292 overbore


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By petew - 16 Years Ago
I have a 292 that is currently at .060 over. What is the next over bore size or are they done @ .060 ?
By charliemccraney - 16 Years Ago
They can often times go over .060. Mine's at .070. That's .020 over 312.
By 46yblock - 16 Years Ago
My last 292 was .080 OS.  There was a significant amount of material gouged from one of the cylinder walls, but it held water until teardown.  Apparently a piston seized due to chronic, very rich F/A mixtures, or the engine quack that put it together left too little piston clearance.  It was a '56 block.
By bird55 - 16 Years Ago
Have the bare block sonic tested and you'll be better assured to know what you have left to work with.
By speedpro56 - 16 Years Ago
I'm with Alan. When in doubt go for the insurance and have it sonic tested. On some Yblocks you can go too a 3.905 bore using a scrub 283 piston which sets about .005 in the hole. I believe the 283 .030 over is the 3.905 meaning you don't have to go quite that far but the pistons are a lot cheaper than custom made ones.Tongue
By pcmenten - 16 Years Ago
Well, I can give you an opinion about what blocks will overbore. For starters, what is the casting number of the block?



Blocks that are likely to overbore well are ECZ-C EDB-E B9AE. You can check for core shift on the most problematic cylinder; the last cylinder on the passenger side of the block. It's underneath where the starter would be. Pull the freeze plug and look to see if the cylinder is tilted. You can try pulling other freeze plugs and comparing the gaps with a drill bit.



I have two different 312 blocks, both ECZ-C. One has the tilted cylinder, but it's already .060 over. The other block is straight. Ironically, the block with the straight cylinders has the stock bore. I suspect it could go .100 over.



I also had a C1 block with a very tilted cylinder. I returned the block and kept looking.
By PF Arcand - 16 Years Ago
Yes sonic testing is desirable in your case. I believe 312 pistons were available to 3.840" or 0.040 over from the factory, the biggest for Y-Blocks. Your current displacement is about 304" Unless your engine needs an overbore you won't gain a lot for the cost & trouble, unless you take it out to the 3.9 + range & then you will likely have thin walls & no further overbore room.
By Ted - 16 Years Ago
petew (8/21/2009)
I have a 292 that is currently at .060 over. What is the next over bore size or are they done @ .060 ?
As Charlie mentions, the next overbore in your case will be for the 0.020” over 312 but pistons may be easier to find for a 0.030” overbore.  As far as how much you can bore any block, they do vary so sonic testing is the prudent thing to do.  I have an ECZ block that’s thin due to core shift and 0.015” over was all I felt comfortable in cleaning the block up at.  I’ve been taking the C2AE blocks out as much as 0.110” over after sonic testing to confirm where the core shift resides.  The cylinders can then be offset bored to equalize cylinder wall thickness if taking out a bunch in the first cut.  Where you’re just cleaning it up to the next oversize, then sonic testing will just confirm that adequate material is still there for the long haul.  New pistons and rings for up to 0.060” over for the 312 are still available so if the block can handle it, go for it.
By John Mummert - 16 Years Ago
You can use 312 pistons in a 292 so 3.830" should not be a problem. BTW: you cannot use 292 pistons with 312 crank & rods

I didn't see what 292 block you have but all blocks that were machined as 312's were also machined as 292's. In other words, they were the same casting. ECZ, EDB(Cleveland), B9AE  and even some rare C2AE 312's built as over the counter replacements and marine engines.

Nobody thinks twice about boring a 312 block .030 or .040".

I've taken apart blocks that were as thin as .068" that were not cracked. One was raced extensively. It was a 1955 292 bored .125".

I wouldn't put one together like that but .090" wall is probably all you need for street use.

One major change in block castings is the design of the cylinder walls. Up to the B9AE blocks the cylinders are thickest at the top and get progressively thinner toward the bottom. C1AE and C2AE are thinnest half way down. I think this was easier to cast, not a reliability change.

My 2 cents worth: If you are building a high performance engine, sonic test by all means. If it is a 220hp street cruiser, punch it out and don't worry about it.

By petew - 16 Years Ago
Thanks for all of the responses guys. I agree I would not bore the block without a sonic check and in this case I wanted to determine if it was even worth while to proceed with that.

Apparently it is..... The block is a C2AE 8015C casting that is currently a very tired .060 I am keeping it as a spare since I now have two Y block vehicles.

So it seems that with a good sonic test I can go with a .030 312 piston. I imagine that the pin placement is same on the 292 and 312 pistons ?

By Ted - 16 Years Ago
petew (8/25/2009)
.....I imagine that the pin placement is same on the 292 and 312 pistons ?
Yes.