3970010… but it’s a 305?!?!

[Island’r]

So; my 71 C10 had the original 307 swapped out by the previous owner. He disclosed that it was a freshened up 305 believed to be from an ‘82 Camaro.

However; it has the 3970010 casting number on the rear of the block.

Engine suffix code stamped on the pad behind the alternator says C2R, which comes up as an ‘82 4bbl 305 with a whopping 155hp. (Which fits what he stated)


Aside from pulling the heads and measuring the bore… is there any other ID marks to figure out what this thing really is?!?!

[geezer#99]

C2R.
No suffix codes I’ve seen had a 2 in them.
Post a pic of the pad.
And good morning to you from Bowser!

[Island’r]

Originally Posted by geezer#99

C2R.
No suffix codes I’ve seen had a 2 in them.
Post a pic of the pad.
And good morning to you from Bowser!

Good morning from sunny Qualicum! I’m positive it’s a 2 unless my eyes are really failing me!

https://ibb.co/h8XR38b

[geezer#99]

First I’ve seen like that.
And a split in the date code too.
Could be a restamp.
Are the valve covers center bolt?

[geezer#99]

Further research does indeed show a C2R as a 305. I missed it somehow.
Any other letters or numbers on the pad?

[Island’r]

Originally Posted by geezer#99

First I’ve seen like that.
And a split in the date code too.
Could be a restamp.
Are the valve covers center bolt?

It’s a bit of an odd one eh?

No, they are not Center bolt.

[Island’r]

Originally Posted by geezer#99

Further research does indeed show a C2R as a 305. I missed it somehow.
Any other letters or numbers on the pad?

No other markings on the pad at all.

[geezer#99]

I suspect a restamp.
Unless you read the casting number wrong.
3970020 is a 307.

[Island’r]

Originally Posted by geezer#99

I suspect a restamp.
Unless you read the casting number wrong.
3970020 is a 307.

I’m going to try and see if I can see the casting date on the back of the block tonight. Might help narrow it down.

It’s definitely 010 and not a 307

I should’ve sent you this earlier… I wasn’t thinking!

https://youtu.be/43A5hBi93YI

[geezer#99]

Ford guy eh!
That might explain your heater hoses being hooked up wrong!
Good looking motor!

[Island’r]

Originally Posted by geezer#99

Ford guy eh!
That might explain your heater hoses being hooked up wrong!
Good looking motor!

Heyyyy… good catch! This truck was a “bit” of a basket case when I got it.

It was previously owned by a bodyman and you know the old saying: “most mechanics aren’t good bodymen, and most bodymen aren’t good mechanics”

Body was fairly well done, and had fresh paint, but the mechanical side of things was something to be desired.

For example; The front brake hoses were routed so that they were rubbing on the control arms and had nearly worn through. The rear brake hose was right tight to the cobbled together exhaust… the solution; wrap it with crumpled up foil tape and zip ties.

The heater hoses being backwards never even crossed my mind. I only drive the truck on hot sunny days so I’ve never even turned the heater on lol. Not surprised. It’s just being back flushed… permanently hahaha.

And hey… I might be a Ford guy at heart, but I’ve owned a equal amount of Chevys. I usually say; I’m not a Ford guy OR a Chevy guy. I’m a “Car Guy” through and through… I love ‘em all!

[geezer#99]

Same here.
Just an old car guy.
Owned a lot of different stuff in my 70 years.
First hi per motor I worked on was a sohc 427.
Some crossbreeds too.
Poncho 455 in a 64 Ford F-250 for one example.

You Might need to pull a head to finally figure out exactly what you have.

[AussieinNC]

As far as I know, and I may be wrong....

3970010....302 cu in.....69 Year ....4 bolt main...Z-28 Camaro
3970010....327cu in.....69 Year....2 bolt main...Trucks and industrial
3970010....350cu in...69-80 years...2 bolt or 4 bolt main

Are you sure the stamp code is C2R and not CR2...CR2 was a 1975 350 used in Chevelles....

[mattfranklin]

My 3970010 is definitely a 350, but when it was cast, I think a chunk of loose sand dropped on the numbers so they have more texture than most. Readable, bit not super clear. I guess there is a risk that the internals of my block might have similar housekeeping issues. I once saw a 3970010 block at a racing machine shop and those numbers were as clear and clean I've ever seen. Maybe clean numbers is one more thing to add to the list of things like core shift when looking for a good block?

EDIT1: So, your block numbers are cleaner than mine and clearly a 3970010. 350, 327, or 302, like Aussie shared.

EDIT2: Beautiful truck, BTW!

