4 banger weight reduction

Discussion in 'Rotating Assemblies' started by NitroInjected, Jul 23, 2018.

  1. NitroInjected

    NitroInjected Well-Known Member

    Without sounding as my usual self ( out of place.) I have a question about the webs on my crank.

    I am losing 200 grams... or more if I can help it off my rods as I switched from an old forged design to a new H beam design in 4340 vacuum drawn steel. ( Which seems to be the low end of the spectrum these days.)

    Now all that weight under of course can come off the webs right or wrong?

    Now here's where I blow off track. This is going to be a quick car by modern terms if I can help it.
    I am not too concerned with feeling viberation as it wasnt smooth at all in stock form.
    Can I mill the webs right to just about nothing if I wanted?
    I am thinking about having the guy doing the balance profile the crank to balance it rather than add slugs ans while he was at It I was thinking about having him cut 4-8lbs (4kg) off from the crank and another 10 off the flywheel as from what I can see performance ones for my car are just stock ones that have been windowed and slotted.

    Now an expreienced builder of my engine type said the bearings wear strange at power ratings over 400 crank. my goal is 550 or -20 Hp nothing over as I dont have an engine dyno but I do have 1/4 times to test against. I am going to read up on bearing clearences as I never really thought much about it at such a low H.P. but this engine only makes 175 at the wheels NA and 276 boosted from the factory and thats what they raced with until 94 when they upped it to 300.

    Maybe still out in the woods but if someone can give me an answer about that crank this week I would be happy as I can relay info to the shop that is going to do my crank after I do the static balance.... Oh heck why not throw this in there. Is there a guide on lightening H beam rods with no pad. Theres another website with a near identical rod that weighs 80 grams less at 550 grams.
  2. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    This a Chevy Ecotech ?
    Ford 2.3 Lima?
    Nissan ?
    Honda B18 or B20 ?

    An aftermarket Forged or Billet might be Better.
    Crower will build almost any engine crankshaft.
  3. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    Ford Cosworth ?
  4. NitroInjected

    NitroInjected Well-Known Member

    I was out in the shop when it dawned on me that I forgot to say.
    Lotus 910 2.2l turbo version.
    Slant 4 torqueless gutless engine slammed in at the time a great chassis.
  5. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum


    Cosworth is Legendary Power
  6. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    don,t remove more weight from the crank, more than what may be required too get it correctly balanced,
    the steel in the throws and counter weights, on the crank, helps control flex, and resulting stress.
    and I darn sure would not reduce the weight of a 20 lb flywheel,
    as the mass helps a great deal with getting smooth acceleration, and reducing heat build-up issues
    reducing weight in the rotating assembly pistons and rods is a plus, provided strength is not reduced.
    reducing the crank or flywheel mass may help the engine reve quicker in neutral, and marginally if at all, reduce upper rpm stress but at a significant cost in long term durability,
    and reducing the flywheel mass does very little or nothing once the drive train is locked to the flywheel. like it will be under acceleration.
    a larger more efficient turbo and inter-cooler , could significantly improve boost, but it also requires a higher octane fuel and more effective cooling and better oil flow.
    before dumping a ton of cash into building what you might consider to be a kick butt, engine you may want to mentally step back and look over all your options,
    and certainly one of those is swapping to a car with fewer limitation,
    before you invest the time and cash into what may be a rather expensive conversion of the existing drive train,
    for what might be minimal gains compared to what the same cash outlay spent else-ware might provide,
    I'm certainly not saying you can,t build the car, just look over your options carefully before you dive head first off the dock, financially.
    be darn sure you won,t regret spending a ton of cash on a project you won,t be happy owning just to vindicate your idea and impress some clown on a web site youll never meet in person.( that could be totally a troll)

    if your builder says the bearings wear oddly with engines producing over 400 hp,
    its almost always related to block and crank rigidity issues, excessive flexing, or lack of lubrication under high boost




    Last edited: Jul 23, 2018
  7. NitroInjected

    NitroInjected Well-Known Member

    This isnt the cosworth.... sadly
    Also I will just cut what I need to balance the crank then but... I do want to profile it a little to get windage down as this engine does run in the upper RPM... 4000-7200 is where its good and I am trying to run another 500 RPM safely.
    I will be going against your advice on the flywheel with much respect to you and your knowledge. I dont give two farts about it being smooth I got a foot and computer to control that . I want to go fast. 20lbs in this car is a bit much and I would very much like to be able to stab the throttle for down shifts... Well there are many reasons and I respect what you are saying and I thought about the risks vs rewards on the flywheel a lot. The crank however is a territory that I will listen to you on and not anyone else to be honest as I have seen a lot of bad information out there on the web. I should also mention this is a forged crank but based on modern methods of the 80s. I am betting it is far out of balance by today's standards.

    Heck while I have your attention I have to ask... lets say these throws are rediculiously heavy.. I have not and can not weight the throws at my home yet but I bet its over by a lot. Is there a way to calculate a safe weight to cut off from the crank. Like a good balance between longevity and performance?

    My cooler has to be about double what it is now to cool the charge efficently and not get hot. The old system was scorching about double will get me ambient even with the larger turbine.
    If this was a cosworth I would not even need to ask how to develop it and to be honest what I spent on developing the gasket and getting rods alone would have paid for 500+ brake power.

