Oil pump shaft radial play

Discussion in 'Street/strip 400/430/455' started by Electra Sweden, Mar 18, 2023.

  1. Electra Sweden

    Electra Sweden Well-Known Member

    There is a lot of information on the axial clearance on the oil pump gears. However, I have found none on the radial shaft clearance ("side-to-side"). Nothing in the Chassis Service Manual. Reason I am asking is because I can clearly feel the shaft moving side to side, even now when oiled. Considering how bushings this size usually are setup, I see no reason why this shaft should have more than 0.001"-0015" radial play?

    Seems like a tricky machining operation to drill the passage out and install bushings. I suppose running a reamer in reverse like some people do with throttle shaft bushings might be an idea but.... A bit disappointed Buick didn't put bushings in it. Guess I am reaching out as a last resort for input before ordering a timing chain covers.
     
  2. Mart

    Mart Gold level member

    I would think too much slop or play would result in wear all down the line, gears, oil pump pocket & cover. Set clearances tight on pump cover and that unwanted shaft play will allow gear to score cover surface.
     
  3. Stevem

    Stevem Well-Known Member

    How much play are we talking about?
    A sheet of note book paper is like .004”, can you rap a strip of that around the shaft and get it to drop into the pump?
     
  4. Schurkey

    Schurkey Silver Level contributor

    HOW are you measuring shaft radial play? Photos would be welcome.
     
  5. Bigpig455

    Bigpig455 Fastest of the slow....

    Off the cuff, I wouldnt expect more than .002-.004 - maybe toward the latter given the disparate heat expansion rates of steel and aluminum.
     
  6. Electra Sweden

    Electra Sweden Well-Known Member

    So it was worse than I thought. I put an indicator dial on a magnetic stand. Timing cover flush to the steel work bench, trying to put the dial plunger on the apex of the shaft. Got around 0.40 m.m. of radial travel on this measurement, see picture below. It so bad it seems the gear even can scrape the pump housing. So yes, something needs to be done... I used a brand new shaft for the oil pump when doing the measurement. It has a diameter of 12.39 m.m, same as for the old shaft. The old shaft had witness marks, where the shaft was worn around 0.02 m.m. Why would GM use such a weird shaft dimension... Had they went 1/2" at least a standard bushing would have worked.
    20230321_220552.jpg

    As seen here, the walls of the pump took quiet a beating.
    20230321_215835.jpg

    Maybe from the pump chewing something though, the teeth had had its fair share of something:
    pumpteeth.png

    Heavy pitting around the water jack as well:
    20230321_215231.jpg

    So I think this cover can be fixed, but I don't feel it is worth when there is so much involved machining needed when we can get new ones. If this car wasn't worth much economically or sentimentally, I think I would just put bushings on the shaft and RTV around the water ports, measuring oils pressure and hoping for the best. But this is not one of those machines.

    As a bonus, I see the oil pump itself has got some grooving going as well. Maybe we can get away with just milling it down?
    20230321_215401.jpg

    How bad was the situation with the oil pump? It seems it had oil pressure, at least that is what the indicator light showed. I had planned to measure the oil pressure, but the engine worked for like one day before the water pump broke and I ended up here. Would have been nice to have the measurements. I can imagine this pump wobbling around and scraping of material, sending around the engine. And getting lower and lower pressure. Maybe the broken bolt on the water pump saved me from ending up with a boat anchor for an engine...

    On a side note, is this a stock cover? It has a star cast around one of the water jackets:
    20230321_215238.jpg
     
  7. Mart

    Mart Gold level member

    You need a new cover, that one is wopped out.
     
  8. Electra Sweden

    Electra Sweden Well-Known Member

  9. Mart

    Mart Gold level member

    I've never run one.... I sand/resurface and reuse the cover, not with that much drive gear shaft play though.
     
  10. Schurkey

    Schurkey Silver Level contributor

    0.40mm = 0.016". But that wouldn't be the actual clearance, that's the clearance leveraged out a couple of inches.

    But if the pump gear can contact the housing, yes, it should be tightened-up. And that housing looks terrible.

    That probably was a nominally 1/2" shaft, before it had the mill-scale removed, machined true, polished and ready for use. It's like GM using 0.491 distributor shafts--again, they likely bought 1/2" rod, and then ground and polished it to make a distributor shaft.

    I don't know how much the damage to the gear pocket will affect oil pressure. I'm concerned that it would be a significant pressure-leak past the gear teeth affecting both pressure and volume. I tend towards salvaging parts when possible...but I think that cover is "done".

    Thus the sales of "booster plates".

    Perhaps. Examine your oil-pressure switch. Some are activated at ~7 psi, others go lower. The shop I was at had numerous Buick-owning customers who expected us to "turn off the oil light" while refusing to pay for any real repairs. We installed oil pressure switches that shut off the light at lower oil pressure--3, or maybe 5 psi.





    I recognize that I'm on a Buick-enthusiast web site. At the risk of offending...everyone, I have to say that Buick's choice to put an oil pump at the end of two feet of drilled and formed-steel passageways with multiple gasketed junctions, using steel spur gears in an aluminum housing, was unconscionably reckless engineering.

