(pics) 3900 and 3500 oilpump comparison

[23TrackroadsterV6]

The Barnes small block chevrolet internal dry sump pump that several sprint car engine builders used in the late 70's and thru the 80's was pretty much a pump with two sets of gears, with one set stacked on on top of the other seperated by a plate. These gears were driven of the cam/magneto by a hex shaft. The lower set of gears scavenged oil out of the pan and sent it through a -12 fitting out the side of the pan to a remote mounted tank, the other set of gears pulled oil from this remote tank and returned it to the oil galleys in the engine.

[Driver_10]

Seems like you got quite the plan. You said something about having a some sort of internal pump that acted like a dry-sump. Got any pics? I've never heard of anything like that.

[23TrackroadsterV6]

[23TrackroadsterV6]

This is a 3900 oil pump modified to have the intake on the bottom and the by pass valve external. This allowed me to build a shallow pan for my track roadster. The pan is approx 17" long X 12" wide X 5 1/2" deep and oil is 1 3/4" deep in the pan, giving me about 7 quart capacity. It will have trap doors for oil slosh control as well as a crank scraper and windage tray.

[23TrackroadsterV6]

[23TrackroadsterV6]

I'm just looking to stay with a wet sump, but wanted the shorter bodied pump so I can make the pan shallower than if I run a 2.8/3.1/3.4 pump.
I doubt the volume it moves would be an issue.

[Driver_10]

If your gonna modify an oil-pan then what about going with a dry-sump pump? NRC (nutter racing engines) sells brand new, "in-house", american made, CNC pumps for an affordable price. You can get a 3-stage pump with cog pulley and mandrell to fit the 660 for $588 shipped w/ 0ne year warranty.

Their 4-stage pumps are about $100 extra. Try buying the same thing from Moroso or Barnes and you'll spend $1800 for the pump alone.

[23TrackroadsterV6]

Wondering if anyone can tell what model and year the shorter oil pump is off of? I'm currently building a RWD 3.1 and am fabrication my own shallow oil pan and this oil pump would be ideal for what I need.

[AaronGTR]

Hate to drag this topic back up but wanted to add something I just found.

In the "engine mechanical specifications" section in my manual, it's say oil pressure-warm: 103Kpa or 15psi at 1100rpm.

So apparently the technical writers for the manual screwed up and gave two totally different oil pressures in different areas of the manual. I'm more inclined to believe the lower number since I've never seen 60psi from mine.

[sprucegagt]

Your idle values are the same as mine.

[AaronGTR]

I have a feeling you are reading that spec wrong. There is no reason for a 3400 to have 60 PSI at 1850 rpm. If it means anything, my engine will only come close to 60 PSI at redline. It normally pulls 30-35 PSI at 1850 rpm and that's with Castrol 0W-30 and PF-52 filter.

I know how to read. But hey, if they happened to make a mistake in the manual and most 3400 owners don't see pressure that high, then that's another matter. But these are the exact words from my manual in the section on oil pressure testing...

"Ensure that the engine is at operating temperature before inspecting the oil pressure. The oil pressure should be approximately 414 Kpa (60psi) at 1,850 RPM using 5W-30 engine oil."

So what do most people with 3400's see for oil pressure? Like I said when my engine is good and hot my needle sits below the 25 mark, and it goes up above the 35 mark usually above 3000rpm and under heavier throttle. So probably 22-23psi at idle up to 40-42psi... as best I can tell with that gauge scale. That's still less than you are seeing spruce, which is why I suspect my pressure is too low.

[sprucegagt]

Sometimes you need more pressure though. I've been contemplating shimming the spring in my pump... or just replacing the pump or trying a 3500 pump. According to the manual for my 2000 GA I'm supposed to get 60psi at 1850 rpm. My pressure gauge has never shown over 50psi though all the way to redline, and when the engine is hot at idle I only get 25psi or just under. It's been that way since I installed the gauge. I've sent a couple oil samples out for analysis and they've shown higher than normal wear metals. Plus I had a set of crane gold rockers go bad on me. I'm wondering if low oil pressure is contributing to this problem. Also thinking I may want to change oil weights.

I have a feeling you are reading that spec wrong. There is no reason for a 3400 to have 60 PSI at 1850 rpm. If it means anything, my engine will only come close to 60 PSI at redline. It normally pulls 30-35 PSI at 1850 rpm and that's with Castrol 0W-30 and PF-52 filter.

[IsaacHayes]

If the VVT pumps is too much, then the 3.4TDC would be way too much then....

[gectek]

i used a new melling. then used a 1/4 in washer. should shim it about 4-5 psi over normal at idle, and raise the others about the same. have not ran the engine yet tho

[AaronGTR]

So here's a question. For my particular problem, do you think I should try using a non-vvt 3500 oil pump, or stick with the 3400 oil pump (maybe get a new one?) and just shim the pressure relief spring? And how much do you have to shim the spring to get it up a few psi? Ideally I'd like to be able to get 60psi out of it around 1850-2000rpm like I'm supposed to be seeing.