smcurro

Saw an interesting thread over at v8buick:

http://www.v8buick.com/showthread.php?p=1356801

Got to thinking, how does this apply to olds engines? Is sonic checking a "must" when boring an olds engine 0.010", 0.020", or 0.030" over? What do you guys think?

J-(Chicago)

I don't think it's necessary unless you're going .060 over and making over 700 hp.

There's rumor that some GM casting forms are better than others. On the back of your Olds block there's a raised letter casting. Usually F1 or F2 etc. etc.
I believe those are the different factory casting forms used to cast the engine blocks.
Some are believed to be cast more "on center" than others, allowing more "meat" to be left over on the cylinder walls after a lot of over boring.
There aren't enough people out there sonic checking all of these different blocks and forms and posting the data, however.
Steve-O on this site might be able to elaborate more, as his machinist sonic checks his blocks now after he had a .060 stock block crack on him after 3 years of running 9 sec quarter miles with it. I'm sure he could tell you what "F" series the one he broke was.

csstrux

I thought that "f" number on the back of the block related to nickle content, is this wrong

Ice

It's a must if you're in a 442, I must check the computer system in my car before each drive to ensure the restrictor plate is operational to prevent Sonic Boom driving out on the interstate.

joe_padavano

It is a myth that has never been substantiated. ALL Olds blocks have "F" numbers on the back. The 65-67 425 blocks, for example, also run from F0 through F5 or 6. Do you really think that Olds reduced the nickel content in those blocks by 1967 then increased it again in the 455s in 1968? Not a chance. The "F" numbers refer to casting core variations or lots, in my opinion.

J-(Chicago)

Yes. It is wrong.

Although Oldsmobile blocks do have a much higher nickel content in them than a Chebby block. It's obvious from looking at cylinder walls after the same amount of miles driven.

smcurro

In the v8buick post it says sonic checking should be around 75 dollars. My biggest problem with sonic checking was that I called around and the only person I could find that does it charges a ridiculous 250 dollars.

J-(Chicago)

Yup.
The people that actually invest in a sonic checker usually have a long wait in that tool finally paying for itself. It seems they would like to speed up that process with quotes like that.

Seriously, how often does someone get a customer that wants a sonic check?
I'll bet not very often at all.

captjim

We do about one a month, maybe less. It takes a couple of hours at most. We charge $90. What engine are you working on? I have never heard of a 350 that had issues going to 4.125" or a BBO going to 4.185". 403s are supposedly thin-walled, but I have experience with them.

smcurro

So a 350 has no problem going 0.068" over? I'm working on my 350 right now but I was just asking generally about how sonic checking applies to Oldsmobiles. I wasn't planning on having it done unless all of you guys had said that it was an absolute must. Good info!

captjim

I have never done or heard of using a later windowed 350, but nobody I know that has done it to an older 350 block has had any problems. One guy at ROP bored his out to 4.185"!! I am not recommending that. The reason you go .068 to 4.125" is then you can use the plethora of 400 SBC pistons that are available instead of the very few options for Oldsmobile engines.

smcurro

heh, it would be fun to tell people you have a 362 olds small block. What is the compression height and wrist pin diameter of a 350 sbo piston compared to a 400 sbc?

captjim

The pins on the SBC are .920, vs .980 on the Olds, so the pins are lighter. Quite a few pin heights are available in the SBC 400 piston. You can offset grind the crank and use the 2" rod bore and get more cubes and stroke. Or, use the 1.890" Honda bore and add even more.Here are a few combo, there are a bunch,

CI Bore stroke p/h piston weight rod length rod/pin weights
375 4.125 3.510 1.560 485g 6.00 535g 118g

375 4.125 3.510 1.425 466g 6.125 540g 118g

387 4.125 3.620 1.260 451g 6.250 545g 118g

Steve O

It was a 1970 F1 block, it cracked right down the middle of the #4 main web and went up between #5 and 7 cylinders...

It was .133 thick there after the .060 overbore...

J your old "Fragged 455" 1972 F block will be going up there soon to be checked... It might just be the thickest Olds block ever cast

Im also gonna check a later Fa block and a 66 425 D block, the best one will be the heart of the rebuild

Thankfully the Olds block is quite a bit thicker than a Buick block