“Best” is kinda of a relative thing since hp didn't really change much more than 10-15 hp over the whole L98 line. But, if I were to look for a specific one, it would have to have the 113 heads (aluminum) which means a convertible in 86, i believe it was 87 or 88 that all vettes got the 113 heads.
After that, it’s pretty much dealers choice. 89 and up did away with the cold start injector, which is one less thing to go wrong.
L98’s are mostly MAF cars, which means it’s a little more “flexible” when it cones to modifying the car. The maf is reported to be a restriction when you start making serious HP, so some guys switch to speed density. I think it was 90-92 the vette L98 came soeed density fron the factory and then changed back to MAF. Maf sensors are also expensive to replace.
If looking for a manual transmission, I’d go 89 or newer as the 6 speed was offered in 89+ cars.
I wouldn’t go okder than 88 myself. Not for the engine, but for the chassis. They changed a lot in 88. Like going to a zero scrub radius, bigger brakes, etc.
I’d also look for a Z51 or Z52 optioned car. Z51 can be a little “stiff” for sone people, but a z52 gets you all the z51 goodies but softer springs. Convertibles coukd only get the Z52, z51 was not offered on verts.
Lots of other differences throughout the production run. Go and google “c4 corvette buying” and you’ll find lots of reading on the subject.
I just bought my 88 L98 convertible z52 car this summer. 9500 and I had to fix a few things (master cylinder, wipers, etc).
You can find them around 8 grand, but you’re probably going to have to fix a few things or accept some “flaws”. You can find them lower, but tou’re getting into some pretty thrashed rides that low...
Last edited:
I like my L98, but if you have any inclination to build it for more hp, I’d look for an LT1 engined C4.L98’s are stuck around the 250hp mark and it takes a fair bit of work and cash to even get 300hp out of them.
LT1 engines start around 300-330 hp and making 350 with one is a pretty easy job. The LT1 was the step between the traditional small block chev and the LS series. Over the L98, it had reverse flow cooling, better heads, better intake, better exhaust, better ecm, etc. An LT1 can be made to go pretty fast for fairly cheap cash outlay. It is rumored that GM intentionally kept the LT1 hp “lower” as they didn’t want it to compete with the pricey ZR1’s dohc cam LT5. The only real issue with the lt1 was the optispark “distrubutor”. Early ones were sensitive to moisture intrusion. Later lt1’s got a vented distributor unit, which pretty much did away with water issues. They still fail, but everything will fail eventually.
Overall, you really want the car thats in the best shape for your money....then look at options and drivetrains. Make sure you get whatever you are looking at up on a rack and give the undeside a good going over. Pay particular attention to the galvanized “frame”. Canadian climate is hard on a car (even a fiberglass vette) and ontario/quebec is rough on them for the same reason NS is: salted roads.
The only C4 that I wouldn’t consider is the 84 with the crossfire engine. There’s a lot of “1 year” things on the 84 that will be a total biotch to find/fix. 84 was the inly year the C4 got the crissfire engine and while it can be very reliable, its stuck in “low power land” without any real options to make more hp unless you buy some pretty rare performance parts (and still be stuck in “lo po” land) or do an engine swap. Best just to give the 84 c4 a total “pass” IMHO.
Keep in mind that these cars are 30+ years old now. Things break and wear out. The generic GM stuff (tps, thermostat, mufflers, etc) in a Vette isn’t too hard to find and won’t break the bank to buy. But anything that is specific to the Vette is hard to find now and most of it is discontinued from GM. Being a vette, most of it is acailable aftermarket, but you're going to pay through the nose to get it.C4 Vette’s are best used as sunny day fun cars at this point. You can daily drive one, but it’s not going to be cheap to fix it when it breaks. And it WILL break....
The c4 interiors also changed through the years. I believe it was 1990 they got the more “wrap around cockpit” look. Before that, you get the (what is lovongly refered to by c4 enthusiats as) the “Atari dash”. Basically, it’s all bar graphs and led’s. The newer stule gets some analog needles, the older is all digital. Mine is digital and I like it. It’s a personal preference.
