I have been reading the msgs in this board for a while and I have two TPI units and have come to the conclusion that the best way to run a tuned port is stock or with little modification... figuring the horsepower per dollar gain,stock form runs best...remember these units were made for massive low/mid range torque and good horsepower to around 5000rpms with the emphasis on emissions and mileage and in stock form perform amazingly well,but when you modify it something is sacrificed.The small block chevy was always noted as a hi rpm engine with a minimum of low end torque and bursts to 7000 to 8000 rpms were where the engine lived,some examples were the 302Z/28 over 450hp at 8000,first 350LT1 over 450 at 7000 and the 327FI over 480 at 8000,but now we have the same but different small block chevy built to run on terrible fuel,low compression,and carburation units that limit you to 5000rpms, so the modifications should be to the vehicle not the engine or fuel injection...Here is what I'm up to...410 rear,700R, and a set of 29.4 inch diameter rear tires this with the stock(350) tune port engine I bet I'll beat your modified TPI stuff

mmm.... ok. Tell me there is no sacrifices with a 410 rear and 29" tires? Given you may run as good or better than most L98's you also have horrible efficiency and drivability, and increased reliability risks. However, you do bring up a very good point. Horsepower is only part of the quickness equation and people tend to ignore the benefits of TPI. Good food for thought.

give me 2 more weeks and ill smoke your setup with my modified 305 tpi

also whats in the sig hasnt been updated yet

Where did you get those HP figures? I was driving (and have driven) the cars that had those engines when they came out and NONE of those engines made 400+ HP.

Yes, the DZ302 was underrate at 290 HP - probably more like 325-350HP, but that was Gross HP which rates engines much higher than Net HP. An LS1 will SPANK any of those engines and it isn't rated anywhere near 400 HP.

Betcha have a heck of a time hooking up in 1st and run out of gear (unless you want to upshift into 4th) at the end of the 1/4.

As long as you have a balenced engine you will make way more HP and Torque. The only thing that has "suffered" is my emissions output is higher, but still street legal. As for $ to HP gain your probably right....except for in my case. I bought most of my stuff off Ebay and I have access to a machine shop so I've only paid like $1750 in mods. The reason why I say this is if you are reasourceful, you can make good power for cheap.

Are you saying you can beat a miniram or superram car in the 1/4 with that setup? Nat. aspirated vs. nat. aspirated? If so, trust me, you won't come close. The difference between my car now and how it was with the stock engine is night and day. GOfasterfirebird has the stock TPI unit, an SLP cam, and AFR 190 heads and ran a best of 13.4 N/A. He slowed down after changing the 3.23 gears to 3.73, so 4.10's will probably slow you down, even with the taller tires. I give you low 13's tops N/A with good tuning and tracton and after getting some great heads and a matched cam. Don't even think you will run 12's with stock heads and cam N/A.

I probably have the slowest L98 ever, you put 4.10's on your car and i will walk all over you.

Well I seem to have gotten some of you guys attention, well here I go again first off if you hooked up some those older engines to the trannys of today there is no way todays engines could compete its a simple case of rpms ,who's running 7000 on thier TPI engine as for where I got my hp figures for older stuff it came from the vast array of hot rod books and publications I have in my possesion ,want to know do some research... Now gear ratio for standard mech ratio is for 26inch tires make the tire diameter larger and you alter the effective ratio..410 gears w 26in tire =375 gears w 29.5 tire in theory add .7 overdrive some where around 325 for final drive, these numbers just my theory... getting the tires to hook no problem, I have a thrd gen but this engine isnt in it. The engine is 60 over with flattops the TPI is a stock 86 model with a speed dencity computer and 22lb injectors the heads are stock 186 cast 194s and headders no cats tranny is a stock 700R w 2200 stall and I don't expect to break into the 12s and will probably never see the dragway but stoplight grand prix it'll getcha

i'll race ya in my lowley ported intake 305
Andrew

My dad could beat up your dad too lol. Isn't on-line pride a beautiful thing?

Am I right by saying this? Doesn't higher gear ratios (ie 4.10:1) only become useful with high revving engines?

**Don't even think you will run 12's with stock heads and cam N/A.**

No one has done this before, a 12.9x ET with stock heads and cam?? Im currently running 13.52 and I know I have a ways to go yet but I still have headers (complete), gears, porting the plenum, removed AC w/ delete pulley(complete), aftermarket base, LCA relocate brackets, adj fuel reg., drag springs, ram air or custom CAI, and tricks like bypass smog pump, !sway bar, ice the intake, increase front tire pressure or run light weight rims and tires, maybe a higher stall (mines at 2k) and shave weight since Im running these times at 3688 lbs w/ driver. The things that I completed are after the 13.52 run, with the rest of the mods and not getting into the motor and in good weather what are my chances of seeing 12.99?? I cant get too crazy this is my commuter car right now, as soon as I get a 2nd car and do what I listed I'll see what I can manage....

