Just completly rebuilt a 1978 Ford 460 motor and am trying to dial in a few things. A few particulars. This is an F250 used for towing. D3VE Heads w/ smog bumps ground out, stock valve train. Hyper-U pistons up'd to aprox 9 to 1. RV cam (Speed Pro 204/214 dur-.484/.510 lift-112 speration). Eldebrock perf. manifold & perf. 650 carb, headers 2x exhaust, 3 1/2" K&N. Still has the Dura-Spark II but w/new wires & aftermarket coil.

1) Rear main seal seems to be leaking! Haven't dye tested yet but pretty sure it's not the pan gasket. Yes I did rotate the 2 piece Felpro seal off center about 1/8 turn as most suggest. Had this stinking problem before the rebulid too. Could it be from excessive pressure? I replaced the stock valve covers with aftermarkets. They have a "breather" cap set up as opposed to the stock breather with the return line to bottome of the air cleaner. PCV valve is new. Crank was re-ground .10 so don't think that would be a problem. One of the main reasons for the rebuild was to finally fix the stinking leaks! I've done the rear main seal sawp before and would be willing to go through that big pain in the butt again if I knew it would fix it.

2) Timing suggestions: I have been playing around with this and currently have it @ 11 BTDC. At stock setting of 12 BTDC I was experencing some pre ignition under a load and run-on after shut down. Even tried down as far as 8 BTDC. Seemed to run pretty poor down there.
Thanks for any input...

 

My '76 460's rear seal leaked before I rebuilt it, but not afterwards. The only thing I did differently than you was to put a super thin dab of RTV sealer/adhesive on the ends of the seal halves. No leaks after that.

 

A couple of times that I had to deal with rearmain seal leaking, it was caused by bad PVC valve and there was to much pressure in the oilpan cause'n it to blow the oil out the seal. Some pressure is caused by bad rings and the compression slips rightdown into the pan and no matter how good the seal was,it would leak.Also the vacuum from the intake could be bad, or the rubber hose do plug up.

 

Did you install the "lip" of the seal towards the front of the engine? It will leak if installed backwards.
As 76Econoline stated: you also need to put the RTV sealer on both ends of the seal-halves. I also put a lite coat of RTV sealer on all mating surfaces of the oil pan.
Deen

 

I'm doing a rea mian this weekend in my Bronco. I'll let you know exactly what I did and if it stoped it from leaking or not. Oh yeah I use Roll Gaskets if that matters any.

 

Mine didn't leak before, or after my rebuild............

 

i have had rear main's leak in the past but this was on either 302's or 351w's,and i was able to pull the pan and rear main cap,and carfully slide both end's out,and slide the new seal in,and oil leak was gone.My question is can I do the same on my very 1st 460?The seal look's like the same type as my other's I just was wondering if it will be the same process with the 460?

 

that's what I did to my rear main seal last weekend. Pulled the pan took off the rear cap and loosened the other ones to help get the top half of the seal out. Mine was stuck in there and took some doing to get it out but it worked.

 

that is what I wanted to hear!i have to change the pan anyway's so this will work out cool!Im not even sure if the rear main is the leak but if I have the pan off I should do the seal too! I would hate to do the pan job twice!

 

I have seen this before and if replacing the seal and the pvc vale doesn't fix it then main journals are not ground concentric to the seal surface. If the crank has been reground then the Machine shop screwed up. If OEM shaft then Ford blew it. Like I said Ihave seen this before. And until the crank was ground right nothing would keep the seals from leaking.

 

My rear main leaks only when vac drops below 4 inches. This is a fresh motor (12,000 miles) and leaks badly when towing heavy. When the vac drops. oil leaks onto crosspipe and the %&$&* thing looks like it's on fire.....PCV is hooke dup and seems to work fine Any Ideas?

 

Probably should have went with a rope seal.

 

yes they all leak