OP
OP
Tonyrodz
Resident Resident
This is what he gave me today. Forgot to ask about trunnions and the HD chain. What do you think?
317 Heads
- Thread starter Tonyrodz
- Start date
Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.
This is what he gave me today. Forgot to ask about trunnions and the HD chain. What do you think?
iamdub
Full Access Member
I'm sure the HD chain is ok, but the HD LS2 timing set just makes me feel more comfortable because it's an OEM part and it's proven.
Torque converter size is determined by many factors- cam characteristics, vehicle weight, trans and rear end gearing, tire diameter, intended use and desired overall performance
Torque converter size is determined by many factors- cam characteristics, vehicle weight, trans and rear end gearing, tire diameter, intended use and desired overall performance
OP
OP
Tonyrodz
Resident Resident
I can't wait to do this. I asked about the 317 heads and he said EXACTLY what you stated in the post. Thx for that! He said this package runs really well. Told him I wasn't looking for a race truck, just something with some get up and go. After this, going to put a shift kit in, just to help the trans live a little longer. My gf drives it 95% of the time , and she's easy on it, but that 5%! Oh yeah!! 
iamdub
Full Access Member
The good thing about going with a "package" such as what he's proposing is that it's been done before and therefore proven. The parts work together and it's not gonna have any trial-and-error tuning. Just swap in the parts, upload the tune, tweak as needed, and hit the road. That converter has already been paired and tested with that combo and Circle D is good stuff. Seems like you're in good hands. Try to get before and after vids of it running and/or exhaust clips!
Any room in the budget to spare $350 for long tube headers? Those alone make a noticeable increase in power. They would complement the cam nicely. It'd be best to have them installed at the same time so the truck can be tuned for them.
http://www.speed-engineering.com/sh...ck-suv-longtube-headers-y-pipe-1999-2006.html
Any room in the budget to spare $350 for long tube headers? Those alone make a noticeable increase in power. They would complement the cam nicely. It'd be best to have them installed at the same time so the truck can be tuned for them.
http://www.speed-engineering.com/sh...ck-suv-longtube-headers-y-pipe-1999-2006.html
Last edited:
OP
OP
Tonyrodz
Resident Resident
Oh yeah! The long tubes are def going on, also from speed engineering. Getting the 1 3/4 with y pipe. Only thing I don't like is it's an off road pipe and in NJ we do emissions, even if it's only a visual. You actually have to drive over a camera, checks for a cat.
iamdub
Full Access Member
You have pre-cats? You could have the pre-cats (maybe hollow them out?) and O2 sensor bungs from your original Y-pipe welded in and put in place, but have them turned off in the tune. No need to mess with the downstream/main cat.
OP
OP
Tonyrodz
Resident Resident
Whatever is under there is the stock deal. I really need to look and check. I have a brand new cat in a box, but it's a ****** after market I was going to put on my 95 s10. I think it's probably a 2 1/4 opening. I'd really like to get a high flow if possible. When you say pre cats, you mean after the header collector, somewhere in the y pipe, down stream, past the collector?
iamdub
Full Access Member
Yes. I've never looked that much into the exhaust on the GMT800 or 900 so I don't know what's between the manifolds and Y-pipe merge. I know the main thing that's really watched for is the main cat just in front of the muffler. I know there are O2 sensors on each bank as they are needed to monitor the A/F ratio. I could be wrong, but I don't believe there are sensors monitoring the efficiency of the pre-cats, if there are any. Regardless, your state might be tight on any modifications and may know what your truck came with and what should be there. If it has pre-cats and if they inspect for it, I'd cut 'em off the stock piping, hollow them, open the holes to slip over the SpeedTech Y-pipe, and weld the empty shells wherever they'll fit. This way, you'll pass visual and the hollow shells will still have the Y-pipe smoothly going through them. Place O2 sensor bungs/sensors wherever they fit and look appropriate, but turn off their codes in the tune. Except, of course, the O2 sensors that the PCM actually uses to monitor each bank. "High-flow" cat is a bit of a misnomer in the sense that the factory cats are essentially "high-flow". OEM and aftermarket cats are all made up with a tubular matrix of catalyst. It's just that some cheaper aftermarket cats have a lower grade catalyst that may not be sufficient. None of this matters for the pre-cats if they're not monitored. Just crawl under there and take a peek at the layout. Be aware that some flex joints are mistaken for the small pre-cats.
*EDIT*
Curiosity owned me: My '08 has no pre-cats or a single cat just in front of the muffler. It has an '02 sensor after each manifold collector (obviously to monitor A/F ratio), a cat on each leg of the Y-pipe after those monitoring O2s, an O2 sensor to monitor those cats, then the pipes merge together on the passenger side and continue towards the back to a flex joint, then from the flex joint to the muffler...
