I built a 415 stroker with Eagle crank, rods, Ross pistons in the lower end with a Mildon 7qt oil pan and pickup, high volume oil pump. Running Dart Pro1 heads with a Comp Cams solid mechanical cam and lifters and roller tip rockers. My problem is I have 25 to 35psi at idle hot, 50 to 60 psi crusing speed and when I get into the motor oil pressure climbs to 70psi then suddenly drops to 25psi or less at around 4000 to 4500 rpm and a soon as I let off the throttle oil pressure jumps back to 70psi. I have removed the motor replaced oil pump and pickup checked all bearing clearences old bearings look like new, replaced all bearings with new installed a widage tray bigger oil pan new pickup and pump and still have the same results. I do not uderstand why the oil pressure drops. I am running 8qts of oil with the filter and do not believe that all of that oil could go to the heads and puddle. I put 300 miles on the motor before tearing it apart and could not find anything wrong with it. Anyone have any ideas?
400 Small Block oil problems
bac6772
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i had exactly the same problem last year,, cruised ok, idled ok, but when i stepped on the gas a bit the oil pressure dropped and came back up when i got of the gas,, if i accelerated very slowly the oil pressure rose as normal.. after taking the sump of loads of times and changing the pump twice ,, oil filter twice,, checked all the bearings.. it turned out to be the oil level in the pan.. if the oil gets up in the crank under acceleration it turns it to froth and the pressure drops.. try lowering the oil level by a quart and see if the problem eases.. it worked for me and it cost nothing and takes very little time.. george
That's an interesting one George. I'll have to file that back in the memory for future reference. It does make sense - especially if you are running an oil that doesn't have awesome anti-foam capabilities. If you were foaming the oil then that 3/4" pickup height would be an even bigger problem.
Wix makes specialty racing filters that are supposed to flow 28gpm compared to standard 9-11gpm filters. These are for "track use only" since they don't filter quite as well, but you could always try one to really rule out the filter - they are only about $8~$9. They make many different ones with or without different options.
When the engine comes out again - if it's a fresh tight engine how about throwing a stock volume pump on it? I know what a pain it is to keep pulling an engine - hate to just "throw out" ideas that cause you a lot of work, but it's a thought.
Wix makes specialty racing filters that are supposed to flow 28gpm compared to standard 9-11gpm filters. These are for "track use only" since they don't filter quite as well, but you could always try one to really rule out the filter - they are only about $8~$9. They make many different ones with or without different options.
When the engine comes out again - if it's a fresh tight engine how about throwing a stock volume pump on it? I know what a pain it is to keep pulling an engine - hate to just "throw out" ideas that cause you a lot of work, but it's a thought.
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Valve spring life will suffer with any kind of restriction.bac6772 said:
re:400 small block oil problems
I had the exact same problems with my LT1 383 using a Milodon 7 qt pan. Running the rpms up slowly no problem..doing it quickly... around 4K oil pressure dropped. I had the melling HV pump etc. Tried different weight oil and filters no change. I ended up putting 6 qts. in my 7 qt. pan... problem solved. Oil vortex I guess? I also suggest that the oil pickup be 3/8 above the pan including whatever gasket you are using. Good luck with your problem I know how much it sucks to have this kind of problems after putting a lot of money into your engine!
I had the exact same problems with my LT1 383 using a Milodon 7 qt pan. Running the rpms up slowly no problem..doing it quickly... around 4K oil pressure dropped. I had the melling HV pump etc. Tried different weight oil and filters no change. I ended up putting 6 qts. in my 7 qt. pan... problem solved. Oil vortex I guess? I also suggest that the oil pickup be 3/8 above the pan including whatever gasket you are using. Good luck with your problem I know how much it sucks to have this kind of problems after putting a lot of money into your engine!
zephyrc said:
This is funny I had this EXACT same problem too. hard acceleration and oil pressure went to ZERO!! scared the livin crap out of me. i babied it the way home...I thought for sure my oil pump pick up came out. But it turned out low oil level!! - motor mysteriously eats oil and does not smoke/leak. Definitely check you pickup height (and oil
), maybe its screwy with the 7 quart pan.
