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RE: [Cadillac_Performance_Association] Re: The '49-'62 V8... anything out there?

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  • Jerry Brown
    Actually I was speculating about just milling the 500 heads to get the increased compression ratio. Since the engine would be out of the car its no big deal to
    Message 1 of 25 , Dec 12, 2004
      Actually I was speculating about just milling the 500 heads to get the
      increased compression ratio. Since the engine would be out of the car its no
      big deal to pull the heads and have a valve job done and to mill them for
      increased compression...So long as you don't booger up the valve train
      ratios. It seems to me that if you mill the heads, say .040, that it would
      drop the head lower with respect to the valve train i.e., closer to the
      center of the camshaft, and might result in any of a number of unintended
      results.
      In order to keep everything in the same ratio you would have to account for
      being .040 closer. Seems to me that pushrods that are .040 shorter should
      compensate or taking .040 off the top of the valve stem might as long as the
      keepers would still fit. Doesn't seem right that you wouldn't have to do
      anything but mill to do the job right. Likewise decking the block would have
      the same result of moving the head closer to the center of the cam. I guess
      the right question is can milling or decking be done without unintended
      catastrophic consequences and if so how should one compensate for the
      changes.

      Jerry Brown


      -----Original Message-----
      From: jvandecreek25 [mailto:jvandecreek@...]
      Sent: Sunday, December 12, 2004 1:15 PM
      To: Cadillac_Performance_Association@yahoogroups.com
      Subject: [Cadillac_Performance_Association] Re: The '49-'62 V8...
      anything out there?




      --- In Cadillac_Performance_Association@yahoogroups.com, "david
      brode" <dbrode@h...> wrote:
      >
      > Jerry,
      >
      > The '74-'76 500s have 120+ cc chambers and a very small dish. If
      the
      > bores look good, you could just deck the block for a .040" or so
      > assembled quench, and whack the heads to get to *maybe* 9.5-1.
      Fyi -
      > KB makes no dish flat tops for it if it needs bored [which I doubt
      it
      > will].
      >
      > Another option would be dished KB designed for the early heads.
      They
      > give 10-2-1 or so with the '68-'73 heads [76cc]. Another option is
      to
      > use 107cc 425 heads on your shortblock. They'll put you a little
      over
      > 9.5-1. The 425 heads don't flow as well as yours, but a little
      work
      > and they'll do ok. The 76cc heads flow better than yours, btw, but
      > not much in stock form. More fyi - 2.11"/1.66&1.77" pontiac valves
      > fit the 107 and 120cc heads perfectly. For larger valves on the
      76cc,
      > aftermarket valves are available from the caddy
      > parts vendors.
      > Dave


      I'm looking for about 9.5:1 CR to help out performance. I know the
      best way to go is usually different pistons but I'm trying to keep
      the costs reasonable.
      Jerry Brown


      Jerry wanted to keep the costs reasonable, to "deck the block "
      will require a complete disassembly, and is hardly a way to keep the
      cost down, and as he stated he did not want to get into piston
      changes.
      I made my recommendation based on the premise that he wanted an
      inexpensive power increase for a engine that was going into a street
      rod, no it is not the 'ultimate' performance build up, but if it is
      not being used as a race car, there is no need to pursue a lot of
      expensive modifications that are unnecessary for strong street
      performance. Jessie








      Yahoo! Groups Links
    • david brode
      jvandecreek25, [bottom post] ... Al ... I have never CC d a pair myself. Al claims they re 96cc, iirc. Other experts claim 107cc. Dave
      Message 2 of 25 , Dec 12, 2004
        jvandecreek25,

        [bottom post]