LOL, Also being a hot rodding gray beard that was actually alive when those cars were new, and having worked with all of them and many others since, I have to agree with Glen on those well inflated HP numbers. And as mentioned above there is a difference in "gross horsepower" ratings that were used prior to 1974, and "SAE net horespower" ratings in use from 1974 to the present. One of the goals of GM when designing the "new" LT1 was that it had to have atleast the same and preferably more horses as the original LT1 when using the same rating method for both or they were not going to use the "LT1" designation for the new motor. The "new" 90s LT1 beat the original 70s LT1 by about 10 net horses. I also can confirm that an LS1 car will promptly "spank" the @$$ of any of those mentioned above, while only making under 350 SAE net horses.

By the way...

If you believe all that you read...

I've been commisioned to sell the Eiffle tower for scrap, now that they are done with it. It was only intended to be a temporary structure, you know and it's many years overdue it's intended dismantling date. I'll accept a measily 10¢/pound and you have to pick up your metal at Paris yourself.


Anyway, I'll race yah. I'll even remove the blower belt and leave the nitrous bottle in the garage. I think low 12s / high 11s will take you, without reving over 6200 RPM.

Your sources are wrong. The DZ302 was rated 290 GROSS HP by GM (which is generally acknowledged as being underrated using the GROSS HP rating), the LT-1 350 was 360 GROSS HP (Camaro) and 370 GROSS HP (Vette) which would be around 300 Net HP (used today). There were a couple of different ratings for the FI 327, but the last and most potent version was rated 375 GROSS HP (again around 300 HP net AND if tuned right). In fact, keeping the FI327 (original RamJet) properly tuned was very difficult and typically the 4bbl version (L79) kicked the FI327's butt all the time. People avoided the RamJet in those days because simple weather changes affected them and only to get humilated by a lowly carb'd L79.

Those figures I give are GM's actual ratings at the time the engines were released. BTW, when the new LT1 came out, a magazine did a "shoot-out" of the old LT-1 and the new LT1....guess who won?

When the Z/28 302 came out it was a 14.0 second car. I've driven them (when they were brand new). They aren't that fast and there were plenty of faster cars out there. It was a very nice road car, but it wasn't the mighty powerhouse that people are making them out to be.

I am not trying to come down on you, but I am an old-timer that was alive and drove those cars (when they were new). I just get tired of people exaggerating about the engines from the 60s. They rated the HP differently (and HIGHER) and while the kids today listen to their dads reminisce about the "good old days", they actually weren't that good. The big advantage of the older engines is that it was relatively easy to make more HP by a simple carb, manifold, cam and header change. But bone stock, they weren't that quick.

Just don't try to BS us old-timers that were there with "mythical" 400+ HP (Gross, let's not even talk about net) stock small-blocks from the 60s. There weren't any.

The engines that tended to be underated were the Big Blocks and this was primarily due to insurance reasons.

Precisely, high revving engines with big cams often need lower gears/higher stall TCs to overcome their loss of TQ.

I have a complete 3.73 rear axle that I have had in storage for 3 years. Why do you think I never installed it on my basically stock L98? I bought the axle because I have been planning my "build" for the last 3 years, accumulating parts and I was planning to go with the Miniram and I was going to use the 3.73s to compensate for some of the bottom end TQ that I lost.

Putting 3.73/4.10s on a bone stock L98 will make you the burn-out king of your neighbourhood. You are going to have major problems hooking up that car off the line and then run out of breath at the top end because you don't have the rpms.

But don't take my word. Take your bone stock car to the strip and do a run. Swap the rear-end and then do it again. You are going to be sadly disappointed.

NOPE, that's wrong too. Smaller tires are like going to a lower (higher numerical) gear while taller tires are like going to a taller (lower numerical) gear.

It's more like 4.10 w/ 29.5" diameter tires = 3.7s w/ 26" tire. There is a calculator available to give you the exact figures. But that is the basic way it works.

Thanks Glen.... you seemed to set all the facts straight. its nice to have a person with experience on here that'll keep us youngins in the right path.

I am interested in seein gmore of your car, sounds like a monster

ThirdGenZ28, if you run 12's without touching the stock heads and cam, you should go take Lingenfelter's job from him. I've never seen anyone come remotely close to 12's with untouched L98 (ported Vette L98's by Lingenfelter are different) and a stock camshaft. High and maybe mid 13's yes, but 12's? I don't think you can get the power needed from those heads and that cam to get these cars into the 12's N/A. If you prove me wrong, congrats, it will be one HELL of a feat.

I wont be taking his job anytime soon lol, Im a hack with a love for 3rdGens and nothing more but I have no tools, space or skills for tearing down or rebuilding motors and such, I dont even have a driveway. The 13.52 has been run with common boltons that I bolted on outside my house and on a 1.76 60ft and I dont know if 12s are possible either but being .5 away with more boltons left, weight reduction, gears and tricks and maybe more stall Ill see how close I can come, if I fall short low 13s wont disappoint me either until I can save for a healthy crate motor, Ill post times as soon as I have em just incase anyones interested....

Originally posted by agawam
410 gears w 26in tire =375 gears w 29.5 tire in theory
--------------------------------------------------------------------------------

Originally posted by Glenn91L98GTA
"NOPE, that's wrong too. Smaller tires are like going to a lower (higher numerical) gear while taller tires are like going to a taller (lower numerical) gear. "

"It's more like 4.10 w/ 29.5" diameter tires = 3.7s w/ 26" tire. There is a calculator available to give you the exact figures. But that is the basic way it works."

