Where to start with a rusty block?

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pauls340

pauls340

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So I took this 2780930-340-7 (what the heck does the 7 stand for)stock 2.9.72 built bare block to a local machine shop. Their clean/ shot blasting cleanup is $100 which I thought was fair. He then took a look at the rust and said it would take a lot more. Bore, hone etc. Has anyone started with this and where did it go? I want to clean it up and sell it. Thanks
340 Bare block 72.JPG
340 Bare Block 2.9.72.JPG
 
If you don't have the main caps it just got costly.
360 could be bought complete if the blocks is good, for what it would take to use it if mains are gone.
Sell it and buy a 360/5.9
 
The 7 means that it was the 7th batch made on a single mold. That's a pretty high number. I don't know how many batches were generally made given a particular mold before they made another mold. Some say the lower numbers are better, but I really don't think that matters.

As far as bore size, the 340 is 4.040 standard, so if it is .060" all is not lost. For the 340 block, it may can go further, you will need to have it sonic checked to be sure.

As for the rust, take it to a competent machine shop and they can clean it right up.
 
How does it "get costly" without main caps? All it would need is a gentle align hone with some cheap 318 mains and all is well. I can get one align honed for about 150 bucks. Costly?
 
RustyRatRod said:
How does it "get costly" without main caps? All it would need is a gentle align hone with some cheap 318 mains and all is well. I can get one align honed for about 150 bucks. Costly?
Click to expand...
Yep and I even have a set of 318 caps I'd dell you cheap
 
if the block is oily get some pure white tide . put 1 cup per 3 gallons of water in a tub from home depot and soak it for a day.

rinse well

buy oxalic acid crystals online . mix them 1lb to 1 gallon of water .

fill the tub and soak the block for 3 days.

do not breathe the fumes ad do it in a well ventilated area.

your block will look new.
 
I bought 3 old rusty 8 3/4 pigs really cheap because they were 489 and 741 cases with 3.91 and 3.54 gears. They wouldnt even turn ! Been outside for years....
Well anyhow... I was at the bar and got talking to this OLD guy that used to be a machinist. He told be to soak them in Deisel and Acetone ( fingernail polish remover) for a few weeks . Said he did this with old tractor motors often.

It Worked ! Even the gears cleaned up ! I tossed the diffs (open) and bearings but used the housings and gears...
 
not sure but the - 7 would have been the number of core adjustments?
..not many make it past 9 and a -1 or should be virgin mould with original casting specs.
many different theories on this
 
diesel oil and acetone will not remove heavy rust, plus oxalic acid is far faster and far cheaper.
 
The lifter bores will need some particular attention. Any pitting needs to be carefully cleaned out so that rust particles will not later come out into the lifters and the rest of the engine. You can't hone them very much as excessive clearance there will lower oil pressure in the main galleries.
 
oxalic acid will remove the rust from the pits, however, using a small bottle brush occasionally in the lifter bores will speed up the process.
 
RustyRatRod said:
How does it "get costly" without main caps? All it would need is a gentle align hone with some cheap 318 mains and all is well. I can get one align honed for about 150 bucks. Costly?
Click to expand...

Stepping up to 340 main caps is a desirable mod on a 318.
Stepping down to 318 main caps on a 340 is not!
If your going to spend money on a align bore go ahead and get a set of 340 caps.
 
m880 said:
Stepping up to 340 main caps is a desirable mod on a 318.
Stepping down to 318 main caps on a 340 is not!
If your going to spend money on a align bore go ahead and get a set of 340 caps.
Click to expand...

I "just bet" using the stock 318 mains on a 340, you'd never know the difference.
 
RRR, are you the first technical editor?? Never seen one.
 
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