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Author Topic:   sbc 406 oil pressure funny
teenwolfnorcator
Dirt Roller

Total posts: 21
posted May 04, 2005 09:13 AM  
just fired a rebuilt 406 all new rotating assembly, new hi volume oil pump,oil restrictors.
oil pressure at climbs to 65-70# after warm up when motor is turning 5000 rpm the pressure will drop to 40-45#,when you back off the power to 2500-3000 pressure will rise back to 55-60#. What is going on?
Thanks.

novajohnb
Dirt Roller

Total posts: 6
posted May 04, 2005 09:40 AM  
Do you have a high volume pump? Oil restricted to top end? Sounds like you could be pumping too much oil to top end at high RPM's- and lowering oil level in pan. Do you have enough quarts of oil in the engine?

teenwolfnorcator
Dirt Roller

Total posts: 21
posted May 04, 2005 11:08 AM  
Yes, hi volume oil pump, 8 qt. oil pan. The restrictors are supposed to slow the oil from going to the upper part of the engine. The engine under race condition won't normally be turned much over 6000 rpm. With engine turning 6000 and only 40# psi is that good for the motor.Oil screen set to correct depth for the oil pan, bolts loctited. What about something in the oil filter failing?
Thanks

rrrrick
Dirt Maniac

Total posts: 192
posted May 04, 2005 11:10 AM  
if you have a cheap oil filter on that, try changing it with a good racing filter from K&N or a the like


dirtbuster
Dirt Forum Champ
Total posts: 2007
posted May 04, 2005 11:18 AM  
try the oil filter first. Put a wix or napa racing filter on there and see what happens.

next I would make sure you have the thing vented well. Were all the drainback holes open when you put it together? The lifter valley holes should not be plugged, standpipes are ok though. Make sure the breathers on the valvecover are clean and free flowing. You need to vent the crankcase otherwise pressure builds up and oil can t flow back down.

With a typical 20w50 oil, and decent clearances and a high volume pump you should get at least 60psi easily when you rev it up (hot) and it should never go down as you rev it.

teenwolfnorcator
Dirt Roller

Total posts: 21
posted May 04, 2005 08:30 PM  
I will change the oil filter tonight and let you guys know the results. Thanks

Jesterondirt
Dirt Full Roller

Total posts: 56
posted May 05, 2005 09:08 AM  
I'll bet it is the filter, always have that problem on new engines due to the lubriplate

teenwolfnorcator
Dirt Roller

Total posts: 21
posted May 05, 2005 09:39 PM  
Sorry for the late reply, changed oil filter,I think that it helped some, added 8qts of 20w50. After engine is at operating temp will carry 40psi. rev engine to 4500 will rise to 58psi then drop to 45psi then rise back to 58psi. When running at 5800 will carry 58-60 psi. Going to run tommorrow to see what happens. The motor is painted yellow that might be what is wrong with it.
I am puzzled.
Thanks

teenwolfnorcator
Dirt Roller

Total posts: 21
posted May 05, 2005 09:41 PM  
Also put different gauge on no change.

speedy2
Dirt Full Roller

Total posts: 54
posted May 06, 2005 05:01 AM  
ive got a 406 that does that, drops pressure goin down straights and shoots back up entering corner. 8 qt pans with wix racing filer 51069R. Had other problems with motor not related to oil pressure so took P.O.S. out so didnt get into that much detail on why it did that. Anyone have any thoughts?

Clyde Torkel
Dirt Full Roller

Total posts: 33
posted May 06, 2005 06:38 AM  
I have seen engines with way too much bearing clearance have low pressure on the throttle and then have the pressure rise when off the throttle.

BrianW
Dirt Freak

Total posts: 385
posted May 07, 2005 06:39 AM  
Are you sure your oil pickup is close enough to the bottom of the pan, or the opposite - too close to the bottom of the pan?

Did you check it before assembling the pan on the engine? If so how much pickup clearance are you running?

teenwolfnorcator
Dirt Roller

Total posts: 21
posted May 08, 2005 07:30 PM  
I made sure the oil screen was not to high, it was sety close to the bottom don't remember how close to the bottom.
Did run it and it didn't blow. It didn't seem to have much blow out of the breathers.
I am using the smaller nappa filter because of header clearence.
Thanks.

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