Hey guys, so this summer I got my 408 built and its in my truck. Turned out good and runs solid without any issues. Here are the specs:

408ci LQ4 Short block
Callies 4" crank and 6.125" rods
Wiseco flat top 11.5 compression pistons

Stock LS3 Heads
Stock LS3 intake
231/239 114+2

With this combo through a 4L80e Silverado, it made 434whp and 400wftlb. Good not great... I would think the torque numbers would be a little higher but it runs strong. Obviously the H/C/I combo is really holding this project back.

I want to get everyones opinion on a cylinder head that will wake the numbers up.

 

L92...

 

? Did you read my post? I have LS3 heads on there right now.

 

Something/anything ported. That motor wants to breathe.

 

TFS or AFR

 

How big of a runner could I run. This is a daily driver. But I don't want to leave power on the table. Is 235cc too big? 225cc?

 

AFR 215cc and a Fast intake. as stated above... that motor wants to breathe!

 

The new AFR 230's or TFS 235's would be nice. Almost any of the MAST deals too. Put a FAST LSXrt on there too.

 

Yea when I get heads, I will for sure get a fast intake and cam to match. Any ideas how much horsepower/torque AFR 230's Fast intake would produce.

 

Mozes

 

I don't think heads are your problem. Stock LS3s with similar cams are putting down way more power. LS3 heads on a 408 should be a 500RWHP combo.

 

Yes, through an m6. 4L80e's are extremely robbing. I figure I'm making around 550 at the crank. Right where it should be with stock heads/intake and a small cam.

Also the tuner didn't spend much time on it. I was pretty disappointed. He didn't tune for different injectors or anything like that. I think he only played with the VE table and timing. So i'm trying to learn the tuning part of this motor as we speak.

 

If you don't like your heads... when you get more, wanna sell them to me?

 

AFR if you have a good budget.

 

AFR heads and fast intake and throttle body,GOOD tune!!

 

Send your heads to advanced induction im sure he can fix you up with a cam too.

 

Yes there are better heads but your problem is not with your heads. Get it tuned correctly first and see where you are. I have seen a good tune pick up 30+. Also what exhaust are you running and are you sure lifter preload is correct? Unless you are just on a stingy dyno those #'s are pretty low. My old 346 made those exact #'s on a smaller cam.....

 

First off I thnk your cam is too small for a 408 but for heads I would go with some TFS 235's. If you don't have a FAST intake you should look into that too

 

At your altitude and air, and being in a truck, you need grunt (torque)...not just hp. The best way to create that is with velocity through the intake tract. I'll bet you that AFR would recommend their 205 cc heads. I would be shocked if there was a significant drop in top end, but the bottom end would be a bunch better due to the increased velocity through the intake ports. This is assuming you have good headers and exhaust. I have a lot of experience running at 4500 to 6000 feet in elevation. This will help. You may be nowhere near that elevation, but in Las Vegas, I can guarantee the density altitude will be way up there most days.

 

Yea thats funny, those were my exact numbers. I was trying to run 1.875" headers and they didn't fit my truck so I had to overnight some replacements. They only thing they had were Pacesetter 1.75". From there I'm running 3" to a dual inlet Magnaflow, and a single 4" out.

Obviously I need to buy a wideband and tune the truck myself.