Well guys I am looking at getting a new motor in my car in the next 6 or so months. I have been debating whether or not I want to go with my orginal TPI setup but just go with a 350 or go with an LT1 or a Carb.
I know the LT1's run stronger out of the box than a L98 but the L98's do have a lot of potential. However, the one big thing about the L98's is there inconsistancy that they had from the factory. I know this due partly because of GM's lack of quality control however, I have seen guys that have a lot of mods like, cold air, pullies, exhaust, ignition and Edelbrock baseplate and runners only running high 13's and a friend of mine just put in a chip and an exhuast and runs 13.8's with his L98. If I do a rebuild on a TPI 350 what could I expect with SLP headers, exhaust, a decent cam and hopefully an edelbrock intake. I have 3.42's and a 700 R4 with a stage 1 shift kit and Corvette Servo.
Then I could get a low mileage (60k or less) LT1. This would get me mid to high 13's with headers exhaust and chip. However the swap may cost significantly more especially for the wiring and all that computer crap. It would be different but with 60k miles or so I would be looking at a rebuild within about 80k or so.
Then there is the ever present Carb question. I can get good gas mileage with a carb if I drive halfway sane and also that would be different for my car as well. Carb motors can be modded easily and run really really hard. I know a guy that is in the low 13's like 13.2's with his 305 carbed motor!!!
What are your opinions and pro's and con's. Feel free to e mail me if you would like. IROCZSS@AOL.COM

THANKS GUYS



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TPI 305,
Gutted airboxes,
gutted MAF,
K&N filters,
Corvette Servo.
14.9@93mph

"Speed kills, wanna live forever, drive a Ford."

 

You'd be surprised. I've seen stock 93-94 LT1 Z's and Trans Ams run high 14s. Auto and stick. Road and Track got a 14.8 in the 1/4mile with the 1994 Trans Am. Thats about equal to the time of a stock 91 305 TPI 5speed formula. There are alot of L98 guys running mid 14s out of the box. Don't count on being in the mid 13s on an LT1 with the chip and a few bolt ons.
I'm sure a few have done it, but we all know about the consistency of GMs engines (not very consistent at all!). It all depends on how fast you want to go. Stay with your 305 and modify it out the bunghole. If you set aside about $2000 for it right now..it will be a hell of a lot faster than the $3000 you spend swapping in an LT1. Swapping an engine is a PITA. Anyone can drop a bigger engine in there to go faster, why not make your 305 fast? That way you can make everyone feel bad after you smoke them

Your times are already pretty good for what mods you have done.

Get a good catback ,slp 1 5/8th headers,3:73 gears,1.52 roller rockers,TPIS ZZ9 cam,SLP cold air intake,TPIs 52mm throttle body,AS&M runners, drag radials and a custom burned TPIs chip. If you want to take it even further you can get AFR heads or have yours professionally ported.

You should see a nice increase in performance. And it would still be under the $3000 you spend for an LT1 and all the accessories you need to install it.



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'92 Formula
305 TPI
Mods: SLP catback,SLP air foil,ported plenum,Crane AFPR (49psi),MSD6AL,homemade cold air,K&Ns,3:73s,JET fan switch...SLP 1 5/8ths are coming...oh yes

 

Theformula what times are you running??? Should I completely forget about carb???


------------------
TPI 305,
Gutted airboxes,
gutted MAF,
K&N filters,
Corvette Servo.
14.9@93mph

"Speed kills, wanna live forever, drive a Ford."

 

On G-tech pro I turned in a 14.3 before the add on of my AFPR. I'm hoping with headers, and a new clutch (mine has took a dump just about) it will throw me in the high 13s.

I'm not going to touch my cam just yet. However when I do, it will be a TPIS ZZ9 cam.

Forget about carb and stick with your 305. Trust me...i know how easy it is to be influenced and to believe a 305 is "inferior".

They don't think that anymore when I blow past they're 350s.

 

IROCMANIAC, here is some info on ******* car (moderator). Convinced yet?


Willie

Supercharged 1987 305 IROC-Z, Daily-Driver, Emissions-Legal.
12.57 @ 111 mph.
12.04 @ 114 mph (50-hp nitrous). http://www.ozemail.com/au/jca69/mods...sz/willie.html

1987 "20th Anniversary Commemorative Edition" Z28 Convertible -- Super Chevy Show Class Winner, 1998.

 

If emissions are not a concern, then the best performance bang for the buck would be a carb'd SBC 400.

Modding a fuel injected car is an expensive proposition and (unfortunately) may not yield the results you were hoping for until you get the car "tuned" properly.

When you add up the cost (and effort) of swapping the F.I. system (TPI has its limits), power adders, etc, you'd would have been there IF you had build a good 400 with a carb. Carbs are a lot easier and cheaper to "tune" to obtain optimum performance.

Lastly, a 400 can easily make a civilized 400 HP and has far greater potential beyond that. A 400 HP 350 is getting a little finicky and a 400 HP 305 would be quite tempermental without using a power adder. A 400 HP SBC 400 would be the most streetable of the 3.

 

Any carb impressions and other opinions would be greatly apprecieated.

------------------
TPI 305,
Gutted airboxes,
gutted MAF,
K&N filters,
Corvette Servo.
14.9@93mph

"Speed kills, wanna live forever, drive a Ford."

