Question for the machinists here....

[cutting torch]

I am wondering three things......

1) How thin can the bores of an LA block be for a build that could be used up to about 600 horse? (Major and minor thrust areas, and front and rear of the bores.)

2) If it is thinner than desired, how much help would block filler be?

3) How badly does block filler distort the block as it cures, assuming main caps and heads are installed and torqued for the cure time?

Thanks for any input.

torch

[Madman Stephan]

I always thought a trick was to bore out the cylinders until the walls are paper thin and then to sleeve them. I think you could get up to .090 overbore that way.

[perfmachst]

hello, boring out to .060 over would be my limit. however, block grout will support the walls and will not flex or grow when running. using block filler will usually not distort bores. use the Hard Block grout. important, have mains torqued on before grouting block, right after pouring in grout, torque on deck plate with gasket. let it sit for at least two days to cure completly. then roll block to other side, repeat steps. after all this, then you can bore and hone block with deck plate. now the bores will stay round. this filling of a block is for drag race blocks only. fill to bottom of water pump outlets in block.
just food for thought.

[Rust collector]

If I understand the question, I think he is asking about wall thickness, not some generalized overbore size "rules"???

[cutting torch]

Rust, you are correct, and Perf, here is more info to go on:

I have the chance to get a Kieth Black block (LA) that is a real nice piece, but it has a thin area in the #5 bore, half way down, at 3 o'clock, that is .079 thick. The major and minor thrust areas are in the .200 to .300 range. My thought was to fill it to the bottom of the freeze plugs to shorten the unsupported length of the cylinder walls, but not lose too much water jacket.

The bore is at 4.100 now, and I was wondering if the filler would distort the block as it cures, requiring a lot of hone to true it up. (It's an iron block.)

torch

[perfmachst]

hello, on your bores, first measure bore with dial bore gauge. see how out of round it might be. If out of round, torque main caps on, let it set about 12 hrs, then remeasure. If still out, install deck plate or cylinder head, you want to make sure bore is round before grouting. If they are round,with out any bolts torqued, then grout it. prep requires ,soft plugs installed, clean water jacket with muratic acid, radiator shops use it.flush with clean water, blow dry, heat dry, water jacket. the instructions in block filler will tell you how to prep.I use the Hard Block brand of filler. grout usually will not distort bores.
it just hardens where it sets.no skrinkage or expanding.just food for thought.
BTW, letting block set 12 hrs before meauring, takes that long for block to pull where it stops.

[cutting torch]

Thanks, Perf! That is the most detailed info I have gotten yet on block filler.

If I may bug you a little more......... Is that .079 spot in the bore going to be an engine killer?

torch

[toad490]

Hi Perf, I'm going to be doing my RB block in the next few days (finally) what are the "soft plugs" you mention in your last post? Thanks.

[perfmachst]

hello, soft plugs and/or freeze plugs are same. use brass plugs only.they do not rust out. the .079 part must be covered with block filler. you'll have to fill block at least somewhat past it.filling to botom of freeze plugs will not be enough to do anything much for support. might have to sleeve that hole first
if you don't want to use that much filler. If this is for a race motor, filling up to bottom of water pump outlets will give a lot of wall support. just food for thought. Hard Block brand is the best out there.

[cutting torch]

Thanks again, Perf!

torch

[toad490]

Originally Posted by perfmachst

hello, soft plugs and/or freeze plugs are same.

Thanks Perf, I've never heard them called that, up here its pretty much freeze.

[cutting torch]

Why are you hijacking my thread, Toad?!?!

torch

[toad490]

Originally Posted by cutting torch

Why are you hijacking my thread, Toad?!?!

torch

Aaaah, do ya need your belly rubbed?

[cutting torch]

Sure! Not too hard, though, 'cause I might fart!

torch

[toad490]

Well thats not nice, now you'll just have too get over it with a soother. ee: