On my car the cutout is worth 15rwhp over my B&B triflow, so I would say you have some power left on the table by not using a cutout and running thru the factory cat back.

 

So your pull was with loose rockers? Wouldn't that reduce the valve lift?

 

One loose rocker (last one on the passenger side was completely loose )..

thanks,
Crowley

 

so it leveled at 6000? sounds like valvetrain issues. stock lifters? why the shorter pushrods if the 5.3's are unmilled? well...I guess it depends on the cam too. what does RPM and Jay say about it? Oh, if you are just looking for a number, finish the tuning and drop the catback (or just the muffler). I wouldn't...since thats not how you are gonna drive it. Did you put in the 4.10's already?

 

I would say a valve not opening would be a issue. Make sure all are TIGHT and get it tuned.

 

just an fyi, i dynoed back to back with stock catback vs. cutouts in the y-pipe and gained 35 rwhp. the y-pipe/stock cat-back setup is killing you. i couldn't believe how much it cost me. however, i still only did 403 rwhp and am still trying to figure it out what is wrong. LG get's the car in a week and hopefully it will be fixed.

 

Keep me posted ... fyi .. what springs do you have in your heads? Mine are 978's ...

thanks,
Crowley

 

978's here as well. once i find out where the problem is i'll post up. hopefully i'll get the power i'm looking for.

 

Thanks .. you still running the 230 cam?

 

still running the 230 cam as of now. after lg get's the car i'll be running the x2 cam. i feel the reverse split is far from optimal for these heads so i'm switching it out for a traditional split.

keep us updated on what you find.

 

I gain 18 hp and 10 lbs of tq with the cutout over my Edelbrock catback.

My catback is only a 2.75 inch I-pipe though, 3 inch for the lt1 cars for some odd reason. It is **** for hp but has a great tone with no rasp so as long as I got my cutout which will soon have a electric opener on it, it is staying.
Good luck and keep us posted on what it does as I was thinking of swapping to those heads soon.

 

I had the mods in my sig. installed up at RPM in Lewisville. I was hoping for some numbers closer to 400, but like you stated, their dyno has been known to give lower results than some around this area. Don't get caught up on just dyno numbers. The car hasn't been tuned yet, right? If not, you will pick up a lot with a good tune.

Is Chris R tuning your car? If so, he does a great job.

So, basically get rid of the stock catback and let Chris tune your car. I think you'll be much happier. Have you looked into some true duals from LANE's yet? If not, you should! RPM is a good shop, and they will take care of you. That's what I heard, and that's why I took my car there. I am very happy with my "new" car.

 

With one valve not opening at all, I am surprised you made as much power as you did.

 

Is this a joke!!!! how could you possible state that you made no power in your 1st post and leave this sentence out My guess is that most 7 CYL cars will not make great power when they are realy an 8 CYL. Next time you dyno you should at least take out the plug so the other 7 cyl's don't have to push the the dead cylinder as hard BTW how could a shop not run 1 more dyno pull after finding a problem like this

 

Apparently it was after the last pull that they noticed this .. I would think that it was loose at least ..

We did find out one thing .. Jay from absolute recommended the 7.35 pushrods .. the heads are unmilled so we put 7.4 pushrods back in (that was $130 I didn't need to spend ) .. I am getting a misfire somewhere, but with the old LG programing .. not sure what is going on ..

RPM is hooking me up though and they said they will find this problem (plus re-set my computer and then re-upload the tuned program and re-dyno .. also pull the catback off to see how much I am loosing ..)

I'll keep you all posted ..

Thanks,
Crowley

 

That should be 425 hp... combo / valvetrain or tune issue.