“Atari” dash:
“Cockpit” dash:
Personally, I prefer the Atari dash. The 90+ dash looks too much like the “pontiac” look of that era. At least the Atari dash doesn’t look like sonething else, there’s no mistaking it for anything but a C4 dash.
Like I said though, it’s a personal preference. Just as many people don’t like the “atari” dash.
Last edited:
- Thread starter
- #5
wow this forum application is too Nice and you are a real bible ahahah thanks a lot for ure recommandation i will consider when im gonna Buy it ... And for sure i prefare the lt1 engine but they cost more than i Wanna pay ...my plan is more clear now im Will try to find a 89-90 manual Targa and try every thing i can to get extra juice ....i Seen many cheap tip to gain micro Horse Power like
1. open the air box
2.k&n air Filter
3.unsreened the Mad
4.bypass coolant on throtlebody
5. remove the air pump
6. bypass precat
7. remove the heavy freeze on poolies
8. magna flow exhaust
9. add an air foil on the throtlebody
10. polish the edge on the intake tube
overall its what i expect ...u look to now what u talk about so im interest to have ur opinion
thank again my Friend
1. open the air box
2.k&n air Filter
3.unsreened the Mad
4.bypass coolant on throtlebody
5. remove the air pump
6. bypass precat
7. remove the heavy freeze on poolies
8. magna flow exhaust
9. add an air foil on the throtlebody
10. polish the edge on the intake tube
overall its what i expect ...u look to now what u talk about so im interest to have ur opinion
thank again my Friend
The translation is funny, so it's okay!
I agree with the above statements about an LT1, it really is the best choice and is undoubtedly the best bargain even at a higher price. Change your budget and do it. It's worth it.
I would love to get my hands on a 96 Grandsport with the LT4 and a 6-speed, but that is because I am a Corvette nut and that is the best of the C4s, unless you have the money to maintain an LT5 ZR1.
But the real question of this thread is which is the best year of the L98?
1989, when a twin-turbo Callaway Corvette called 'Sledgehammer' set the world speed record for street legal production cars at 254.76 mph, and held that title for 10 years - well above the likes of Ferrari and Lamborghini, and even the McLaren F1 couldn't touch it. This is what made the Bugatti Veyron famous. Well, that and it's astronomical price - whereby Bugatti was still losing money.
I agree with the above statements about an LT1, it really is the best choice and is undoubtedly the best bargain even at a higher price. Change your budget and do it. It's worth it.
I would love to get my hands on a 96 Grandsport with the LT4 and a 6-speed, but that is because I am a Corvette nut and that is the best of the C4s, unless you have the money to maintain an LT5 ZR1.
But the real question of this thread is which is the best year of the L98?
1989, when a twin-turbo Callaway Corvette called 'Sledgehammer' set the world speed record for street legal production cars at 254.76 mph, and held that title for 10 years - well above the likes of Ferrari and Lamborghini, and even the McLaren F1 couldn't touch it. This is what made the Bugatti Veyron famous. Well, that and it's astronomical price - whereby Bugatti was still losing money.
I answered your questions in red above. I would be surprised if you saw more than 10-15 hp with all that stuff. A lot of people look at performance modifications and try to add up all the numbers.IE: 10 Hp claim from a K&N filter with a 5 hp claim for a TB airfoil plus a 15 hp claim from a CAI =30 HP increase, right? Nope, 5-10 HP if you are lucky. They don't add up for each change, it just doesn't work that way. The "claims" each one makes are also usually "inflated" by the manufacturers who are (lets be honest here) trying to sell you something.wow this forum application is too Nice and you are a real bible ahahah thanks a lot for ure recommandation i will consider when im gonna Buy it ... And for sure i prefare the lt1 engine but they cost more than i Wanna pay ...my plan is more clear now im Will try to find a 89-90 manual Targa and try every thing i can to get extra juice ....i Seen many cheap tip to gain micro Horse Power like
1. open the air box - won't see much, maybe a couple HP. I've got an SLP "cold air" intake on mine, was in there when I bought the car.
