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Old 05-03-2004, 03:44 PM   #1
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Why is the L98 so low in HP

Im wonderin i own a L98 and it came 245 hp (has 13k org miles) But has 345lbs of torque which alot for stock much more the the Lt1... Now why did GM make it soo low hp but a good number of torque?? Does ths make the l98 a slow engine with this kinda hp???. Im talkin bout the 350 not the 305..... I dunno my car is low mileage and mint and never drive it...... Im just wondering why GM made it a low hp engine?
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Old 05-03-2004, 03:48 PM   #2
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Quote:
why GM made it a low hp engine?

I ask myself that everyday...
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Old 05-03-2004, 03:49 PM   #3
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!

TPI. That's why. TPI is good for torque, that's why the number is rather high, but try to go up on those RPM's and you will see the power start to take a dive. Strap on a Stealthram intake and you will see high RPM capability -- the way no O.E. TPI system will ever be able to provide you.

Hope that helps.
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Old 05-03-2004, 04:56 PM   #4
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Because they went with TPI because it looks so damn cool.

Nah jk but who cares when you have all that torque, and you have so many options to go with higher HP numbers with other inductions.
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Old 05-03-2004, 07:32 PM   #5
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It is indeed the TPI setup. They really went for a torque combo with the heads and cam. I agree tho, they fall short on horsepower EVEN IF they intended to focus on torque.
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Old 05-04-2004, 12:18 AM   #6
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good enough for 13s with just suspension and exhaust who needs horsepower :lala:
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Old 05-04-2004, 12:19 AM   #7
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Well the power output characteristics of the L98 are determined by more than just the intake. The stock heads, stock cam, and stock exhaust play a big role in that low HP, high TQ output. But if you're focusing on the intake, it has to do with the runner length. Different length runners give you different powerband characteristics. TPI is a long tube runner type of intake, commonly refered to as a LTR setup. LTR setups give you badass torque, but less than exciting high end HP. The LT1 intake on the other hand has shorter runners, so it makes more HP up top. Same thing with the Holley StealthRam. If you want more top end power, an intake change to a short runner type of setup is a good idea, but dont forget about the heads, cam, and exhaust too. Things need to be matched up to get the most potential. My stock L98 setup falls on its face around 4500-4800 RPM. I've been told that this is not a direct result of the TPI intake, but more a result of the stock cam and exhaust. With better matched components, the TPI can pull strong to 5000+ RPM and other members here have proven this. But the TPI will never have the high end capabilities of the short runner style intakes like the LT1, SealthRam, or MiniRam. My goal for now is to get my L98 to pull hard to 6000 RPM. I plan to do an intake change (to the StealthRam), a cam/valvetrain change (blower cam), and an exhaust change (SLP 1 3/4ths to 4" Mufflex setup w/ Mufflex Y-pipe). I'm expecting this to majorly boost the ammount of HP my combo makes (and since its boosted it will be much more pronounced). But the stock heads will still be holding me back ...
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Old 05-04-2004, 12:34 AM   #8
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Couldn't you get higher end power out of your TPI engine with not only a matched cam, heads and exhaust but also with a better intake manifold, high flow runners, bigger TB and ported pluenum? I noticed with just my cam (268* comp cam) with everything else stock except muffler, cat. and custom chip my power already increased a little in the upper RPM. So instead of the engines power dying at 45-4800RMP its now up to 5200RPM and thats just with a cam and the other small mods.
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Old 05-04-2004, 06:38 AM   #9
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Definately. If you want to stick with a LTR intake then go for it.
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Old 05-04-2004, 07:16 AM   #10
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Re: Why is the L98 so low in HP

Quote:
Originally posted by nick418
Im wonderin i own a L98 and it came 245 hp (has 13k org miles)
See this thread.

245 fwhp does seem low as compared to the later LT1 and LS1 engines, but the L98 & TPI v8 induction was designed in the early 1980s; age-wise they aren't close. And 245 hp in a 3500 lb car means low 14s in the Vette, which was plenty fast for its day. HTH.
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Old 05-04-2004, 08:23 AM   #11
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Re: Re: Why is the L98 so low in HP

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Originally posted by kdrolt
See this thread.