It seems that there is a miscommunication on how tires and rearends act together. Glen, your initial theory statement and Agawam say similar things but your second statement conflicts with what he is saying. I think that you two are trying to say the same thing.

This is the applied mechanics of reaend gears and tires. If you swap in 4.10s (only change in drivetrain)into you rearend while using a stock 26" tire it will turn the tire one revolution with 4.10 turns of the drive shaft therefore making the car move forward 81.7"s or 19.9"s per revolution of driveshaft. With a 29.5" tire and 4.10 gears the car is moved forward 92.7"s or 22.6"s per revolution of drive shaft . So to make the car travel 81.7"s with 29.5" tires it only requires the driveshaft to turn 3.62 times.

In my first paragraph "Smaller tires are like going to a lower (higher numerical) gear while taller tires are like going to a taller (lower numerical) gear" means if you change to a smaller diameter tire you are effectively gearing your car down. IE. If you had 3.7s with 29" tires, and changed the tires to 26", it would be similar to going with 4.1s (with the original 29" tires). Or if you originally had 4.1s with 26" tires and switched to 29" tires (on the 4.1 axle), it would be like going to a 3.7x (with the original 26").

My second paragraph is just a correction to Agawam's formula "4.1 w/26 = 3.7(ish) w/29.5", to what it really is should be "4.1 w/29.5 = 3.79ish) w/26". Which is consistent with what my first paragraph says "Smaller tires has the same effect as using lower gears (higher numerially). Like 4.1s are lower than 3.7s and 3.7s are taller than 4.1s."

What gruvin84ss is saying is what I mean with taller tires you go farther .so if the mechanical ratio is for a 26" tire the effective ratio will be lower (numerically) with taller tires and top speed will be greater with the taller ones at the same rpms therefore if you can hook the taller tire to the ground the car is quicker....

Okay, so you WANT 29.5" tires and thus you WANT 4.1s so it would be like 3.7s with a normal 26" tire? Will this be for "strip only" or do you plan to use these 29.5" tires for all driving? Have you checked for clearance in the wheelwell with 29.5" tires with the width, rim and aspect ratio you want?

YES Ive checked for fit and there is no problem but the car is not a 3rd it'a 2nd but I do own two 3rds and sold two others this year one is a stock 83 T/A w/ a recaro interior the other is an 86T/A with no motor or trans yet the sold ones were an 86 T/A and an 86 camaro

4.10's in a stock TPI 700R4? Thats wayyy too much gear..the best gear is 3.07's for 1/4 mile and TPI.
I have 3.73's in my Vette with 700R4,stock TPI,crane cam and etc and its a monster off the line but I dont think Its going to get track records.I love the feel and the launches from 0-60 but know Id be faster with the stock 3.07 gears at the track.
Track times isnt what I was after so the mod was fine by me,but I wont say it will beat anything TPI.

Oh yeah, theres a guy on the corvette forum who ran 12.9s with a stock L98!! I couldnt believe it but he did.A few guys got 13.4's with their stock L98s as well.Stock 3.07 gears too.
Just wanted to let some of you know.There were a few bolt ons but the engine is NA and no work done to it.

Even I know my 3.73's arent made for top end power,so the person thinking 4.10's and a certain tire size is going to be fast is wrong.My 3.73's are already a bit overkill with the TPI and ya want 4.10's?

If you had a high revving carb intake and etc, I might believe it,but the TPI runs out of steam after 4500 so you will peak out alot sooner and watch the other cars fly by.
Sure,stop light races and burn outs are fun,my car can smoke them at will and fish tail like crazy with ease but isnt going to beat cars better set up for 1/4 mile races with matched components.

No flames intended,just dont think old school muscle car mods with 4.10's and etc like the old days will work with the TPI the way you think it might.Btw,if youre putting this in a 2nd gen,its going to be a Heavier car..some of them weighed like 3800-4000 lbs!
A 3rd gen is lighter and can be made lighter with some work.

You guys never know agawam could go out and run 9s on his car (roflmfao) ok seriously you never know what it is going to do if he has built the suspension corretly. Most of the people on this site don't build a car to handle the power a high performance engine puts out. That is why you see so many people saying "it will go much faster with traction" just think of what some of these cars would run with better suspension parts and not the crappy factory and have the correct geomerty in the suspension.

But agawam there is alot to be said for actual knowlege and all of this total C-R-A-P that they put in hot rod mags. Believe 25% of what you read and 75% of what you see.

PS agawam I expect to see low 12s and high 11s out of my car. OFF THE N20.

OK, i left this thread open just to see if any remotely useful discussion could occur. It didn't, thus i am getting it off my board before it turns into a flame fest. Since everything the original poster stated was theoretical (i just love guys who argue from books and pie in the sky theory against the people who have been there/done that), i am moving this post to the theoretical/street racing board. There is absolutely nothing of technical value to this board in a post about 'i bet my car will beat your modded TPI' when you don't have slips, or even confidence it'll run low 13s/12s....