All,

My 91 383 with 12k has started to run a little off. There is a lot of crankcase pressure, venting out of the pcv valve, breather on the other valve cover, and out the dipstick tube. Oil is dripping from the pcv and breather grommets.

All cylinders max out to 210psi except number 4, which is 100 psi. All other 7 cylinders hit 180 psi after 4 revs of the motor.

I am looking at either a blown head gasket which is pushing compression into the crankcase (blown up near the lifter area) or my compression ring is shot/broken/stuck and I have severe blow by.

What are my repair options? I need to do a leakdown test on cyl 4 first.

I am unable to pull piston 4 from the bottom of the motor right? They need to come out the top of the engine?

I have a super ram and I HATE TAKING IT APART...but if I have to, I'm praying that I will not have to pull the motor to fix any cylinder scoring. Heads were machined and block was decked before installation 12k miles ago. I do not feel that is a blown head gasket. I am thinking an injector leak which washed the cylinder down. I cannot tell if there is fuel in the oil. Coolant looks clean/fine/etc.

Background: Car was running better than ever just before the issue happened in late june. Full power, absolutely screamed. Two and a half years ago, the oil filter adapter cracked and spewed 6 quarts out on to the road. I caught the check gauges light right away, killed the motor, fixed it, and all is well. Back before that, my steel distributor gear shattered, leaving metal pieces everywhere. Multiple oil drains, and all was well, but I have noticed over the past 3 years that my oil pressure has been slowly declining from 30 psi to around 10 psi at idle, jumps right to 40 psi at 2000 rpms, and up to 80 at full throttle. I am assuming all of these events are somehow connected...

What are my options? I do not want to pay someone to fix it, but I really don't feel like spending hours and hours R & R this engine/trans/etc again on jack stands.

Thanks,

Mike

 

Pull the valve cover and look to see if the valve ajustment looks right and go from there.

 

No pistons come out the top. You have something serious going on low compression and high crankcase pressure. Then tossing in metal through lube system. How much is salvageable who knows. Until engine comes apart there is no way to know. Valve issue or head gasket could cause low compression but not blow by, so doubt a leakdown will tell anymore than it's broke. Bore scope would let you look for damage on piston head and cylinder wall. You could pull oil pan check a few bearings and look for scoring on cylinder walls from underneath. It's a bad situation. You could cut your loses figure on new engine or take it a part and hope its repairable. That works on DIY but paying labor it's lost money. If damaged to the point engine has to be replaced.

 

I ordered a bore scope. I'll check that out when it comes in and go from there.

What's the chance a ring is just stuck with gunk?

Thanks

 

Unlikely only one set of rings would stick. One piston to be damaged is more likely. Compression is less than 1/2 that is a huge percentage. The best case is a hole in piston, no cylinder wall damage with light scratches on crank. One piston with rings and a set of .001 or .002 under bearings.

 

Good idea with using a borescope. U might want to try a compression test on #4 w/a squirt of oil. If compression returns/increases that shows blowby from the rings. Another test would be to remove the rocker arms (or just back off the rocker nut) and pressurize the cylinder w/air then listen and locate source of leak by sound of air. Crankcase, lifter valley, intake, exhaust pipe?

As for blown head gasket usually shows coolant leaks or 2 adjacent cylinders have low compression. The gasket would have to tear a long distance to reach the lifter valley but maybe a head bolt hole could make a flow path.

 

I agree with cardoo try the oil in that cyl. first then pull rocker and pressure check. either way looks like motor has to come apart to find out for sure.

 

Forget the borescope and the oil in the cylinder. Ur problem is blow-by from #4. Pulling the right side head and oil pan is required. If the cylinder wall isn`t damaged you might get by with a new head and oil pan gasket plus piston and ring set for one cylinder. Check ur rod bearings. If the crank is damaged you surely don`t want to install an undersized bearing. It`ll need turned and a new set of oversized bearings because the crank will be undersized.

 

What are the chances my cylinder wall is fine? What the hell caused this? Fuel wash from a bad injector? I do want to get the scope and try to see the cylinder wall before I pull it apart. I can still move it/drive it/etc. I don't have a ton of room to work on it, and I MIGHT send it to a mechanic friend if the motor needs to be pulled. I don't want to tear it apart, have it immobile, then let it sit all winter.

Thanks for all of your help. It's too bad, it was running reallllly strong just before it went. All of the plugs looked consistent, etc. Fuel mileage was normal...just the oil pressure concern which is probably the root cause. I'll probably check out all crank bearings when its apart. Maybe replace them all. Hope for the best for the cam bearings.

I really wish it was the a drivers side cylinder which went. It would make my life a hell of a lot easier. Might also swap out the super ram at the same time cause I don't want to deal with it.

Thanks

 

Is this motor still under warranty?

 

Nope. It was a 383 short block which I installed everything else onto.

I am really hoping the motor does not come out.

 

What is it about the super ram that makes it such a pita? i've heard this a few times compared to the miniram which is supposedly less of a pita. the normal tpi is a pita. how much worse is the superram?

 

Depends. How do you want to assemble it? There are the instructions and there are 2 other ways to assemble it. The great PITA seems to be how to get the manifold screwed down. The outer perimeter bolts are ok. It is the inner ones that are rough

Modified Factory: assemble the outer ones, slot the inner ones so you can turn them with a screwdriver and tighten it with the 12 point wrench.

Lazy way: drill out the screw holes on the inside bolt holes. Put helicores in the runner so you can screw it from the top side down. IF YOU DO IT THIS WAY, USE RED LOCKTITE. That will stop the screws from coming loose.

I think the issue is that the Superram is old and gaskets might not be forthcoming so you might have to make your own once they are no longer available.

Also someone modified the HSR to fit under the hood. This means you don't have to put a hood scoop like I did. HOWEVER, that said, I have no idea how it will affect the air flow if you cut it down.

 

So...update

Pulled apart down to the passenger side block. Cylinder looks great. Head gasket wasn't leaking. The exhaust valve on cyl 4 was a tan color, unlike all other cylinders on that side which were a golden white color. I did not pull the drivers side head.

I stil, have to pull the oil pan. Then I'll pull the piston but it looks no different than the others but obv I can't see the sides of it.

Rest of the motor so far looks just as it should for a well tuned 383 with 12 on it. All cross hatch still visible, etc.

One thing I did notice on cyl 4 head was a clean spot on the 6 o clock part of the head. This to me means an injector was leaky and was dripping fuel. I'm thinking that's what caused a ring failure but I'll know more tomorrow.

What do you guys think??? Main bearings will tell me a lot and I can see what's in the pan. I'm praying for a rering and injector rebuild and run it.

I'm going to send all 8 injectors to fic and label each one so I know if cyl 4 inj was leaking. That'll tell me for sure. If it's not, well I have some more work to do.

Thanks all

Mike

 

Have you seen any leaking? IOW, when you hook up a gauge, do you see a pressure drop after the pump shuts off?

 

No, I haven't. I can't pressure test it now as its all apart. I guess I could mock it up on the intake and hook up the fuel lines. I'm sure it'll leak at fic if it's bad.

 

Mark it and send it. Sounds like a plan. In the meantime, what about the head? Is there something wrong with it or has it been checked out?

 

Here are a few pix. Heads look great. That lil line you see is a piece of grass lol. Heads were sent out and decked and valve job. before the rebuild.

Look at the intake valve. Look at the 6 o clock part of the head and piston. Looks really clean to me.

What do you all think???

 

What could cause this???

 

this is far beyond my ability but what am i evwn looking at insofaras the issue? the broken thicker ring?