65GS.com - Buick Gran Sport Enthusiasts!
Drivetrain => The Nailhead => Topic started by: WkillGS on January 31, 2009, 07:22:12 PM
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I completed a 401 rebuild recently, and thought I would share some tips.
The Flame Red 66 GS I bought in 1996 had low oil pressure. It drove fine, but the gauge showed only 10-25 psi max. Kinda scary. Glad I put a oil pressure gauge on it(??). Even tho if I had not, I would've thought all was fine...
I bought a oil pump and pickup from Carmen Faso (1998??).
Now fast forward to 2008 when I FINALLY commit to getting this car back on the road! (the curse of having multiple projects!)
I compared a new Melling oil pump from Autozone to the one I got from Carmen years ago. Both are Melling pumps. Gear lash and gear-to-housing clearances are similar. The only difference I could detect was the relief spring. Carmens pump was shimmed to increase the oil pressure, so I did the same to the new Autozone pump. I drilled out 2 washers, and slightly ground down the OD of the existing spring retainer...the spring bore is stepped, so the OD of the retainer needed to be reduced so it could be pushed in further. The 2 washers were placed on top of the original retainer, and pushed into place. The housing was staked to hold them all in place. Once the pickup is bolted on (use some loctite), it'll hold it all in place.
Before:
(http://65gs.com/GS_Gallery2/albums/userpics/normal_DSCF0890.jpg)
After:
(http://65gs.com/GS_Gallery2/albums/userpics/normal_DSCF0891.jpg)
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So I bolted the pump into place, and installed the mock-up distributor. The distributor didn't have a gear on it yet, since I wanted to check the alignment and fit of the oil pump and shaft.... Since there had been some reports that the oil pump shaft might bind.
Once the pump was torqued down, I found the shaft was binding. At first I thought the oil pump shaft was hitting the bore in the block. So I elongated the holes in the pump to adjust alignment, but that didn't fix the binding! I eventually realized the casting/machining of the pump was not compatible with my particular block!
I had to grind a relief into the pump housing in order for it to fit my particular block:
Before:
(http://65gs.com/GS_Gallery2/albums/userpics/normal_DSCF0913.jpg)
After mods:
(http://65gs.com/GS_Gallery2/albums/userpics/normal_DSCF0914.jpg)
In conclusion....check the fit of your oil pump using the distributor without the gear installed to ensure proper alignment!
I don't know if it was my particular block, or the Melling pump that was at fault.
Just check it to be sure!
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Now for the oil pump pickup....
When I tore the 401 down, I did not find any excessive bearing clearances to explain the low oil pressure. I did notice the oil pan was dented up and the oil pump pickup was tight against the oil pan. Maybe that was the problem?
I did buy a HP pickup from Carmen that used a larger diameter tube, and some additional holes in the pan pickup:
(http://65gs.com/GS_Gallery2/albums/userpics/normal_DSCF0908.jpg)
However, I decided to use the original pickup, and use Carmens in another build.
To ensure the pickup was the proper distance from the bottom of the oil pan, I welded washers onto the pickup. These were later ground down for 1/8" pickup-to- pan clearance:
(http://65gs.com/GS_Gallery2/albums/userpics/normal_DSCF0962-1.jpg)
At this point, I know the oil pump shaft turns freely without binding, and the pickup will be the proper distance from the bottom of the pan....even if the pan should happen to get pushed up by a speed bump or curb! Pressure is bumped up for extra security with the spring shims. Spinning the oil pump with a drill is giveing me 40 psi.
Engine will be fired up soon! Reports to follow...
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Carmens latest design of the oil pump pickup can be seen here:
http://cgi.ebay.com/ebaymotors/Buick-nailhead-rear-sump-GS-oil-pump-pickup-401-425_W0QQcmdZViewItemQQcategoryZ140691QQihZ001QQitemZ110332338268QQrdZ1QQsspagenameZWDVW
(http://gransports.com/GS_Gallery2/albums/userpics/Carmen_Russ_Oil_Pump_pickuo.JPG)
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Carmens latest design of the oil pump pickup can be seen here:
[url]http://cgi.ebay.com/ebaymotors/Buick-nailhead-rear-sump-GS-oil-pump-pickup-401-425_W0QQcmdZViewItemQQcategoryZ140691QQihZ001QQitemZ110332338268QQrdZ1QQsspagenameZWDVW[/url]
([url]http://gransports.com/GS_Gallery2/albums/userpics/Carmen_Russ_Oil_Pump_pickuo.JPG[/url])
Looks nice.
