300 hp L98?
Burning Brakes
Joined: Jul 2006
Posts: 1,080
Likes: 2
From: Pittsburgh PA
So its a touring car? Like a Jag or a mercedes? I'm not trying to get 500hp or 450 or 400 just a decent 300 ish (ok 285 would be acceptable see I'm learning to accept less) with 300 ish tq. I don't think those are screaming hi #'s. There has got to be a way to do i naturally.
300whp is not screaming high numbers. I dont consider any V8 in the 355-383 range making less than 400whp screaming high numbers. But 300-400whp range makes for a darn quick car if you set up the rest of your suspension and gearing
300 whp naturally aspirated using your heads or better yet, a good seat of heads is possible , i just outlined it for you above
Thread Starter
Burning Brakes
Joined: Aug 2001
Posts: 1,160
Likes: 3
From: Greensboro NC
For the time period, and 80's tech, those numbers arent bad. Full bolt on L98 is a high 12 second car properly setup in a good air conditions track environment.
My HSR on my 89 Fbody L98 put down 254 running very lean. probly 260's tuned up properly but i never got around to it.
If you have a vette, 87 aluminum heads with full exhaust, upgrade your intake to a miniram or superam, or a cut down HSR to fit under the hood, with a hotcam and good tune should put you near 300whp and be very driveable
300 whp is pretty much full bolt on manual trans LT1 motor range, and stock LS1 range. makes for a ok street car. you should have some fun with it. its easy to make with a mild cam and some intake work on your car
YOU NEED A TUNE THO. So before you stick with fuel injection, get someone to tune it for you. If thats not possible then go carbed if you know more about carbs. I just think a factory injected car should stay fuel injected and especially a Corvette
A solid 300+whp combo thats very very driveable is a good set of heads in the 180-195 cc range like AFR 180's or 195's, Brodix IK180's or 200's, Dart pro 1 195's or trick flow 195's combined with a siamesed SLP runner setup on a ported aftermarket base manifold. For the cam use the 218/224 XFI 268 grind. I know that combo is good for 321 on a fbody motor and those numbers are abit lower than anticipated. But that car is docile.
I think a strong budget build is a LT4 hotcam, SLP runner/Siamesed base with stock aluminum L98 heads. Should give you a nice 280-320 whp depending on tune/trans/how far you siamese the base/etc.
If you have money get a good set of heads, miniram, cam similar to the XFI268 and you'll be a quick little vette.
If you have future plans for this car to go faster, then get good heads like AFR 195's/Brodix IK200's/Dart Pro 1's 195-200 cc range and plan to use those heads in the future. They are good for 383's in the 500hp range so you'll be set down the road if you spend the dollar now
My HSR on my 89 Fbody L98 put down 254 running very lean. probly 260's tuned up properly but i never got around to it.
If you have a vette, 87 aluminum heads with full exhaust, upgrade your intake to a miniram or superam, or a cut down HSR to fit under the hood, with a hotcam and good tune should put you near 300whp and be very driveable
300 whp is pretty much full bolt on manual trans LT1 motor range, and stock LS1 range. makes for a ok street car. you should have some fun with it. its easy to make with a mild cam and some intake work on your car
YOU NEED A TUNE THO. So before you stick with fuel injection, get someone to tune it for you. If thats not possible then go carbed if you know more about carbs. I just think a factory injected car should stay fuel injected and especially a Corvette
A solid 300+whp combo thats very very driveable is a good set of heads in the 180-195 cc range like AFR 180's or 195's, Brodix IK180's or 200's, Dart pro 1 195's or trick flow 195's combined with a siamesed SLP runner setup on a ported aftermarket base manifold. For the cam use the 218/224 XFI 268 grind. I know that combo is good for 321 on a fbody motor and those numbers are abit lower than anticipated. But that car is docile.
I think a strong budget build is a LT4 hotcam, SLP runner/Siamesed base with stock aluminum L98 heads. Should give you a nice 280-320 whp depending on tune/trans/how far you siamese the base/etc.
