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How to build a VERY low budget 400 sbc

Discussion in 'The Hokey Ass Message Board' started by kscarguy, Jun 1, 2012.

  1. I want to "assemble" a low buck 400 SBC engine. It is going into my car hauler and I want to see if I can keep the price low and the fuel MPG high.

    Any ideas on how to build it cheaply...yet make it run good?

    Here is what I have to work with...

    To start with, I have a running, stock 1973 Impala, 400 SBC motor (block 3951511) with stock heads (3973493). I also have a 80-85, 350 4 bolt main engine that is probably worn out (judging by the loose valves in the heads).

    In addition to the stock 1973, 400 SBC heads, I have a set of rebuilt heads (333882) that have been completely rebuilt and have screw in studs. I also have a pair of new head gaskets.

    In the intake area, the 400 came with a stock cast GM 4bbl intake with an EGR valve blocked off, I have available a Weiand 8004 quadrajet intake and an Edelbrock performer manifold.

    Carb wise, I have a decent rebuilt quadrajet and a new AFB (600 or 650) to choose from. I also have the complete TBI injection setup off a 350 truck.

    The Ignition system I have is a stock HEI.

    The truck already has full length headers and dual exhaust.

    Overall truck vehicle weight is around 7000# (guessing), motor should turn 2200 rpm at 70 mph, 4:11 gears and 33" tall tires, Trans is a 700R4.

    Any way to assemble this mess into a good street motor that gets good MPG and yet keep the price really low? Or should I just run the 400 as a stocker?

    I's like to keep the price of additional parts under $300. Anyone up to the challenge???
  2. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 1,174


    Put some 305 heads on it to get the compression up , they have small ports to get good velocity at the RPM you'll be using.
    And get a good RV towing cam [ high lift but short duration ]

    Everything in the short block can be stock [ buy a rebuild kit ]

    What you're trying to do is get it to behave like a diesel engine [ really crisp down low ]
  3. I want a nymphomaniac with an oral fixation that owns a tequila factory.

    Be lucky to see 10mpg empty with that rig.

    Performer (not rpm) and a truck or RV cam should help.
  4. Really, only two responses? Perhaps there aren't any motor builders on the HAMB who know how to build inexpensive motors for a daily driver...? :(
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  5. Diavolo
    Joined: Apr 1, 2009
    Posts: 796


    At the risk of keeping this thread alive, I will have to chime in and say there is no realistic way you are going to do what you want to accomplish with the amount of funds you want to spend. There are lots of options, but each one will cost a certain bare minimum of cash if you intend on doing it right and having anything even resembling a reliable machine when you are done.

    If I had a thinner skin, I would be offended by your comment...

    If $300 was all I intended to spend, I would fold the stack of bills and stuff them in my pocket and consider a less expensive hobby.
  6. aaggie
    Joined: Nov 21, 2009
    Posts: 2,431


    A good gasket set and rings would eat up $300.
  7. LWT
    Joined: Jan 3, 2012
    Posts: 188

    from Va.

    Don't forget the steam holes in the stock 400 heads, if you use other heads they would need to be drilled. I would use the performer, afb, 400 heads, performer cam & call it good. The 400 is a great engine for what you are doing, it doesn't need anything fancy to work well.
  8. dave lewis
    Joined: Dec 12, 2006
    Posts: 1,294

    dave lewis

    A set of stock vortec heads is a better choice....
    smaller chambers,tall,narrow ports and high swirl chambers.
    the proper intake from speedway (edelbrock vortec performer clone ) is about $ 150.
    Use the cam that came with the engine if its in good shape,,,replace the timing gear set with a true roller set..make sure you advance the cam 4 degrees..(they are WAY retarded from the factory)
    It will run unbelievably well..If you dial it in it should see 15 to 18 mpg...
  9. Turbo26T
    Joined: May 19, 2004
    Posts: 1,038


  10. KS- Make sure your cooling system is in top shape too. Lots of cracked 400s out there from overheating and those steam jackets aren't the greatest. Careful with the timing too- put some of that cheap ass AMPM gas in there with too much timing it'll die in no time.
  11. Engine man
    Joined: Jan 30, 2011
    Posts: 2,629

    Engine man
    from Wisconsin

    The only way to do it for $300 would be if you had your own machine shop. Even then it might not be possible. You probably need to bore the block, new pistons, turn the crankshaft, valve job and a roller cam and lifters, cam bearings, rod and main bearings, valve job, align bore and you should recondition the rods. $3,000 would be closer.
  12. marxjunk
    Joined: Feb 4, 2010
    Posts: 75

    from KCMO

    Im in KC..if it where me, id take that 300 and keep an eye on craigslist..sell some of the stuff you have collected,take that money and go buy a motor you can hear run..ive bought 3 running 327s for less that 400 each, a 400 running for 450...ya just have to be diligent, get a plan...carbed motors are everywhere for cheap here...saw a 454 running and driving for 650...better ways to spend money than trying to save some...
  13. LWT
    Joined: Jan 3, 2012
    Posts: 188

    from Va.