    AT MINIMUM, there should have been a thermally-stable, long-wearing iron insert in the aluminum timing cover for the oil pump gear pockets to be machined out of; and a sufficiently-large enough groove in the block behind the front cam bearing for the oil to flow around without disturbing the load-carrying surface of that front bearing.

    Killing the load-carrying capacity of the front bearing by cutting a groove in the bearing surface, and then making that compromised bearing carry the excessive load of the overhung distributor/oil pump drive gear was insane. A high-school kid could understand that the Buick system was a disaster waiting to happen. When Chevrolet made the same bearing-grooving mistake on cam bearings that DIDN'T have to support over-hung loading, they fixed it within three model years. Buick let it drag on for decades.
     
    alvareracing and Dadrider like this.
  11. Bigpig455

    Bigpig455 Fastest of the slow....

    "I recognize that I'm on a Buick-enthusiast web site. At the risk of offending...everyone, I have to say that Buick's choice to put an oil pump at the end of two feet of drilled and formed-steel passageways with multiple gasketed junctions, using steel spur gears in an aluminum housing, was unconscionably reckless engineering.

    AT MINIMUM, there should have been a thermally-stable, long-wearing iron insert in the aluminum timing cover for the oil pump gear pockets to be machined out of; and a sufficiently-large enough groove in the block behind the front cam bearing for the oil to flow around without disturbing the load-carrying surface of that front bearing"

    I actually think they lasted pretty well given the intended design perameters. Buicks really didnt blow up under hard use any more than Pontiacs, and 50 years later ther are still plenty of unopened engines running around. They didnt intend these things to make it 50 years, and yet here we are....Yep I like the Nailhead design better but ...
     
    1969BSGS and tdacton like this.
  12. Schurkey

    Schurkey Silver Level contributor

    Wasn't really a matter of "blowing up under hard use...". The larger problem was low hot-idle oil pressure under normal use; and long before these engines went 50 years.

    I was dealing with near-zero oil pressure on Buick engines--V6s, iron small blocks, and big blocks back in the 1980s. At that point, some of those engines were still in production although they wouldn't have come to me until they were out-of-warranty. In fact, the first "big news" of Buick doing something worthwhile for oil pressure was--I think--on the '86 V6. I think that's when they finally started grooving the V6 block instead of the wear-surface of the front cam bearing.

    Buick engines have some interesting and worthwhile design features--but the oiling system, and the production-line balance should never had made it past a senior engineer. And the crazy Buick center-of-mass connecting rod, and "punch some holes in the flexplate" balance is easier to forgive based on "normal, Grandma driving" than the oil system screwups.
     
    Last edited: Mar 21, 2023
  13. Electra Sweden

    Electra Sweden Well-Known Member

    I missed the aspect of that groove you are talking about. Picture? Otherwise I agree with your general sentiment, I am seriously unimpressed by the engineering around the oil pump. Another aspect I was thinking of is maintainability. That you actually might have to replace the whole timing chain cover even if it is just the oil pump being the issue. Not built to last, not built to be maintained. It is a shame when most of the rest is a sturdy good old piece of solid iron.
     
  14. Jim Weise

    Jim Weise EFI/DIS 482

    You will get no argument from me that the OE oil pump design was less than ideal from a durability standpoint. But it did allow the distributor to be in the front, without some silly front sump/dual sump oil pan, so there were benefits that went along with the drawbacks. Doing normal maintenance on those cars back in the day with a front mounted distributor was so much easier than trying to lay over the fenders and work on a distributor that was often pinned up against the firewall.

    Considering the cracking/complete falling off of the pickup screen on many cast iron oil pumps in the pan.. it's easy to see that every design has it's issues.. our Buicks have a bolted on pickup tube.

    It was all about packaging, as well as the fact that the 400/430/455 were based on the original 215ci engine design.

    Today, I reject that idea that the oil pump location has a serious drawback for performance use, we have moved away from stock daily drivers for the most part, and we generally are not ignoring the maintenance on these engines, which was one of the biggest factors in the "low oil pressure" stock Buicks back in the day. If the owner decided that oil changes were optional, they paid the price sooner than later for that folly.

    JW
     
  15. Schurkey

    Schurkey Silver Level contributor

    There's a lot of truth there, Jim.

    Every automotive company had their characteristic problems, and for the most part the aftermarket (or enthusiasts) came up with reasonable fixes or at least patches/work-arounds.

    Way too many old Buicks went to the Treasure Yard prematurely due to oil system failures that could have been prevented by better engineering. A shame.
     
    Electra Sweden likes this.
  16. Electra Sweden

    Electra Sweden Well-Known Member

    Sure there are a lot of aspects to consider when developing a product. Having the oil pump at the front is not necessarily a bad idea I think. But for the negative aspects of the pump already mentioned, these might have been a more or less deliberate commercial decisions also. A car company needs their cars to break down to sell new ones. They just need to last as long as what a customer accepts and expects being a reasonable lifespan. And if the oil pump met this criteria for lifespan, the business part of the company will stop any improvements to e.g. the oil pump.

