i just bought a used bowtie block with 4.600 bore.the block is fine but there is one little problem:there is small crack from headbolt hole to the cylinder.since the hole is blind there is no water near the crack.by the looks of it the engine has been running with the crack already there.is it dangerous to just fix it or should it be sleeved.there is a lot of iron around the crack and the bolt hole it self is ok.the crack is not visible there.it appears to be cracked only near the surface and the crack itself is very thin like a hair.i talked to a seasoned alky mechanic and he said you should see our cracks.but i know here is better knowlegde about american iron.so,what should i do?ps.the block was cheap!?

Does the crack extend down into the ring wear area? If it does go down that far can you see a difference in the wear pattern on the two sides of the crack? If it does and you can I would sleeve it. If it doesn't or you can't see a difference you might try running it, accepting that there could still be problems.

What I would do if you haven't already is take it to a decent performance machine shop and have the crack area magnfluxed so you can be confident on where exactly the crack stops. This is not always visible to the naked eye. While it's there pay them to do a pressure check, make dead sure the thing doesn't leak water. If it does leak water it's going to leak into the chamber where a hydraulic lock can destroy the whole shortblock. $$.

I've run blocks that had cracks in race engines before, a block is not just automatically scrap because it has a little crack somewhere.

Tom

thanks for answering,tom!the crack in deed goes down but not so deep where the piston rings are.it is surrounded by a thin layer of carbon and is not sticking up so that there would be any wear marks.it looks harmless but i am checking the block thoroughly anyway.it is going to be a sweet street engine:500 cid+8-71 and now with that bore my dart pro 1 heads are going to start flowing some serious air.atop a couple 8896`s and it`s cruising time.now,back to work,gotta pay those big pistons soon enough.

Blower? Did you say blower?

You really need to get that magnafluxed so you know where exactly it goes -and doesn't go. Blower motors are hard on head gaskets. That crack almost surely goes through to the head bolt hole. between these two things magging is called for. If the crack goes through into the bolt hole you may want to heli-coil the hole rather than take a chance on pulling the threads or distorting the cylinder wall at the crack. Studs are called for here.

Tom

thanks again,tom!i will be using head studs and the crack is going to be welded at wärtsilä marine diesel plant and sonic tested and `fluxed.i use SCE copper head gaskets and they work great.the block is getting o.rings so there shouldn`t be major problems with cylinder pressure escaping.i almost forgot even myself that i will be supercharging the thing,so the first question was a little stupid,of course it needs to be fixed.you learn as you go!

after welding the crack the block will need to have at least that cylinder bored and that deck shaved to get things back to straight. I'd consider boring all eight cylinders to the next convenient oversize and taking 5 or 10 thousandths off both decks just to keep things even.

Tom

I hope they "furnace weld" it using a rose-bud torch and a high nickel rod or else an expert that knows how to use the powder weld process!!

Good luck with it and please come back and tell us how it was welded.

pdq67

the guys there can really weld.those big v-48 diesels don`t come cheap and need a weld or two occasionally.yes as tom said,those measures has to be taken,there is enough iron to bore the block 4.625,but that is the most it can take.i think it will be plasma welded and when done i will let you know what the outcome was.i don`t want to sleeve the engine just for one crack and besides my dream of having a 500cid of my own is about to come true.can`t wait to start building it!!!ps.a new cnc-machined bowtie block costs here over 4000 us dollars including shipment etc.

>> "a new cnc-machined bowtie block costs here over 4000 us dollars"

Wow, I was wondering about that. Seems like running across a used one over there would be pretty rare. Actually, I'm surprised it's not more with shipping, import duties, all that.

best of luck to you on this, feel free to post anytime.

Tom

your reasoning was correct tom,i wouldn`t have bought if it were a bonestock block.most big bowtieblocks here have pro stock background and if yours has just one small crack ,you are lucky. judging from the casting number mine isn`t very old and comes from 8 sec street `vette.the only reason why the block doesn`t cost more is that there is practically no profit for the selling party.race only parts are for just servicing customers in hope that they buy their other stuff from the same shop.hope that makes sense!(you should see our plant`s parking lot:100 riceburners, a couple old volvos and one bright yellow 9 sec pro street malibu ss in the middle of it!)but thanks for now tom and everybody else who took their time and read these notes!