I was picturing my S10 exhaust when I wrote the first part and assumed the third-gen LS stuff was similar. Either way, there's relatively easy ways around inspections unless they look to see if the tune has been altered to turn off any emissions-related codes.
*EDIT*
Curiosity owned me: My '08 has no pre-cats or a single cat just in front of the muffler. It has an '02 sensor after each manifold collector (obviously to monitor A/F ratio), a cat on each leg of the Y-pipe after those monitoring O2s, an O2 sensor to monitor those cats, then the pipes merge together on the passenger side and continue towards the back to a flex joint, then from the flex joint to the muffler...
I was picturing my S10 exhaust when I wrote the first part and assumed the third-gen LS stuff was similar. Either way, there's relatively easy ways around inspections unless they look to see if the tune has been altered to turn off any emissions-related codes.
OP
OP
Tonyrodz
Resident Resident
So you have 3 O2 sensors and 2 cats on your 08? Hopefully this weekend it'll be nice enough for me to get under there. I used to do inspections at a state facility. As long as a cat there, that's all that mattered. Doesn't matter what it looks like or located. Shops today won't do anything with a hollowed out cat, they're scared they'll get caught. Can't blame them tho. Funny, my express van has a hollowed out cat and I'm not throwing a code. Granted the o2 is before the cat. Think maybe I should throw on that new after market cat? Even tho it has a small opening? Think around 2 1/4. I think the stock pipe is somewhere close to 3 inches. Wouldn't that be a bottleneck?
iamdub
Full Access Member
I have 4 O2 sensors, two on each bank and 2 cats, one on each bank. One is upstream of the cat just after the flange that connects the Y-pipe to the manifold. This one monitors the air/fuel ratio. The other is just downstream of the cat. This one monitors the cat. The other bank is set up the same.
I understand that a shop won't hollow out a cat, but surely you can handle it. BTW, save the catalyst as recyclers will buy it. I had the cat cut out of my S10 and ran an O2 simulator since '04. I went to a shop and explained that I "had a damaged portion of my exhaust pipe that needed to be removed and replaced with a new piece of pipe" while pointing to the general area of the cat. The guy understood what I was saying without actually saying it. $25 and 15 minutes later, I had what I wanted. You can doctor up the Y-pipe before you have it installed if you can determine where to put the "fake" cats where they won't affect the fitment in the truck. The O2 sensor before the cat in your Express van isn't monitoring the hollowed cat because it is upstream from it. It's monitoring the exhaust for fuel trims. Is it an older van? Some (or most/all?) older vehicles (I think just OBD1) didn't have an O2 sensor to monitor the cat. You should most certainly NOT put that tiny cat on your exhaust as it will be a bottleneck and counter the purpose of the longtubes.
Bottom line- If you have any cats between the manifolds and where the Y-pipe merges together to form one pipe, you will need something that looks similar (even empty cat shells) on the new Y-pipe. None of it has to be functional as it can be tuned out. If your stock setup has any sensors immediately (within a foot or so) after the cat(s), you will need to have them installed in the new Y-pipe for visual purposes. The O2 sensors that matter are the ones after the manifolds, before any cats, and the headers will have bungs for these in place.
I understand that a shop won't hollow out a cat, but surely you can handle it. BTW, save the catalyst as recyclers will buy it. I had the cat cut out of my S10 and ran an O2 simulator since '04. I went to a shop and explained that I "had a damaged portion of my exhaust pipe that needed to be removed and replaced with a new piece of pipe" while pointing to the general area of the cat. The guy understood what I was saying without actually saying it. $25 and 15 minutes later, I had what I wanted. You can doctor up the Y-pipe before you have it installed if you can determine where to put the "fake" cats where they won't affect the fitment in the truck. The O2 sensor before the cat in your Express van isn't monitoring the hollowed cat because it is upstream from it. It's monitoring the exhaust for fuel trims. Is it an older van? Some (or most/all?) older vehicles (I think just OBD1) didn't have an O2 sensor to monitor the cat. You should most certainly NOT put that tiny cat on your exhaust as it will be a bottleneck and counter the purpose of the longtubes.
Bottom line- If you have any cats between the manifolds and where the Y-pipe merges together to form one pipe, you will need something that looks similar (even empty cat shells) on the new Y-pipe. None of it has to be functional as it can be tuned out. If your stock setup has any sensors immediately (within a foot or so) after the cat(s), you will need to have them installed in the new Y-pipe for visual purposes. The O2 sensors that matter are the ones after the manifolds, before any cats, and the headers will have bungs for these in place.
