I'm new to the import performance world, however I'm old to "hot rodding". I was wondering, if any one has tried to port and polish or extrude hone a intake manifold for a 1st generation LS400? If so, what were your results?

 

Well, at some point an extrude hone would probably help but the stock intake manifold is not the weakest link performance wise. Tuned runner length manifolds are designed for max torque in the main power range of the engine and/or off line torque on small displacement engines. The 3rd generation manifold may bolt up and could be a good upgrade but would require relocating the mass air meter and air box. Also, the air box assembly would probably be the first place to start. There is a good site from Australia from a guy that posts in the SC300/400 section. He tested several aftermarket air inlet mods and ended up with making his own for cheap and getting great results. I have the web address at my office computer and will try to post it here.

 

Thanx for the info JBrady. Would you happen to know, exactly how much power can one gain by replacing the 1st gen. intake manifold with a 3rd gen. intake manifold?
I was also wondreing, if any one has any insight on the exhaust manifolds "Headers" sold by (TDI)?
Can any one please post the the Bore and stroke specs for the
4 litre and 4.3 litre engines? I was wondering if the 4 litre is an under, over or dead square engine. If at all possible, can anyone furnish the various horsepower and torque specs. for the 4 litre?
Thanx

 

I have all the specs on my other computer so I will try to remember to get them posted.

Basically, the 1st gens (91-94) had 250hp/260tq, the 95-97s had 260hp/270 tq, the 98-01s had 290hp/300tq. All shared the same bore/stroke.

Without other mods I doubt you would gain any significant power with the 3rd gen intake on a 1st gen engine as it is not the restriction. Fully modified with exhaust, compression, head work, cam work, intake system the 4.0 could probably make 330hp or so while retaining a resonable idle quality. The 98s up could go higher with the variable valve timing. All of this is speculation as the actual output has MANY variables.

 

1st gen specs: 1991-1994 LS400
250hp @ 5600rpm
260tq @ 4400rpm
4.0 liter = 3995cc
Bore x stroke = 3.43" x 3.31" (suspect data from carpoint)
10.3 to 1 compression ratio

2nd gen specs:
260hp @ 5300rpm
270tq @ 4500rpm
4.0 liter = 3969cc
Bore x stroke = 3.44" x 3.25" (87.5mm x 82.5mm)
10.4 to 1 compression ratio

3rd gen specs: 1998-2000 LS400 (variable valve timing w/intelligence) VVTi
4.0 liter = 3969cc
Bore x stroke = 3.44" x 3.25" (87.5mm x 82.5mm)
10.5 to 1 compression ratio
290hp @ 6000rpm
300tq @ 4000rpm

4th gen specs: 2001 LS430
4.3 liter = 4293cc
bore x stroke = 3.58" x 3.25" (91.0mm x 82.5mm)
10.5 to 1 CR
290hp @ 5600rpm
320tq @ 3400rpm