Aluminum SVO X heads

with what sized motor?

If you really want to make power, just let you custom cam guy know what heads you are going to run. A ported set of x heads aren't going to give up that much to box-stock 205s, depending on the port work obviously.

One thing to keep in mind, on the discussion of normal aspiration vs. boost is that the port job could be horrible, with terrible velocity and a possible loss of power on a NA engine, but once you introduce boost, the whole game changes. Being that the air is force fed into the engine, as long as you have a decent shot to the combustion chamber and no obvious problems, they could produce great power.

205's are way too big for that engine

the 40x heads did verrrrrry well on my 302, i loved em, just had some strippage problems on the threads...

they are still too large unless you want to run around 6-7.5k rpm all the time. X heads get hell from everyone on here, but they perform, and as previously mentioned, they will flow better with a good port job..

it's completely according to what u wanna do with the engine how much power u want to make and such. if u want the most power possible out of it buy the afr's if u are only looking to stay under the 500 hp mark the x heads with a charger will get u there. but yea if u go with the 205's u will def have to push alot of rpm's to keep in the power.

I would suggest getting your current heads measured and flowed. If you then think you need to go bigger, this is where I'm going to deviate from the pack a bit.

A 205 head is not too big for a 306 let alone a 347 especially with a blower. Now the cam is important but I've run a Canfield 195 on a N/A 306 street car and had no complaints at all. The car idled like stock and would rev to 7K at the drop of a hat. It was a bit soft under 3K wiht a Vic JR and 750 DP but that was a good thing street driving.

As far as AFR. Not worth the money in my opinion. I don't get caught up in the CNC thing. IMO it's just a good way of producing the same port over and over again. The important thing is what is the size and shape of the chamber and ports. Something to keep in mind is the AFR 205 and 225 pretty much require a 4.125 bore as the CNC program for the combustion chamber is based on the large bore. With the 2.08 valve, using stock valve location, on a 4.030 bore you'll get a good bit of shrouding as well.

A better choice in head is the RHS 200 or 215. They have a slightly relocated intake valve but in the 215 will suffer SOME of the same shrouding issues as the AFR205 due to the 2.08 valve. These heads flow up to 1" of valve lift with just a slight amount of turbulance at .700. They take all standard parts and headers but are also drilled for the 3" spread bolt pattern so you can use large tube headers with ease.

Another good choice is the Highport or Canfield. These heads have draw backs in the fact you may have header cleareance issues and they will not take standard stud girdles due the revised intake valve location. They will make some great power and you can suck on them as hard as you want without stalling the ports. The revised valve location eliminates shrouding on a 4.030 bore. The Canfield 212 is pricey at over 2K but the 195 is the same cost as our RHS heads at 1395 which comes in about 500 less than the AFR. Both heads (Canfield 195 or RHS 200) are capable of 1.6HP per CID N/A and with a blower...