Block/Block Preparation for Procharger

Discussion in 'High Tech for Old Iron' started by dr, Dec 16, 2016.

  1. dr

    dr Well-Known Member

    Current combo between 9.5 and 10:1 ratio
    Milled eddy aluminum heads
    290 cam
    950 quick fuel carb.
    Dave small body HEI ignition

    12 bolt rear end 3:42 gears
    Trishield street strip converter
    I will obviously will get this all dialed in before I purchase Procharger.

    Goal 10.5 ET pump gas friendly Skylark. sub 700hp
  2. pmuller9

    pmuller9 Well-Known Member

    The fact that the crankshaft on a supercharged engine has to handle the power it takes to drive the supercharger added to the power output at the flywheel is sometimes overlooked.
    So lets say the engine puts out 650 HP at 7 lbs of boost.
    The supercharger can be using upwards of 70 HP at that level to drive it so the crank sees about 720 hp.

    The block will need a full girdle to survive the actual HP and torque.
    The compression ratio should be less than 9:1 depending on actual boost requirements.

    You may have already viewed this thread but it will give you good info.

  3. hugger

    hugger Well-Known Member

    I believe John JR has proven without a doubt that the full girdle is NOT a must for one to live, yes he runs aluminum rods and a simple Halo which is very effective and much easier to install, but he has put his car thru more punishment than most, and it has survived. My stock rod no girdle Shortblock was on 6lbs at 11.25 to 1 compression and didn't complain. Unless you are out there every week thrashing on it and spinning big rpm a girdle is just "extra" IMO anyway. I see no reason for less than 9.1 comp either. Maybe mine was a grenade pulled I was 3900lb 11.25 to 1 comp , 28 hot air setup on corn. I'm going to 93 pump this time around and will set compression around 9.75 which still leaves a large tuning window. If I was after some stupid number I would set it back on 11to1 or even more. But no need for that this time around.

    And I've heard all the arguments that the ones who don't run girdles are just lucky etc etc, but there so many fast BBB's out there that aren't girdled tho. How often are you going to load a 650+ hp 455 on the street for more than just a couple seconds? For no more time a true Street strip car sees under a hard load it's just not needed IMO . if we all succumbed to believing all the pitfalls of a BBB we probably wouldn't be able to crank it without it destroying itself every time. For a hard hitting hard launching bracket car that sees lots of exercise time yea those engines need reinforcing. Not looking for an argument BTW just pointing out another perspective.
  4. pmuller9

    pmuller9 Well-Known Member

    I appreciate another perspective.

    If the cam has an intake duration around 230* on a wide LSA for street/strip use with a supercharger then the compression is better at 9:1 or less with 91 octane pump gas.
    After all the base engine power doesn't have to be more than 500hp.
    I can understand a higher compression when using a long duration Bullet cam.

    I look at the girdle situation like this.
    A 650 HP engine may be OK at the beginning but dr may find that it is not enough to get the ET he wants at the track and may want to turn it up.
    It doesn't make sense not to spend the extra for a full girdle over the HALO and not have the extra margin of safety to protect the investment of the entire short block.
    The problem is finding a local shop that will do the girdle installation correctly.

    It is not necessarily just about a block cracking or not. It is also about engine longevity due to block stiffness.
    Add to the fact that all blocks are not equal.
    Just my opinion.

    Here's JW's opinion.
  5. hugger

    hugger Well-Known Member

    That's my biggest thing getting it installed correctly and the $ it takes to do so. I'm a big believer in Hard Blok, it's cheap, easily done and very effective. My block I ran was half fill, billet mains and studs. I wish I would have done a halo. It's no secret I like big cams and yes I did and will continue to run Bullet Cams, Richard and them guys do seem to go larger than most grinders. I certainly see where a mild cam will get you into cyl psi problems.
    I have no idea what HP I was at on mine it ran 10.80s at 120 NA and I just bolted the blower on so 900/950 maybe, I will say it was VIOLENT down low and pulled like crazy, it was a 259/267 615/615 on a 110lsa with a 4.10 gear.

    Dr are you opposed to running e85?
  6. Jim Weise

    Jim Weise 1000+HP


    Your spending what 3-5K for a blower and associated parts. So girdle cost has to be considered irrelevant at this point.

    So lets look at need:

    I agree that boosted motors load the parts over a longer period of crank rotation, thus limiting the hammering type stress that kills main webs. So you can push a bit harder with a blower/turbo than NA or with N2O.

    But should you?

    Consider it insurance should you get a bad tune, tank of gas or other mishap.

    I will not argue it's mandatory, I will argue it's prudent.

    The only downside of the girdle, installed as directed, is that it's my strong opinion that you cut the caps too much. Since 2014 all girdle installations at TSP have thinned the cross beams of the girdle .200 and left that material in the cap.

    Cutting the cap too much weakens it, and thermal stress causes it to pinch, even in motors that have not sustained any bearing failures or other abuse/extreme conditions.

    Thinning that girdle out is something I have wanted to do forever, but it was hard enough to find someone to put it on in the first place, let alone start machining on the new parts. But when I teamed with Ron in 2014, he actually brought it up.. after looking at previous installations.

    Not everyone agrees with this, but everyone is entitled to his/her opinion.

  7. Babeola

    Babeola Well-Known Member

    I would worry less about static compression and more about dynamic compression, quench and overlap in a street/strip application. Keep the DCR under 8:1 and have some negative cam overlap @.050" on pump gas premium. We run almost 10:1 static compression with an @ .050" intake duration of 224* at 20# of boost in our Cobra on 93 octane. There is no hint of detonation and it has stock-like street manners. You can back off timing and boost when the compression is optimal for the fuel and still make more power then the same car without optimal compression/quench.

    Cheryl :)
  8. hugger

    hugger Well-Known Member

    Mike at Wildcat agrees with you on not thinning the caps, that's what concerned me about that whole operation too, but as you said it's hard enough finding someone that can install the girdle let alone modify it then install it. Once cut as directed there is what lime 3/8 of material left maybe little more?
  9. dr

    dr Well-Known Member

    I planned on doing a girdle or anything else to help the motor live. I want to build it "right and strong". I agree Jim if I'm going to spend that kind of coin DO NOT GO cheap on the little stuff. If it MIGHT help, I'm going to do it.
    Keep the advice coming, you guys are great.
  10. sailbrd

    sailbrd Well-Known Member

    MLS gaskets please. I blew out others on 5 psi. Agree that boost numbers mean little. Think more about percentage of max rpm. A D-1 can support 925 hp. So if you spin it at 90% of max you should be around 800 hp. I ran for 4 years with stock reworked rods and crank with no problem (has girdled Poston pan though.) Tuned very conservative. Get an MSD 6530 box. Timing control is critical. Great in stock cam for D-1 is a TA 413. New solid cam is better but not huge better.

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