Thread: 496 Rebuild Or Replace?

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Hi. I'm back after a several year absence. Some background.....I have a chopped, twice "Z-ed" and slammed '40 Chevy 2 door sedan. Tilted B pillars and back glass. Power is provided by a 496" BBC. It has (8 stack) Hilborn electronic fuel injection that works extremely well. Comp Cams roller cam, Scat crank, Eagle rods, and Edelbrock aluminum heads. It's been dynoed at 450 to 500 HP at the rear wheels. I'm running a beefed up 700R4 with a Ford 9" rear end, 3:70 posi and Curry axles. The engine and trans work pretty much flawlessly. It's a really awesome looking and running show car that's also a driver.

OK, let's narrow this down a little.....in my shop I noticed a VERY slow leak in the area of the rear main seal. Soooooooo, if it is a main seal am I looking at a major procedure? If so, should I consider a rebuild or a replacement? There are currently so many really nice, very powerful, pump gas, crate engines being offered. So, assuming the car needs a rebuild or replacement which way would you lean? Rebuild or replace?

BTW, my mechanical knowledge runs pretty shallow and is very basic but I have a lot of knowledgeable buddies. If I replace the engine I would want to keep the Hilborn electronic fuel injection if at all possible and install it on the new engine.

So, rebuild or replace? What would be your choice be and why?

drive it. they all leak sooner or later . make sure your crankcase is well ventilated . oil leaks are from crankcase pressure 9 times out of 10 . i use moon breathers .

I wouldn't worry about it either. Unless it's leaving a puddle of any type.. it's just marking a spot otherwise.
If it bugs you, replace the seal and run it some more. A damp seal doesn't warrant an overhaul, unless you just want to spend money!

Originally Posted by 34_40

I wouldn't worry about it either. Unless it's leaving a puddle of any type.. it's just marking a spot otherwise.
If it bugs you, replace the seal and run it some more. A damp seal doesn't warrant an overhaul, unless you just want to spend money!

DITTO. Mike/34_40 is spot on!

Drives me crazy but all the older engines drip, the rear main is always a problem. My small block chevys always leaked. My ford 5.0 I was so careful building that motor because I didn't want any leaks - it leaks everywhere! A new LS crate motor would be cleaner I'm sure.

Thanks guys. The leak is barely even a leak. Maybe a drop a year? Or less? It's an awesome engine. Drive it I will.

Originally Posted by bgblk40

Thanks guys. The leak is barely even a leak. Maybe a drop a year? Or less? It's an awesome engine. Drive it I will.

Wow - a drop a year?? I thought you were talking a lot more that. Get one of the cookie sheet type drip pans and call it good.

i have scored really nice motors in the past that somebody thought was toast. i bought a 60's era 427 out of a vette . not the big hp motor so calm down . i put it on a stand and checked compression . good all 8 holes . the guy couldn't tune so it was running really fat . smoked a lot . likely washed down the cylinders . i put ti back together with new gaskets and seals. put a good tune in it and was good to go. within a few hundred miles the cylinders cleaned up and seated .
a pcv valve wont do diddly on a fat motor pumping up the crankcase . i use the moon breathers on every build and my motors dont leak for a good while .