built head, eprom, dsmlink

[HiImBrian]

Throw a 2G head on it.

Why would I do that when 1g heads flow better?

[Shane@DBPerformance]

Which one makes more power though? Take a look at the port size on an Evo head, it makes 2G stuff look big. And those heads make killer power compared to DSMs. I have always had good results with 2G heads on cars from 16Gs to GT35Rs. The 2G intake manifold and throttle body do suck. I have one customer with a stock 2G head(with 272 cams) on 2.4l bottom end and 61mm turbo. It makes a tad over 400 DD awhp at 19psi on pump gas.

[HiImBrian]

Which one makes more power though? Take a look at the port size on an Evo head, it makes 2G stuff look big. And those heads make killer power compared to DSMs. I have always had good results with 2G heads on cars from 16Gs to GT35Rs. The 2G intake manifold and throttle body do suck. I have one customer with a stock 2G head(with 272 cams) on 2.4l bottom end and 61mm turbo. It makes a tad over 400 DD awhp at 19psi on pump gas.

Well tell me if I'm dumb but I was planning on doing a 6bolt bottom end down the line when/if my 7bolt walks and I thought i'd just be easier if I started out with the 6bolt head. Plus I figured that the 6bolt and 7bolt heads are the same except the 6bolt flows more. Am I missing something???

[tim]

Well tell me if I'm dumb but I was planning on doing a 6bolt bottom end down the line when/if my 7bolt walks and I thought i'd just be easier if I started out with the 6bolt head. Plus I figured that the 6bolt and 7bolt heads are the same except the 6bolt flows more. Am I missing something???

It might flow more but like Shane said, look at the Evo head as an example. The least restriction(flow) is not necessarily the key point. You need velocity to get the air/fuel charge into the combustion chamber.

Get to the point of a huge turbo and maybe the 1g head will be better? I cant say for sure because I have never researched it.

[TkrPerformance]

I have a compleat evo III head
bigger stock cams ,heaver springs,flows the best of the heads
250.00

[HiImBrian]

So let me get this straight. 1g heads flow best, followed by the 2g heads which are then followed by the evoIII head. But what you guys are saying is that my big16g may not flow enough to actually "need" a 1g head? I always figured the 1g head would add a little power because of the whole flow thing.





I have a compleat evo III head

bigger stock cams ,heaver springs,flows the best of the heads

250.00



pm sent

[TkrPerformance]

the evo head make the most over the dsm heads because of the design of the head and runners in it

[HiImBrian]

Ok so it may not flow more than the 1g's but because of the design of it it's able to make more power?

[Shane@DBPerformance]

You want the head to perform optimal cylinder filling. Too big of port/too much flow and velocity of the air slows down so much that you don't get a complete fill during the intake stroke. You could bore the hell out of the ports and make them flow whatever on a flow bench, but that might be counterproductive unless you are reving to 15,000 RPMs.

It's is hard to say what is best. The old conventional wisdom was that bigger was better, 1G head had bigger ports, so it's better. I am rarely disappointed by cars on the dyno with 2G heads once the shitty intake manifold, TB and cams are replaced. I am often disappointed with cars with ported 1G heads on them, more than ones with stock 1G heads. I don't push head porting at all at our shop, most of the decnet power DSMs that I have dealt with have had unported 1G or 2G heads. Some of the fast guys started figuring out how little doing a stage 19 head port helped when they would ruin their main head and have to throw on an unported backup head at the last minute at the track or dyno.

I would do a little clean up work on any majopr casting flaws, but I wouldn't go much farther than that, and polishing is absolutely worthless except for pictures.

[HiImBrian]

Thanks for the info! What about an EvoIII head? shorter runers but they don't flow as well. Would it be worth it to port that out or would it be best to leave it stock?