Jump to content

Black Magic

  • Content Count

  • Joined

  • Last visited

  • Days Won


Black Magic last won the day on February 17

Black Magic had the most liked content!

Community Reputation


Recent Profile Visitors

2,258 profile views
  1. Black Magic

    Reground Camshafts

    My dad did it in the 40s with flat head fords required to be "spec" through selection of valve springs (to be soft) Some things don't change It was not kind on parts then either
  2. Black Magic

    Reground Camshafts

    Extra "like" or "agree" on this In general you are going to see a lift increase when you make sizable duration changes. This is due to the valve dynamics, as a "square" cam lobe would accelerate the lifter\bucket off the cam too quickly causing not only more lift at that point, but lots of load in the valvetrain parts when it all crashed together again. You can sort of reduce this with high spring loads, until that breaks something else. To get the stress manageable the compromise is to add lift at the max point so the curvature change is less extreme. The quick 80%/20%, you would catch 80% of the messed with cams using 20% effort by looking at max lift alone.
  3. Black Magic

    Reground Camshafts

    Good question. I would assume that is open (clarify, meaning timing), since most of you guys change it inadvertently when you deck heads, replacing timing belt parts, etc. I would guess i am in the minority who actually degree my cams in when i do a rebuild. I doubt stock cam duration and lift is gonna benefit much from changing overlap or valve open events. Not like big duration and lift will.... Solid point huggy, gotta pick your battles.
  4. Black Magic

    Reground Camshafts

    My suggestion +.030 lift at valve, - infinity +10 deg duration, - infinity In head measurements will always read low. Failing these would be a pretty clear non oe..... You would need a stock engine, or well supported engine to know the stock .050 lift specs. Advertised numbers are junk.
  5. Black Magic

    Reground Camshafts

    The other options are Regrind cam on smaller base circle and deck the cam caps the amount of the base circle reduction (needed to fit your cam profile on the oem material). You then re bore the cam journals in the head to size, dropping the cam down in the head for ohc engines. Several cam companies offer welded regrinds, where they remove the surface hardness, weld on the cam, grind it and then re harden it. Webcams for example. Depending on how rare your engine is, the cam companies may or may not have cam blanks from the oem or aftermarket available. This creates the welded and small base circle cam industries.
  6. Black Magic

    Reground Camshafts

    I have run non oe cams in one of my neon motors. To really notice the power, you are gonna notice the lift and duration. Like .050 to .100 or more lift change, and 20+ degrees of duration. You will also notice the idle quality, and vacuum....
  7. Black Magic

    Reground Camshafts

    Anyone submitted a "what fixed vpi is fixed ?" petition yet? If not might be a good time. So far: Aero is not Cams are the rest??
  8. Black Magic

    Statistically Speaking, Fuel Capacity

    Or because the entire ready to run caged car you bought ($2500) was cheaper than some of you have paid to have your car caged up..... The path in to champcar can be very different depending on the team and their resources.
  9. Thanks for the perspective chip and guys....confirmed I am somewhat normal, but not fully Alot of the cars I have driven don't have the pedal spacing to heel toe (little toe big toe really) well, and it seems like I do my downshifting a little later than most. I am doing it a little after initial turn in, with a throttle blip, just before I want to apply some drive power again. Usually I am in FWD cars and having to "diamond" the corners more than a RWD, I think this habit developed around trying to make the car turn (clutch in, diff if limited slip unlocked) when otherwise tight. Like the sc300, I don't row down each gear because I don't have the clutch out mid decell. Driving more RWD cars it seems like I need to try downshifting earlier, and see if it helps my timing and entry speed. The few rwd cars I have done (at least the small rwd cars) all seemed like I could have carried a little more entry speed and rounded the corner more, which is I think is part of this unlearning FWD habits. I think in RWD cars I might be too "busy" near the apex with my method, and getting the shifting done sooner might let me spend more effort wheeling the car. Also great to get more perspective on how different people drive, because as a team event I need to understand how most guys drive, so I can test those scenarios when working on car setup.
  10. How many of you downshift and use engine braking (downshift early part of braking) vs late in the braking event? I tend to do it really late, closer to the point where i want to apply maintenance throttle\get to the gas than when i start braking. Sort of a fwd habit (use engine braking differently to create balance change) and a desire to keep the potential for high\over revs down on decell\downshift, but curious how a typical i am (probably very). Might also be a car owner thing (if you gotta do the motor swap work for an over rev......).
  11. Black Magic

    Anyone have Aero questions?