2.k&n air Filter - again, a couple hp at best. Biggest advantage is it's "cleanable". Have one in mine, no real seat of the pants increase.
3.unsreened the Mad - Best just to leave it alone on a street car. A screened MAF already passes more CFM than a stock L98 can use. Better use of your time is to make sure the MAF wire stays clean, especially with a K&N filter. They can "oil" the MAF wire, which causes false readings. Don't touch the wire, just hit it with MAF cleaner once or twice a year.
4.bypass coolant on throtlebody - Meh, jury is out on that one. The change in air density is minimal. Any gains are pointless unless you change the tune to add more fuel and honestly, it probably doesn't make enough difference to warrant a calibration change anyways.
5. remove the air pump - No real point. You loose the emmisions function of it, need a shorter belt if you don't install a replacement pulley and if you are lucky, gain 1-2 hp at best.
6. bypass precat - bypass? you mean remove?if your cat isn't malfunctioning or clogged, it's not going to make much difference. You'll get more gains out of a set of headers that better match the "D" shaped ports on the 113 heads. OEM headers have a square opening, which blocks part of the 113 exhaust ports.
7. remove the heavy freeze on poolies - not exactly sure what you mean by this? If you're talking about hte "damper" on the water pump pulley, GM put it there to dampen vibrations that crack the AC bracket. You can take it off though, I took mine off. Doesn't free up a lot of HP (5 or so if lucky), but the throttle response gets a little better.
8. magna flow exhaust - not a bad idea, but it's mostly for sound. You'll get 10 HP if you're lucky. The real issues in the C4 exhaust starts at those crappy headers and center section, which kills the flow before you even get to the "cat back".
9. add an air foil on the throtlebody - jury is mostly split on this one. Some say it helps, other think it's just added weight. I've got one on my vette simply becuase I had it laying around from long ago. Didn't notice any difference once installed.
10. polish the edge on the intake tube - Not sure what you are trying to say here.
overall its what i expect ...u look to now what u talk about so im interest to have ur opinion
thank again my Friend
A lot of guys find that out after spending the moneythat the claims either only hit the low claim (or nearly nothing at all), which is just disappointing. The thing is; what these items are is "details". They are meant to support modifications, but they're not really modifications of any consequence on their own. You have to make changes to the major parts to see any real gains from these "bolt on" bits. Look at it this way: If GM could have grabbed another 10 hp for their (at the time) flagship model with just a larger/more open air intake, they would have done it to not be embarassed by those Camaro or Mustang boys (not to mention the "eurocras" they were claiming was thier intended competitors)......but they didn't, so.........
To make big HP gains on an L98, you're talking new heads, cams, roller rockers, intake, full exhaust, etc. The TPI is a great little street car torque monster, which is what makes it so fun. Dropping the hammer from a start (or low RPM) on my L98 shoves you back in the seat like hitting AB on takeoff in a CF 18. But it falls on it's face around 4500-4800 RPM,right about where most engines start making their big HP numbers.
Grabbing 300 HP in an L98 means (at a minimum) things like replacing the TPI intake (or having it heavily reworked or buying something like the FIRST TPI manifold-over a grand for that one alone), doing a full exhaust (from heads to tailpipe) and camming it up.Then you're probably going to have to get into datalogging and burning new chips to get it to run right, or at least to it's full potential.
There's just no cheap way to make any real HP with an L98. But the L98 makes a FANTASTIC cruiser. Lots of grunt down low and just an overall very relaxed, under-stressed lump. But best look elsewhere if you want big HP numbers, or prepare to open your wallet.......WIDE! That's why I suggested looking for an LT1, if you have HP building in mind. It's just cheaper in the long run.
