oil pressure

3/4 through 1/8 mile run our oil pressure goes from 90psi
to 40 every run
dan olson pan 11qt
tried more oil 14qt
kb stage 10 block and brad fuel heads
no push rod problems
do i install restrictor plugs in deck of block and
what size hole should it have
or is their another fix
also we have twisted 2 mag shafts off cold oil
pressure is about 160 till warm then idle is 60
3000 rpm and up is 90 psi
any experience would be helpfull
thanks
duane

 

That sounds like a lot of variation...what kind of oil pump do you have? Is it a dry or wet sump?

14qts of oil still isn't "lots" of oil, in our dry sump deal we run near 20 in the tank. We have a pleuger dry sump pump, 150psi cold and goes to about 110 when hot idling, usually 95-100psi after the burnout when staging dependant on how hot it is outside. The hottest weather we ran in was the Seattle national event, 105F outside, left the line with 85psi. Just would be curious to see why it's so low when idling. What does your car idle at??

 

faria oil pump wet sump
looks like system 1 also
system 1 coarse screen oil filter
idling at 1700
during the run its at 90psi untill about 500 ft
or about 3.5 second into run

 

I would be real careful about restricting oil up to the heads or you will eventually end up with pushrod problems which can be catastrophic. I know some of the top fuel guys run as much as 20 quarts of oil in a wet sump motor. I know that will probably be higher than the pan rail in the motor but it would help you to know if it is simply running out of oil. Another consideration would be clearances both in the bearings and the oil pump itself. Also what viscosity oil are you using. I don't know anyboy running less than 50 wt and on the hotter days lots of guys are running the 70wt nitro. How are you monitoring your oil pressure? I am assuming a racepak or something like that? Good luck with it. Dave Germain

 

we run 60 wt valvoline vr1 but we are switching to
70w lucas or valvoline next year
we monitor oil pressure with a computech computer
this has done this from day one we want to run 1/4 mile
but we cant with this problem
1/2 inch drain holes are clear through block/headgasket/
and heads
their is threaded holes in the head surfaces for restrictors
if i run restrictor what size hole .080/.100/.125 should i use
17-20QTS is making sense
THANKS
NATHAN/DAVID/MIKE
any help to do this one time is apreciated
DUANE

 

It sounds like you are bound and determined to restrict the oil to the top of the motor. Restricting the oil to the heads is really restricting it to the pushrods. If you burn an intake adjuster to where it won't open the valve the next event is the motor goes lean because 7 cylinders are getting 8 cylinders worth of air. Unfortunately they are still only getting the amount of fuel that they were getting previous to the pushrod failure. That leans the motor and it eats a rod bearing and kicks the rods out the side of the block. So by restricting the oil to the top end you might boost the oil pressure to the expense of the rods, crankshaft, and block. Once that happens get in touch with me. I have a KB stage 15 block for sale. It's been windowed lots of times, that is how I figured this out. Dave Germain

 

which heads are you running fuel or fat heads
what crank are you using
what main bearings and clearances
and has the block ever been windowed???

we used to run restrictors in our TFX bocks
until we went to external oiling
I went and dug up records
we ran a .032 on right side and .045 on left side
remember this was for a TFX block
been way to many years to try to remember back when we ran KB's
if we ran restrictors then or not, but i really think we did
call up Keith Black's shop and ask

 

Restrictors...........(NO) I had the same similar problem.solved by preheating the oil and adding more oil16qts.The coolest idea I have heard is the one from mike, take off the pan and start filling it,ect. that will tell you how much oil is always in the motor not in the pan.and like dave said once you start having push rod probles look out...that can be devasting. Good luck.Dave Lowe

 

when i called keith black they said .080 restrictor
but do they really know my combination
[stage 10 and bae fuel heads faria wet sump-
dan olson pan bryant crank]
looks like i will assemble and try more oil 16-20 qts
then if i still have the problem ill remove heads and
install the restrictors
im thinking about gores fuel management and overboost richener
any body had problems going this route on the fuel system
THANKS EVERY ONE

DUANE

 

I feel compelled to comment on this issue as we have run alcohol funny car, nitro funny car [Nitrofish], and now Top fuel dragster for nearly 30 years.First thing we must understand is that NO oil returns to the pickup until the engine stops! With crank windage, thick oil, small drain backs, how much 50 wt oil can you pour down a 1/2 in. hole in 4.5 - 9 seconds. Restricting the flow to the head with an .080 to .100 jet is quite aceptable because after a 90 second burnout and staging procedure the motor will have at least 8 -10 quarts in the top of the motor. On a dyno pull with the right side valvecover off, oil will shoot out of the drainback ??? holes 15 feet in the air! The motor requires 1.7 qts to operate! Having run wet and dry sump systems for quite a while put at least 20 qts. in the motor or tank, adjust the pump pressure to have at 100 psi runing hot and lastly forget about the oil pan, in this case size does not matter !!!

 

Another idea and question. What is the condition of the Cam bearings? An internal leaker really shows up at idle. The pressure returns when the engine rpm comes up. It can mask this problem. It is very hard to change bearings on some raceblocks and this can become overlooked. You almost always see a dry sump on a TAFC with a screw. My experience is the engine oil capacity will make it on a roots but real problems show up when a screw is installed. Same pan and oil capacity. Won't make it. 18 quarts plus in a wetsump pan can start oil foaming and leaks.
We have always run restrictors with external oiling to the head. Boats and cars. Helps stop oil leaking by the headgasket into the chambers beside the oil gallery that feeds the head. Careful with the silicon around the holes. .060 works great. Brad billet blocks come with this size restrictor.