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400 rebuild and 700Tranny Swap Questions

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by SummitXMK, Sep 4, 2001.

  1. SummitXMK

    SummitXMK 1/2 ton status

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    I am thinking long term of a raptor in my truck. However I think I will need a rebuild first. So what are some suggestions for a rebuild of a 400. I am looking for the best milage at 65 to 70 in overdrive.I know that it will never be great! However I still need to pull a hill or 8. What will the rebuild cost. I can take the motor out and put it back in. I will probably have 31 or 32 inch tires with 3.73 gears and a 203 transfer case. Also when I swap to a 700 how do you bypass the computer and how do you mount the TV cable?

    78 K5 Cheyenne 400 th350 203 With lots of miles
     
  2. hawglet

    hawglet 1/2 ton status

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    I can't be of a whole help as to I bought mine it had the 400 backed by a 700r4. Mine is all 100% purely stock just rebuilt, it gets about 10 to 12 mpg in town with 3.73 and 33's, but I can't really keep my foot out of it, highway milage is about 14 to 16 not to great but alright. As long as you don't have problems keeping the 2nd-aries closed you'll be alright with milage and your tires should spin too much. I can ask the guy that I bouhgt mine from how much he has into the motor,if you like? Let me know.

    Thanks,
    Greg Gayman
    Hawglet
    Stovie
    hawglet@excite.com
     
  3. Andreas

    Andreas 1/2 ton status

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    If you want defenite parts for your sbc400 rebuild here´s my $.02

    Comp Cams Xtreme 4x4 254 or 262 hydraulic camshaft, the milder one if you´re towing. Double rollerchain camdrive. Find a some reasonably priced good heads, like World Products Torquer. Keep your compression around 9:1. Rollertip rockerarms. Edelbrock Performer Air-Gap intake. A good Q-Jet or Edelbrock 750. 1&5/8" primaries headers and full dual exhaust. Along with machinework (hot-tank, boring, honing, freezeplugs, cambearings, balancing etc.) it will NOT be a cheap engine [​IMG] but it´ll bonk out 425-450 ft.lbs between idle and 4000 rpms (along with around 350 hp @ 5000rpms)

    Cheaper option would be all of the above minus the heads.

    More expensive option would be all of the above plus GM 5.7" rods and new pistons designed for 5.7" rods. This enhances the stroke-rod ration, decreases cylinderwall wear. It´ll rev more freely but you´ll loose a couple of ft.lbs of torque due to some geometric leverage stuff...[​IMG][​IMG]

    /Andreas

    406cui of pure sh*t[​IMG]
     
  4. SummitXMK

    SummitXMK 1/2 ton status

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    hawglet, See how much and what some specs might be if you can.
    Andreas, Thanks those are the specifics I was looking for. This probably won't happen till after winter as I am already running short of fun money and the snowmobile season hasn't even started yet. This way I can price things out and maybe start buying pieces here and there. If I don't wreck my sled again and have to fix it!!

    78 K5 Cheyenne 400 th350 203 With lots of miles
     
  5. Andreas

    Andreas 1/2 ton status

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    Yeah, that´s just what I did with my 406. Bought a piece here and a piece there. Took me little over a year to build it. I went with the 5.7" rod option but kept my heads, as they are ported, has bigger valves and so on. Oh, another thing. Should you decide to stay with the stock 5.565" rods be sure to put ARP bolts for ´em on your shoppinglist. Cheap lifeinsurance as rodbolts probably are the most stressed part in the whole engine [​IMG]

    /Andreas

    406cui of pure sh*t[​IMG]
     
  6. 84_Chevy_K10

    84_Chevy_K10 Banned

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    The 700R4 doesn't require any computer, it's controlled completely by the TV cable. You mount it with a bracket that bolts by the carb.

    S/R torquers are nowhere near big enough to feed a 400 SBC. It's not a 350 and you need much more flow for good performance than they're ever going to reach without massive porting.

    I have the Xtreme 4x4 250 grind cam in my 305. I can't imagine a 254 grind being even near enough cam for a 400 SBC, even for a low-rpm toque monster. You've got 30%+ more motor to feed, and that's not going to be enough. The 262 is probably the better choice there. You might even be able to be a little more liberal on camshaft. A bigger motor will eat up the usual characteriscs of a bigger camshaft.

