454 BBC questions seeking advice

Discussion in 'Engine: Repairs , Modifications ,trouble shooting ' started by Arden, Aug 10, 2018.

  1. Arden

    Arden Member

    Hey guys,

    I stumbled upon this forum looking for information for my current project. It's a 1968 C10 with a 250 CID and 3 on the tree. It actually is tuned up and runs REALLY good in the dependability department; but, I have a hard time leaving things alone.

    I stumbled upon a 1975 C20 for the engine and transmission. It has a 454/TH400 combo that I was able to drive/compression test/inspect prior to purchasing and pulling the engine. The truck was originally a SBC car per the VIN but it was swapped out in the 90's per the owner who had the conversion done. The block is 361959 and the heads are 336781. The only visible change I could see was an Edelbrock aluminum intake. It still wore the Quadrajet and cast exhaust manifolds.

    My goals for the truck are 98% street and would sacrifice large numbers for reliability and a little lump to the exhaust tone. I want to be able to throw the wife the keys without having to explain a bunch of the trucks quirks first. Also, I'm going for a stock/restored look in the truck and would like to keep the stock exhaust manifolds. I have a huge cowl induction style/rubber gasket type air cleaner set up lying around so if I swap out the carburetor it would be pretty much hidden.

    Here is where my fork in the road is: Dropping in the 454 as it is would be a huge improvement over the 6 cylinder. I realize all these systems work together so I was looking at the highway RPM's of the TH400 with the 3.37:1 gears in the truck and realized with a 28 inch tall tire I didn't like where it was. Switching to a higher gear (numerically lower) such as a 3.08:1 was better but required switching the carrier which was ok because I need a posi. I also though about tracking down a 2.76:1 set of gears and posi but that proved to be much harder to do.

    So I decided to purchase a 1993 700r4 to get the overdrive benefits and ensure it was wired to lock up the torque converter. Initially I though I would match the torque converter to the cam but realized if I kept the 3.73 gears and only install a posi a high stall converter wouldn't lock up because the RPM's would be too low. So I'm leaning towards keeping the stock converter.

    The next issue is with all the weight in the front end I would like to get a set of reasonably priced aluminum heads to help out a little. This seems like a huge can of worms. I couldn't find a lot of examples of people keeping the dished pistons and low compression. There was the 454 RV test Hot Rod did where they added a $3,500 top end kit and made a lot of power. But aside from that, most of the information I've found is flat top/decked set ups or domed pistons. This adds a lot of cost for machine work and tear down versus slapping a top end kit on it.

    One of the issues with the C10 is, I'm sure traction will be an issue. In my case it doesn't make sense to try and build a 750 ft.lbs monster if I can't use it on the street. I'm running a 245/45 tire so I'll be traction limited.

    Then of course there is cam selection with the relatively small cubes and very low compression. I'm pretty lost on this because the more I read and research the less I know.

    I did commit a Grumpy sin and purchase a 750 vacuum secondary ultra street avenger carb that I'm hoping I can make work (factory refurb deal). I couldn't use the Quadrajet because I was planning on running the Bowler TV cable set up with the 700R4 and they didn't support the stock carb. I've read some negative issues with the BowTie Overdrive kit and don't want to chance burning up the transmission while I'm trying to learn how to set it up. IMG-0497.JPG

    What does this group recommend to get to my goals? Throw a very small cam in the stock motor, aluminum heads with stock bottom end, 3 speed vs 4 speed. I'm on a tight budget from the boss and she's losing her patience with this project before I even started the engine swap!
  2. Strictly Attitude

    Strictly Attitude solid fixture here in the forum

    Welcome aboard! Good heads with a matched cam will be very enjoyable. Better heads milder cam. Whats the Budget like?
  3. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum


    When money is tight I am a big fan of factory Cast Iron Heads.
    There really was no Bad Stock cast Iron Big Block Chevy Cylinder Head.
    Each was engineered to do a specific purpose.
  4. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

  5. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    A 700 R4 is Ok.
    In stock Form they can take only 300 Hp and 375 ft/lbs torque.
    To beef up and take 450 hp max and about same torque level it will cost $2k.
    Build it yourself.
  6. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    4L80E is better.

    Turbo 400 works nice on the street with highway gears.
    Capable of handling 800 Hp.
    Very low cost to rebuild.
    Drag race strength there if you pursue power.
    Ditto for 4L80E overdrive.
  7. Arden

    Arden Member

    Thanks, I can tell this is a great place with a whether of information. It seems fouls are a dying breed with Facebook, but with all the misinformed and difficult to search information I think this is a better place for me.