I'm not really a "bible". I know a few things about the C4's, but not everything. Just general info, mostly because I have one.
Last edited:
An LT4 grandsport is going to go for serious cash, or at least too much for the OP budget. If they're not already pushing ZR1 prices, I'll wager they will be soon. Great C4 though. Could have been an LT5 killer had they worked it up as far as it's potential would take it. Even stock, an LT4 can make and LT5 nervously look over it's shoulder and sweat pretty hard to stay ahead. Breath a little on an LT4 and I'll lay money on it being able to stomp a stock ZR1/LT5.....
LT5/ZR1 is going to command somewhere in the 20G CAD range, and that's just to start.... that's out.
The Callaway cars were monsters, made to fil the gap until GM could get the ZR1/LT5 off the launch pad. The engine itself wasn't much more than a production L98, it was the twin turbo's that made it a monster. Callaway's are like ZR1's; expensive as hell. Assuming you can find one for sale. That 248 mph was also with the "sledgehammer" Callaway. The Sledgehammer was mostly a prototype, they only built the one but everyone quote the sledhammer top speed for every Callaway C4. The "sledgehammer" had specially designed tires to run that record (reported cost 1 million to design them and they were supposedly good to 300 mph). "Normal" Callaway's got the conventional tires for the time, which were Z rated which limited you to 149 mph (240 KPH). Z rated is 149 mph, but they could go over. However, no manufacturer would say how much over or for how long you could run them over 149 mph. Still, for a street car, 149 mph is pretty much a useless number. You could do 149 on public roads, but someone should beat your ass silly if you did.....and then chuck you in jail. Those are track numbers and should only be explored on a closed track.
So, best L98 I would say is just about any of them from 88-1991.I'd stay away from the 86/87 L98 with aluminum heads , they were the design before the "D" shaped exhaust ports, which flowed much better than the early aluminum heads. Early L98 aluminum heads (86/87) were designed the same as the Iron L98 heads, so they had square ports, which flow less than the D ports.
Hmmm, maybe I know more about L98 C4 Vettes than I thought I did.......
Last edited:
- Thread starter
- #11
thanks for you anwser guys i really appreciate ....so i Will pray to find a Nice lt1 and maybe get more budget for it ...cause i didnt want to be embarassed by a Civic si ...i really love the cheap of the vette but i swear a minimum of performance ...juste to give me a reference witch model you have and have to try it on a 0-100 or a 1/4 mile and again really happy to see the interest u give to many noob question
My advice would be to stop worrying about a civic SI, or any other car for that matter, "embarrassing" you. All it takes (in any car) is a driver who's a little bit better than you to be "faster" or "quicker" in a car that's actually slower than yours. There's a lot of import guys running around out there with stock appearances but absolutely ridiculous horsepower. I personally know of a couple Honda's running 400-500 hp around here and they're absolute monsters. No indication they can run 11-12's until you try to drop the hammer on one. It's the combination of light weight and "no foolin" HP that makes those little rice burners so dangerous.....thanks for you anwser guys i really appreciate ....so i Will pray to find a Nice lt1 and maybe get more budget for it ...cause i didnt want to be embarassed by a Civic si ...i really love the cheap of the vette but i swear a minimum of performance ...juste to give me a reference witch model you have and have to try it on a 0-100 or a 1/4 mile and again really happy to see the interest u give to many noob question
Get the best car you can for your money (ie: condition) and one that you personally like. One that makes you turn around to look at it as you walk away. There's always someone out there faster (and these days, it can be ANY car) so you just have to not worry about it. Get the car that makes you smile the most,regardless of if it's an L98 or LT1. An LT1 has more potential and it has more power out of the gate compared to an L98, but it can still get stomped by a "breathed on" import. Like I said: there's always someone faster.....