    On the personal front, still at the transition of the denial/acceptance phase of this now :D American car parts are a lot more expensive here so a ProForm cover is around 550USD. And the only company that sells it is one that I have had bad experiences with. And ordering it from overseas is as expensive and can take up to a month. Yeah, will need the weekend to absorb the shock before I order it I think :rolleyes:

    The old cover certainly could be fixed, but it wouldn't be easy and it wouldn't be cheaper. I will store away this cover, so the day when these covers are not manufactured anymore someone could rebuild this one and keep another Buick running.
     
  17. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    If you buy the Proform cover, pay attention to the clearances when you put the pump together, and also the distributor alignment within the cover. Those may or may not be a problem. That may be the downside of Proform products. I know some have used the cover successfully, you just need to check everything and correct if feasible/necessary.

    https://www.v8buick.com/index.php?threads/oil-pump-clearances-and-oil-pressure.326597/
     
  18. Electra Sweden

    Electra Sweden Well-Known Member

    That is a great thread! Distributor alignment would be pretty tricky to check though? What to do, paint the gears on the camshaft and distributor, slide it in, and examine?

    Yesterday I went to a local professional machine shop and showed them the timing chain cover. I kind of knew what the answer would be, but I wanted to be dead sure before throwing out 550USD, and also it was an opportunity to acquire new contacts. They said they sure could put in a bushing for the shaft, but they would prefer to have proper specs on radial play and tolerances. They also gave me a tip about a local mechanic with 45+ years experience on american cars and went there. As expected, no easy workarounds. Everyone estimated that it might soon be as costly or almost as costly as buying a new cover. As for the scratches in the gear house, they are not as bad IRL as in the photo. Everyone gets it is not ideal, but understandably it is hard to say exactly how bad it might be. You know if I had a small machine shop I would sure have given it a try. I would have verified the result with a pump primer and a drill first that I could get decent pressures off course. Having a mill and lathe are high on my wishlist anyway. But not realistic to acquire the tools and knowledge needed before the season starts. So yeah, ordered a new Proform cover. I checked like 8 suppliers, only found a single cover in stock in the whole country. Soon the Electra will be roaring on the roads again!
     
  19. Electra Sweden

    Electra Sweden Well-Known Member

    So I got the Proform cover now. Visually it looks quiet alright except for a mill mark at the water pump gasket surface. RTV should take about that. Crank seal sits on the outside and there are timing marks all up to 12 degrees which are nice improvements.

    Now, the oil pump shaft sits tighter but you can easily feel play. Measuring using the same method as for the old cover I get 0.14 m.m of oil pump shaft clearance. As for gear clearances toward the gear house I am not sure if it is in the green there. I can pinch a 0.05m.m. (0.002") feeler gauge between the cover and the gear on one teeth without using much force at all. Then if I wrap a feeler gauge around the gear when inside the gear house I can slide in a 0.15 m.m gauge but not a 0.20 m.m, so it is more than 0.15 m.m. According to https://www.vortexbuicks-etc.com/Oilpump.htm, 0.13m.m. is max for this measurement. I have to double check the oil pump gear diameter here also. Does any of you know what the clearance is on the TA timing chain cover here? Correct me if I am wrong here, but I cannot see any good reason why this should have more clearance than 0.03-0.05 m.m.

    All in all this is not something I like to see after all this money spent :/

    I was using a brand new driving shaft from Melling for all measurements. On top of this, I just discovered that the old oil pump shaft is bent and quiet badly so! I believe I have been rather careful with it after disassembly, at least I have done nothing violent enough to bend this pretty tough shaft. I wonder what happened here...

    Wonder if anyone had luck retrofitting an oil pump from some other car brand. But that should be a pretty difficult operation.
     
  20. Electra Sweden

    Electra Sweden Well-Known Member

    So I thought I'd share what numbers I have found so far on the specs on oil pump shaft radial play. I have gazed through samples of the Buick Chassis Service Manual in the interval 1956 to 1972. I note that they have very similar documentation for the oil pump, and none to my knowledge contain specs of the shaft play.

    This page specify 0.001"-0.0025" (0.025 m.m - 0.063 m.m.) for the Nailhead oil pump, which look similar enough: https://www.teambuick.com/reference/nailhead_oil_pump.php. No idea how they came up with that number, but it is in the ballpark of what we generally expect for a bushing of that size.

    I e-mailed TA Performance on the subject. I attached a picture of the measurement method I posted in this thread. They briefly replied 0.002"-0.003" (0.05 m.m - 0.08 m.m). Not sure if that is for the measurement method I use or for the actual bore.

    Waiting input from Melling also as I bought the oil pump repair kit from them.

    I can imagine slightly more slop being needed/acceptable on this shaft to accommodate for a slight misalignment with the distributor shaft. But this brand new ProForm cover which has 0.14 m.m. of shaft play, that must be way over top...
     

Share This Page