What year Big Block Buick to Build?

Discussion in 'Buick FAQ' started by Nicholas Sloop, Jan 25, 2007.

  1. Nicholas Sloop

    Nicholas Sloop '08 GS Nats BSA runner up

    If you are questioning what year motor to start with for your big block Buick (BBB) build-up, this thread is for you. (If you are looking for a ’70 SF motor to build “because it has 370 HP,” you REALLY need to read this thread!)

    I’ll cut to the chase and give you the answer right off. With one major exception, it really does not matter. The exception is the 75-76 heads. They are junk, due to their compression-killing open combustion chambers. Everything else is 95% comparable between every BBB ever made.

    If you are concerned about factory horsepower levels, the fact is that the iron “hard parts” (block, crank, rods, heads, and manifolds—the stuff you might re-use in a rebuild) of a BBB have very, very little to do with the power output of the engine. Now, as Paul Harvey would say, here is the rest of the story…

    Crank and rods
    All BBB cranks and rods are identical, equal, and interchangeable.

    1967 through early 71 blocks have a smaller oil pick-up passage. This is easily drilled out during machine work. 75-76 blocks are slightly heavier (about 10 lbs.) For anything under 500HP, this is just dead weight. And there is only a small horsepower window between where using a 75-76 block would be beneficial before you get to the point where you need a girdle no matter what.
    If they pass a sonic check, 400-430 blocks CAN be bored out to 455, but you better send your machinist a Christmas card after that. :)

    As stated, 75-6 heads are junk, due to the open combustion chambers. For the drop in compression between 70 and 71, most of the change was done through a deeper dished piston. The 71-74 heads have slightly larger combustion chambers, but not by much. They flow just a well as earlier heads. The emissions passages in 72-up heads do not affect flow. 67 and early-68 heads are known as “big port heads,” due to slightly larger intake passages. Untouched, they do flow a little better than later heads, but if you are doing any porting, it is just a “head start” for the porter. Any port job will go way beyond the flow of big port heads.
    Stage 1 heads are just the same castings as regular heads of that year with larger valves installed. Any BBB head can become a “Stage 1 head.”
    67-69 BBBs oiled the valve train through oil passages in the block and heads, into the rocker shafts. 70-up oiled through the pushrods. You can use through-the-pushrod oiling on any BBB, but, 455 blocks continued to have this oil passage in the driver’s side of the block. So, if using early (67-9) heads on a 70-up block you need to block this oil passage, either in the block deck, or in the head. The passage is in the front rocker shaft pedestal, right next to the rocker shaft bolt hole.

    All intake manifolds will flow equally. As with the heads, any emissions passages added to later intakes do not affect flow. If you are putting a 67-71 intake on later heads, you need to block the AIR passages at each corner of each head, as the earlier intakes don’t cover them. There are also issues with the exhaust crossover changing in, I believe, 72. Some (all?) 67 intakes do not have the cast-in bosses to mount the throttle cable bracket.
    67-69 heads use 3/8” intake bolts and 70-up use 7/16” bolts. Obviously, you use whatever bolts fit the heads. The bigger bolts go through the bolt holes in the earlier intakes just fine.
    All exhaust manifolds flow equally. Some 67 manifolds do flow a little better, but not a big difference.

    If I missed anything, or others have a different take on any of this, chime in!
    Last edited: Oct 25, 2007
    PGSS likes this.
  2. DaWildcat

    DaWildcat Platinum Level Contributor

    Nicely done, Nicholas! :beer

  3. standup 69

    standup 69 standup69

    is that 50 lbs heavier a typo:Do No:
  4. Bobb Makley

    Bobb Makley Well-Known Member


    One of the biggest reason for useing a 75-76 block for us in high HP builds is lifter bore mateial the bores in MOST 75-6 blocks can be well over twice as thick. I broke a lifter bore in a 70 block 10 years ago and the bottom of the bore was less than .100 thick. I agree with the main girdle part but if you plan to be agressive at all with your cam whether it is a flat tappet or roller or if you plan to add a ta lifter girdle its better to start with good lifter bores.
  5. myriviera

    myriviera Well-Known Member

    Outstanding thread.....very well done.....
  6. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Nicely done. This should be a sticky in the FAQ forum, like my timing thread.
  7. NSAN1T

    NSAN1T Member

    so if I'm reading this correcltly..

    you would probably want to use a later model block, with either stock or moddified 67-74 heads. 75+ heads have too large of a combustion chamber?

    what if you had 75+ up heads, is there anyway to "close" the chamber by running domed piston or is there a valve clearance issue there?

