81c3

Your questions have been answered.... bottom line is, you dont like the answers youre getting. Your theoretical torque monster getting 40mpg from light to light is a frikken pipe dream and not doable.

Its been explained to you now... I dunno, 20-30 times... but you refuse to see the error in your thinking... This is not our problem, its yours.

....and its not a motor... its a damn ENGINE!!!

A motor is what will accomplish your goals... not a damn LT-1 build....

Now go away and leave all of us stupid Corvette owners to talk about **** we have no idea about..... Go to the F Body Forum and explain to them what you want to do... let us know how that works out. ....or did you already try that and that's why you're here spewing this nonsensical garbage?

Do you know the definition of Insanity?..... of course you do....

GREGGPENN

Uhhhh....I remember a "homework assignment" designed SPECIFICALLY to get you to understand how YOU f-up the threads you participate in.

FWIW...If you were nicer to your dad, he'd BUY you a new car.

Phoenix'97

This isn't about "proving you all wrong", it is about satisfying my need to improve my motor given the criteria I have set for the build. This car won't be anything impressive by other standards but for me, I want to have something that feels like a genuine muscle car! Yes, I can spin my tires if I want to but this isn't about how well I can perform a burnout, it is about how hard it feels to gun my car from a green light while maintaining traction up to the speed limit. The best my car can do is up to 50 mph requiring one shift into second before 5000 RPM and then I have to let off soon after. That is all the "fun" I get to enjoy out of my car! So, how do I improve the motor to put more of a smile on my face? I hear the TPI motor was very good for doing just that, so why not put the TPI intake on my LT1 and figure out the rest from there?

Phoenix'97

I am already seeking other opinions elsewhere as I research this build of mine. IF Corvette TPI owners won't be of much help, maybe F-body TPI owners can help me make a decision about the intake on my motor.

84 4+3

True. However, for the amount of money you'd get for a lt1 car vs an l98 car, you'd be ahead of the game selling the lt1 car and fixing the l98 car. On top of that with it being older insurance is surely going to be less and you'll be getting "better" fuel economy so you're saving there as well. There are plenty examples of low mileage Sunday drivers all over... Just saying I don't really see a down side and if it's in as good of shape as you say it is you'll get top dollar for her too.

Phoenix'97

Yeah, but a good reason I am holding on to my car, despite the cost it has been to keep it going, even now at this stage in my life, is because I love the styling of the car. The only issue I have is that the motor just does not give me what I am seeking and I refuse to buy another car or swap a different motor in. So, being as stubborn as I am, I am left with the question of how to modify this motor to make me happy with it.

I have a second-generation LT1 which has higher compression than the L98 and the potential to increase the compression a little more. I want more power down low from idle and up to the mid-RPM range around 4,000 preferably. Okay, I could try using the right camshaft that works with 1.5 RRs, for the fuel economy aspect. However, I am still leaving some leftover torque on the table by not having the right intake optimized for this powerband. This is why I am so obsessed with the TPI intake. I only need to modify a few things to get my LT1 intake connections to work with the TPI intake connection points, fuel rails and all. I just need a good case for why I should not do this whether it being the complexity behind camshaft selection, needing to retain my stock camshaft with 117 lobe separation to spread out the torque or actually needing that B-body stock camshaft with 111 lobe separation.

84 4+3

The 88-89 l98s ran a 117 lsa... Just and fyi they are also a little more racey feeling then others as the cam is the more aggressive of the l98 cams iirc. I'd imagine it's similar to the lt1 cam.

if you're only looking for power to 4k I have a nice crossfire intake sitting in my garage. And not matter how hard you try you won't be making power above 4500. Heck I don't even remember if it would go over 4.5k.

Phoenix'97

Yeah, I did notice that way back when I first posted the cam specs for the different year L98s and LT1s along with aftermarket cams I was considering to use.

CAM 88-89 L98 10066049 In/Exh Dur@.050" 207'/213' Lift (w/1.5) .415"/.430" LobSep 117'

92 LT1 205/207 @ 0.050" .451"/.450" Lift, LSA 117
93-95 LT1 202/207 @ 0.050" .450"/.460" Lift, LSA 116
96 LT1 200/207 @ 0.050" .447"/.459" LSA 117

Yeah, the two camshafts may be close enough that I won't have to switch mine out.

