Scotty's Racing Technologies 494 build

Discussion in 'Race 400/430/455' started by stg1dom, Feb 18, 2015.

  1. gmcgruther

    gmcgruther Well-Known Member

    Buickstage1, I'm curious if you ever contacted Royal Purple to see if they have any light weight racing synthetic oil? I always ran Royal purple in light oils for the oval track small block chevy's and never had a single problem with oil pressure variance's. I see buick is becoming a trick in most peoples eyes but common sense and a little engineering goes a long way. I'm trying to see where I can help but not over engineer it at the same time.
  2. gmcgruther

    gmcgruther Well-Known Member

    Your correct 8ad, but to start at one hundred psi is not the correct way to go. I follow AM&P and don't see any of his engines run 100 psi ;) So what is everyone doing wrong to have to run 100 psi? To me it sounds like a volume problem not so much psi! I'm gonna contact pac racing springs tomorrow and see if they make oil pressure springs and if they do, I will write down their number so anyone can have a spring made for their particular engine. Custom made springs through them is not exspensive it's just time.
  3. Jim Weise

    Jim Weise EFI/DIS 482


    Yes, the 555 Crower crank is in fact bullnosed and knife-edged, that motor has no significant windage issues.

    You are talking about the 1% motors here.. Most Buick engines follow the 11-12 psi per 1000 rpm rule.

    It has been proven time and again, by a number of different builders, that high oil pressure is required to keep a high rpm/high HP Buick alive.

    In my own experience, George Sweesy's 870 HP 525 was my trip thru the school of hard knocks. Only after we went to the external oil pump and overhead oiling, which plugged the main galleys and fed the mains directly, would that motor live.. and then it did live, for a number of years, and bearing problems magically disappeared. At 870 HP and 765 ft lbs of torque, we litterally pounded the main caps off that motor.. but it never hurt a bearing again, after I cranked up the oil pressure.

    It was sold around 2009 to Greg Looker out east, and he ran it for several years.. Qualified number 1 in the V8 class several times at Englishtown for the Buick meet... I know the car is getting a Tomahawk now, but I never heard if that motor expired, or if it was just being upgraded.


    The most common theory for the need for high oil pressure was 2 fold... the narrow main bearings and large diameter crank bled a lot of oil, and were more prone to breakdown of the hydrodynamic wedge, resulting in bearing/journal contact, causing bearing failure, if the oil pressure was too low.. and the big 3.25" main 4.400 to 4.500 stroker cranks, would generate G force in the oil at rpm, and push the oil back away from the rod bearings.. number 3 was a particular problem.

    These motors had oil passages enlarged, and ran external, belt driven oil pumps.. volume was not an issue. Windage was not an issue, the dry sump motors were in the same boat as the wet sumps.

    Virtually all these problems were solved by going to high oil pressure. If you could get thru the traps at over 100psi, you were golden.

  4. bobc455

    bobc455 Well-Known Member

    I disagree wholeheartedly with this assertion. I might not be an expert engine builder, but I have a strong mechanical engineering education and have worked around many types of machinery and lubrication systems throughout my career.

    For a PRESSURE gauge, you want the smallest possible volume of oil between the pickup point and the gauge. The larger the volume of oil, the slower the gauge will react. This is more evident in gasses than liquids (i.e. this is even more important with a MAP sensor than an oil pressure gauge because of the fluid compressibility), but the same principle still applies.

    You want the shortest and smallest diameter line that is practical.

    If you need to maximize flow, then you want larger diameter channels and whatnot. But for a pressure gauge, flow is not important and you want the smallest volume of fluid that is possible.

    Back into my quiet corner now.

    BQUICK Well-Known Member

    Gary, as Jim mentioned the large truck-sized main bearing diameter 3.25 is the reason for the high oil pressure. Won't find that in any Chevy engines that I know of......
  6. buicksstage1

    buicksstage1 Well-Known Member

    I called the tech line because I am quite sure that David Reher of Reher-Morrison Racing Engines is no dummy so I called and talked to the head tech guy at AutoMeter and the simple fact is that if you look at the oil hole on the back of any of the fuel, boost and oil pressure gauges you can see a restricter orifice in that hole. That restrictor is in all those gauges to kill the sensitivity/response of the gauge/needle. He says they had a lot of complaints about the needle movement so a restriction in the line is what resolved it. So I guess regardless of line size a curtain amount of this fluctuating etc in the oil pressure is dampened out on these gauges.