 

is this a daily driver?
if so, carburetion wont get near the milage of fuel injection. nor will the durability be bettered. more concerns of fuel quaility and carb settings can not be set it and forget it. for fuel injection, sure its a lil more technically advanced, not everyone can work on them, but if consistancey (et and mph) is desired then fi is the one. if budget is more a concern then carb it and save the dollars to fill the tank. the biggest problem i see is that someone wants 400hp, will give $6000 for it, whine they just got their tail kicked by a near stock car and blame the people selling the parts. 400hp wasnt meant for the street. 400hp wasnt meant to be driven 100,000mi before wrenching the heads or rebuilding the lower end at 20000mi. street engines wernt meant to blast 5-6000rpm and not cost $8000 to build every year.
ironmaniac: you mentioned 'inconsistancies' of the L-98 what are you talking about? its not that the peeps installing all that aftermarket muscle and hype just didnt help.
im not doubting that there are some differences between engines, but i wouldnt blame the manufacturer for the slowness of the others vehicles. i believe the reject on an engine is 8-12% hp loss at the crank. and this would be a regional kick. excluding the heavy emissions cars (3-7%). ive watched the boards for 9 years and watched the readers buy the cam\manifold\wax of the month and all didnt get the same results. why? conditions? installation? difference? im not flaming this thread, but not every part bought and installed on a vehicle will produce the same results becuase the end opinion is: did it make my car faster? you mean i spent $1500 and it didnt go any faster? thats a rip off!!!
and i wouldnt contribute that to gm and their qc. maybe the 32000mi t/a could use coil and gain a .05sec but the 125000mi could probably benefit with a total ignition overhaul.
the number one call i get everyday is 'will your product make my vehicle faster, get better fuel economy, and not cost an arm and a leg'?
i usually tell them they can choose any two of the three and maybe we can talk... j/k
heres a scenario:
1988 corvette coupe daily driver street radials.
383 L98 afr heads, comp .555 cam, 10.5:1, ling headers tpis base\slp runners, 58mm tb, 2.75 exhaust, ported to the gills, 700r4, 2500 stall, 3.07 rear gear 12.50/101mph
dynoed 295rwhp/400rwtq (weak huh?)
same car
355 L98 brodix head, same induction, 10.5:1, comp .570, same 2500 stall, 3.54 gear, 3in exhaust 11.90\116mph. dynoed 335rwhp/445rwtq
what do you want? the reason he like the L98 is consistancy in the times and mph. the L98 is torque and you have to manage the torque element properly. i keep agging him on to miniram it and pronounce some hp. but this car is heavy. better balance f/r weight wise but still heavy.
look this is getting too long, and again not flaming the thread, but the whole meaning im trying to say is the total package of car\hp\torque has to be managaged and planned to produce results most peeps would give double the dollars for. only because theyve seen it done before and it didnt work for them.
i dont blame gm for that. ive seen hundreds of tpi systems and dont see any variences in production that would be grave concerns of power loss.
ive seen some 12-13 305tpis, some 11-12 350 tpis and theyve got about the same $$ in each. just depends on if your willing to let go if it. if $$ is an issue then like i said carb it and save the extra for fuel.
sorry to ramble...
airdeano

 

WHOA!!! I love GM. However, I have talked to a couple of people at GM dealerships(this doesn't always mean anything) they said the quality control was a little weak. L98's can run really hard. I was at the track a couple weeks ago and a guy ran a 14.3@96 mph with his IROC all it had was a flowmaster system andhe had 2.77 gears with his L98. The thing is ***** fast. Anyways itis my daily driver. I have had some tell me to build up my 305 but it just won't have enough for me. I don't think I am going to get a carb just because I already have the TPI setup from my 305 and if I can find some Edelbrock runners and base plate I may be in business. Any more resonses will be appreciated.

------------------
TPI 305,
Gutted airboxes,
gutted MAF,
K&N filters,
Corvette Servo.
14.9@93mph

"Speed kills, wanna live forever, drive a Ford."

 

I'd definitely vote for a TPI set-up, but your success will ultimately come down to a question of balance. Recognizing the inherent strength's and weakness of TPI and working with them. Before you even begin the build-up try to find as many articles as possible by Ray T. Bohacz(old issues of High-Tech Performance, GMHTP and Hot Rod). He has written many very good pieces on F.I. in general and TPI in particular. He continually stresses components that complement each other and avoiding mismatches(ironically, the staff at GMHTP have chosen to ignore most of his advice on thier TPI project car. By my reckoning they have spent $6000+ on the motor, and the car only does mid-13's. Ugh!). Again it all comes down to balance.

I'll finish with a couple of guy's who might know what they are talking about:

John Baechtel - author of many books on Chevy high performance: "The aftermarket is loaded with hop-ups that will make your TPI-equipped engine equal or better than any LT1 or LT4. A good TPI-equipped car can still beat these things across an intersection, and it will run right with them up high with only a few modifications." - from "Chevy TPI Swapper's Guide"

John Lingenfelter - who really doesn't need any introduction: "It's apparent that the new LT1 intake was seriously limited in it's design by the new Camaro and Firebird styling to the extent that Chevrolet engine designers were not allowed the freedom to create the manifold they perhaps would have preferred." - referring to the LT1 manifold: "However my tests have shown that this short runner lenght exhibits poor fuel distribution during low engine speeds..." "...the LT1 does not make as much mid-range torque as the longer runner length L-98 TPI engine."

I believe your goal of mid(or even low) 13's is easily attainable with TPI, without sacrificing street manners. Hell you could get there with a 305 even. Andriis Skulte recorded a 13.4 on his 305 TPI, without removing the valve covers.

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He who hesitates,... is lost!

 

On these "inconsistencies" of the L98, the most common variance between the engines seems to be in fuel pressure. An AFPR will cure this problem.

I still believe that "tuning" is often the major difference from engine to engine, with incorrect fuel pressure being a leading cause. I did a lot of playing with my fuel pressure and I was quite surprised to find that it was a very narrow range which yielded the best performance on my car. The biggest killer in performance was caused by too high of fuel pressure. At 50psi, I lost over 1 second over my optimum setting (around 44 psi).