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It’s been years since I posted but here I am. So my potnah has a LQ9 block he’ll give me, and I’m thinking since it’s free maybe I’ll build a 408 and replace my motor. My current setup is a H/C/I LS1, it makes about 430hp to the wheels 380 tq. I figured I could reuse my cam and AI ported 243’s, but maybe go to a FAST 102 from my FAST 90/90, Cam specs below.
So is it worth the expense and trouble, how much more Power could I expect the setup
to make?
If you are going to a bigger motor go as big as you can get. What size are you now a 346? If so going from 346 to 408 will be a nice jump in hp and tq. If you can go bigger than 408 than that is even better you only want to do this once. Seems like you have some good heads and cam which will go well with the 408. My guess is it will move your current power band down about 500 rpm and give you better drivabilty. My guess with the good manifold and other stuff you will pick up 20% more power (assuming 408) which is nice - so say 510 and 460 on tq at the wheels. I think the tq would be more noticeable than the hp as I think it will come in at a lower rpm given your current set up. There are probably some 408 guys that can chime in here on what they have done and what works. Does the LQ9 block have bay to bay breathing like LS2 as I think that adds like 10-20 hp by just having that set up.
I'm sure the man knows more about engines than I do and for what you have going on that's the right cam but a 4.030 bore and a 4.00 inch stroke will make more power with more cam and rectangular cylinder heads.
I'm sure the man knows more about engines than I do and for what you have going on that's the right cam but a 4.030 bore and a 4.00 inch stroke will make more power with more cam and rectangular cylinder heads.
Yeah if you can afford them and the intake upgrade. FYI a stock LS3 intake is pretty good compared to aftermarket intakes and there's guys on here that can even port the LS3 intake. My current build is an LS370 12:4.1 motor with 823's a stock LS3 intake and NW92.
If you are going to a bigger motor go as big as you can get. What size are you now a 346? If so going from 346 to 408 will be a nice jump in hp and tq. If you can go bigger than 408 than that is even better you only want to do this once. Seems like you have some good heads and cam which will go well with the 408. My guess is it will move your current power band down about 500 rpm and give you better drivabilty. My guess with the good manifold and other stuff you will pick up 20% more power (assuming 408) which is nice - so say 510 and 460 on tq at the wheels. I think the tq would be more noticeable than the hp as I think it will come in at a lower rpm given your current set up. There are probably some 408 guys that can chime in here on what they have done and what works. Does the LQ9 block have bay to bay breathing like LS2 as I think that adds like 10-20 hp by just having that set up.
I’ll have to ask about the bay to bay breathing I’m not familiar with that.
Pretty much everything 01camarosstx is saying is spot on. The heads and cam will work but def not going to
help a 408 breathe. Personally I would with a 408 build at the very least go with ls3 heads and intake if I’m a budget and maybe a btr cam. If you look at the sticky called tuskys cook book https://ls1tech.com/forums/generatio...or-builds.html
it has a huge amount of great info on stroker builds. There’s a couple of 408s with ls3 setups on them making killer power. Then a couple of 408s with badass cathedral port heads running awesome times
Last edited by Z28SteveA4; Jul 5, 2020 at 09:50 PM.
Pretty much everything 01camarosstx is saying is spot on. The heads and cam will work but def not going to
help a 408 breathe. Personally I would with a 408 build at the very least go with ls3 heads and intake if I’m a budget and maybe a btr cam. If you look at the sticky called Tusky's cook book https://ls1tech.com/forums/generatio...or-builds.html
it has a huge amount of great info on stroker builds. There’s a couple of 408s with ls3 setups on them making killer power. Then a couple of 408s with badass cathedral port heads running awesome times
I would sell your heads and intake and get LS3 heads and intake.
LS3 intakes cost about $250 bare and new.
LS3 heads are $500 used.
That gives you an idea of costs.
I’ll have to ask about the bay to bay breathing I’m not familiar with that.