If you have money get a good set of heads, miniram, cam similar to the XFI268 and you'll be a quick little vette.
If you have future plans for this car to go faster, then get good heads like AFR 195's/Brodix IK200's/Dart Pro 1's 195-200 cc range and plan to use those heads in the future. They are good for 383's in the 500hp range so you'll be set down the road if you spend the dollar now
Thank you thats what I needed. The budget build with the LT4 Hotcam sounds right up my alley. If I add the headers and exhaust I should be able get where I want still look (fairly) stock right?
Burning Brakes
Joined: Jul 2006
Posts: 1,080
Likes: 2
From: Pittsburgh PA
Yes i think you can. With the hotcam i would strongly suggest SLP runners if you can find a set of them. Else get some big tube runners and definately siamese the base runners onthe base manifold. you'll gain another 500 rpm of useable power band and that hotcam will like it.
hotcam/TPI stuff is a popular combo since it is a budget setup but makes good power. To pull it off, you need to match that intake to the cam and most long tube runner setups dont go all that well with a hotcam since it likes to make peak power around 5500-5700 on most 350's. TPI is done by 5200 on most big tube setups so its a slight miss match but works ok.
SLP runners with a their semi siamesing combined with a little siamesing on the base manifold (about an inch or so) will compliment that cam much better and give you the 5500 rpms you need.
stock heads should support abit over 300whp. Mild port job on them would be awesome if you could have that done. More head flow is more power so get it done if you can spend the cash
EDIT.. when i mean budget you can find hotcams on ebay/camaroz28.com/thirdgen.org/corvetteforum/etc for well under 150 bucks. most around 100 used. Rollers dont wear so thats a great deal. SLP runners can be found to for under 200 in most places sometimes. but 250 isnt a bad deal considering most other runners are near 400 bucks if not over.
Another option is FIRST TPI. Its HUGE compared to factory and aftermarket TPI's. 1000 bucks gets you base,runner, and throttle body to match. Not a bad deal considering TPI bases are near 350-400, runners near 400, and TB over 200. Almost same price for a inferior system. Get FIRST if you can afford to spend it.
hotcam/TPI stuff is a popular combo since it is a budget setup but makes good power. To pull it off, you need to match that intake to the cam and most long tube runner setups dont go all that well with a hotcam since it likes to make peak power around 5500-5700 on most 350's. TPI is done by 5200 on most big tube setups so its a slight miss match but works ok.
SLP runners with a their semi siamesing combined with a little siamesing on the base manifold (about an inch or so) will compliment that cam much better and give you the 5500 rpms you need.
stock heads should support abit over 300whp. Mild port job on them would be awesome if you could have that done. More head flow is more power so get it done if you can spend the cash
EDIT.. when i mean budget you can find hotcams on ebay/camaroz28.com/thirdgen.org/corvetteforum/etc for well under 150 bucks. most around 100 used. Rollers dont wear so thats a great deal. SLP runners can be found to for under 200 in most places sometimes. but 250 isnt a bad deal considering most other runners are near 400 bucks if not over.
Another option is FIRST TPI. Its HUGE compared to factory and aftermarket TPI's. 1000 bucks gets you base,runner, and throttle body to match. Not a bad deal considering TPI bases are near 350-400, runners near 400, and TB over 200. Almost same price for a inferior system. Get FIRST if you can afford to spend it.
Last edited by Orr89rocz; Nov 2, 2008 at 06:46 PM.
