2bbl to 4bbl guidance please
 

1968 C10, 327. I have been led to believe that the motor is original...now I’m doubting it. Block is 3914678, MA suffix. This returns to a ‘68 from a car, with a manual trans? (Truck is AT) The heads are 3973478, J141 date code. This points to a early 70s 350? It does have the 5/8” spark plugs. Plausible that early in its life it received a head swap/valve job(?). Current 2bbl manifold is 3919801. At issue is...trying to decide if I should remove the current 2bbl and swap on a 4 bbl...only because the current 2bbl is trash, a cleaning and rebuild didn’t help much. Thought about switching to a 4bbl but only if the heads will support it and if it nets any performance and driveability gains. Or just buy a quality rebuilt Rochy 2bbl. Thoughts?

Re: 2bbl to 4bbl guidance please
 

I would just buy a quality rebuilt 2 barrel unless you have additional plans for mods to the engine.

The two barrel and 4 barrel heads are mostly the same. Cam is as well most likely.

If you are going to swap on a free-flowing exhaust and do a cam swap, a Q-jet and 4 barrel intake will certainly help add to the package. But just swapping to the 4 barrel isn't going to make much difference and it's all going to be above 4000 rpm.

Re: 2bbl to 4bbl guidance please
 

That motor codes out, as you mentioned to a '68 327....car engine.
Nothing wrong with that and usually higher hp than the truck 327's.
The heads tho'....I think the number on the heads should end with the suffix 487 instead of 478.....I've never heard of a 478 head but the 487's are a good head and yes...they definitely support a quadrajet 4 bbl. and if they are in good condition leave them on and keep going.
As well, I'm pretty sure the 487's were only installed on the 4 barrel engines due to their larger valves (1.94 and 2.02).
They were used on a lot of vehicles including the odd truck up to a '71 350 LT1 engine so they will work better with a 4 barrel than a 2 barrel.

my two bits.
Coley

Re: 2bbl to 4bbl guidance please
 

You are correct...they are 487s, I transposed the #s. I know they were not the correct heads when I attempted to change the plugs. I think I will go 4bbl, since the 2bbl is trash and it needs a new air cleaner too. And yes...the heads spec out as supporting a 4bbl. I bought this thing thinking it wasbab307 but this combo is much better :-). Has ram style exhaust too...with an old school 2” duals and glasspacks

Re: 2bbl to 4bbl guidance please
 

Is it your carb or is it really the state of your tune?
99% of suspected carb problems are timing problems.
What are the symptoms?
What distributor do you have?

Maybe an ignition upgrade will cure your ‘carb’ problem.

Re: 2bbl to 4bbl guidance please
 

Yes...I’m basically resurecting an engine/truck that has been asleep for 10 years. Dist was a mess...cap/points/wires. Got it running just barely, though it did run. Swapped to HEI (new) and MUCH improved. The issue with the carb is sloppy throttle shafts and it appears to be leaking internally. It looks like a chain store rebuild. The truck runs good above idle but at idle it runs rich/rough.
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Re: 2bbl to 4bbl guidance please
 

I would get a remanufactured Quadrajet from National Carburetor. You can find them on Amazon at really good prices, and they tend to run well right out of the box. You'll be much happier with the Quad. Get a decent dual-plane manifold and you're set.

Re: 2bbl to 4bbl guidance please
 

What’s your initial timing?

Re: 2bbl to 4bbl guidance please
 

Man, a 350 holley would be awesome.