This is for my future swap to ported Vortec heads. Sent out my 906 castings to get professionally ported. Luckily I know a person that enjoys doing this kind of work. Got the flow bench numbers back tonight from him. At .500" lift they flow 257 CFM on the intake and 224 CFM on the exhaust. Will be running a ZZ4 cam with 1.6:1 roller rockers. The intake lift is .505" and the exhaust will be .544". I have the feeling this thing is going to run.

Will put pictures up as soon as I get them back, early next week.

Attached are some pictures of the untouched castings on the junk 350 Vortec. Has a rod hanging out of the passenger side of the block.

 

Looks like you got monster gains on the exhaust, more modest gains on the intake. Not all that surprising. But amazing, given the big difference in valve size, isn't it?

Single pattern cam would probably be the best choice, IMHO. I'm sure it'll run good with the ZZ4 cam but probably run better with something aftermarket in the 220/220 range.

 

Definately agree there

Plan on keeping the ZZ4 cam for two reasons.

A.)Already own it and it already resides in the engine

B.)Should make very streetable power over a wide RPM band. As another benifit it has a 112* LSA which will help keep the vacuum for the accessory setup.

 

224 cfm on the exhaust.... That's incredible. What size valves you using???

 

1.94/1.55

I'll see if I can get the flowbench paperwork when I get them back

Actually I have had 3 different head castings with 1.5" valves that flowed 224 on the exhaust. Crazy. Wonder if that is some barrier to flow with the 1.5" valve.

 

What's a single pattern cam?

 

A single pattern cam has the same specs on the intake and exhaust, lift, duration are identical, a dual pattern has a larger exhaust grind usually for smaller heads to make up for lack of exhaust flow, i always use dual pattern no matter what, thats just me though, i have seen 275 on the intake side with 1.94s, i did mine myself, if i ever flow bench them i will post my home porting results, i am pretty serious about my work and the effort i put into my craftsmanship, i took two solid days to do my castings and am very curious about my flow #s, they are on the 383 now and it has 50 miles on it and started nocking today for some reason, i assume a spun bearing, if it is not a quick fix, i may have them benched, wish me luck.

 

Which intake manifold will you be using? Keeping the TBI set up or carb?

 

I will NEVER own another vehicle with a carb, if that answers your question.

 

Hehehehe. Maybe a little over scavenging in your future. The ZZ4 cam sports a 208/221 intake exhaust spread and the heads flow 224cfm on the exhaust. I do see a big exhaust bias.

 

Maybe

1 3/4" primary headers and 2 1/2" duals too. I have cats and mildly restrictive mufflers to keep it legal and quiet though, so it may not be too bad.

 

Trying to decide whether or not to drop in the HT383 roller cam with the 1.6:1 rockers or keep the ZZ4 with the 1.5:1s.

 

Those are some impressive numbers. Better than my Trickflows.