steveelsbury

Hi guys,

Having just got rid of my dud MSD unit and fitted a Crane replacement, and also finally got the tune dialled in, I've been playing with a little red-line, WOT driving in prep for some track time. I'm having 2 problems, which I believe are connected:

1. If I go on boost, the oil caps blow off the rocker covers

2. Big oil consumption

My immediate reaction is one or more broken rings, allowing oil into the combustion chambers, and also allowing blow-by, and I've bought a compression tester so I can check this out. I thought I'd post here as well, in case anyone had any other suggestions for diagnostics.

More info:

It's possible the crankcase pressure is caused by a bad check-valve in the PCV system, allowing boost pressure to reach the crankcase. Again, an easy thing for me to test and rule out.

On the oil-burning front, I get through a litre every few hundred miles. Whenever I go WOT I leave a puff of white smoke behind, but during normal running there is not excessive smoke from the exhaust and the engine does not smell like it is burning oil. Also, the rear bumper is not getting excessively oily - so where is that oil going? Clearly, I've checked that there are no discernible oil leaks.

I have noticed that with an oil cap removed and the engine idling, there is a stream of whitish mist issuing from the rocker cover, pulsing to match revs - again this implies that there is a problem with a single pot. I cannot believe the volume of oil that can come out of an open rocker suspended in that mist in such a short time!

Finally, my oil pump generates about 65psi, and I have no restriction in the blower oil feed. Last time I had the air filter off, I noticed oil dripping from the end of the blower shaft. So either I have a bad oil seal in the blower, or I am putting too much oil pressure through it, thereby defeating the oil seal. This one could also explain the high oil consuption, as it would be sucked (or blown!) through the intake manifold with the engine running, but I can't see how it could possibly be connected to the crank overpressure problem.

Sorry this is so long, but having not long finished the engine I'm dismayed at the prospect of a teardown and want to be sure I cover all the possibilities.

Finally, with all the above going on, the car still goes like a scalded cat, and pulls like a train right up to the red line. I've stopped doing that though until I figure out what the problem is!

All advice and suggestions gratefully received.

TIA

Steve
(Gagging to get the Beast on the track!)

PS Engine spec is in sig., which of course is now hidden by default!
In brief, Bow-Tie block, destroked to 377. TPIS RAM, All forged internals, Vortech V1 blower pushing 12 psi (ha! never seen more then 8!), TPIS long-tubes, yada yada yada


[Modified by steveelsbury, 2:49 PM 5/7/2003]

lead foot 85 vet

steve I have a procharger on my 85 and NO pvc system at all........the procharger instructions said throw it away.........I have a breather in each hole, inclulling oil adding hole and it seems to work........your running the pvc system?


\ :cheers: :cheers: :cheers: :cheers:

1991Z07

Steve,
First, might I suggest you post this in the "Forced Induction/Nitrous" section for someone who would know a lot more about it than most of us here.

It looks like you have identified the most common issues it COULD be. I'd start at the easiest and work your way up the ladder.

If you are getting some blow-by past the S/C oil seal, then you'll see oil in the intake track.

If possible, you may want to disconnect the S/C and let it run NA for a bit and see if you get the same symptoms.

Valve seals are another place to look for leakage. I don't think that is where your problem is, but it is another consideration.

Hope you find out soon what it is and get it fixed. I know the frustration you feel.

SPD DMN

Sounds to me like it is going right through the PCV system and out the exhaust. I have a litle consumption from this at high rpm but add a blower to the mix and you will have tons. Best option, disable the PCV and get an electric vacuum pump to evacuate the excessive crankcase pressure.

If it is going through the PCV and blowing out the breathers, you may have a blown ring or two though. Seems quite excessive.

SloRvette

To get an idea on the PCV system, check to see how much smoke you get right after you let off the throttle after a hard pull. The manifold vacuum at that point will be the highest the system will see and any oil pushed into the line will get burnt. Personally, on my forced induction car, I've got Chrysler breathers in each valve cover with hoses running from each of them to a common "puke tank" with a breather on it. It keeps the mess down from having open type breathers on the valve covers dripping oil after they get saturated.

How do the plugs look ? You'll get a crusty grey build up from burning oil. Are all the plugs the same or do you have individual ones that are worse than the rest ?