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As easy as it is to do ,the first thing I would do is eliminate the oil bypass . Jeg's and places sell them or you can do it yourself with the right hardware. Your high velocity pump may be more than your "old" bypass can handle.
RE: 400 small block oil problems
I also had all kinds of advice from fellow rodders... like my high volume pump was emptying the pan etc. but think about it ...a stroker crank has a longer throw so it will travel into any oil pan further than the stock crank. So it will hit the oil sooner... if you reduce the level of oil in your pan by half the increased amount of your stroke you are maintaining the same clearance as the stock crank. Remember how you had to notch the block? With after market rods that use larger bolts they also travel further into your pan and at higher RPM's they will whip up the oil and it stays around the crank leaving the bottom of the pan empty. I did not check it out but I wonder how much one quart raises the oil level in SBC pan...my guess is about 1/4 to no more than 3/8 of an inch... just look at your dip stick! Again it's just my opinion that this IS your problem.
I also had all kinds of advice from fellow rodders... like my high volume pump was emptying the pan etc. but think about it ...a stroker crank has a longer throw so it will travel into any oil pan further than the stock crank. So it will hit the oil sooner... if you reduce the level of oil in your pan by half the increased amount of your stroke you are maintaining the same clearance as the stock crank. Remember how you had to notch the block? With after market rods that use larger bolts they also travel further into your pan and at higher RPM's they will whip up the oil and it stays around the crank leaving the bottom of the pan empty. I did not check it out but I wonder how much one quart raises the oil level in SBC pan...my guess is about 1/4 to no more than 3/8 of an inch... just look at your dip stick! Again it's just my opinion that this IS your problem.
My engine builder swapped the stock SB pump fpr a BB pump w/ matching canton 7qt pan/pu AND when you think about it kinda makes sense as this is a big motor nonetheless. Honestly I dont think this is your problem but it sure don't hurt have the BB pump.
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F-BIRD'88 brings up a good thought on the oil filter. If you using a FRAM (even if it is NOT the root problem) use something else.
tom
tom
oil press drop ....
Are you seeing any oil loss from the engine ? A friend of mine had a similar problem at rpm and it turned out he was losing oil from a bolt hole from the front of the motor down by the fuel pump that went all the way into the crankcase .... we fixed the problem by installing the proper size short bolt with a bit of sealant. Are you running a windage tray ? Give a 1/1.5 qt. lower oil level a try. I think high volume oil pumps are over rated .... never ran one and never had a problem even spinning over 7000 rpm on a 355.
Are you seeing any oil loss from the engine ? A friend of mine had a similar problem at rpm and it turned out he was losing oil from a bolt hole from the front of the motor down by the fuel pump that went all the way into the crankcase .... we fixed the problem by installing the proper size short bolt with a bit of sealant. Are you running a windage tray ? Give a 1/1.5 qt. lower oil level a try. I think high volume oil pumps are over rated .... never ran one and never had a problem even spinning over 7000 rpm on a 355.
Well I have solved the problem with the help from everyones advice. I lowered the oil in my 7qt pan to 5.5 qts and a half qt in filter total 6 qts and I no longer loose oil pressure under acceleration and my idle oil pressure went up 10 psi. Looks like Buds34Ford was right on the money with this one. I would have never guessed that this would have been the problem. I now have 70+psi under load and 45psi at idle, before I had 15 to 20 psi idle and under load would only go to 60psi and drop to 20psi.
Thanks for everyone's advise, and I hope this helps someone else with this problem when buliding a stroked 400sbc
Thanks for everyone's advise, and I hope this helps someone else with this problem when buliding a stroked 400sbc
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You say you got the filter that has a non bypass setup on it, put you a real cheap filter on it, it will permit more flow,and will probably increase pressure, I always run a cheap filter on my drag race motors for that purpose.bac6772 said:
I'd rather have more oil and less pressure, than more pressure and less oil, Small block chevy can live on 15-20 lbs.
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No.eliot said:would the oil pressur drop,at that r.p.m. if the plug between the two oil pass.under the rear main bearing cap was out,left out/
tom
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Once the filter is full the oil will go the path of least resistance and will bypass the filter but should not affect the oil pressure.eliot said:would the oil pressur drop,at that r.p.m. if the plug between the two oil pass.under the rear main bearing cap was out,left out/
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