Oil Pressure Equalization line

Discussion in 'Race 400/430/455' started by Jim Weise, Feb 24, 2015.

  1. Jim Weise

    Jim Weise EFI/DIS 482

    I did some testing here last fall, with a 600HP 470, equipped with my equalization line.

    The purpose of the line is to balance the oil pressure front and rear of the engine. It also provides a handy place to hook a good -4 oil pressure gauge feed line.

    Here is the line..


    Comes from the oil pressure sender hole on the RF of the block.. this is my STG 1 head routing..

    With STG 2 heads


    We disconnected the lines at the T and did some testing.. hooked a pressure transducer to each side, and made a pull.

    (sorry for the old tech here on the sheet.. my digital copy is not with me right now)

    Oil_P on the sheet is rear pressure, LineP is front pressure. Pickup points are the oil sender hole, and the RH rear galley. -6 line size.


    Interestingly enough, when we hooked the two lines together again, no other changes, the pressure actually went to the lower number.


    By feeding the Passenger side main galley from both front and rear, we have now eliminated restriction to oil flow that the engine wants.. this is why the oil pressure drops to the rear reading. At this point, we just increase the system pressure back to where we want it. In this particular engine, the rear pressure was where we wanted to run the pressure, so no adjustment was needed.

    In any event, I have had a few folks ask me about it, so I sat down tonight to show it in greater detail.

    The only tricky thing is you have to tap the rear of the galley considerably deeper, to fit the steel 90* fitting in the bellhousing. l highly recommend the use of steel fittings and braided stainless lines and fittings, anytime you put anything inside the bellhousing.

    It would be a drag to have to take a motor out to fix a leaky line.

  2. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    How long did you hold it on the pull? I would think after a few moments on a sustained rev the numbers would even out. A difference of 10% seems like a lot.

    Maybe you could do a volume test? Spin it with a drill with the line off and the other capped and see which empties the pan first? perhaps the oil is more likely to turn up into the galley than down and out the sender hole? Must be less of a turn towards the galley..
  3. dan zepnick

    dan zepnick Well-Known Member

    kinda off topic here but how low(years) do guys use the braided line? does it break down? 5 years?longer? lets here how long you've had the same line on your engines ??
  4. TheSilverBuick

    TheSilverBuick In the Middle of No Where

    Also off topic, can you share the EGT data? :grin:
  5. Jim Weise

    Jim Weise EFI/DIS 482

    Sure, what head, intake, cam, carb combo are you interested in?

  6. Jim Weise

    Jim Weise EFI/DIS 482

    The total running time, from engine start, pull to WOT, and then the test, is typically 20-25 seconds.

    But the difference as you see, is consistent thru out the pull, more or less.

    Look at any one of the dyno videos on my website, and you can calculate how long it runs.

    Volume to each side would be difficult to measure, but I would suspect that only dynamic testing would be useable information, free flow tests out of the engine would only be limited by pump speed and orifice size.

  7. Jim Weise

    Jim Weise EFI/DIS 482


    I think heat cycles would be the measurement component you would use. The hoses would last indefinitely if it sits in the shop all the time.

    I had a set of braided stainless trans lines on my 89 Suburban for 13 years.. daily driven for about 5 of those.

    They were hard for sure, but we had no issues.

    On a race car, I have seen where the fuel lines tend to stiffen up first, but I don't know of any recommend service interval. There are engines out there with this by-pass line, that were built 12-13 years ago. I have had no feedback of line/fitting failures, but then again, these are not daily driven cars.

  8. TheSilverBuick

    TheSilverBuick In the Middle of No Where

    Ideally square bore SPX intake with TA stage1 aluminum heads to see if there a meaningful cylinder to cylinder difference (the SPX has some nice runner length though so I'm not expecting much). Smaller details to be more pertinent to my combo would be mid-10's compression and ~.550" lift +/- ~.02", knowing if the cam was a 4-7 swap or not. Mine is EFI, but a square bore Holley of appropriate CFM/size is good.

    As a PM or another thread, I'd be interested in your thoughts about cylinder to cylinder distribution with different intakes/combinations given your experience on the dyno and apparently EGT data that I hadn't noticed before!
  9. Jim Weise

    Jim Weise EFI/DIS 482

    I will start a new thread for you Randal.. and get another copy of the EGT's for this motor later this week.

    It is the 4-7 swap/ Stage 1 SE/SPX/Holley deal your looking for.

    SPX intakes are not widely used, including the cool runner versions, I think I have only done about 5... Several of those were before I drilled the STG 1 and 2 headers for EGT's, which happened in about 2009.

  10. buicksstage1

    buicksstage1 Well-Known Member

    That is pretty much what I have seen in all my testing, on a 648hp stg2 and it showed a difference of 5-6 psi. You guys don't run a oil temp gauge Jim?
  11. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    I deleted my post. Still interesting that there is only an 8 pound difference from front to rear. If you are holding the rev for 25 seconds- much longer than an ET (hopefully), I still wonder if its worth the 100 bucks in fittings and lines. Oddly enough last night I just placed the order to Summit for everything needed for the job.
    Daves 67 GS likes this.
  12. buicksstage1

    buicksstage1 Well-Known Member

    Not in my opinion. But some people will have a bigger loss then others depending on oil mods, clearances etc so it should be checker and I always run the oil pressure off the back for any thing better then a warmed over street build.
  13. Jim Weise

    Jim Weise EFI/DIS 482

    Yes, Chris, oil temp is monitored via a temp sender strapped to the oil filter.