I'd take the outlet pipe off the supercharger an look at how much oil is there. I know with turbos you need to put a restriction in the oil feedline if the feedline is too large, or this sort of problem can happen. I'd give the supercharger manufacturer a call and see what they've got to say about oil feed volume. For you dropping them an email would be a start.

With the luck you've had in the past I sure hope you don't have a ring problem already.


[Modified by SloRvette, 6:44 PM 5/7/2003]

steveelsbury

Thanks for the feedback guys.

I do not get any smoke when I back off after a hard run, only when I slam it in the first place. I'm annoyed I didn't think of the very simple check of looking in the inlet tract for oil traces - that's on this weekends diag list now.

I'll post in forced induction about the oil pressure to the blower, and I'll post back here when I find out WTF is going on!

If you guys open an oil cap with the engine at idle, what do you see? Mist? Spary? Nothing at all?

Thanks, Steve
(I guess if I never had to work on the car, it wouldn't be much of a hobby)

lead foot 85 vet

When I open my oil cap at idle with a cold engine I get nothing but on a hot engine I get a mist or blow by..but my engine has 120,000 on it. when I bought the car three years ago at 105,000 there was none, then supercharger and now blowby.......any supercharged engine new or old will have to deal with blow by at boost you just have to deal with it. but at idle of course your not boosting and its showing you the condition of your ring seal.

jburnett

What are your ring gaps?? It sounds to me that you're getting excessive blowby...Best thing to do is leak it.
-Jeb

steveelsbury

Yeah, sadly excessive blow-by is what I'm assuming, but I've got everything crossed it won't be that! Ring-gaps, I don't know as I didn't build the engine (but wish I had now!).

Seems there's a school of thought that a PCV system is more trouble then it's worth. Is evacuating the crankcase really necessary? One person recommended fitting an electic vacuum pump, but is there any harm is just making the rocker covers are vented? LeadFoot, I see from your earlier post that this is exactly what you've done - any probs? The less plumbing, the less there is to go wrong perhaps? I'm going to have to make up a leakdown kit, as Brit shops don't seem to sell them. I'm kinda hoping if it is a ring, it will be obvious from compression plus plug crud! Then again I'm kinda hoping it's not a ring, too!

I could cry just now, 'cause I don't have the spare time for a tear down, and the racing season is just starting up over here! Oh well, I'm sure I can find a spare weekend if I try hard enough!


Oh well, a recent emissions test indicated a possible manifold leak in the right bank anyway, so perhaps this is a good opportunity to fix that too.

Steve


[Modified by steveelsbury, 11:31 PM 5/8/2003]

jburnett

Any forced induction or nitrous fed motor requires specific end gaps. If your engine has gaps built for traditional n/a applications it is WAY too narrow if you're trying to run any kind of boost; most likely you have had the ring gaps butt (flutter) and some scoring or damage has taken place (not what you want to hear).

Regarding PCV I'm of the thought that they ARE worth having. The scavenging affect can be worthwhile than simply venting to atmosphere via a breather. You may also want to think about running a pan evac system...This is similar in function to PCV but better as it produces much more vacuum and aids in ring sealing. These are generally run from the valve covers to a special check valve in the collectors of the headers...I run them on my 850 hp Super Stocker and on my heavily nitrous fed 1990...

My best advice to you is to perform a leakdown test on your engine. That will tell you everything you need to know.
-Jeb
PS- The Pan Evac is analogus with a vacuum pump as well...Both operate on the same principal they just go about it in different ways.


[Modified by jburnett, 10:42 PM 5/8/2003]

steveelsbury

Thanks for that Jeb - I'm sure the ring gaps were fine, as the builder knew all along it was to be a blown motor. We discussed it at length to arrive at the right build to support that, plus possible gas in the future. Mind you, he did rip me off in other ways, so perhaps?......

I guess if the pcv system is not *causing* problems, then I'll leave it as it is!

jburnett

That's why I provide everyone I build a motor for with the build sheet... That way there's absolutely NO question whatsoever.

