C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

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Old Sep 16, 2018 | 09:17 AM
  #21  
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It still comes down to money. Lose the efi and go carb or self learning tbi; build a old school sbc You can meet you goal relatively expensively, as long as you don't have emission testing. Going carb will require a hood scoop most of the time.
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Old Sep 16, 2018 | 12:33 PM
  #22  
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Originally Posted by topfuel67
Gears are about the easiest way to get more performance. The 4+3s came with 3.07s. They used 3.33s for 89 manuals and were up to 3.54s later in the 90s. You can probably sell your Dana 44 with 3.07s for about the same as you can find a later one. Maybe only be out 200.00.
Thanks I have been thinking about different gearing and keeping the engine where it's at with a lt1 intake
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Old Sep 16, 2018 | 01:30 PM
  #23  
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3,45 is a great gear with the L98. Not too tall, not too low and pulls hard.
The comment about L98s and bolt ons to a point is true to a point. "Bolt ons' with most cars arent worth it
Back in the day nobody even called an intake, dual exh, headers or a 4bbl a mod everyone had em and they didnt do much.
The intake sucks, the heads are not great, the exhaust sucks too.

Either do something mild & cost effective, buy a different car or plan on spending a chit ton and changing everything.

Theres a $ threshold on these cars where it goes from worth it to wtf an I thinking. lol
.

Last edited by cv67; Sep 16, 2018 at 04:22 PM.
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Old Sep 16, 2018 | 03:18 PM
  #24  
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IDK -- I did a lot of research on this and honestly my takeaway is that for most people these L98 cars are pretty much what they are unless you are going to totally redo the powertrain which is both outside of most people's skill level and budget.

I mean like the other posters have alluded to I am just having fun with my C4 as is. It is faster than most cars on the road just as it is. Plus, why give up the great fuel economy?

I also agree that it makes more sense to get a C5, they are just more powerful to begin with. That is my plan anyway.

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Old Sep 16, 2018 | 04:08 PM
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Originally Posted by Kevova
It still comes down to money. Lose the efi and go carb or self learning tbi; build a old school sbc You can meet you goal relatively expensively, as long as you don't have emission testing. Going carb will require a hood scoop most of the time.
Good point..efi has its pluses but can be costly to modify. 1000 for an intake is insane.
x2 on a carb...some arent familiar with them today but why limit a build on hood clearance? change it up and make it run!
Run a return line to the tank, a good fan/low temp stat to avoid todays **** they call gas to avoid the boiling off problems they bring.
Outside of hot restarts on pump gas love my 850 dp. Simple reliable and 100% pedal feel

Last edited by cv67; Sep 16, 2018 at 04:54 PM.
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Old Sep 16, 2018 | 04:41 PM
  #26  
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In all honesty, modding an 85 seems to be waste of effort and resources. Stick to a gear change and call it a day. Way to much needs to be changed out and then you have a tangle of parts that never seem to want to cooperate with each other. Unless you want to sink a ton of money and get everything done properly.

I’ve modded an 85, went through different intakes/carbs and other parts. It was sold off and haven’t missed that headache st all.

Last edited by ChumpVette; Sep 16, 2018 at 04:43 PM.
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Old Sep 16, 2018 | 05:13 PM
  #27  
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Originally Posted by ChumpVette
Way to much needs to be changed out and then you have a tangle of parts that never seem to want to cooperate with each other. Unless you want to sink a ton of money and get everything done properly.

I’ve modded an 85, went through different intakes/carbs and other parts. It was sold off and haven’t missed that headache st all.
Or ask the tuner what he has had success with in the past and what he recommends for now with growth considered? A radical idea no doubt.
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Old Sep 16, 2018 | 05:31 PM
  #28  
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Originally Posted by aklim
Or ask the tuner what he has had success with in the past and what he recommends for now with growth considered? A radical idea no doubt.

How many “tuners” still support 85’s, especially the ECM
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Old Sep 16, 2018 | 05:45 PM
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Originally Posted by ChumpVette



How many “tuners” still support 85’s, especially the ECM
Don't know but I think you will know only if you ask. I know of 1 for sure
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Old Sep 16, 2018 | 07:53 PM
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How much money do you have for this and are you able to do the work?. To get 300 hp will not take much and if you do the work yourself it is very cheap.

113 used heads
small but good cam
headers
may need a tune
port the intake or use the lt1 intake with supporting mods

less then 3000 if you do the work and 350 hp.
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Old Sep 16, 2018 | 08:06 PM
  #31  
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Originally Posted by Bigpoop
1985 l98

STOP THE INSANITY. Bolt-ons for a l98 is like putting **** on a bore.

Keep it. Cherish it for what it is.

Don't fall prey to these interweb gurus.

Save your money. Buy a C5 next year....when the mid engine comes out...prices will drop.
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Old Sep 16, 2018 | 09:55 PM
  #32  
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The bigger question is how much fabrication can he do?
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Old Sep 16, 2018 | 11:02 PM
  #33  
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Originally Posted by cuisinartvette
Good point..efi has its pluses but can be costly to modify. 1000 for an intake is insane.
x2 on a carb...some arent familiar with them today but why limit a build on hood clearance? change it up and make it run!
Run a return line to the tank, a good fan/low temp stat to avoid todays **** they call gas to avoid the boiling off problems they bring.
Outside of hot restarts on pump gas love my 850 dp. Simple reliable and 100% pedal feel
https://www.holley.com/products/fuel.../parts/0-4781C

$567 already. Add manifold and we are almost there. Is vapor lock a recent thing or has it existed for a long time? Seems like old timers are talking about.

https://en.wikipedia.org/wiki/Vapor_lock

The higher the volatility of the fuel, the more likely it is that vapor lock will occur. Historically, gasoline was a more volatile distillate than it is now and was more prone to vapor lock. Conversely, diesel fuel is far less volatile than gasoline, so that diesel engines almost never suffer from vapor lock.
According to that, it was worse in the past than today. OTOH, you seem to imply that it was better in the "good old days". Also, another issue is that carbs are harder in the cold weather or at least, my lawn equipment seems to be. My toys that were carb also had that issue till I got rid of every last one of them. Now, with EFI, fire it up and go. No waiting for warm up or choking, etc.

