New domain: www.Speed-Talk.com

The forum is currently running on the new domain and server. The old domain will remain active for a short while to forward any (less frequent) visitors.
IMPORTANT: Update your bookmarks to https://www.speed-talk.com/forum/

1991 c4 corvette L98 engine questions, options, mass confusion.

General engine tech -- Drag Racing to Circle Track

Moderator: Team

SpeierRacingHeads
Vendor
Posts: 184
Joined: Sun May 13, 2012 1:28 pm

Re: 1991 c4 corvette L98 engine questions, options, mass confusion.

Post by SpeierRacingHeads » Mon Sep 02, 2019 4:14 pm

BOOT wrote:
Mon Sep 02, 2019 4:11 pm
SpeierRacingHeads wrote:
Mon Sep 02, 2019 11:33 am
The OEM TPI is great for a street rod. It has a timeless classic look, and some might say ahead of it's time. However performance wise it's a disaster, IMO. The bottom isn't even big enough to match the factory head, and you can't port it big enough without weld.
A bit harsh, the problem is most don't build to it's strengths and try to make it do what it won't. Still most the time I try n caution anyone not to go too big on a combo piece they just go bigger! People always think my C4 is a LT1 car cause I beat basic moded LS cars and it's fun to pop the hood n show them the TPI.
Where does your engine peak with the OEM TPI? 46-4800?
Speier Racing Heads
Chad Speier
785-623-0963

User avatar
BOOT
Guru
Guru
Posts: 1641
Joined: Fri Apr 09, 2010 6:23 pm

Re: 1991 c4 corvette L98 engine questions, options, mass confusion.

Post by BOOT » Mon Sep 02, 2019 4:34 pm

SpeierRacingHeads wrote:
Mon Sep 02, 2019 4:14 pm
Where does your engine peak with the OEM TPI? 46-4800?
I already told the guy to get another intake and the TPI was a money pit AND I think it's good for a mild street car, the guy wants more than mild so....
I'll even go one further, my car would prob be a lil faster with a different/better intake but not by much for how I have it set up.


Oh and to the OP, I forgot to suggest a carb intake and fitech or sim TB, still tight fit, so I'd used shorter type dual plane like maybe a brodix but not like you got air bleeds to worry bout.
Channel about my projects https://www.youtube.com/user/BOOT350V

I know as much as I can learn and try to keep an open mind to anything!

If I didn't overthink stuff I wouldn't be on speedtalk!

F-BIRD'88
Guru
Guru
Posts: 7179
Joined: Tue Mar 27, 2007 6:56 pm

Re: 1991 c4 corvette L98 engine questions, options, mass confusion.

Post by F-BIRD'88 » Mon Sep 02, 2019 7:02 pm

There was a company that sold modified gen II LT-1 efi intakes modified to fit and run on a gen I block/heads.
A lot more power, like a mini ram.

More cr + 219° 219° .560" hyd roller + headers + fully port+ 2.00/1.56 your 113 heads. 10.5:1 cr

You may be able to find this modded LT-1 intake used or a used mini ram.
A shortened stealth ram/weiand hi ram base with custom low height plenum top will work well too.
A shortened Edelbrock tunnel ram base with custom fabed plenum top is another path.
Must add injector bosses.

Orr89rocz
HotPass
HotPass
Posts: 1834
Joined: Sun Sep 28, 2008 9:25 pm

Re: 1991 c4 corvette L98 engine questions, options, mass confusion.

Post by Orr89rocz » Mon Sep 02, 2019 7:17 pm

BOOT wrote:
Mon Sep 02, 2019 4:34 pm
SpeierRacingHeads wrote:
Mon Sep 02, 2019 4:14 pm
Where does your engine peak with the OEM TPI? 46-4800?
I already told the guy to get another intake and the TPI was a money pit AND I think it's good for a mild street car, the guy wants more than mild so....
I'll even go one further, my car would prob be a lil faster with a different/better intake but not by much for how I have it set up.


