Major mods.....cuz im bored
#1
11-09-2006, 07:23 PM
Major mods.....cuz im bored
I have noticed that threads start on how to add horsepower on this forum and other forums so I thought I would put my opinion on this. HAHA. Yea I know it dont count for **it but oh well.
You need to make a plan before you begin anything.
Ask yourself:
What do I want to spend?
What do I want out of the engine when I'm done? (as in HP/TQ numbers or ET)
How much of the work can I do myself?
After you answer these you can begin working to make your goal a reality.
YOU HAVE TO MAKE A PLAN. You cannot throw a bunch of parts together and expect to get some miracle. I KNOW. Thats how I think.
Now this thread is for L-98 and L-T1 motors.
FORCED INDUCTION/NOS**NITROUS OXIDE**
1984 and 85 C4s come with forged TRW pistons from the factory, as holdover parts from the late C3 and these cars will be able to handle more generous amounts of juice. I would start low, say a 50 shot, and go from there. The forged pistons 'may' allow you up to a 150 shot before entering danger zone. Stock compression is low already because of the large 76cc chamber. Be sure to use higher octane gasoline when you are going to be running that much juice however. There is no way to definitely know what to use without a scanner to detect knock counts, and you want to use the lowest octane gasoline you can and not have them.
86-91 C4s use a cast piston, which is not good for juice, so I would only stay in the 50-75 shot area. 92-96's have a hypereutectic piston, which is not much better than cast. These engines also have much higher compression, so you better keep an eye on knock.
Building a motor for NOS
As far as building an engine for extended use with Nitrous, you must use forged pistons and rods, thats pretty much set in stone. These two are going to be taking the brunt of the punishment in the bottom-end. Cranks are very hard to destroy unless you lose oil pressure, and unless you want to spin it above 7000rpm regularly you dont need a forged one.
You would ideally want the engine to be 4-bolt main splayed (thats where a 2-bolt main block has 2 extra bolts drilled into the meat of the block, which is stronger than a regular 4-bolt), and have heads with larger combustion chambers and to have the final compression ratio in the 9.x:1 range
L-98 Motor
This motor is a torque monster. 330 ft/pds of torque STOCK. Low end is this motors strong point. Midrnage-High RPM is where it falls flat on its ***.
Emissions is killing the potential of this car. The L98 is severely choked from the factory in terms of exhaust flow, so this is the #1 place to begin your modifications.
The main catalytic converter is huge piece of ****, used in the 70s erra and is a major restriction on the engine's.
The precat Y-pipe that started in 86 was added to help meet tougher standards in California. 84-85 do not have precats in their front Y pipe.
The AIR system's primary function is to inject O2 into these cats on startup, which helps them to light up quicker and clean emissions soon after startup. Once the engine is hot, the AIR really does nothing. AIR pumps to the manifolds on startup, then switches to the main cat in closed loop.
EGR introduces exhaust gases back into the engine, which lowers combustion chamber temperatures.
Headers:
Long tube headers can give back 15 horsepower to the L-98. You must delete the exaust manifolds and front y pipe.Delete all cats and use a highflow cat such as catco. They only restrict 1-2 horsepower.
I like these headers: Hooker 2149 (with O2 bung, AIR pipes, and EGR, ceramic coated)
Hooker 2151 (no emissions, no bung, uncoated)
Hooker 16720 Y-pipe can be used with either.
Deleting AIR:
Alot of the manufacturers of headers make a set with the AIR pipes deleted. As I said above, AIR only functions on startup until the engine is warm, so you can safely remove it with no ill effects to emissions testing (provided you get the sniffer done when the engine is hot). You can cap off the lines on the headers or not, as the valves are supposed to be one-way only, likewise for the main cat. The AIR eliminator kit sold by many magazines does NOT give you any power, as the AIR pump is a fairly freely-spinning unit, but it does clean up the engine a bit and so is mostly a cosmetic mod. Any connections can be left alone as the L98 does not throw codes when AIR is removed.
Catback:
Any of them should give the same 10-12hp gain. They all vary depending on the sound, shape, looks, ect.Corsa is best for those who do not like resonance (loud droning sound at around 2000rpm usually). There are many brands. The top ones that I reccomend are: Corsa, Borla, B&B, Flowmaster is good for sound but has low flowing capabilities and bad resonance.