Last edited by aklim; Sep 16, 2018 at 11:04 PM.
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Old Sep 17, 2018 | 10:12 AM
  #34  
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I think I'll just do long headers, change my rear diff and do a small shot of n20....and save for a c5 I want to keep both
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Old Sep 17, 2018 | 01:18 PM
  #35  
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Originally Posted by Cloud92
I think I'll just do long headers, change my rear diff and do a small shot of n20....and save for a c5 I want to keep both
If that is the case I'd leave it alone and mod the C5 which is easier
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Old Sep 17, 2018 | 03:45 PM
  #36  
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Here is my project, -86 L98 TPI Automatic.
I've done all the installations myself. The budget was about 4k.

Here's what I have changed, other parts are original.
-2.5" exhaust with X-pipe
-Hedman headers
-New harmonic damper
-Mild Comp Cam cam
-113" Corvette heads - not ported
-1.6 ratio Scorpion roller rockers
-Boshc 4 EV14 30lb injectors with adapters
-Ported intake
-Ported SLP runners
-Ported Plenium
-New MSD wirings
-AC delete kit
-Air pump delete kit
-Airfoil
-K&N filter with opened housing
-PLX wideband
-Tuned original ECM
Dyno tested 330hp and 570Nm.
Next coming Procharger P600B with Aquamist methanol / water injection.







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Old Sep 18, 2018 | 12:42 PM
  #37  
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Originally Posted by MrBigDee
Here is my project, -86 L98 TPI Automatic.
I've done all the installations myself. The budget was about 4k.

Here's what I have changed, other parts are original.
-2.5" exhaust with X-pipe
-Hedman headers
-New harmonic damper
-Mild Comp Cam cam
-113" Corvette heads - not ported
-1.6 ratio Scorpion roller rockers
-Boshc 4 EV14 30lb injectors with adapters
-Ported intake
-Ported SLP runners
-Ported Plenium
-New MSD wirings
-AC delete kit
-Air pump delete kit
-Airfoil
-K&N filter with opened housing
-PLX wideband
-Tuned original ECM
Dyno tested 330hp and 570Nm.
Next coming Procharger P600B with Aquamist methanol / water injection.







Car looks great but at what point do you guys realize that you’re just wasting money when you could have just done an ls swap. Easy power + good fuel efficiency. I cringe every time I read about someone spending 4-5k to make lower horsepower numbers. 😬
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Old Sep 18, 2018 | 01:39 PM
  #38  
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Originally Posted by slow_zo6
Car looks great but at what point do you guys realize that you’re just wasting money when you could have just done an ls swap. Easy power + good fuel efficiency. I cringe every time I read about someone spending 4-5k to make lower horsepower numbers. 😬
With what we have going on today, you'd be right if you insisted on keeping the C4 body. Much easier to buy an LS equipped car and mod it.
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Old Sep 18, 2018 | 01:51 PM
  #39  
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Originally Posted by slow_zo6


Car looks great but at what point do you guys realize that you’re just wasting money when you could have just done an ls swap. Easy power + good fuel efficiency. I cringe every time I read about someone spending 4-5k to make lower horsepower numbers. 😬
I can't speak for all but some of us follow the idea you have to **** with the D!$# you got. I mod on a budget and limited time. Can I convert my L98 car and ecu system to an LS with 24 or 58X system? Yea I can, but at that rate I will grab the megasquirt sitting in my box of goodies for another day and have all the features I could want and get a 6.0L vortec block as a start.

I recommend people try to build with what they have as a learning experience and so IF they every sell the car it is easier to return to stock. The other thing to remember is that an LS swap is more than a bolt up. It is weeks ( usually) of fitting parts and fabricating mounts to make the supporting parts like fuel system, cooling and the accessories on the front of the engine play nice.

An LS swap is great bang for the buck, but an engine swap isn't always in the cards.
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Old Sep 18, 2018 | 10:16 PM
  #40  
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Originally Posted by Space387
I can't speak for all but some of us follow the idea you have to **** with the D!$# you got. I mod on a budget and limited time. Can I convert my L98 car and ecu system to an LS with 24 or 58X system? Yea I can, but at that rate I will grab the megasquirt sitting in my box of goodies for another day and have all the features I could want and get a 6.0L vortec block as a start.

I recommend people try to build with what they have as a learning experience and so IF they every sell the car it is easier to return to stock. The other thing to remember is that an LS swap is more than a bolt up. It is weeks ( usually) of fitting parts and fabricating mounts to make the supporting parts like fuel system, cooling and the accessories on the front of the engine play nice.

An LS swap is great bang for the buck, but an engine swap isn't always in the cards.
LS engines have been swapped into just about everything these days and if you wanted to swap one in a C4 it wouldn’t take that long. Different strokes for different folks. If people wanna continue to spend $4-5k building gen I sbc engines that might make 400hp then so be it-it’s your $ just funny to see people waste it and most likely be disappointed in the end.
I wouldn’t waste the time or money trying to modify an L98.
To each their own.
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