hello guys, i dont post much, i mostly read. i build small block chevy powered Porsches and have recently built a kit to do a LS-1 in a 944 (bitchin') now working on the 911 and 914 and had a thought. i dont know the truck stuff well enough to know this answer. when did the trucks have the top throttle body on them and when did they go to the LS-1 style throttle bodies on the front of the intake? were the top TB intakes ever on the 6/0 liter style motor or were those only the older motors? a little (lot) of help here is greatly appreciated.

Mike
Renegade Hybrids
www.renegadehybrids.com

 

The GenIII (LS1 based) motors were introduced into the trucks in 1999. (Although, in 1999, the 6.0L had irons heads. Later years are equipped with aluminum ones.)

Hope that helps somewhat.

 

ok, that is a great help, what about intakes and intake designs? top fed versus front fed?

 

You would never want a TBI (the one on top) swap into a performance car. They just suck. They don't flow well and the tuning system (the computer and software) is too simple and limited to support anything fun. Basically, once you start dipping below about 17 inches of vacuum at idle they get harder to tune because the tuning tables don't offer enough range. If you hit 12 inches of vacuum at idle you're screwed for tuning. You basically have to stick with a compucam type camshaft if you want it to work well.

Cory

 

This happened with the GEN III motors

 

My 96 vortec 350 (old style v8) had a top mount TB, and was much better than a TBI, but very inferior to our current injection setup, and will not work. How much clearance do you have on the top, and what kind of budget are you working with? If money is no concern you can buy the intakes to convert a LS1 to carb, and I think you can get them with injector bungs already welded in. I am also sure that someone(I think accell, but don't hold me to that) makes a 1250 cfm throttle body that will mount to the top of that intake in place of a carb. Then you would have a top mount fuel injected badass LS1.

 

you guys are awesome, i know the TBI sucks bad, i own one of those, a 7.6 liter (yes larger than 7.4l) dually. the main question here is did they ever run the top load throttle body vortec on a gen 111 motor? on these cars hood clearance isnt really the issue its room in front and back of the motor, this is something we do in "kit" form, so many reproductions of it. what i am looking at doing is a throttle body relocation and do a 90 degree bend off of the intake manifold and then the throttle body over the end of the valve cover. this will give me unwanted torque, ( i know that sound crazy) but these cars are only 2200 pounds and the trannys cant take a ton of torque. but this or the top load throttle body is my only real choice. unless i want to recast an intake which is a possibility. anyway you guys are a great help, hope i can help with something for you in the future.

Mike Johnson
Renegade Hybrids

 

No, they did not ever have a intake with the TB on top that will work on the LS1 based engines. That is the reason that I told you about that setup. At this moment, there are 2 manufactures that make those intakes, GMPP, and edelbrock, both of which perform similar. I think that route would be more simple (and cheaper) than casting your own intake.

 

There are several GEN III carb intakes out right now...I think Edelbrock makes one. Sounds to me like that would cure your problem.

Any pics of the LS1 Porsches?