400 block

I have a STD/STD/STD '77 400. does anyone have experience sonic checking the cylinder wall thickness of these block's? what kind of numbers on the thrust side? what's considered a good thickness? .200?

Thanks

.200 on the thrust sides for all 8 holes would be a fantastic block. I've tested a lot of Mopar blocks over the years and typically what you'll find is 5 or 6 good holes in a block and 2 or 3 bad holes. Ma Mopar's quality control sucked during the 70's. Whoever ran the foundry that cast Chevy blocks knew what they were doing. The Mopar foundry wasn't so lucky.

is .190> more common? and thanks for the reply Andy.

Random numbers are the common result! I'll sonic check Chevy blocks and they are nice and consistent from hole to hole then switch over to a Mopar block and one hole will be .243 thrust and the next hole will be .147 on the thrust.

They are just all over the map. Core shift is very common as are random thin spots. I'd say that over the past 20 years roughly 50% of the Mopar blocks I sonic check are too thin to build into race engines.

I'm building a low deck 470 right now and I passed on three blocks before I found one that was good enough to use.

thanks again.

I just built a 400 stroked to 512. I had one of the good blocks 6/28/71 thick web but it was 30 already and done by a blind man with the shakes so I couldn't use it for my 035 over bore needed.
The shop got me a 74 cast block that sonic at a little over 200 on each hole. I think 219 or so. When they were all said and done with the final hone with plates it was still just over 200. Even the deck was close but not perfect to achieve 0 deck.

Don't have it fired yet but they were real happy with the #'s and consistency.
Ron

I bought a sonic gauge, I scanned both the 400 and the original to my car 383. (6-26-68) like was stated above, both blocks are all over the place. I am not looking to build max effort strokers though, so i'll do the usual band aids to help the motors live.

Ultra sonic thickness gauges are addictive, I scanned everything in sight while learning to use it. scanned my Cat, he's good for an overbore, lol.......

Thanks again for the info.

Do you remember what your minimum thrust side numbers were for these two blocks?

Can this be fixed by sleeving the block? I have access to a machine shop, so cost is less of an issue. S/F....Ken M

Absolutely. Be aware that sleeving alters the other bores, so you'd want to sleeve first before boring and honing the others. The person above who posted every thrust side at or above 0.200" should have bought an armload of lottery tickets while his luck was running red-hot.

To back AndyF's observation, nearly every 4.25" bore BBC block will go to 4.375". It's so common that pistons are available at 0.125" over.

R.