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Old 09-22-2013, 01:41 AM   #1
dtana
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Default Where Does the 50HP Manifest Itself ?

As some of you may know I'm looking for my first Vette, a C4 6 speed. I'd like to pose a contest scenario that I understand is a bit unfair, but please humor me anyway.

2 Vettes, both totally stock, 6 speed, similar condition, age etc etc. , in short comparable. One is a 1990 or 91 L98, the other a 1992-94 LT-1. From what I've read these 2 cars weigh within 50 or so lbs of each other, am I correct? Also, for the sake of this comparison let us also assume that these cars perform as they did when they were new.

Now I understand that the LT-1 has a 50-55 hp advantage over the late model L98 .............& having now test driven 4 L98s & 5 LT-1s (all 6 speeds) of varying conditions in the last 8 weeks, I have no doubt whatsoever that the LT-1s are indeed quicker.

BUT.............here's the contest scenario I'd like to pose to the group. If you were to drag race these 2 cars against each other for 1/4 mile & placed a rev limiter on the LT-1 at 5000rpm & shift the L98 at 5000rpm as well, what would happen? Who would win this contest? Would it essentially be neck & neck? Again, I understand it is unfair, so please humor me.

In short, does most of the 50-55 hp difference manifest itself within that 1000rpm advantage & no where else? Thank you in advance for your responses, comments etc.
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Old 09-22-2013, 02:21 AM   #2
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Originally Posted by dtana View Post
here's the contest scenario I'd like to pose to the group. If you were to drag race these 2 cars against each other for 1/4 mile & placed a rev limiter on the LT-1 at 5000rpm & shift the L98 at 5000rpm as well, what would happen? Who would win this contest? Would it essentially be neck & neck? Again, I understand it is unfair, so please humor me.

In short, does most of the 50-55 hp difference manifest itself within that 1000rpm advantage & no where else? Thank you in advance for your responses, comments etc.
The break-point is more like 4500rpms and up -- but you've got the idea. I think the L98 would win -- if limited to 5000rpms. The midrange would be enough stronger AND the advantage of staying in a lower geart longer PLUS having the top-end horsepower would be negated. (I don't thing the advantage from 4500-5000rpms would be quite enough to offset the midrange torque differences. 5000-5800 is actually quite a large chunck of the "usable" racing range. Considering where it downshifts to, you're probably talking 20-25% removed -- and in the highest power range of the LT car.

I agree the LT1 has better compression and headflow so the race would still be very close.

Compression, headflow, and even the possibility of better 1000-1500rpm response would be the advantages of the later LT car. (Shorter intakes theoretically have snappier throttle response because of their ability to put their shorter [intake] column of air into motion faster.)

Because most cars have automatics AND kick down to that higher rpm/lower gear range, you'll find the reason that longtube intakes were abandoned. Still for trolling about town with a 6-spd, an L98 TPI can present some fun....especially with some stroking to boost that low-mid torque. Of course it still would be -- and is -- beneficial for either engine.

In theory, you're probably leading yourself to the reason I chose a midrange build -- for my 6-spd car. (With an automatic, pick an LT engine and don't look back.)

Last edited by GREGGPENN; 09-22-2013 at 02:26 AM.
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Old 09-22-2013, 02:43 AM   #3
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Don't know if you have considered the aftermarket for both engines yet. l98 Endless aftermarket. Lt1 not so much. Not hating on lt1's just pointing out a big monetary difference when you plan to build.
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Old 09-22-2013, 02:50 AM   #4
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Well said Gregg. What an explanation. Thats why CF is awesome !! I still like the look and feel of high rise intakes. oops (off subject)
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Old 09-22-2013, 02:25 PM   #5
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Thanks Greggpenn. Your comments make a lot of sense & confirm my sense of what is happening. Are the latter L98 engines rated as 245, 250 @4000 or 4400rpm? I've seen both figures quoted.
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Old 09-22-2013, 05:41 PM   #6
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Originally Posted by dtana View Post
Thanks Greggpenn. Your comments make a lot of sense & confirm my sense of what is happening. Are the latter L98 engines rated as 245, 250 @4000 or 4400rpm? I've seen both figures quoted.
90 & 91 L98 / 245 @ 4000 (250-hp for hatchbacks using 3.07:1 rear axle due to use of low-restriction mufflers with this option combination only)
90 L98 Compression ratio 9.5:1
91 L98 Compression ratio 10.0:1

