worried about this 78 vette oil pressure am i paranoid?



worried about this 78 vette oil pressure am i paranoid?

Postby sozo13 » September 2nd, 2010, 2:03 am

I got a 78 vette original L48 350 only mod is an aluminum intake and a slightly larger cam..or thats to the best of the owners knowledge ..it has 75k original miles, again to the best of my knowledge .. ive had it a few months it runs great but for what im used to seeing the oil pressure seemed a little low to me ..

right at start cold it idles at 40psi ... cold it still doesnt climb above 40 at shifts ..(4spd factory rear end 3.08 i think? not very low ) so im guessing 3000 -3500rpms when i run the gear out just a little long ....tach needs a new board its on order. ive never really tached it out but it seems safe to say it looks like 40 -43 or so is the hard limit on my pressure seems to jump around fine with a little rev once warmed up and idling till it hits the magic 40-43 then stops solid.

warmed up its holding around 17-20 idle and about 35-40 at shift points ( NOT a synthetic oil)
now i know the factory oil gauge isnt very acurate so I HAVE confirmed these with a mechanical gauge ..attached right beside the distributer ...factory electric is at the filter.

the engine runs at 160- 180 degrees will get
up to 190 ish at sustained highway speeds 65-80 never gets over 180 idling in traffic. running 10w40 oil atm moment and its a recent oil change.

im about to change the oil pan gasket so an oil pump change isnt a big deal ..but my questions are

1. do these numbers look normal and or safe ? its been years since i even had a V8 I used to play with hot rods alot in high school ( 20 years ago )and seems like i always had better pressure on my cars. 60-70 or so at running speeds and 25+ at idle

2. what type pump should i look into putting on it or is it fine as is? ..and if its not ,what numbers should i be looking for on pressure this car is NOT hot rodded and i want the longest possible life out of whats left on this motor?would putting in a new stock pump be of any benifit ?are these pumps prone to any gear wear within the first 100k miles?

3. is there some sort of pressure bypass that could be failing to allow my pressure above 40 if this is a low number for this engine?

4. and if i go with a high volume/pressure pump will i have clearance in the stock pan without modifying baffles ect?


Thank you for your time any info would be great.!
Shane
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Re: worried about this 78 vette oil pressure am i paranoid?

Postby grumpyvette » September 2nd, 2010, 8:30 am

viewtopic.php?f=54&t=2376&p=7633#p7633

viewtopic.php?f=54&t=1800&p=4597#p4597

viewtopic.php?f=54&t=525

read thru these threads, above carefully


your symptom, tends to indicate a weak bye-pass spring, or a defective installation on the pump or pick-up,because normally oil volume increases with the rpms up to the point the bye-pass circuit starts releasing oil back to the feed side of the pump, regardless of engine clearances, and while the pressure may not rise rapidly the pressure is directly related to the pumps rpm,up to the point that the bye-pass circuit opens, but there IS a chance that the pick-up is mounted too close to the oil pan floor, if its less than 3/8" it can restrict oil flow into the oil pump, this can and frequently does cause pressure to drop off rapidly once the engine reaches the oil flow rate where the clearance becomes a restriction point in the engine oil flow due to its rpm.

replacing the pump and verifying the pick-up to pan floor clearance is usually the cure
Image


http://www.melling.com/Aftermarket/High ... Pumps.aspx

there are high pressure bye-pass circuit springs available

http://www.summitracing.com/parts/SUM-122171/

http://www.summitracing.com/parts/SUM-122170/
Image
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: worried about this 78 vette oil pressure am i paranoid?

Postby sozo13 » September 2nd, 2010, 5:24 pm

Great thanks for the info ..i think im going to change the spring out i found a high pressure spring for the stock pump from MR.gasket just 2 questions.

1. is it as simple as it looks ..can the spring be swapped without removing the pump? and im assuming theres no adjustment there just replace and tighten the nut/spring cap back down?

2.im going to check my pickup clearance i see i need a minimum of 3/8 of an inch ..is there a MAXIMUM i need to be weary of?
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Re: worried about this 78 vette oil pressure am i paranoid?

Postby grumpyvette » September 2nd, 2010, 6:01 pm

sozo13 wrote:Great thanks for the info ..i think im going to change the spring out i found a high pressure spring for the stock pump from MR.gasket just 2 questions.

1. is it as simple as it looks ..can the spring be swapped without removing the pump? and im assuming theres no adjustment there just replace and tighten the nut/spring cap back down?

in most cases yes its ALMOST that simple, just remember to oil the piston and spring assembly, before they get re-installed and the LARGE END of the spring goes OUT facing the nut/plug NOT THE PISTON

2.Im going to check my pickup clearance i see i need a minimum of 3/8 of an inch ..is there a MAXIMUM i need to be weary of?

yes the minimum distance is 3/8" between the oil pump pick-up and the oil pan floor and the max is generally considered to be about 1/2"between the oil pump pick-up and the oil pan floor, you measure with a lump of clay on the pick-up lower surface being compressed with a temporary install of the oil pan
then measure the compressed clay, after removing the oil pan (see picture)

Image
http://www.amazon.com/Pro-Art-056001410 ... B002NZAOSS

Image

IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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