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Old 01-25-2010, 01:41 PM
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'81 Chevy C30 dually "M" code 350 question

I know I can drop the oil pan to find out but, I was wondering if anyone knew if this engine code, "M" HEAVY DUTY 350, was the same 4bolt main used in the C60/70 trucks?

BTW, I'm starting a frame off on this truck. It only has 56k original miles on it so I'm STILL trying to decide if I want/need to go through this engine or not. I can always pull it back out if the need arises.

PLEASE, feel free to tell me what you think I should do.

***This is the FIRST forum that I can allow my 8 year old, (car and truck lovin'), daughter read without running across a bunch of cussin' and carryin' on.

I thank you for keeping this forum clean and hope I can contribute something.

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Old 01-25-2010, 02:16 PM
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If originality is a concern, as in, 'numbers matching' stuff, then hang onto the engine. No bad noises, smoke, leakage, roll with it. The '4 bolt main' is really not a big deal. I doubt it would have a steel crank either, like the OLD truck engines.

If you want to play, go big block.

If you want to be 'trendy' go diesel.

If you want to be 'retro-diesel' go 6.2 GM diesel. OR even the 6.5 turbo diesel. You'll get laughed at by most, but at least your diesel truck will still be ALL GM.

Last edited by C-10; 01-25-2010 at 02:21 PM.
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Old 01-25-2010, 02:46 PM
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I'm into the Ford performance diesel stuff as well. So, that did cross my mind, stuffin' a powerstroke down in it. I would have to totally redo the front end because of all of the "crap" and weight becomes an issue as well. So, probably not.

I really want to keep this truck fairly original, maybe upgrade the stereo and instrument cluster and the paint will be far from stock as well.

The engine has no leaks, uses no oil, no smoke, nothing wrong really. Heck, I've been driving it around a fair amount, 3k miles worth. Those bias tires are soemthing new for me, LOL! They're fairly new tires but, man alive on these cold mornings I have to wear a helmet to keep from hittin' the cab!
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Old 01-25-2010, 03:00 PM
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First I would like to welcome you to the forum always nice having new people here.

I've done as much digging as I could and all I find are 3, 350 Engine Options for the 1981 model year trucks.

L - 350 V8 - Commonly Found in C&K 10 and 20 Series Pickups
M - 350 V8 HD - Commonly Found in C&K 20 and 30 Series Pickups
N - 350 V8 Diesel - Unknown

Now in 1981 the 17 Digit Vin # came into play in which case the 8th digit if I remember Correctly is the Engine Code. I've Also Found the Following Coded 350's Available for the C60's in 1981

8th digit G
8th digit A

Differences between the M, G and A blocks are Unknown to me hope this helps at least a little bit, but chances are if the G and A blocks are Gasoline and Non-Diesel, the 4 bolt in them will be the same as ur M block, GM usually changes Heads, Cam, intake, Etc rather then block designs.

My Expertise is 13 Years older in the 1968 Chevy Trucks lol
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Old 01-25-2010, 03:13 PM
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I wouldn`t rebuild it if it only has so little miles on it. What I would do is install a edelbrock performer plus cam, or the summit eqiv. Which has .204 In.
.214 Ex. Duration figures @.050. Add a double roller timing chain. Replace the smogger heads with a set of Vortecs and a Edelbrock performer Vortec intake. retain the Quadrajet carb. Add a pertronix flame thrower coil and module, moroso blue max spiral core wires, take the time to route them correctly. Small tube headers, dual exhaust with crossover pipe and turbo mufflers. Lastly add a K&N air filter. These small mods will kick up the torque by about a 100 more ft. lbs. The truck will have very sensitive throttle response, so sensitive you`ll swear it`s fuel injected. It will make it a pleasure to drive. Another added benefit is it will get better miles per gallon.
On another note, these trucks came with 4 bolt main blocks, but as mentioned, that`s really not important. It may have possibly came with a steel crank, as some of the heavy duty engines did. This is easy to check, if the parting line on the crank is wide, it`s a steel crank, if it`s narrow, it`s a cast iron crank.
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Old 01-25-2010, 03:52 PM
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Quote:
Originally Posted by Smoked Rubber
First I would like to welcome you to the forum always nice having new people here.

I've done as much digging as I could and all I find are 3, 350 Engine Options for the 1981 model year trucks.

