As the title reads, I would like your collective thoughts and opinions on the merits of 12 degree vs. 15 degree LS heads. Once again, I'm looking for somewhere close to 600 in a N/A package. Is it even possible to do this in a 427 and keep the motor fairly smooth on the street? This going in a Caddy XLR, not a Vette. I want to drive in traffic and not worry.

I currently have forged pistons to accommodate either the 12 or 15 degree heads.

 

From what I've seen, for max power you probably want to run the LS7 heads but the LS3 heads tend to produce better bottom end. They may work better in your heavy car. I have a very mild build 427 that I'd run in a XLR in a heartbeat.

 

What was different in the two runs shown in the graph?

 

Seems like LS7s will easily make the most power. May want to call Virginia Speed. They seem to have done a lot of these type of builds. When I built mine 2 years ago I tried to get a response to trickflow 235s versus LS7s. I wanted to go with LS7s since the vettes were doing so well on the dyno and tracks. I do think the vettes dyno better. But most said trickflows so I did. There are a handful of cars that have done exceptional well but I think those are a rwsult of the setups where people have done a lot of work on and really knew what they were doing. In hindsight, I wish I had gone with the LS7s. In great weather (50s) I went 10.55 at 133.34 on a 1.59 60 foot w/ 3.73s so I can't complain too much. I have a 00 formula with a race weight of approx. 3,650 lbs. It's a 6 speed. I definately don't make 600 rwhp.

WKMCD - Are you going to make to the track this year?

 

I was wondering the same thing bill. I will be having a 427 but it will be a LS3 based so i cant use LS7 heads. I have "ordered" some small bore LS7s from TSP, but if that doesnt ban out what is there? And it looks like either Scoggin DIckey LS3s or WCCH stage 3's. But it's hard to really find numbers of trick flow/AFRs compared to ported/worked over LS3s. Thats sort of the rock and hard place im at. So im curious where this goes.

 

403 vs 427

 

I promised the Shawn and Ed I'd make a couple runs. I just had a Level 5 tranny and diff done and an RPS Twin Light added so it will shift at high RPM. We'll see when the vette guys set up a track rental at MIR.

 

You may also want to consider rocker arm options. There are a few more for the LS7 heads.