I read on a B-body forum that a guy with a Vortec engine had swapped a TPI intake on it and was asking if it mattered if he used the camshaft from an F-body that was already installed or if he really needed the B-Body camshaft. The general consensus was that it mattered none. On another forum, the B-body camshaft offered more low end torque but basically it produced the same power if a B-body and F-body were modded the same with bolt-ons. Even on the EPA fuel mileage site the B-body is rated at the same mileage as the F-body for the same LT1 years. So this is where I am trying to figure out which of the two would be better for this application I am looking into.

If my LT1 tachometer will literally max out at 4500 with the TPI intake, then I won't be too heartbroken about it. That is my maximum shifting point anyways!

MatthewMiller

Quoted to highlight the stupidity.

Space387

Not looking at the possible hood clearance issue because I really don't know how much room you will or will not have at the TB before it touches, the only modifications required to make the L98 intake fit an LT1 is to relocate 4 of the mount holes and re-drill the others due to a different mounting angle. Oh and patch the hole for the distributor, so pretty easy job. Fuel system may need custom lines where you have steel crossover tubes ones but thats not too big a deal. The best way now is to spend the money and try. We can theorize the gains and falls of this project 'till the cows come home, we wont know unless someone builds it and dyno's it.

Phoenix'97

The stock LT1 WS6 hood will provide more than enough clearance for the TPI intake and throttle body. The highest point in my engine bay is the very top of my air box intake, raising the tubing three additional inches to match the new location of the throttle body attached to the TPI intake still leaves ample room to close the hood, so I am not worried here.

If the only problem with using a stock TPI base is the drill holes, it is a simple enough solution to have a machine shop add more material, fill in the old holes, and match the new holes to the bottom of my stock LT1 intake. Hopefully port matching will not be needed.

As far as the distributor hole, it will sit behind the motor so there is no need to worry about it nor spend the money to cover it up with a weld job. The fuel lines can be dealt with.

Well we will see how this goes. Right now I am trying to figure out which stock camshaft would be the better choice for my build.

Phoenix'97

Okay buddy, how does the TPI behave when you push it beyond 4500 RPM? No one wants to answer this one! Please, give me an idea about how the TPI effects the motor.

bjankuski

Phoenix, let me try and explain the problem with trying not to use RPM to get your car from zero to 50 in the least amount of time. What you are looking for is the most HP/torque under the curve (which means the area where you use you engine when looking for max acceleration). You want the max torque at the rear tires as possible from zero to 50 or whatever speed you choose (which also means the max HP at the rear tires) to keep the car accelerating. If you build the engine to have low RPM torque but use the TPI intake which means you want to shift at 4500 RPM you will lose lots of torque at the rear tires to accelerate the car when compared to using more RPM. Here are some numbers to consider 4500/3.06 1st gear transmission ratio/3.23 rear gear ratio = 455 RPM of the rear tires at shift point 455 x 6.75 ft/rev/5280*60=35MPH at the shift. Let's assume you have 300 HP at 4500 which is 350 ft/tq at that RPM that 350 ft/tq x the gear ratio's of 3.061st gear ratio x 3.23 x 350 ft/tq = 3460 ft/tq at rear tires in first gear. As soon as you shift the torque at the rear tires drops to 1.62 2nd gear ratio x 3.23 x 350 ft/lbs 1831 ft/tq at rear tires to accelerate the car from 35 to 50 MPH. Now assume you build the LT1 to take advantage of the RPM that the intake can support and assume you peak the HP at 5500 RPM and shift at 6000 RPM and cam the car to operate in that RPM range. This means it will make similar torque to the previous combo at 350 FT/tq but it will do it at higher RPM which also means much higher HP. That combo will shift at 6000 RPM as noted before that means (if you do the math) that the car will still be in first gear until 47 MPH. So you can see that from 35 MPH to 47 MPH that car will be accelerating 3460-1831 = 1629 FT/TQ additional torque to the rear tires vs the low RPM engine which must shift because it is too far over its power band to make any power. Once both cars are in 2nd gear acceleration will be similar but before long the low RPM engine will have to shift again and then the higher RPM engine will be pulling much harder since it is in second gear vs the third gear.

What you want to do is boost the peak torque of the LT1 engine and use its RPM capability. It is misrepresentation of the facts to assume a high torque low RPM engine will accelerate the car faster from zero to 50. To boost the torque of the LT1 you want to use a fast acting cam that has similar closing points to stock but has more lift and longer .050 numbers. Also better flowing heads will build more torque and higher compression. This will not work as well on an engine with a TPI intake because the intake will kill the airflow which will negate the effect of the cam and compression. I also mentioned before that if you want an intake that is better for torque and power then an LT1 intake and still make power to 6000 RPM find the rare Superram intake designed for the LT1 engine and use the 219 cam.

