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wp442 06-11-2011 07:16 AM

Stress-relieving a block
Years ago when I first built my Olds 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 lifter valley slot vs. the as-cast block. (The flash-rust you see is what happens when a clean block sits outside overnight in a rain problem, it's trashed anyway.)

(click thumbnails to enlarge)

...and here's a comparison of the smoothed-out main web and oil pain rail 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?

oldschool hero 06-11-2011 08:50 AM

An old round track racers trick to get the oil back to the pan as quick as possiable I also do this and to top it off I paint all the cast surfaces with Glyptol.

ap72 06-11-2011 09:09 AM

I would do it ONLY if you have oil drain back issues.

68NovaSS 06-11-2011 11:50 AM

If I'm bored waiting for parts, I'll do it, but will make sure nothing's hanging out ready to flake off.

cobalt327 06-11-2011 12:14 PM

There's something to be said for cleaning up the drain backs and to remove anything that would cut you while handling/building the block. Other than that, IMO there's little to be actually gained for the amount of time that you can spend deburring/radiusing/polishing the internal surfaces of a block that is used in a street application.

327NUT 06-11-2011 01:05 PM

Being retired I have PLENTY of time to debur the block, I did the inside and outside on my 507" Cadillac block and heads. I'm sure there are area's on the inside of the block that may benefit a little from the procedure, eliminating stress risers etc.

Oil drain back is always a good idea, I drilled a 9/16" hole at the rear of the lifter galley and radiused it with the die grinder just because their isn't one, but me doing the outside is strictly for the OOOOH effect. Hey, if you have the time, tools and inclination ...why not?

1BAD80 06-11-2011 07:24 PM

While you have the grinder out maybe port match the water pump to the block it helps with flow

wp442 06-11-2011 10:07 PM

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)

================================================== ==================================

Since I do have another week to kill before I can get the block to the machine shop, I might spend a few minutes with the water and oil pump matching too.

Overdriv 06-11-2011 10:20 PM

Cleaning the casting flash out of the block is always a good idea. Instead of smoothing the cast surfaces, paint them with Glyptol. Glyptol not only make for a slicker surface for the oil to return, but also seals the casting so minute pieces of sand or metal won't shed. I is also good to epoxy screens in the drain back holes. If you break something in the valve train it won't end up in your oil pump, etc.

cobalt327 06-11-2011 11:58 PM

BTW, "stress relieving" is NOT what is being depicted. What IS being shown is the more or less routine opening of drain backs, deburring, etc. and has little or nothing to do w/stress or its relief, other than coincidentally.

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