L - 350 V8 - Commonly Found in C&K 10 and 20 Series Pickups
M - 350 V8 HD - Commonly Found in C&K 20 and 30 Series Pickups
N - 350 V8 Diesel - Unknown

Now in 1981 the 17 Digit Vin # came into play in which case the 8th digit if I remember Correctly is the Engine Code. I've Also Found the Following Coded 350's Available for the C60's in 1981

8th digit G
8th digit A

Differences between the M, G and A blocks are Unknown to me hope this helps at least a little bit, but chances are if the G and A blocks are Gasoline and Non-Diesel, the 4 bolt in them will be the same as ur M block, GM usually changes Heads, Cam, intake, Etc rather then block designs.

My Expertise is 13 Years older in the 1968 Chevy Trucks lol
I'm assuming that it's the same by some online references...??? Still not for sure but, I think I'm in the safe range for ordering any parts I may need with what info you gave me and what I've found.
Thanks so much!
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Old 01-25-2010, 05:14 PM
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Quote:
Originally Posted by DoubleVision
I wouldn`t rebuild it if it only has so little miles on it. What I would do is install a edelbrock performer plus cam, or the summit eqiv. Which has .204 In.
.214 Ex. Duration figures @.050. Add a double roller timing chain. Replace the smogger heads with a set of Vortecs and a Edelbrock performer Vortec intake. retain the Quadrajet carb. Add a pertronix flame thrower coil and module, moroso blue max spiral core wires, take the time to route them correctly. Small tube headers, dual exhaust with crossover pipe and turbo mufflers. Lastly add a K&N air filter. These small mods will kick up the torque by about a 100 more ft. lbs. The truck will have very sensitive throttle response, so sensitive you`ll swear it`s fuel injected. It will make it a pleasure to drive. Another added benefit is it will get better miles per gallon.
On another note, these trucks came with 4 bolt main blocks, but as mentioned, that`s really not important. It may have possibly came with a steel crank, as some of the heavy duty engines did. This is easy to check, if the parting line on the crank is wide, it`s a steel crank, if it`s narrow, it`s a cast iron crank.
That's a little more than I plan on doing at this point. I DO APPRECIATE and WROTE DOWN the combination you listed in case I get a burr up my behind later on.

Would you reccomend a "towing" cam for this truck?
- 4spd manual trans and 4.10 gears 2 wheel drive
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Old 01-25-2010, 05:18 PM
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Yeah that info came from books and Online References, and I only posted what I saw come up numerous times Good luck with your Project, the M engine Code block is the LT9 Block.


RPO FY CID appl VIN HP BBLS Body/Comments
UHW 1981 350 con cab, m/t, A.I.R. M LT9 165 4 C-20 to 3500
UHX 1981 350 con cab, a/t, A.I.R. M LT9 165 4 C-20 to 3500
UHY 1981 350 con, m/t, A.I.R., Cal M LT9 165 4 C-20 to 3500
UHZ 1981 350 con, a/t, A.I.R., Cal M LT9 165 4 C-20 to 3500

Source for Graph: http://www.nastyz28.com/gm-chevy-cod...s-suffix-9.php

This Engine was produced from 1980 - 1989 in 86' Gm moved to the 1 piece rear main seals so your block should have a 2 Piece rear main seal.

http://www.gmgoodwrench.com/_res/pdf...RPO%20List.pdf Page 4 Upper Right Corner Lists the production period of your engine

I had a Spec sheet from the local GM dealer on the LM1 and LT9 Engines, Its lost somewhere in my Trucks mountain of Information.

Also GM has a Current Production Engine made as a Universal replacement for this its the Goodwrench 350 engine part # 10067353 Hope this Helps, and good luck with whatever you plan on doing with it later.

10067353 Engine info: http://www.sallee-chevrolet.com/Chev...V8s/gen350.cfm

Last edited by Smoked Rubber; 01-25-2010 at 05:23 PM.
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Old 04-13-2013, 09:53 AM
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SBC 350 vin code M

Well it's like this ... pop a head and you'll think that you're lookin at a 400 because the heads and block are drilled with additional holes identical to the holes of a 400 block and heads for extra water jacket flow. I found one in my 1985 Chevy P35 Grumman Van.
350 ci block casting GM 14010207
HD Truck with only double AIR emissions pumps
heads casting GM 462624
transmission GM TH400
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