Last edited by floridamale; 09-22-2013 at 05:47 PM.
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Old 09-22-2013, 05:44 PM   #7
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Quote:
Originally Posted by dtana View Post

BUT.............here's the contest scenario I'd like to pose to the group. If you were to drag race these 2 cars against each other for 1/4 mile & placed a rev limiter on the LT-1 at 5000rpm & shift the L98 at 5000rpm as well, what would happen? Who would win this contest? Would it essentially be neck & neck? Again, I understand it is unfair, so please humor me.

In short, does most of the 50-55 hp difference manifest itself within that 1000rpm advantage & no where else? Thank you in advance for your responses, comments etc.




OK here is my opinion and why. I believe, even short shifting the LT1 at 5000 rpms, its going to take the L98 in the example you set above.
I am including a dyno showing the overlay of the 2 motors. Keep in mind it is based on the strongest L98 and the weakest LT1
Now assuming both cars are going to launch at the most efficient rpm, and then shift at 5000 rpms, I don't believe the rpms will drop below 3000 in the race. Look at the dyno and decide for yourself.




If you notice, from about 2300 rpms and up the LT1 produces more hp and climbs very rapidly to 5000 compared to the L98. Torque is slightly better from about 2300 to 3400 rpms, but this brings up 2 things. 1. you will not be in that rpm range in the above proposed race, 2. as stated earlier this is the weakest LT1. 93 and up gained an additions 10 lbs torque.

For these reasons IMO even short shifting the LT1 and lot letting it run at its potential, its going to take the L98, all other things being equal.

Last edited by 93 ragtop; 09-22-2013 at 05:46 PM.
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Old 09-22-2013, 05:59 PM   #8
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Originally Posted by lozer View Post
Don't know if you have considered the aftermarket for both engines yet. l98 Endless aftermarket. Lt1 not so much. Not hating on lt1's just pointing out a big monetary difference when you plan to build.




What are you basing this on? Both use the same aftermarket cams, cranks, rods, pistons, etc. Both have plenty of aftermarket heads available.
The reason there is not much in the line of intakes is the LT1-4 intakes are as good as any of the aftermarket ones out there. So right off the bat you don't have to invest $1,000.00 dollars or so in something such as the miniram.
The exhaust flows very well, not like the L98. Matter of fact, many L98 owners adapt the LT1 exhaust to their L98 motors.
You can adapt an electric waterpump to a LT1 much easier and cheaper then the L98. Very useful especially drag racing and anytime you need to cool the car quickly.
You can easly put a LT1 vette in the 11.7 sec., 117 mph range with nothing but reworked factory heads, hotcam, headers, converter, and 3.73 gears. Keeping the factory exhaust, and intake all at the same time.
For the same money, a L98 will never do that.

All that being said, the only advantage to a L98, again IMO is the availability of aftermarket blocks. But unless you intend to build a 400+ CI motor it does not matter.
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Old 09-22-2013, 07:24 PM   #9
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Originally Posted by 93 ragtop View Post



What are you basing this on? Both use the same aftermarket cams, cranks, rods, pistons, etc. Both have plenty of aftermarket heads available.
The reason there is not much in the line of intakes is the LT1-4 intakes are as good as any of the aftermarket ones out there. So right off the bat you don't have to invest $1,000.00 dollars or so in something such as the miniram.
The exhaust flows very well, not like the L98. Matter of fact, many L98 owners adapt the LT1 exhaust to their L98 motors.
You can adapt an electric waterpump to a LT1 much easier and cheaper then the L98. Very useful especially drag racing and anytime you need to cool the car quickly.
You can easly put a LT1 vette in the 11.7 sec., 117 mph range with nothing but reworked factory heads, hotcam, headers, converter, and 3.73 gears. Keeping the factory exhaust, and intake all at the same time.
For the same money, a L98 will never do that.