Intake
I suggest the miniram If you go this route it will cause you to loose alot of low end torque. It will kick in at about 3000 to 4000 RPMs. It should flow up to 7000 RPMs without issues. The bottom end: Needs to have lighter components, the best parts available for bearings, rods, crank, and pistons. Forged is best for everything. Better have a new oil pump put in too. A larger, deeper pan may be necessary.I suggest using full synthetic oil and upgrading to the larger pan which will help keep everything lubricated and running at optimum.
Top-end: You'll need to get heads with larger ports as they are required to feed the engine at high rpm. 185-200cc would do for a 350. Also, lighter components are best here, with titanium retainers and 10* locks. I think its best to pick springs that are slightly stronger than what is recommended for the camshaft. This will ensure less occurence of problems due to mishaps.
You will need a rev-limiter for this engine, L98s fuel cutoff is set at 10,000rpm. MSD Digital 6 ignition has one built in.
Rear axle: A high-spinning motor will need more rear gear to get you to the power zone, so something in the way of 3.54/3.73/4.10 would be best. This, combined with gas mileage, is why I would not use this strategy for an automatic. If you do have an automatic, you will need a higher-rpm stall converter to go along with all this . I reccomend a 2200-2400 RPM range 2000 comes stock on the 85-86.
Noww if you have an LT1/4, you must effectively copy the same thing said above about the Miniram intake. The intake design is basically equivalent, short runners have the ability to feed a motor very well at high rpm, since the air doesnt have to travel far to get to the chamberr. Thats the L-98s problem and advantage. Long runners means low end torque.
For the manual, 4.10s would be good, possibly lower (higher numerically) depending on your exact cam choice if its not stock. For stock and most street applications, 4.10 would be best. It'll give you a good use for 6th gear without costing mileage, and it'll absolutely roast the tires off the line.
For the automatic, 3.54 or 3.73 is best. The deciding factor between the two, for a street-driven car, is fuel mileage. A highway driven car is going to lose at least 2-3mpg on average from 3.73s in 4th. (if you want to get an idea of how it could be, drive at 70mph on the highway in 3rd) But, 3.73s will be faster 0-60, and in the quarter mile times, so they are optimum for a city car or drag-only car. 3.54s lose less mileage, and you'll still get the jump off the line that the LT1 needs. Combined with a higher stall torque converter, you may be looking at a cut of half-a-second in the quarter mile.
Those are the first mods a LT1/4 driver should do; l before modding into the engine. The camshaft choices all really need the gearing to have been fixed beforehand
Camshaft-the ever-popular LT4 Hotcam is the one recommended most often, for good reason. The kit from GM includes about everything you'll need to install it. The springs in an LT4 are made for the lighter valves it carries, so they
You need to make a plan before you begin anything.
Ask yourself:
What do I want to spend?
What do I want out of the engine when I'm done? (as in HP/TQ numbers or ET)
How much of the work can I do myself?
After you answer these you can begin working to make your goal a reality.
YOU HAVE TO MAKE A PLAN. You cannot throw a bunch of parts together and expect to get some miracle. I KNOW. Thats how I think.
Now this thread is for L-98 and L-T1 motors.
FORCED INDUCTION/NOS**NITROUS OXIDE**
1984 and 85 C4s come with forged TRW pistons from the factory, as holdover parts from the late C3 and these cars will be able to handle more generous amounts of juice. I would start low, say a 50 shot, and go from there. The forged pistons 'may' allow you up to a 150 shot before entering danger zone. Stock compression is low already because of the large 76cc chamber. Be sure to use higher octane gasoline when you are going to be running that much juice however. There is no way to definitely know what to use without a scanner to detect knock counts, and you want to use the lowest octane gasoline you can and not have them.
86-91 C4s use a cast piston, which is not good for juice, so I would only stay in the 50-75 shot area. 92-96's have a hypereutectic piston, which is not much better than cast. These engines also have much higher compression, so you better keep an eye on knock.
Building a motor for NOS
As far as building an engine for extended use with Nitrous, you must use forged pistons and rods, thats pretty much set in stone. These two are going to be taking the brunt of the punishment in the bottom-end. Cranks are very hard to destroy unless you lose oil pressure, and unless you want to spin it above 7000rpm regularly you dont need a forged one.
You would ideally want the engine to be 4-bolt main splayed (thats where a 2-bolt main block has 2 extra bolts drilled into the meat of the block, which is stronger than a regular 4-bolt), and have heads with larger combustion chambers and to have the final compression ratio in the 9.x:1 range
L-98 Motor
This motor is a torque monster. 330 ft/pds of torque STOCK. Low end is this motors strong point. Midrnage-High RPM is where it falls flat on its ***.
