This is the result of the sonic test on my spare 292. Shop says there is too much core shift to make boring reasonable. Opinions? Chuck

Y's guys rule!
Looking for McCullouch VS57 brackets and parts. Also looking for 28 Chrysler series 72 parts. And early Hemi parts.

MoonShadow, 292 w/McCulloch, 28 Chrysler Roadster, 354 Hemi)
Manchester, New Hampshire

Chuck:

I think you want to supercharge this engine, and with the readings as low as .140, you should probably not bore more than .040 over.  I also think you want to bore bigger than that, so it's probably not a good idea.  With the blower, I would strive for .120 wall thickness after boring.  As stated above, you could sleeve the thin ones, but 292 blocks are not too hard to find.  They didn't all have core shift.

John

John - "The Hoosier Hurricane"

Chuck.  Granted that the block has what appears to be significant core shift on the drivers side bank but it still looks to be able to go as much as 0.080” oversize even if not offset boring the cylinders.  But depending upon how much oversize you’re considering and the accuracy of the sonic test, then the block in question can potentially be bored even more.  If considering a reasonably heavy overbore, then I’d recommend having the machine shop offset bore into the heavy sides in order to equalize cylinder wall thickness at which rate you can consider overboring 0.110” or more.  Double check the sonic check sheet to insure that the #1 cylinder was numbered for the Ford and not for the scrub lineup as being reversed could prove to be disastrous if pursuing offset boring.

 

I do have a question regarding the wording on your sonic check sheet though.  It lists ‘thrust’ for each bank but it’s not clear (to me anyhow) which side of the cylinder is really being referred to as the opposite side of the cylinders in both cases are listed as ‘up’.  It would make more sense if one bank was listed as ‘down’.  But if ‘thrust’ just refers to the side of the cylinders closest to the outside of the block, then that would explain it.  What’s driving this thought process is that when looking at a block from its top, the major thrust within the cylinders on the drivers side would be the side of the cylinders closest to the lifter valley while the major thrust on the passenger side would be the side of the cylinders closest to the outside of the block.  If offset boring a block, it’s imperative that the sonic check sheet be absolutely clear as to the orientation of the numbers within the cylinder.

Lorena, Texas (South of Waco)

And of course John is right about the supercharging.  If going the blower route, then leave more cylinder wall in place.  My values were assuming the engine being naturally aspirated.

Lorena, Texas (South of Waco)

Chuck,

               Sonic tests tend to average the area under the probe. there can be more or less in any particular spot. If these are the minimums you are likely OK for Normally Aspirated. If it's for only one spot on each section, you don't know much more than you did. Listen to John on the blown recomendations. Too little wall will get you wet pistons.

                                                  Frank   

Frank/Rebop

Bristol, In ( by Elkhart) 

Thanks guys,

I was thinking towards the blower motor to be done right once! The machine shop seemed to think that offsett boring would be too expensive because of the many passes required. I do have another block to tear down plus the one in the Vicky. One has to be good.

PS: I put a closed oil fill breather on and attached it to the air cleaner (without the blower). Result was the dip stick was getting pushed out by oil pressure. I put the crankcase breather back on and found some improvement at the top BUT it now pushes oil out the breather as I drive. Think I might have some blowby issues? (and thats with a PCV valve!)

Y's guys rule!
Looking for McCullouch VS57 brackets and parts. Also looking for 28 Chrysler series 72 parts. And early Hemi parts.

MoonShadow, 292 w/McCulloch, 28 Chrysler Roadster, 354 Hemi)
Manchester, New Hampshire

I'm curious to know what the casting number of that block is. I'm going to guess that it's a C2AE.



Is it possible that instead of core shift, that the cylinder bores are off?



Would it make sense to leave the 'thrust' side of the cylinder slightly thicker than the non-thrust side?



Is it true that boring the cylinder .060" takes .030" off of the cylinder wall? If the before were .240", the after would be .210"? Heck, if I knew I had .240" walls, I'd be tempted to bore the block at least 1/8".

Best regards,



Paul Menten

Meridian, Idaho

Actually it is a Canadian CEBY block. I was going to 30 over 312 pistons if I could. Thats why the sonic check. Yes I could go to a 40 over 292 but I was hoping for BIGGER! I have a couple more blocks to check. Chuck

Y's guys rule!
Looking for McCullouch VS57 brackets and parts. Also looking for 28 Chrysler series 72 parts. And early Hemi parts.

MoonShadow, 292 w/McCulloch, 28 Chrysler Roadster, 354 Hemi)
Manchester, New Hampshire

Chuck:

As you know, I bore 292 blocks to .030 over 312, put in 312 cranks, and supercharge them.  Never sonic checked them, never a wall failure.  Guess I've just been lucky.  Never had a Canadian block either.

John

John - "The Hoosier Hurricane"

pcmenten,

            You are correct about the amount from each wall being half the total bore increase. You really want to keep a .125 wall on the thrust side. With the blower, depending on the amount of boost, at leasr .100" wall is needed. Remeber, especially with the blower, you'll lose more to blowby than you'll gain from the displacement increase. As the walls get thinner they start to flex more. More cylnder pressure equals more flex equals more blowby. Just like other sports, stiff is GOOD!!

I can bend a flat piece of cast iron .100 thick with my bare hands, not much, but a measureable amount. the cylindrical shape helps, but the pressure in a cylinder in a running engine is a lot more than I can put out. I've seen spikes at over a 1000 psi.

Frank/Rebop

Bristol, In ( by Elkhart)