Burning Brakes
Joined: Jul 2006
Posts: 1,080
Likes: 2
From: Pittsburgh PA
Heres some more info for you. A budget build that may fit your goals well. Right in line with what i'm telling you
Thats basically a ZZ4 crate motor with some mild porting done to the heads as mentioned. he's using the stock base with BIG long tube runners and still made 282whp with a mild zz4 cam, another cam you can snag for under 150 bucks, new in some places too! most guys swap out the ZZ4 for the hotcam like below
here he is using a aftermarket base for abit more flow and some more port work to the heads. Good flow gains on the base/head side and he added the hotcam. All that picked up almost 40 whp. The torque gain is great too! over 400wtq is BRUTAL. Cam is usually worth a good 30 whp over the ZZ4 cam on a proper intake setup. He still used the long tube runners which dont feed motors well over 5000 rpms. With superam/miniram or SLP runners that siamesing would have picked up a good 500 rpms of rpm range and power would be closer to 330-340whp or more
350, ported corvette L98 heads, stock ported TPI intake with TPIS/AS&M long tube runners, SLP 1 5/8" headers, ZZ4 camshaft: 282 RWHP, 380 RWTQ.
350, even more ported corvette L98 heads, ported Edelbrock/TPIS intake with TPIS/AS&M runners, Dyno Don 1 3/4" headers, LT4 hot cam: 318 RWHP, 419 RWTQ.
Pro
Joined: May 2002
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From: New Jersey
Instructor
Joined: Sep 2008
Posts: 152
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From: O'Fallon Missouri
another thing to remember throughout all this...... the stock L98 for 87 has 340 on Tq. but paired with 2.59's in the back like I have( Auto) i dont get the same feel of the tq as i would if i had 3.73's.
I agree with the LT4 cam idea with the LT4 springs and ported L98 heads. the only place I would de viate would be either a SR or Miniram intae setup and prom'ed to match the setup. some 24-26lb/hr injectors would romp and stomp like nobodies business. and still be pretty streetable too. Oh i DO love roller cams!!!!!!
I love a good carb, dont get me wrong. I'd take a 1470 cfm predator on a BBC thats built to the hilt over injection any day. However............On a SBC even built and be able to pass a sniffer and be somewhat driveable give me a properly tuned FI setup.
I agree with the LT4 cam idea with the LT4 springs and ported L98 heads. the only place I would de viate would be either a SR or Miniram intae setup and prom'ed to match the setup. some 24-26lb/hr injectors would romp and stomp like nobodies business. and still be pretty streetable too. Oh i DO love roller cams!!!!!!
I love a good carb, dont get me wrong. I'd take a 1470 cfm predator on a BBC thats built to the hilt over injection any day. However............On a SBC even built and be able to pass a sniffer and be somewhat driveable give me a properly tuned FI setup.
Advanced
Joined: Oct 2007
Posts: 84
Likes: 0
From: Naples FL
If you get good flowing heads and keep your compression up near 10 to 1 and a smaller cam with less overlap, the car will drive like stock but have near 100 more whp
300whp is not screaming high numbers. I dont consider any V8 in the 355-383 range making less than 400whp screaming high numbers. But 300-400whp range makes for a darn quick car if you set up the rest of your suspension and gearing
300 whp naturally aspirated using your heads or better yet, a good seat of heads is possible , i just outlined it for you above
300whp is not screaming high numbers. I dont consider any V8 in the 355-383 range making less than 400whp screaming high numbers. But 300-400whp range makes for a darn quick car if you set up the rest of your suspension and gearing
300 whp naturally aspirated using your heads or better yet, a good seat of heads is possible , i just outlined it for you above
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From: Overland Park Kansas
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Maybe "Motorhomes" doesn't know that the LTx engines are not interchangable with L98s. Heads will not interchange.
56cc TFS heads are the smallest off-the-shelf chamber you can buy for L98s. But, the stock head gasket is .051, I'm pretty sure. (Maybe a typo?) 56cc with a .021 gasket would push static compression up to 10:1. 56cc with the stock gasket around 9.7:1.
56cc TFS 175s don't flow quite as well (as OrrocZ's suggested heads), but that's in upper rpms. With the TPI setups, this head is less expensive and would create good low-end response. That's what a TPI is best at anyway.
If the FIRST, miniram or higher flowing intake (than the TPI) is selected, bigger heads can make higher rpms -- and 1/4 mile times faster. You just have to decide if you wanna pull harder til 50-60mph or shoot to higher speeds above that.