Emissions is killing the potential of this car. The L98 is severely choked from the factory in terms of exhaust flow, so this is the #1 place to begin your modifications.
The main catalytic converter is huge piece of ****, used in the 70s erra and is a major restriction on the engine's.
The precat Y-pipe that started in 86 was added to help meet tougher standards in California. 84-85 do not have precats in their front Y pipe.
The AIR system's primary function is to inject O2 into these cats on startup, which helps them to light up quicker and clean emissions soon after startup. Once the engine is hot, the AIR really does nothing. AIR pumps to the manifolds on startup, then switches to the main cat in closed loop.
EGR introduces exhaust gases back into the engine, which lowers combustion chamber temperatures.
Headers:
Long tube headers can give back 15 horsepower to the L-98. You must delete the exaust manifolds and front y pipe.Delete all cats and use a highflow cat such as catco. They only restrict 1-2 horsepower.
I like these headers: Hooker 2149 (with O2 bung, AIR pipes, and EGR, ceramic coated)
Hooker 2151 (no emissions, no bung, uncoated)
Hooker 16720 Y-pipe can be used with either.
Deleting AIR:
Alot of the manufacturers of headers make a set with the AIR pipes deleted. As I said above, AIR only functions on startup until the engine is warm, so you can safely remove it with no ill effects to emissions testing (provided you get the sniffer done when the engine is hot). You can cap off the lines on the headers or not, as the valves are supposed to be one-way only, likewise for the main cat. The AIR eliminator kit sold by many magazines does NOT give you any power, as the AIR pump is a fairly freely-spinning unit, but it does clean up the engine a bit and so is mostly a cosmetic mod. Any connections can be left alone as the L98 does not throw codes when AIR is removed.
Catback:
Any of them should give the same 10-12hp gain. They all vary depending on the sound, shape, looks, ect.Corsa is best for those who do not like resonance (loud droning sound at around 2000rpm usually). There are many brands. The top ones that I reccomend are: Corsa, Borla, B&B, Flowmaster is good for sound but has low flowing capabilities and bad resonance.
Intake
I suggest the miniram If you go this route it will cause you to loose alot of low end torque. It will kick in at about 3000 to 4000 RPMs. It should flow up to 7000 RPMs without issues. The bottom end: Needs to have lighter components, the best parts available for bearings, rods, crank, and pistons. Forged is best for everything. Better have a new oil pump put in too. A larger, deeper pan may be necessary.I suggest using full synthetic oil and upgrading to the larger pan which will help keep everything lubricated and running at optimum.
Top-end: You'll need to get heads with larger ports as they are required to feed the engine at high rpm. 185-200cc would do for a 350. Also, lighter components are best here, with titanium retainers and 10* locks. I think its best to pick springs that are slightly stronger than what is recommended for the camshaft. This will ensure less occurence of problems due to mishaps.
You will need a rev-limiter for this engine, L98s fuel cutoff is set at 10,000rpm. MSD Digital 6 ignition has one built in.
Rear axle: A high-spinning motor will need more rear gear to get you to the power zone, so something in the way of 3.54/3.73/4.10 would be best. This, combined with gas mileage, is why I would not use this strategy for an automatic. If you do have an automatic, you will need a higher-rpm stall converter to go along with all this . I reccomend a 2200-2400 RPM range 2000 comes stock on the 85-86.
Noww if you have an LT1/4, you must effectively copy the same thing said above about the Miniram intake. The intake design is basically equivalent, short runners have the ability to feed a motor very well at high rpm, since the air doesnt have to travel far to get to the chamberr. Thats the L-98s problem and advantage. Long runners means low end torque.
For the manual, 4.10s would be good, possibly lower (higher numerically) depending on your exact cam choice if its not stock. For stock and most street applications, 4.10 would be best. It'll give you a good use for 6th gear without costing mileage, and it'll absolutely roast the tires off the line.
For the automatic, 3.54 or 3.73 is best. The deciding factor between the two, for a street-driven car, is fuel mileage. A highway driven car is going to lose at least 2-3mpg on average from 3.73s in 4th. (if you want to get an idea of how it could be, drive at 70mph on the highway in 3rd) But, 3.73s will be faster 0-60, and in the quarter mile times, so they are optimum for a city car or drag-only car. 3.54s lose less mileage, and you'll still get the jump off the line that the LT1 needs. Combined with a higher stall torque converter, you may be looking at a cut of half-a-second in the quarter mile.