    I'm taking it that the 400 runs decent now & has some life left in it. I think he is just wondering about a few bolt ons not a rebuild.
  14. biscaynes
    Joined: Mar 16, 2008
    Posts: 1,639


    yep, 3 bills will get you rings, bearings and gaskets.
  15. HamD
    Joined: Mar 3, 2011
    Posts: 296


    The TBI with a xxxx747 service # ECM is beyond well documented. Everything you wanna know about it is out there. Using a vaccuum HEI gives up the ECM timing curve possibilities so if you go that route, get the right distributor. If you want it to run correctly and get mileage, make sure it has a VSS and is setup just like a 95 truck.

    You can adapt it to the GM intake with a simple adapter; 454 TBI trucks had an adapter like that on a 4bbl intake.

    EGR helps mileage if setup correctly and the only downside is 200k miles later, you might clog an EGR passage in an intake. If you really want mileage, add it. I just did an intake swap last year (clogged passage) and mileage is up a good bit plus it's running cooler.

    Technology is your friend and the Vortec heads are the final in a series of head advancement that started with the aluminum head LT1, progressed to the iron head LT1 (better flowing,) then to the Vortecs. They're worth the expense of a new intake.

    $300? Really? Why take the pinnacle of displacement in the good running but still budget engine of the century and then half-ass it?

    I have an upcoming 400 EFI job. Gotta start doing some parts hunting. :)
  16. Rattle Trap
    Joined: May 11, 2012
    Posts: 358

    Rattle Trap

    The last motor I built on the cheap cost me $600. And this was done with all the machine work done for FREE.
  17. zman
    Joined: Apr 2, 2001
    Posts: 16,505

    from Garner, NC

    Perhaps those that build motors here live in reality. What you are asking is pretty much impossible on your budget.
  18. Biscayner
    Joined: Jul 1, 2009
    Posts: 54

    from MN

    Doing a cheap 400 does not exist anymore. That being said it is just that the parts are more expensive than years ago. The 400 I just took out of my Son's Biscayne ran fine but it runs hotter and used more gas than the 350 Vortec engine it just got.

    A Vortec head 400 like the other guy said is a good idea and with those heads you will be close to 10.5 if not 11. to 1 compression which is ok as long as the cam you use is on a 114° LCA. Guys are making 500 lbs tq. with the vortec heads on 400's and you just have to find good used parts cheap.

    If you plan to use TBI the vortec intake is big bucks as I spent over $350 just for that and $200 just for the 454 throttle body. If you go that route let me know and I will give you a deal on both.

    As for fuel mileage anyhting more than about 15 in town and maybe 20 on the hwy. may be possible but you would need the right gear to make it work or overdrive.
  19. Thanks for all the replies, guess I had to shake things up a bit...sorry.
    Some very interesting stuff. I do need to make a few corrections.. Tire height is 30" Weight is more like 6000#.

    My 400 runs well as-is. Since we all messed with low dollar stuff in high school, I thought $300 would be sufficient to hop it up a bit especially since I have a bunch of parts already.

    I think I can divy up the $300 goal as follows:

    $100 - Summit Racing cam and Lifter kit (build low rpm torque)
    $65 - Speedway motors head and intake gaskets
    $35 - cloyes double roller set
    $95 - eBay used 3.73 gears for my 14 bolt diff. (down from 4.10)
    $5 - Chevy orange spray paint (always makes them run fast)

    Drill steam holes in my rebuilt 76cc heads that have hardened seats
    Install the performer manifold I have
    Use the quadrajet I have (easy to try the AFB)
    Swap the cam. lifters and timing chain to get more torque (???)
    Swap the gears to reduce rpm (from 2250 to 2050 @70 mph)

    I'd like to change the heads to smaller combustion chambers, but I read somewhere that vortec and 305 heads up the compression too much for the stock pistons. Will a 72cc head work with 87 octane and stock pistons?
  20. mike hohnstein
    Joined: Dec 4, 2011
    Posts: 263

    mike hohnstein
    from wisconsin

    Years ago I built a 400 for towing, truck was a 78 3/4 t Chev. carried a 10' camper and pulled a 22' tag with a 3000# drag car. 3.73 gear, NP540 5 sp trans, 31" tires, performer, Q-jet, stock type heads but CR was 9:1, balanced assy. smooth runner, sounded great, ran like a watch got 3 mpg. Yes 3 mpg from WI to Idaho for a race @ Firebird, and back, then I took it all apart, put a 350 and granny gear 4 speed and sold it all. Next truck was a 79 single wheel crew cab with a 454 and a T-400, LEFT IT ALONE. I suspect the fact I left the stock length rods in there was probably part of the problem. Rat motor truck with same load got 6.5 all the time.
  21. Seems I've upset some people here. That was definitely not my intent.

