TPITuned Port Injection discussion and questions. LB9 and L98 tech, porting, tuning, and bolt-on aftermarket products.
Welcome to ThirdGen.org!
Welcome to ThirdGen.org.
You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, join the ThirdGen.org community today!
I need a little help in picking out some gears for my application. I am running a stock intake but hope to upgrade to the TPIS big mouth intake and runners in the next year or so. Currently the ZZ-9 cam runs pretty good up top. But in the lower end of the rorque curve it bogs a fair bit. My buddy suggested I put in a shorter gear set (like maybe 4.11 or 3.73). This car will never go to the track and is more of a streeter than anything.
Will these gears be alright or will I be greatly disappointed. I currently have 2.73 in there and I think this is why the bog might be occuring.
__________________ 1989 IROC-Z, 355, 4-bolt main, stock TPI intake, roller rockers, forged steel crank, ZZ-9 cam, 700R4, 1-3/4" SLP headers, 1227165 ECM, Prominator, 'in dire need of a good tune....'
You won't need a lot of gear with a LTR intake and that cam. I'd go with 3.23 or 3.42 if you have the 10 bolt or 3.27 or 3.45 if you have the 9 bolt. ZZ9 is not that wild so you should be able to tune out any bogging on the low end.
__________________ 89 Formula 350, Accel Tri-Ys, Jacobs box, Probuilt tranny, Vigilante 2600, Dana 44 w/3.54, Spohn (Tq arm, LCAs, Panhard rod), Global West subframe connectors, DIY PROM, stock cam, heads, runners, base 13.55/97.4 (1/05)
So you figure 3.73 gears would be terrible with my setup?? The reason I am asking is because I think I can get my hands on a set for free, but I don't want to install them if I will be unhappy with them. Thanks for the input!
3.73 aren't terrible and you can't argue with the price. They'd be great for in-town driving with the right tires and suspension set-up. It's just that a LTR TPI with stock heads is going to make peak power below 5000 RPM so you'll run out of breath on the top end in a 1/4 mile race. It will pull great down low if you can hook it up.
I'm running the combination you are talking about except I have higher flowing heads and intake system to take advantage. I think Mark has pretty well nailed it for your situation. For a street machine that never sees the track I would opt for the 3.2x gears depending on what rear end you have.
__________________ Best of 11.57 and 115.73 mph(1811DA). Motor: Dart SHP block 368ci, AFR Comp 195cc heads, 11.1:1 comp, highly modified TPI 1st style SLP runners, moded GM plenum and First Injection TPI intake manifold, Mike Jones 3/4 race cam, Yank PT4000 converter, Dyno Don 1 3/4" shorty headers, Dyno Don custom exhaust, custom cold air intake, AS&M monoblade throttle body. Meziere electric water pump. Mufflex 3.5" exhaust catback. Magnaflow 3.5" muffler#12909. Kevin91Z Tune. 4L60E installed. Now 420RWHP, 417RWTQ with new motor.
