quick clutch size question: is a 70 350 11 inches?

Discussion in 'U-shift em' started by Clanceman427, Sep 17, 2012.

  1. Clanceman427

    Clanceman427 Hardtops need not apply

    Some background: I'm retrofitting a 71 Buick 350 engine from a 71 Skylark into my 64 Special. I'm also converting the 64 Special to a manual 4 speed. So, I purchased a flywheel from NAPA for a 71 Skylark with a 350. I also purchased the clutch kit for 71 Skylark with 350 BUT kit has the fine-spline clutch. I'm retrofitting a coarse-spline Saginaw 4 speed. So I returned the 71 clutch kit and thought I was smart to order a 68 Skylark 6 cylinder 3 speed clutch kit because that would assure the coarse spline clutch. It was, but I think the 68 parts are a 10.5" clutch, while my flywheel is an 11" clutch (the 68 pressure plate mounting holes' bolt circle was too small for my 71 flywheel).

    Just want to see/confirm that if I instead order the clutch kit for a 1970 Skylark with a 350 I'll get the coarse spline clutch and the proper 11" clutch size (sorry but I don't recall if the NAPA had the details of the clutch diameter on their computers). So I'd like to know if my plan would work.

    Nothing fancy or high power with my car it's only a stock skylark 4 barrel motor so I'm not looking for Centerforce or other stronger aftermarket parts.

    Thanks for any help.
     
  2. buick64203

    buick64203 Just plum crazy Staff Member

    Generally speaking, a small bock will take a 10.5 and a big block will take an 11". You should just be able to tell the guy behind the parts counter that you need an 11" clutch with a coarse spline disc.
     
  3. Clanceman427

    Clanceman427 Hardtops need not apply

    I just measured the 68 clutch and pressure plate: they are 10.5 inches. The flywheel mounting bolt circle for the 6 bolts is considerably bigger. I checked my NAPA receipt and it says 1971 Buick Skylark 5.7L
    part# BK_600-5151

    Only thing I can think of is that maybe in 1971 when GM converted all manual transmissions to the fine spline input and output shafts, they also converted all V8's(small and big) to the 11 inch clutch size.
     
  4. buick64203

    buick64203 Just plum crazy Staff Member

    The holes on my 11" flywheel measure 12 5/8"
     
  5. Clanceman427

    Clanceman427 Hardtops need not apply

    Thanks I'll see what my flywheel measures. Now I'm considering returning my 11" flywheel, because I've already buggered up my pilot bushing which came with the clutch kit (includes clutch disk, pressure plate, throw out bearing, and pilot bushing) and I'd feel bad returning that. Last night I tried out the bronze pilot bushing, and after some strong hammer blows I stopped myself (been reading all the threads regarding this). I was only able to insert it about .23 inches then took it out and said "lets change plans". My 71 Skylark 350 crank is drilled for the bushing, but I think the bushing itself is a little oversized on O.D. as we know. The NAPA bushing does not attract a magnet (good news) and it does slip over my Saginaw input shaft smoothly. Here's how the NAPA bushing measures out of the box:

    O.D. 1.0965 inches
    I.D. .589 inches
    length: .756

    I plan to clean up the hole in the crank just to knock off the surface rust, then measure it, and then establish a target O.D. on my bushing to be about 0.0005" smaller then that. Then I'll have my bushing turned down.

    I'll talk to NAPA today to see if a 1970 Skylark 350 flywheel is 10.5" or 11". I'll probably swap flywheels I'm thinking.
     
  6. 87GN_70GS

    87GN_70GS Well-Known Member

    I was under the impression that all small-block bucks were 10.4" (or 10.5" depending on who's measuring) except the early 70's 350 Jeep, which was 11" . My '70 350 was 10.4" .
     
  7. Clanceman427

    Clanceman427 Hardtops need not apply

    Thanks Scott.

    UPDATE: I worked with the store manager of my NAPA (very helpful guy) and we walked thru the issue. Turns out he had a new paper catalog from their new flywheel supplier, and when we found the correct 10.5" flywheel part number in that paper catalog and plugged it into the NAPA computer, low and behold there it was, the correct flywheel. Obviously the computer system needs to be updated. I'll know more later today when I do my exchange as far as part numbers. Cost I think was still around $220.00 for the flywheel. I explained how I wanted to buy a separate pilot bushing since I had buggered-up the one that came with my clutch kit (from hammering on it and scratching the I.D. while removing it). I mentioned how I will need to turn the O.D. to fit the Buick crank and he said he wanted to get to the reason why his part won't fit out of the package properly, so we'll see if we can make any headway with that too.
     
  8. Clanceman427

    Clanceman427 Hardtops need not apply

    [HR][/HR]sad to report none of Napa's suppliers provide this flywheel. Even the books listed the chevrolet style part number. Next question : are the Buick pressure plates and clutch disk unique also? Or will my chevrolet parts work?
     
  9. 87GN_70GS

    87GN_70GS Well-Known Member

    Yeah I was thinking to myself I've never heard of a mainstream vendor supplying an off-the-shelf flywheel for a 350 or 455.

    The answer to your question is: clutches are not Buick-specific. Almost any clutch made for a GM application will work.
     
  10. Clanceman427

    Clanceman427 Hardtops need not apply

    Good news, thanks Scott. Yeah, the ironic thing is that I originally went into the NAPA looking ONLY for a pilot bushing, and when the store person said "looks like we have the flywheel for that model too...." and I said Really?? Well how much? Then the ball got rolling....but turns out they over-reached and assumed the same Chevrolet parts interchange with the Buick parts.
     
  11. Jim Blackwood

    Jim Blackwood Well-Known Member

    I bought a SBB flywheel and it has the hole pattern for the 11" clutch also, and I think the wheel is OEM. So Buick must have used an 11" at some point with the small blocks. Anybody have a clue what year that was and what model?

    Jim
     
  12. 87GN_70GS

    87GN_70GS Well-Known Member

    Yes. Used on Jeeps (Grand Wagoneer? )in the early 70s with the 350 SBB. That is a HEAVY flywheel though, like 50 lbs vs the stock 35 lbs
     
    knucklebusted likes this.
  13. knucklebusted

    knucklebusted Well-Known Member

    So, it would take longer to spin up but it wouldn't bog down. Just what a Jeep needed.
     
    87GN_70GS likes this.
  14. agetnt9

    agetnt9 Agetnt9 (Dan)

    The pilot bearing will give you some trouble i think.
     
  15. knucklebusted

    knucklebusted Well-Known Member

    Why so? You talking Jeep or Buick in general?
     
  16. agetnt9

    agetnt9 Agetnt9 (Dan)

    Buick, not the same as the rest size wise
     
  17. knucklebusted

    knucklebusted Well-Known Member

  18. agetnt9

    agetnt9 Agetnt9 (Dan)

    The crank may or may not be the proper size and depth. As in the notes below #4
     
  19. knucklebusted

    knucklebusted Well-Known Member

    That is only listed for the extended pilot bushings, not the standard one.
     

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