    3-4k is what I’m trying to work with, well minus the $20 I chipped in for operating costs.

    I was re-reading the bolt on 230 HP article and besides them not using cast exhaust manifolds and a single plane, that set from trick flow might work for me. I read Grumpy talking about the hidden costs and fallacies in these magazine articles designed to sell parts. Are you guys aware of any pitfalls in this one?


    Seems like a 113cc combustion chamber and the stock dished pistons would have the same compression as my 781 heads have now. I haven’t done the math but for some reason 8:1 sticks out.

    Obviously the cast exhaust manifold will be the choke point, do I want to run a 2.5 inch exhaust and how much would I be leaving on the table. As I mentioned I’m sue I’ll still be happy with the results.

    I have played the expensive game of always having enough money to do it right the second time, and I’m trying to learn my lesson. So just for ease and simplicity I think a marched top end kit would be my best bet. Do you guys have any recommendations to meet my goals? I looked at the 100cc Edelbrock heads which would raise the compression some, but I read their cams are just based on old school cams like the LS6 grind. With this technology constantly advancing and improving I want to make sure I’m picking the best matched components.
  8. Arden

    Arden Member

    I still may use the 400 I have, I just thought the 3.07 gears were a bit still high in the rpm range at 70. I know the big block has the torque not to lug down low but I figured long term obit drive would let me enjoy it a little more.

    I really struggled with yhe overdrive decision, ultimately I didn’t think I wanted the amount of torque to tear apart a 700r4. The added cost, weight, driveline loss, mechanical speedo adapter, stand alone computer and TPS set up for the carb didn’t make sense for my application, but if I had faith the boss would enjoy manually shifting it I may have swung different.
  9. Arden

    Arden Member

    How much can you shave off the 781 heads to bump compression. Is 9.5:1 doable? Would I notice the weight savings and handling difference if the cast heads were retained and freshened up? I’m not auto crossing or drag racing it, I’m too old for that.
  10. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    boosting the compression significantly by milling the heads, on any BBC,
    is not in my opinion worth the effort and cost vs the potential resulting gains.
    if your going to go the higher compression piston route you may as well go to either a .030-.060 over bore longer connecting rods and a 4.25" stroke crank.
    I posted more links with related sub-links above
  11. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    781 heads are enough to cause that 700R4 to fail blow up.
    Trickflow right away.

    Pontiac Trans Am guys have tried the 700R4.
    One guy with a 455 blew up the 700R4 doing a burnout in his driveway.
    20 feet later Kaboom.
  12. Indycars

    Indycars Administrator Staff Member

    I wouldn't worry about your 700-R4, Brain is all about the full blown race car that hardly ever
    sees the street. Do your research, upgrade those weak links and enjoy that OD drive transmission.
    I'm enjoying my 200-4R trans with OD, I love running a 3.7 rear gear and motoring down the
    highway at 1900 rpm doing 70 mph.

    No no no, not going to happen!!! I'm running a 2800 rpm stall converter and have absolutely no problems
    on the highway at 1900 rpm. Beside you have a lockup torque converter which takes the TC out of the
    equation. Even without the Lockup TC you will have no problem other than possibly heat. It's a good chance
    that you will need a transmission cooler. Since you have more room that I do, go with a cooler and fan. I
    have limited room for much of anything, but I did find room for a cooler and remote trans filter. Filter will
    be coming soon and is not in the photo below.

    I've had some comments and concerns about running rigid tubing and suspect they might be right, so you
    might want to run some kind of flexible hose instead. Do think about a transmission temperature gauge.

  13. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    I am a Real Mechanic.
    That means I support my Family with earnings fixing cars and trucks.
    I do Claim that title.

    I can run circles around you with transmissions.
    I do not need Google
  14. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    Got alot to show me yet.
    Race Fast.
    Zero Failures
  15. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    No Musclecar from 1961 to 1974 had Overdrive.
    How did they do it ?
    A few ran box stock 10s in the 1/4 mile and street driven.
  16. Strictly Attitude

    Strictly Attitude solid fixture here in the forum

    I have a 700r4 runs great but allot of money invested the 400 with highway gears is a good combo if you already have it. I like AFR heads personally. But I am a small block guy so I can't toss to much info at the bbc from personal experience.

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