Jvette73

heres the original topic I started but its read only now>> http://forums.corvetteforum.com/zerothread?id=653563

Anyway I was talking to a trusted source who asked me how the vette was runnin and I said great except for this oil pressur drop off above 5k. He askes me if I was runnin a Fram filter with the black grip stuff on the bottom. i said yeah I think so. Anyway he pulled a box off the shelf and showed me one and compared it to a Purolator filter. He pointed out how the Purolator didnt have a rubber diaphram just under the holes and showed me how much bigger the holes were on the Purolator. He said that the smaller holes and the diaphram on the Fram filter were causing the exact symptoms in other engines he had delt with. He told me to get the Purolator # L20049 and give it a try. The momment I get a chance I will do so and test drive. Ill let you all know if it solves the problem. Car still runs as good as ever otherwise. Rock on.....

71coupe

munday

i read in the building hp book.by david vizard that having as little as 1/2 qt to much of oil can cause frothing at high rpm and oil pressure drop off....

turns out my installer from my engine the POS HE IS!!!!! couldn't get my dipsticktube in so he ziptied it to a sparkie cable. so this whole time I was thinking i was even i was 1/2 qt to much.

Jvette73

The filter swap didnt cure the symptom. Some day Ill get to pullin the pan and checkin other stuff out. Oh well, it still runs great and maintains great pressure under normal to moderate driving conditions. Its only when you pound it hard and run it to the redline above 5k rpm that the presure drops off. Drops off from 65 to around 35 before the 1-2 gear change. It rises again after the change to 2nd but will begin to drop off again to below 35 when aproaching redline in 2nd. The second you let off the gas it shoots right back to 65.

vert2go89

Are you using a high volume oil pump? Could it be you are not getting oil back to pan fast enough therefore losing pressure?

comp

does it have a windage tray in it ??

Jvette73

Yes im running a high volume pump and no it does not have a windage tray. One of these days when I get some time and money I plan to pull the pan and add a windage tray and maybe a 6 qt pan and a different pump. Ide like to do these things one at a time to see exaxtly what cures it but since they all require pan removal Ill do them all at the same time. On the idea of having too much oil in it, I already drained about a qt and ran it a qt low and it still did it. So areation due to overfill is kinda ruled out. I like the idea of a few free ponies with the addition of a windage tray. Any recomendations on a tray, pan, pump combo? Thanks for the input.

munday

dang..well looks like it's time to pull out the drill.....

SmokedTires

This is a common problem when mating a high volume pump to a stock oil pan

0ski_dwn_it

If your loosing oil pressure at higher RPMs, THAT IS NOT GOOD. You will evenutally ruin that motor.

Few things that can cause it. Some already mentioned.

1. Too much oil, crank whips it up and puts air into it.

2. Oil climbs the back of the pan, if not designed right, and contacts the crank. The oil will climb the crank, which will throw it back down into the sump causing the same effect when the seas parted for Moses. This parting will leave the pickup sucking air.

3. HV oil pumps are OVERKILL, they are not needed and can fill the top end with all the oil, leaving the bottom starving.

4. Pickup could have broken off, when the oil gets lower at higher RPMs if can suck air again. Drain the oil, and hit the bottom of the pan with a rubber mallet, if you hear something boucing around in there, bingo.

5. The pickup itself can crack, and blead out pressure.

6. Poor bearing clearances, in which case you will get to pull it all back apart sooner than if you keep running it with pressure being lost.

Hope this helps!

TrueBlue ChevyDude

imho 5k is way too low of an rpm to be needin' a windage tray, something else is not right

VETDRMS

I am happy with Moroso's 7qt pan with windage tray and scraper.
Summit part number: MOR-20191 $178.95
http://store.summitracing.com/partde...rt=MOR%2D20191

Good Luck!




[Modified by VETDRMS, 9:08 AM 6/9/2004]

Jvette73

Thanks for all the replies everyone. That Moroso pan looks like its worth considering. I may go that route in the future. The fact is, although ive rebuilt the top end, the bottom end is still factory standard bore with 80k miles on it. In addition to that, a while back I had a cam wipe a lobe and had to replace it, so all that metal went in there and surely some of it is still circulating around. I can see the fine glitter in the oil when I drain it. It still runs great though as strong as ever. I may just take it easy for now and avoid the sustained high rpm untill I can afford to do up the entire bottom end. Im thinkin a 383 kit is in store for the future. At that point Ill seriously do my research on pans, trays and pumps. For now Ill just try and take it a bit easier and enjoy some more mellow driving. It still maintains a solid 65psi under normal to moderate driving. It was just the idea of it maybe being just the filter causing it. Since thats inexpensive and easy to do it was worth a try. Too bad it didnt solve the problem. What kind of 383 kits should I be lookin for? Where can I get the best deal on all the parts to do the conversion?

Matt Gruber

what is the distance, pickup to pan now, and what will it be on the 383?

Jvette73

Not sure what the distance is. Pump came with pickup already welded on. It was the specific part for a 73 vette with 350. If the pickup height would cause this problem would it be because it was too low or too high? What height do you recomend. I can pull the pan and measure with clay. While the pan is off ide like to check the index on the dipstick too. Where should the resting oil level be in relation to the pan gasket surface on the block? If the current mark is in the wrong place Ill just file a new full mark on the stick.

Matt Gruber

i hope others chime in, like clem z., as he has built more motors than me.
i would say 7/16"
i set mine in my 61(in 1993) at 5/16 and it does the same thing as yours. in my 72 the pan was smashed and i couldn't get it that close(lucky me) and it works fine. same pan & pump style.

clem zahrobsky

3/8" from the pan floor. this also happened with my brand new 1966 450HP 427 corvette unless i ran i quart over full because so much oil was being held upstairs in the engine. you need vents in the rocker covers to allow the oil to return to the pan as air must get in so the oil can return.

Jvette73

Hmmm, i wonder if I ran a qt over just temporarly for testing purposes, if the oil pressure stayed up then a cunclusion could be drawn? What would the conclusion be?

h rocks

My money is on the HV pump. I know too many instances of guys running the dang things with high dollar racing pans, and windage trays. The SBC head design just does not allow the oil to drain back fast enough with an HV pump. You don't need that much oil up top. I wouldn't go as far as to install restrictors if you are running hydraulic roller lifters, but I would bet you dollars to donuts that your problem would disappear by installing a stock oil pump.

Jvette73

I think Ill try a pump swap. Ill go with a stock volume pump but add a higher pressure relief spring. That will give me higher pressure at stock volume. I guess Melling is a good brand pump. Any other brand names recomended? Ill use the clay method to make sure I get the pickup set the correct distance from pan floor then have it tack welded in place. Maybe ill add a crank scraper while im at it. Are there any scrapers out there that will bolt in with a stock pan without too much trouble? Keeping the cost down is a concern. It will probably be a few weeks before I can find the time to do the swap but Ill be sure to post back with results when the job is done. Thanks for all the help