Stock Runners? Modified 355
#1
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Car: 86 IROC-Z
Engine: 355
Transmission: T5
Axle/Gears: 3.23
Stock Runners? Modified 355
Im in the process of putting a tpi back on my 86 iroc. The original engine was removed(305 tpi), and I put 355 with high flowing heads and a moderate hyd roller cam in its place. I am trying to figure out if I need to go with better flowing runners.(slp?) I have upgraded the injectors (22lb) and am programming a chip to match. I have a holley 670 carb that seems to be well matched to the engine, but am excited to get the tpi back on.
Sorry if youve had to answer the same kind of question a bunch of times, but any advice would be much appreciated!
Sorry if youve had to answer the same kind of question a bunch of times, but any advice would be much appreciated!
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Car: 86 IROC-Z
Engine: 355
Transmission: T5
Axle/Gears: 3.23
Re: Stock Runners? Modified 355
Yeah, ive heard that the runners were the most restricted part of the top end. The cam Im running has 206-212 duration and 480-487 lift. With the carb Im getting power up past 6000rpm, Im hoping to get good flow from the tpi and not lose the top end power.
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Car: GTA
Engine: 350 TPI
Transmission: 700R4
Axle/Gears: Aussie 9-bolt/3.27 posi
Re: Stock Runners? Modified 355
The stock top end can support 400hp/500ft lbs, You think you'll exceed that with the 355?
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Car: GTA
Engine: 350 TPI
Transmission: 700R4
Axle/Gears: Aussie 9-bolt/3.27 posi
Re: Stock Runners? Modified 355
More like 4750/5000, but it comes down to the Owners desired usage of the vehicle. On the street, 4500 is plenty. For drag racing higher rpms might be. But a higher rpm range also costs you bottom end torque.
For a primarily street car, I'd gladly sacrifice the above 4500rpm horsepower to gain bottom end torque. For the drag strip I'd go for rpms too.
I constantly see people quick to dismiss TPIs rpm range when no consideration is given to the intended usage.
For a primarily street car, I'd gladly sacrifice the above 4500rpm horsepower to gain bottom end torque. For the drag strip I'd go for rpms too.
I constantly see people quick to dismiss TPIs rpm range when no consideration is given to the intended usage.
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Car: 1988 Iroc
Engine: 5.7L
Transmission: '96 T56, Hurst Shifter, Mech VSS
Axle/Gears: 3.45 9 Bolt
Re: Stock Runners? Modified 355
I think a FAST TPI intake would work well with your combo. It will allow you to keep that low end torque, but let you breath uptop and not waste your cam. Your set up with that intake and a spot on tune will make a really fun street car that should be easily into the 12's.
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Car: 86 IROC-Z
Engine: 355
Transmission: T5
Axle/Gears: 3.23
Re: Stock Runners? Modified 355
Thanks for the info guys. I forgot to mention that my heads have been ported and polished too. Ive been trying to find cfm specs on the stock runners compared to slps. Im wondering how much of a difference bigger runners can make? What is a Fast TPI intake?
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Car: 91' Firebird SOLD
Engine: 350 TPI +bolt-ons
Transmission: 700r4
Axle/Gears: 3:42
Re: Stock Runners? Modified 355
are u keeping the 273's? then if you are you better go for a low end torque street car. How are u using the vehicle? track only? street?
#10
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Car: 86 IROC-Z
Engine: 355
Transmission: T5
Axle/Gears: 3.23
Re: Stock Runners? Modified 355
I would love to change the rear end gears to 3.73s, or 3.42s. Its just a street car, but not a daily driver. I feel like the gears are way too high right now. Do you guys think that upgrading the runners sacrifices low end torque?? I am just kind of wondering the difference in performance between stock and aftermarket runners, and I guess trying to confirm that they are the most restrictive part of the intake? Maybe someone has done this upgrade and was happy or unhappy with the results?
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Car: 1989-92 FORMULA350 305 92 Hawkclone
Engine: 4++,350 & 305 CIs
Transmission: 700R4 4800 vig 18th700R4 t56 ZF6 T5
Axle/Gears: 3.70 9"ford alum chunk,dana44,9bolt
Re: Stock Runners? Modified 355
Unported the SLPs will show very little gain. You have to port the !!!! out of them to be worth it. then you need a bigger or ported base.
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Car: 1987 Trans Am
Engine: 5.0L TPI
Transmission: 700R4
Axle/Gears: Richmond 3.73
Re: Stock Runners? Modified 355
The heads are your biggest bottle neck with the TPI motors. You have updated heads so I think you will see nice gains. I have the Edelbrock intake set up on mine. And I'm pretty happy.
