Thread: SBC Oil pressure loss.. What the Heck??

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Hmmm.....that has me thinking... I installed an aftermarket intake too. There is a chance (small one) that the distributor mounting surface is higher (further away from the oil pump) than the original. That doesn't sound likely though...just thinking out loud.

Shouldn't be a difference, but anything is possible. Compare it to your old one. Is the distributor seated all the way down?

Don

Originally Posted by Itoldyouso

Shouldn't be a difference, but anything is possible. Compare it to your old one. Is the distributor seated all the way down?

Don

That has been my exsperiance too..usually they need shimmed up a tad for proper clearance...I guess its not out of the question for it to be the other way.

I would guess the problem is in the distributor somewhere..not engaged far enuff or broken inside......is there a shear pin inside of those?
Might be sheared off and still binding and spinning the pump some..?

Not sure where the shear pin is or if they even have them in there on that model......or if the shear pin effects the timing gear, rather than the pump rod?

When I install a new oil pump, I check the side clearance of the pump shaft before I torque the pump. I just had a 406 recently with near zero oil pressure. I pulled the eng twice, checked bearings changed bypass, changed cam bearings, changed oil galley plugs...all of which were already new. Turned out to be a bad "new" pump. Installed a milodon STD pump and it idles 40 psi hot. The previous pump was a milodon high vol unit which had a defective bypass piston. Usually when psi near zero it is a oil galley or rear cam bearing alignment to changer issue so I am told.

take and measure down the dist well till you fall in to the oil pump slot on the pump drive now mark it were the dist seats on the intake .this is the over all the dist need to be to reach the oil drive . the dist gear helps hold the pump shaft so it longer then the over all so you can work out . subtract the over hang of the gear to dist drive or just take out the roll pin .drop the dist in and see it reachs the oil pump drive . so if this make s it to pump then it 3 thing s dist gear is screwed up or cam gear .or the cam is to far front or back in the engine .this can happen if a thrust shim was left off the top timming gear or a thrust shim was added to the timming set and not cut for it. this stuff we have to do all the time on tall deck big engines were i cut the dist shoulder off on the lathe or buy adjustable collar dist. when you get it in ..you do not want the dist bottoming out on oil drive and the gear pattern should be in the mild part of dist gear .use lay to check or red sharpy marker . about all the away down and then 060 up then add gasket gets you close on a good pattern on the gear

Very good points, Pat. In fact, I have an MSD distributor for a sbc in the shop that has and adjustable collar. You loosen a couple of set screws to move it up and down. I had never seen that before.

Don

Originally Posted by Itoldyouso

Very good points, Pat. In fact, I have an MSD distributor for a sbc in the shop that has and adjustable collar. You loosen a couple of set screws to move it up and down. I had never seen that before.

Don

yep on the big engines with tall decks we cut the collars off the dist and make a slip ring or just buy the msd . i have cut vertex mag dist down for slip rings if the intake has enough meat you can sink the dist well to

hope he did not stick a chevy II v8 oil pump drive in it there shorter then a sbc. bbc are longer then stock sbc. had a customer that did just that . i cut out a stub drive it reach the sbc shaft next day was race day he said no way he was not going.... it work.. told him take it out and not push his luck

Thanks for all for the suggestions. Sometimes it's hard to see the obvious (for me anyway....) I tend to get wrapped around what I'm seeing instead of what's really there.
It's cold and icy here now, when it warms up in a day or two I'll take some measurements. I like the idea about taking the roll pin/gear off of my distributor and see if it meshes with the oil pump shaft. That would take out some of the variables. Worst case (and I dread it) I'll pull the pan and replace the drive shaft. If I'm lucky, I can raise the engine up enough without taking it out of the car.....but I'm not typically a lucky person. :-)

Here's an update... I like to see updates on peoples posts, so I figured I'd do it too. Apparently, when my son and I were priming the oil pump the primer slipped up out of the slot in the pump shaft and spun around on the top it. (don't know how the heck that happened, but it did) Anyway, the top of the shaft was mushroomed out a little and it wouldn't slide up inside the distributor gear. The distributor wasn't seating all the way down on the manifold. (how did I miss that? Who knows?) I could have pulled the shaft and put in a new one, but I didn't. I removed the gear from the distributor and drilled it out a teeny bit below the level of the roll pin that holds it on. After that, the distributor almost fell in like it was supposed to. We've got great oil pressure, and it runs like new. Thanks to everyone that offered suggestions, and helped me to pull my head out of my arse long enough to see the obvious.