        <dbrode@h...> wrote:
        > >
        > > jvandecreek25,
        > >
        > > The 425 heads will not gain near that much in compression. It has
        > > been said that they are 96cc, but I believe they are more like
        > 107cc or so. That figure comes from experts that I trust.
        > >
        > > CR on a stock engine can vary. Assuming a stock late 500 is 8-1,
        > and
        > > the heads are 120cc, the 13cc reduction in combustion space would
        > > raise the CR to 8.7-1. Assuming the stock engine was 8.5-1, the
        > > change would give 9.25-1.
        > >
        > > It would take a change in combustion space of apx 27.5cc to raise
        > > compression of an 8.5-1 engine to 10.5-1.
        > > Dave
        >
        > After I posted I realised I had over-shot on the amount of
        > compression increase, the figure I gave was one I had seen posted
        > elsewhere,and I never took time to confirm it.
        > However the figure for the 40 hp increase did come directly from
        Al
        > Betker of MTS,one of the most experienced Cadillac builders to be
        > found.
        > If this 40 hp improvement comes from an increase to only 9.25-1,
        > then so much the better.

        I have never CC'd a pair myself. Al claims they're 96cc, iirc. Other
        experts claim 107cc.
        Dave
      • david brode
        Jessie, [bottom]
        Message 3 of 25 , Dec 12, 2004
          Jessie,

          [bottom]


          <snip

          > Jerry wanted to keep the costs reasonable, to "deck the block "
          > will require a complete disassembly, and is hardly a way to keep
          the
          > cost down, and as he stated he did not want to get into piston
          > changes.
          > I made my recommendation based on the premise that he wanted an
          > inexpensive power increase for a engine that was going into a
          street
          > rod, no it is not the 'ultimate' performance build up, but if it is
          > not being used as a race car, there is no need to pursue a lot of
          > expensive modifications that are unnecessary for strong street
          > performance. Jessie

          Well, the reason I suggested decking the block for a tight quench and
          whacking the heads a bit, was because he said that money was an
          issue. Decking the block 20-30 thou costs just $65-$80 around here.
          Cutting the heads .050" or so would be a few more bucks, but not too
          much. Of course, once it's apart, hot tanmk, cam bearings, etc would
          cost him some. Personally, I would want to ring and bearing it
          anyway.

          The 425 head swap might be a much better bang per buck, I admit. As I
          see it, for a '74-'76 500, other than the 425 heads, the only other
          affordable option is to change to the dished KBs and 76cc heads to
          get any decent compression increase. Even the true flat top KBs on
          the 120cc heads aren't going to gain much over the very small dish
          stock late pistons.
          Dave
        • Preston III
          I ve never decked the block, or shaved the heads of a Caddy engine, but if it s anything like a Chevrolet small block, there s a limit that you can go before
          Message 4 of 25 , Dec 12, 2004
            I've never decked the block, or shaved the heads of a Caddy
            engine, but if it's anything like a Chevrolet small block,
            there's a limit that you can go before you have to do some
            machining to the intake manifold too. I expect that if you
            go past a certain extent, then you'll be in for spending
            even a few dollars more!

            Don't forget to inquire as to whether the changing geometry,
            and clearances of the intake/head surfaces may require a
            specific gasket, such as something extra thick.

            Also, in a true performance application, you may consider
            port matching the intake manifold to the intake side of
            the cylinder heads, as this is the dimension that will change
            as you go shaving things.


            Preston III


            --- david brode <dbrode@...> wrote:

            >
            > Jessie,
            >
            > [bottom]
            >
            >
            > <snip
            >
            > > Jerry wanted to keep the costs reasonable, to "deck the block "
            > > will require a complete disassembly, and is hardly a way to keep
            > the
            > > cost down, and as he stated he did not want to get into piston
            > > changes.
            > > I made my recommendation based on the premise that he wanted an
            > > inexpensive power increase for a engine that was going into a
            > street
            > > rod, no it is not the 'ultimate' performance build up, but if it is
            > > not being used as a race car, there is no need to pursue a lot of
            > > expensive modifications that are unnecessary for strong street
            > > performance. Jessie
            >
            > Well, the reason I suggested decking the block for a tight quench and
            > whacking the heads a bit, was because he said that money was an
            > issue. Decking the block 20-30 thou costs just $65-$80 around here.
            > Cutting the heads .050" or so would be a few more bucks, but not too
            > much. Of course, once it's apart, hot tanmk, cam bearings, etc would
            > cost him some. Personally, I would want to ring and bearing it
            > anyway.
            >
            > The 425 head swap might be a much better bang per buck, I admit. As I
            > see it, for a '74-'76 500, other than the 425 heads, the only other
            > affordable option is to change to the dished KBs and 76cc heads to
            > get any decent compression increase. Even the true flat top KBs on
            > the 120cc heads aren't going to gain much over the very small dish
            > stock late pistons.
            > Dave
            >
            >
            >
            >
            >




