Teach me to distinguish the difference between a 305 and a 350 SBC [Archive] - El Camino Central Forum : Chevrolet El Camino Forums

: Teach me to distinguish the difference between a 305 and a 350 SBC


Gert B. Frobe
04-14-2010, 11:32 PM
Hey, Guys, I'm back for some more friendly knowledge... I need to know how to visibly distinguish the difference between a 305ci and a 350ci SBC without cracking the engine open or jacking it up and crawling under it to get the casting number.

The reason I ask is because I have a sneaky suspicion that the engine currently in the Elco is a 350... I do know the motor has been swapped out because the VIN shows that it was originally a V6. I also know that the current motor has been bored out .30 over. I just don't know the original size of the motor before the rebuild.

I know it's a question that should be asked before purchasing, but somehow I just forgot about it when I was standing in front of the car...

I'm leaning more and more to the 350 side because for one, I've never heard a 305 that sounds like my car, and two because I was researching and I came across a site that said (I believe it was a camaro forum) that the oil dipstick on a 350 was on the drivers side... which mine is...

Thanks for any help in advance!

elcamino74guy
04-14-2010, 11:41 PM
The only real way to tell other than pulling the heads and measuring the bore is to find the block stampings and decode them. The dipstick can be on either side and isn't a good way to tell.
:nanawrench:

Camino-Boyz
04-14-2010, 11:45 PM
I have a 350 in my '89 Camaro and 93 Roadmaster and both dipsticks are in the passenger side . . .

Gert B. Frobe
04-14-2010, 11:52 PM
Ah, I also forgot to mention that the actual block has a sticker/badge on the bottom front driver's side that says "Remanufactured 357742"...

Maddening
04-15-2010, 12:31 AM
You need to dig around the back of the block, where it mates to the transmission, on the driver's side under your master cylinder is a number cast into the block. You might have to scrape away grime and crud to read it, but it's there. I used a digital camera to read mine since it's way back there and hard to get an eye on in some cars.

http://www.nastyz28.com/sbchevy/sblock.php

Flaminmeano
04-15-2010, 06:09 PM
Harmonic balancer is the answer your looking for, How wide and the diameter:nanawrench:

steelybill
04-15-2010, 09:27 PM
On the top of the right side of the block, just ahead of the right head, is a designator and the serial number. It's likely under the alternator or some other accessory. Lots of info around for identifying blocks and heads. Some on this site too I believe.

leogexx
04-15-2010, 09:58 PM
As steelybill stated look for the suffix code on the block in the front where the head meets the block on the passenger side usually can be seen behind the alternator. Then go to this site and click on suffix code . Suffix codes have more info than the back block numbers

http://www.73-87.com/chevy_ids/sbcid2.htm

K5Cruiser
04-15-2010, 10:34 PM
Harmonic balancer is the answer your looking for, How wide and the diameter:nanawrench:
This is the easiest way to tell them apart if you aren't able to look up casting numbers, etc. This was one of the things we always looked at when checking out the other guy's car at the street races back in the day. You definitely wanted to know if you were going up against a 305, 350, 383, or 400, and the balancer was the tell tale.

Flaminmeano
04-15-2010, 10:53 PM
Thank you K5C:beer:ruiser

Gert B. Frobe
04-15-2010, 11:12 PM
Alright, guys, thanks for the info... Just for future reference, what is the difference in size between the harmonic balancers? I believe it was 6" and 7", but I could be mistaken...

Maddening
04-16-2010, 03:32 AM
If it's a rebuild done by a large volume bulk rebuilding factory the original stamped serial number is most likely gone, and their part number/serial stamped back in it's place.

elcamino74guy
04-16-2010, 03:45 AM
I know that SBC 400 Balancers are different looking too because they're externally balanced.

Marv D
04-16-2010, 08:25 AM
You better rely on the casting # (or suffix code if it's still on the pad behind the alternator) for it's original bore size, but physically measuring the bore and stroke is the only SURE way to know 100% positive what you have. ESPECIALLY with knowing it is a reman engine,, who's to say someone didn't order a 350 short block and stuff the 305 harmonic damper and heads on it??? or... the outer ring of the damper started slipping and it was replaced with one some parts counter jockey pulled out of a computer (we all KNOW how accurate those can be http://small-block-chevy.com/images/smiles/newrant.gif ) Or one somebody had laying around their back yard.

