one mean tuned port mod
Thread Starter
Drifting
Joined: Nov 2000
Posts: 1,722
Likes: 0
From: Big D Tx
Cruise-In II Veteran
one mean tuned port mod
i just got done with a mod on my tuned port that simply amazed me. i took the stock intake manifold off of the car, and with a die grinder, i siamesed the intake manifold where the two seperated circle intakes are, i ground out the middle wall about 3 1/2 inches deep into the manifold. then i matched the gasket to the pattern of the opening. i also did this to the stock runners but only about 3/4 of an inch deep. what this does, is each intake port on the manifold each now gets two runners to suck air through, instead of one. the car now pulls hard all the way up to 5400-5500rpm. the car doesnt seem like it is choked up. throttle response is extremely crisp. i also gasket matched/smoothed the heads and the rest of the intake to. i highly recommend doing this.
Thread Starter
Drifting
Joined: Nov 2000
Posts: 1,722
Likes: 0
From: Big D Tx
Cruise-In II Veteran
Re: one mean tuned port mod (88L98)
btw, i also put a quarter in my stock fuel pressure regulator, to go with the higher air flow now. pressure is around 43-48psi now. these are some pictures of what im talking about. these arent my intake, its where it got the idea from.
[Modified by 88L98, 2:33 PM 9/18/2001]
[Modified by 88L98, 2:33 PM 9/18/2001]
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: one mean tuned port mod (88L98)
Hmm, ingeious and interesting concept; now track/dyno numbers are needed. It makes sense that she can breath better up top, but did you give up anything on the low end from loss of tuning?
BTW, you can build a "free" AFPR by drilling out your FPR cover, welding on a nut and using a matching screw to move that quarter. You might have to tap the inside of the cover to flatten it a little.
BTW, you can build a "free" AFPR by drilling out your FPR cover, welding on a nut and using a matching screw to move that quarter. You might have to tap the inside of the cover to flatten it a little.
Thread Starter
Drifting
Joined: Nov 2000
Posts: 1,722
Likes: 0
From: Big D Tx
Cruise-In II Veteran
Re: one mean tuned port mod (65Z01)
ill have track times as soon as i get back to the track. and no, actually i didnt loose any bottom end, just the opposite actually. it seems to pull harder. alot more rev happy. thanks for the idea about the fuel pressure regulator, i hadnt even thought about that. ill just tack a nylon lock nut on there.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: one mean tuned port mod (88L98)
I'm looking forward to your track test results. This could be something cost effective to try when I'm ready to do an aftermarket base & runners.
BTW, if you can get weather conditions the normalization equations are on my site. That way you have a valid comparison between time slips obtained under varying conditions. I picked up a $99 weather station from Summit for this purpose.
Good luck.
[Modified by 65Z01, 3:13 PM 9/18/2001]
BTW, if you can get weather conditions the normalization equations are on my site. That way you have a valid comparison between time slips obtained under varying conditions. I picked up a $99 weather station from Summit for this purpose.
Good luck.
[Modified by 65Z01, 3:13 PM 9/18/2001]
Thread Starter
Drifting
Joined: Nov 2000
Posts: 1,722
Likes: 0
From: Big D Tx
Cruise-In II Veteran
Re: one mean tuned port mod (65Z01)
i was reading on thirdgen.org's TPI board, that a guy dynoed his car after doing this and he gained like 30+40hp and the stock dyno died at 4800rpm and the new one was still climbing at at point but he had to quit because they heard a rocker come loose and start making lots of noise. but the before and after dyno was very appealing. power gains were very noticeable. as it is with the butt dyno too. it feels to pull way harder.
Le Mans Master
Joined: Jul 2001
Posts: 8,183
Likes: 3
From: Santa Maria, CA
Re: one mean tuned port mod (88L98)
I too came across this in the thirdgen site. Credit to "madmax"! I am actually doing this as we speak. Removing the walls in the lower intake just about makes it un-necessary to port the upper or the runners. Can't wait to get her back together. Way to go 88L98!
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Race Director
Joined: Oct 2000
Posts: 16,477
Likes: 1
From: Enter Post Count Here
Re: one mean tuned port mod (88L98)
Oh sure, after I've put my intake manifold on so tight it will never leak again, you tell us this. :p:
Great mod, my only worry would be water ports(I have no clue where they are located), but in that location you shouldn't have a problem.
In 60K miles or when I suspect that my RTV seal is worn out and needs to be replaced(it won't be leaking, its never going to leak again), I'll probably do this. It makes sense and looks like a great power adder.
Great mod, my only worry would be water ports(I have no clue where they are located), but in that location you shouldn't have a problem.
In 60K miles or when I suspect that my RTV seal is worn out and needs to be replaced(it won't be leaking, its never going to leak again), I'll probably do this. It makes sense and looks like a great power adder.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: one mean tuned port mod (88L98)
Well if it realy pushes the torque curve out, I'm glad I lightened up my valve train when I installed new springs. That might mean shifting at 6k RPM instead of 5,400 RPM as I now should be.
Time for a trip back to thirdgen.org/.
