# Oil Pump connecting Rod



## switchgearguy (Jun 3, 2014)

What is the correct ( exact ) length of the connecting rod from the bottom of the distributor to the oil pump in a GTO 398 ci 1965 engine?


----------



## PontiacJim (Dec 29, 2012)

You may have already gotten your answer, but here goes.

I dug out the stock pump rod from my 455CI which should be the same as all Pontiac 1965 and up -less the 301CI. Then I pulled the aftermarket hardened pump rod I had installed in my 400CI for comparison.

The left rod is factory. Note the "pinched ears" approx. 1 1/4" down from the top. The replacement rod has a grooved ring to identify the top, or distributor end. The factory piece is done this way to keep the rod from dropping down if you need to replace the oil pump and have no need to pull the distributor. The aftermarket rod poses a problem as it will slide right out. Try keeping the rod in the hole and installing the pump as its weight wants to keep it sliding out. You can pull the distributor and drop it down from the top, but why? Simply apply a little heavy grease as needed to the rod to keep it in place, seat the pump top slot with the distributor shaft "tang", and then install the oil pump. Try doing that on your back, engine lifted as high as possible up against the bellhousing, oil pan dropped just enough to get your big hands into the bottom end, and blindly juggle the oil pump shaft while inserting the oil pump & bolts. Only did this once, and that will be the only time!:crazy: You do what you have to do when you only have the one car to drive. Now I own 2 cars so when one breaks, I have a back up while fixing the other. The single man's CYA transportation plan.:thumbsup:

Dimensions of both rods are identical. 7 1/2" long. 1/2" diameter. The bottom of the rod (oil pump side) has a machined hole .475" deep to accept the small centering dowel that you will find machined on the oil pump drive gear. This dowel fits into that hole in the oil pump shaft. The aftermarket rod has razor sharp edges where machined to form the slots at top and bottom. Sliced me up twice just handling the rod -be careful.:cryin:


----------



## switchgearguy (Jun 3, 2014)

Thank you for your response. The engine is on the floor, so working it is easy. My son that was working on it said it wasn't oiling the top end, and thought the shaft was wrong. I have the same two shafts ( factory and replacement) and will mic them and use the best one or another new one. The oil pump is new, but might be faulty. I'll test it for flow. Thanks again, your answer is appreciated.
Douglas


----------



## BearGFR (Aug 25, 2008)

Make sure all the oil gallery plugs are in place, including the "hidden" one that is in front of (front meaning towards the front of the engine) the distributor driven gear.

Bear


----------



## PontiacJim (Dec 29, 2012)

BearGFR said:


> Make sure all the oil gallery plugs are in place, including the "hidden" one that is in front of (front meaning towards the front of the engine) the distributor driven gear.
> 
> Bear


Bear is correct, check the plug at the rear if you had your engine rebuilt as it can be left out. If you had the plugs in the front tapped and use screw in plugs, they don't need to be inserted too deep as this will cut off the oil supply -from what I have read.

You did not state what your running oil pressure was? I had a bad experience with a brand new pump and poor oil pressure to the lifters/rocker arms. Seems a couple of big chunks of rubber "something" got pinned under the check valve on the oil pump -that's that big looking bolt on the side of your oil pump. You can make sure this is free from any bits/pieces by undoing it. Be careful as there is a spring behind the bolt, which puts regulated pressure on the check ball -which looks like a big ball bearing. It won't spring out at you with great force, but just be ready for it. LOOK down inside with a light to ensure no "junk" got in there & that it has not stuck from sitting around.

Next thing, factory pushrods & rockers? Some aftermarket pushrods & rockers have smaller holes to prevent excess oil going to the rockers and keep it in the bottom end.

Is the block original? Might someone have installed restrictor plugs in the lifter bores where the oil is supplied to the lifter? This is another thing done to minimize the oil supply to the lifter and keep oil at the bottom end. Each lifter bore has an oil supply hole. Check to see that they are open and not plugged with a restrictor.


----------

