casting question

[MileHiSS]

Has anyone here ever heard of a 655 casting instead of a 656? Have you ever heard of a YM stamping on a 409? Just chasing the elusive wid goose chase. Thanks,
Dave

[CDNpontiac409guy]

Has anyone here ever heard of a 655 casting instead of a 656? Dave

ABSOLUTELY, Dave...
it's a 62-65 348.... truck application, and COULD also be the later over-the-counter replacement blocks.
To my knowledge, they're all actually "car blocks" ( a single small valve relief, instead of two giant ones ).
good block...
but still a 348

[Phil Reed]

Dave:
I have been told that these 348 truck blocks have enough cylinder wall thickness that they can be bored to standard bore 409. Would have to sonic test first!! They make a "cheap" 409....bore and drop in the 409 internals!!

[oldskydog]

Dave:
I have been told that these 348 truck blocks have enough cylinder wall thickness that they can be bored to standard bore 409. Would have to sonic test first!! They make a "cheap" 409....bore and drop in the 409 internals!!

Phil,
I guess you missed the thread on the "pencil test".:scratch

[poison ivy]

what is pencil test??? poison ivy

[1958 delivery]

what is pencil test??? poison ivy


With a freeze plug removed, you check the thickness of the cylinder bores by looking at the distance between them, rule of thumb, if you can stick a pencil between them they are not thick enough.
With big block chevys this test works as the 4 bolt HP blocks have very little room between the cylinder cores while the lo po 2 bolt blocks have ample room for a pencil to fit between. Frankly I don't know if this same situation applies to W's.

[oldskydog]

I'ts not a matter of 4 bolt vs 2 bolt. It's a matter of casting cores....396 vs 427 on BBC or 348 core vs 409 core on W. If the pencil goes between the cyls then it's the thinner cyl wall casting core.

[Phil Reed]

Phil,
I guess you missed the thread on the "pencil test".:scratch

The only pencil test I know of is where you place one under a woman's breast............:bow :bow :bow

[oldskydog]

The only pencil test I know of is where you place one under a woman's breast............:bow :bow :bow

OK.....I'll take the bait.....elaborate.:doh

[Tom Kochtanek]

I'll tell you in a PM :).

TomK

[Skip FIx]

That's the only one I knew of too Phil:)

If the pencil falls don't need a bra!

[1958 delivery]

I'ts not a matter of 4 bolt vs 2 bolt. It's a matter of casting cores....396 vs 427 on BBC or 348 core vs 409 core on W. If the pencil goes between the cyls then it's the thinner cyl wall casting core.

It is a matter of 2 bolt vs 4 bolt (big blocks) as the 4 bolts had the thicker core and the 2 bolts don't. If you've ever found a 2 bolt with that thick of a core it was a mistake.

[oldskydog]

It is a matter of 2 bolt vs 4 bolt (big blocks) as the 4 bolts had the thicker core and the 2 bolts don't. If you've ever found a 2 bolt with that thick of a core it was a mistake.

Ok, anybody have a 4 bolt 396 block laying around? If so would you pop the freeze plug on the side and see if you can fit a pencil (#2, not the fat first grade pencils) between the cyls?
Do you really think the engine foundry used a different core for 4 bolt castings than 2 bolt? The core was designed to provide sufficient cyl wall thinkness for the final bore. With a few exceptions,(as in the 961 castings used in early 66 427 blocks before the 942 casting was used . You can bet that they had 427 innner cores .They probably just hadn't issued the new casting number yet.) the casting number was used to differentiate between the different displacement engine castings otherwise there would be no reason to change casting numbers, just cast them all the same thickness and bore them to what ever displacemnt bore you wanted. The only problem with that is that GM was cheap and didn't want to waste money on excessive materials and if the cyl wall castings were too thick it likely would affect the cooling . It is my humble understanding that 4 bolt blocks were pulled from the same pile of raw castings as the 2 bolt. They were then machined for the specific application. But then againI could be wrong. It wouldn't be the first time. I thought I was wrong once but I was wrong.

Where's Fran when you need him?:D

[oldskydog]

I'll tell you in a PM :).

TomK

Thanks for explaining that Tom. I know I haven't exactly led a sheltered life but that one I must have missed although with a little imagination I think I figured it out. I only had to consider the source.:rofl

[Phil Reed]

I thought I was wrong once but I was wrong.

Where's Fran when you need him?:D

:rofl :rofl :rofl :rofl :rofl :rofl

THAT is the pencil test!!!!

[chevymusclecars]

Cecil

I agree with you, there were some of the 961 blocks bored and used as early 427 blocks when the 942 was not yet available, the 961 block was only made in two bolt main. The 961, 962, two versions and 942, again two versions, can all be bored .125 oversize. The only difference I can see in the two and four bolt mains is that the four bolt main blocks are tapped for an oil cooler and are machined for the four bolt main caps.

Bill

[1958 delivery]

Cecil

I agree with you, there were some of the 961 blocks bored and used as early 427 blocks when the 942 was not yet available, the 961 block was only made in two bolt main. The 961, 962, two versions and 942, again two versions, can all be bored .125 oversize. The only difference I can see in the two and four bolt mains is that the four bolt main blocks are tapped for an oil cooler and are machined for the four bolt main caps.

Bill

Yep, I forgot about that early 396, yes the 2 and 4 bolt were both thick wall blocks. The later years, essentially 1967 and above were cast from different molds. Go look if you think I'm kidding. 2 bolts generally will go 90. but barely.

[oldskydog]

Yep, I forgot about that early 396, yes the 2 and 4 bolt were both thick wall blocks. The later years, essentially 1967 and above were cast from different molds. Go look if you think I'm kidding. 2 bolts generally will go 90. but barely.

I've got an early 65 961 2 bolt and it is not a thick wall casting. The pencil easily goes between the cyl walls because it is a 396. My 66 942 2 bolt 427 will not take a pencil between the cyl walls.

[hogmotors]

Phil,
I have one of those 655 348's or "X" 348 blocks & wondered about the wall thickness as well So, we checked several blocks-though NOT as thoroughly as if we were going to bore WAY out-just "fishing".
They were ALL(several 348's inc. the 655 & 4-5 409 blocks of varing vintage).250 wall in every place we checked.