300hp L98
Thread Starter
Instructor
Joined: Sep 2012
Posts: 204
Likes: 3
From: Bristol Rhode Island
300hp L98
How do i get there/w an '89 L98.I once had a steel cranked,Dart headed,10.5:1 Forged piston,Crane cammed/roller rocked,750 Holley'd 350 that i swear met that.
How do we begin modding this L98 to achieve 300hp? On a budget of $5000 MAX
How do we begin modding this L98 to achieve 300hp? On a budget of $5000 MAX
Melting Slicks
Joined: Jan 2009
Posts: 3,181
Likes: 286
From: Puyallup Washington
Do you want 300 at the crank or the rear wheels?
Heads, cam, rockers, springs, intake and long tube headers and exhaust should get you close to 300 at the crank.
For 300 at the rear wheels you will need to go forced air (turbos or supercharger) or nitrous.
You can also consider bore and stroke.
The above is my opinion based on what I have read.
Heads, cam, rockers, springs, intake and long tube headers and exhaust should get you close to 300 at the crank.
For 300 at the rear wheels you will need to go forced air (turbos or supercharger) or nitrous.
You can also consider bore and stroke.
The above is my opinion based on what I have read.
Burning Brakes
Joined: Aug 2005
Posts: 1,172
Likes: 9
From: '88 TPI L98/HotCam Powell, Ohio
These are steps that I have seen on my '88 L98 on the Dyno:
1) Headers/Exhaust = 250 whp
add 1.65 Roller Rockers to pick up another ~5-10
2)Above plus:
CNC Ported heads
TPIS Big Mouth Base w/ Accel runners
HotCam
24lb SVO injectors
= 325 whp
3) Above but swapped intake to Holley Stealth Ram and 5.5" clutch
= 375 whp
Matt
1) Headers/Exhaust = 250 whp
add 1.65 Roller Rockers to pick up another ~5-10
2)Above plus:
CNC Ported heads
TPIS Big Mouth Base w/ Accel runners
HotCam
24lb SVO injectors
= 325 whp
3) Above but swapped intake to Holley Stealth Ram and 5.5" clutch
= 375 whp
Matt
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Joined: Apr 2011
Posts: 3,660
Likes: 22
300?
thats pretty easy.
You have 300 at the crank NOW....240 RWHP...maybe little less.
Rule: crank HP will be 20% less at rear wheels.
headers, mild porting, roller rockers, cam, tune. Viiola ! 300 rwhp.
Easy.
That list of stuff another member posted...if he had to do all that to get past 300 then he forgot to do the "tune" when it was all done. 300 is EASY. 400 is where it really starts getting expensive.
thats pretty easy.
You have 300 at the crank NOW....240 RWHP...maybe little less.
Rule: crank HP will be 20% less at rear wheels.
headers, mild porting, roller rockers, cam, tune. Viiola ! 300 rwhp.
Easy.
That list of stuff another member posted...if he had to do all that to get past 300 then he forgot to do the "tune" when it was all done. 300 is EASY. 400 is where it really starts getting expensive.
Burning Brakes
Joined: Aug 2005
Posts: 1,172
Likes: 9
From: '88 TPI L98/HotCam Powell, Ohio
300?
thats pretty easy.
You have 300 at the crank NOW....240 RWHP...maybe little less.
Rule: crank HP will be 20% less at rear wheels.
headers, mild porting, roller rockers, cam, tune. Viiola ! 300 rwhp.
Easy.
That list of stuff another member posted...if he had to do all that to get past 300 then he forgot to do the "tune" when it was all done. 300 is EASY. 400 is where it really starts getting expensive.
thats pretty easy.
You have 300 at the crank NOW....240 RWHP...maybe little less.
Rule: crank HP will be 20% less at rear wheels.
headers, mild porting, roller rockers, cam, tune. Viiola ! 300 rwhp.
Easy.
That list of stuff another member posted...if he had to do all that to get past 300 then he forgot to do the "tune" when it was all done. 300 is EASY. 400 is where it really starts getting expensive.
Hmmm, never realized an '89 TPI came with 300 hp.....
Thread Starter
Instructor
Joined: Sep 2012
Posts: 204
Likes: 3
From: Bristol Rhode Island
I also have a 2012 HEMI 6sp Challenger.I have known power.My '89 satisfies me.We just pulled it yesterday and my friend(of some 35 years) is egging me that NOW is the time to consider performance mods.We're going to hot tank it so,it will get a hone and new bearings/rings.But what else? We're considering options.The responses are GREAT and informative.
