Landracing Forum
Tech Information => Technical Discussion => Topic started by: Leadfoot on June 17, 2013, 03:47:18 PM
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Just wondering if anyone has had any experience with runnung a vacumn pump on a Big Block chevy on the salt ? I know they are common in drag racing circles but will they work for 5 miles with out hurting the luburcation of internal parts. Plan on running 12-14 lbs vacumn. Any thoughts ? thanks.
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I run a dry sump---but I have piston squirters & and EDM drilled rods
the squirters help in several ways .
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Ok thanks, I should of mentioned that I do have a wet sump right now.
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Just for clarification, are you sure you meant 12-14 lbs vacuum? As in 12-14 psi? That would be around absolute zero, which I don't think is possible.
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Your right...I mean Inches of Mercury. 12" to 14".
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A friend mine runs one on 600" blown BBC with dry sump and has been over 250. I've run one for over 20 years on an inline engine.....What's your concern?
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We sometimes use an electric one from a cheby, it works good and not too hard to find a used one
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We sometimes use an electric one from a cheby, it works good and not too hard to find a used one
Unless we are running one of the motors set up to create vacuum using the exhaust. Of course we are running a 60.0 inch motor unless we are running our 84.0 inch big block... :roll: only spinning the motor to 13000 last year, no oiling issues.... wet sump as well.
It does seem to lower the oil pressure a little, but it helps move it through the motor.
YEMV :cheers:
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Theoretically, on a closed wet sump oiling system, the static pressure within the crankcase will have no effect on the oil pressure to the bearings and valves. Your gauge pressure will read lower, because it will be comparing the actual pressure at the pump within the closed system (say 40 psi which is against an internal static pressure of -7 psi) with atmospheric pressure (which your gauge reads as 0) so the gauge might read 33 psi. The same will be true of a dry sump system, as long as it is a closed system. On my old BSA, the dry sump tank is vented to atmosphere, so I'm a little concerned about the sump pumps ability to pump against the internal vacuum. But I'm only hoping for about a vacuum of 7-10 inches of water pressure (about 1/4 to 1/3 of a psi) so I'm not too concerned.
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Im concerned mostly about the removing of the oil mist which helps lubrucate the wrist pins.
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Lead...never lost a piston we could blame on that. My pins are a "palm" fit on the rods and I run a scraper on the pan. The catch can should have a petcock to check after every run. We find about a 1/2 teacup of clean water on the first pass of the day. Condensation. We both have vacuum reliefs set at 9"
25 years ago when I started running one I had it spinning to fast and did suck out some oil. Slowed it down another 20% and have had no problems since. Most are built for "squirt" racing and not full throttle for 5 miles. I would never run again without one. Most use a 3 or 4 vane Moroso amd I use an Aero Space Industries. They say a 4 vane is for a big block but our 600+ inch BBC uses a 3 vane because we took it off a SBC and never had a bearing or pin problem with it.
NASCAR runs a lot of vacuum with their drysump pumps. They have valve spring squirters for cooling so they may have piston/pin squirters too...............Good Luck
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We run one on the 608 AA/GL. 582 BBC. 14-15 in vac. Works well. No problems with oiling.
Our engine guy says that over 18 In is when you need to worry about wrist pins and crank bearings. The drag race guys that run hi vac use a coating to retain lube, he says.
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Ok thanks everyone for the good answers . Gary
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If you run a "dry sump" system then the engine case pressure does not have any affect on the engine pressure pump operation as it's inlet is from the bottom of the drysump reservoir. IF you have a "wet sump" system, i.e. one oil pump in the pan of the engine that pumps inlet pressure is the pressure in the case plus the height of the oil above the pump inlet. If you reduce the case pressure you will reduce the pump inlet pressure, if the pump inlet conditions are anywhere close to marginal you will cause the pump to cavitate, i.e. the vacuum at the inlet of the pump will cause the intrapped air and desolved air in the oil to become seperated from the oil in the forms of air bubbles and these will then be pumped into the engine lubrication system. Air has no lubrication properties so guess what happens next. Therefore if you have a dry sump engine then a case vacuum pump is a good idea and worth horsepower, if you have a wet sump engine then I suggest you be very careful.
Rex
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Use the 4 vane pump if your going to purchase one. The 3 vane can shear off the screws due to it's design. 12-14" will get you the largest percent of power available without oiling issues to the pin. Also an external oil pump is a great addition. It allows you to install an isolator between the oil in the pan and the crank. This helps a bunch in reducing the pounding (piston action) of the oil in the pan which aerates it.
The vacuum pump will also allow lighter tension rings, especially the oil ring which is the biggest drag.
