Anyone know what the "MD" means on this Goodwrench motor?

 

Maybe for a boat engine replacement ?

 

Medium Duty?

What are you really asking? Casting numbers and stamps will tell you more than believing a VC decal.

 

per gmpartsgiant.com....

GM Part No.: 12514811

Engine Asm,Goodwrench 350 Medium Duty

 

Not finding any specs on a 350 Medium Duty motor. Does anyone know what the difference between this MD and a non MD Goodwrench 350 would be?

 

All I can think of is it might have thicker valve stems(to carry away more heat from the exhaust valves),possibly smaller valve heads.The "regular"Goodwrench 350 has 4 bolt mains and low(8.5) compression...

 

Ya know how easy it is to grab a valve cover from the junkyard with a sticker on it? Run the numbers, otherwise you're just guessing.

 

Here are the numbers from the front passenger side if the motor. Still don't match up with any numbers from sites with ID information.

 

It tells you it was a crate engine, made in the Flint plant, a production date code and a partial part number.

You can dig into that further, and you might get lucky and find the part number based on that partial. OR you could look at the CASTING NUMBERS on the block, and the cylinder heads and look them up, since there are lists of those numbers ALL OVER THE PLACE. That'll help you narrow it down, and give you a direction to look for a part number.

I know it's completely crazy to start with the numbers that are easiest to find and most general, and then to work your way down to the more obscure numbers, but it's generally a lot faster to work from big to little. Think of it like reading a tape measure. Are you going to start at the closest foot and work down to the 1/16" of an inch or are you going to start at the end of the tape and count every 1/16"?

 

Gotcha, I'll keep digging.

Thanks, Dave K.

 

https://www.mortec.com/

Casting numbers will tell you most of what you can find out. The stamp will tell you the date of production, original application, partial vin if it was part of a new car at one point.

 

Is the date August 12, 1985?
If so, does that mean 2 piece rear seal?
Should I stay away from that for a swap motor?

 

Probably best suited for use in an old 1 ton dually from the information so far not that it couldn't be made to work well in a 3rd gen with some modifications,but 'old skool"2pc rear and flat tappet cam...neither of which I have ever had any trouble with on all the SBCs I have had...the old cork pan gaskets are best replaced with 1 piece rubber design to avoid leaks though

 

It might have a four bolt main

 

Probably should have started with that question... It's easier to answer.

It's not impossible that someone stuck early heads on a late block, but GM only used perimeter bolt valve covers until 86, and the 1pc rear main started in 86, so the valve covers alone are a real good bet it's a 2pc rear main engine from the dark ages.

What are you planning on putting the engine in? If it's an 86 or newer thirdgen, a 1pc rms makes things a lot easier. The other thing to look at is dipstick location, unless you want to buy headers as part of the swap, you want and engine with the dipstick tube on the passenger's side. The other things to consider are the intake bolt patterns, if you're planning to reuse a stock intake and your old engine was 87 or later, you'll have to mod the intake bolt holes to match an older set of heads like that.

Now that's out of the way, I wouldn't want to spend time or money putting an oldschool engine in a thirdgen. There's just no logical reason not to step up to centerbolt valve covers, one piece gaskets, the roller cam, etc and as a general rule all those 87-up engines swap in better than 70's garbage and TargetMaster engines.

 

We are upgrading my sons 86 IROC from the 305 to a 350.
Had this motor in a truck that the PO said had low miles.
Think ill look at something newer.
Vortec?

 

Vortec.

 

Vortec.

Depending on which 305, it'd need an intake, headers, and potentially a work around for the lack of a mechanical fuel pump boss. Otherwise it's a bolt in upgrade, and totally worth the trouble.

 

Just by looking I'd question the "low miles" claim. Looks like a veteran of the highway. Still could be a decent motor depending on routine servicing. I'd guess a pre-vortec flat tappet two piece rear seal internal balance engine.