245 fwhp does seem low as compared to the later LT1 and LS1 engines, but the L98 & TPI v8 induction was designed in the early 1980s; age-wise they aren't close. And 245 hp in a 3500 lb car means low 14s in the Vette, which was plenty fast for its day. HTH.
I agree and add:
For the Eighties that 220/245 was high Horsepower. You have to remenber if you can the average car in those years had less then 150 HP. So for those years the 305/350 TPI were high performance engines and Can Not be compared to today cars.
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Old 05-04-2004, 01:00 PM   #12
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i deff agree with u guys 100 percent! But there engines these days that still cant touch the L98S torque, i dont think hp is everything but its a very significant role for a car. Like FormulA said Theres quite of few l98s that can easily hit high 13s with a few upgrades and i seen it on my cuzins 90 ROC. He added a chip, exhuast and a couple other things and was hittin mid 13's!! So i still think the L98 should get the respect.. In my opinion as much as i maybe sound stupid i would take a L98 over a LTI.. i Dunno i love em and i grew up with them.. My father owned a L98 86 VETTE b4 i was born, my other cuzin owned a T/A with a L98, my cuz steve owned a 90 ROC (junk yard ) And also my friend owned the first TPI ever (1985) corvette.. I was born with this engine ,rem 70% of u guys are probably over 30 yrs of age.. Im still a lil kid heheh, the TPI came out 19yrs ago.. wow
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Old 05-04-2004, 01:02 PM   #13
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o yeah as much as engine appearance doesnt mean nothin but performance, i think the l98 TPI was one of the hottest lookin engines that GM ever made.. Somethin bout the looks of it that gets me the goosebumps
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Old 05-04-2004, 01:04 PM   #14
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o yeah as much as engine appearance doesnt mean nothin but performance


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Old 05-26-2004, 10:44 PM   #15
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who cares about hp? torque is what makes a fun street car. as my good friend corky bell put it, you drive torque, but you buy hp(or something like that). of course, you need hp to get track numbers, but that torque sure is fun.

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Old 05-27-2004, 01:43 AM   #16
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Quote:
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o yeah as much as engine appearance doesnt mean nothin but performance, i think the l98 TPI was one of the hottest lookin engines that GM ever made.. Somethin bout the looks of it that gets me the goosebumps
Absolutely! The HSR, MiniRam, Super Ram, LT1, etc. look rather boring compared to the L98/LB9 IMO. I think that is what sold me on my '85 Z28. I had previously owned 2 carbed 3rdgens ('82 SC and '83 Z28) but the look of the TPI was (and still is) so high tech! So why did I buy a '91 RS? The looks of the car itself.
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Old 05-27-2004, 07:57 AM   #17
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seems like the way the Lt1 engine looks it would be the L98 and the mean lookin l98 would be the Lt1
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Old 05-27-2004, 02:05 PM   #18
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Do you really need very high rpm's to make big power?

I know the more rpms means more air and fuel to burn to make power but TPI can make good horsepower down below 5000 rpm with the right equipment right?

Most cars with LTR TPI's are primarily street driven anyway and most situations won't allow for hitting over 5000 rpms.

A 6000 rpm powerband would be sweet but on the street, lower rpms is better for drivability and fun factor. But I got to admit that the sound of 6K+ rpms running through my 80 series flowmaster or a spintech would sound awesome

nothing looks better than a chromed or fully polished TPI LTR setup. Seen one in a 40's truck and it was one of the finest motors I ever seen.:hail:
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Old 05-27-2004, 02:06 PM   #19
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The beauty of the whole thing is if you bolt a blower on a L98/LB9 you get the torque down low, and the supercharger/turbo will give you the horsepower up high. Makes for a fun street setup.
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Old 05-30-2004, 01:47 PM   #20
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Quote:
And 245 hp in a 3500 lb car means low 14s in the Vette, which was plenty fast for its day. HTH.
actually there have been plenty of Vettes that have hit high 13s in them 100% bone factory stock (including my own). with just boltons, these TPI Vettes have hit mid - high 12s. theres a guy on corvetteforum.com that has a 89' Vette with just about every bolton and runs 12.70 at 108mph. hes never even lifted a valve cover. cant wait to see what kinds of #s he puts up with new heads and cam

BTW- C4 Vettes (non-verts) typically weigh 3300lbs, not 3500
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Old 05-30-2004, 06:43 PM   #21
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yeah my dad owns a 1986 Vette which he did hit high 13s with just a chip and exhuast and lifted the valve covers.. Yeah these cars didnt come with the best hp but had a hell of alot of torque and were very fast for there day and still are if u think about..
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Old 05-30-2004, 07:15 PM   #22
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My L98 camaro ran 13.58@99mph with 3.73 gears, K&N filters, BFG drag radials and a 2200 convertor. Never had the valve covers off
The key for the track is traction, and even more so when you have no high end. While the torque is fine on the street, it will likely lose more races than it will win, due to tire spin.

