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View Full Version : Engine eating oil


MacDaddy
05-19-2005, 10:37:00 PM
Just want your guys' opinions on this.

My engine has been consuming oil (about one quart a week or week and a half). It seems to only occur when I am in a high vacuum situation, like cruising on the highway (I barely have to give this thing any gas when cruising at 70...just barely crack the blades open at 3000 RPM) or coasting down a steep hill in first gear with the throttle blades fully closed. If I drive around on normal flat streets, the engine still burns oil, but at a much, much slower rate. Almost undetectibly slow.

I am running a PCV/breather setup, similar to stock configuration, only the breather does not run to the air cleaner. The valve is working normally and I am using baffled rocker arm covers. That rules that out there (I think).

Next, I suspect the valve seals. Not even 10,000 miles on the heads yet, and there are no puffs of blue smoke coming out the tailpipes at cold startup. I think that is ruled out.

This leaves rings or intake manifold gaskets. I am really hoping it's not the rings (they don't even have 10,000 miles on them either, and piston to cylinder clearance was good).

So today I took off the intake manifold to inspect. The bottom halves of the gaskets were pretty oily, and it looks like MAYBE oil could have been sneaking in that way. I shone a flashlight into the all the valves, and they all look like this (http://pg.photos.yahoo.com/ph/macdaddy1660b/album?.dir=a1d2&.src=ph&store=&prodid=&.done=http%3a//pg.photos.yahoo.com/ph/macdaddy1660b/my_photos)

I also checked the machinework on the intake itself. It checks out ok. I used a feeler gauge to see if there was more clearance between the botom of the intake and the heads than the top.

On the right cylinder bank, however, there did seem to be some threads etched into the upper part of the bolt holes on the intake. Almost like they aren't big enough to permit a good seal. SHould I drill these 1/16" larger? IT should be noted that I never had any problems getting the bolts to line up and thread when I put the intake on last summer.

I just want to make sure this is the problem before I button it all up. If the cylinder heads are toasted, then I will already be half way to having them off.

BTW, I'm using Valvoline 10W-30 and AFR 180cc heads with Corteco intake gaskets. They're the stock replacement gasket for the '79. I read on AFR's site that they require a bit different gasket. Oops. I got the right ones today though.

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Gordon

1979 Camaro Berlinetta

[This message has been edited by MacDaddy (edited May 19, 2005).]

COPO
05-20-2005, 08:36:00 AM
A compression test would tell you if it were the rings. How many miles do you get per qt? Did you know that the 67-69 302 Z/28 engines were built so loose from the factory for more HP that you'd be happy if you got 500 mi to 1 qt of oil. So was your engine built with tight specs like GM went to later?

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Mark D
1970 Z28
http://http://ca.geocities.com/mlvd@rogers.com/ (http://ca.geocities.com/mlvd@rogers.com/)
WTB: 70 SS396 Chevelle 4-spd, flapper hood car, no rag tops, 1-2 owner car.



[This message has been edited by COPO (edited May 20, 2005).]

SHANE 73Z
05-20-2005, 09:34:00 AM
MacDaddy,

First thing that jumped out at me was the fact that you have thread marks in the bolt holes. I had a similar problem that with the machine work done to my heads, a thin intake gasket would not seal at all (especially at the bottom of the port). This was due to the bolt holes holding the intake up. Most intake gaskets are 1/16" thick, but Mr Gasket & Felpro both make 1/8" double thick gaskets. I used a set of these and all is well now.

Do you have screw in rocker studs???

If so are the threads in the intake rocker studs sealed with thread sealer. Most screw in rocker studs are drilled through into the intake port and can pull oil down through the rocker threads. I just fixed that on my car as well.

Hope this helps,
Shane

MacDaddy
05-20-2005, 01:51:00 PM
Ahhh! Forgot about the compression test. I'll do that this afternoon and let you guys know what's up.

Yes, I do have screw in studs, but AFR did not drill them all the way through.

I think I will first start with elongating the holes in the intake. I'm not sure if I have any hood clearance left for double thick gaskets. http://www.nastyz28.com/ubb/rolleyes.gif

Thanks for the replies you guys. And sorry that the post is so long.

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Gordon

1979 Camaro Berlinetta


[This message has been edited by MacDaddy (edited May 20, 2005).]

73454
05-20-2005, 02:17:00 PM
When you installed you pistons, what did you lube the rings with?