[mongocanfly]

I'm with what Matt and Aussie said....
I also know Keith said GM recycled numbers over the yrs on some things..
also could it being Canadian make it different from US?

[mongocanfly]

Found this

[Island’r]

…

Originally Posted by geezer#99

Same here.
Just an old car guy.
Owned a lot of different stuff in my 70 years.
First hi per motor I worked on was a sohc 427.
Some crossbreeds too.
Poncho 455 in a 64 Ford F-250 for one example.

You Might need to pull a head to finally figure out exactly what you have.

Very cool Geezer! Those 427’s were monsters!

Originally Posted by AussieinNC

As far as I know, and I may be wrong....

3970010....302 cu in.....69 Year ....4 bolt main...Z-28 Camaro
3970010....327cu in.....69 Year....2 bolt main...Trucks and industrial
3970010....350cu in...69-80 years...2 bolt or 4 bolt main

Are you sure the stamp code is C2R and not CR2...CR2 was a 1975 350 used in Chevelles....

100% positive it’s C2R!

Originally Posted by mattfranklin

My 3970010 is definitely a 350, but when it was cast, I think a chunk of loose sand dropped on the numbers so they have more texture than most. Readable, bit not super clear. I guess there is a risk that the internals of my block might have similar housekeeping issues. I once saw a 3970010 block at a racing machine shop and those numbers were as clear and clean I've ever seen. Maybe clean numbers is one more thing to add to the list of things like core shift when looking for a good block?

EDIT1: So, your block numbers are cleaner than mine and clearly a 3970010. 350, 327, or 302, like Aussie shared.

EDIT2: Beautiful truck, BTW!

Well that would be great news for me!

And thank you sir, she’s a fun cruiser!

Originally Posted by mongocanfly

I'm with what Matt and Aussie said....
I also know Keith said GM recycled numbers over the yrs on some things..
also could it being Canadian make it different from US?

Originally Posted by mongocanfly

Found this

I have just learned that they did indeed recycle numbers, but I’ve not found that suffix referenced anywhere else. If the 3070010 is the hard fast ID, then I lucked out!

My thought last night; if I pull a valve cover and check the casting number on the heads… that might give me another clue. This isn’t 100% either as guys have been known to put 305 heads on 350’s… but if my 3970010 also has heads with 350 casting numbers, I think o can confidently say it’s a 350.

Thanks everyone for your info and thoughts!!!

[geezer#99]

I read on nastyz28 (can’t find it now)that above all else the casting number always trumps anything found on the pad behind the alternator.
Casting number is hard to alter. Stuff on the pad can be wiped clean decking the block.

[Island’r]

Originally Posted by geezer#99

I read on nastyz28 (can’t find it now)that above all else the casting number always trumps anything found on the pad behind the alternator.
Casting number is hard to alter. Stuff on the pad can be wiped clean decking the block.

That certainly makes sense. This engine was indeed gone through at some point, so it’s very possible they wiped the original stamp when they decked it. The spacing of the date/suffix code that you pointed out definitely seems to be an anomaly as well.

Perhaps it was restamped by someone having a dyslexic moment at the machine shop. As Aussie pointed out; if it was CR2 that would make a heck of a lot more sense.

If I could find the date stamp on the block we would be sure! But some silly enginerd decided to put the damn distributor at the wrong end of the engine… right in the way! 😂

[geezer#99]

Take a pic with your phone. Several in fact.
Or use a flashlight and a mirror. Angle the mirror back there and point the light into the mirror. The whole area will light right up.
I have a mirror that I sneak out of the wife’s stuff for that purpose. lOL!

[Warrens69GMC]

Maybe Canada has different suffix codes?

[geezer#99]

Originally Posted by Warrens69GMC

Maybe Canada has different suffix codes?

They’re in metric!

[Island’r]

Originally Posted by geezer#99

Take a pic with your phone. Several in fact.
Or use a flashlight and a mirror. Angle the mirror back there and point the light into the mirror. The whole area will light right up.
I have a mirror that I sneak out of the wife’s stuff for that purpose. lOL!

I actually did both of those things! Nothing up along the rear of the block, other than the casting number itself. There is a raised square with a large “2” next to that, but nothing else.

I do see a whole bunch of casting numbers on the right side of the block, but the block hugger headers which are on it hide 90% of the numbers. I will be pulling the block huggers this winter to install some full length headers, so we shall see what they are when that time comes.

[cadillac_al]

There never was any such thing as a 305 with an 010 block.

[Warrens69GMC]

Originally Posted by cadillac_al

There never was any such thing as a 305 with an 010 block.

That is why this thread is here.