A guide to building the lil guy. The Mighty 300

Discussion in 'Small Block Tech' started by Joe65SkylarkGS, Oct 27, 2009.

  1. Jim Blackwood

    Jim Blackwood Well-Known Member

    OK this is not a P76 block. I was told it was when it was shipped in but this is the first time I've taken any actual measurements. Guess John will be surprised. With a tape I measured 7-3/4" from the deck to the main bearing bore. That bore measured out to 2.485" (no insert). Which puts the deck real close to 9" even. The BOPR has a deck height of 8.96 and a main size of 2.3" Looks very much like this is a Rover 3.5L block but I'll have to look at the liners to be sure. Mains in the P76 block are 2.5495"

    Sorry that doesn't answer the question, I've had no luck with online searches. Might find out by asking some of the UK guys or Aussies.

  2. Alssb

    Alssb Well-Known Member

  3. Jim Blackwood

    Jim Blackwood Well-Known Member

    I asked on MGE and so far it looks like the P76 deck is somewhere between .100 and .125" taller. Which means as long as a P76 intake had a reasonably thick flange it could be shaved to fit the 300.

  4. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    There is probably enough material on the heads to take a little bit of that off if the flanges start getting to thin as well?
  5. aznriceninja

    aznriceninja Member

    Hello, new to Buick forums, I don’t mean to Hi-jack the thread but my friend is selling me a 65 300 for $200 one caveat, he yoinked the crankshaft for his 3.9 Rover stroker for his 62 skylark. Is there anyone in the California area with a spare 300 crank they are willing to sell? Or would it be beneficial to me to consider a 350 crank swap? I’m not looking for too crazy of a build considering this is for a possible future 4x4 Willy’s wagon
    300sbb_overkill likes this.
  6. Taller than a 215 engine or taller than a 300 engine?
  7. Jim Blackwood

    Jim Blackwood Well-Known Member

  8. Jim Blackwood

    Jim Blackwood Well-Known Member

    Got my heads back Saturday, here are some photos. Basic TA bare heads, no port or chamber work, standard sized seats. They have beehive springs as you can see, 1.6 and I think 1.9 intakes but I'd have to measure. I might have cut them a little over that. (the valve heads) The valves are titanium and had to be shortened, in the last photo you'll see the hardened steel lash caps that are required. Fitted with umbrella seals to help lubricate the valve stems. A light skim cut on the mating face of the heads to remove any scratches. I'll CC them maybe this week, then when I get the bore size and deck dimension I'll be ready to finalize a piston order.

    Spring pressures are about 145 seated and 350 at 1/2" lift, which should be acceptable for either a solid flat tappet or a solid roller I believe. Shooting for 7-7.5K without valve float.

    Valve lift will be 1/2" or less, duration around 215 probably.


    IMG_0009.JPG IMG_0010.JPG IMG_0011.JPG IMG_0012.JPG
  9. Joe65SkylarkGS

    Joe65SkylarkGS 462 ina 65 Lark / GN

    Good stuff in here guys
  10. Mart

    Mart Gold level member

    I like those heads, titainium valves & beehives. Looking good Jim.
    Last edited: Jun 30, 2020

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