Space387

bjankiski, only because it will skew the numbers a touch he has 3.42 rear gears and his 1st is 2.66 2nd is 1.78 ( 95 F-body T56)

I suggest changing one component at a time to give quantifiable changes based on single changes. So Intake first see how it is then cam, or the other way around. Also the TPI engines fall on their face over 4500rpm. Flat on their face. Most who raced these engines in teh late 80's and early 90's shifted at 4750-5000rpm to keep the power up. This required lower rear axel gears this killing off the line acceleration and massive changes in power between shifts.

bjankuski

Thanks for the correction, I thought he had an auto. That still does not change the basic discussion, you just add in the different gear ratio's to see torque at the rear tires. The theory is still that same.

By the way the LT1 intake is designed to work well with the T56, the TPI not so much.

Space387

Yea I have a 94 Formula like his and a 90 Corvette with the ZF6 and without a doubt the Firebird has more pull from launch to redline, hence why I don't see where changing the parts will benefit.

bjankuski

As you can see by the power curve the TPI intake boosts low end power a little but has no high RPM power. The L98 and the LT1 are very similar in engines with similar cams and head flow, but the major difference is the intake. As shown the TPI does not make good medium to high RPM power.

Phoenix'97

The concept I am struggling to grasp is how exactly the torque curve for the TPI won't be useful for my application as a daily driver spending most of it's time around 2000 or 2500 RPM and when I do decide to let loose, I don't push the motor beyond 5000 RPM.

Well, would this aspect really pain me when my shifting point is at 4500 to 5000 RPM at maximum? I don't think it is advisable to put in a 2.73 gear ratio on a 6-speed, and I do plan to throw on a bit bigger and wider rear end tires, so my 3.42 gear ratio will end up acting like a 3.23, possibly. So, I just need to learn more about why building for more low end torque is not ideal granted my driving style for daily driving. Then lastly, with the LT1's higher compression, it will shift the L98 TPI torque curve up a bit more than it is. So, I then have to ask myself if the B-body LT1 camshaft is really necessary with the additional power from compression.


You know what, I am starting to think that maybe I should spend the money to first modify my motor before I have the entire car resto modded. This way I will know for certain how the components are working, one at a time.

84 4+3

If I shift out of second at 5000 rpms on any road except a highway I'm getting points... If I do that for third I lose my licence. Actually if I do that at 4500 the same thing happens.

1st tops at 40
2nd 67ish
3rd at 94
And it takes about 13 seconds to be going that fast. Stock third gen or 84 vette. Limiting yourself to those rpms isn't saving you much.

bjankuski

[QUOTE=Phoenix'97;1596293625]The concept I am struggling to grasp is how exactly the torque curve for the TPI won't be useful for my application as a daily driver spending most of it's time around 2000 or 2500 RPM and when I do decide to let loose, I don't push the motor beyond 5000 RPM.


Go read my previous post, why would you shift at 4500 RPM, it makes no sense. You would get no advantage doing that! Both engines have more then enough power to allow you to drive that car fine in the 2000 RPM to 2500 RPM range but when you decide to let loose then shift at 5500 plus with the LT1 while you must shift at 4500 with the L98 since it is way over its power band. As I listed before the power band of the LT1 allows you to shift later which allows more power/torque and acceleration in each gear then the L98 intake and possibly do. If you have some self imposed 4500 RPM limit then use the L98 intake but it will only slow your car down from stock while providing no performance gain.

As I stated in my previous post just figure out the RPM and MPH of your car at each shift and that will tell you which combination will get you zero to 50 faster. It is most definately the LT1 intake.

Side note the 1991 L98 has 10.25 compression and the 1992 LT1 has 10.5 compression that is why I chose that graph to negate the compression difference. That .3 difference will only add up to a 1% difference in power so it is a non factor. The real difference is the L98 intake hurts mid and top RPM power with a small increase in low RPM power which is negated by the vast increase in mid and upper RPM power that the LT1 intake provides.

Just look at what the factory does today to see why you should not use the L98 intake. A similar displacement 2002 ZO6 has 405 HP and 400 ft/tq and uses and intake that is designed to shift at 6500 RPM. This is a mid length intake that makes good low end power and excellent mid and top end power. Those cars can hit zero to 60 MPH in less then 4 seconds, and I can assure you they are shifting at 6500 RPM to do this and they have plenty of power at 2000 RPM to move the car fine.