Leak it and let us know... Your PCV should NOT be causing that problem.
-Jeb

lead foot 85 vet

All right now I'm confused..........the pvc gets its vac from the manifold....when under boost the manifold is under pressure so the pvc isn't going to work ....right?..and if all your valve cover holes are blocked with pvc stuff your engine crankcase is not going to be vented. :crazy:


[Modified by lead foot 85 vet, 4:42 PM 5/8/2003]

jburnett

You're not pressurizing the block, though; PCV's have a one-way check valve... I do not advocate the use of two of them; only one.
-Jeb

lead foot 85 vet

I agree the pvc has a check valve but it's not going to work under boost so its just blocking the crankcase ventilation system. why keep it. :chevy

SloRvette

You only spend a small part of the time under boost. The majority of the time the PCV system is working. The problem that happens is that with a lot of blowby during normal operation you end up fouling the plugs and having carbon deposits on the tops of the pistons and oil built up in the intake that gets pulled into the cylinders at WOT. Taking the PCV out is a crutch for a poorly sealed motor.

I know Steve runs a FAST with a wideband. My biggest concern is the wideband O2 getting fouled from the oil thats getting burnt. That's also why I'd stay away from a header type evac system. The widebands don't really like oil and they really hate antifreeze.

So Steve, when you get some time to diagnois, see what kind of feeling you get about the root cause of the problem. Is the oil getting burnt because it's getting by the rings, or is the oil getting burnt because you've got blowby that's causing oil to get into the intake tract through the PCV system.

If it's the PCV, you can always crutch the motor by taking the PCV out and running breathers, and at least have some fun with the car for a while.

I did that for a couple of months last year with my 383. It's looking like too fine of a finish on the hone did my rings in.

steveelsbury

OK guys, go my hands a little dirty this weekend and discovered:

1. The whole intake tract is covered in oil.

2. After an extended idle, there was no discernible oil leak on the blower (remember my oil pump generates 65 psi at idle too).

3. All the plugs were badly oiled up, with a couple showing a huge build up of burnt on crud.

4. Compression test showed 190-210 psi for 7 of the 8 pots, but 140 on pot 2. The tests were done with all plugs out, but with TB blades closed (I forgot - gimme a break!)

Soooo - clearly there's a major problem with cylinder 2, but I can't tell if it's rings or valves without a teardown. All in all, I'm now of the opinion that blowby is pressurising the PCV and blowing oil through the return pipe to the air filter. This points to rings. Doesn't it?

Bottom line, the engine is going to have to be torn down for a complete inspection. The trick for me will be ensuring I can get all the parts I need before hand, as the UK is not the best place to get SBC parts!

I would assume that if I replace any rings, I might as well replace them all, yes? Relatively inexpensive, aren't they? So all I *should* need is gaskets for heads and inlet and exhaust manifolds, plus a set of rings. Anything else?

SloRvette - I appeciate the tip about 'crutching the motor', but having come this far I can't bring myself to drive around with a motor that isn't right. I'm consoling myself with the though that my most recent WOT runs felt like I had a Warp drive, so when the motors fixed, it should be like a TransWarp drive :yesnod: Buddy's transmission is working well too, although it took me a while to get used to an overdrive in 3rd, using the manual TC lock! She's running 2200 rpm at 80 on the freeway, so economy remains good.

Keep the good advice coming everyone,

Steve


[Modified by steveelsbury, 3:30 PM 5/12/2003]

1991Z07

Steve,

If you can find one, try a bore-scope in the suspect cylinder. It goes in through the spark plug hole, and has a light built into it. You MAY be able to see something in there before the tear-down.

It will at least give you some indication if there is anything wrong with a piston, and if there isn't anything noticeable, you might just get by with a gasket set, new rings and the labor.

Good luck...


[Modified by Joe90, 6:05 PM 5/12/2003]

ziggy57

Since it is blower motor, I would probably buy a piston too along with rings . I have seen it many times on blower motors. Hopefully that is not the case but since you mentioned difficulty in getting parts, just a thought on being prepared. I see your results from the compression test, but have you down a leak down yet?

Good luck and please post the results after you tear it down. :thumbs:

steveelsbury

Hi Joe

A bore-scope? Don't forget I'm in the UK, where the motor spares shops and garages stock the bare minimum parts and tools! I suppose I could go to the local proctologist and borrow an endoscope! Anyway, the heads have to come off this weekend, so it should all become clear then.

S


[Modified by steveelsbury, 2:59 PM 5/13/2003]