[1996thunderchicken]

Ok I am getting a 350 out of a 92 chevy g20 van it runs awsome no problems at all I am just wandering if this is a good engine to mod or not thanks in advanced for any input

[123pugsy]

Should be fine. I believe its should be set up for a roller cam already and it has the one piece rear seal on the crank which is nice.

I would guess that being a truck engine it will be a 4 bolt.

[DoubleVision]

Most cases vans and trucks got flat tappet blocks. Some got the Roller block but came with a flat tappet cam. The engine is fine to hot rod, but you won't be able to use the factory heads as they are the dreaded swirl port heads, the worst flowing heads in small block history.

[1996thunderchicken]

Why are the swirlports so bad

[ChevyTruckGuy]

Originally Posted by 1996thunderchicken

Why are the swirlports so bad

They don't flow well but where designed for torque most 4x4 guy like them for the mid range builds! Most rebuilder put a bigger intake valve! Some go in and grind off the shelf that make the air swirl. You could get a set of marine heads they don't have the shelf. With all that said most of the tbi engine builder are about 300-350hp on the stock head that have had a little work done. search e/bay you can see what there doing. Also the tuning is the most important in combo to get what you want. So you might want to go here and look around see what everyone else is doing with there truck! A few guy have video on you tube. www.fullsizechevy.com

[DoubleVision]

Why are the swirl ports so bad? Okay lets put it like this:
The straighter the port the better the flow.
While all heads violate this law, some aren't as bad as others and in some cases with a little reshaping a port with a bend can be made to flow decently.
The swirl port head really violates this law, and why is because on the swirl port heads, the port leads straight into a wall. the port runner is offset to the side of the valve so were asking the air/fuel mixture to make a sudden turn where it travels up the swirl ramp that is around the valve and comes out from around the valve with the mixture swirling for better combustion.
These heads provide explosive low end torque from high velocity, but they run out of breath by the time the engine reaches 4000 RPM.

[1996thunderchicken]

I still got 416 heads would these flow better than the swirl port heads

[DoubleVision]

Yes, 416's will flow better than the swirl ports, however you have to be careful with them. Why is because of the compression ratio. The 416 has a 58cc combustion chamber, and on a 350 with a flat top piston it puts the compression ratio quite high, even with a dish top piston. You'll be forced to run 93 octane fuel only and you'll have to very carefully set the timing.
If your engine has flat top pistons I wouldn't even attempt it as it would put the compression ratio over 10.5:1.
A 416 head that's completely stock has small valves, the intake size is 1.84 so that too limits the air flow. The 416 heads on a 350 suffers from the same problem as the swirl port head, it's out of breath by 4000 RPM.

[1996thunderchicken]

so try for 202 heads or is there a way to get the 416 heads to get from 4000 to above that mark