I am swapping from a TPI to carb setup. Currently is a 350 w/ vortec heads 7/16 screw in studs, comp magnum 1.6rr, LT4 Hot cam. I am looking at a rpm air gap, keeping the vortecs, 670 street avenger carb. Should I keep the hot cam or switch. I have searched and it seems that alot of people suggest the xe274... I would like to get as close as possible to 400hp at the crank.

 

With the Hot cam you should have close to 400 hp

Have the heads ported and you should hit 400+ hp

On the other hand, you could go with a little bigger of a cam and reach 400 hp

I Say you drive it first, and if it is not enough. Choose one of the options above and go from there

FWIW, I had a set of my ported vortec heads and one of my cams in a customer’s car put down 428 RWHP..... Cam was in the mid 230's

 

I'd say don't use that carb, just go for a run of the mill Holley 650 mechanical secondary. I had a 670 Avenger and never got that thing to run good enough for my liking. And before you get your panties in a bunch over a mechanical secondary carb drinking a lot more fuel... You're going to be driving on the primaries most of the time anyway just like a vacuum secondary carb. You'll be able to feel when you're about to tip into the secondaries. Also, if you do end up with 400 hp, you're not going to be flooring it everywhere you go during normal driving. You'll probably end up spinning your tires even at half throttle.

 

I've heard nothing but good things about the LT4 spec cam on the street; you should be okay with that one.

Just a side question, did you have your valve guides cut down for more lift? I thought the LT4 cam had enough lift to smash the top of the guides...

 

I would not run the 274. I think the hot cam would be so much better for street driving. You should be close to 400hp with that cam.I would get a different carb though.650-750dp but that carb could still work and make sure you have a stall speed of 2,500 plus for launching.I would run the 274 in a 383 or 400 if it was my daily driver.
Also the xe 274 is a hydraulic cam and the LT-4 hot cam is hydraulic roller.The hot cam will have a noticeable idle but nothing serious.The LT-4 is more of a sleeper cam it has a 112 lobe seperation.If you wanted more of a lope to the motor run a comp cams XR276HR-10. This has a 224 230 dur. and a 502 510 lift with a 110 lobe seperation. The hot cam will rev alot higher than this cam but this comp cam will sound meaner.