    It's just not on that sheet.

    Good investment in my book Joe, I always put them on motors above 550 HP.

    You simply can't go wrong stabilizing the oil pressure across the mains.

    Lack of oil pressure at number 4 main, is the number one cause of #7 rod bearing failure, which is so common on stock engines.

    Traditionally, we have prevented this by increasing the oil pressure, taking into account the front to rear drop.. so crank it up to 70-80, to insure you have 60-70 in the back of the motor.

    With the line, your now working what we will call "system pressure", so you can set it where you want it, without having to push it harder in the front, to keep it alive in the back. Reducing stress on the oil pump, is always a good idea.

    A required mod?... I will be the first to say no, but just like windage screens, never a bad idea. I like it on higher HP motors, because few people are going to invest the extra $$ to build 600 HP, and then drive it like Grandma..

  14. 64 Hardtop

    64 Hardtop Founders Club Member

    Interesting, thanks for the data. When I assembled the engine in my 64 I used this equalization line concept. I hard lined mine with 3/8 steel tube. I wasn't sure of braided line lasting and I didn't want to chance it.
  15. Jim Weise

    Jim Weise EFI/DIS 482

    Interesting you mentioned that Dwayne..

    I have been considering a steel line kit for this.. to reduce costs.

    Downside is the flexible braided gives you options in routing, which is important when your building just the motor, and not a car.

    But it is one of the products I have on my development sheet..

  16. buicksstage1

    buicksstage1 Well-Known Member

    They left the factory with a shield to stop the oil from getting aerated etc so if they were concerned enough about it on a stock engine to install one then I think it is up to us to use windage screens/sheilds, crank scrapers etc. Not only does it help keep the P/U tube covered, prevents oil from getting aerated and helps keep the oil out of the crank it = HP.

    As far as the rear oil line goes that is something that I have been testing for a few years now and the last thing I will do is jeopardize someones investment, if something is needed to go past the full distance it gets is.

    It boils down to what ever it takes to keep the builder confident that it ain't coming back is money well spent. :TU:
  17. buicksstage1

    buicksstage1 Well-Known Member

    I also questing if its a small id line how does that effect or does it effect the response time, volume and pressure etc by the time the increase gets to the back of the engine?? Will it leg?
  18. 8ad-f85

    8ad-f85 Well-Known Member

    I can say that on the other makes, Cadillac, AMC, Sm. Mopar...nobody is using a smaller line.
  19. Jim Weise

    Jim Weise EFI/DIS 482

    Rooting around looking for some EGT stuff or Randal, I came across this example.. Jim's motor (Machinefarmer)..

    Didn't start out this way, but ended up being a virtual duplicate to Larry's motor, save for some head porting.. and it does not have the equalization line.


    We did upgrade the balancer to an SFI unit, and the oil pan to an TA fabricated pan, before it went in the car.

    Here is the data, the by-pass line was not in the original buildup, and I did not add it, as I knew it was optional, and did not want to be seen as "running the price up"... this motor is the only one, of 70-odd builds in 15 years, that changed hands during the process. I guess I have been lucky that way.

    Here is the sheet, which I have the digital copy of.. and the appropriate datapoints.

    From Left to right... Corrected Torque, Corrected Power, BSFC, Fuel, Air, oil temp, oil pressure, coolant temp


    This would be representative how how I would tune a motor like this.. notice the oil pressure is up in the 80's, without the line in it. It will drop into the 70's with 160* oil, but a drag race motor would only see that if he were going rounds at the end of the race. SO I tune the oil pressure for that possibility.

    This sheet is also representative of all the ones you see from me.. we do not get the oil to 180* and cool the water to 120.. to make more power.. that is not the point of testing, as far as I am concern. I like to test a steel rod motor, with the oil between 120-140*as measured at the fiter skin. That is typically within 10* of the oil temp in the pan.

  20. gymracer01

    gymracer01 Well-Known Member

    Jim :

    Just noticed this post today, this is some what like a problem I have wanted to ask you about. I got a 470 from a noted Buick engine builder and installed in my racecar. It had the line as shown. It also had the added aluminum spacer on the oil pump with an external pickup from the SRE pan. Unfortunately after 2 1/4 mile passes and 1 1/8 mile pass and a couple of 60' runs, it spun a couple of rod bearings and after tearing it down all bearings appeared to have been having an oiling problem. The pan had all the baffling that is required and was run with plenty of oil. First failure of this kind I have had with a BBB in over 20 years of racing them. Current engine in car has been ran for ten seasons, and I assembled it with stock oiling. The engine that lost the bearings also had a girdle.

    Jim N.

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