Valley Pan pushed up

[Garys1969RR]

Our 496 stroker motor must have excessive crankcase pressure, as the valley pan has now blown upward against the bottom of the intake manifold. This occurred the last time we raced it. Is this due to blow by past the rings? Or poor venting from the valve covers? It never did this before, and we've raced it lots of times. It has the vac u pan set up, so I don't know what's going on. Will prob pull the motor out soon, and rebuild it over the winter. Has anyone else had this happen?

 

[zyzzyx]

Last time I had that happen was when the Nitrous solenoid opened, but the gas solenoid didn't!
Burned a hole in one piston and POOF! That's what I call Blowby! OOPS!

 

[Garys1969RR]

Hahaha, that's a lot of pressure down there! we had a 383 with nitrous blow up the valley pan too! Guess sometimes the rings just can't hold the high pressure on top of the piston. That's with a piston with no holes in it.

 

[63RedFury]

Need to vent the valve covers better..

 

[Cranky]

Better evac system needed or the rings are leaking more. A leak down test will probably show that. Had a small block that wasn't venting good enough and it blew oil out like crazy and it blew out the front and rear intake gaskets....

 

[zyzzyx]

Of course, if you are racing the car you could ad a dry sump system and you'll have
negative pressure in the crankcase, and tons of clearance underneath!

 

[Cranky]

Of course, if you are racing the car you could ad a dry sump system and you'll have
negative pressure in the crankcase, and tons of clearance underneath!

What kind of money are ya talkin bout?

 

[WP29440SE]

I had an ex girlfriend take my 440 out , lost oil pressure, melted the main bearings and subsequently blew the valley pan up against the intake , AND blew the sides of the valve covers out. that engine was never the same after that.

 

[zyzzyx]

I was just looking, and it depends who's brand you use, but you can put a system together for 2-3k
and never worry about running out of oil. There's alot more available now then there was years ago.
Petersen, Edelbrock, Moroso, etc.

 

[Bobzilla]

Check leak down as Cranky suggested. That will tell if the rings still have decent seal or may have caused this.
If the check valves down at the hedders have worn out, burnt up, or otherwise failed, they may allow exhaust pressure into the crankcase. That would be an easy fix.

 

[jason79]

When that happened to me I had lost 2 rod bearings

 

[moper]

You have a vacuum pump, and it popped the valley cover? You need to do a leakdown immediately. The pan bent from pressure, but with the vacuum pump you should have had a vacuum (negative pressure) to start with. You might have damage to a piston, not just normal wear. Especially if this was "fine one run" and then "not fine".

 

[zyzzyx]

I used to put a piston all the way down in a bore, and screw in an old spark plug bottom welded to a quick connect fitting and pull a valve cover. When you hook an air line up directly from your compressor, going from cylinder to cylinder will give you an idea of how bad
the damage is. Just make sure both valves are closed when you're pressurizing each cylinder. WoW! that pic of the valley cover looks just like mine did!

 

[Garys1969RR]

Don't I want the piston at TDC when checking leak down? And how much is too much? 5% or more too much?

 

[zyzzyx]

Yes, to do a true leakdown test, but I think you have something, uh, a little more!

 

[Garys1969RR]

The car ran the same ET as before the valley pan blew, low 11s. I do think the rings are worn, or maybe it has too much piston to wall clearance. I'll do a leakdown test next Saturday. There is alot of piston slap noise when I have the mufflers on there, I can hear it.

 

[dvw]

How much timing? Compression/cam timing? Fuel type? It may be in detonation unseating the rings. Assuming it has a factory style breather. Something would have to messed up to flow that much volume out of the crankcase. Broken ring land?
Doug

 

[moper]

A 496 B, or 496 RB? The B uses a really short piston. So they can be noisy and I'd expect the rings to wear much faster due to the piston rock at TDC. Acceptable leakage depends on the rings and wall finish. Standard gap-type rings I'd say anything less than 8% is ok. Gapless less than 3%. Leakdown should be tested at TDC.

 

[Garys1969RR]

Running 38 degrees advance. It's been running fine the past 2 years, with no valley pan issues. Using 100 octane LL fuel. Roller cam about .640 lift. 383 block, so B deck height, short piston skirt. Not sure what rods are in there, although the previous owner claimed it was a 14 to 1 C Ratio motor. I dont think so. Stealth heads. Roller rockers. It has a vac u pan venting system. No PCV. It has been pushing oil out around the oil pump mounting gasket.

 

[Garys1969RR]

Also, we just went to a tunnel ram with 2 500 CFM Carter carbs. The car actually ran about .2 sec slower with THIS set up. Plugs have a nice tan color. It ran faster with the M 1 intake and an 1150 CFM Dominator carb, although that carb seemed to be running a little rich. Sat I will be switching to a couple of 750 Holley dbl pumpers that Cranky used to have on a ten second RR. So well see how well that arrangement works. Our carb airflow will then be 1500 CFM. Its at 1000 CFM now with the Carters. Maybe the Tunnel Ram and the Carters caused this. It happened on the 2nd or 3rd run after installing it.