350’s. 1970 vs 1978

[dave6672]

I have a 67 C10, original 283 truck, that needs an engine. I have a 1978 350 I can buy or a 1970 350 that I can buy. Both equal condition and miles and both are truck engines. I would have either one of them gone through regardless. Is there any reason to pick one over the other? Any major differences between those years?

Thanks, Dave

[Warrens69GMC]

IMO the 1970 is slightly better, depending on heads.

[mattfranklin]

Similar probably. '70 may be better. Check to see which might have a forged crank. You can see the parting line of the casting or the shearing zone of the forging on the crank flange, I think. Also, the 3970010 block is preferred by racers. Either year might have that. Most of things won't matter for a mildly driven truck, though.

[dave6672]

It will a mildly driven truck for. It may be driven a lot, but not run hard.

[Accelo]

Many of the 010 blocks from around 1970 had 4 bolt mains. Very common on the truck blocks of that vintage. By 1978 there were a lot fewer around, mainly in the 1Ton and above trucks. The 1978 heads will have satellite valves. Required after the leaded fuel went away. The 78 heads will also likely have larger combustion chambers and thus a lower compression ratio.

I would use the Vortec heads from the newer SBC. Vortec cylinder heads will fit 1958 and later small block Chevy engines, and offer a 20 to 40 hp increase over earlier cast iron small block heads. Features include fast burn combustion chambers, and a high-velocity port design. They require the use of a Vortec-style intake and self-aligning rocker arms. And the biggest plus? They take a center bold style valve cover and they don't leak.
Consider purchasing a newer block. Get the newer SBC (1987-up) that comes stock with a roller camshaft and one piece crankshaft seal. It costs a lot of money to rebuild a motor why not start with one with the modern touches and the vortec heads. You will not have to worry about the dreaded flat cam syndrome if you go this route. Here I go spending other peoples money.
Cheers

[Getter-Done]

I would buy both

No Really

Yes the 1970 will have more Nickel content and Tin

(Tin is a chemical element with the symbol Sn (from Latin: stannum) and atomic number 50. Tin is a silvery-coloured metal. Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort.)

in the Block and that is why they last longer, and they are (Machine shop friendly).

[Wrenchbender Ret]

The 1970 may not have hardened valve seats.

George

[Dead Parrot]

Watch for differences in how the accessories mount. AC & Alt swapped sides after 68 and by 75. Nothing that can't be worked around if you have any needed parts already on hand.

As others have mentioned, if you are having the motor worked over anyway, might as well go to a modern head and roller cam.

[dave6672]

Thanks for all the helpful comments.

[Tom]

For a mild build they are both the same. For a stock build they are exactly the same.
I'd skip both and buy a vortec 350 from a 96-98 pickup.

[Louisvillekytruck]

The 78 has junk heads they Crack easy I think they are 624 casting numbers

[AussieinNC]

Originally Posted by Tom

For a mild build they are both the same. For a stock build they are exactly the same.
I'd skip both and buy a vortec 350 from a 96-98 pickup.

If you go looking for a Vortec, double check the starter motor bolts are intact and the block is not cracked or broken where the bolts go thru....this cracking breaking is a huge issue...also make sure the starter rear brace is in place to support the rear of the starter.

The Vortecs are a much better solution (imho) due to better oil seal controls and roller cam system by default. Plus the heads have hardened seats for unleaded fuel.