OLDSmobility

Years ago when I first built my 455, I was told that it was cheap insurance to spend some time deburring the block...removing casting flash (like just above the cam in the lifter valley) and radiusing the sharp edges around the main webs and oil pan rail, as a way of stress-relieving the block to prevent possible cracks. I spent an evening with the die-grinder and completely smoothed everything off.

Now I'm ready to rebuild another 455, a street/strip project around 450HP. This block is stripped down and will be headed off to the machine shop within the next week or so. However, if I'm going to repeat the deburring process on this block, now's the time to do it, before it gets cleaned.

So...what is the general concensus regarding spending time removing block casting flash and sharp edges. Is this something that SHOULD be done, or is it just internal eye-candy?

Here's a comparison of the smoothed-out main web and oil pain rail vs. the as-cast block. (The flash-rust you see is what happens when a clean block sits outside overnight in a rain storm...no problem, it's trashed anyway.)

(click thumbnails to enlarge)



...and here's a comparison of the smoothed-out lifter valley slot vs. the as-cast block.



So what do you think? I know it's not going to hurt, but is it beneficial to any degree?

442garage

Keith,

I'm sure there are many differences of opinions on this, but I will weigh in on the side of thinking that it is beneficial to remove the casting flash and deburring the lifter valley to aid in oil return. A combination of esthetics and function. I seem to remember reading in Joe Mondello's tech book that these were recommended. At the least, I see no harm that it could do.

don71

If you can help the oil drain back, this could only be a good thing. I don't think polishing it like a jewel would yeild that much gain. Concentrate on the oil drain back areas.

I wouldn't waste much time unless you have a known good block.

joe_padavano

What he said.

I routinely deburr the insides of the block to facilitate oil drainback.

OLDSmobility

Well, I decided to forego the shaping of the main web and pan rails, but I did spend a little time smoothing out the rough casting flash in the lifter valley and enlarging the front oil drainback hole. The bottom of that hole got dropped a good 1/2", so that should definitely help with drainback.

(click thumbnails to enlarge)

BEFORE:

AFTER:

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BEFORE:

AFTER:

don71

Since you got this far..and its looking good, why not check out where the oil pump bolts to the last main journal. You might be able to detail that area as well. You'll see what I mean when you get there, its like port matching the intake...

rustyroger

Deburring the block won't make much difference in oil draining efficiency, the clue is in the title - stress relieving.
The reason behind it is simple, any area of casting that varies in thickness is a weak point where cracks can develop, smoothing off casting flash addresses that problem, rounding off square edges does the same thing (think of the edge as a peak).
The American way of making a big lazy motor meant casting flash removal etc was not really neccesary on the understressed lazy v8s that were the norm in the era of cheap gas.
Don't take my word for it, ask a metallurgist or foundry engineer!.
Roger.