6.2L Swap 08 Sierra. Interesting stuff.
04-01-2015, 08:14 PM
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6.2L Swap 08 Sierra. Interesting stuff.
So I recently (11/14) swapped a 6.2L bottom end into my 2008 GMC Sierra Crew Cab. See here for the initial thread I started at the time: https://www.performancetrucks.net/fo...1500-a-533520/
I put some headers on it this past weekend finally and have been tweaking the tune to get things right in the AFR department and have noticed a couple of things.
1) Either I have an exhaust leak after the header install, or headers just really sound incredibly loud under load on these trucks. I can hear a very fast rattling noise almost like a misfire at WOT that drives me a bit batty because I cant figure out what it is. Retorqued header flanges...new gaskets...retightened all clamps....etc. Scanned for KR and misfires and nothing. Truck pulls like crazy, but just makes an annoying noise. I tried multiple times to get video, but the noise doesn't seem to come through.
2) I have not changed the WOT shift points and notice its shifting at like 5400 RPM. Seems incredibly low to me. My GTO shifts at 7K. I guess I never really noticed the stock shift points were so low. I have BTR springs, pushrods, and a Tick cam in it, so I plan on raising this a BUNCH....but....
3) My injectors are at 100% duty cycle with a 12.8:1 AFR at WOT at only 5400 RPM. Guess I'm in the market for some bigger injectors. Anyone know how much HP the stock injectors support? I can prob lean it out some but if you take the generally accepted max of 80% duty cycle into consideration, I'm going to need at least 36 lb/hr injectors just to be able to hit 6500 RPM in this thing.
All in all I am incredibly happy with the results, just want to get that noise issue worked out and get some injectors so I can wind it out a bit.
I put some headers on it this past weekend finally and have been tweaking the tune to get things right in the AFR department and have noticed a couple of things.
1) Either I have an exhaust leak after the header install, or headers just really sound incredibly loud under load on these trucks. I can hear a very fast rattling noise almost like a misfire at WOT that drives me a bit batty because I cant figure out what it is. Retorqued header flanges...new gaskets...retightened all clamps....etc. Scanned for KR and misfires and nothing. Truck pulls like crazy, but just makes an annoying noise. I tried multiple times to get video, but the noise doesn't seem to come through.
2) I have not changed the WOT shift points and notice its shifting at like 5400 RPM. Seems incredibly low to me. My GTO shifts at 7K. I guess I never really noticed the stock shift points were so low. I have BTR springs, pushrods, and a Tick cam in it, so I plan on raising this a BUNCH....but....
3) My injectors are at 100% duty cycle with a 12.8:1 AFR at WOT at only 5400 RPM. Guess I'm in the market for some bigger injectors. Anyone know how much HP the stock injectors support? I can prob lean it out some but if you take the generally accepted max of 80% duty cycle into consideration, I'm going to need at least 36 lb/hr injectors just to be able to hit 6500 RPM in this thing.
All in all I am incredibly happy with the results, just want to get that noise issue worked out and get some injectors so I can wind it out a bit.
04-04-2015, 12:30 PM
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Well, the noise was an exhaust leak. New clamps and some Permatex muffler and exhaust sealant at the joints fixed it. Sounds awesome now.
Bought some LSA injectors for $125 on Ls1tech. Smoking deal. So my injector duty cycle issue will soon be a thing of the past.
Coming right along
Bought some LSA injectors for $125 on Ls1tech. Smoking deal. So my injector duty cycle issue will soon be a thing of the past.
Coming right along
04-05-2015, 07:27 AM
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Still using the stock 5.3 intake manifold and TB with 317 casting cathedral port heads. The heads were cleaned up with a valve job and BTR springs, but otherwise stock. I know how much flak I'll get for THAT little tidbit. LOL.
Realistically, this was going to be a very mild build from the beginning and I wanted it to be 87 octane friendly since it is a DD. Didn't want to spend the cash for rectangle port heads/intake. The short block only cost me $1500, then the cost of some lifters, cam, pushrods, and timing set. With heads and all, I probably have $2500 in the swap. I just made sure the cam would compliment the heads and went with it...
I'm a bit irritated with that exhaust leak right now. After I posted the above, we drove around town a bit, and by the time we got home, it was leaking again. Going to try a couple more tricks I read about like aluminum foil wrapped around the joint and maybe a stepped style band clamp. If that doesn't do it, I'll weld the damn things on. I hate exhaust leaks.
Realistically, this was going to be a very mild build from the beginning and I wanted it to be 87 octane friendly since it is a DD. Didn't want to spend the cash for rectangle port heads/intake. The short block only cost me $1500, then the cost of some lifters, cam, pushrods, and timing set. With heads and all, I probably have $2500 in the swap. I just made sure the cam would compliment the heads and went with it...
I'm a bit irritated with that exhaust leak right now. After I posted the above, we drove around town a bit, and by the time we got home, it was leaking again. Going to try a couple more tricks I read about like aluminum foil wrapped around the joint and maybe a stepped style band clamp. If that doesn't do it, I'll weld the damn things on. I hate exhaust leaks.
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