You know.... ying/yang.
Instructor
Joined: Jan 2008
Posts: 163
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From: Idianapolis Indiana
Remember hp is a fictional number, its just torque vs rpm. You can have less torque at a higher rpm and have higher horsepower but actually have less power. I know it sounds nonsencical but its true. Ultimately you need to decide what rpm band you want to produce torque in. If you want a high rpm engine then a wound up lt motor will be more your speed. If you want more acceleration and fuel mileage then you should run a modified L98. Here are some good suggestions for building low rpm torque in a L98 platform.
Bolt-ons/simple: Dual 2.5 in exhuast with an H pipe (no cats) and your choice of mufflers. Ceramic Longtube headers with 1&1/2 in primaries and 2.5 in collectors. Msd 6AL and Blaster coil 8mm plug wires. 58mm throttle body. 160 deg T stat/fan switch. Roller rockers 1.6:1 INT 1.5:1 EXH. Custom Prom. No lower than 3.55 rear gear. 1800-2400 rpm stall converter. Disconnect EGR. Move IAT sensor to airbox. Disconnect smog pump from AIR lines, plug lines. Take air cleaner assembly and remove metal shroud on top side of airbox.
Engine work/difficult: Pull intake manifold and fill EGC passage with Sonic weld and cover with stainless steel sheet metal. Install aftermarket non-EGR Alum heads 180-200 cc INT 64cc comb cham. Have machinist balance/blueprint engine. Install 10:1 forged pistons(dont ever for any reason skimp on quality pistons). A wide lsa camshaft with about 2-4 degrees of timing adv(do not use a camshaft with an advertised powerband above 4500 rpm).
And remember the key strength with TPI is it makes far more low rpm torque. Building a high rpm l98 is an excercise in frustration and bankruptcy. Utilize rear gearing/torque conveters that keep the engine in the torque band.
Bolt-ons/simple: Dual 2.5 in exhuast with an H pipe (no cats) and your choice of mufflers. Ceramic Longtube headers with 1&1/2 in primaries and 2.5 in collectors. Msd 6AL and Blaster coil 8mm plug wires. 58mm throttle body. 160 deg T stat/fan switch. Roller rockers 1.6:1 INT 1.5:1 EXH. Custom Prom. No lower than 3.55 rear gear. 1800-2400 rpm stall converter. Disconnect EGR. Move IAT sensor to airbox. Disconnect smog pump from AIR lines, plug lines. Take air cleaner assembly and remove metal shroud on top side of airbox.
Engine work/difficult: Pull intake manifold and fill EGC passage with Sonic weld and cover with stainless steel sheet metal. Install aftermarket non-EGR Alum heads 180-200 cc INT 64cc comb cham. Have machinist balance/blueprint engine. Install 10:1 forged pistons(dont ever for any reason skimp on quality pistons). A wide lsa camshaft with about 2-4 degrees of timing adv(do not use a camshaft with an advertised powerband above 4500 rpm).
And remember the key strength with TPI is it makes far more low rpm torque. Building a high rpm l98 is an excercise in frustration and bankruptcy. Utilize rear gearing/torque conveters that keep the engine in the torque band.
Burning Brakes
Joined: Jul 2006
Posts: 1,080
Likes: 2
From: Pittsburgh PA
So are there heads that you can buy that don't require planing or decking to achieve at least 9.5:1? The ones I see for sale have too large of chambers comparing to the L98 58cc chamber (and stock .021 compressed head gasket!) it seems you would lose your c/r. Are the LT4 and LT1 heads the best bet? ProTopLine is the only ones I've seen below 62cc
If the stock gaskets are .051" thick then your in luck, as you can run a thinner gasket to get compression up and still leave good quench height because factory pistons sit below deck, anywhere from .02 to .025".
If it is .021 which to me would make much more sense since the pistons sit in the bore alittle ways, then your out of luck and need to run smaller chambers via milling them down.
