plan on building a 415 in the next year or 2. If you've got the 400 block, look into a 415 stroker kit. I think you'd be happier with the 415.
     
  3. Mr.Chevy4x4

    Mr.Chevy4x4 1/2 ton status

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    A lot of drag racers run the 377 because it is a higher reving motor with the short stroke. You would be better off building a 383 for a 4x4 application. The longer stroke will produce more torque that the 377. Building a 377 requires using spacers for the main bearings and personally I don't like them. Go with a 383, parts are more plentiful and cheaper, and you won't have to drill steam holes in your heads. Just my $.02
     
  4. J.R.

    J.R. Guest

    im building one for my nova, there are 2 ways to build a 383 or a 377. you can use a 350 block and a 400 crank this is the most comon way. or you use a 400 block and a 350 crank and rods. the later seems to be a better mid and high rpm motor and it has beter rod ratio and angles then the 350 block and 400 crank. the down side is using a factory 400 block, when you start boring them they arent the strongest blocks and cooling becomes a problem. im using a world products after market block, they are made with more nickle in them and are stronger and cool better then factory ones. if you are going to use a factory 400 block then have it sleeved, this will make the block stronger and let you use the factory bore so you get 377 cubes. check out this web site www.ryanscarpage.50megs.com he has put together a list of engine combos that are dynoed and gives you an excellent idea of what and how you can make some serious power from a small block.
     
  5. Blazer1970

    Blazer1970 1/2 ton status

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    377 is a .030" overbored 400 block with a 350 (3.48" stroke) crank.

    383 is a .030" overbored 350 block with a 400 (3.75" stroke) crank.

    I don't know why anyone would want to destroke a 400 motor for a truck application.
     
  6. bigmack

    bigmack 1/2 ton status

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    I have never had a problem with the stregnth of a GM 400 block. Me and my racing buddies have built several and never had a problem with block stregnth. I have .030 over 400's (406's) in both of my trucks now (one 4wd and one 2wd) and haven't had any problems. As far as cooling I treat mine like they are big blocks, big 4 row radiators, & a good fan that throws alot of air and the temp runs about the same as other small blocks, but when you step on the gas they sure don't feel like other small blocks.
     
  7. 84_Chevy_K10

    84_Chevy_K10 Banned

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    I don't know why anyone would build a 383 if they had a 400 block, either.

    As for the bearing spacers, they make spacer bearings now I believe so that you won't need spacers.
     
  8. J.R.

    J.R. Guest

    you build a 377 because the shorter stroke with a bigger piston lets the engine windup faster. it also has better mid and high rpm power. the problem with a 383 or 400 sb is the rod ratio and rod angle, you want your rod ratio to be at least 1.6 or higher, a 400 sb with factory rods is at a 1.48 rod ratio and a 400 with 350 rods is at 1.52.
     
  9. Twiz

    Twiz 1/2 ton status

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    A 377 will have a larger piston.
    A larger piston will have more surface area to applie cumbustion pressures.
    More applied pressure will increase torque, much like a longer lever does.
    -
    ?
    -
     
  10. 84_Chevy_K10

    84_Chevy_K10 Banned

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    You can build it with 6" rods if you want so that's not a good point.

    And mid and high RPM power is not all that important in a truck compared to torque.
     
  11. J.R.

    J.R. Guest

    thats my point, a 377 is more of a mid to higher rpm motor. also when you use 6in rods you are changing rod angle and also the pistons sits at top dead center longer then the shorter rod. this has good and bad points to it so you really need to consult a pro engine builder if you arent sure of those points. when building a performance motor i want the engine to make as much power per cubic inch as it can and i want it to do it as efficiently as possible. this will make for a longer lasting engine and a more streetable one.
     
  12. bajaviking

    bajaviking 1/2 ton status

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    I guess I will have to be beat up my buddy for trying to talk me into building one of these. Sounds like the 383 makes a lot more sense for a 4x4. Would I be able to use my stock q-jet on a 383 or will I need to get another carburator.
    Thank you for your comments.
     
  13. bigmack

    bigmack 1/2 ton status

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    Your stock q-jet will be fine. I've got one on my 406 and it does great.
     
  14. J.R.

    J.R. Guest

    for your stock q-jet it depends how you build the motor. a q-jet will work but to get the max performance you may want to think about having it rebuilt . just jetting the primaries can make a big difference, your factory q-jet is made for economy not performance.
     
  15. J.R.

    J.R. Guest

    did you check out the web site i put in my first response? they have some excellent 383 combos with dyno proven power.
     
  16. bajaviking

    bajaviking 1/2 ton status

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    I did check it, a lot of good information, thanks. The reason I ask about the q-jet is that since I am on a limited budget(aren't we all) I want to run my old q-jet which works fine and later on I can upgrade it when I have recovered from the money spent on the stroker kit.
     
  17. J.R.

    J.R. Guest

    it should work, just remember the more power you make the more air & fuel it takes.
     
  18. RedDwarf

    RedDwarf 1/2 ton status

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    377 is superior to the 383. Bigger bore can breath better and that is good for power at all RPM
     
  19. Mr.Chevy4x4

    Mr.Chevy4x4 1/2 ton status

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    It is a proven fact that a 383 will produce more low end torque than a 377. Hot Rod Magazine did a shoot out a couple of years ago. With the same heads and the same camshaft the 383 made more torque and horse power all the way to 4600 rpm. The only people I ever hear of running a 377 are drag racers. Their power curve requirements and ours don't quite compare. 383 or 406 are your best options IMHO.

    Mike
     
  20. J.R.

    J.R. Guest

    i wouldnt say its superior , i have built both and they both have advantages and disadvantages. it really depends on your needs and how you build them. a 377 is an excellent motor but in my opinion if you want low end torque go with a 383 using a 350 block and 3.75in stroke crank and 5.7 in. rods. there is more machine work to this combo but it has proven low to mid range power.
     

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