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Old 05-30-2004, 07:25 PM   #23
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My L98 camaro ran 13.58@99mph with 3.73 gears, K&N filters, BFG drag radials and a 2200 convertor. Never had the valve covers off \



u ran 13.5? seriously?
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Old 05-30-2004, 07:59 PM   #24
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Quote:
Originally posted by nick418
My L98 camaro ran 13.58@99mph with 3.73 gears, K&N filters, BFG drag radials and a 2200 convertor. Never had the valve covers off \



u ran 13.5? seriously?
Yep,
1.8 60ft. Traction is KEY.
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Old 05-30-2004, 08:48 PM   #25
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yup traction is very much key at the track, use that torque; cause there is on top end
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Old 05-30-2004, 09:34 PM   #26
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so l98s can hit 13s easilly with trac..nice, my maro is a l98 and the org own hit 14.1 wit exhuast and chip and airfilter.. My dads Vette hit 13.8 or 13.7 cant rem, with the same exact mods on mine, i think the l98 is way underrated engine that doesnt get much respect like the Lt1s and Ls1, Yeah well wasnt the Lt1 design org from some parts of the L98? And some good mods with the l98 it can easily be caught up with the Lt1 (hp) But in the Torque dept, the Lt1 is owned. i hear everyone say that after 50 the l98 dodges down with power, it seems like my MARO and my Dads vette doesnt do this...... My dad hit eaily 140mph down RT 95 . ANd i hit 120 very easily as well...... I dunno it doesnt seem to hav prob with me
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Old 06-01-2004, 03:08 PM   #27
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cleaner air , and insurance purposes , yes the tpi was designed fro a 305 but with better heads and cam , and exhaust those cars could be real fast

in the 80's early 90's 245 hp is all they would let for power out. now a days there is no limit to power , also insurance don;t care either anymore
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Old 06-01-2004, 09:22 PM   #28
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I still think the L98 is one of the greatest engines GM built..
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Old 06-01-2004, 09:22 PM   #29
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I always had good performance and great luck with them
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Old 06-16-2004, 01:24 AM   #30
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im sorry but the TPI is absolutly the best looking intake possible, especially chromed. ever been to a carshow, look around at the old hotrods and such, the majority are running with tpi setups. and if you arent looking for serious power or a lot of track time you just cant beat a tpi for running around town, hell even in my 305 its a blast.

now im switching to a stealthram because im getting a little more serious with my car but for some reason i think ill take this 305 and go get me another cheap 91/92 TBI car to do a cheap swap.....daily driver!!!
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Old 06-17-2004, 12:09 PM   #31
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Yea i love the looks of the TPI engine, and despite the naysayers i think the L98 is just fine on the top end.... If i ever manage to get my Super Ram machined and see if it even fits on my car it better make a big impression on me or im goin back!
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Old 05-11-2006, 03:01 AM   #32
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so if i was to get a tpi and put it on my crate engine will it kill my horse power??? it comes 330 horse 380 torque out the box.
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Old 05-11-2006, 03:39 AM   #33
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brought this one back from the dead didnt we? Yes the stock TPI intake will be rather restrictive on that engine. There are however many options to make it flow better. I.e. porting and siamesed runners. And again the 350 was just as retricted by a crappy oem exhaust and heads/cam designed specifically for mind blowing torque.

A modified LTR intake would however make for a fun street/strip ride with that long block
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Old 05-11-2006, 08:55 AM   #34
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I love TPI for its looks and the way it performs, but I just got sick of that
700r4. Yes call me a traitor but I went for a LT1, mainly for the T56 but also cause it will make more power up top and being able to use the OBD1 is nice for trouble shooting problems. I took my TPI setup off its complete if anyone wants it send me a PM.
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Old 05-11-2006, 02:33 PM   #35
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Quote:
Originally Posted by rocluvr0013
brought this one back from the dead didnt we? Yes the stock TPI intake will be rather restrictive on that engine. There are however many options to make it flow better. I.e. porting and siamesed runners. And again the 350 was just as retricted by a crappy oem exhaust and heads/cam designed specifically for mind blowing torque.

A modified LTR intake would however make for a fun street/strip ride with that long block

I disagree.

