Location of oil passage 425 head - pics?
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500, 472, 425, 368 Discussion, Location of oil passage 425 head - pics? in Cadillac Engine Technical Discussion; I pulled the valve covers on my '79 425 last week to replace the gaskets, and to my dismay found ...
  1. #1
    sixtycyclehum is offline Cadillac Owners Member
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    Location of oil passage 425 head - pics?

    I pulled the valve covers on my '79 425 last week to replace the gaskets, and to my dismay found mucho sludge......just got the car about 6 months ago. I cleaned the valve covers well and tried to find the oil passages in the heads (think they are in the rear by firewall) but was never sure I had found them. There was some oil in the head, but not a ton, it did not spill out or anything when the covers were removed. I added to little oil to the heads and it did drop in level, so it is not plugged. However, if anyone has a pic of where the oil drain hole is, PLEASE post it, if I can be sure of where it is, I'm going to pull the covers again and soak up any oil in the heads and make DAMN SURE those passages are open! I've googled and not found any clear pics. I get a puff of smoke on start up, which could indicate oil pooling in the heads, but more likely it's valve seals (how hard are those to change on a 425? Considering it..)

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  3. #2
    deVille33 is offline Cadillac Owners Connoisseur
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    Re: Location of oil passage 425 head - pics?

    Your oil return passeges are on either end of the head. I don't have any good pics to use as examples, but I believe there are some over on the Rear Wheel Drive Section on one of Benzilla's posts concerning this issue.
    Changing valve seals proceedure is similar to SBC except that rockers mount on shafts.

  4. #3
    deVille33 is offline Cadillac Owners Connoisseur
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    Re: Location of oil passage 425 head - pics?

    All returns in the heads feed back into the valley area. There are four on each head. I checked yesterday when I got to my shop. The returns are quite wide and should allow oil to return to the sump quite readily, unlike a SBC.
    The condition you describe sugggests that the oil used in this car is high in parafin content and the engine was run at low engine speeds. Some people on the OC suggest the use of SeaFoam or like product to flush the sludge from your engine. Put it in about 50 mi. before your next oil change.

  5. #4
    sixtycyclehum is offline Cadillac Owners Member
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    Re: Location of oil passage 425 head - pics?

    I searched but could not find the thread you were referring to. I did see some pretty large holes in the heads, I was looking for really small ones, so it's probably fine.
    When I got the car (Sept), I saw crud on the underside of the filler cap, so I knew it was probably pretty bad. Changed oil immediately, and happened to have a leftover bottle of Auto RX that I added. Have gone thru the rinse phase, and was about 600 miles into the next change when I pulled the rockers. I could see some of it was peeling, but there is a lot. Went ahead and changed again, and added MMO. I'll stick with 1000 mile changes over the summer with MMO. Rear of the intake is leaking like a stuck pig, hopefully it will seal some on it's own. If it does not within 6 months, I'll pull the intake and clean pushrods, lifters and add valve seals.
    Thanks for your help.

  6. #5
    deVille33 is offline Cadillac Owners Connoisseur
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    Re: Location of oil passage 425 head - pics?

    You will probably find sludge in the valley area also.

  7. #6
    steelybill is offline Cadillac Owners Enthusiast
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    Re: Location of oil passage 425 head - pics?

    When you pull the intake, that may be a good time to jack the engine up and pull the pan. All that crap & crud will wind up down there when it drains down. The other thing I would think, is that the screen on the oil pump pick-up may have a lot of sludge collected on it.

  8. #7
    sixtycyclehum is offline Cadillac Owners Member
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    Re: Location of oil passage 425 head - pics?

    I could see into the valley area, and yes, lots of crud. I'd love to pull the pan, as I worry that the pickup screen may be filthy. However, looks like quite a job to get it off . I'm hoping the Auto RX and MMO combo, at 1000 mile oil change intervals, will clean things up pretty well. Engine runs really, really well, plenty of power. Does not smoke under load. Only 69,000 original miles. Get a very small amount of valvetrain noise when engine is first run for the day, noticable going up hills only, with light throttle- can barely hear it though. I'd like to hook up an oil pressure gauge to see how the OP is doing. Any particular ones recommended? I don't have one.

  9. #8
    deVille33 is offline Cadillac Owners Connoisseur
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    Re: Location of oil passage 425 head - pics?

    11
    Quote Originally Posted by sixtycyclehum View Post
    I'd like to hook up an oil pressure gauge to see how the OP is doing. Any particular ones recommended? I don't have one.

    Any quality OP gauge should be sufficient. One of my mechanic buddies used to have an Olde ( meaning really "old" ) Stewart Warner he kept in his tool box. He said in was more accurate than the new ones. He used it for testing only.

  10. #9
    sixtycyclehum is offline Cadillac Owners Member
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    Re: Location of oil passage 425 head - pics?

    WOW- I pulled the oil filter after 500 miles, and cut it open- check out the crud! Looks like I'll keep pulling them at 500 mile intervals until they start looking better!
    Attached Images

  11. #10
    deVille33 is offline Cadillac Owners Connoisseur
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    Re: Location of oil passage 425 head - pics?

    What oil are you going to use?

  12. #11
    sixtycyclehum is offline Cadillac Owners Member
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    Re: Location of oil passage 425 head - pics?

    I've got a stockpile of different kinds, all bought on sale- Pennzoil 10-30 with one qt 20-50 is what was in it for the photo, puralator filter. I've got Castrol GTX 10-40 in it right now, 1 qt 20/50, larger STP filter for a 472/500. Not too worried about the oil type, none will be in for long. I'm going to keep adding a little Marvel Mystery Oil to clean with. Appears to be working!

  13. #12
    deVille33 is offline Cadillac Owners Connoisseur
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    Re: Location of oil passage 425 head - pics?

    I might get some negatives on this, but stay away from the Pennsylvania oils. They are higher in parrafin concentration.

  14. #13
    sixtycyclehum is offline Cadillac Owners Member
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    Re: Location of oil passage 425 head - pics?

    Man, I believe that is a myth. I ran my '68 Deville on Pennzoil for about 14 years (to date). Engine is absolutely spotless. Oil stays clean almost the whole 3000 miles, and I have removed rockers several times.
    Haven't used Quaker State enough to form an opinion.
    Check out bobistheoilguy.com is you are interested in oils, it's great fun. Although you probably are already aware of BITOG.I'm an oil nerd, love reading,thinking etc about oils. I think our Caddies would probably be served very well by Mobil 0-40, but I have not tried yet. I'm going to clean out some of this crud first. It would be a waste of Mobil 1 to not keep it in for at least 5K.
    Have you checked your oil pressure? If so, do you have any averages for the 472 family?

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