Blessings..........Ron C
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Leadfoot:
We were curious about a vacuum pump too. We just did a dyno test with my old school "D" motor 302 SBC. 3" stroke, 4" bore, AFR heads, tunnel ram w/ two 650's and a big cam, VP 110. We tuned the motor to 472.3 HP at 8,000 without our a vacuum pump. Put the belt on and made 492.1 at 8,000 RPM for an honest 20 HP. Aerospace Components 4 Vane pump 16.9 Ins vacuum which is high. We did not pull any oil into the pump and oil pressure stayed at a steady 90 PSI so it did not appear the pump was keeping the oil away from the wet sump pick up.
Horsepower had not fallen off up to 8,000. After 19 dyno pulls we decided to take the engine off the dyno, drop the pan and check everything before we moved up to the 8,400 pulls. It was still making about 3 HP per 100 RPM at 8,000 so in theory it could make a little over 500 at 8,400. We also had #7,#8 running a little rich so there may be a tiny bit more power in the carb tuning.
BR
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BR;
8400RPM...what kind of valve rockers are you using?
Regards, Neil Tucson, AZ
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BR,
Great to have some "real" numbers as to what a vacuum pump is worth in real horse power. Your wet sump engine must have a very efficient and deep pan an oil recovery system. Thanks for the report, another real number we all can use.
Rex
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Thanks BR thats some good numbers should be even better on a larger cubic inch engine. Gary
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Where did you plumb the suction side ??? Valve cover ?
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I've used both pan and valve cover and reccommend valve cover. Make sure you have some type of deflector under the fitting to deflect the oil. Mine is attached to the rocker arm assembly.
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Yes, welded two -10 bungs to each valve cover. One -10 an to the suction side of the pump and the other side we attached to the Dyno vacuum port. We did not see it pulling any oil. Not sure if we just got lucky.
Valve train is a Clay Smith cam, Comp Cams roller lifters, Scorpion rockers 1:5 exhaust, 1:6 intake, Comp Cams stud brace. Comp Cams lifter retainer.
BR
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No oil in the vaccum pump is not OK. At the salt in 5 miles you will fry that pump. Put a couple of squrits of oil in the pump before every run.
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I might have mis-spoke.
When I said no oil in the vacuum pump I meant it was not picking up large amounts of oil from the valve cover and discharging it out the discharge side of the pump. It was picking up some mist and had an oily film but was not sucking oil out of the valve cover. We had heard that vacuum over 12 to 14 on a wet sump could hold too much oil up top and starve the pump. We never saw any indication that was happening. In fact, the motor always has made a lot of oil pressure. It has a Melling billet pump and made about 90 PSI at Bonneville. We used 20W50 and it made at times 100 psi. Seems we can drop the viscosity down some.
I will use your suggestion and put a few squirts of oil in the pump before I make a run.
Tomorrow at work, I'll scan both dyno sheets and post them.
That's why I like this forum. I always take away some good advice or ideas.
BR
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The fortunate 'idea" is that you have found some time to work on the car.
I think you have been missing that.
FREUD
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Thanks, BR. I was assuming that you used some sort of shaft rockers for that high RPM.
Regards, Neil Tucson, AZ
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Doc:
I actually got the front suspension installed last night. It is good to have a roller again. Waiting in a new release bearing and the engine and trans can go in. Not a record capable engine but it will let me go to a few mile events and shake down the new modifications.
BR
The fortunate 'idea" is that you have found some time to work on the car.
I think you have been missing that.
FREUD
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BR,
Great to have some "real" numbers as to what a vacuum pump is worth in real horse power. Your wet sump engine must have a very efficient and deep pan an oil recovery system. Thanks for the report, another real number we all can use.
Rex
Here are some more real numbers for you Rex. I wish I got the same results as BR. I just finished 3 days on the dyno - testing and tuning my 295 cu in Flathead Ford. After establishing a baseline 230hp @5500rpm on gas, we hooked up a brand new Moroso vacume pump. Max hp with vacume pump was 229 for a loss of 1hp. Scrapped the idea of the vacume pump. Went on to test with Methanol. Made 250 hp with Methanol and 260 hp with 10% Nitro. I think I will start in XF/FCC at Speedweek this year and maybe switch back to gas later in the week. See you on the salt.
Gord Driedger
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What is a good baseline to run the pump...10 -12 inch ?
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We were told by the engine guy 12 to 14. On the first pull we guessed at the setting and the engine vacuum was 17.1 and made 20 HP. We adjusted it down and at 14 we gained about 12 HP. Adjusted it back up to 16 and gained 19 HP.
The engine had some interesting responses. It shows rich on the EGT's and O2s but when we leaned it out some the HP dropped dramatically. The carbs are not the best so some of the rich may be the carbs. It also responded to a lot of timing somewhere around 36 degrees of total timing made the most power. In addition, we ran 20W50 and the difference between a starting oil temp of 177 and 195 was 15 HP.
BR
What is a good baseline to run the pump...10 -12 inch ?