I do believe AFR and possibly Dart will make the heads to your combustion chamber spec for a small fee. I have heard this but i dont know for sure. If you cant get them to do it, getting a 64-65cc, you probly can only take it down to 60 cc without having a super thin deck
Properly setup with the right intake and cam, stock L98 heads should support 300whp. There are factory stock racing classes in which you need to use stock heads and guys have gotten alot of power out of setups like that. Not so much streetable anymore but possible to make power
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From: Naples FL
So we're talking about the Trick Flow "Super 23"?? It looks like they are similar flow to the vortecs.. (Sorry for the newbie-ism)
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From: Valparaiso
Remember hp is a fictional number, its just torque vs rpm. You can have less torque at a higher rpm and have higher horsepower but actually have less power. I know it sounds nonsencical but its true. Ultimately you need to decide what rpm band you want to produce torque in. If you want a high rpm engine then a wound up lt motor will be more your speed. If you want more acceleration and fuel mileage then you should run a modified L98. Here are some good suggestions for building low rpm torque in a L98 platform.
Bolt-ons/simple: Dual 2.5 in exhuast with an H pipe (no cats) and your choice of mufflers. Ceramic Longtube headers with 1&1/2 in primaries and 2.5 in collectors. Msd 6AL and Blaster coil 8mm plug wires. 58mm throttle body. 160 deg T stat/fan switch. Roller rockers 1.6:1 INT 1.5:1 EXH. Custom Prom. No lower than 3.55 rear gear. 1800-2400 rpm stall converter. Disconnect EGR. Move IAT sensor to airbox. Disconnect smog pump from AIR lines, plug lines. Take air cleaner assembly and remove metal shroud on top side of airbox.
Engine work/difficult: Pull intake manifold and fill EGC passage with Sonic weld and cover with stainless steel sheet metal. Install aftermarket non-EGR Alum heads 180-200 cc INT 64cc comb cham. Have machinist balance/blueprint engine. Install 10:1 forged pistons(dont ever for any reason skimp on quality pistons). A wide lsa camshaft with about 2-4 degrees of timing adv(do not use a camshaft with an advertised powerband above 4500 rpm).
And remember the key strength with TPI is it makes far more low rpm torque. Building a high rpm l98 is an excercise in frustration and bankruptcy. Utilize rear gearing/torque conveters that keep the engine in the torque band.
Bolt-ons/simple: Dual 2.5 in exhuast with an H pipe (no cats) and your choice of mufflers. Ceramic Longtube headers with 1&1/2 in primaries and 2.5 in collectors. Msd 6AL and Blaster coil 8mm plug wires. 58mm throttle body. 160 deg T stat/fan switch. Roller rockers 1.6:1 INT 1.5:1 EXH. Custom Prom. No lower than 3.55 rear gear. 1800-2400 rpm stall converter. Disconnect EGR. Move IAT sensor to airbox. Disconnect smog pump from AIR lines, plug lines. Take air cleaner assembly and remove metal shroud on top side of airbox.
Engine work/difficult: Pull intake manifold and fill EGC passage with Sonic weld and cover with stainless steel sheet metal. Install aftermarket non-EGR Alum heads 180-200 cc INT 64cc comb cham. Have machinist balance/blueprint engine. Install 10:1 forged pistons(dont ever for any reason skimp on quality pistons). A wide lsa camshaft with about 2-4 degrees of timing adv(do not use a camshaft with an advertised powerband above 4500 rpm).
And remember the key strength with TPI is it makes far more low rpm torque. Building a high rpm l98 is an excercise in frustration and bankruptcy. Utilize rear gearing/torque conveters that keep the engine in the torque band.
i like this post !
Le Mans Master
Joined: Aug 2000
Posts: 8,838
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From: Australia
L98 performance in a nutshell.Buy some DR's ; you will need them.
My old setup
100K unopened L98 , ZZ4 cam and springs , home siamized base and ported plenum,Big tubes , headers ,stock stall , 3.07
13.00X all day