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'Only' $155
I'm cheap!....gotta spread my funds across a dozen cars. ;D I think you know where I'm coming from...
Melling has a bunch of pickups avail, maybe some can be modified for our GS's?
Wish I could find more pics of Melling oil pump pickups.....
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AWESOME POSTING WALT!
This is good stuff and the time you spent to share what you've learned will help out many on this board.
I personally need to drop the pan on my vert. this Spring and check the pump and pickup. I have rocker tick for about 10 minutes after start-up and although I realize some of this is normal, the fear of lack of oil from the bottom to the top of engine scares the hell out of me.
Thanks again Walt,
Chris
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Walt,
Thanks for the great information about the oil pump and pickup tube. I will be rebuilding my 401 this spring for the silver convertible. I will definitely make these changes. I seem to recall that someone told me that it might be a good idea to also tack weld the pickup tube to the pump. Your thoughts?
Thanks,
John
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Walt,
I got my pump and pickup from Carmen as well, around 1996 or 97. I never checked the pump shaft/distributor fit during assembly to see if there was any interference. I bolted the pump and pickup on, then buttoned up the bottom end. The distrib drops right in where I have #1 at TDC. I haven't primed the pump yet, so the distrib needs to come back out. Is there anything I can do at this point to make sure the shaft isn't binding?
Carmen went through the distributor too, adding a Pertronix unit to replace points.
Mark
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Mark, with the distributor out, you should be able to turn the oil pump with a screwdriver.
When I put my blue 66 together, the oil pump shaft rubbed against the block. I only had to loosen the mounting bolts and center the pump.
It had gotten a new TRW pump when I did the rebuild in 1979. Oil pressure slowly dropped over the next few years. A fresh pump with a shimmed spring did the trick. Runs at 40-50 psi.
John, I guess tacking the pickup on could be done. That's often done on engines that have press-in pickups.
I just used locktite on the bolts.
A better method would be to use bolts with safety wire. Wish I had though of that a month ago.
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I feel compelled enough to be up at 4am to write this little piece. We are talking about one of the aspects of longevity. 1st. off doing what Walt did is fine with the stock pick-up tube diameter. But for the larger tube diameter there has to be something done to cut down the restriction caused by the washers. It makes no sense to put in a larger tube & then have washers that are a smaller diameter. We would be going from large to small to larger again. With some smaller washers you will have oil pressure but will have cut down on the amount of oil volume, by as much as 50%. Volume is as, if not more, important than pressure. Blueprinting an oil pump is enlarging the passage to the same diameter as the outer plug diameter & cleaning away all the casting "Flash". Smoothing all curves for a more gentle flow & checking gear to cover clearances. Another thing no one thinks about when raising oil pressure is the thin plate that makes up the cover. More pressure will easily distort this plate. We make a 3/16ths. steel ring to go around the outside diameter & held down with longer cover plate bolts. Loctited & wiretied. 5PSI oil pressure at a HOT IDLE is OK. As well as 25PSI while cruising & not putting the engine to too much abuse. As long as when you touch the go pedal pressure immediately rises. These things lived for 200K plus with an average of 35PSI. I know some that have lived to over 300K without a rebuild. The most common problem with low oil pressure when all the crank bearings are OK is more likely caused by cam bearings. Most have all the bearings installed & then pop in the cam & hope for the best. Very few ever check for clearance or, again, binding issues caused by cam bearings or cam bearing journal diameters. This is where you end up with insufficient oil pressure problems. The cam bearings get "Wiped" & the clearances become TOO much. Worst case the bearing or bearings will spin in the block. You need to install the rear bearing 1st. of course, but stop at the 2nd. from the back & install the cam & check for binding. You may be surprised at what you find. Do each bearing in turn ending at the front. We just spent over 4 hours doing just this to make sure there was no binding & sizing as nec. I say it all the time. When you think you have covered all the details go back I BET YOU MISSED SOME!!!!! What Walt has given is often overlooked advice. The only thing I can add is to make it easier, my opinion, is to cut a piece of thinwall pipe with the correct wall thickness to put in place of the washers. Easier to fit & size & the pick-up tube will keep it all in place. Just use Loctite as Walt mentioned & wire tie. We lost our last engine because of the bolts somehow coming loose. 