My lq9 started developing a rod knock this morning so its time to pull the trigger on a 408. My local builder is doing it for me, will be an eagle rotating assembly with wiseco pistons. Motor will be roughly 10.5:1 and he will spec the cam out as well. I have a fast lsxr-t right now but was considering selling it to fund some of the build and just going with a tbss intake or something similiar. i know it will kill performance a bit, but it will get me by until i can get something later. For the complete short block assembly and cam kits/ gaskets its $4500, so i need a top end to complete it. I am trying to stay under $6000 for the long block but can budge a little.

So that being said, rectangle or cathedral port? How bad will a set of factory ls3 heads be for it? im on a semi tight budget for heads so cant go all out. I know with my budget it wont be optimal but i can change things later as i get more funds. any incite is appreciated

 

If you're talking factory as cast heads I go square port. If you can afford a decent port job from AI or TEA etc I go with a cathedral. It would be a screamer with a ton of grunt on a 408.

 

I was looking at my options. I can get a used set of ls3 heads for semi cheap that are worked. I have a budget of about $6000 so I have around $1500 for heads. Maybe a bit more if I can sell my fast set up and just go with a tbss intake until funds permit.

 

Keep the FAST there is plenty of budget heads that will work on the 408.

Compression is going to be dictated on your heads chamber size. with that in mind where do you need to be on that end of things?

 

As far as compression, I'd like to be in the neighborhood of 10.5/1 or more. Will most likely be closer to 12 to 1. I'm still debating on putting a decent cam and heads on a lq9 and just getting it going. Then just start acquiring more parts for the 408 and doing it in winter.

 

If you are building this thing from scratch then make the compression whatever you want. Just pick the right combo of piston, gaskets and heads. If you are running stock untouched heads then just calculate based on those chambers.

A stock LS3 head is 68cc so a -8 Wiseco piston with a .051 gasket will put you at 10.6-1
A -3 Piston in the same combo would be 11.3-1

 

Buy these

230cc LS1 Cylinder Head - Air Flow Research

 

I am not a huge AFR fan but some are, not that their is anything wrong with them. I like TEA's TFS offerings, that's what's going on my new motor.

 

Lol those are out of my budget. I've actually decided to go with a 6.2 and do the vvt delete and cam kit. I found one aND it's to good a deal to pass up.

Selling my fast lsxr-t set up if anyone is interested. It's in the classifieds

 

what is the vehicle weight?
I did a lot of reading and a lot of calling around when I was picking heads for my 408 and everyone told me to stay cathedral port to keep the low end torque to get the weight going.
I ended up with TFS 245 that I had sent to TEA for more porting and the n2o exhaust ports.