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          • david brode
            Jerry, I ve only seen a few late 500s apart, but they all were pretty decent as far as deck to piston. Assuming you have eom pistons and they re good shape,
            Message 5 of 25 , Dec 12, 2004
              Jerry,

              I've only seen a few late 500s apart, but they all were pretty decent
              as far as deck to piston. Assuming you have eom pistons and they're
              good shape, and a 40-50 thou gasket is used, a .020" to *maybe .025"
              deck cut will give you a nice tight assembled quench. El-cheapo cast
              replacement pistons are often 20+ thou shorter than oem. I would
              shoot for 040" assembled quench, regardless. Experts use either
              Felpro of Corteco gaskets. The Coretcos are a little better, but
              thicker, btw. .044"-.048" installed, iirc. You may need to stick the
              piston out of the hole a bit wioth those. The 472/500 heads can be
              cut way down. 050" is nothing on those, afaik. The 425 heads' deck
              isn't as thick, and experts say not to cut them much over 040".

              As far as rocker geometry, you can use shorter pushrods. You can also
              have a good stock cam re-ground, and that'll reduce the base circle a
              bit. Maybe enough to make up for the head/block cut. Most of the
              caddy parts vendors offer re-ground cams, btw, but most grinders will
              do one for you if you have a decent stock core. A note on that; most
              grinders want to use profiles with 10+ extra exhaust duration. Afaik,
              it's not needed on a caddy, esp with the 76cc heads. Even the 120cc
              heads' stock exhaust port flows well enough to allow same duration on
              intake and exh. Some experts even say that when ported, the caddy
              heads flow so well on exhaust side that they use a little less
              exhaust duration!

              As far as higher lift cams, you may need to snip a little from the
              top of the guides for clearance there. The '68 up seals are a joke.
              You can use the normal old umbrella valve seals from the '67 429
              caddys. SBchevy springs can be used, but you'll need to get creative
              with shimming. The caddy springs are very tall. The new behive
              springs offered for fords and LS1 chevs work better, with a retainer
              change, as they fit the caddy spring pad, and are taller than std sbc
              springs. If you have a freindly machine shop, they'll probably have
              some larger diameter used retainers from something that'll fit the
              behive springs. Just make sure they fit with the 11/32" valve
              keepers. Unlike the sbc or behive springs, larger o.d. springs will
              require pricey spring seats and more machine work. If you don't have
              a machine shop that you can trust, you might want to buy a spring
              package from one of the vendors. If you use stock rockers, choose a
              cam grind with nice slow ramps, as quick ramps are hard on the stock
              stuff. When cam shopping, make sure to tell them that you want slooow
              ramps. Fast ramps are hard on the stock T pedistals and rockers.
              Dave

