Stock rotating assembly power capability

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  1. #1

    Default Stock rotating assembly power capability

    I have a stock rotating assembly from an 05 GT. What is the rough HP limit at the crank for the crankshaft, rods, pistons?

    Thanks!

    Rob

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  3. #2

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    500hp is pushing it. 550hp is cliff hang area. 600hp is grenade time.

    All those numbers being out there... It totally depends on how and where you drive it, how light or heavy the car is, how good the tune is, etc... . On the street, spinning generic brand stock-sized tires, is WAY different than being on the strip with slicks dropping the clutch from 4500 RPM

    Sent from my SM-G965U using Tapatalk

  4. #3

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    Crap, For some reason I thought I heard that crank was good to 700. Thanks for the info!

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  6. #4

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    Crank.... Maybe... Rods no.

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  7. #5

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    If the crank is a forged crank (8 bolt flywheel and center counterweights) it is good for 3000+ turbocharged HP. With a PD blower like you are running Rob, the ceiling is going to be around 800-ish. The problem is not the rods or mains it is the snout. Big screw blowers like you have kill the snout. If you shift at 7500 and the blower is pullied to hit 18,000 rpm at 7500 then a gear change in a T-56 will instantly change the blower rpm from 18,000 to 12,000 rpm. If you have an automatic it is much easier on the crank.

    The inertial tug this puts on the crank snout to slow down the rotor pack is off the scale. The more aggressive the clutch the more damaging the gear change. Short of going to a billet crank with a 1.400" diameter snout the best compromise is to stud the crank. There are two articles in the TToC about the studding process along with part numbers for the ARP hardware. The stud is not a 100% fix it is more like an 80% fix. That said there are only one or two (possibly) studded cranks that have ever broken a snout and even with the broken snout the stud saved the rest of the engine.

    The OEM rods like msvela488 has already indicated are throw aways. A set of Manley H-Beams will cost you ~$600, a set of the Manley I-Beams will cost you about $2,300. A set of the Weiseco Boostline blower rods will cost you about $1250. All three are available through Summit or Jegs.

    Here is a pic of a Manley H-beam

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    Here is a pic of a Manley I-Beam

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    Here is a pic of a Wiseco Boostline

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    Rod strength is not really a HP related issue unless the beam is particularly weak. It is actually an rpm related issue because our engines make their power at elevated rpm. I would feel very safe with the H-beams up through 8000 rpm. Above 8000 you need either the Manley I-Beam or the Wiseco Boostline rods both are excellent rods. I have a preference for the Wiseco design because... If you want a cheap insurance policy get the Boostlines. I've seen a Modmotor that pushed the crank and mains right out of the block. The Boostline rods were undamaged and used in the next build.

    This was the block

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    And these were the rods and pistons

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    As you can see the rods and pistons lived to fight another day.


    Ed
    Last edited by eschaider; 05-18-2019 at 03:50 AM. Reason: Fixed broken pic links

  8. #6

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    Ed,

    Thank you for taking time to make this post! However thankfully I am not using any of these parts in the 4v motor I am building. The rotating assembly I am referencing is what came out of the 05 Aluminator block I purchased for my build. I was seeing if I could use it for another project a friend and I were working on. We are swapping a 2v into a 94 fullsize Bronco and topping it off with a tork tech kit. Was hoping maybe I could get a little bit extra out of these parts I had laying around. Thanks to your guidance previously, I have already set my eyes on a set of Weisco Boostline rods, a billet Bryant crank, and a set of your custom pistons a-la Gibtech. Thanks Ed!

  9. #7

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    The two premier crank shops for any of the professional cars (Nascar, T/F, F/C Pro-Mod etc) are Bryant and Winberg. When I was sourcing my billet Bryant was too busy with regular customers to do a custom billet. Winberg was also but asked if I could wait until the professional season ended. Because I wanted a 1.400" snout, a ⅝ stud and other custom stuff I was willing to wait for the season to end. The crank that Randy Winberg built for me is stunning and I couldn't be happier.

