401 vs 425

Discussion in ''Da Nailhead' started by KDML, Nov 7, 2009.

  1. ahhh65riv

    ahhh65riv Well-Known Member

    I agree John. Almost all Nailheads will run flat above 5500 RPM. Conversly very few nailheads will make power or ever be reved above that anyway.

    Undoubtably now that I've said that, somone will post on and example of an exception that was probably done umpteen years ago, but again that will be one of the very few exceptions.

    Nailhead Nut- I am aware the timing curve is different between a 2x4 and single 4, but you are going to have to explain to me what makes it a completely different distributor. :confused:

  2. wkillgs

    wkillgs Gold Level Contributor

    I'll have to check my notes, but I believe the distributor used on the Dynaflow cars is the same as the 2x4 distributor. Both used 12* initial advance.
    I do have the 2x4 curves somewhere. Anyone have the Dynaflow timing curve?
  3. kilkm

    kilkm Well-Known Member

    Appreciate any info on timing curve you have. Currently my 401 has an Elelbrock 600 cfm performer series carb that I really like. My idea was to add another one with the 2X4 manifold. I've heard that nailheads like lots of CFM's so I thought 2 of them might be a good match for this engine. This is stricktly a show car so a big performance gain is not my goal. I've been told the 2nd four barrel only added 20 hp anyway. I'd love to get the endurashine carbs that Elelbrock makes, they'll look fabulous with the rest of the chrome under the hood. I have to score the manifold first. Missed out on a real nice Offy the other night, my computer messed up at the end of the ebay auction when I was trying to bid. I'd really like to have the Edelbrock manifold also, but I know they are really expensive. The last one I saw on ebay went for $811, and I don't want to spend that much. The Offy went for $266, I was furious my final bid didn't go through. A stock Buick manifold would be fine - if I could find one!
  4. 87GN@Tahoe

    87GN@Tahoe Well-Known Member

    what about a brand new eelco (edelbrock copy) for a around $425?
  5. wkillgs

    wkillgs Gold Level Contributor

    I looked up the distributors in the 1940-1974 Buick parts book...the 425 with 2x4 uses the same distributor as 60-63 with Dynaflow trans. However, according the Motor's service manual, they use different vacuum advance units.

    has 1960 and 1966 Chassis manuals in their Reference section. See the 66 manual for std 401/425, and the 60 manual for the Dynaflow (same as 2x4) timing curves.:TU:
  6. wkillgs

    wkillgs Gold Level Contributor

    That would be a much better choice than the Offy! The Offy simply doesn't perform well....
  7. Joe65SkylarkGS

    Joe65SkylarkGS 462 ina 65 Lark / GN

    Great info here.

    I say sticky this thread.

    Now Doc, what's this dual plane intake I'm hearing about?

    I have my first nailer and will be breaking into the engine this winter.

    I have alot of research to do i guess.
  8. wkillgs

    wkillgs Gold Level Contributor

    Joe, All Nailhead intakes are dual plane design.
    EELCO was working on a single plane, but he couldn't get it to flow well.
    Dual plane is the way to go for these engines!
  9. 1967GS340

    1967GS340 Well-Known Member

    Marty is still working on getting the single four barrel right and expects to have it ready soon.
    He has a thread on here for questions and him and Doc talked about it.
    Search for eelco or something and you should find the thread pretty recent.
  10. roostriz

    roostriz Well-Known Member

    So with a dual qaud on the 401 would you be better off recurving your distributor to the 425 dual quad curve?
  11. doc

    doc Well-Known Member

    Actually you would be better off using that advance curve with any carb or carb combo.... it is just a better performance spark pattern....
  12. doc

    doc Well-Known Member

    Joe, the ''Doc dual plane'' that i came up with a while back was just a simple effort to make the factory nailhead manifold better, because there was/is no good single 4 available on the after mkt. for the sq. bore carbs and in particular for my holley 3 bbl carbs....sooooo, as a simple experiment , I pulled the intake off my 64 riv, and cut the partitions out from between the FRONT and the REAR holes on each side , leaving the center divider intact to preserve the torque....
    I made absolutely no other changes, same intake, same carb, same tune up, ect...
    It made a big difference in the performance,,, you could feel quite a bit of increased performance at all speeds, gears, ect... I was amazed.... and wondered why Buick did not do that....
    Cost was minimal, effort was minimal, and the results were good,,, and the gas mileage was the same ,,, no changes there.....
    Then when i posted the info on the board , the guys started calling it a ''Doc dual plane'',,,,
    I used a sawsall with a short metal cutting blade and then followed up with a air die grinder and 6'' carbide burr... and finally , a sandpaper porting tool....
  13. kilkm

    kilkm Well-Known Member

    The EELCO manifold is best suited for Carter AFB's I'd like to use the Edelbrock Edurashine carbs (it's a show thing.) Anyone have a stock 2x4 manifold they want to sell, send me a PM.
  14. wkillgs

    wkillgs Gold Level Contributor

    The biggest difference between the standard and the 2x4/ Dynaflow curves is it gives more low-RPM advance that will boost performance.....
    The standard gives a total of 2-30 degrees mech advance, and the 2x4 gives 10-30 degrees.

    Anyone have a 64-65 Buick Service manual that shows the 2x4 advance curve?:Do No:
  15. CameoInvicta

    CameoInvicta Well-Known Member

    And the final result looks something like this :TU: ...

  16. doc

    doc Well-Known Member

    Yep,,,, cept mine aint that muckeldy dun color, it is red.....:Brow: :laugh: :Brow: :laugh:
  17. Joe65SkylarkGS

    Joe65SkylarkGS 462 ina 65 Lark / GN

    Doc thanks. When I'm ready I'll be requiring some input. Prolly this winter if Arties machine shop bud will hook me up.


    Please stick this thread boys!?!?!?
  18. CameoInvicta

    CameoInvicta Well-Known Member

    Cut me some slack Doc, it's still in primer :bla: ! I haven't decided if I'm going to repaint it the factory color, or go with an aluminum color, or wait for Marty to maybe release his intake. Until then it sits in the shop...
  19. telriv

    telriv Well-Known Member

    I see this reply so many times about the 2x4 timing curve verses the normal distributor timing curve. There's nothing special here guys. The standard distributor has 15* (30* at crank) built into the distributor with 2 1/2* initial advance. The 2x4 has 10* (20* at crank) and 12* initial. So, they both have full mechanical advance at 32* & 32/12* at full advance. The 2x4 comes in full at 200 RPM's sooner. They both have approx. 20* of vacuum built into them. The curve I like to run that gives me options for the fuel available is 11*built in (22* at the crank) & I can set my initial anywhere from 8*-14* which will give full advance from 30*-36* all in by 2400-2800RPm's. This all depends on the quality of fuel available in certain areas of the country. So with this set-up you have options available to you. I then limit the vacuum advance to 8*-12* so at no load cruising your at around 42* or so. Our "Nails" run about 10* cooler with the vacuum advance hooked up while cruising. Weather ported or manifold vacuum depends on cam selection. Stockers can run either ported or full vacuum. Hotter cams need full vacuum always.
  20. doc

    doc Well-Known Member

    Andy,,,,, There are a lot of choices out there,,,,:laugh: but you better not wait on that new manifold... need to get that puppy on there to pick up the power... You will like it.... trust me.... You did a better job on that one than I did on mine,,actually.... I still wonder why Buick did not do this.....:idea2: :idea2:

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