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Discussion Starter #1
Hey,I've got a 05 3.5 G6 Gt.I wanna change the exhaust manifolds,cats & the flex pipe.For a little more power. But what I'm trying to find out is will a 3.9 exhaust manifold bolt up to a 3.5? Help please?!
 

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waste of time, the 3.5 and 3.9 exhast manifolds cats etc are the exact same because the 3.5 and 3.9 are the same engine block as far as the LZ4 and LZ9 goes, the 3.5/3.9 stuff wont fit the LX9 3.5 tho
 

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Discussion Starter #3
waste of time, the 3.5 and 3.9 exhast manifolds cats etc are the exact same because the 3.5 and 3.9 are the same engine block as far as the LZ4 and LZ9 goes, the 3.5/3.9 stuff wont fit the LX9 3.5 tho
So they will bolt up but it'd be a waste of time? Well if its a waste of time then what are my options on headers?
 

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itd be a wast of time because you already have those "3.9 parts" on your engine from the factory, and no such thing as headers for the LZ4/LZ9 because nobody wants to pay for someone to do the R&D and fabrications for a custom set of headers, the interest isn't there for the cost. it cost us almost $1300 a person when we had 5 sets of headers fabricated for the 3.6L engine
 

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ah, I just now noticed you have an 05.....so the 3.5/3.9 parts wont bolt up, but there are headers for cheap for the LX9 3.5 that you have made by OBX, haven't had too great of reviews tho, and you MUST have a PCM tune done to run headers, and only one place is able to tune that PCM on the 05/06s and that's Chris at WAMS
 

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LZ9 = 3900
LZ4 = 3500vvt
LX9 = 3500

3.9vvt and 3.5vvt are NOT the same engines. Block castings are different, heads are different, intake setup is different. 3900 also has oil jets underneath all 6 pistons, hence the oil cooler. All other 60* enigne only have oil jets under pistons #1 & #2. Fiero guys have tried mixing and matching other 60* manifolds with 3900 heads and nothing fits. As for exhaust, custom is the only way, as Sexy pointed out... (Pretty sure the LZ4/9 manifolds are not the same either...someone correct me if they know FOR SURE that this is not correct. 3900 exhaust manifold mounting surface has a different angle than all the other heads.)
 

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the LZ4 and LZ9 ARE the "same" engines, same block castings same exhaust manifolds/ catted downpipes same head designs the upper intake manifolds are interchangeable...... mabey if you had actual hands on experience you would know this instead of looking like an idiot arguing and stating incorrect information
 

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Ok guys im new here and I have an 08 lz4 and I have looked for simple mods to make power and cant find them and mr. Silver you could just gasket match your manifolds and not waste time buying shitty headers but like I said I have an 08 lz4 so I could be saying shit I kno nothing about
 

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TC...yea hit that button
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the LZ4 and LZ9 ARE the "same" engines, same block castings same exhaust manifolds/ catted downpipes same head designs the upper intake manifolds are interchangeable...... mabey if you had actual hands on experience you would know this instead of looking like an idiot arguing and stating incorrect information
Hmmmm....good thing I followed up on this. LZ9 and LZ4 are different blocks. Both engines share the same bore, but the 3900 is equipped with a larger-stroked crankshaft. The main journals are larger on the LZ9 crank, and the entire block is 'spaced' apart more, hence the LIM's from other motors do not fit a 3900. Yes the upper intakes are compatible, but practically all '96+ 60* motors have the same UIM bolt pattern. And the 3900 heads are different too, so I'll have to report back as to what it is cuz I honestly forget. (edit: 1.7 ratio rockers on 3900 too. Oh and not to mention a different oiling system inside the block. LZ9 has an oil cooler for sure, Idk if LZ4 does or not...)

I have torn out so many GM V6 motors it's not even funny. I converted my GA to 5-speed and recently replaced the clutch in my G6. Please dude I'm a ****in Diesel Technician, these cars are just simple little toys.
 
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