90 L98 convert to LT4?
Thread Starter
Heel & Toe
Joined: Aug 2006
Posts: 24
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90 L98 convert to LT4?
Hi
I have a 1990 L98 6-speed with Side Effects (sport version) exhaust installed. Also have a set of new Hedman long-tube ceramic headers to install. I hope to improve performance up to an LT4 level. I understand it is possible to upgrade the heads and intake using LT1 heads, intake and other parts, but is there any reason why I cannot simply install a good used LT1, or better yet an LT4? I have been told that this is complicated, but can't understand why. Wiring problems ?
Upgrading with aftermarket parts is OK too, but I would like to keep the idle sounding like factory as it is for street use and little if any track time.
I would expect to spend several thousand $, hopefully under $5K.
Any advice would be appreciated.
Thanks, Lee
)
I have a 1990 L98 6-speed with Side Effects (sport version) exhaust installed. Also have a set of new Hedman long-tube ceramic headers to install. I hope to improve performance up to an LT4 level. I understand it is possible to upgrade the heads and intake using LT1 heads, intake and other parts, but is there any reason why I cannot simply install a good used LT1, or better yet an LT4? I have been told that this is complicated, but can't understand why. Wiring problems ?
Upgrading with aftermarket parts is OK too, but I would like to keep the idle sounding like factory as it is for street use and little if any track time.
I would expect to spend several thousand $, hopefully under $5K.
Any advice would be appreciated.
Thanks, Lee
)
Le Mans Master
Joined: Feb 2005
Posts: 5,146
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From: The Motor City
Since you have a reasonable budget to work with there is no reason why you can't take what you have, and make just as much or more power than the LT-4. It will be more simplified than worrying about cooling system, etc. If I were to do any motor swap along those lines I would want to use an LS motor.
Racer
Joined: Sep 2006
Posts: 446
Likes: 1
From: Punta Gorda Florida
Correct me if I'm wrong, but I believe the LT1 is a redesigned block, heads, and intake, Generation 2 sbc (1992-93 to 1996?). And the LS1's were the start of the generation 3 sbc's (97? to present).
Just look at the head gaskets HUGE differences, between the three heads.
Just look at the head gaskets HUGE differences, between the three heads.
Le Mans Master
Joined: Feb 1999
Posts: 9,938
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From: South Carolina
St. Jude Donor '03 & '05
Just do AFR's new heads, Cam and a Mini Ram and Long tubes and new throttle body. Then you will be beyond LT4 performance, cheaper too, and have reliability of a good ditributor.
Race Director
Joined: Dec 2002
Posts: 13,348
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From: SCMR Rat Pack'r Charter Member..Great Bend KS
Originally Posted by Sparkpluglee
I have a 1990 L98 6-speed ..I hope to improve performance up to an LT4 level.
Any advice would be appreciated.
Any advice would be appreciated.
Larry
code5coupe
Instructor
Joined: Dec 2004
Posts: 168
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From: Charlottesville VA
Or of course you could always sell your current ride, add the 5000.00 to the proceeds from that and buy a beefed up LT1/LT4 car, ready to go. Sure, with those cars they have the Optispark that some people will tell you is a demon or witchcraft under your hood, but you get the nicely upgraded interior and newer styling on the exterior, for those who prefer that.
If not, or you are sentimentally attached to much to let go, then building your current motor as everyone has recommended is definitely the best route.
If not, or you are sentimentally attached to much to let go, then building your current motor as everyone has recommended is definitely the best route.
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Racer
Joined: Apr 2006
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From: New York NY
Originally Posted by rocco16
There are proven ways to get 350hp out of a L98. Careful planning and your $5K budget could get you there. Larry
code5coupe
code5coupe
Le Mans Master
Joined: May 2000
Posts: 7,033
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Originally Posted by mseven
Since you have a reasonable budget to work with there is no reason why you can't take what you have, and make just as much or more power than the LT-4. It will be more simplified than worrying about cooling system, etc. If I were to do any motor swap along those lines I would want to use an LS motor.
Originally Posted by cuisinartvette
Id just do a head/cam/intake combo on yours, you can go fast and stay on budget.
You can sure make 290 rwhp a helluva lot easier with a L98 than swapping a LT4 in it.
You do realize the L98 is THE fabled TORQUE MONSTER. Roar
I included a pic of my 44.3 mph torque monster.
Go easy on me, my feeling() gets hurt easy. Yea my only feeling.
I am .7 mph short of my damn goal of 45mph when I bought it. So far I am up around 11 mph with a pipe and a 19/32" drill bit thru the carb and a few other tricks. Maybe a 50* day could increase the 3 hp to 3.4 hp to allow me to achieve my summer goal. Or a nutrisystems diet of their crap food might help too.
Mick, did you ever dyno your setup???
Le Mans Master
Joined: May 2000
Posts: 7,033
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Originally Posted by cuisinartvette
Hippy, shes a real beaut, wutz ur rwhpz? Traps.
My modz r, pipe, carb, intake, no head gasket, sprocket, and jet.
Haven't made er to the dyno/strip to get the dyno/trap #'s yet but top speed has increased around 10. This mother fo moves like there is no tomorrow.
I could probably give crapvette a good race with it.
Le Mans Master
Joined: Feb 2005
Posts: 5,146
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From: The Motor City
Originally Posted by hippy
Mick, did you ever dyno your setup???
My biggest thing of late has been fiddling with closed loop tune......mileage is looking good, but I really need to get some track time to dial it in the rest of the way, testing in my backyard isn't like taking it from a dead stop and winding it up.
BTW, nice puch, is gas that high over there
...and here I thought the mo-ped/euro/wats ur mods was dead
Last edited by mseven; Sep 6, 2006 at 11:49 PM.
Le Mans Master
Joined: May 2000
Posts: 7,033
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Originally Posted by mseven
BTW, nice puch, is gas that high over there ...and here I thought the mo-ped/euro/wats ur mods was dead
...and here I thought the mo-ped/euro/wats ur mods was deadNo, gas isn't that high but I just kinda laugh holding the damn thing to the wood and listening to it scream.
Now it's kinda a pissin contest between me and the ped trying to get it to the speed I set out to make it go.
I dare say I am having more fun trying to get 2 mph out of it than I am this summer with the vette.
Who fkin cares, they're all gas engines. 
I might, might, put a true dual on it to see if I can hit 360rwhp with the car yet this summer, I doubt it will see the strip though.
Le Mans Master
Joined: Feb 2005
Posts: 5,146
Likes: 3
From: The Motor City
Originally Posted by hippy
Now it's kinda a pissin contest between me and the ped trying to get it to the speed I set out to make it go.
That would drive me even more crazy than I am already.
Le Mans Master
Joined: May 2000
Posts: 7,033
Likes: 12
Originally Posted by hippy
Notice the luggage rack too. About half way back you can see it bending towards the fender. I guess it doesn't like me sitting on it attempting to be more aerodynamic, it is good for around .5 mph on the GPS though.