(pics) 3900 and 3500 oilpump comparison

[Driver_10]

Since Im modifying my 3500 for oil-jets on all 6 cylinders, I was needing a pump with an adaquate flow rate.

After a lot of searching I believe that Ive found candidate for an oil-pump. The 3900 uses oil-jets stock so the pump will have the flow that I require. Here are some pics comparing the two...

Heres pics of the 3900 from the top (flange side)



Heres some pics of the 3500 from the same angle



Heres some pics of both from a side profile. Youll notice that the 3900 oilpump is a bit shorter. Im not sure how that will affect install on a 3500 block



And heres a couple more to compare pump size

[91LQ1Lumina]

Not to be an ass or anything, but those are photos off of my LZE 3500VVT motor not the 3900. I am fairly sure they would be the same, but just so you know. Again not trying to bust your balls or anything like that.

[Driver_10]

Not to be an ass or anything, but those are photos off of my LZE 3500VVT motor not the 3900. I am fairly sure they would be the same, but just so you know. Again not trying to bust your balls or anything like that.

Oh, not at all man. In fact, your the one that posted those same pics after I posted a thread asking for them. Im able to post my findings because of your help.

Id like to thank you again for that.

(LZE VVT3500...got it)

[SappySE107]

A 3.4 DOHC pump would also work and probably has a lot more flow than either of those. I don't know how much you would need. The 3500/3900 VVT should be enough.

[Driver_10]

Since Im having my block machined to accept oil-jets, Id imagine that the vvt3500 would have an adaquate pump since it comes "stock" supporting oil jets across all cylinders.

Do you have any pics of the 3.4l DOHC oilpump by any chance? I thought that block revisions to the 3500 made them incompatable with older style pumps.

[SappySE107]

The 3500 is the same as the 3400 as far as oil pump looks. The 3.4 DOHC is a bigger version of that. I will get some pics in a sec.

[SappySE107]

Sorry for the delay. I think you know which is which:P

[1988GTU]

hrmmmm....

[geoffinbc]

Don't get obsessed with cranking out huge oil volume. The oil jets have poppet valves and will only open at a certain pressure. They will not bleed off pressure at idle. All of the stock pumps easily make full pressure by 2000RPM there is no need to go bigger. If you do you are just wasting power and introducing heat and air into the oil when it gets forced through the pump bypass and back into the pan.

[gectek]

shim the spring = more pressure

[Driver_10]

Don't get obsessed with cranking out huge oil volume. The oil jets have poppet valves and will only open at a certain pressure. They will not bleed off pressure at idle. All of the stock pumps easily make full pressure by 2000RPM there is no need to go bigger. If you do you are just wasting power and introducing heat and air into the oil when it gets forced through the pump bypass and back into the pan.

Volume is a bit important for this motor. This motor is being built to red-line at 7500 w/ 7200 shift-point. The tollerences were made to be looser which also translates to higher oil-sheering rate.

I dont need to boost the oil-pressure as much as I need the additional oil-flow. Shimming the oil-pump relief-spring can do more damage than good too. If pressure is increased "too" much, then the babbit material can seperate from the face of the berrings and cause catastrophic failure.

[AaronGTR]

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.

[Driver_10]

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.

Youve probably got a lot of oil-sheering from loosened clearances.

[gectek]

oil shear will also break down the additives faster and cause oil overheating....i doubt he has that.

[Driver_10]

oil shear will also break down the additives faster and cause oil overheating....i doubt he has that.

If oil pressure is low at part idle and drops considerably at high rpms, then excessive sheering is the most likey cause. Had his pressure been low yet stable from 2000-redline, then I would diagnose the pressure relief spring.

You have to remember that an engine's oiling system is a regulated "oil-leak". The looser that an engine gets over time, the more oil will "sheer" away and leak off at the clearances between the berrings.

You can shim a pump much to your heart's desires and still not get adaquate oil-pressure IF there isnt enough flow passing through the clearances to form restriction and build pressure.

Pumps can only produce oil flow, NOT pressure.