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Car: 91' Firebird SOLD
Engine: 350 TPI +bolt-ons
Transmission: 700r4
Axle/Gears: 3:42
Re: Stock Runners? Modified 355
I would love to change the rear end gears to 3.73s, or 3.42s. Its just a street car, but not a daily driver. I feel like the gears are way too high right now. Do you guys think that upgrading the runners sacrifices low end torque?? I am just kind of wondering the difference in performance between stock and aftermarket runners, and I guess trying to confirm that they are the most restrictive part of the intake? Maybe someone has done this upgrade and was happy or unhappy with the results?
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Car: 91' Firebird SOLD
Engine: 350 TPI +bolt-ons
Transmission: 700r4
Axle/Gears: 3:42
Re: Stock Runners? Modified 355
i think your looking at like 10hp on a stock motor and they cost $300+.
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Car: 1987 Trans Am
Engine: 5.0L TPI
Transmission: 700R4
Axle/Gears: Richmond 3.73
Re: Stock Runners? Modified 355
Before you look into a gear in the rear end, think about the cost. You probably have a series 2 carrier. Series 2...you can only go to a 3.08 gear....its not worth the $$ in my opinion.
Anything more then that your going to have to jump to a series 3 carrier. And if your going to be spending the $$ I would go with 3.73....I have had them in my car for 6 years...wouldn't change a thing! People who think 3.42's are the best....haven't driven a car with 3.73's LOL!!
Anything more then that your going to have to jump to a series 3 carrier. And if your going to be spending the $$ I would go with 3.73....I have had them in my car for 6 years...wouldn't change a thing! People who think 3.42's are the best....haven't driven a car with 3.73's LOL!!
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Car: 91' Firebird SOLD
Engine: 350 TPI +bolt-ons
Transmission: 700r4
Axle/Gears: 3:42
Re: Stock Runners? Modified 355
you can pick up a used rear for $150 from a junkyard. Sometimes with 342 or 323's in them. I remembering reading an article on a 91' TPI car that went from 342 to 373 and gained nothing. Maybe a better 60ft time.
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Car: 91' Firebird SOLD
Engine: 350 TPI +bolt-ons
Transmission: 700r4
Axle/Gears: 3:42
Re: Stock Runners? Modified 355
Before you look into a gear in the rear end, think about the cost. You probably have a series 2 carrier. Series 2...you can only go to a 3.08 gear....its not worth the $$ in my opinion.
Anything more then that your going to have to jump to a series 3 carrier. And if your going to be spending the $$ I would go with 3.73....I have had them in my car for 6 years...wouldn't change a thing! People who think 3.42's are the best....haven't driven a car with 3.73's LOL!!
Anything more then that your going to have to jump to a series 3 carrier. And if your going to be spending the $$ I would go with 3.73....I have had them in my car for 6 years...wouldn't change a thing! People who think 3.42's are the best....haven't driven a car with 3.73's LOL!!
#18
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Car: 86 IROC-Z
Engine: 355
Transmission: T5
Axle/Gears: 3.23
Re: Stock Runners? Modified 355
Before you look into a gear in the rear end, think about the cost. You probably have a series 2 carrier. Series 2...you can only go to a 3.08 gear....its not worth the $$ in my opinion.
Anything more then that your going to have to jump to a series 3 carrier. And if your going to be spending the $$ I would go with 3.73....I have had them in my car for 6 years...wouldn't change a thing! People who think 3.42's are the best....haven't driven a car with 3.73's LOL!!
Anything more then that your going to have to jump to a series 3 carrier. And if your going to be spending the $$ I would go with 3.73....I have had them in my car for 6 years...wouldn't change a thing! People who think 3.42's are the best....haven't driven a car with 3.73's LOL!!
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Car: 1987 Trans Am
Engine: 5.0L TPI
Transmission: 700R4
Axle/Gears: Richmond 3.73
Re: Stock Runners? Modified 355
It's not like hes going to the track racing every week. Hes an in town driver who like the streetlight to street light race. Or likes the feel of goosing the gas pedal off the start.
You want to get even better throw a little stall in it. Do some research, a stall out of a S10 truck / blazer bumps up the stall a little, that's cheap too. And that's just a stock GM converter. I think our cars stall around 1200 this bumps it up to 1700.
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Car: 82 Z28
Engine: 383 SP EFI/ 4150 TB
Transmission: T400
Axle/Gears: QP 9" 3.73
Re: Stock Runners? Modified 355
In 1st gear ,2.73 rear w/ T700 is equal to old skool 3spd auto with 3.4's
3.42 is equal to old skool auto w/ 5.10's
Probably running out of top end w/TPI
Last edited by vetteoz; 02-15-2012 at 07:44 AM.
#22
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Car: 1987 Trans Am
Engine: 5.0L TPI
Transmission: 700R4
Axle/Gears: Richmond 3.73
Re: Stock Runners? Modified 355
https://www.thirdgen.org/forums/tran...4-11-whos.html
here is a link to the mph / rpm's it shows 3.73's also
Last edited by tenpin842; 02-15-2012 at 07:56 AM.
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