Looking to build a 370 or a 408. The more I look at it I want to go with the 408. The part I am wondering about is what would be a better direction to with for the top end.
I have two options I am looking at and not sure what will be worth more power.
I can get prc 225 heads and use my ls6 intake.
Or I can get stock 243 heads and get a ported fast 102/102 combo
Both options will be around the same money. Witch one does everyone think will perform better?
Cam will be picked out for witch ever direction I go with the top end.

I could actually probably get the 370 with the prc 225 and stock fast combo but I would think the 408 would have tons more tq

Just lots of different options and I tried searching but I can not find exactly what I am looking for.

Motor is going in a 6sp firebird. The car is no longer a daily driver but I want a good driving car that I could drive every day if I wanted too.

I look forward to everyone's opinions.

 

The 408 will have a little more torque...not tons. Either of two options should be close in terms of power. I'd get someone like Mamo to do the 243's and Fast 102

 

I would love to have Mamo do the 243 and fast it's just not in the budget. I can swing the ported fast just not the both of them ported.
I really like your set up I have read your threads a million times and was going to clone your set up till the 408 peaked my interest. I really would like to put down 450tq is the main reason I was thinking 408 instead of the 370.

 

Gotcha! Thanks for the compliment! Just to give you a comparison when I swiched to the 370 from the 346 I did in fact experience a broader torque gain, but it wasn't big by any means...just enough to notice though. The main reason I didn't go to the 408 over the 370 was because I knew the heads were limiting me big time at that point, and that for the extra $800 I wouldn't benefit much. The 408 makes much more sense with a much better head, otherwise it won't do much overall

 

ok so if both 408 set ups would be close. How far apart do you think the 370 prc225 ported fast and the 408 prc 225 and ls6 intake would be?

 

Well see that's the thing....you do the exact same setup on both the 370 and 408 there will be no difference in hp and maybe 15-20 tq with the 408. To me it's not enough to offset the price difference. That's just my opinion of course. But if you add the Fast to the 370 (but not with the 408) you will not only make more hp but the tq will be close as well

 

Personally I'd go 408 with ls6 intake. Going this rout your motor would stay together when you have the funds for a better intake. Go with the 370 and when its time to port or upgrade the heads you'll have to tear top end apart. I beleive the 408 with ls6 would make more average power through to.

 

IMO, you're going to want heads with high flow velocity at lower rpm levels . So have Mamo port you 243's and spec you a cam with you want for high TQ, and leave the FAST 102 stock for now. I'd go with the 408 for the most TQ.

 

I'd go with the 408 with PRC heads and replace the LS6 intake later when you can afford it. It's way easier to replace the intake than replacing heads.

 

Might be blasphemous on a third gen thread but for a 408, if you want cheap high flowing heads, grab a set of LS3's.

 

When i was looking at a 408-408 I was gonna go with prc or trickflow 235's and have a cam specd for it. Like some said you can always get the intake done later. For a driver the torque is nice and seat of your pants feel. I just made another 80 hp and 60ftlbs through a slipping clutch with a 383 and i was laughing my *** off yesterday after getting it from my tuner. It feels so much stronger power wise with the low end and pulls like crazy, street tire are useless lol. Im not staying in it either as the clutch needs to be done

 

I think the 408 with the prc 225's and ls6 intake would be your best bet. Like previously mentioned, it is much easier to swap intakes when funds allow.

 

Personally my first choice would be the LS3 head/intake route if budget was really tight.....
On the other hand I would do a TFS 235 head with a custom cam by Brian Tooley.
Some 235 TFS heads for 2000 bucks in the classifieds.

 

Thanks for the input everyone. I think I will be going 408 prc 225 and ls6 intake.

 

I don't think you will be disappointed in the least. Those prc 225's flow just as well as stock ls3 heads on the intake side, with a much stronger exhaust flow ratio, and should provide a very responsive and fun driving experience. Keep us updated with your progress and results.

 

Good choice. It's much easier to swap out the intake later when you get some more money than the heads.

 

I agree. Or even if your budget isn't tight. I like the LS3 heads better on strokers. Check out the video of my latest build. While these are Dart LS3 heads, they are even bigger than the stock LS3 and they are on a a 4.005" bore. So, I don't subscribe to the theory that they are too big for a 408. This engine is a 403" and look at the torque:

 

I have been researching this heads a lot. They are for sure going on what ever combo I end up on.

This is very true. Will probably be a wile down the road though as the wife will only let me do this one time

I have thought about the ls3 head route but what all would I need to switch? Intake, fuel rail, rocker arms, and tb what else would be needed?

 

All that & a map sensor extension harness ($20), ls3 throttle cable bracket ($20-30), make a bracket to hold the ls1 map sensor in the ls3 intake, will need a short piece of clear 3/8 hose on the end of the map sensor so it seals in the intake. & modify the passenger side valve cover so it clears the rockers. Basically cut the baffles out or get an ls3 valve cover. I cut the baffle out of mine.

If running an ls3 intake & fuel rail its easiest to get ls3 style injectors. I went with low mile 52 lb LS9 Injectors & were only $225. Also need USCAR to EV1 fuel injector adapters(under$20) to connect to the stock harness.

 

I guess you can get everything for about the price of the prc heads... AND the ls3 top end can be mamo-fied (or ported in general) when funds allow. Whereas the prc heads are about as good as they are going to get, and offer no room to grow other than the intake upgrade.