              Brown" <jerome@p...> wrote:
              > Actually I was speculating about just milling the 500 heads to get
              the
              > increased compression ratio. Since the engine would be out of the
              car its no
              > big deal to pull the heads and have a valve job done and to mill
              them for
              > increased compression...So long as you don't booger up the valve
              train
              > ratios. It seems to me that if you mill the heads, say .040, that
              it would
              > drop the head lower with respect to the valve train i.e., closer to
              the
              > center of the camshaft, and might result in any of a number of
              unintended
              > results.
              > In order to keep everything in the same ratio you would have to
              account for
              > being .040 closer. Seems to me that pushrods that are .040 shorter
              should
              > compensate or taking .040 off the top of the valve stem might as
              long as the
              > keepers would still fit. Doesn't seem right that you wouldn't have
              to do
              > anything but mill to do the job right. Likewise decking the block
              would have
              > the same result of moving the head closer to the center of the cam.
              I guess
              > the right question is can milling or decking be done without
              unintended
              > catastrophic consequences and if so how should one compensate for
              the
              > changes.
              >
              > Jerry Brown
              >
              >
              > -----Original Message-----
              > From: jvandecreek25 [mailto:jvandecreek@c...]
              > Sent: Sunday, December 12, 2004 1:15 PM
              > To: Cadillac_Performance_Association@yahoogroups.com
              > Subject: [Cadillac_Performance_Association] Re: The '49-'62 V8...
              > anything out there?
              >
              >
              >
              >
              > --- In Cadillac_Performance_Association@yahoogroups.com, "david
              > brode" <dbrode@h...> wrote:
              > >
              > > Jerry,
              > >
              > > The '74-'76 500s have 120+ cc chambers and a very small dish. If
              > the
              > > bores look good, you could just deck the block for a .040" or so
              > > assembled quench, and whack the heads to get to *maybe* 9.5-1.
              > Fyi -
              > > KB makes no dish flat tops for it if it needs bored [which I doubt
              > it
              > > will].
              > >
              > > Another option would be dished KB designed for the early heads.
              > They
              > > give 10-2-1 or so with the '68-'73 heads [76cc]. Another option is
              > to
              > > use 107cc 425 heads on your shortblock. They'll put you a little
              > over
              > > 9.5-1. The 425 heads don't flow as well as yours, but a little
              > work
              > > and they'll do ok. The 76cc heads flow better than yours, btw, but
              > > not much in stock form. More fyi - 2.11"/1.66&1.77" pontiac valves
              > > fit the 107 and 120cc heads perfectly. For larger valves on the
              > 76cc,
              > > aftermarket valves are available from the caddy
              > > parts vendors.
              > > Dave
              >
              >
              > I'm looking for about 9.5:1 CR to help out performance. I know the
              > best way to go is usually different pistons but I'm trying to keep
              > the costs reasonable.
              > Jerry Brown
              >
              >
              > Jerry wanted to keep the costs reasonable, to "deck the block "
              > will require a complete disassembly, and is hardly a way to keep the
              > cost down, and as he stated he did not want to get into piston
              > changes.
              > I made my recommendation based on the premise that he wanted an
              > inexpensive power increase for a engine that was going into a street
              > rod, no it is not the 'ultimate' performance build up, but if it is
              > not being used as a race car, there is no need to pursue a lot of
              > expensive modifications that are unnecessary for strong street
              > performance. Jessie
              >
              >
              >
              >
              >
              >
              >
              >
              > Yahoo! Groups Links
            • david brode
              Preston, Good point. I ve decked a couple of them, but only 10-20. There was no need to cut the intake, or intake side of head. The intake may ride up on the
              Message 6 of 25 , Dec 12, 2004
                Preston,

                Good point. I've decked a couple of them, but only 10-20. There was
                no need to cut the intake, or intake side of head. The intake may
                ride up on the heads a wee bit, but unless a large amount of mat'l
                was cut, the ports can be re-aligned when port matching.

                If it was a problem, the intake could be cut, or the intake side of
                the head, although the valve cover bolt hole bosses there make it a
                bit tricky.

                I know that this issue is common, as the .015" shorter 6.735" forged
                olds rods are often used in the caddy. Another old combo is 7" olds
                rods and 403" olds pistons. That combo is 40-50 thou short, so I'm
                sure it's been addressed.
                Dave


                III <prestoniii2002@y...> wrote:
                > I've never decked the block, or shaved the heads of a Caddy
                > engine, but if it's anything like a Chevrolet small block,
                > there's a limit that you can go before you have to do some
                > machining to the intake manifold too. I expect that if you
                > go past a certain extent, then you'll be in for spending
                > even a few dollars more!
                >
                > Don't forget to inquire as to whether the changing geometry,
                > and clearances of the intake/head surfaces may require a
                > specific gasket, such as something extra thick.
                >
                > Also, in a true performance application, you may consider
                > port matching the intake manifold to the intake side of
                > the cylinder heads, as this is the dimension that will change
                > as you go shaving things.
                >
                >
                > Preston III
                <snipped
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