As a machinist of 32 years,this build will be fun no matter the state of tune
As a machinist of 32 years,this build will be fun no matter the state of tune
Drifting
Joined: Nov 2012
Posts: 1,331
Likes: 2
300 ponies should be pretty easy to cough up. Runners, new high flow lower manifold, ported plenum, long tube headers, x pipe high flow cats and mufflers should get you there with some room to spare.
Now if you really want to get nutso. Just get a 383 off of ebay, port the manifold and get some runners, and headers. You'll be pushing even more ponies pretty easy then.
Now if you really want to get nutso. Just get a 383 off of ebay, port the manifold and get some runners, and headers. You'll be pushing even more ponies pretty easy then.
Race Director
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From: Rolla Missouri
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Verdad Gallardo
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Joined: Apr 2011
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You DO understand the difference between CHP and RWHP, right?
Crank HP is easy. Thats what you get when you buy a crate motor. People run up and talk all about their new 350 hp bowtie motor or zz or whatever...yessir, its 350hp....AT THE CRANKSHAFT. Not at the rear wheels where a min of 20% is lost due to parasitic drag from drivetrain , wheels and suspension. After the motor has wasted a BUNCH of available hp to just turn all that dead weight...the 350hp suddenly turns into less than 280....at the wheels were it counts.
So yeah, the L98s of the 80's most likely did come with 300hp...at the crankshaft where the GM folks could NOT advertise it...because of the fed DOT laws that required vehicles to be rated at BHP, or Brake HP that was measured at the WHEELS.
The advertised HP rating for ANY American production car is RWHP or BHP...so the L98s all had somewhere around 240 hp on the sticker. THATS how they are rated. Thats accurate. Crank HP does nobody ANY good unless you get as much of that to the ground as possible. 300 at the crank is very easy...but to get that to the pavement in a car this heavy? subtract 20-25% and thats whats left. Thats what is allowed by law to be advertised.
see? learning is fun
Crank HP is easy. Thats what you get when you buy a crate motor. People run up and talk all about their new 350 hp bowtie motor or zz or whatever...yessir, its 350hp....AT THE CRANKSHAFT. Not at the rear wheels where a min of 20% is lost due to parasitic drag from drivetrain , wheels and suspension. After the motor has wasted a BUNCH of available hp to just turn all that dead weight...the 350hp suddenly turns into less than 280....at the wheels were it counts.
So yeah, the L98s of the 80's most likely did come with 300hp...at the crankshaft where the GM folks could NOT advertise it...because of the fed DOT laws that required vehicles to be rated at BHP, or Brake HP that was measured at the WHEELS.
The advertised HP rating for ANY American production car is RWHP or BHP...so the L98s all had somewhere around 240 hp on the sticker. THATS how they are rated. Thats accurate. Crank HP does nobody ANY good unless you get as much of that to the ground as possible. 300 at the crank is very easy...but to get that to the pavement in a car this heavy? subtract 20-25% and thats whats left. Thats what is allowed by law to be advertised.
see? learning is fun
Last edited by leesvet; Mar 18, 2013 at 11:27 AM.
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,009
From: Texas
You DO understand the difference between CHP and RWHP, right?
Crank HP is easy. Thats what you get when you buy a crate motor. People run up and talk all about their new 350 hp bowtie motor or zz or whatever...yessir, its 350hp....AT THE CRANKSHAFT. Not at the rear wheels where a min of 20% is lost due to parasitic drag from drivetrain , wheels and suspension. After the motor has wasted a BUNCH of available hp to just turn all that dead weight...the 350hp suddenly turns into less than 280....at the wheels were it counts.
So yeah, the L98s of the 80's most likely did come with 300hp...at the crankshaft where the GM folks could NOT advertise it...because of the fed DOT laws that required vehicles to be rated at BHP, or Brake HP that was measured at the WHEELS.
see? learning is fun
Crank HP is easy. Thats what you get when you buy a crate motor. People run up and talk all about their new 350 hp bowtie motor or zz or whatever...yessir, its 350hp....AT THE CRANKSHAFT. Not at the rear wheels where a min of 20% is lost due to parasitic drag from drivetrain , wheels and suspension. After the motor has wasted a BUNCH of available hp to just turn all that dead weight...the 350hp suddenly turns into less than 280....at the wheels were it counts.