An L98 is an honest high 5 second 0-60 mph car, runs the 1/4 mile in the mid 13's and plays with supercars in the 150 mph range. That's not exactly slow, but in comparison to most modern vehicles, it's not fast either. You're buying a 30 year old sports car, you have to enjoy it for what it is and not how fast it is compared to anything else....mostly because it could be stomped to death by nearly any modern engine, whether it's an 8, 6 or 4 cylinder. Hell, a C4 would have a hard time with an Ecoboost 4 cyl mustang these days. If you really want to get into an "unzip and measure" contest, you have to make them fight on your terms and not theirs. That means you have to make the contest short and about acceleration in an L98. An L98 will fire stop light to stop light with just about the best of them. With a little work, they can even embarrass the mighty LS. More than a block or so though and you're going down in a ball of flames. The L98 is good from a dig and as long as it's a short run, it's an impressive sprinter. Give a modern engine enough room to swing though and it's all over any longer than about an 1/8th mile run.
Now, get a good condition C4 into a "fight" that involves cornering and that Civic Si will be not much more than a dot in the rear view mirror.
As in the Art of war: fight on their terms and it's over before you begin......if you are going to fight make them fight your fight, not theirs.
Last edited:
- Thread starter
- #13
i smile all the way reading ur post 6sec 0-60 and a 13.5-14sec 1/4mile its exactly my espectation in term of performance i was think they were slower ...so like as you Say i Will take it like is it and dont be stressfull with a ricer 200hp Civic lol ...so now am way more excited about m'y eventual c4 thank again
No worries.
The few times I've dropped a dime on other cars I've never had a problem. The Vette just annihilates them. Always been while rolling thoughand I don't bother unless I know the odds are stacked in the Vette's favor.
I've had a wicked up diesel Jetta try me when I tried to pass him on a normal passing zone. I got up beside him (this is on a two lane road where he was traveling a good 20 kph under the limit) and then all I saw was a huge black cloud behind us. So he at least have the injection pump whicked up, they don't make destroyer sized clouds unless they have the fuel turned up in some misguided attempt at making more HP. I also heard the engine wind up crazy high and the nose of his car came up. So I knew he was being an ass. I was maybe 1/2 throttle so I just rolled it on and left him for dead. We were both doing about 80 kph when he hit the throttle, but I had the Vette in the meat of it's torque curve and we were at 140 kph before he even knew what happened. Once past him, I dropped back down to 80 (speed limit) and he just dropped way back in my mirror. I think his buddy in the passenger seat was actually laughing at him, but it was hard to tell looking in the mirror.
Then there was an S-197 generation Mustang once. He had lots of goodies on it and it made one hellacious noise sitting at the light with me. He kept blipping the throttle and looking over at me. Well, I had no intention of "racing" hi (or anyone for that matter) and when the light turned he hammered it like a madman. Did he leave me at the light? Sure did, left me for dead. But I didn't even try. You see, he missed one important thing in the whole mess: the RCMP car sitting at a set of lights to enter the way a couple streets up. Sure enough, he blasts past the RCMP car at full battle cry and was treated to fireballs right away. I just rumbled by the two of them on the side of the road, Laughing at the top of my lungs with the top down. The Officer actually gave me a wave and a smile as i drove by and took the guys paperwork from him...
This is the thing Vette's are really good at IMHO: just enjoying life at your own pace.
I couldn't really gives a crap how fast it is when it works sooooo great as squid bait and makes such a great top down cruiser.