I am running the ZZ4 camshaft ( sam as that 330 hp engine) stock heads , ported TPI setup , with the stock iron heads . without a tune I got 251 rwhp . LS1's were down 10 hp that day ( hot out) so I figure I had 260 hp to the wheels . Now when I get it tuned I may pick up 5-10 hp there. It all works out to be pretty dam close to the origonal 330 hp . useing a 15 % drivetrain loss. But I will have definately more TQ
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Old 05-11-2006, 07:01 PM   #36
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Originally Posted by D's89IROCZ
I disagree.

I am running the ZZ4 camshaft ( sam as that 330 hp engine) stock heads , ported TPI setup , with the stock iron heads . without a tune I got 251 rwhp . LS1's were down 10 hp that day ( hot out) so I figure I had 260 hp to the wheels . Now when I get it tuned I may pick up 5-10 hp there. It all works out to be pretty dam close to the origonal 330 hp . useing a 15 % drivetrain loss. But I will have definately more TQ
Thats why i said stock. Porting can and will make a big difference.

Especially since your on a stock (or untuned anyways) computer. 280 to the wheels would put you @ 330 fly (roughly assuming 15% loss) So yes you are very close to those numbers and with stock heads? Thats impressive. Where are you making peaK power? somewhere in the 4500 range i assume? (just curious)
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Old 05-11-2006, 08:33 PM   #37
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Lets take the LT1 for instance. It makes what, 285 hp 310 lb ft tq? at what rpms? 5200, 4000, something like that, im not an lt1 goer. Or you can drive a 230-250 hp L98 with 330-350 lb ft tq. 30-40 lb ft tq is much more fun on the street than 40 hp. Granted you may not run as fast in the 1/4, but the 1/8 is just as fast, if not faster. Get an L98 and do some simple bolt ons, pull it into 1st and cruise at 20 mph and then hammer it, youll never ditch tpi. It does some nasty brakestands. Plus, who the hell revs their car to 5000+rpm on the steet anyway? Thats just asking for some valve float and ignition issues. Btw, with so much low end grunt, you barely have to stay on the gas to lug up hills, thus maximizing fuel economy. My L98 even with its mods and no tune can get 18 mph in town and 25 on the highway.

I run withing .1 of the LS1 cars here in the 1/8th

The only car I would suggest redlining daily is a 93 geo prizm 1.6, i can't blow the damn thing up. Left my foot on the floor for 10 minutes, didn;t even go over 220 degrees. I'll drop a chevy 350 (yes tpi) into it if the little 1.6 ever blows up. Untill now ill enjoy 30 mpg in the geo.
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Old 05-11-2006, 09:15 PM   #38
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I dont think the low hp rating of the L98 is beacuse of the tpi intake. I think that performance was down for third gens beacuse of the gas shortage problems durning the time these engines were made. More power=more gas. Just a theory lol. L98 engines do not exactly have a great heads/cam combo. So you really cant just blame the intake.


Forgot about how tough the emmision laws were in the 80's as well. Rough time for performance.

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Old 05-11-2006, 09:23 PM   #39
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THat is hillairous! Good stuf. Want more horse out of a stock L98 change your cam or better yet heads too. Theres allways more cubes and lots of money$$$$$$$. Did it myself, $6000.00 ruffley later to create 496hp & 547 lbs torque at the WHEELS!! Have fun. ( not by any means a stock nothing)
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Old 05-12-2006, 07:56 AM   #40
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No one has stated the obvious and proven reason.

TPI was designed for 305 engines and was an afterthought on 350's.

Truth hurts, just imagine the power and torque we would have had, had the TPI setup been designed in total with a 350 in mind in the first place.

Also go to remember the Big Three here in the 80's had nothing good to speak off. The turbo 3.8 was ok :-) But nothing else was considered amazing off the show room floor. I mean seriously think 80's and fast, u have TPI F bods, 5.0 Fords and 3.8T, thats it.

It was the end of the band aid era to improve econonmy and emissions. Everything else after the TPI engines was new, they didnt need to use crutches like poorly designed EGR and small avg flowing heads. Modern designed cyl heads and better injectors to better ecm;s.

Still, TPI makes me smile more than almost any other car u drive cause a little blip off the pedal and the car lunges :-)

later
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Old 05-12-2006, 09:39 AM   #41
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Quote:
Originally Posted by 3.8TransAM
No one has stated the obvious and proven reason.

TPI was designed for 305 engines and was an afterthought on 350's.

