Duke94

My machine shop told me today that there is a crack in the water jacket of my 71' small block. It's about 2 " long and goes from the water jacket to the lifter valley in between 2 cylinders. He said he could fix it with some sort of drilling and tapping operation (I didn't understand what he was talking about)and then leak test it. I was trying to keep this restoration a "numbers matching" job. Any recomendations?

AlwaysWave

Sight unseen I'll say this. If the crack does not run into a hole, then a hole must be drilled at the end of the crack to stop it. Then the crack must be "v"d out with a carbide rotary file (not a grinding wheel) to a depth past the crack depth. Then heat the cast iron and lay in a nickel base and finish the fill in with brass. Then blend off any critical surfaces.

I can't say that your engine shop will agree with me, but that's how we fix cracks in cast iron stamping dies.

backtrail69

can you get a new used block at a swap meet or something

JB

On a '69 SB, an original matching #s block kicks the value up $2K or more. If the block is fixable, I'd fix it.

JB

45ACP

Yeah, I know where he's going with that. Start at one end of the crack. Drill + tap a hole. Run a bolt with thread locker into it and let it set up. Cut of the bolt flush to the block surface. Then drill + tap the next hole overlapping the last one 1/3 or so, which you then run a bolt into . . . etc, etc until the crack is plugged full length.

If he's any good at all this repair method will work very nicely.

Crash Dummy

To those who have responded....

Let's say you wandered into a sale of a '71 Corvette and asked about the engine history. If the owner mentioned that the block was cracked(no matter where) & repaired would you consider it a good *matching #'s* investment? I would definitely agree to try to salvage the block if possible.

On somewhat the same subject.... what really differentiates a matching #'s engine to another vette engine from the same year besides the ser#? What stops anyone from resurfacing the identification plate... restamp it with the original block info... install the heads, rods, pistons from the original engine & then claim it is the matching #'s engine? I wouldn't put it past that over 1/2 of the vettes that went through used car lots in their lifetime might not be the original matching #'s that are represented. Maybe I am just a pessimist, but if there are other things besides the heads, casting # on the back of the block, manifold & serial #(things that you can access without tearing the motor down) that would help prospective owners make a determination I would like to hear it.

Oldguard 7

That depends on wether you will: sell the vert at a later date keeping in in mind that non #'s matching fall below resale value. However if you are going to keep it then it shouldnt make any difference. As for me I would get another block. Now you are justified in getting a big block engine :)

VegasJen

bgrice, as to what you asked in your reply, if the #s matching thing was important to me, i would still be skeptical of a repaired block. repairing cast iron is a little like voodoo. some people say it can be done and some people say it can't. of those that say it can, maybe half of them would screw up the repair. i'm not saying that i know one way or the other but before i agree that a repaired numbers matching block is worth an extra $2k, i'd have to be convinced it was a solid repair. you would provide full disclosure, wouldn't you?
personally, i'd put a crate in it and keep the cracked block for some numbers matching guy that cares about that stuff. this way you can drive your car with one less concern for it's engine. if you do decide to sell it, you don't lose that much since you will still have the original block and let the buyer have the repair done at his expense. JMHO.

Desertdawg

You might want to ask the guys in the FCR section on the value of the original block, and what the procedure is for re-stamping another one...

http://forums.corvetteforum.com/zeroforum?id=77

tippi58

To be the devils advocate, matching numbers makes me laugh at times. We replace most everything with "repo" parts when they wear out. :chevy:

Whats so special about the engine block. :confused:

Your car probably has new tyres, rubbers, battery, A/C, interior panels, brakes, shox, springs, strut rods. :reddevil

Unless u want NCRS go with a "good" block rather than the old cracked one.

Small blocks chevs take a lot of s... before cracking so u can guarantee its had some serious abuse.:cuss:

Would you stick with a worn out part in your vette when u knew you could get a better quality replacement.:skep:


Food for thought or ??

:cool: :cool: :cool:

DREGSZ

Why did the block crack?
and has that problem been 100% remedied?
Was is a plugged or bad radiator, bad water pump, bad thermostat, leakingradiator hose?
Blocks don't just crack.
I think we all assume you fixed the cause, but if you didn't, or aren't sure then you may be replacing the bulk of your cooling system.

(As I just did, I have a cracked block too, I'm looking into a 454 swap)

Duke94

Thanks for all the comments. I guess I'll take the safe route and replace the block since I didn't buy this car as an "investment" anyway. Sure has been a money pit though. Looks like the next guy will get a nice car but w/o "numbers matching".

JB

Re your question about restamping a block to get matching #s--my understanding is that that can be detected fairly easily because of the machining marks. If I remember right, the factory surface had "swirled" marks which decking the block takes off and replaces with straight marks.

Cluchdust's suggestion is an excellent one--stick a crate engine in there, and keep the old block, crack and all, so that you still have the matching #s block if you sell the car.

JB

Sigforty

Sounds like time for one of those nice crate motors out there. I had my motor break a couple of pistons a while back. I went with the ZZ4 and have not looked back. The motor is great and has a warrenty. Not to mention if you repaint the zz4 block from black to orange it looks awesome with the aluminum on it.

Mark B.