Okay, So What's the Minimum Cylinder Wall Thickness Again?

[410bruce]

Is it 0.125? If it is, I have no blocks I can use.
I'm scrapping two 390 blocks, the 352 I was interested in is at .030 and measured a 0.108 and will need to be bored, the .030 5.0 I thought was good is at 0.110 and will still need to be bored, the other 302 I have is at .040 but I'm getting .120s-.140s on the thrust sides but  measly .080s between the cylinders. And, it needs a bore.
Man, it's looking like I'll be going back to a 460 for my torque and "efficiency" engine. lol. I definitely have usable blocks and cranks for them.
I know I could find another standard bore block somewhere but remember, I'm trying to use what I have. Unfortunately, that doesn't seem to be working out so well.




.

[67xr7cat]

Depends on where it is thin. If is on the sides can go .090"-.100" and be ok for street use. Also is it a thin spot or thin top to bottom. Major thrust want thick.  If it is one cylinder a bit thin on just one side can off set bore it too.  Really need see a sonic map and know how the engine is to be used to say what is ok.

[plovett]

I think 0.125" is a good conservative number.   It depends on where the number is, as you alluded to.  You mentioned different numbers on thrust and non thrust sides.   Certainly non thrust sides can go lower, but I don't think I'd want to bore that 302 with 0.080" between the cylinders. 

JMO,

pl

[FERoadster]

Bruce: I've got a 351W sitting here in Brookings. Probably 20K miles It's a rebuilder block I installed in a 1978 E250 van. Van rusted out and the block & trans have been sitting inside for close to 30 years. $300 if you pick it up. The engine still turns over, Missing the distributor otherwise  complete, but includes a Edelbrock 351W intake.
Richard >>> FERoadster

[410bruce]

Bruce: I've got a 351W sitting here in Brookings. Probably 20K miles It's a rebuilder block I installed in a 1978 E250 van. Van rusted out and the block & trans have been sitting inside for close to 30 years. $300 if you pick it up. The engine still turns over, Missing the distributor otherwise  complete, but includes a Edelbrock 351W intake.
Richard >>> FERoadster

Hi Richard. Thank you very much for the offer but since you say it's a rebuilder block, I'm assuming you mean it was rebuilt and most likely bored at that time. With the luck I've been having with previous bored engine cylinder wall thickness, I think it's best to find a standard bore block.
Again, thanks for the offer. I really do appreciate it.

[Joe-JDC]

IF all your blocks are coming up thin, I suspect that your sonic tester needs a good calibration, before getting rid of those blocks.  If your readings are off .020", then you are good to go on all those blocks.  You need to double check that tester against a known thickness, known material, and prove it's repeatability.  Also, what are you using for the lubricant?  Glycerin, white grease, vaseline?  I found white lithium grease to be the most consistent and make sure the sonic test head has the correct radius to fit the bores.  Joe-JDC

[410bruce]

IF all your blocks are coming up thin, I suspect that your sonic tester needs a good calibration, before getting rid of those blocks.  If your readings are off .020", then you are good to go on all those blocks.  You need to double check that tester against a known thickness, known material, and prove it's repeatability.  Also, what are you using for the lubricant?  Glycerin, white grease, vaseline?  I found white lithium grease to be the most consistent and make sure the sonic test head has the correct radius to fit the bores.  Joe-JDC

Hi Joe. I'm using one of those cheap ebay sonic testers. Using cooking oil for lube. I trimmed the test head to fit the bores.
I came up with great numbers on my 410 block before boring. If I remember right, they all came in between .160-.200
Thanks.

[TomP]

I don't trust sonic tests. The best way to verify wall thickness is to measure it directly and that can be done with a homemade tool that looks like a pair of scissors.
 The late John Heida made such a thing to check his engine and made several sets with different offsets so that would go part way around the bore even though the deck hole is offset. Just strips of 1/8" by 1/4" steel welded together. Pivot point is the same from both ends which have 90 degree pointed tips and you can meaure the gap up top which is the same as what it's pinching at the bottom. He used a piece if 1/8th flatbar... if that piece of steel doesn't fit in the gap it's too thin for his needs to check further. After a few blocks you know where to check first and he'd check that and could check a dozen blocks in a half hour. For free.

It's quick it's easy to use and easy to verify. Calibration is dead simple,  if both ends close together, both ends open the same amount.

[410bruce]

I don't trust sonic tests. The best way to verify wall thickness is to measure it directly and that can be done with a homemade tool that looks like a pair of scissors.
 The late John Heida made such a thing to check his engine and made several sets with different offsets so that would go part way around the bore even though the deck hole is offset. Just strips of 1/8" by 1/4" steel welded together. Pivot point is the same from both ends which have 90 degree pointed tips and you can meaure the gap up top which is the same as what it's pinching at the bottom. He used a piece if 1/8th flatbar... if that piece of steel doesn't fit in the gap it's too thin for his needs to check further. After a few blocks you know where to check first and he'd check that and could check a dozen blocks in a half hour. For free.


It's quick it's easy to use and easy to verify. Calibration is dead simple,  if both ends close together, both ends open the same amount.

Hi Tom. Is there any pictures of this tool available?

[Blueoval77]

Decent sonic checkers are pretty cheap and accurate. Use the China rail to verify its accuracy . You have to change the setting on the tool to correspond to the material you are measuring. To be accurate its not always the one it should be. WHen I use the cast Iron setting its off a little.

[Sand hauler]

Pics or drawings of it would be great. Cool idea

[Joe-JDC]

I have a wall of an actual cylinder that was split, and have ground a couple of flat areas that can be measured with a micrometer to calibrate my tester with before each sonic test.  Ford iron, Ford cylinder material, and has radius of bore of the split cylinder.  Can't get much more accurate for a calibration test than that.  Joe-JDC

[TomP]

I never took any pictures but looked like a pair of long thin scissors. Maybe 10" long quite thin. You went down the deck coolant hole and the bore and pinched. If you got .100" clearance at the top punch points that was what the wall thickness was down below. But since deck holes are not usually found on the thrust side he made another set that bends around... they looked like you drove over that pair of scissors.
 Clever but saves a ton of money compared to spending fifty bucks each for a shop to test ten blocks that are not going to be used. The buggers would get an .065" reading on the first hole but still test all the rest and charge him full price. After wasting $500 on unusable block checks he made the tool and could take it to the wrecking yard and check engines with heads off but still assembled. If it's .200" thick above the piston it's worth getting, if it's .120" thick there, maybe not.

But shops can be like that. Remonds me of a guy who send his newly bought 66 Fairlane in to a detail shop. They are cut polishing it and the vibration of the polisher knocked a bug chunk of bondo off the bottom of the quarter. They kept on polishing of course!