The 73K lb9 in my '86 Iroc is dying a slow death and I'm going to put it out of it's misery. I don't have much spare change right now, so I want to build a 350 for the car with parts that I already have laying around. The 350 is a 2bolt main, non-roller from a '91 Chevy truck that ran well.
I have the choice of the stock swirl ports, '71-'72 LT-1 heads (large chamber) that look like they should be reconditioned, or a set of late 70's 305 heads that could use new valve seals but have been ported. Which would be the better choice for best street performance?
I'm not willing to spend a ton of money building this thing up for power because I already did that on my other '86. I just want better-than-stock performance and for it not to kill the 5-speed I'm going to put behind it.

 

Freshen up the LB9 heads.

 

use the 71 lt-1 heads. they are bad ***. those were the fastest camaro's ever produced! freshen them up and you will have a peppy little mouse motor

 

You mean the original heads to the car, right? There is a good possiblity that one of them is cracked. I also wanted to have the complete long block ready to go before I pull the stock motor.

What concerns me is the 76cc chamber. I don't know what size the chamber is on the stock heads, Mortec doesn't list it. I didn't want to end up with like 8:1 compression or something.

 

Any more input... pretty please?

 

Agree with Five7... the LB9 heads are the best ones of the choices you listed. The large chamber LT1 heads really aren't anything special, they just had a little extra machining done at the factory (screw-in studs and guideplates) which is cheap to have done on your LB9 heads. Otherwise they aren't much different than any other smog era heads from the '70s.

The LB9 heads have smaller chambers, very similar to the good double hump heads from the '60s (which does NOT includes the large chamber LT1 heads) and actually flow fairly well in stock form if you just increase the valve size to 1.94/1.60.

If theres a problem with them, find out what castings the other 305 heads are. If they are 601, then they are even better ones than your LB9 heads.

 

I don't remember the casting # on them, I did look them up on mortec a few years ago though. I believe they were listed as '78-'80 heads. I guess I should dig them out and look. They were on my other 350, and it felt pretty strong other than off the line (I believe that was due to other minor issues).