So yeah, the L98s of the 80's most likely did come with 300hp...at the crankshaft where the GM folks could NOT advertise it...because of the fed DOT laws that required vehicles to be rated at BHP, or Brake HP that was measured at the WHEELS.
see? learning is fun
The L98s were all rated at 250 SAE Net Crankshaft hp...or less depending on year. It wasn't until the LT1 that the SBC hit 300 SAE Net Crankshaft hp. The LT5 was rated at 375 in 1990 and ultimately 405 in later years.
The rating process is quite elaborate and involves a fully dressed engine with a full exhaust system on a test stand. There's not a car or driveline to be found.
GM has NEVER rated or sold cars based on rear wheel horsepower. SAE Net or Gross at the crank.
Race Director
Joined: Oct 2005
Posts: 11,771
Likes: 177
From: Rolla Missouri
2021 C4 of the Year - Unmodified Finalist
St. Jude Donor '10 thru '25
You DO understand the difference between CHP and RWHP, right?
Crank HP is easy. Thats what you get when you buy a crate motor. People run up and talk all about their new 350 hp bowtie motor or zz or whatever...yessir, its 350hp....AT THE CRANKSHAFT. Not at the rear wheels where a min of 20% is lost due to parasitic drag from drivetrain , wheels and suspension. After the motor has wasted a BUNCH of available hp to just turn all that dead weight...the 350hp suddenly turns into less than 280....at the wheels were it counts.
So yeah, the L98s of the 80's most likely did come with 300hp...at the crankshaft where the GM folks could NOT advertise it...because of the fed DOT laws that required vehicles to be rated at BHP, or Brake HP that was measured at the WHEELS.
see? learning is fun
Crank HP is easy. Thats what you get when you buy a crate motor. People run up and talk all about their new 350 hp bowtie motor or zz or whatever...yessir, its 350hp....AT THE CRANKSHAFT. Not at the rear wheels where a min of 20% is lost due to parasitic drag from drivetrain , wheels and suspension. After the motor has wasted a BUNCH of available hp to just turn all that dead weight...the 350hp suddenly turns into less than 280....at the wheels were it counts.
So yeah, the L98s of the 80's most likely did come with 300hp...at the crankshaft where the GM folks could NOT advertise it...because of the fed DOT laws that required vehicles to be rated at BHP, or Brake HP that was measured at the WHEELS.
see? learning is fun
The GM factory advertised HP numbers for their production cars is based at the flywheel, not at the rear wheels.
So, a factory L98 Corvette engine is rated at 240 HP
And that is not at the rear wheels.
Race Director
Joined: Oct 2005
Posts: 11,771
Likes: 177
From: Rolla Missouri
2021 C4 of the Year - Unmodified Finalist
St. Jude Donor '10 thru '25
The advertised HP rating for ANY American production car is RWHP or BHP...so the L98s all had somewhere around 240 hp on the sticker. THATS how they are rated. Thats accurate. Crank HP does nobody ANY good unless you get as much of that to the ground as possible. 300 at the crank is very easy...but to get that to the pavement in a car this heavy? subtract 20-25% and thats whats left. Thats what is allowed by law to be advertised.
see? learning is fun
see? learning is fun
Burning Brakes
Joined: Aug 2005
Posts: 1,172
Likes: 9
From: '88 TPI L98/HotCam Powell, Ohio
I'm always willing to learn...I was under the impression that this had something to do with how hp ratings were given:
SAE Net Horspower In 1972, American manufacturers phased in SAE net horsepower. This is the standard on which current American ratings are based. This rating is measured at the flywheel, on an engine dyno, but the engine is tested with all accessories installed, including a full exhaust system, all pumps, the alternator, the starter, and emissions controls. Both SAE net and SAE gross horsepower test procedures are documented in Society of Automotive Engineers standard J1349. Because SAE net is so common, this is the standard we will use to compare all others.
I'm assuming there should be a lot of dyno runs on the net with stock L98's making 240 whp? Assuming they made 300 hp from the factory ahe??
I could only find them making 208-2112 whp....hmmmmm. Wierd.
