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Canadian Poncho Homepage -> Canadian Poncho -> General Engine Performance Forum -> Sucking oil from lifter valley past the intake gasket
Post Info TOPIC: Sucking oil from lifter valley past the intake gasket
canpontiac57


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Sucking oil from lifter valley past the intake gasket
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I had the engine rebuilt in my 57 Laurentian about 4 years ago.  It's a 327 that I had it bored it .030 over, 11-1 forged pistons, retrofit hydraulic roller cam, aluminium 23 degree heads.  I has a new, out of the box brand name aluminum intake and a 500 cfm carb topping it off.  The engine burned oil from day one.  I talked to the engine builder and he said the rings likely hadn't seated yet, which I didn't believe but I went with it.  4 years and 5000 miles later, car was still burning oil at the same rate as it did on day 1 after the rebuild.  I did some reading online and discovered one possibility was oil being sucked in past the intake gaskets.  I was bored and it's been raining lots in Calgary so I headed out to the garage 2 weeks ago and popped the intake off and sure enough, you could see that was indeed my problem.  I got my hands on some 10 gauge wax wire, laid it along the outside of the outer 4 intake runners in the head and bolted the intake back on with 4 flat washers the same thickness as the intake gasket.  I tightened the intake just until the washers wouldn't rotate anymore.  I took the intake off and used digital calipers, measured the crushed wax carefully and found that it was .006" wider at the bottom than the top on both driver and passenger sides so I wasn't getting enough clamp load on the bottom half of the gasket allowing it to suck oil into the runners.  I took the intake to a machinist and he re-cut the angles based on my numbers.  He said not only was it too narrow at the bottom, the whole manifold was slightly banana shaped.  He was able to clean that all up for me.  I put everything back together this weekend and boy what a difference; it drives like a different car.  Now it's pulling more manifold vacuum at idle and is way snappier and No More Blue Smoke!  I don't post often but wanted to share this experience in case anybody else out there in Canadian Poncho land was having similar problems.  Between the machining and new gasket set, this was about a $240 fix and maybe 6 hours.  The worst thing was cleaning the old gasket off the heads and intake. I guess the moral of the story is that you can't just buy parts out of the box and bolt stuff together.  Maybe sometime that works but in my case it didn't.  



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DonSSDD


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Edelbrock?

All new aftermarket parts are guilty until proven innocent. Great that you stuck with it and figured this out.

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4SPEED427


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Great job and thanks for sharing that. You may have helped others with a similar issue.

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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

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Amazing and very interesting information. Thanks for sharing.



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66 Beau


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Kudos for diagnosing this one. I don't think I would have ever thought to trace oil consumption back to a poor intake manifold fit, but it makes sense. Makes me wonder how often this might have been an issue in the past. I've had friends whose engines used oil and/or behaved like they had a vacuum leak we could never trace (and finally blamed the cam selection).
Come to think of it, it was popular to use fine grit stones to put the crosshatch in cylinders for "high performance" engines. If/when one of these ended up burning a little oil, it was real easy to blame it on poorly seated rings. Often these same engines got some pretty weird intake set-ups (often second, third or fourth hand tunnel rams, dual quads, or tri-power set-ups), and/or it was not uncommon for builders to mill the heads to reduce the combustion chamber volume and get another few points of compression. That'd make poor intake manifold fitment even more likely.


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canpontiac57


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I didn't want to get in any trouble on the forum, so I didn't list any brand names, but yes, the intake was an Edelbrock Performer.  It was brand new, out of the box.  The first time around, I torqued it to specs using the correct bolt tightening sequence.  I think part of the issue here is that between having the block decked, installing other performance parts (Dart aluminum Pro 1 heads), Edelbrock intake etc, you wind up with tolerance stack-up, for lack of a better term.  I'm sure that you could get away with the angle between the intake and the head being out by a thou or two and still get it to seal but I wound up with everything stacking up the wrong way until I was out by about 6.5 thou which turned out to be too much for the gasket to take up.  I never even contemplated checking the intake to head tolerance when I installed it the first time.  Checking it with wax wire as I described literally only took me 10 minutes and would have saved me so much time and grief if I had have done it.

This time around I have the angle perfect and then for good measure I painted some sticky gasket sealant on both sides of the intake gasket, not just the head side when I put it back together.  That might have been overkill but I'm hoping to never take it apart again.  God help the poor bugger that does someday though, because it will be a nightmare getting that intake off now!

Over this weekend I put on a couple hundred miles, both city and highway driving and I checked the oil last night and it was still at full on the dipstick.  It's a huge relief because it was burning enough oil before that it was fouling the plugs really fast.  On a side note, I was getting really good/fast at gapping and changing plugs.



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