GT3 Oil Pump - Long term results wanted

Tom C. · 02-21-2007, 03:49 PM

I'm currently building a 2.5 Short Stroke motor and have been told that a GT3 Pump is the one to use. As usual, everyone wants the latest and greatest . . . but I also know "leading edge" technology can also be accompanied with some pain.

Just to share . . . here's my application for the pump.

7R Case
66mm Crank
Carrillo Rods (2.2 long)
964 Intermediate Shaft
Mahle 89mm P&C (10.3:1 ???)
38X38 Ports, 40X46 Valves
Intake is TBD . . . 40mm PMO's vs. modified 2.0 MFI setup
Exhaust is TBD . . . SSI vs. headers.
Single plug Ignition w/ Bosch CDI.
Cams will likely be a Mod-S grind.

So I'm interested in feedback from anyone that is running this GT3 pump in their rebuilt motor . . . both positive and negative.

Thanks in advance,

Tom

ErVikingo · 02-21-2007, 04:36 PM

That's what I run on my race motor. No problems whatsoever under stresses normally not encountered in road driving (performance or otherwise).

Tom C. · 02-21-2007, 06:22 PM

Juan,

Are you running an engine oil cooler or do you have a oil filter console? I ask because it seems like that could be an area where some serious leaks would happen, based on the oil pressure the GT3 pump can create.

ErVikingo · 02-21-2007, 08:15 PM

Neither, remote tank up front with dual coolers.

I did run a 965 oil pump with a console (1969 unit) with no problems.

Tom C. · 02-21-2007, 08:42 PM

Ok, so you were not running an engine oil cooler . . . and that's my concern. Is anyone running an engine-side cooler with a GT3 pump?

Tom C. · 02-21-2007, 08:45 PM

By the way, thanks to Juan for the info

ErVikingo · 02-21-2007, 09:21 PM

No problem. That's what the forum is for.......

MBruns · 02-22-2007, 05:09 AM

We run them all the time, all positive results, some with coolers most with the filter console. The pressure is adjustable at the relief spring, and if you are running the thermostat the cooler wont see cold oil anyway. The other plus is they are cheaper than the 964 pumps, they do need some case clearance but nothing big, they can be used in the early sand cast 2.0 and up.

Mike Bruns JBRacing.com

Tom C. · 02-22-2007, 12:00 PM

That's good new . . . I picked up a used GT3 pump from a local guy for a fair price and had it disassembled and checked . . . everything looks good so back together it went. Yup, I'm having the Case clearenced for the pump and I had my Cooler pressure checked and ultrasonic cleaned.

I think the only other piece will be to make sure the pressure relief springs are the correct ones. I've read about short vs. long springs but what are the correct ones to run with this pump?

I've also heard about different "cap nuts" that have a different seat depth for the spring, which would affect the spring pre-load, but I can't imagine this would be significant enough to really make a difference. I think the length of the spring is probable the only decision at this point that really matters.

Any thoughts on this?

BTW Mike, I love that Billet Twin-Plug Dist you've got. Thinking about going Twin-plug, just in case . . . need to see how much $$$ to machine the heads.

MBruns · 02-22-2007, 01:39 PM

Tom, we update to the latest springs,pistons,hex style caps and adjust/trim the spring to set the pressure. Alot will depend on how big the squirters are and engine bearing clear.etc... as to where you end up. The distributors are working very well, the cost to machine twin plug is 350.00 for the set if the heads are clean and apart, which includes the holes in the lower covers.

Thanks, Mike Bruns