Oh and to the OP, I forgot to suggest a carb intake and fitech or sim TB, still tight fit, so I'd used shorter type dual plane like maybe a brodix but not like you got air bleeds to worry bout.
The big tube ported aftermarket base tpi stuff will make his power. It will peak 4400-4600 and hold to 4800-5000 but its been done many times. Welding the base up and raising injectors up to gain cross sectional area is the only way to really get more out of them systems

F-BIRD'88
Guru
Guru
Posts: 7179
Joined: Tue Mar 27, 2007 6:56 pm

Re: 1991 c4 corvette L98 engine questions, options, mass confusion.

Post by F-BIRD'88 » Mon Sep 02, 2019 7:27 pm

Putting a aftermarket hood on the C4 Vette really opens up the possibilities.

User avatar
BOOT
Guru
Guru
Posts: 1641
Joined: Fri Apr 09, 2010 6:23 pm

Re: 1991 c4 corvette L98 engine questions, options, mass confusion.

Post by BOOT » Mon Sep 02, 2019 10:25 pm

Orr89rocz wrote:
Mon Sep 02, 2019 7:17 pm
The big tube ported aftermarket base tpi stuff will make his power. It will peak 4400-4600 and hold to 4800-5000 but its been done many times. Welding the base up and raising injectors up to gain cross sectional area is the only way to really get more out of them systems
People act like it peaks and drops like a rock! More like a very slight peak and then it flatlines and that makes the ave power still decent, if your ignition and valvetrain are good.

I still think longterm higher hp goals and how people buy parts that support narrow high rpm a better intake is a safe bet.
Channel about my projects https://www.youtube.com/user/BOOT350V

I know as much as I can learn and try to keep an open mind to anything!

If I didn't overthink stuff I wouldn't be on speedtalk!

SpeierRacingHeads
Vendor
Posts: 184
Joined: Sun May 13, 2012 1:28 pm

Re: 1991 c4 corvette L98 engine questions, options, mass confusion.

Post by SpeierRacingHeads » Mon Sep 02, 2019 11:12 pm

BOOT wrote:
Mon Sep 02, 2019 10:25 pm
Orr89rocz wrote:
Mon Sep 02, 2019 7:17 pm
The big tube ported aftermarket base tpi stuff will make his power. It will peak 4400-4600 and hold to 4800-5000 but its been done many times. Welding the base up and raising injectors up to gain cross sectional area is the only way to really get more out of them systems
People act like it peaks and drops like a rock! More like a very slight peak and then it flatlines and that makes the ave power still decent, if your ignition and valvetrain are good.

I still think longterm higher hp goals and how people buy parts that support narrow high rpm a better intake is a safe bet.
I don't think it drops like a rock. I also have a '85 IROC with a 215hp 305. To be honest it runs damn good. I think they get a bad rap myself.

Image
Speier Racing Heads
Chad Speier
785-623-0963

Bill Chase
New Member
New Member
Posts: 8
Joined: Tue Aug 27, 2019 1:11 pm

Re: 1991 c4 corvette L98 engine questions, options, mass confusion.

Post by Bill Chase » Tue Sep 03, 2019 5:40 am

Want the sale? I need a guaranteed to work and play nice together package I can bolt on in a weekend, then throw on trailer and take to dyno to be tuned, unless of course there is a package with custom parameters chip you sell..?? You come highly recommended sir.

Edit* thought I was quoting Chris Spier sorry guys. I like the heads cam intake approach, then I can have a 383 built for when he kills this thing in a year or two of flogging it.

Orr89rocz
HotPass
HotPass
Posts: 1834
Joined: Sun Sep 28, 2008 9:25 pm

Re: 1991 c4 corvette L98 engine questions, options, mass confusion.

Post by Orr89rocz » Tue Sep 03, 2019 7:13 am

BOOT wrote:
Mon Sep 02, 2019 10:25 pm
Orr89rocz wrote:
Mon Sep 02, 2019 7:17 pm
The big tube ported aftermarket base tpi stuff will make his power. It will peak 4400-4600 and hold to 4800-5000 but its been done many times. Welding the base up and raising injectors up to gain cross sectional area is the only way to really get more out of them systems
People act like it peaks and drops like a rock! More like a very slight peak and then it flatlines and that makes the ave power still decent, if your ignition and valvetrain are good.

