The Stovebolt Site Forums The Shop Area Engine Shop Swapping sbc 350 engine parts

With a little more time on my hands now, I’m finally getting to a long overdue project. The engine in my truck finally blew/ seized, and I have a used engine I’d bought a while back that I’m now swapping into the truck. I’ve pulled the engine and am now cleaning the used one up and swapping accessory parts from the blown engine to the used one before I put it in. First time I’ve done this, so I now have some questions, and likely many more to come. I’m hoping you can help me with. Both engines are 350’s, the blown one is an 80’s block, the used one I’m going to instal is a 72 block. I don’t know any more about their specs. I’m wanting to swap parts as the blown engine has some newer / nicer parts on it that I would like to use if possible.

Question 1: Harmonic Balancer swap. Well, I just learned there are 2 sizes. Should I keep the 8” that came with the used engine, or can I put on the 6” from the seized motor on?

Question 2: I was planning on swapping flywheels because the one from the seized motor is newer / cleaner. Ok to do?

Thanks.

Keep the bigger harmonic balancer on the new engine as long as the timing pointer is also included with the new one. I assume you are running a manual transmission, probably best to keep the flywheel/clutch assy. from the old set-up. Are you SURE that they are both 350's, I ask this only because all of the small blocks have interchangeable flywheels and balancers EXCEPT the small block 400 which is externally balanced with a flywheel and balancer all it's own. While you are in the process are you replacing the front and rear crankshaft seals?

Check the engine numbers on the rear of the block, drivers side of block. Go to Mortec .com and check the numbers, in the 80's the rear seal was changed to a i piece seal and the flywheels are different. As 78 buckshot said the 400 has external balanced flywheel and harmonic balancer, you don't want to put that on your engine. If you do it will shake so bad when running you will loose every dental filling in your mouth.

Here are the engine block # results from Mortec.

The wrecked engine; 10066036...350...........2 or 4...Target Master/Goodwrench crate motor, 2-piece rear
seal, "Hecho en Mexico"

And the used replacement I got. Guess its not necessarily 72 as I was told, but in the range. Says its a replacement block.
3970014....350...70-76...2 or 4

Sorry, its a flex plate, not a flywheel (showing my inexperience here), that mates to a 700R transmission. I just compared the two and they are the same size and thickness and both in good shape (teeth etc). So I guess to be sure its all balanced correctly, I'll use the same flex plate and balancer (the larger one) that came on the replacement engine. I do also have the timing pointer for the larger balancer that I will use (other one wouldn't fit anyway).

I've cleaned it up, given it a little paint touch up, and am replacing all the seals (except head gaskets of course), installing a high volume oil pump, new thermostat, oil pressure and temp sensor.

I switched the timing chain cover over as the other one was nicer chrome. It had a newer seal in it so I left it (@78buckshot, is this the crankshaft seal you mention replacing? I did use a new gasket and also black gasket maker per many youtube vids for a good seal. Sound ok?

Yes, that is a crankshaft seal, they are inexpensive and I would replace it especially if the balancer has any groove in it. Also be mindful of a high volume or high pressure oil pump, if you are not doing any head work ( valve stem seals) the increased oil may result in smoking/oil consumption. The 3970014 block should give you 100 years of more service.