    Allright back to the shop! One more piston to clean and Ill get that photo up before I weigh them again.
    ( All within half a gram. These pistons cost the p/o 800$ MAHLE did good. I sanded a bit inside the skirt to take off two 3 tenths of a gram on the heavy one.)

    Grumpy. It's my dream car. This isnt the engine I wanted but its not like I can afford the taxes on the v8 which has its flaws as well. But make no mistake this is a spite build and it is beyond my means. The only reason it came apart now was because the first builder used a screwdriver to install the rear main burning up my new clutch and he used some crappy sealant on the block halves and.... did not adjust lash at all... New valves and didnt do a valve job. ....clever.... My goals before were just 100 H.P. less but I honestly would probably have put just as much care into it as I just cant put it back together knowing it has a weak gasket nasty ports an heavy rods. So It probably would have happened anyways.

    I am going to read your articles but in the meantime I thought I should say I think oil is a major player in the engines issues and a ball bearing turbo along with a proper clean up of the oil system should get me in the right direction. If I do dyno it and find out I am making more than 550 I will do what lotus should have done to the block.
    Last edited: Jul 23, 2018
  8. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    if you can find one locally its would be better, but certainly you can find an experience crank assembly balancing machine shop ,
    that can profile the crank throws, mag test the crank for flaws,polish the journals, and reduce the crank mass , matching its balance to the new lighter weight piston & rods,
    without compromising the cranks structural strength
  9. NitroInjected

    NitroInjected Well-Known Member

  10. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

  11. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    Mitsubishi EVO is the toughest 4 cyl. I have seen.
    Built a 1st gen EVO engine last year in the Race Shop I worked in.
    44 psi Boost on the street.
    The Flying EVO.
    Infamous race car.
    Carrillo Rods.
    Venolia pistons.
    844 Hp at the wheels.AWD.
    Rode Shotgun at 2am
    Street Racing in Chicago burbs.
    Scary Fast.
  12. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    Diesel engine Turbo. 88mm.
  13. NitroInjected

    NitroInjected Well-Known Member

    I think to get any more than 600s I would need to do something major to the block . .... Or a swap....
  14. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    Yes. A custom Engine to Transaxle Adapter needed for your Lotus to swap.

    I have to do some reading on your Lotus later today after work.
    They are nice cars.
    Turbo boost adds tremendous torque gains. Hp follows.

    Grumpy is correct block strength and limits known are important.
    Making a crankshaft lighter for Turbo boost likely not a good idea.

    Engine vibration messes with the valvetrain in operation terrible.
    Broken parts usually.
  15. NitroInjected

    NitroInjected Well-Known Member

    There is a lot of misinformation online about esprits and that particular motor. Read and take internet tomfoolery lightly.

    Like I said a swap is out of the question... Illegal... If I blow it up theres a chance for approval as the engine is rare and old.

    I might add a fluid damper to the mix. But honestly a good balance properly set valve train and injection that actually fires the proper amount of fuel only on the intake stroke should cut this engines roughness down. Then I will add some back with a lighter flywheel and if I can get some formula for how big the throws should be for optimal balance I will. I have not finished reading Grumpys articles. I fell asleep not from reading... it was 3:30 am.
    Hmm could I just stamp the block number onto a honda engine and paint lotus on the cam cover??? Lol. I just keep saying honda because they are cheap to build.
  16. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    I like the Honda engines.
    Made nice.
    Last a long time.
    Fairly easy to work on.

    Those Mitsubishi EVO 2nd gen Cars are terrible to work on.
  17. NitroInjected

    NitroInjected Well-Known Member

    Not a fan of the chassis weight for the stock engine output. So I was going to make a balancer today but only got the small end made... I got too big of a piece for the big end... DOH!

    BACK ON TOPIC: I stray easily.... I was thinking about just maybe getting a fluid damper and having it machined to fit my crank. A bad idea? I know any Honda... I say honda because its so common... always has a damper attatched if its making anything north of 500 brake.
    Last edited: Jul 24, 2018
  18. NitroInjected

    NitroInjected Well-Known Member

    Finally I got my balancing jig close enough to repeat within a gram.... still not ideal and I had some crazy numbers I just ignored but in the end small ends were 200 for two of them and 201 and 202 for the others. after I measured the whole set ten times each I went back 5 more times to make sure. I will be subtracting from the total weight rather than using the jig because of how I have it set up and having only one scale. I will be remaking this in steel if I ever need one again and to be honest I didnt have a lot of luck with the chain as I did balance the spindle but it kept cocking over.... My fault and I know I need photos but my phone is right full. Ill cut them tomorrow after work and its looking like I will have to have the machine shop verify. I hope they dont have to cut anything. Also looking at other pins of a similar overall size mine are huge. I am almost comfident I can loose 70 grams but... It may end up costing 200$ ... no one carries a 1 inch pin.

    Maybe I better clarify on my jig. The issue seemed to be the scale side being clamped down right and not a long enough chain along with the wrong dimensions on the l bracket that holds the big end.
  19. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    That is a big Wrist pin diameter.
    Big Block Chevy is .990".
    Pontiac V8 With Pontiac spec Rods are .980.
    Chrysler 426 Hemi had 1.031" wrist pins.
  20. NitroInjected

    NitroInjected Well-Known Member

    Maybe that actually could help me... I wonder if 426 pins are long enough or longer. It would be nothing to get some lighter stronger pins that were made for a hemi and have them turned down. Probably cost me 50$ but money well spent. If you know of anything else close let me know. The length is 61.88mm

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