455GTO

iTrader: (18)

I have a Ls2 block being assembled with a 403ci assembly using Wiseco -8cc pistons and plan on spraying a 300 shot. My current Ls1 has a set of AI 226cc 243 heads with 63cc chambers.

My question is how much am I leaving on the table using these heads? Of course id love a set of Tfs 235's but the budget isnt there right now. Down the road I'd love to go bigger if its worth it. Anyone have any imput?

96capricemgr

iTrader: (1)

Use what you have.

KCS

iTrader: (20)

I think those heads are going to be small for a 400ci engine. It would be a fun combo for a street car with lots of low end power, but I don't think that's what you would want when you're on a 300shot though. Depending on the cam, I doubt you will break 480whp NA.

If you're going to go racing, I would look at some ported LS3 heads. I think the larger valves and cross sectional area will help feed that engine at higher RPM and maybe soften the low end to help with traction. 550whp NA with a intelligently selected cam isn't unreasonable.

JakeFusion

iTrader: (7)

Depending on budget... TFS 255s, MAST 255s... or step up to the MAST 265 LS7 heads.

I think with that kind of nitrous, you want the big runner square port stuff and an aftermarket casting.

455GTO

iTrader: (18)

Thanks for the insight guys. The cam I plan to run is a BTR stroker grind for nitrous. 251/266 63x/595 112+4. I will run the heads I have and see how the combo performs and save up for a nice set of heads down the road.

My lil ol' HCI Ls1 runs 12.1 on motor and 10.76 on a 175 shot... Thats with a super tight nitrous converter as you can see by the slow NA ET... Since then Ive upgraded to a plate and a 225 shot.

DavidBoren

Absolutely use what you have now. Those AI 226's are going to be a blast while you save up for your dart ls3 heads.

Check out speedtrigger's 403, if you haven't already. It's inspiring, to say the least.

455GTO

iTrader: (18)

Below is the reply from A.I. in regards to my heads and what other options would really entail. I thought it was a good read.

Thanks for taking the time to email! That head will support around 500-525rwhp or so NA w/ a HR cam, so you may find it will work out just fine since you’ve got a power adder app. If we re-CNC the larger 232cc ports + move to a 2.055” intake then it’ll gain another 20hp or so, but at that point we’re totally re-machining the head so it ends up at $1395 including a set of Manley Racemaster 2.055” stainless intake valves.

At that point you can usually sell the 226’s & spend about the same $ going to something like our 230cc head we cut in a TFS porter casting, or some of the newer stuff I’ll add to the site over the next couple months if you aren’t in a hurry. Going to the 280cc CNC’d LS3’s is an option ($2295 including new GM heads, CNC work, and a BTR dual spring kit), but that would obviously require another intake. Let me know what you think; thanks!