Need Help On Excessive Crankcase Pressure

[1969 beep beep]

Sixer, I checked the breather hose and did not find any oil. A very small amount of oil misting on the inside, could barely tell.
Is .007th okay or is it to tight on end play? Factory was .023th.

 

[daredevil]

I have a 4.15 stroke rb with indy ezs and flattops 0 decked. Mine blew oil out everytime I jumped on it when it was new. Dipstick, valve covers, valve cover caps, vents. Finally I added a breather to the oil fill and two pcv,s one in each valve cover to a tee in the back of my carb spacer. Just a little gets out the vent sometimes now. I have bungs on the headers so i,m gonna add a couple pan evac lines also to take care of the red line blips. I got it chipped at 7 k.Mines been in the car over a year but only has a couple hundred miles on it.I fight the same issue of blowby at high rpm but it usually came from the vent or dipstick/ I run a comp billet distributor though.

 

[1969 beep beep]

Okay I tested the car with disconnecting the 5/8 tube off the air cleaner and left it in open air, installed a new pcv and the first time I did a wot run oil was present again below the distributor. I cleaned up everything and removed the pcv and installed a breather with a 5/8 tube connected and routed it under the car. The other breather was connected to the air cleaner. I tested the car again and still found oil but not as much as with the pcv system. It is definitely coming from the distributor. I removed the distributor cap and found oil in the bottom of the distributor base. I checked distributor shaft play with the distributor installed. If I move it back and forth with my hand it has .020th shaft play. If I use a short bar and move the shaft, it has .050th shaft play. Not sure if this is to much play. Should I try a complete open breather or will it make no difference? I am out of ideas. It I definitely excessive crankcase pressure that is causing this.

 

[snakeoil24]

You can also put5 a felt washer under theplate inside distributor. This will soak the oil up. It will still drip but it will reduce contamination of the electronics in the distributor. Also dud you check the bearing in thedistributor to see if it is worn or extra out of round.

 

[dryheat]

I originally took apart the distributor and it had a teaspoon of oil in it.

I'm certainly no expert but that has never stopped me from posting my thoughts before !

Given the fact that you obviously have oil inside the distributor housing there are only two ways for it to get there ... it's either being pushed in from the bottom or pulled in from the top.

I have not taken my distributor apart but there is a spiral cut in the lower shaft that could act like a pump and push oil inside of the housing.

Does your distributor have a vacuum advance? Is it possible that it is broken and causing suction inside the distributor and pulling in oil? Perhaps using the wrong vacuum port off the carb?

 

[1969 beep beep]

dryheat, I am running no vacuum advance but good point. I took apart the distributor and found oil inside and decide to add a larger shim diameter. I think the oil is forcing it's way up the oil port in the bottom of the distributor and working it's way up threw the bushing. Should I add some felt to the oil ports, and a larger diameter shim to cover the ports?

 

[69Bee]

This might be a silly question because I have never seen oil come out of the disributor. Oil must be under pressure to be violently thrown at the bottom of the dist. The only place there is pressurized oil close to the dist is the pipe plug blocking the end of the lifter rail. It might be possible to be loose enough to squirt oil under hard acceleration, or might be missing altogether. I have a hard time believing that non-pressurized oil can get past two bushings with enough volume to flood the dist and leak, just a thought.

 

[1969 beep beep]

69Bee, I agree with you. I cannot understand it either. Is this the plug you are referring to.

 

[RustyRatRod]

.020 or .050 shaft slop is too much, IMO. We're talkin about a bronze bushing here. There's shouldn't be much clearance at all. I can only imagine what changes that is making to the dwell.

 

[1969 beep beep]

Were can I purchase new bushings?

 

[daredevil]

Were can I purchase new bushings?

possibly auto electric shop

 

[RustyRatRod]

Were can I purchase new bushings?

It might not be necessary. A good machine shop should be able to burnish and ream them to the proper size. Very similar to knurling a valve guide.....but with bronze bushings it actually lasts a long time.


Before you run out in a distributor crisis, see what some of the other members think. It's just my opinion that the clearance you mention is too much. I could be flat out wrong. It has happened before. lol

 

[daredevil]

.050 sounds huge.

 

[69Bee]

I was and wasn't talking about that plug. On the RB, there should be an inner plug on the lifter rail, but not the B I guess. I just verified on a 400 I have in here. The excessive clearances could contribute to the problem, and can be fixed by most any machine shop. They just ream out the old bushings, install new oilite bushing stock, and hone to size. I would expect to see something along the line of 0.002" to 0.005" since my 69 manual says to rebush if over 0.006".

 

[1969 beep beep]

69Bee, the block I used is a 400. I removed the lower bearing last night, and will have to get a new one machined. It is a weird OD. The inner is a standard .500, I pulled it because it was not 100% round. After using a telescope gauge I measured .050 on the top bushing, and .051 on the bottom bushing. The top measurement was the same in all positions on the bushing. The lower was not the same in all positions. Some were .050, .051 and .052. The distributor shaft was .047 on the top and bottom.

 

[69Bee]

I am not following your measurments. You start out by saying the id std is 0.500", but then go to 0.050" to 0.052", and the shaft is 0.047". Are you saying the bushing measures between 0.500" to 0.520" and the shaft is 0.470"? If so, the clearance is approx 0.030" to 0.050", and too much.

 

[RustyRatRod]

I was and wasn't talking about that plug. On the RB, there should be an inner plug on the lifter rail, but not the B I guess. I just verified on a 400 I have in here. The excessive clearances could contribute to the problem, and can be fixed by most any machine shop. They just ream out the old bushings, install new oilite bushing stock, and hone to size. I would expect to see something along the line of 0.002" to 0.005" since my 69 manual says to rebush if over 0.006".

Finally, a spec! Thanks for that. Sounds about right, too.

 

[1969 beep beep]

Sorry 69Bee, I made a mistake. I remeasured it. The distributor shaft is .497 and I meant to say .500 for the top bushing all around. For the lower bushing it was ,.500, .501, and .502.
The lower was out of round. Still within spec. Sorry if I confused anybody.

 

[1969 beep beep]

Here are my results. I replaced the lower distributor bearing and installed a fitting on the distributor base drain hole so I could hook up a small vac hose to route the oil some were else. This would show exactly were the oil was coming from. I now have a diameter of .499 on the top and bottom bearing, and the distributor shaft is .497. A difference of .002th. I added a larger diameter shim on the bottom of the distributor to cover the 5 oil holes and set the end play to .007th. I tried about 10 wot hits and sure enough oil is back in the distributor. It probably blew out 1 tablespoon. There are no signs of oil around the distributor base, heads or valley pan corner. So I thought maybe the 4.15 crank I used was throwing the oil up into the distributor oil holes, and by blocking the distributor oil holes that did nothing. Trying to set the end play on the distributor from .023 to .007 thou also did noting. I drained the oil today and thought maybe it was over filled. I removed almost 6 quarts. I am using a 440 source hemi oil pan with a 440 source stroker windage tray. I am also using a Melling high pressure and standard volume pump. Could any of these items be affecting this. Maybe the oil is not draining back quick enough on wot due to the windage tray. Is there away to check the crankcase pressure under wot? This has to to be from oil pressure pushing the oil between that .007th gap, or is it from the top of the engine being flooded with oil? Maybe the pan is to small? Any ideas?

 

[70rr-brian]

Do a leakdown test.

http://www.carcraft.com/techarticles/116_0406_cylinder_leakdown_tester/viewall.html