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Senior Member
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Discussion Starter · #1 ·
I have changed my oil pan gasket twice now and the persistent leak near the rear is still there. I suspect that it is the rear main seal. I have read many posts that suggest that too much crankcase pressure or a bad pcv may cause this. with my motor and 9 quart canton oil pan, the oil pressure is about 55 - 60 lbs while cruising around 65 mph on the highway and around 40 lbs at idle. Is this too high? What would be considered normal pressure for a motor like mine?

Also, the pcv i got is for a small block Mustang. Is that valve good enough?

Thanks for the help.
Curtis
 

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Your oil pressure sounds perfect, Getting the seal at the rear is tough. Are you using silicone at the corners and being very careful not to let the gasket slip?

There is no oil pressure at the rear seal, but could be crankcase pressure. Your pcv valve should work. How are you venting the other valve cover?
 

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Also, there is a steel wool mesh filter under the PCV valve. Be sure that is clean. You can buy a replacement for a couple bucks in any auto parts store.
 

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Discussion Starter · #4 ·
Thanks guys.

Hey Mark. I actually paid a reputable mechanic to change the gasket. (I know I'm a wimp.) The second time, he did it for free. I really didn't want to get under the car and on my back to change it. He explained to me that he would put silicon in the corners. Besides, he told me he has changed the gasket on he race cars, so I was comfortable. Also, I am venting the other side with a breather cap.

USMC, I may just do that and change the pcv, cheap insurance.

[ March 14, 2007, 02:55 PM: Message edited by: Curtis ]
 

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FFCobra Craftsman
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And if for nothing else than an experiment ditch the pvc and just vent to a can.
 

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Pull the dipstick out, and attach a long rubber hose. Duct tape a catch can to something, and point the tubing into the open can.

That should vent the crank case pretty well. If it stops your leak, you need a better venting system. Like this one from GZ Motorsports:


 

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FFCobra Fanatic
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The way you have your pvc valve set up should be fine. Pcv valve on one side,vented cap on other. Keep in mind you have a stroked motor. Strokers take up more room inside the crak case and can benifit from additional venting mentioned and even going with a larger pcv valve. Look in the parts store for a pcv valve used on big block fords. May help some also.
Since this will be 3rd time for pan gasket replacement might want to use some dye to check exsactly where oil is comming from. It may be seal or may be pan but dye will help in finding point of leak. Won't be the first time leaking valve cover has led to pan gasket replacement.
 

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Discussion Starter · #9 ·
Thanks guys! I'll look for a larger pcv first
 

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Curtis,

Are you sure you are not leaking from your rear main? What year is your block? 1-piece or 2-piece main? I have a persistent leak in the same area. At first I thought it was the pan. After digging deeper it turned out to be the rear main. I have a '77 block with a 2-piece main, and after changing it 3, YES THREE :mad: times I have reduced the leak to an occasion drip, but I have not been able to eliminate it completely. Correct me if I'm wrong, but I think a lot of guys with the 2-piece rear mains on a 351W block have leak problems.
 

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Curtis, I had the exact same problem at the back of my 393W, but before pulling it out to redo the rear main seal, I dropped the oil pan and used a one-piece Fel-Pro oil pan gasket. MAKE SURE TO SQUIRT GASKET SEAL IN THE CORNERS WHERE IT STARTS TO GO AROUND THE CRANKSHAFT. You will seel the two little dips (about 1/4" deep). Fill them with gasket seal completely, then put the gasket on and tighten it up. I neglected to do this on my motor I was repairing this winter and had thae same nagging drip in the rear of the engine. The one-piece gasket is about $40, but well worth it. The real kicker is the $1.99 worth of gasket seal I didn't use the first time that cost me an additional $40 for another gasket and $100,000 in frustration and cursing.
 

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Discussion Starter · #12 ·
Chris,I checked with Keith Craft and confirmed that I have a 1974 block with a 2-piece rear main seal.

Robert, the first time I had the gasket changed, it was with the Fel-Pro. The second time, it was with the 4-piece as recommended by Canton.

At last check, I loose about a 1/4 of a quart every 550 miles.

I'll get some of that dye this weekend just to make sure it is not leaking from somewhere else. I'm pretty sure it's not the valve covers, but hey...let's cross it off the list anyway.
 

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Old thread I know. But figured I'd pass this tip along(on removing the PCV wire screen , At the bottom of the PCV valve).
Small - long needle nose pliers worked perfect ,on removal of the screen.It did not damage it at all. :smile2:
 

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Since this thread has been brought up, I'd like to ask a question.

I am running the Fitech unit on a Edelbrock RPM Performer. I don't really know about pcv valves, but I've read that they relieve the crankcase pressure. there is a 3/8" vacuum port that comes out of the fitech to go to a pcv.

For those of you that have the rpm performer intake, where have you put your pcv valve?
 

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FFCobra Craftsman
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The PCV valve is usually in the valve cover and it's hose runs to that 3/8 nipple on the FiTech throttle body. Same as it would on a typical 4bbl carb. Be sure one of your VCs has a cap w/ screen in it so the PCV has some place to suck the air from.
 

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The PCV valve is usually in the valve cover and it's hose runs to that 3/8 nipple on the FiTech throttle body. Same as it would on a typical 4bbl carb. Be sure one of your VCs has a cap w/ screen in it so the PCV has some place to suck the air from.
My DS valve cover has a 3/8 stub coming out just below the cap on the fill neck. But that's all. Should pcv be installed?

I do have a available port on the PS that I can do something with.

 

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That stub is used to go to the air filter base for filtered air into the engine. The other valve cover gets the PCV. Conversely you could put an inline PCV in the stub to the PCV port on the bottom of the carb and a breather in the passenger valve cover. Keep in mind that there is usually a baffle under the PCV so you don't suck a lot of oil.
 
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