    Just curious since I haven't gotten to go pickup or see my 455 yet.. already planning my rebuild :laugh:
  8. RG67BEAST

    RG67BEAST Platinum Level Contributor

    I do not have a 75/76 455 but the 70 & 71 block I have seem to have decent material for the lifter bores. Nice and even too. Same for the cylinders.
    I also have a 72 block with a few extremely thin bores (way under .100") and core shift. Even some the cyl. walls are real thin only on the one side of the cyl..
    If I was looking for a block I would pull the pan and intake to have a look at how much meat there is for the lifters and cyl. and check out how even it was cast regardless of the year just to be safe. I've worked in 2 foundries for 12 years. Cast iron and aluminum. Alot of things can happen.
    Freakazoid likes this.
  9. bob k. mando

    bob k. mando Guest

    75+ heads have too large of a combustion chamber?

    yes, but the bigger problem is that they have absolutely no quench / squish area. that's why they're called 'open'.
  10. Nicholas Sloop

    Nicholas Sloop '08 GS Nats BSA runner up

    Thanks, Larry. That was the whole point. I PM'd Jim W. to ask him to make it a sticky, referrencing your timing thread, and he said sure, but put in in the FAQ section. I will put my original post there, but I'm not sure if I can move the whole thread...
  11. Nicholas Sloop

    Nicholas Sloop '08 GS Nats BSA runner up

    You are reading correclty. There is no way to "fix" 75-6 heads. There are no domed pistons for Buicks. Only flat-tops, which can get you serious compression with good heads, and deck and head milling. The block issue is pretty much a non-issue. Unless you are in the high horsepower range, or running a big cam (see Bobb's post above), the later block is really not an issue.
  12. Nicholas Sloop

    Nicholas Sloop '08 GS Nats BSA runner up

    I think we are saying the same thing here, just using different words...
  13. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Any of the moderators can move the entire thread and make it a sticky for you. Just PM one. It should be in the frequently asked questions (FAQ) Any time someone asks the question, just link them to your post. That's what i do with Timing questions.
  14. Nicholas Sloop

    Nicholas Sloop '08 GS Nats BSA runner up

    Me too, unless you beat me to it... :)
  15. Nicholas Sloop

    Nicholas Sloop '08 GS Nats BSA runner up

    No, not a typo.
  16. Jim Weise

    Jim Weise 1000+HP

    Just a note..

    Always sonic check a 455 block--- always..

    Don't assume because it has no visible core shift, or because it is a certain year block, it's good for a high HP build..

    I have a number of sonic sheets from 76 standard bore 455 blocks, that look perfect in the lifter valley, but have core shift in the passenger side bank, particularly bad on the backside of number 4 and 6 hole, in line with the pin.

    That said, I also have a couple '76 race blocks that were over .200 everywhere, and that is super for a 455 production block.

    Moral of the story.. sonic check-- always.. it's the best 40-75 bucks you can spend, and it should be done before anything else is attempted.

  17. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

  18. htwhls19

    htwhls19 Well-Known Member

    This is a very nice sticky.

    I have one question about the oiling schemes on the different blocks/heads. I'm planning on using 1970 455 heads on a 1969 400 Block....problem or no problem?
    So will that work fine or do I have to mod something slightly?

    Thanks In Advance.
  19. Nicholas Sloop

    Nicholas Sloop '08 GS Nats BSA runner up

    Will work fine. Just use 70-up lifters, pushrods and rockers.
  20. DaWildcat

    DaWildcat Platinum Level Contributor

    I would suggest blocking the oil feed holes in the deck that used to oil the old-style rockers, rather than relying on the head gaskets to seal them up.

    Last edited: Nov 4, 2007

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