    The fact is, I have a budget. End of story. I started this post to see what, if any, improvements could be accomplished on that budget and with the parts I already have, rather than just installing the motor bone stock.

    Thanks to those who understand my goal. Sorry to those I've upset.
  22. zman
    Joined: Apr 2, 2001
    Posts: 16,505

    from Garner, NC

    Is that manifold squarebore or spreadbore? That'll make your decision.
  23. Bad Banana
    Joined: Jun 20, 2008
    Posts: 655

    Bad Banana
    from Michigan

    Facts are facts. Laws of physics says it takes X amount of fuel to do X amount of work. Production engines and fuel systems have had teams of engineers trying to wring every MPG and HP out of each combination. You can sometimes cheat the MPG a bit but you will suffer a power loss (lean). You can cheat the fuel a bit and gain some power with power enrichment but MPG will suffer (rich). If you increase the airflow through the engine (i.e. more cam, better heads, manifold headers, etc.) that increased airflow needs more fuel to support it. Period.

    The 2 biggest things you can do to improve fuel economy is either slow down (under 60 mph for wind load on the front) or lighten the load (take out all that shit you don't need to haul and start swiss cheesing everything). Most braggarts who claim huge fuel economy gains over "stock" are liars and want to justify in their own minds the money and work invested in their "improvements".

    Physics... it's the law. ;)
  24. Engine man
    Joined: Jan 30, 2011
    Posts: 2,629

    Engine man
    from Wisconsin

    I hear ya there. All of the ads for an air filter, exhaust system, computer chips etc that will boost power and save fuel make me laugh. Manufacturers these days are very conscious of fuel mileage and if there was anything they could do to bring their corporate average up, they would do it.

    I recall Hot Rod Magazine in the 70s taking a Ford van and try all of the various mileage improving parts on it. I recall the only appreciable difference they were able to make was removing the outside mirrors.

    EFI would be the best bet but it isn't cheap.
  25. I'm using a remanufactured 400 SBC in my 1948 Chrysler.....not finished yet, but it cost way more than $300.00....I spoke with the rebuilder and told him that I wanted a torque monster...not a high revving engine...I'm also using a modified TH350 with a stock converter and a 3:31 open rear diff....The 400 has an Edelbrock Performer w/Quadrajet, MSD HEI dizzy, ramhorn exhaust manifolds w/duals and Raptor Turbo mufflers....I'll be happy if this combo delivers 13-15 MPGs....If you think that 300 bucks is going to have you up and running...think again !!!...double that figure and even then it might not cut it for a budget build....these projects get real "spendy" real fast....I understand the concept of a budget too...spend money on the important things like a RV style cam and lifters, a good gasket kit, timing chain, and lap in your own valves...any farmed out machine work kills budgets quickly !...use what you already have on hand...its all the small stuff that adds up like fittings, hoses, wires, clamps, etc.good luck and keep us posted.
    Last edited: Jun 3, 2012
  26. All of my my intakes are spreadbore. I like the idea of using the stock manifold with the EGR to gain MPG. It is just so hard to pass on the Edelbrock. It seems counter productive.

    I think the TBI will cost too much to modify to run well on the 400, so I'll save it for a 350 bolt on swap in another project.

    Swapping in the 400 is just a bolt in operation. I already have a crate 350 in my truck and it runs and drives as-is. Only extra costs might be some small gaskets, antifreeze and fresh oil. The reason for the swap is to gain the extra torque.

    Any recommendations for the best size of cam running the stock pistons and the stock (rebuilt) heads that I already have? I am thinking of using the Summit Racing cam kits. I also am considering Northern Auto parts Kits. Both seem affordable.

    Does advancing the cam timing by 4 degrees really work? Anything to watch out for in a stock type motor?
    Last edited: Jun 3, 2012
  27. I also remeber that Ford van. They suggested not hauling your spare tires on the roof. Words to live by...harly ever see them on the roof of a camry.
  28. So far on my build, I have spent:

    $75 for a new Crane cam (pn 113901)
    $47 for new Crane Energizer lifter set
    $72 for new Fel Pro head gaskets, Summitt intake gaskets, Cloyes 3023x double roller chain and Comp cams break in lube (just in case).

    I have a chance to buy a new set of steel 1.6 rocket from Jegs for $20. Not sure if it is worth it for a low RPM motor. Someone suggested it on the initake valves only

    Keeping close to my budget so far...
  29. deto
    Joined: Jun 26, 2010
    Posts: 2,613


    58cc cast iron heads on a 400CI motor for hauling... no bueno
  30. raengines
    Joined: Nov 6, 2010
    Posts: 227

    from pa.

    don't forget the flywheel is special for the 400 too along with the damper

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