Basically on the LS1 block (I think LS6 too) and the 5.3 block the wall that the main caps bolt to goes all the way down making each bank of cylinders 1/2 3/4 5/6 7/8 isolated. On the LS2, LS3, LS7 if the main caps were off and you reached down your fingers could wrap around where the main caps were bolted to as there are windows cut in the bulk head between the cylinders which allows the air to go back and forth between the 4 banks of 4 cylinders. At higher rpm this becomes an issues as the air is somewhat trapped between the banks thus creating some resistance. There is a trade off the bays do weaken the set up a little. In the story of the LS7 to get to the 505 hp the bay to bay breathing was the last thing they had to do to get the 505 they were about 15 hp off. They wanted to use the full wall design for strength but it was holding the power back for them to get the 500+hp with all the other components they cut the walls for bay to bay and got the extra 15 hp. I think Steve at RSD has said the bay to bay breathing is worth like 10-15 hp. Blower guys with 5.3 are more concerned about the strength than the bay to bay so they don't mind using those blocks. The new Dart Block has the walls but uses a 4 bolt main cap (versus the GM 6 bolt cap) design and wider skirt that allows air to go between the banks instead.
Basically on the LS1 block (I think LS6 too) and the 5.3 block the wall that the main caps bolt to goes all the way down making each bank of cylinders 1/2 3/4 5/6 7/8 isolated. On the LS2, LS3, LS7 if the main caps were off and you reached down your fingers could wrap around where the main caps were bolted to as there are windows cut in the bulk head between the cylinders which allows the air to go back and forth between the 4 banks of 4 cylinders. At higher rpm this becomes an issues as the air is somewhat trapped between the banks thus creating some resistance. There is a trade off the bays do weaken the set up a little. In the story of the LS7 to get to the 505 hp the bay to bay breathing was the last thing they had to do to get the 505 they were about 15 hp off. They wanted to use the full wall design for strength but it was holding the power back for them to get the 500+hp with all the other components they cut the walls for bay to bay and got the extra 15 hp. I think Steve at RSD has said the bay to bay breathing is worth like 10-15 hp. Blower guys with 5.3 are more concerned about the strength than the bay to bay so they don't mind using those blocks. The new Dart Block has the walls but uses a 4 bolt main cap (versus the GM 6 bolt cap) design and wider skirt that allows air to go between the banks instead.
Well just as I thought my lil budget build dreams were just that. So my potnah has a set of LS3 heads for me $400. Now I gotta go get those portedalso, and I’m assuming it’ll be best to match new cam now also?
Well just as I thought my lil budget build dreams were just that. So my potnah has a set of LS3 heads for me $400. Now I gotta go get those portedalso, and I’m assuming it’ll be best to match new cam now also?
The porting isn’t necessary. Unported, the ls3’s will support a lot more power than your going to make.
From: Coast of San Mateo County Between Pacifica & HMB
Ported AI should flow what the stock OE LS3s do I would consider using your existing Heads and Intake
and just upgrade your existing cam (something like~ 237*/243* 112*+3* rowdy, 114*+3* mellow, .620"/.610")
The 4" stroke and +60" will drive just like your current combo with a good tune. ~11.2-11.7:1 comp,
depending on 91 vs 93 octane, combined with .035-.040 quench,
(Obviously get with Cam Motion or Darth to really spec you a cam for your goals, not a cam guru...
just like to play one on tech.) lol
Make the same HP and broader torque curve due to higher port air speed, ~600 HP @ Crank & ~520 lb'
500 RWHP & 440 LB' with wicked throttle response everywhere. For what you are looking for and
budget you have great heads and intake for 4.030" Bore and sub 7000 RPM street/strip car fun driver.
You need more rpm and cam to utilize ported LS3 heads IMO.
Or mill LS3s clean up exhaust side a bit , your existing cam would work pretty good with the much LARGER ports,
260 cc VS 230 cc for close to the same air flow ~ 315 CFM enough for 640+ HP @ Crank.
Just my .02
Good Luck
Last edited by NAVYBLUE210; Jul 6, 2020 at 10:00 PM.
Hey man, I read your sticky, nice work! I built my current setup to be able to still be a daily driver if needed (even tho it’s probably got less than 10k miles in the last 5 years) with great power, be very reliable, but still be able to bust *** if these newer high HP cars try me. I feel
torque under my current setup is really lacking, top end speed is underwhelming also. I still want the reliability, but I’m looking for a lot more HP and torque now. That’s why I figured I’d build a 408 instead of just the standard 6.0. But if the new setup can run in the Tens and I can still use the car to make a 3 hour run to the Florida coast I’d be excited. My friend has the 6.0 block and the 823 heads, and I have my Ai ported 243’s, I’m just tryna figure out the best combo. Also, I saw texas speed has a 218/221 stroker kit for the LQ4/9 setups should I be considering that also if I don’t ever plan on forced induction?
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Too stroke or not to stroke!? 