1978LT
05-21-2005, 07:24:00 AM
Since you have driving situations where you barely use oil, I'd say the rings are good and seated. The high vacuum situation jumps out at me. I've seen many a intake bottom out on the intake bolts before it seated. I know mine did. Enlarge the holes and give that a shot. If there's any evidence of oil trying to creep in the intake ports, then there's you're problem! Hope it works for ya, you have a nice combo and I'd hate for you to have to go through it again.

gin man
05-21-2005, 05:26:00 PM
Some years ago, I flipped the top of the air cleaner, effectively making it an open arrangement and it tripled my oil consumption. It may or may not have any bearing on your problem but thought I would pass it on.

engine
05-24-2005, 10:23:00 PM
do you travel a lot of highway miles? 1:1 trans ratio coupled with not-so-highway-friendly gears? I noticed higher oil consumption at highway speeds around 3000-3500rpm. I did about 250 miles in one day and my engine ate a whole quart. I have a feeling it's in the engine speed where oil will just flash in the heads to a certain extent and get sucked into the PCV and out the tailpipes.
but what do I know...?

MacDaddy
05-25-2005, 08:05:00 PM
Well the funny thing is that when I take off the PCV valve, it blows out what looks to be vaporized oil or something. I've seen it in my old stocker 350, but it was never a problem.

But in any case, replacing the old gaskets with some new $25 Felpro gaskets SEEMED to do the trick. The oil level has stayed about the same since I got them on.

The gaskets have no sealing bead on them, so I had to use silicone. It seems that they are much neater and seal better than the beaded gaskets in the sense that they don't allow oil to slowly travel up to the top of the intake and leak onto the top of the engine. I think I like these gaskets much more than the Cortecos that I had on there before.

Funny thing is that when I first started her up after putting on the new gaskets, the engine ran a little rough, but the vacuum was about 1" Hg higher than before. I even had to recalibrate the carb because it was running way too rich.

I'm wondering if the carbon on the valves was from a rich mixture, and maybe some oil too. Hmmmmm.

Now I just need to get the carbon off. Looks like I will have to buy some top-end cleaner online, because it's illegal for sale in Ca.

Thank you for the help everybody.

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Gordon

1979 Camaro Berlinetta

1978LT
05-25-2005, 09:02:00 PM
Top End cleaner is illegal for sale in Cali?? You've got to be joking!

Glad you got the oil consumption problem solved! What brand gaskets did you use?

Skaal-tel 79
05-25-2005, 09:31:00 PM
probably illegal since it sends "interesting" chemicals out the exhaust when you fire it up, right?

MacDaddy
05-26-2005, 11:21:00 PM
I used the Felpro performance gaskets. I thought I had already mentioned that. Oops.

Yeah, the chemicals they use in those top-end cleaners are pretty narley. The only stuff you can get in CA is the fuel additive stuff. As we all know, that won't do crap.

Thank God for the internet, eh?

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Gordon

1979 Camaro Berlinetta

Knuckle Dragger
05-27-2005, 01:02:00 AM
<font face="Arial,Verdana" size="2">Originally posted by MacDaddy:
I used the Felpro performance gaskets. I thought I had already mentioned that. Oops.

Yeah, the chemicals they use in those top-end cleaners are pretty narley. The only stuff you can get in CA is the fuel additive stuff. As we all know, that won't do crap.

Thank God for the internet, eh?

</font>

We used top end cleaner all day at work, are talking about the same stuff. We have the Delco and the Motorcraft stuff on the shelves. Hell the 4.0 wouldn't run quiet with out it. Let me know if you need some.



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Dave

There is a fine line between "hobby" and "mental illness".

Eric
05-27-2005, 02:04:00 AM
<font face="Arial,Verdana" size="2">Originally posted by MacDaddy:
Funny thing is that when I first started her up after putting on the new gaskets, the engine ran a little rough, but the vacuum was about 1" Hg higher than before. I even had to recalibrate the carb because it was running way too rich.</font>

That pretty much answers it- if you were losing vacuum previously and replacing the gaskets solved that- it seems apparent that's where the oil was going. Higher RPM also sucks a lot more A/F in a shorter period of time-meaning also there was more oil being sucked in a shorter period of time than at lower rpms.

Hindsight's handy, no? http://www.nastyz28.com/ubb/wink.gif

1978LT
05-27-2005, 05:25:00 AM
Yep you sure did mention the brand http://www.nastyz28.com/ubb/wink.gif Duh me http://www.nastyz28.com/ubb/biggrin.gif

COPO
05-27-2005, 01:58:00 PM
If the compression test tests ok, then it could just be the oil rings.

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Mark D
1970 Z28
http://http://ca.geocities.com/mlvd@rogers.com/ (http://ca.geocities.com/mlvd@rogers.com/)
WTB: 70 SS396 Chevelle 4-spd, flapper hood car, no rag tops, 1-2 owner car.