I have the engine short block rebuild last summer at one machine shop and the heads at another. After I assembled it - heavy oil burning. The machine shop took it apart, mic'ed everything and found nothing. Put in different rings and it ran fine for about 300 miles. Now it is puffing oil smoke after sitting at a light and at idle you can see a faint blue smoke coming out.

The heads were totally machined with new guides, PC seals, valves, springs, retainers and locks. Does anyone have experience with these type of seals for leaking?

The intake has been changed 2X with different ones and a different brand of gaskets, so doubt it is the intake.

The short block like I said has been apart 2X's and measured and remeasured now with different rings.

Sure would like some advice of how to approach this as it really takes the joys of a new engine away quick!! Thanks.

 

Inspect the plugs. Are all of them oily? Only some? How are they oily? Facing the intake valve? This will help us identify some possible causes. Doesn't have to be the rings. Could be a bad PCV system, valve seals, etc.

 

Thanks, I will look at the plugs as soon as I can. Might be early next week as I have to leave town on Friday.

Zwede, what can go wrong with the PCV system. I have a 73bb. One line goes to the charcol cannister and to a full vacuum port on the carb. The other line to the PCV valve - cannister - carb port. I changed the PCV valve several times to no affect.

As I mentioned I am using PC seals. Any experience with these leaking??


[Modified by bigvette1, 9:19 AM 4/22/2004]

 

My 71 was sucking in some oil through the PCV. There's always going to be some oil going in that way, but I thought mine was excessive. The inside of the intake was always oily. I redid my PCV system which greatly improved it. I modified the valvecover baffle to a closed box with several small holes on the bottom. The box is filled with steel wool to help separate oil from air. Then I use a breather filter stuck into the valvecover and a more restrictive PCV valve.

When I bought my car it was smoking badly. On mine it turned out they had used regular valve seals with dual springs. The inner spring shredded the seals.

 

One thing I can stand about the PCV is there really is not ratings to be found for them so you can't match them to your vac level. If you eng doesn't pull enough vac the valve will be open all the time.

So you have a baffle for the PCV?

 

Zwede and Ferve -

I have chrome valve covers on the car and there appears to be a baffle under the PCV hole. My engine is running 9.5:1 CR with the Crane 272 cam, 2.19 by 1.88 valves, dual Comp Cams springs PC seals with stock stamped steel rockers.

I put on a Edelbrock Performer 750cfm (not Q-Jet) on with a stock intake. (adapter used) I did this so there was almost zero chance of pulling fuel via the boosters of the Q-Jets and washing the cylinders down of oil. I evern put on a regulator so the fuel pressure did nto exceed 6 psi. At idle I am pulling 17-18" of vacuum and fairly stable idle. Yes, there is a slight oily film in the intake runners. Makes it hard to tell if I am sucking oil on one runner and it is getting sprayed back on intake strokes or pulling it via the PCV system, or blowing it past the rings and sucking it in????

Am I correct in the vacuum line to the cannister being full vacuum vs ported? Thanks.

I think I will try the box approach and steel wool in the PCV area.

 

Zwede,

I am now confused. Pulled 2 plugs on each bank and they were dark on the edge not oily and toasty brown in the tip and insulator. That tells me the mixture is just right if not a tad shade lean. No oil build up on the plugs.

OK what am I smoking if the plugs look like this or should I pull all of them and see if there is only 1 problem cylinder.

Also, should the "breather cap or oil filler cap be a sealed cap or a filtered breather cap? I am using a sealed cap.
Thanks

 

YiKes ! :eek:

Your tires are the only parts allowed to smoke. :jester

 

Yeah, you need to pull all the plugs to see if you have one or more problem cylinders. If all of them look fine it would certainly be weird...

 

If I was sucking small amounts of transmission fluid via the modulator and vacuum line to the manifold, would I produce smoke that resambles oil smoke??

 

I would check the compression to rule out the rings and valves,then systematically remove all possible oil sources.The PCV,vacuum from the distributer and transmission,whatever.I doubt the shortblock would be shot after so few miles,but an intake mismatch may seal for a bit,then leak.A lot of shops shave the heads every time they "rebuild" them,and though the surfaces are trued,the intake face angle is changed slightly.This could cause oil to be drawn into the intake ports from the lifter valley.

This is the rationalization I used to justifty the AFR195's to the boss.(wife) :yesnod:

 

Yes. ATF produces a lot of smoke, and the smoke resembles motor oil.

 

You did not mention if the engine smoked originally and that's why you "rebuilt it". An engine leak down gauge will isolate where the PSI maybe leaking too. If it's rings again you'll hear it leaking to the pan or out the oil cap. This also works great for verifing valve leakage. Compression testing is a quick/rough measurement compared to leak down testing.

Also which plugs did you remove? The vacuum modulator is basically plumbed into 4 cylinders with a dual plane intake(stock) It's very possible that the modulator has given up the ghost.

Look at what exactly what work the machineshop performed. Most will resurface all mating gasket flanges, and this can magify a problem. Fel-Pro sells an intake angle gauge #2525 for your big block. The reason your problem doesn't change with intakes swaps, it could really be with the heads!
If the angle is wrong you could be sucking oil from the intake valley. Do not use the stock rubber end strips. Instead run a bead of RTV in this location.

PC seals are more advanced than the OE o'rings that came stock. Short of some miscalculation with valve spring clearance and installation, these should not be your problem.

Look at the engine as a whole, custom V/C's and Air Cleaners may not allow the proper routing of the PCV system. Think of it as a loop, often a closed chrome V/C cap changes this simple system. I've seen many oil leaks caused by this.

Good Luck!

 

I pulled 4,6 and 1,3 plugs and they looked normal.

The valve covers that were stock on the 73-454 had a rubber cap in the passenger side and venting tothe air cleaner via a filter. Even though I have aftermarket covers and air cleaner that setup is duplicated.

I will run a leakdown test in the next week or so and see what I find.

According to the machine shop that did the heads they did not take off took much from the block side to make a difference. Maybe not.
At this point all bets are off and lets go digging.

Thanks for the input.