Do I read the chart below correctly? The 68-72 BB with a number of 396021 and simply an "F" after it means a stick block and the other "F" with two vertical hangers and a base then must mean an auto block.


If I read this correctly then does that mean the mount for the bellcrank ball is not present on the latter? Also, if the crank has not been replaced would that mean the block with the "F" code would have the crank drilled for the pilot bearing?


ID/ Casting
Code Year(s) CID Number Notes
A '65 425 381917?? 1st year, big cars.
386525
B '65 400 389298 442 only, one year only.
D '66 - '67 425 389244 Big-car engine. Toro is different internally.
E '66 - '67 400 390925 442 engine [VERY rare].
F '68 - '72 455 396021 Most common big block. Two types of "F"
letters: stick type, and one with two vertical
hangers and a base.
Fa '72 - '76 455 396021 Very common big block.
G '68 - '69 400 396026 442/Vista/etc. engine.
L '76 455 231788 Motorhome, maybe marine also. GM made motorhomes
from '73-8, maybe in all?

 

No.


All 1868-1972 455s are F blocks & are 4 speed compatible.


The Fa block came out in 1973. Some 1973 blocks are 4 speed compatible. Most 1974-1976 Fa blocks are not.

 

I'm confused. The descriptionabove "stick type" just refers to the "F" itself and its font (sans serif). The later ones had a font with serifs. Only a small portion of any of the 455 cranks are drilled for a manual transmission input shaft, but all can be - or a manual crank can be installed in any olds 455 engine.

Steve

 

No, you are reading that wrong. The description "Two types of "F" letters: stick type, and one with two vertical hangers and a base." is not referring to the block, it's a poor attempt to describe the FONT of the letter "F" used on the casting. The description "stick type" is trying to say "sans serif" and the description "two vertical hangars and base" is trying to say "serif" font.

Sans serif: F

Serif: F

Both of these are "F" blocks and both have the provision for the clutch equalizer ball fitting. Note that despite what the FAQ says, there are documented uses of the "F" block into the 1974 model year, based on the VIN derivative stamp. The "FA" block was the more common block for the 1973-76 model years, however.

Trivia note: the term "serif" refers to the little "flags" at the ends of each leg of the letter. "Sans" is French for "without" so "sans serif" means "without the little flags".

 

Joe thank you for the information. It would've made better sense for the chart to say there are two F blocks (the only difference is the font style used)
So now am I correct that both "F" blocks do have the mounting for the bellcrank?
Does that also mean that both "F" block have their crank drilled?


I'm only referring to "F" blocks not the "Fa" blocks.

 

Again NO.


Finding an F block is no guarantee that the crank is drilled. Keep in mind how few Oldsmobiles had manual transmissions.

 

Thanks for the information.

 

As Dave has noted, EVERY 455 block cast from 1968-72 (and some after that) were "F" blocks, with both sans serif and serif casting letters. Every one of them had the boss drilled and tapped for the clutch equalizer ball stud. Most of them were bolted to automatics and did not have the crank drilled for the pilot bearing. The configuration of the crank is unrelated to the version of the block. Bottom line is that the vast majority of Olds cranks were not drilled for a pilot bearing. Unless the motor is still bolted to it's factory-installed manual trans, there is no way to tell from the outside if the crank is drilled without actually looking at the crank flange.

 

Here is something I found on the web about the "F" block 455's.


"Oldsmobile blocks aren't made of mush, rather, they are made of high quality cast iron with plenty of nickel to make it strong. Olds big block engines were cast with extremely high nickel content until mid 1970. You can easily spot the difference in the shape of the "F" near the oil sending unit. Look at any 1968 1969 and early 1970 block and the F will be different in shape than any late 1970 to 1974 block. In 1975 the nickel content was lowered even more. Some of these later engines will have a mounting hole for a clutch swivel rod ball, some will not. This can always be machined. "

 

Forget about the nickel content BS. It does not matter. All of the blocks are adequate for any street application you are thinking of.


Focus on finding a block that has the 4 speed stud boss & on finding a good crank. If it is not already machined for the 4 speed input shaft then have it machined. Simple.

 

Don't believe everything you read on the web, especially with regard to nickel content in Olds blocks. This urban myth has never been proven. More to the point, why would Olds only do this to the 455s and not the other motors? It's BS, especially when someone tries to relate it to the "Fn" number on the bellhousing face of the block. Again, 425s were cast with numbers from F1 through F6 or higher, but for some reason no one relates those to declining nickel content.

 

Thanks guys for the information. I guess if you want to convert to 4 speed there's only one way to know for sure and that is to look at the block and crank.


Thanks again,
John