Tuskyz28

Really? Every 408 I have seen with TFS/AFR cathedral head is over 500 rwhp.......
You must had been looking at those guys running 317 heads on 408 Ci motors LOL

Assman

iTrader: (2)

What is everything needed to do a ls3 top end? Intake, some sort of heads, fuel rail, but what does everyone use for a cable driven throttle body? Are the ls3 injectors good enough for a 408? Where do you get the adapters to plug them in? Are there any more sensors needed that won't adapt from the ls6 setup?

ragtopz28

iTrader: (57)

I'm planning on using the stock fuel rail and injectors on my LS3 intake with a NW92 DBC. I believe there is an easy sensor fix for the back of the LS3, but I haven't gotten that far yet....

dr_whigham

iTrader: (49)

Fuel injector adapters, the stock LS3 are 42# I believe so you should be good, a NW/PTM 92 TB, intake, rail, and heads. And an extension pigtail to put the MAP at the front. That should be about it. Not hard at all.

Assman

iTrader: (2)

Ok it's sounding like the ls3 top swap is right for me especially given my ls6 intake restriction. Would I need rockers as well? I read something about the ls3 rockers being different.

Thanks for everyone's help and input, it is much appreciated!

M.BOZZ

iTrader: (14)

Yes, the intake rockers are off set. so your looking at a set of intake rockers, do the trunion upgrade on all. Rocker stands and if your using your ls1 valve covers you will need to grind away aliitle on the inside ( no big deal ) or find some used ls3 valve covers. If you are getting the hollow intake valves ( 821 ) i believe, then your going to have 2 different valve heights.Two choices are to get 2 different push rod lengths ( i did ) or get the valve tip ground down alittle, they sell shim caps for the top of the valve but i don't like that thought.

george g

iTrader: (12)

That's all you need,plus the intake rockers.

HISS

iTrader: (52)

Ok so let's compare a set of heads that retails for oh over 2k to a set of stock cnc ported cathedrals. The man is trying to remain budget friendly. We can't all afford afr/tfs heads. So let's spend under a grand for square ports and make the same power......it's not rocket science genious. Read some more Internet bs and post again, I'll wait.

Tuskyz28

Not bashing square ports at all..... I own a set myself on my 370ci on my car with a 229/244 cam. They a great head no doubt but they not the best. Cam selection is what plays a role with a LS3 head.... that's why you see some guys wondering "what happened" and the next guy having a party.....

Assman

iTrader: (2)

From my rough figures it seems I'll be saving about a grand over a cathedral setup to flow about the same, plus I'll get the benefits of the ls3 intake over the ls6 that I'd be using. I think I'm sold, now the question is heads. What about these heads?
https://www.texas-speed.com/p-1179-p...ted-heads.aspx

Is there another comparable option that doesn't break the bank?

M.BOZZ

iTrader: (14)

Nice heads, but you scroll down and add $275 for springs ( thats ok ) $375 for hollow intake valves. Or you can get the gm 821 heads with hollow stem intakes, light cnc $1200 at summit and replace the springs

HISS

iTrader: (52)

^ding ding ding, this is good advice!^

Assman

iTrader: (2)

So with the intake valves being longer does that affect the spring install? Would those have to be shimmed? Those summit heads would save even more money, I'm digging it!

M.BOZZ

iTrader: (14)

No, will not effect valve spring install height. I have push rod length of 7.305 and other is 7.315, with comp short travel lifters, 0.041 gaskets and heads milled to 65 cc. My engine is nothing crazy put down 487rwhp @ 7, 200 rpms on mustang dyno.

Assman

iTrader: (2)

Well you guys talked me into it, I just ordered the summit ported heads. Looks like I'm committed to the ls3 route!

Assman

iTrader: (2)

What throttle body is a good choice? The ptm was out of stock at Texas speed but they have the nick Williams readily available. What about the cable mount bracket?

HISS

iTrader: (52)

Get the NW tb, I run it and it's a nice piece. The throttle bracket can be found on good ole ebay, or I think a few of the vendors on here sell one. Glad you bit the bullet and made the decision. Good luck with the build!

M.BOZZ

iTrader: (14)

That's the ticket, just like HISS said, the nick Williams is a good tb. If I can remember I used the factory tb cable bracket for my fast intake. But a google search will work

VandykeT/A

My Prc247 and 251/259 cam made 523/487. They had nightmares tuning it from the massive intake vacuum leak and the lifters collapsing lol. Motor had a weird knock we couldn't find and a lot of valve train noise we couldn't figure out until we lifted the rockers off the valves 1/4". Hard to say what that setup would make dyno'd healthy. You could do 247s and wait for a intake. Just a thought.

kyleholt11

iTrader: (3)

thats the route i went... prc 247 heads and a texas giant cam... im running the ls6 intake for now and later upgrading to a fast intake