My car's RPO codes:
AC1 –Power passenger sport seat
AC3- Power driver sport seat
AQ9- Sport seats ‑ leather
BGR – Bowling Green assembly
B4P - Radiator cooling boost fan
C68 - Automatic electronic air condition
DL8 - Twin remote heated outside mirrors
D3X- Speedometer driven gear 25513049 green
D74 - Illuminated driver vanity mirror
D98 - Speedometer sensor 25007308
E5Z - Delete speedometer adaptor
E9Z - Delete speedometer key
FG3- Preloaded gas shock absorbers
G44 - Rear axle 3.07 ratio
KC4 - Engine oil cooler
K68 - 105 amp generator
L98 - Tuned port injection 5.7 L engine
MD8 - Automatic 4‑speed transmission
MXO - Automatic transmission
NA5 - Federal emission system requirements
QA1 - Styled aluminum wheels, 17 x 9.5"
UQ4 - Delco Bose four speaker system
UU8 - Delco Bose AM/FM stereo radio with cassette
V01 - Heavy duty radiator
V73 - Vehicle statement certification, US or Canada
XAU - Front tire P275/40 ZR17
X05 - Sales processing option 14
YAU - Rear tire P275/40 ZR17
Z31 - Advance price sheet
Z49 - Mandatory Canadian base equipment modifications
Z52 - Sport handling package
19I - Black interior trim
19T- Black convertible top
192 - Black leather interior
I99 - Black safety belts
41U - Black exterior
Some things are not as delivered though. It's got wheels from a 91+ corvette (know as "sawblades"), a saddle colored top (intead of the orginal black) and I've changed out the stereo for this:
Last edited:
I guess I should also say my Vette will boil both rear skins from a standing start (it's got posi) as long for as I keep the throttle on and it pulls down between 25 and 30 mpg on the highway. That's pretty impressive for 275 width tires all around.
Those same 275/40's also make it corner like a rat in sneakers on a rubber gym floor. It's nothing for me to pin the passenger against their door in a LH sweeper until I ease up on the wheel.
Corners that tighten up in the middle aren't even a concern. It just rails through and sharpens up the line with nothing more than a couple finger's pressure on the wheel. This thing is just crazy in the corners! Cornering in the C4 is 10x more fun than the throttle to me, and I used to race motorcycles (amateur). It just rails thorugh corners where lesser cars would be 4 wheel drifting off the edge or snap over-steering into the ditch. I've let a couple freinds drive it and everyone comes back raving about how it handles corners. They also come back raving about how much it rattles......lol!
L98's may be slow for most peoples standards, but it's "personality" drops it right into my wheelhouse.....very happy with it.
Only problem is I just want MORE of it....LOL!
Those same 275/40's also make it corner like a rat in sneakers on a rubber gym floor. It's nothing for me to pin the passenger against their door in a LH sweeper until I ease up on the wheel.
Corners that tighten up in the middle aren't even a concern. It just rails through and sharpens up the line with nothing more than a couple finger's pressure on the wheel. This thing is just crazy in the corners! Cornering in the C4 is 10x more fun than the throttle to me, and I used to race motorcycles (amateur). It just rails thorugh corners where lesser cars would be 4 wheel drifting off the edge or snap over-steering into the ditch. I've let a couple freinds drive it and everyone comes back raving about how it handles corners. They also come back raving about how much it rattles......lol!
L98's may be slow for most peoples standards, but it's "personality" drops it right into my wheelhouse.....very happy with it.
Only problem is I just want MORE of it....LOL!
Last edited:
Well, 3.07's will boil both rear tires at will from a stop and shove you back in the seat hard enough that my passengers can't reach the dash until I either let off or we get up to speed, so they're good enough for me!
YMMV! LOL!
The LT1 intake is in the development stage right now:
That's it sitting in a Jig to get the critical dimensions right when I go at it with a TIG welder. Currently saving up for one. It could have been done much more simply, but it involves compromises that I just didn't want to make. I need an AC pulse Tig capable of around 250 amps for that sucker. That's around 2500 bucks on the low end (for a larger Chinese brand, if you want a Miller or Lincoln it's going to set you back around 5-6 grand). I've got a Lincoln 180 amp MIG with a spool gun, but it just doesn't have enough "punch" to deal with an aluminum casting this thick. Works fine on 1/8" aluminum stock though:
It built the cage for my Argo no problems, but just not enough punch for that cast aluminum. Close, but not quite enough. No big deal really, I've been "jones-ing" for a nice TIG machine for a while now and this gives me an excuse to get one. Between the MIG, TIG, metal lathe and plunge mill, I'll be pretty well set up for my retirement hobbies......