    Good luck, sounds like a fun group to work with. I have wanted to get some of my race engineering geeks (engineer) friends together to do something but none of us have really jumped at it. I am doing more tech videos for the series, and when we get around to aero (we have a way to go) i may bring you in to give some pointers. Aero is my least knowledgeable area.
  12. Black Magic

    Crankcase ventilation (the good kind)

    The large volume I was quoting in the first thread was doing some rough napkin math on what would have to come out if you had 10% power loss (not 10% reading on a leakdown tester). A good motor at our 150 to 200 hp would most likely be about 2 to 4 cfm actual blow by. Look up vacuum pumps as a power adder. Depending on your ring design pressure in the crankcase will be a detriment to ring sealing, and you will lose some power. There are some other actions going on here, but you will pick up power if the crankcase pressure was high and you vented it better. The major detriment I have seen from not having enough crankcase venting (a pcv valve at say 1/4" outlet diameter as the only vent was not it) is horrific oil leaks. Almost all of your seals are not meant to handle positive pressure. The crank, cam and valve cover gaskets in the nightmare I lived though pushed out and started leaking even worse than the engine smoked. That engine had a bend ring on assembly and actually burned the piston ringland off in a spot (where the ring was leaking, you need piston seal to trap a insulating layer of air on the piston top or it gets plasma cut). With more venting I would have been able to finish the race (without going full exxon valdez), but the motor would still have burned alot of oil and needed a rebuild. If you had a dyno you could try adding more vents and see if the power picks up, or you could log the crankcase pressure (what pro's do) and see how high it is. Beyond that, try and make sure you have a 3/8" vent somewhere and add a second if convenient. Make sure to pick an area that is baffled (want air not oil out), or you will just make an oil film version of old faithful. Most of us plug the extra vents, and the "makeup air vent" which is meant to be an inlet, because in a turn or under braking the valve cover dumps oil out that particular port. Run each of your vents to a separate bottle (with some air vents in the top) do a few laps and see where the oil is coming out (if any) and only use vents that get air out, not oil.
  13. Black Magic

    Statistically Speaking, Fuel Capacity

    Using (curb weight * .9 )\gallons.... Some could lose 5 gallons and still beat 170 lbs\gal 😞
  14. Black Magic

    Teach me about leak down tests

    If you are seeing 10% power loss in a region with ve around 100 it is gonna be close. Assuming the same thermal efficiency, the loss of power is from either cold charge (compression) or burnt charge (power) escaping, or both. But totally agree a 10% leak down tester reading at 100 psi is not this, because the pressure is much different and the duration is short. It could easily be a factor of 10 smaller in actual %blowby of delivered volume to the cylinder thus and power (1% would be 2.6 cfm). Only point being, it takes alot of blowby to kill your power enough to notice it in our racing, assuming you have enough pcv venting to not have a rise in crankcase pressure. Just trying to give perspective on "if having a slightly low leakdown test is a big problem, medium or small for an na engine". Great write up and info mender. Wish you were east coast to build a car with.
  15. Black Magic

    Teach me about leak down tests

    Agreed, much better tool. In a pinch I have used a compression tester and just hooked it to shop air with the cylinder held at TDC to listen for where the air is going. In my case, it came out the adjacent cylinder (warped head). When looking for where the leakage could be going, if you are really getting 10% leakage past the rings dynamically, to create a 10% loss of power, it has to go out the crankcase system. Most of us have blocked some of the stock PCV system, and the average team I would guess has a single 3/8 hose as the only PCV vent. At 150 cubic inches (.087 cubic foot), 6000 rpm, firing all 150 cubic inches every other rev, you are looking at 26 cfm through a 3/8 hole. Lesson learned from blowing out the cam seals, most of us have undersized crankcase vents for bad levels of blowby.