So what do you have left??? The casting number on the block will tell you what it started life as,, a 3.736" bore of a 305 or a 4" bore of a,, 302, 327 or 350 or??? But it can't tell you what crank and pistons the re-manufacturing house stuffed in it. They are notorious for playing mix-n-match with whatever components may be laying around the shop to make up the cu. in. order may be.

old_coot
04-16-2010, 08:47 AM
You better rely on the casting # (or suffix code if it's still on the pad behind the alternator) for it's original bore size, but physically measuring the bore and stroke is the only SURE way to know 100% positive what you have. ESPECIALLY with knowing it is a reman engine,, who's to say someone didn't order a 350 short block and stuff the 305 harmonic damper and heads on it??? or... the outer ring of the damper started slipping and it was replaced with one some parts counter jockey pulled out of a computer (we all KNOW how accurate those can be http://small-block-chevy.com/images/smiles/newrant.gif ) Or one somebody had laying around their back yard.

So what do you have left??? The casting number on the block will tell you what it started life as,, a 3.736" bore of a 305 or a 4" bore of a,, 302, 327 or 350 or??? But it can't tell you what crank and pistons the re-manufacturing house stuffed in it. They are notorious for playing mix-n-match with whatever components may be laying around the shop to make up the cu. in. order may be.

There's some gospel in there somewhere...you may want to take note of what he just said....:beer: Marv for President......................Dan

Marv D
04-16-2010, 08:59 AM
LOL, just stating the obvious Dan,, after 50+ years of the backyard rebuilder and the reman houses playing mix and match,,, it's a crap shoot at best to have anything 'completely original'

and as far as Prez,,, I'll remind you of a phrase from a song from 'our' time


He can't even run his own life I'll be damd if he'll run mine!! http://small-block-chevy.com/images/smiles/whacky.gif


Now that I've finished my http://small-block-chevy.com/images/smiles/coffee.gif Better get back to work!

Gert B. Frobe
04-16-2010, 10:33 AM
Thanks for the info Marv... I'll check to see if the suffix code is still there, but I guess like you said the only true way to know is to take the heads off and measure...

If I can't find the suffix code, I'll just go on pretending that I have a 350 bored .30 over until I can verify it for sure...lol

BTW, do you think that any of you guys could tell the difference by hearing the sound of the engine/exhaust???

theelcaminofactory
04-16-2010, 11:07 AM
BTW, do you think that any of you guys could tell the difference by hearing the sound of the engine/exhaust???No you could have two identically built smallblocks and they could sound different because of the mufflers/exhaust used. I've also heard a 305 in an M80 Malibu that made my eyes :eek3: pop out of my head because of the way it sounded...I swore the guy had a big block until he showed me it wasn't...once again it was the exhaust system used.

Gert B. Frobe
04-16-2010, 11:33 AM
Well, I thought I'd update you guys with the information I have just found out... It's seriously got me giggling like a schoolgirl...

I wiped some grime off of the block casting by the master cylinder and ran the code on the site Maddening gave me... The code is "3970010" which from what I can tell it is a 350... I know since it's a reman. engine that the short block may have been mix-n-matched, but it's definately a 350 block... technically if nothing was changed then I have something similar to a 383 stroker in the Elco...

WOOT WOOT!!!! :beer:

Thanks for helping me out guys... This really makes my day!!! :You_Rock:

Marv D
04-16-2010, 12:05 PM
3970010 is about the most common 4" bore block. They were cast from 69 all the way through the 80's and are a SOLID foundation for a performance build. MANY were 4bolt mains and I'd go on assuming it's a 350. That's the most common. I mean if you have a 4" bore, why not make it a 350. 302's and 327's just do not make sense any more unless your trying to do something 'particular' (class limits or original engine or something)

As far as being 'something similar' to a 383, ummmmm No. You have a 355 (assuming a +.030 350) It would take a totally different crank, different pistons and a buttload of clearancing to make it the 3.75" stroke of a 383.

And like theelcaminofactory explained,, NO WAY can you anything about size from the sweet music the exhaust makes. There are some Comp Eliminator 300 Cu In motors that make my 13.6:1 797HP 434 small block sound like a ***** cat purring. Sound is a function of compression and cam timing much more than ANYthing else.

Gert B. Frobe
04-16-2010, 01:05 PM
Thanks for the info Marv... I'm still VERY happy that I have a 350 'cause this means there is a s**tton of performance options out there. I'm sure they'll keep me occupied until I can scrape together enough cash to build the Dart SHP that I want.

Again, thanks for the advice! :beer:

americanhandy
04-16-2010, 03:15 PM
There's some gospel in there somewhere...you may want to take note of what he just said....:beer: Marv for President......................Dan
I second that.