The LT1 intake is good for spinning an L98 up past the TPI intake limitation of about 4500-4800 RPM. You loose the peak torque that TPI creates,but you gain more average torque across the curve. Where the LT1 intake shins is over 5,000 rpm, where is where you start seeing higher HP numbers. It's my understanding that the LT1 intake will flow enough CFM to support somewhere around 400-500 HP, but you ned to do a lot of other work to an L98 to get it there. Heads, cams, etc....
This year, I believe I will be reworking the TPI to see what I can get out of it. I've picked up a used TPI lower intake to weld and port:
It would have been easier to start wit han edlebraock or accell TPI "big mouth" base, but they're hard to come by and if you do, people want stupid money for them. My stock 113 heads only flow around 240-260 CFM, so with some welding and raising the runner roofs, I should be able to get close to that. Ideally, you want your intake to flow more than your heads, but it's difficult with the TPI Long Tube Runner (LTR) design. The long tubes are what "tune" the intake pulses and are also what becomes the restriction (and flat tops the HP curve) around 4500-4800 RPM.
Here you can see a rubber casting someone made of a stock lower and a ported lower:
left to right; Stock, cleaned up and gasket matched, welded and port roof raised.
You need to weld to the intake and raise the roof at the head becuase o fthe way it turns into the head port/runner:
The rubber mold is taken from the 113 head runner, the tpi lower intake is what you see on the bench. The rod closest to the camera is the stock TPI runner roof angle, the sceond rod is the welded and ported runner roof. You can see how the stock runner essentially chucks the airflow into a wall, the ported one makes a "gentler" turn into the head port. This is important because any time you try to force air to turn more than approx 45 degrees, you get separation and turbulence, which kills flow and power.
The runner tubes also need to be enlarged, but hte problem is they are VERY thin walled and can't be made any bigger. You need to either buy an aftermarket set (most are out of production now) or make your own. I'm going to make my own.
I'm also going to "remake" the upper plenum to hold more volume. Generally, you want the plenum in an intake to be about the same size as the engine displacement and the OEM TPI upper plenum is about half the size of the 350 cu/in engine. I'm also going to take the opportunity to reduce the runner length a bit. Something like so:
You can also see the welding that is required to change the port roof. That's on an Edlebrock lower intake as well. It already has extra "meat" (compared to the OEM piece) that could be ported out and they still had to add material to the runner. They even had to add "bungs" for the injectors in order to raise them up out of the port area. It's all work I can do myself (once I get my TIG), it's just going to take a long time to get it done. Counting welding, reworking and porting, that guy easily had 100+ hrs of work into his intake.
That guy made max torque of 421 at 5000 rpm and max Hp of 413 at approx 6200 rpm. But it made pretty much that HP number at 5000 RPM, dropped a little bit at approx 6000 rpm and charged back up to 421 just after that, then started to fall on it's face after 6500 rpm. Here's the chart he posted:
That's dead serious territory....for an L98/TPI engine that is. And that's not an engine Dyno, that's RWHP! Figure another 15-20 percent for crank HP numbers. He had more work into his engine that just the intake though. AFR heads, cam, exhaust, ECM tuning, etc....
Changing around the runner length moves the hp and tq peak up a bit, but it also means it increases the RPM capability of the TPI. I'm not looking for much, maybe another 500-700 RPM to 5500-ish before the HP curve "flat tops". I've got some math to do though before I settle on how long they should be. I have to get the 1st, 2nd, 3rd and 4th harmonics right to get the power peaks where I want it and the proper RPM ranges where I use the car.
I'd like to say it is all my idea, but as you can see from the pictures above, I'm not the first. I'm just following someone else's patternand putting my own "twists" where needed.....
Last edited: