[grandam1979]

This will help, some engine codes got reused in later years.

[caddor38]

Originally Posted by tom s

I remember back in 2014 you were trying to make a 63 421SR block to be a 63SD block!I see a pattern here!Tom

Yes that was me 8 years ago and yes it was not an SD block like I was told and was sold as a standard block. Guess what! that is what this forum is for educating and selling Pontiac stuff. If you want to attack my integrity, go ahead but you should do that personally. and not hide behind a keyboard. I will always admit when I am proven wrong. I use Pontiac stuff not sell it, but when I aquire something I usually keep it or sell it as the need requires. Not that its any of your business but the guy who bought the 421 was super happy and so was i we keep in touch. As far as a pattern of scew ups, heck yeah i have had my share.

[caddor38]

Originally Posted by grandam1979

This will help, some engine codes got reused in later years.

Thanks for the info, geez i may have to pull the PHS document on this motor just for giggles. I know my name is mud here now but it would be nice to see an HO build was put in this motor, but I think that would be wishful thinking with little hope. Thanks for the time you spent looking it up.

[grandam1979]

Your block is a 71 but you asked how the 70 GTO could have that code. Codes being used more than once is how.

[n20ta2]

Gm definitely pulled parts as needed. I have a 69 YS auto gto block non ram air with 4 bolt mains. It's factory and as far as I know shouldn't be 4 bolt. My current 1969 gto has its numbers matching block YS as well, non ram air and its a 2 bolt.

[caddor38]

Originally Posted by n20ta2

Gm definitely pulled parts as needed. I have a 69 YS auto gto block non ram air with 4 bolt mains. It's factory and as far as I know shouldn't be 4 bolt. My current 1969 gto has its numbers matching block YS as well, non ram air and its a 2 bolt.

Very interesting, there should be a thread for all of these applications that devated frm spec and the norm. To bad most of those folks who worked at the plants have probably passed by now. i am sure there are some cool stories they could share. Now info is merely written and interpreted. Some have open minds and some are set in there ways and dont want this information to be revealed.

[dld]

I have read through this thread .

I bought a 455 two bolt that was taped for 4 bolt mains too. I build like the motor you built . Roller with 4.5 stroke E heads ect.

But a question I did not see asked is have you installed the 4 bolt caps on this block and checked to see if they are machined to the block noted. possibly they were just included with the block .

[caddor38]

Originally Posted by dld

I have read through this thread .

I bought a 455 two bolt that was taped for 4 bolt mains too. I build like the motor you built . Roller with 4.5 stroke E heads ect.

But a question I did not see asked is have you installed the 4 bolt caps on this block and checked to see if they are machined to the block noted. possibly they were just included with the block .

Good question, how do you check for that? Folks seem to think these were the original caps but I have no idea how to check. let me know and i will do it.

[caddor38]

Originally Posted by dld

I have read through this thread .

I bought a 455 two bolt that was taped for 4 bolt mains too. I build like the motor you built . Roller with 4.5 stroke E heads ect.

But a question I did not see asked is have you installed the 4 bolt caps on this block and checked to see if they are machined to the block noted. possibly they were just included with the block .

i have read on this forum that most pontiac 455’s were drilled with 4 bolt mains. I had asked the question whether these caps were original? I did take 3 bolts from my other 455 4 bolt to replace missing cap bolts. My primary motor was studded. If there is a way to tell i can take picture or measurements. I think many are tired of this thread but hopefully people doing searches on similar questions will get there answers after painstakingly going through the post.

[Formulabruce]

109 Posts and NOBODY has mentioned what this engine was... a... >>>> RPO L75 <<<
A friend owned a 71 Formula 455 with this engine. There were 2 formula 455 engines in 71 and this was the 'D" port version, and WAS a 4 bolt capped block when I saw it get taken apart for the first time. Not an HO though, no round ports, etc.
However just heads, and exhaust and you would be close to making one.
This engine is from a GP most likely, but a good core for a fun build.
About your caps. The bolts look correct.
To cheaply see if they are correct, you would have to carefully clean the crank bore, install bearings , lube and a crank and plastigauge if it spins well.
Other than that, you can send to machine shop, but now your eating into your profit.
I have seen a couple big car 455 blocks from 1970 with 4 bolt caps as they were same block as the 70 D port "HO"
GLWS...

[dld]

They may not align . Edges off and or the hone lines won't match . But as with my block, was drilled and tapped but was a two bolt . My block was a YC also. See date code on block

[caddor38]

Block is sold