I have been wondering about trying some different heads on my new 440 short block. The factory heads are a 2.02-1.625. I can get some aftermarket aluminum heads that have not had the seats installed. There is a nice CNC porting program for them already and I am thinking of changing the valve sizes to favor the exhaust for the turbo's. What do you guys think about using something like a 1.94-1.80 valve sizes? My cam is 224-224 with .575-.573 on a 113 LSA.

 

Dave at Hughes Engines has just received the bare un-machined Edlbrock heads. He is figuring out the max exhaust valve size without the intake valve taking a bit hit. They have a CNC porting program for this head which will be modified to take more advantage on the exhaust side. I expect to see some great flow data.

 

I port mine the same way as I would for NA. I try to maintain good mid and low lift, while keeping the port as small as possable.

 

The factory heads are 2.02 intake & 1.60 exhaust
I am going to try a 1.94 intake & 1.70 exhaust. The larger exhaust valve should help the performance with the turbo's and the boost should compensate for the smaller intake valve.

 

i think your blowing your money. just turn up the boost.

the only reason i see for spending a significant amount of money on heads is if the new heads will help the head gaskets stay in the motor. i am sure you will gain some power at a given boost level but you could also just turn up the boost and have the same power for a lot less money.

 

The old rule of thumb I always heard was make the exhaust flow really really well, even at the expense of the intake, because the intake side will be pressurized. Sounds like you've been thinking along those lines.

These days, I'm with Parish. Heads flow so damn well out of the box, I don't think much needs to be done in a turbo application. Yeah, maybe if this is a race car and you need every last hp, go for it, but it's definitely cheaper to just turn up the wick.

I run a stage III head and it get great hp / psi numbers, but at the end of the day, I could easily make up any difference in that ratio with a few more psi.

If I had it to do over again, I'd get a good set of flowing heads and invest the saved cash from custom work on an awesome set of springs and a great set of roller rockers. I ended up doing both of those things anyway...

 

What you gain with ported heads could have been gotten with 1-2 psi of boost.

 

Thanks for some different points of view. I was trying the head modification in order to extract even more power from a max amount of boost. I am limited to 91 octane and the most boost that 91 octane will allow. I was hoping to get even more hp from the heads and stay within the limits of my fuel.

 

Why not add Alcohol or Meth and up the boost even more? My plans for the Camaro is one boost setting for pump, then a much higher boost setting with Meth

 

I'm probably the least informed here about FI, but I thought the same about a head upgrade. I went with cnc ported LQ9's and will run plenty of boost as well on 93 for a DD...can't hurt. Look at some of the guys in the valley. It seems many have a good set of heads. I know na is TOTALLY different, but it's the heads that determine the power capacity na. NA power can be about 2 hp per intake cfm. Probably should take the advise of guys that have boosted for years though. Good luck!