I still think longterm higher hp goals and how people buy parts that support narrow high rpm a better intake is a safe bet.
Yeah it can certainly make average
Heres the one tpi hot cam car i tuned.
You do not have the required permissions to view the files attached to this post.

Bill Chase
New Member
New Member
Posts: 8
Joined: Tue Aug 27, 2019 1:11 pm

Re: 1991 c4 corvette L98 engine questions, options, mass confusion.

Post by Bill Chase » Tue Sep 03, 2019 10:02 am

Orr89rocz wrote:
Tue Sep 03, 2019 7:13 am
BOOT wrote:
Mon Sep 02, 2019 10:25 pm
Orr89rocz wrote:
Mon Sep 02, 2019 7:17 pm
The big tube ported aftermarket base tpi stuff will make his power. It will peak 4400-4600 and hold to 4800-5000 but its been done many times. Welding the base up and raising injectors up to gain cross sectional area is the only way to really get more out of them systems
People act like it peaks and drops like a rock! More like a very slight peak and then it flatlines and that makes the ave power still decent, if your ignition and valvetrain are good.

I still think longterm higher hp goals and how people buy parts that support narrow high rpm a better intake is a safe bet.
Yeah it can certainly make average
Heres the one tpi hot cam car i tuned.
What all did the combo consist of?

Orr89rocz
HotPass
HotPass
Posts: 1834
Joined: Sun Sep 28, 2008 9:25 pm

Re: 1991 c4 corvette L98 engine questions, options, mass confusion.

Post by Orr89rocz » Tue Sep 03, 2019 10:52 am

Stock shortblock 87 L98 350

Box stock afr 180 heads
Tpis bigmouth base basically box stock no porting, already was 1205 ish gasket like the heads
AZ speed and marine large runners
Matched plenum to runners
Lunati lt4 hotcam clone 219/228 .525”
52mm throttle
27 lb injectors
2800-ish stall 700r4 trans
1 3/4 shorty headers, single 3” magnaflow which was quiet and probably restricted some

I was expecting 300 whp pretty easily so was abit disappointed. But motor did have bad blowby not sure why

Doing that over again i would have gone slightly more lift on cam in a more aggressive lobe, maybe tighter lsa and maybe afr 195 heads

dfarr67
Pro
Pro
Posts: 381
Joined: Sat Jul 27, 2013 7:14 pm

Re: 1991 c4 corvette L98 engine questions, options, mass confusion.

Post by dfarr67 » Tue Sep 03, 2019 11:03 am

If he went vortec....GM Ramjet, GM marine vortec intakes. FIRST TPI, Weiand Stealth.

F-BIRD'88
Guru
Guru
Posts: 7179
Joined: Tue Mar 27, 2007 6:56 pm

Re: 1991 c4 corvette L98 engine questions, options, mass confusion.

Post by F-BIRD'88 » Tue Sep 03, 2019 11:50 am

Test the existing motor as is first to see if it really is healthy. 1/4 mile mph. Power/weight ratio. Or dyno it.

Eg:3600 lbs. 245 net hp should run 95-96 mph.

If you are going to change the tpi base and runners
ditch it for a better manifold design.

NewbVetteGuy
Pro
Pro
Posts: 420
Joined: Sun Aug 07, 2016 4:11 pm

Re: 1991 c4 corvette L98 engine questions, options, mass confusion.

Post by NewbVetteGuy » Fri Sep 06, 2019 12:15 am

This guy is selling a ceramic thermal barrier coated, black crinkle painted brand new FIRST FUEL INJECTION intake and vortec heads for $1,200 asking price out by me...



Adam

rfoll
Guru
Guru
Posts: 2374
Joined: Mon Jan 11, 2010 12:44 pm

Re: 1991 c4 corvette L98 engine questions, options, mass confusion.

Post by rfoll » Sun Sep 08, 2019 12:02 pm

I didn't see anything in the discussion about exhaust. Stock manifolds might make the goal hard to reach.
So much to do, so little time...

Post Reply