327 or 350

[rico7769]

Does anyone know how to identify the diff between a 350 and 327? My casting numbers are 3970010 w/ the other identifying #'s being 5 G 7. I understand the info, but am unsure of the block size. It was put in a 67 GMC CST before I bought the truck. It would make a diff in the horsepower rating we are looking to achieve if it is a 77 and not a 67. Any help would be appreciated. We haven't checked the heads for #'s yet. We are running a perf. intake, holley 4bbl 650cfm, accel hei system, accel 8mm wires, and perf. headers. I am also curious about the HP. If it is 67 it will be greatly diff from 77.

Thanks

[68GMCCustom]

That's the same block I have. It's an early 70's sbc performance block with 4 bolt mains, and with the high nickel content. I'm sure it was used for 350's...not sure about 327's.

[Gray Ghost]

Depends on where you read about it. according to Mortec, 327's had a one year date with that block code. In the Chevy V8 casting numbers 1955-1993' book only 350's and 302's had that number.

Mortec says '69-'80 for the 010 block as a 350. I've never seen a 327 with that code so I don't know.

[breeh]

Did you look up the suffix code stamped in front of the passenger side head? Also, 010 blocks do not always have 4 bolt mains.

[Gray Ghost]

Two good points....most were actually 2 bolts, but that's not a bad thing at all. The suffix code will help a ton.

[breeh]

You can look up the suffix code here:

http://www.nastyz28.com/chevy-engine-code-stampings.php

[68GMCCustom]

I've heard of that block number coming up as a 327 also...but I never heard of it with 2 bolt mains. We talking about the same 3970010 high nickel content "performance block"?

Learn something new everyday I guess.

[rico7769]

Motor has been repainted and rebuilt recently so it appears the codes on the pass head (front if I'm correct) have been cleaned or painted over. Very difficult to get to w/ the water pump in the way, too. We plan on changing out the valve covers soon and will check the #'s on the head then. Maybe that will lend some info. About the high nickel block, not too sure how early it is. If the numbers G 5 7 are correct it would lend to a 77 w/ a phenominal......180hp-yeah.

[rico7769]

Also tried to find the date codes on the front, but it appears the the engine has been decked and I've read that decking can remove the numbers. Don't know how reputable the source was though. Just found it tooling around a diff. website.

[elkynova]

the 3970010 block is a 350 in both 2 and 4 bolt used through 84. Used in passenger and truck lines, both low and high performance.

[sweet70beast]

Originally Posted by breeh

Also, 010 blocks do not always have 4 bolt mains.

60s-mid 70s most were 4 bolts, mid70s- 80s most were 2 bolts. I had a 83 Suburban years ago with a 2 bolt 010 block.

[breeh]

Originally Posted by sweet70beast

60s-mid 70s most were 4 bolts, mid70s- 80s most were 2 bolts. I had a 83 Suburban years ago with a 2 bolt 010 block.

Hmmm, that has not been my experience. Especially with these trucks. All of the 2wd 1/2 and 3/4 ton trucks that I have had with that block had 2 bolt mains. For some reason the 4x4's seem to have the 4 bolt mains.

I also play with early 2nd gen Camaro's and most of those 010 blocks have 2 bolt mains as well. Maybe it is regional?

[Gray Ghost]

010's were factory blocks only up until 1980 according to Mortec.

[special-K]

Nasty Z28 doesn`t list my suffix code and I can`t even find suffix codes at all on Mortec.
My`68 327 block casting# is the same as 302 & 350 in`68.My suffix code is VI0I8YH.It`s fresh rebuilt and clean as a whistle on a stand.There is no mistaking the digits.They are perfectly clear.Any tips on finding suffix codes on Mortec?

[special-K]

...Or anywhere else?

[red69ss]

special-k according to one of my engine id books ths YH stands for 1966 model 327 220 hp ,4 bolt used in c-30 or the more likely fit 1967-68 327 220 hp ,4 bolt used in c-10 thru c-35 heres a link to nasty z28 they got there info from mortec http://www.nastyz28.com/sbchevy/sblock.php

[67slammer]

my engine casting numbers are 3932386 which i found to be 69 camero and they used that same casting number for the 302 327 and the 350 the 327 was a two bolt main.

[Lugnut64052]

Originally Posted by elkynova

the 3970010 block is a 350 in both 2 and 4 bolt used through 84. Used in passenger and truck lines, both low and high performance.

It's a four-inch, large journal block, and a very common one. I've seen just as many 2-bolt ones as 4-bolt ones with that block number. If it was in a passenger car, a lot of them were 2-bolts, if in a heavier truck (3/4 ton and up) they were usually 4-bolt.

The only way to tell for sure whether it's a 350 or a 327 is to pull a head and measure the stroke length. At this late date original, un-rebuilt engines are fairly scarce. Chances are it's been apart and been rebuilt at some point and if so, all bets are off. Probably a 99% chance it's a 350. There are large journal 327 cranks out there, but they're pretty scarce.

As for power ratings, it all depends on what's in it (cam, heads, etc.) All you know for sure at this point is that it's a 4-inch block.

[special-K]

The 010 blocks can be bored 40 over.They are the best rebuild candidate.Mine isn`t an 010.It came out of a`68 CST/20 and I opened it up for the 1st time.The six says it`s a`67 according to NastyZ28.It`s a large journal.

[ChevLoRay]

Okay, this casting number....where is it located? My engine is on a stand and I know that it is the "numbers-matching" engine for my truck, per the coding on the right side of the block on the machined part....i.e., it has not been decked.

I just haven't gone to the trouble to look for it, yet....it's cold in the garage.