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Longtube primaries too big??

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Old 05-08-2014, 01:51 PM
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Default Longtube primaries too big??

I've got an 04 tahoe 5.3

212/218 low lift cam
CAI
BB tune
And 1 3/4" longtubes with a 2.5" collector.

Did I go too big on my primary size for my mods? I sorta feel like I've lost some low end (which SUCKS in a tahoe...) but I'm also not retuned. Do I need to step down to 1 5/8"? Any suggestions?
Old 05-08-2014, 02:58 PM
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1 3/4 with a 3" collector is what most run. i think a retune will help a lot.
Old 05-08-2014, 03:11 PM
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Well I did a search (like I'm supposed to but didn't at first, stupid me) on my style headers and actually found out that people were posting the O.D. Of the primaries rather than the I.D. So in the end, I believe I have 1 5/8" primaries into a 2.5" collector and 3" at the end of the ORY to catback.

Maybe it's the 2.5" collector i need to be more concerned about, but I will definitely get her tuned up again. Sorry for the junk thread I made for anyone who reads!
Old 05-08-2014, 03:15 PM
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yes get a retune and report back.

maybe a higher stall torque converter
Old 05-08-2014, 04:42 PM
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I assume you have the OBX headers... there was a lot of that ID/OD talk floating around about them.

1) they are a 1 3/4" header
2) They arent too big
3) you need a retune
4) you may feel a small loss in low end (i'm talking very low end like tip in with the converter locked at 50 MPH)

If you really did lose power there just get used to dropping it into 3 and you will be in a more meaty part of the power curve with more power than stock. I would think that cam makes more power as low as 2000 or 2500 RPM. My guess is that your dynamic compression is slightly lower so it'll eat more timing down low which will help bump the bottom end back up.
Old 05-09-2014, 01:47 PM
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Well they are the eBay brand. However, they're based off the OBX headers/old dynatechs with the hump on drivers side.

I'll get it tuned. Hoping to possibly buy a verter in the near future. Any recommendations for a heavy beast like my tahoe?
Old 05-09-2014, 06:00 PM
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i have a 2000 tahoe with very similar mods, BB tune, Same headers, 216/220 cam, efans servo nd CAI, i noticed a better gain once i tuned after the headers which im sure you will too as far as converter i will order this week a FTI 3200 converter which is what has been recommended to me by fti. that or the FTI 3000 converter
Old 05-09-2014, 11:27 PM
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I'm sure I'll go 3000+ verter in the future. I still need to tune for the headers.

Ended up going to track tonight with my buddy and his TT rumble bee. With a CAI, 212/218 low lift, long tubes, and BB tune (needs new tune) and ran a 10.8 in the 1/8 mile. 60' was 2.6...

Numbers seem bad or good? My first time ever at the track.
Old 05-10-2014, 01:09 AM
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those numbers seem pretty good to me! whats the elevation at your track? mine is 5600 ft which affects my times bad..but my best 1/8th so far is 11.2 with a 2.7 60'
Old 05-10-2014, 01:11 AM
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Central iowa. Not sure on elevation, but definitely not up there!

Gonna have to tune her and take it back within the next few weeks

Was gonna run against a Nbs Denali 6.0, but my buddies truck decided to take a dump so we had to push...


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