    To me, it sounds like you've built a few too many 350s. 400s are a different animal. The parts you've mentioned would build a great 350, a damn good one for a truck, but a 400 you could be a little more liberal and squeeze out some more power.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  7. Neil

    Neil 1/2 ton status

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    the first 400 I built was in a 2wd and had plenty of power, but not GREAT on gas. The happy medium is one that will be lacking of the power you might be looking for. A 262 cam, some Vortec heads or 041,487,441 heads do great with 1.94 and 1.60 valves. Make sure they have the little steam holes drilled out of course! Get a new or remanufactured water pump for sure. In my experience the best carb for power and mileage is the Edelbrock Q-jet replacement line of carbs, Usually $200-275 at most auto parts stores like autozone or discount a.p. A 700-750 cfm is probably what you'll need. A divided plenum aluminum intake is fine for what you want. GM HEI distributor of course. Roller rockers are NOT necessary for street and off road use. They are big $$ compared to stamped 1.5 or 1.6, and not necessary in what you have described. Go with flat top pistons for more compression and some head surfacing maybe. Have it all balanced at machine shop. Just remember- strong bottom end and good flowing valvetrain-key to power. This all will give good power and decent mileage considering the application. Been there in your shoes and I know about power/mileage vs. budget. E-mail me if need any more help or finding parts.neilheis@yahoo.com

    Neil H.. Alabama.. '78 K5 400ci 4x4 AT,AC,PW Cheyenne. '74 C10 3spd/floor 250ci 4x2
     
  8. Neil

    Neil 1/2 ton status

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    OH yeah..this will be a $800-$1600 project easily. Try swap meets or buddies for parts. Hook up with some local racers and see if they might have some extra or salvage parts.

    Neil H.. Alabama.. '78 K5 400ci 4x4 AT,AC,PW Cheyenne. '74 C10 3spd/floor 250ci 4x2
     
  9. CaptCrunch

    CaptCrunch 1/2 ton status

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    A 700r4 IS controlled by a computer!!!! The torque converter lock up is activated by a computer in I believe 85 and newer trucks... the 82-84's had a seperate box/computer that controlled lock up. If you don't get the converter locking up correctly the tranny will fry faster then bacon and eggs. Painless wiring and TCI I know both make kits that run about $50 and allow the converter to lock up w/ a now computerized vehicle. Also don't forget about the Tcase... That presents another set of questions and then after those 2 are squared away you can detirmin what driveshaft and the length you will need.

    I agree the Torquers are a bit weak headwise... I would pay about a hundred or so more and get the sportsman II's. The 400, like the 383 loves to breathe and like a 190 or 200cc port head. #1 is either AFR heads in that range... next choice would be Brodix and my third choice would be Edelbrock RPM's. I do believe all the heads will need to be machined for the 400's steamholes though.

    -Mikey
    1987 Chevy K5 Blazer- 350 TBI
    <a target="_blank" href=http://coloradok5.com/gallery/captcrunch>http://coloradok5.com/gallery/captcrunch</a>
     
  10. Andreas

    Andreas 1/2 ton status

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    Tim, I agree the 262 would be the better choice. I try to be conservative when giving advice to others. Wouldn´t wanna recommend a big cam that doesn´t run or perform very well right off idle.

    The S/R Torquers has 170cc intakeports. Stock csb heads, even the best ones, are what? 150-155cc´s? I´d love to recommend 195cc Canfield or AFR´s but then we´re talking big money.

    I run Xtreme Energy 274 in mine (230/236 .487"/.490"), Performer RPM intake, Holley 780, I have ported 64cc ironheads with 2.02" &amp; 1.6" and run 10.2 compression (Speed Pro Hypereutic pistons with a small dish). I may have to run 2000-2200 stall with this cam. Haven´t started it up yet because the Blazer is.... well... in a million pieces all over the floor[​IMG]

    Neil, the rollertip rockers I recommended is a good buy. Easier on the valvestems and reduces some friction. They aren´t very expensive, like $80-90 or so.

    /Andreas

    406cui of pure sh*t[​IMG]
     
  11. SummitXMK

    SummitXMK 1/2 ton status

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    Thanks alot guys. Now I will have to do some reserach and start saving! Anybody know a good motor builder in Boise, Idaho?

    SummitXMK

    78 K5 Cheyenne 400 th350 203 With lots of miles
     
  12. Neil

    Neil 1/2 ton status

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    Where do you get roller rockers for $90? I need to go shopping with you. Understand that I was just trying to keep his costs down. I agree they are nice to have. I have had Crane and Summit RRs and they both were $150 +.

    Neil H.. Alabama.. '78 K5 400ci 4x4 AT,AC,PW Cheyenne. '74 C10 3spd/floor 250ci 4x2
     
  13. Andreas

    Andreas 1/2 ton status

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    Neil, rollerTIP rockers, not "full" rollers. The budget kind with only a wheel at the tip of the rocker, not on the stud [​IMG]

    /Andreas

    406cui of pure sh*t[​IMG]
     
  14. Neil

    Neil 1/2 ton status

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    O Tay. I see.

    Neil H.. Alabama.. '78 K5 400ci 4x4 AT,AC,PW Cheyenne. '74 C10 3spd/floor 250ci 4x2
     

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