Ok guys here's what Joseph's Z28 adding just the Street Precision Race Components LS6 heads.


What you have to notice is it's not only hp she's gaining, it's huge torque as well! The setup makes more torque than the stock heads at the start of the pull!! 2500rpm & already making more torque!!

Pretty hard to beat for the $$$!!

 

What cam is he running?

 

235/240 112

 

Car just picked up to 430@400 with a little lean out

 

Are the heads milled any?

 

Do you have the full list of mods for his car?
I totally think my headers, and sotck cats are killing my power numbers.

 

My mods are in the sig. I also have been running a Hooker Y-pipe and TSP Rumbler Catback (for both dyno's) the last couple of months which isn't as good as my true duals were. I havn't bought a pulley yet, and I'm thinking of going with a MS3 next so there is a little more left.

Heads/Cam is about as far as I planned to go with this car as far as engine mods, so for once in my life I'm almost done modding something.

 

what dyno was that?????

 

I'm pretty sure that was on a dynojet.

 

Its an in-ground Dynojet Model 248C.

 

seems like good overall numbers for a cam like that.....what do you think those heads would pull with full bolt-on and a 231/237 cam

 

good results but were the new heads milled at all or thinner head gasket, were the runs done the same day and are they sae corrected, and what was the air fuel ratio and timing on both of the heads and finally was there a reason the runs stopped at 6200rpm's with the new heads, sorry for all the questions

 

would the 2.04's clear with a MS3 cam.....I have been looking for a good set of heads for the cost to go with my MS3 cam I am getting soon

 

N/P on the questions:

They were milled .003" for cleanup and to make sure there was a flat surface - just like all heads PRC does. I'm running .051" Cometic gaskets, the same that I had with the stock heads. I had to replace some lifters 3 weeks ago, so I prepared the car for this upcoming head swap with the Cometics and ARP Head Bolts to save time on cleanup, and in torque procedures. It worked as this swap took 4 hours.

The Cam-only pull was yesterday after work, about 7pm, I finished the swap at midnight and did the dyno pulls this morning after I arrived at work, about 11am. I believe the cam-only setup was 13.3 a/f at the tailpipe, and after heads was 12.9, at the motor it would be .5 richer if we were testing there.
Not sure what Jason finally tuned it for as I was in a rush after lunch and didn't check.

The pull was ended at 6600, but I had a spark plug wire start cutting out up top, so the graph shifts down. After replacing the wires with MSD's, it picked up a little more and didn't cut out. The last pull we did today was 430rwhp and 400rwtq, we always use SAE.

I'm pretty happy with this setup, especially for the price - everything I bought was economical other than the splurge for coated headers.

 

Damn that is awesome. One question though, these heads are a little bit more than $850 with springs that will support a 235/240 cam, aren't they?

 

I forgot to mention that I have PRC doubles on mine now. My stock heads had Comp Cams 918's with a ton of miles. I had other plans for the 918's or I might have reused them.

The PRC LS6 heads come with new valves, seals, retainers, locks, and stock '02+ LS6 "yellow" valvesprings for no charge (~.560" lift capacity). The valves are not sodium filled, and are similiar to what the C5 and GTO LS2 engines have.

Single Comp 918 Beehive spring upgrade is $150.
PRC Double Spring upgrade kit is $250.

 

Those chrome wheels are not dyno friendly either. I have the same wheels on my Z06 and when I added them it felt like I lost 20rwhp. I would have to guess I lost a minimum of 10rwhp although it feels like more.

 

That is a nice improvement for a nice price.

 

do you guys have a custom grind cam to match these heads perfectly or is that 235/240 112lsa close?

 

Would these heads work with your 233/239 on a 112?