    This is what it looks like

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    You can get a quick sense of the relative snout size when you look at the #1 main journal. The snout is much bigger and longer than OEM. You can read all about the crank snout improvement development in the Crank Tech I and Crank Tech II articles in the TToC. BTW I did not use a factory snout mounted oil pump. I went to an external pump that was just the pressure stage off a dry sump pump and used a through the side of pan Milodon swinging pickup. The oiling system mods were primarily for reliability and pump performance at elevated rpm.

    I asked Randy to lighten the crank pins with if I remember correctly with a 1" counterbore, rifle drilling of the crank mains is now standard. I upgraded to 7/16" flywheel bolts (up from 10mm) and finished the rod journals off to use the SBC 2.0000 inch journals in the Saleen rods. The snout uses a custom length and diameter with a ⅝" stud. The lightening of the rod journals is not a performance enhancement necessarily but, it does lower your reciprocating weights which means less mallory to balance the crank. The only change I would make today would be to replace the custom stud with an off the shelf LS7 Damper bolt (ARP Part# 234-2504) it is dimensionally similar, ARP 2000 steel and an off the shelf item — the last part, off the shelf item, is big deal.

    Randy Winberg was easy to work with and willing to do anything I was capable of drawing up. Bryant is also very good but more focussed on current pro class racers so depending on time of year and what you are asking for you may or may not be able to get it.

    Parting thought on the crank, wait until you have your rods and pistons before you order the crank. Randy includes balancing in the base price of the crank which will save you $500 because of the mallory.


    Ed
    Last edited by eschaider; 05-18-2019 at 01:06 PM. Reason: Spelling & Grammar

  10. #8

    Default

    Thanks ed, great looking chunk of steel you have there. Your crank tech threads were as exhaustive in information as usual, great reads. What was your reasoning for going with the 2" journals down by 0.086"?

  11. #9

    Default

    The SBC journal has a much wider selection of bearings available for it because it was the go to racing journal size for years before everyone settled in on the Honda journal size, Rob. Additionally I wanted to use the slightly shorter Saleen rod for increased piston speed as the piston leaves TDC.


    Ed

  12. #10

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    Ed, I definitely need to start reading the book on engine math I ordered. Any benefit to the increase in piston speed?

  13. #11

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    Quote Originally Posted by rainyp71 View Post
    Ed, I definitely need to start reading the book on engine math I ordered. Any benefit to the increase in piston speed?
    The faster (with reason) that the piston moves away from TDC the greater the pressure drop the intake port sees. Like any office, increasing the pressure drop across the office will increase the mass flow through the office. The shorter connecting rod produces a more rapid movement away from TDC. When you do this you place a greater tensile load on the rod and rod bolts.

    The Saleen Rod at 5.850" vs the stock rod at 5.933" does not appreciably increase the pressure drop at the intake valve. The primary benefit of the rod is the availability of the increased range of bearings offered in the SBC journal size and the ability to get the wrist pin further away from the oil land.

    If you dig into ProStock engine metrics you will discover a block deck height approximating a Modmotor or less (depending on the year you look at) and a surprisingly short connecting rod. Additionally the engines typically use a bore stroke ration between 1.3 and 1.35. The engine designer is attempting to get an engine with low internal parasitic losses, very high volumetric efficiency, and an operating rpm range that will allow gear changes between 10,500 and 11,000 rpm. NHRA, I believe, has placed a limit on engine speed by limiting it in the Holley ECU but, 10,000+ rpm is still a pretty good number.

    All this design sophistication is how they extract 3HP per cubic inch from a naturally aspirated race engine. Can it help us — sure. Is there a better (cheaper) way to get the power — yup! Just go down a step on the blower pulley or up a step on the crank pulley. The shorter Saleen Rods will get the pin further from your oil land and probably give you just a small enough power increase you won't be able to see it on a dyno chart.

    If you want the best book I have in my library on engines, cars and performance stuff in general, go to this link on Amazon => Physics for Gearheads. It is just about as good as it gets — and don't be put off by the Physics part of the title. The book is a must read for all performance enthusiasts who want to modify there ride.


    Ed

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