All that being said, the only advantage to a L98, again IMO is the availability of aftermarket blocks. But unless you intend to build a 400+ CI motor it does not matter.


If I was in the market to buy ANOTHER C4, I'd never consider an L98 at all. LT1, LT4, or ZR1 would be the only options. Prices have gotten so low, it's crazy not to buy the newer car. Of course, I also like the new body style (in/out) better.

If you liked the old body style better AND didn't have designs on racing AND could steal one, that's when L98's are still worth considering. You gotta change everything to mod an L98. With an LTx, stroke it, cam it, tune it and put it back together. With a ZR1, just drive it.
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Old 09-22-2013, 07:39 PM   #10
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Originally Posted by 93 ragtop View Post



OK here is my opinion and why. I believe, even short shifting the LT1 at 5000 rpms, its going to take the L98 in the example you set above.
I am including a dyno showing the overlay of the 2 motors. Keep in mind it is based on the strongest L98 and the weakest LT1
Now assuming both cars are going to launch at the most efficient rpm, and then shift at 5000 rpms, I don't believe the rpms will drop below 3000 in the race. Look at the dyno and decide for yourself.




If you notice, from about 2300 rpms and up the LT1 produces more hp and climbs very rapidly to 5000 compared to the L98. Torque is slightly better from about 2300 to 3400 rpms, but this brings up 2 things. 1. you will not be in that rpm range in the above proposed race, 2. as stated earlier this is the weakest LT1. 93 and up gained an additions 10 lbs torque.

For these reasons IMO even short shifting the LT1 and lot letting it run at its potential, its going to take the L98, all other things being equal.
I've always those this particular graph (shown above) was designed to exaggerate in favor of an LT motor. Obviously where torque is higher, so it horsepower. So, the statement about the 2300-3400 (3700) rpm range is false. The L98 has the advantage in both power/torque there. Typically, longtube reversion waves provide at least a 7% boost in midrange -- which is somewhat more evident in the torque graph. The sheer slope of the HP graph tends to exaggerate the LT's advantage IMO. Plus, I was thinking the L98 rolloff (graph overlap) was 500 rpms higher -- in the 4200 rpm range. I'm not saying the LTx car isn't the better/faster car -- because it really is. Now that I think about it, since an automatic shifts well before redline...I'm second-guessing whether I believe the race wouldn't favor an LTx until you rev-limited both to the 4500rpm range. I think that's when the L98 would finally gain solid traction.

You can see I was thinking that in my original response.

If the graph (above) is really accurate in it's cross-over points, I'm leaning more to the 4500-5200 range being the source of the 50HP difference. Hmmm....maybe no one should bet against an LT1 until you made him shift at 4500! LOL

Last edited by GREGGPENN; 09-23-2013 at 02:49 PM.
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Old 09-22-2013, 08:34 PM   #11
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Originally Posted by GREGGPENN View Post


If I was in the market to buy ANOTHER C4, I'd never consider an L98 at all. LT1, LT4, or ZR1 would be the only options. Prices have gotten so low, it's crazy not to buy the newer car. Of course, I also like the new body style (in/out) better.

If you liked the old body style better AND didn't have designs on racing AND could steal one, that's when L98's are still worth considering. You gotta change everything to mod an L98. With an LTx, stroke it, cam it, tune it and put it back together. With a ZR1, just drive it.
Amen to that statement !!!!! You can buy a low mileage C4 ZR-1 for under $18K cash. They are out there and money talks. Brakes gears drive train and HORSEPOWER. You don't have to spend a dime on after market parts or a second of time changing anything. Just drive.
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Old 09-22-2013, 09:13 PM   #12
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Prior to CMC (Camaro Mustang Challenge) allowing the later model Mustangs and LS1 Camaros in the series, we ran LT1s against L98s constantly. We all were limited to 230 rwhp. That was about what a stock L98 would do given no mufflers. I had to run a 39 mm TB restrictor in my 48 mm TB to get down to 230 rwhp which effectively limited the LT1 to 5000 rpm since it wouldn't breathe well any longer above 5000 rpm.

Once that was done we were pretty equal. The series allowed the L98 cars to carry 50 lbs less weight to do the final adjustment for parity.
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