And here's a link to some more pics on this topic. http://www.geocities.com/softtailduece01/
[Modified by 65Z01, 9:38 PM 9/18/2001]
Time for a trip back to thirdgen.org/.
And here's a link to some more pics on this topic. http://www.geocities.com/softtailduece01/
[Modified by 65Z01, 9:38 PM 9/18/2001]
Thread Starter
Drifting
Joined: Nov 2000
Posts: 1,722
Likes: 0
From: Big D Tx
Cruise-In II Veteran
Re: one mean tuned port mod
http://www.thirdgen.org/messgboard/F...ML/001492.html
there is two dyno sheets on there with alot more pictures explaining how to do this.
there is two dyno sheets on there with alot more pictures explaining how to do this.
Race Director
Joined: Aug 2000
Posts: 14,130
Likes: 7
Cruise-In II Veteran
Re: one mean tuned port mod (65Z01)
Ive seen this mod on the 3rdGen site as well...I have bought another L98 intake manifold to do this mod so i dont screw up my stock one...cant take chances if i slip when cutting.. 
I think the idea is good...it seems to trick the engine into thinking it has shorter runners...I was cutting the SLP runners down inside as well almost to the bottom as a full siamese and combined with an siamesed intake manifold, the runner length can be knocked down a nice size.
I dont see losing too much torque...I think it will have a similiar tunnel ram effect and be able to feed the engine to 5k or higher and is still far cheaper then buying a miniram or a SR.
I also thought the person said they siamesed the intake 5 inches down..is that what they did?Or maybe im thinking of another person who did the same mod.
Either way Its a plan i will do and see how it runs..I have 3.73 gears and a mild cam and this may help the 3.73 gears work better now with the engine....hoping!!
I think the idea is good...it seems to trick the engine into thinking it has shorter runners...I was cutting the SLP runners down inside as well almost to the bottom as a full siamese and combined with an siamesed intake manifold, the runner length can be knocked down a nice size.
I dont see losing too much torque...I think it will have a similiar tunnel ram effect and be able to feed the engine to 5k or higher and is still far cheaper then buying a miniram or a SR.
I also thought the person said they siamesed the intake 5 inches down..is that what they did?Or maybe im thinking of another person who did the same mod.
Either way Its a plan i will do and see how it runs..I have 3.73 gears and a mild cam and this may help the 3.73 gears work better now with the engine....hoping!!
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
Re: one mean tuned port mod (65Z01)
This is a very intrigueing modification. I have been following this over on the 3rd gen board as well. Notice his before and after torque curves, however, they are not typical of the peaky L-98 torque curve. I would love to see someone post before and after curves with an L-98 closer to stock trim.
Thread Starter
Drifting
Joined: Nov 2000
Posts: 1,722
Likes: 0
From: Big D Tx
Cruise-In II Veteran
Re: one mean tuned port mod
i dont have a pre-mod dyno, but if someone knows a place in dallas texas i can get my car dynoed at i will do it. i bet the hp curve peaks at 5300-5400. id like to see the torque curve too.
[Modified by 88L98, 8:14 AM 9/19/2001]
[Modified by 88L98, 8:14 AM 9/19/2001]
Thread Starter
Drifting
Joined: Nov 2000
Posts: 1,722
Likes: 0
From: Big D Tx
Cruise-In II Veteran
Re: one mean tuned port mod (Bill's86Coupe)
yeah bills86coupe, thats what im gonna do now. buy the slp runners and knock down more of the wall to make the runner as short as possible. im also gonna siamese the holes in the plenum to the hourglass shape like the top of the siamesed runners. when i do that, im gonna do my manifold some more and go deeper. then im gonna buy some 4.10s. then i bet i can run 12s with a good converter.
Le Mans Master
Joined: Mar 1999
Posts: 9,663
Likes: 1,680
From: Fort Worth Texas
2024 Corvette of the Year Finalist - Unmodified
2023 C8 of the Year Winner - Unmodified
2020 Corvette of the Year Finalist (stock)
2019 C7 of Year Winner (stock)
Former Moderator
Cruise-In I-II-III Veteran
Re: one mean tuned port mod (88L98)
there's a couple of places to dyno... speedworks (speedwerks?) in Lewisville, some other place in Garland.... I'm not up on them but the local clubs will be. I think LG Motorsports is having a dyno day on October 20th. $50 for three pulls. Lou Gigliotti will be there and have some race cars out I think.
Le Mans Master
Joined: Apr 2000
Posts: 5,589
Likes: 0
From: DrunkDefender
CI 1-2-3-4-5-6-7-8 Veteran
CI-IV AutoX Champ
CI-IV Burnout Champ
St. Jude Donor '07-'10
Re: one mean tuned port mod (Marcho Polo)
I dont want to rain on anyones parade but I've also seen where some guys who did this mod had some trouble with getting some cylinders too lean and others too rich because of this mod. Dont know of any firsthand accounts of this though. I've just read some posts about it over on camaroz28.com. One guy said he burned a piston up because of it. Just something to consider. Sounds like a worthwhile mod though.