Truth hurts, just imagine the power and torque we would have had, had the TPI setup been designed in total with a 350 in mind in the first place
even though the intake was designed for a 305... it still flows more air than the heads they put on the 350

its the heads/cam combo more than the intake setup that restricts hp in these cars
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Old 05-12-2006, 10:07 AM   #42
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I've heard of people putting 305 heads on a 350 is there any truth to this helping at all ?

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Old 05-12-2006, 10:16 AM   #43
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The LT1 is not in any way short on torque; 97' 285hp 325ftlb of torque thats actually just 20ftlb of torque difference. Im not trying to take away from TPI at all Im just saying that the LT1 is also up there in torque. The LT1 doesnt need to rev to 5k to get its advantages.
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Old 05-12-2006, 10:31 AM   #44
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Quote:
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The LT1 is not in any way short on torque; 97' 285hp 325ftlb of torque thats actually just 20ftlb of torque difference. Im not trying to take away from TPI at all Im just saying that the LT1 is also up there in torque. The LT1 doesnt need to rev to 5k to get its advantages.
how true. my 93' LT1 dynoed 266/306 rwhp/tq which equals about 312/360 at the flywheel. also, the LT1s torque peaks at 2400rpms... 600 rpms SOONER than a L98... and as the final blow its 300+rwtq curve doesnt start to fall till around 4500rpms
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Old 05-12-2006, 10:33 AM   #45
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HAS ANYONE SEEN THIS WEB SITE!!!! WWW.CORVETTEPLENUM.COM. I LIKE THE TPI SET UP, AND WANT TO KEEP MINE AS STOCK LOOKING AS POSIBLE. ON THE WEB SITE THE GUY STATES GAINS LIKE A HSR!!!! TAKE A LOOK AND LET ME KNOW WHAT YOU GUYS THINK!
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Old 05-12-2006, 12:42 PM   #46
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Quote:
even though the intake was designed for a 305... it still flows more air than the heads they put on the 350

its the heads/cam combo more than the intake setup that restricts hp in these cars
That doesnt exactly apply.

True head flow is only achieved when an intake that has 10-20% more airflow than the head it is bolted to.

In that apsect of intake design TPI fails when compared to the 350 heads and is marginal on the 305 heads.
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Old 05-12-2006, 03:51 PM   #47
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So if a tpi on my crate will kill my horse what should i get for a FI system. SOme guy told my about a pro-jection system from holley, r those any good?
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Old 05-12-2006, 08:25 PM   #48
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A moded TPI system can flow pretty good. An Extrude Honed Accel TPI manifold flows 276 CFM. That will get it done. Couple that with fully siamesed SLP runners and a moded plenum and we are talking some horsepower.

Stay tuned as there are cars being built here in SoCal that will be pushing the high 300RWHP mark this year. Lots of good heads and cams available these days with more comming on the market.
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Old 05-12-2006, 10:16 PM   #49
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Quote:
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HAS ANYONE SEEN THIS WEB SITE!!!! Home. I LIKE THE TPI SET UP, AND WANT TO KEEP MINE AS STOCK LOOKING AS POSIBLE. ON THE WEB SITE THE GUY STATES GAINS LIKE A HSR!!!! TAKE A LOOK AND LET ME KNOW WHAT YOU GUYS THINK!
You can do the same thing yourself and won't see any power difference between your home port and the $195 CNC porting on the plenum. I gutted the SLP runners I had more than his picture shows and I shifted that combination at 5500 rpm and with no other change than the Holley StealthRam the shift point moved to 6400rpm,,, but I don't see where he reference a StealthRam. He compares it to a SuperRam,, which the power band would be closer to,,, but still no cigar. Still,, do the work yourself and the bang for the buck on a gutted plenum and gutted SLP runners are hard to beat on a moderately powered 355.
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Old 05-13-2006, 04:59 PM   #50
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Quote:
Originally Posted by rocluvr0013
Thats why i said stock. Porting can and will make a big difference.

Especially since your on a stock (or untuned anyways) computer. 280 to the wheels would put you @ 330 fly (roughly assuming 15% loss) So yes you are very close to those numbers and with stock heads? Thats impressive. Where are you making peaK power? somewhere in the 4500 range i assume? (just curious)

I am peaking at 4900 rpm . Heads would definately move that over 5000 rpm . But the power drop off is far less as harsh as a stock TPI setup .

Click the image to open in full size.

Id I were the origonal poster. I would keep the LTR setup , it's a bit more fun down low . Looks pretty bad . But if you are bent on the biggest output you can get , try a different intake ( shorter runner) . I still have loads of fun shifting this setup at 5000 rpm . Lots of power all the way there too.

Have fun
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