Thread: where in the world is the oil coming from?

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Originally posted by Bryan TTM
big cams with lots of overlap cause reversion....usually its black soot crap...poor ring seal would make oil

just an educated guess

ARE YOU TRYING TO SAY IT MIGHT BE RUNNING RICH?

OK, RINGS.

I have to get the heads reinstalled to do a comp test, but for now, if the rings are indeed not sealing, it would make sense why the plugs are getting wet, and with a cam like i have with a longer duration, that you would get oil as far up as the intake runners. But, if this is so, how can the bottom of the manifold and the intake gaskets get all the oil it has on it?

I'm not disagreeing with the assesments, but it seems that the current evidence points to oil getting sucked in from the lifter valley, because the top of the intake gasket, and the intake is soppin' wet with oil.

Now, I will say that on an earlier test with another manifold, I thought I detected a fuel smell on my dipstick. Rings right? If this is so, then I have bad rings and a bad seal on the manifold. Fun.

My 318 was doing much the same thing. The manifold surfaces of the heads had been milled crooked, the surfaces were not parallel with the manifold. Thick gaskets and lots of "goo" fixed it.

if the in take is not setting down and hit the bottom of the intake on the block. it will be held up and when the engine as running the intake ports will suck the oil up and that could be why the intake is not sealing on the gaskets side at the bottm are leaking

Let's go back to Stu Cool's question about the heads being milled. And thanks for reminding me too. I thought for a V8 block the intake manifold surface had to be milled about 71% (actually 0.707 for sine(45 degrees) ) of what ever was milled from the heads? Maybe this is not a problem with a small resurfacing of the heads but if there was a substantial milling of the heads should there not be some milling of the manifold surface also? I am reminded that I have not done this on my 350 and may have the same problem. Let's say the heads were milled 0.100" (extreme), then I would think the manifold should be milled 0.071" on each side to keep the passages and gasket surfaces lined up?

Don Shillady
Retired Scientist/teen rodder

here were i have been there and done it many times i have cut a lot off intakes and by that i mean 0.125 a side the best way is to have the intake and the engine at the shop that is cutting the intake i will not sell or build a engine for no one with out fitting the intake or cut one with out the engine in my shop

the formula i have at my shop and do not used it if the block is cut and the head are new or intake is cut and uesd the formula will not help . it may help for engines that was to gether and well sealing i have not been so lucky .and on in take 0.020 off the intake will seal up ok a little more may move the port matchup off on the small block you can cut the intake side of the head after you deck it on big block you can not do it lip for valve cover on my 85 b block master so you do the intake

Originally posted by DennyW
The formula I'm talking about Pat goes from what you are starting with, and you figure from there on angles, and how much needs to come off.

i do know that. but were are you starting at?? not trying to be a smart ass but why will it mater if the block has been deck 0.030 or more. if the intake is used or like he had it cut .how can you take off metal and cut the intake with knowing this. denny i have cut alot of intakes. for big block s you never know how much to cut off ontill it setting on the engine and fig for the gaskets and . 0.10 less a side for the wedge in

on a 45 angle intake. then it lets say 0.060 up than you take 0.050 off the sides and 0.060 off the bottom of the intake and no angle change just get cut . intake angle is at 44 angle for it to wedge in at the bottom

i will post on this sunday and get the chart i have it is at the shop and will post it .guys buy engines all together and go to diffrent intake and it will not fit. just trying to say sometimes you have to do it like i said

DennyW, great pictures and Pat is certainly right about fitting the manifold to the engine on site since every engine might be different depending on a given rebuild or factory tolerances. The question now is whether "dutchhotrod" can find out or measure if his block has been decked and/or how much the heads have been resurfaced. Pat has a good tip about using 44 degrees instead of the theoretical 45 degrees to get a wedge fit. All I have to do is backtrack to the guy who rebuilt my reads to find out how much he resurfaced them, maybe a lot since we cc'd the chambers and got 73 cc instead of the stock 76 cc on the 882 heads so I guess my heads were milled more than a few thousandths.

Don Shillady
Retired Scientist/teen rodder

Thank you all for your posts. I have some know-how with motors, but I can tell from the posts that I am amoung those that have been around much longer than I. These are intellegent, well thought out ideas that make sense. Ever since I was 17, I've done several cam changes, manifold swaps, etc. and never ever ran into this problem.
I plan on talking to the machinist on Monday. Perhaps the cylinder heads' angle were milled in such a way that the intake surface of the heads did not have enough mating material towards the bottom end of the runners to seal?
I am interested in doing a "leak-down" test, so i'll need to install a fresh set of heads to do it, and the machinist is ready and willing to build a new set for me. The problem is the machinist is not local, so this is time consuming.

if you are having oil splashed that high and its coating the under side of the intake....then that sounds to me like there is a ring seal problem and the block is being pressurized by the leaking cylinder.....do a leak down test as suggested, this will show you what cylinder has a ring problem......and also as stated tight LSA and large overlapped cams will introduce a bit of the exhaust gasses into the manifold, this happens cause both intake and exhaust valves are off the seat together at the begining of the exhaust stroke.....but i think the rings are the culprit here, it can happen that the ring ends arelined up on a cylinder, it has happened to me on my first engine build, just where they ended up seating them selves......good luck with it.....

Gents: thank you for your comments on this: Just so everyone knows, I had the short block assembled ( by the machinst ), because I did not feel comfortable enough with doing the rotating assembly myself. Assembling the heads, timing, adjusting the the valves, etc. no problem. If we are talking about a leak down test, what are the acceptable readings on a brand new 383? The machinist knows that it is ultimately his responsibility to make things right, if the rings are bad, but I need to do this test before I yank this thing out; hopefully I won't need to.

P.S. The cam has been mentioned as a possible culprit. I'm not sure I can totally agree. Here's why: The cam came out of a 327 that had less than 4000 miles on it. This cam never gave me an oil issue in that other motor.The machinst was comfortable with this cam to use, as long as , of course you keep each lifter with it's matching lobe, which I made sure of.

In case anyone wants to know, here are the cam specs.

110 lobe seperation
advertised duration: 285 intake 295 exhaust
lift: 480 intake 490 exhaust
2500 - 6800 range

Originally posted by pat mccarthy
i will post on this sunday and get the chart i have it is at the shop and will post it .guys buy engines all together and go to diffrent intake and it will not fit. just trying to say sometimes you have to do it like i said

try to put it in did not work so i will do one let say0.030 off the head this will be on a 60 angel head 0.17 off intake or head and.035 off bottom of the intake and on 45 angel off head 0.030 off intake 0.030 and 0.49 off bottom. i like to take more off the bottom i ues RTV here and like some gap here so i know it will not hit the bottom first and hold up the intake