50PSI is more pressure than any "Nail" needs even in "Racing" trim. What we have been blessed with is an extremely efficient oiling system. Oil goes to the cam & crank before going any place else. But, TOO much oil pressure is no good either as it will pass TOO fast & not have enough time to cool. One problem with higher oil pressures is at the heads. The drain back holes provided for at the pushrods are not large enough for oil drainback, especially when cold. The oil will actually fill the valve cover to the point of being sucked into the PCV system & you know what that causes. Billows of blue smoke that you will pull your hair out trying to find the cause. We are HP inefficient as it is, why would you want to lose more HP through parasitic HP loss with all that oil running down over the cam, good, & the crankshaft, bad, that's a HP loss. Everything comes with it's drawbacks. We don't have the pleasure of picking up some catalog & writing a check to make up for the mods we are looking to do to increase the HP. We need to think about the way we are going to make HP & the drawbacks associated with them. Every action has a reaction. Know what I mean??? As far as too much oil up top is an easy mod. Get a, about 1/4" set screw, drill a .030"-.060" hole in it. Thread the front rocker oiling hole in the head. This will restrict the amount of oil when cold & won't overburden the drainback. This has absolutely no effect on hot oil lubrication as the oil is thinner. Another problem is oil leakage at the rear of the head. How many times have you gone crazy trying to find an oil leak thinking it was the rear main or the filter adapter on the block when in fact it's oil weeping from the blocked hole from the rocker oiling hole that's not going anywhere's & just dead ends at the block. This is especially a problem with the composite head gaskets. Oil will weep it's way through the layers of gasket material. Easy fix. Take the same set screw & not drill a hole in it. Install the same way as mentioned. Now the oil can't go there. I don't know why the gaskets weep as there is really no oil pressure there, but it seems to happen mostly when O/P is increased. These set screws have no place to go. On the one end they can't go past the head bolts. On the other end they can't go past the rocker stand bolt. I do this on ALL, even stock, rebuilds. Eliminates an oil leakage comeback. We have gone as far as drilling 1/4" holes in the "Vee" of the heads to get oil to flow to the rear rather than down the pushrod holes. All to gain back some parasitic HP loss.
I need to stop now as it's getting nearer 6am & I need to take a shower to wake my dead ass up. Goodnight or Goodmorning depending on where you call home.
Tom T.
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Thanks for the additional info Tom!
I did drill out the spacer washers so they were at least as large as the existing retainer. Next time I'll use a section of pipe. Good idea.
I'll be watching for head gasket weep as well.
I had issues with the cam bearings as well...I'll put another post up later.
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One other thing I forgot to mention this early am. You MUST check clearance on the rear two rods for clearance, ESPECIALLY with the Melling pumps & most definitely with aftermarket rods. A minimum of .035" is the norm & .060"-.070" with aluminum rods. There is enough casting on the pumps to remove a "Reasonable" amount of material. Just because it doesn't interfere while putting the engine together & you didn't check & after you get it running & warmed up it's a real pain to pull the pan. Much easier to do it now with the engine on the stand.
Tom T.
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Very interesting topic. I would add that when I bought my GS in Arizona, my cousin (who lives there) wanted to get it running. He's a tech at the GM Arizona proving grounds and loves doing this stuff. The car had not been fired in about 14 years so it was a personal challenge for him. First he removed the spark plugs and barred it over to be sure it wasn't seized. The crank spun freely. Then he removed the coil wire and turned it over and found the oil pressure light was on. He put a gage on it and confirmed that it had no pressure. So he dropped the pan and found the pickup laying in the bottom. The bolts had worked themselves loose and the pickup simply dropped to the bottom of the pan. He reassembled it and it works fine.
I'll bookmark these tips for reference when I tear the engine down and rebuild it.
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Bump. Received a PM about low oil pressure, so bringing this thread back up.
Had another thought, if you call Carmen or Tom, bounce this off of them....
Is it possible to test the oil pump while it's on the car?
I'm thinking: remove the oil filter adapter, bolt on a flat plate with a fitting on it for a pressure gauge, remove distributor, and spin the oil pump with a drill.
This might (if it works) determine if the low pressure problem is in the pump or elsewhere in the engine.