Those are the first mods a LT1/4 driver should do; l before modding into the engine. The camshaft choices all really need the gearing to have been fixed beforehand
Camshaft-the ever-popular LT4 Hotcam is the one recommended most often, for good reason. The kit from GM includes about everything you'll need to install it. The springs in an LT4 are made for the lighter valves it carries, so they
#2
11-10-2006, 12:37 AM
RE: Major mods.....cuz im bored
I was actually looking into a 383 stroker conversion for my '93 LT-1... 440-475 hp depending on accessories, installed for around $5k with the stock motor in trade... I live in C(r)ook County Illinois so our emissions testing is Brutal... Everything has to work, so starting with a ton of HP is mandatory...
Right now in boxes in the living room, I have an SLP triple filter intake, a throttle body "airfoil", and Borla cat-back... It's all waiting for my winter projects to begin Nov. 23rd and beyond (I only carry liability insurance from April to November because I don't drive it in the winter)...
What do you think about Bilstein shocks??? Worth the expense or can I get away with Edelbrocks or Monroes???
Right now in boxes in the living room, I have an SLP triple filter intake, a throttle body "airfoil", and Borla cat-back... It's all waiting for my winter projects to begin Nov. 23rd and beyond (I only carry liability insurance from April to November because I don't drive it in the winter)...
What do you think about Bilstein shocks??? Worth the expense or can I get away with Edelbrocks or Monroes???
#3
11-10-2006, 02:26 AM
RE: Major mods.....cuz im bored
the Bilsteins are awesome. If you want good less expensive ones i would look at KYB's
#4
11-10-2006, 08:54 AM
RE: Major mods.....cuz im bored
Blistein all the way
. Very comfortable ride. If your going to go the cheap way with the KYB theres no point in even trying to upgrade. Eddlebrock is good for "horsepower" but shox? I dont know about that. I heard a rumor a while back about there gas shox either leaking or going bad. That was a long time ago though and its just a rumour but as far as I know they are fine. Best shox IMO...
. Very comfortable ride. If your going to go the cheap way with the KYB theres no point in even trying to upgrade. Eddlebrock is good for "horsepower" but shox? I dont know about that. I heard a rumor a while back about there gas shox either leaking or going bad. That was a long time ago though and its just a rumour but as far as I know they are fine. Best shox IMO...
#5
11-10-2006, 01:12 PM
RE: Major mods.....cuz im bored
I have some bad news for you. Your air foil, does pretty much nothing. Your SLP triple filter intake......IF IM THINKING OF THE SAME INTAKE. It has the same air intake as the Cut lid and K&N filter. It looks nicer if your going for looks but thats about it. Your cat back will give you about 12 horsepower and your intake about 10 so your looking at about 22 BUT the air foil adds 2 or 3 horsepower at PEAK...from what I have seen on test. So about 25 horsepower give or take 1-2 ponies. I mean the exaust is great for the car. If you get headers and the catback together youll get about 30 horsepower. Switch to HIGH FLOW CATS and youll get about 5 more. so about 35. Clean apart your throttle body too. Check out my two sites for information. If your getting a 383 bored and stroked in there I would suggest a miniram which there is info on my site. Better heads and a cam would be another 20 horsepower give or take a little. You have to have a plan though. I think with the 383 with all the right parts you could get 500 horsepower. You do know that your going to have to upgrade your rearend, tranny rebuilt??? Unless you have already done this. If not I would suggest 3.73 gears but with all this power, its going to kill your MPG. I would love to see some pictures when your done Your plan seems very impressive. I wish you the best of luck with it.
Your plan seems very impressive. I wish you the best of luck with it.
#6
11-10-2006, 01:17 PM
RE: Major mods.....cuz im bored
This is what your motor will most likely look like. FYI that cat gutting is from ONE cat. See how restrictive it is. Typing error depending on cats its about 5 horsepower for each cat. So exaust is very important.
[IMG]local://upfiles/3722/99D546A4D9144020A3F28B21EC3B75DF.jpg[/IMG]
[IMG]local://upfiles/3722/0E0DD11AE7B5423F9BE3D62E6B584292.jpg[/IMG]
[IMG]local://upfiles/3722/99D546A4D9144020A3F28B21EC3B75DF.jpg[/IMG]
[IMG]local://upfiles/3722/0E0DD11AE7B5423F9BE3D62E6B584292.jpg[/IMG]
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