SAE Net Horspower In 1972, American manufacturers phased in SAE net horsepower. This is the standard on which current American ratings are based. This rating is measured at the flywheel, on an engine dyno, but the engine is tested with all accessories installed, including a full exhaust system, all pumps, the alternator, the starter, and emissions controls. Both SAE net and SAE gross horsepower test procedures are documented in Society of Automotive Engineers standard J1349. Because SAE net is so common, this is the standard we will use to compare all others.
I'm assuming there should be a lot of dyno runs on the net with stock L98's making 240 whp? Assuming they made 300 hp from the factory ahe??
I could only find them making 208-2112 whp....hmmmmm. Wierd.
Race Director
Joined: Nov 2003
Posts: 12,221
Likes: 446
From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
You DO understand the difference between CHP and RWHP, right?
The advertised HP rating for ANY American production car is RWHP or BHP...so the L98s all had somewhere around 240 hp on the sticker. THATS how they are rated. Thats accurate. Crank HP does nobody ANY good unless you get as much of that to the ground as possible. 300 at the crank is very easy...but to get that to the pavement in a car this heavy? subtract 20-25% and thats whats left. Thats what is allowed by law to be advertised.
see? learning is fun
The advertised HP rating for ANY American production car is RWHP or BHP...so the L98s all had somewhere around 240 hp on the sticker. THATS how they are rated. Thats accurate. Crank HP does nobody ANY good unless you get as much of that to the ground as possible. 300 at the crank is very easy...but to get that to the pavement in a car this heavy? subtract 20-25% and thats whats left. Thats what is allowed by law to be advertised.
see? learning is fun
<insert sound of woody-woodpecker here>
My head hurts!
Read post #14 for even more-better learning.
Race Director
Joined: Nov 2003
Posts: 12,221
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From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
Stroke it, with cam/header/intake/exhaust, and you've got a whole lotta fun! Way more than the 300 you were asking about.
FWIW, some swap to a 4-bolt block (stock equip in late 80's trucks). Of course, you can also splay the stock block (add 2 more bolts). Unless you go crazy and spin it much above 6k rpms, the stock block is fine.
Drifting
Joined: Nov 2012
Posts: 1,331
Likes: 2
http://67-72chevytrucks.com/vboard/s...d.php?t=425093
Longer stroke.
Hence why it's also called a stroker.
401 and 406s are also popular swaps too these days in the SBC crowd.
I know the 383 is a fairly bulletproof design (especially with a TPI on it) in terms of reliability. I got to ride in a hard launched 383 TPI car once, that had a 2200 stall converter in it. The experience sold me on TPI in general for daily, occasional autocross, and drag strip use. You can nail mid 11s pretty safely with a TPI, and 383 combo without even going to Vortec heads. Pretty insane really.
Team Owner
Joined: Dec 2000
Posts: 21,094
Likes: 282
From: Phila., PA burbs
I'm always willing to learn...I was under the impression that this had something to do with how hp ratings were given:
SAE Net Horspower In 1972, American manufacturers phased in SAE net horsepower. This is the standard on which current American ratings are based. This rating is measured at the flywheel, on an engine dyno, but the engine is tested with all accessories installed, including a full exhaust system, all pumps, the alternator, the starter, and emissions controls. Both SAE net and SAE gross horsepower test procedures are documented in Society of Automotive Engineers standard J1349. Because SAE net is so common, this is the standard we will use to compare all others.
I'm assuming there should be a lot of dyno runs on the net with stock L98's making 240 whp? Assuming they made 300 hp from the factory ahe??
I could only find them making 208-2112 whp....hmmmmm. Wierd.
SAE Net Horspower In 1972, American manufacturers phased in SAE net horsepower. This is the standard on which current American ratings are based. This rating is measured at the flywheel, on an engine dyno, but the engine is tested with all accessories installed, including a full exhaust system, all pumps, the alternator, the starter, and emissions controls. Both SAE net and SAE gross horsepower test procedures are documented in Society of Automotive Engineers standard J1349. Because SAE net is so common, this is the standard we will use to compare all others.
I'm assuming there should be a lot of dyno runs on the net with stock L98's making 240 whp? Assuming they made 300 hp from the factory ahe??
I could only find them making 208-2112 whp....hmmmmm. Wierd.
If I recall correctly my L98 made around 210 hp at the wheels when it was stock.