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Main cap girdle's....do they work??

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  • #31

    Re: Main cap girdle's....do they work??

    Re: Main cap girdle's....do they work??

    At least in SBF applications, the girdles really help alot.
    By design they spred the stress over a larger area, thereby lessening the stress in the main webbing, whioch is quite weak in the factory castings.

    It depends on the motor in question, the specific block used, and what it's purpose will be, but in my opinion they do help.

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    • #32

      Re: Main cap girdle's....do they work??

      Re: Main cap girdle's....do they work??

      I know a lot of the Big Block Buick guys swear by a block girdle them once the engine crests about 500HP. I plan on using one on the next 455 I build.
      http://taperformance.com/block.htm
      Escaped on a technicality.

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      • #33

        Re: Main cap girdle's....do they work??

        Re: Main cap girdle's....do they work??

        Nice link. High quality stuff.

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        • #34

          Re: Main cap girdle's....do they work??

          Re: Main cap girdle's....do they work??

          You guys must not have built many serious small Fords. They split all the time.
          you must not have neutral balanced them and spun them to high LOL

          stock or stock rebuilds most likely have a 50oz imbalance or maybe even a 28....do a nice zero and a lot of your worries go away, but not completely
          I can show you some nice chucks from a neutral balanced small block Ford with a stock block that pushed a little 62 Sprint to 6.80s in the 8th mile. Third in a series of dead stockers, one per year. The last one split around the front main and cam gear. After the pan was removed, that chuck with the oil pump slid right off the front of the crank. Cute. It's a garage wall trophy now. That guy now runs a Dart block - no more problems with leaving parts on the track. Mostly they seem to like to split up the webs to the cam tunnel. I think all Ford stock blocks have some issue somewhere - 351Cs like to split the bottom of the bores after they cross the 500+ HP mark. 351W are rumored to make it to around 600 and 460 blocks have been known to go way up there. Stock blocks can just be a crap shoot - 4 run balls out and never a problem, 5th one barfs it's guts out at the first sneeze. I've run a bunch of 351Cs without big problems, my current block has more small cracks than California.

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          • #35

            Re: Main cap girdle's....do they work??

            Re: Main cap girdle's....do they work??

            Its not a concept - its an engineering fact. Any fastener like a bolt or stud is just a fancy spring, and the torque value is just a way to pre-stretch it. This is why for critical bolts like rod bolts, a stretch guage is the best way to torque them - you are stretching them an exact amount which gives you a known clamping force.

            Dowling is a great way to keep the main caps from moving if there is enough meat to do it in the main webs.

            Ford small blocks are fun. We have the remains of one in the shop with the crank broken in half, and the remains of another where the block is split right down the middle into two pieces. After removing the intake, and main caps, the block fell into two pieces. lol




            I'm not normally a big fan of girdles - although I'm sure they help some engines.

            If you buy into the spring concept for a bolt or stud it'll tell you that the fastener clamp load is all thats holding a main cap in position. Once you exceed the clamp the cap is free to move around fore & aft because the bolt holes are by necessity larger than the shank of the fastener. The fix for eliminating this free movement is a dowel pin. A pin positively locates the cap, and allows the fastener to only be required to handle vertical movement.

            The pins will not help a marginal main bulkhead - and that is where the girdle may help out - - although I'd pin the girdle to both the mains and the pan rail.

            And stock block small block Fords will eventually split no matter what at 450-500HP - just not enough metal down there

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            • #36

              Re: Main cap girdle's....do they work??

              Re: Main cap girdle's....do they work??

              I'm not normally a big fan of girdles - although I'm sure they help some engines.

              If you buy into the spring concept for a bolt or stud it'll tell you that the fastener clamp load is all thats holding a main cap in position. Once you exceed the clamp the cap is free to move around fore & aft because the bolt holes are by necessity larger than the shank of the fastener. The fix for eliminating this free movement is a dowel pin. A pin positively locates the cap, and allows the fastener to only be required to handle vertical movement.

              The pins will not help a marginal main bulkhead - and that is where the girdle may help out - - although I'd pin the girdle to both the mains and the pan rail.

              And stock block small block Fords will eventually split no matter what at 450-500HP - just not enough metal down there
              I was hoping you would weigh in here. I can't get anyone around here to dowel mine, I'd rather have that than anything. A girdle properly designed works well along with the dowels and a good main index bore or hone with studs. On a Y-block like an FE or B/RB Chrysler can be done with cross bolts and no girdle, but those dowels down there where the action is make a world of difference. Any one in the St Louis, MO have the stones to do this? I wish I lived up by you Barry, we would have it done.

              Stock block small blocks are on borrowed time at 500 hp. The A4 and World Products are the hot ticket there.

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              • #37

                Re: Main cap girdle's....do they work??

                Re: Main cap girdle's....do they work??

                Well, just a little update for y'all, block is now at the machine shop, I got the girdle fitted and all look's very good, my machinist was impresed, ;D he is going to clean up the parting face's on the block and cap's, dowel pin the cap's and re-align hone the block, plus a couple of other small operation's and he say's now I should be ready to let her eat!!!

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                • #38

                  Re: Main cap girdle's....do they work??

                  Re: Main cap girdle's....do they work??

                  A machinist / tool die friend of mine has recently been playing with a Ford small block.

                  He machined the tops of the main caps to make them flat for the girdle to sit on, except for an area right in the center at the top of the cap - there he left a square "peg" for lack of a better term sticking up about 3/16" of an inch - the peg is roughly 1/2" square.

                  He then machined the girdle to create "holes" for those "pegs" to fit into - with not much tolerance, on the order of .001" in any direction - he put the whole thing together with studs, hardened washers between the girdle and caps, hardened washers on top of the girdle, and arp nuts that came with the studs on top of those washers.

                  He's thinking out of the box - something he does quite well - and he enjoys testing his theories, I enjoy following along with his endeavors as well. This one seems feasible - he is not comfortable using dowels in a SBF as there just isn't much iron in those main cap webs as it is....

                  I don't have pictures to show - I know my description probably leaves as many questions as answers but - it will be interesting to see how this little sbf will work out - he's going to do some road racing with it this summer - he's putting a cam in it with an advertised power range of 3000 - 7500.
                  There's always something new to learn.

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                  • #39

                    Re: Main cap girdle's....do they work??

                    Re: Main cap girdle's....do they work??

                    A machinist / tool die friend of mine has recently been playing with a Ford small block.

                    He machined the tops of the main caps to make them flat for the girdle to sit on, except for an area right in the center at the top of the cap - there he left a square "peg" for lack of a better term sticking up about 3/16" of an inch - the peg is roughly 1/2" square.

                    He then machined the girdle to create "holes" for those "pegs" to fit into - with not much tolerance, on the order of .001" in any direction - he put the whole thing together with studs, hardened washers between the girdle and caps, hardened washers on top of the girdle, and arp nuts that came with the studs on top of those washers.

                    He's thinking out of the box - something he does quite well - and he enjoys testing his theories, I enjoy following along with his endeavors as well. This one seems feasible - he is not comfortable using dowels in a SBF as there just isn't much iron in those main cap webs as it is....

                    I don't have pictures to show - I know my description probably leaves as many questions as answers but - it will be interesting to see how this little sbf will work out - he's going to do some road racing with it this summer - he's putting a cam in it with an advertised power range of 3000 - 7500.
                    you never know, he may be on to somthing, you never learn anything if you don't try new thing's.

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