    Something else that is a common issue that slows a gauge response down is not bleeding the air out of the oil line.
  7. TheSilverBuick

    TheSilverBuick In the Middle of No Where

    You both are talking about two different things. Bob is right about response time, but the larger size will show/allow a greater max to min variation, and if the gauge is high quality it will quickly register that max-min variation because of the amount of fluid transfer with each pulse of the pump rotor. Smaller line, smaller volume, smaller transfer of the pulse, aka, it can only push the needle so far. Both being liquid fluids, the response time difference between large and small diameters is negligible to our visual observation abilities, but a computer would likely pick up the speed difference.

    On a secondary funny note, electric gauges have electrical dampeners/filters in them to filter out that same needle twitch. A friend of mine ran an oil pressure sensor right to the megasquirt and dang thing datalogged every pulse of the external belt driven oil pump, lol. He had to de-rate the sampling interval and smooth the oil pressure data because it plotted as a perpetual wave, lol.


    Here is an example of vacuum data on my Firebird's engine. The vacuum line tee's, one goes to the gauge (that has an internal restrictor) and one goes to the megasquirt. Same size line in both directions. The vacuum gauge is rock steady, as is the filtered/dampened megasquirt gauge, but looking at the unfiltered data and high sampling rate, you can easily see the individual pulses through the 3/16th vacuum line. This is at an 826rpm +/- 10rpm idle. Basically oil pressure does the same thing with each pump rotor lobe, and like the intake pulses, the oil pump moves at half crank speed, so its not overly fast and the max to min ticking would easily be seen at lower rpm's with a large diameter line and no restrictor.
  8. buicksstage1

    buicksstage1 Well-Known Member

    He also said that they put a special jell on the gears in side the gauge that helps slow things down.
  9. Jim Weise

    Jim Weise EFI/DIS 482

    All of which is why pressure transducers, not gauges, are used in dyno testing.

    The transducer will pick up things a gauge never will.

  10. TheSilverBuick

    TheSilverBuick In the Middle of No Where

    Like Bob, I'm going back to my quiet corner now. I find these discussions very interesting and thanks all for the sharing of information and public discussion!

    (I plotted that data up to see if any of my six cylinders were not pulling as much air/vacuum as the others. All the low points are reasonably consistent, so it appears each cylinder pulls from the intake plenum equally.)
  11. Robsbuick

    Robsbuick Precision Billet Inc.

    My 2 cents............pressure is one thing and volume is another.
    Not by choice, but I made 2 passes with 20 lbs of pressure @ 7000 rpm with the Tomahawk with no damage.
  12. buicksstage1

    buicksstage1 Well-Known Member

    You are 100% correct Rob, its the old finger over the end of a garden hose deal. Prioity main oiling doesn't need as much pressure.
  13. slimfromnz

    slimfromnz Kiwi Abroad

    Thanks for that Chris, couldnt have done it without all the assistance from guys like yourself.

    Thats impressive Rob.
  14. gmcgruther

    gmcgruther Well-Known Member

    Hmmm, remember what I said about a fineline between pressure and volume? The restrictions in the iron blocks is our problem and it can be fixed period. Now the TA block, Rob thank you for proving a point. If there is enough volume, you don't need a ton of pressure ...
  15. gmcgruther

    gmcgruther Well-Known Member

    BQuick, your wrong on the chevy's, look up 555 on up big block chevy's, they all have the monster size 3.25" crank ;) and yes, some are dry sump and some wet sump. No problem with volume or pressure there ;)
  16. gmcgruther

    gmcgruther Well-Known Member

    JW, Here is a simple test for you and everyone else, take a simple holley red fuel pump and install a 1/2" line and make atleast 6 nintie degree radius's not to tight though and put a regulator at the beginning and a pressure gauge at the very end of lets say ten foot line. Set the pressure at 6 psi, no do a holley blue and do the same thinng to it and get the same pressure . I promise you one thing, that the volume rate is not the same period. This is my point in this thread. Restrictions make a major problem in volume not pressure . Fix the volume rate on the bad side and you won't need the high pressure. Again, Why doesn't AM&P have such high pressure compared to you Jim? Sinerely Gary M.

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