anti depression valve

[kmac]

What does the anti depression valve do? I just installed a banks turbo on my '86 M1009 / K5. The hose with the kit did not fit so I unbolted the ADV and connectected it hanging free. I now have a huge amount of oil coming out of the back of the engine and horrible performance. Can moving the ADV and having it hang on its side cause either of these?

 

[Russell]

That canister is used to draw crankcase fumes out of the engine and put them back into the intake stream to burn them. My 6.2L used to draw air from the oil filter housing and deposited it into the intake. The new 6.5L turbo setup I am installing has the canister draw air from the passenger side valve cover and used to deposit it into the intake ducting before the turbo. I am planning on drilling a hole in the intake and putting a nipple on it to deposit it into the intake rather than in before the turbo since I will be installing a open element cone filter right off the turbo to start.

There shouldn't be a large amount of oil coming out of it, so I would personally be checking my turbo oil supply and return lines for leaks. As far as the performance goes, did you turn up the injection pump? Is your lift pump operating properly?

 

[kmac]

The oil is not coming from a line, it is coming from the inspection cover, I was wondering if a faulty valve could cause to much pressure to force oil out around the rear main. There are only 45K on the engine. Also turned up the IP 1/4 turn, lift pump was new last summer, fuel filter new in November- less than 2,000 mi.

 

[Russell]

Having the canister not working properly can cause some gaskets to sweat, but the crankcase pressure shouldn't be bad enough to cause oil to pour out of a seal. My guess is that your rear main seal has failed, which means you'll need to drop the pan and the rear most main to replace the seal.

Does your engine have a lot of blowby? If it does, coupled with the turbocharger, you could be loosing a lot of your potential power...

Did you take the injection pump off at any point? Are all the cylinders firing properly (aka, no air in the lines?)

 

[kmac]

No blowby that I know of. Engine was very strong before install. Still fires up and runs great. Only getting 2-1/2 to 3 lbs a boost. I have driven 30-40 miles I don't think there is any air. Power increases to 1/2 throttle after that it is just flat. Took the cover off the IP to turn up but I did not remove the pump. Is there anything under the cover that could get hung up putting it back together that could cause this?

 

[Russell]

Not that I am aware of... Do you have a pyrometer installed on the engine?

When you romp on the skinny pedal, do you get any smoke out of the exhaust? If not, you may need to turn the fuel up a touch more. You should be achieve 5 - 6 PSI of boost...

 

[kmac]

I do have a pyrometer 600 degrees max. No smoke. I thought boost is supposed to be 8-10?

 

[Russell]

Sounds a bit cold to me. I'd be turning my pump up a bit more personally. My understanding is that you want to have the temps around 800 sustained, and no hotter than 1100 with un-coated pistons while under load.

Boost is largely dependant on exhaust temperature, so if you are running the engine fairly lean, you won't make much boost. The more fuel you put into the engine, the hotter it will run. On a stock 6.2L, I'd stick around 7 PSI of boost to be on the safe side. It isn't so much that the engine can't handle more pressure, but more that without an intercooler of some type, your exhaust temperatures will get too high.

Again, turn your pump up a bit and keep an eye on both the pyrometer and the boost meter, you want to adjust the fuel until you are getting good temperature and good boost, but not so hot that you start melting pistons. When you get it tuned right, you should have a bit of black smoke when you put the hammer down, but it should clear up as soon as you start making boost. To test your temps, find a long grade to crawl up, or otherwise labour the engine and make sure the temps don't get too high.