3500 vs 3900

[SappySE107]

It was a 2008 G6 GTP, and I do not have any way to mess with it as the car is 1300 miles north of me now. Not a swap with DBW either (YUCK).

You can pretty much bet i won't be doing anything with GM FWD cars now. I tried to give away free tuning and got nothing down here.

[Fastmax32168]

I have never posted ported flow numbers, or pics, or cc measurements.

The 3900 has the same exact exhaust port as a 3500, with the valve seat opened up for the larger valve, and the throat modified to blend it back to the stock 3500 size. If you compare flow with manifolds, its not that biased at all.
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You may not have posted them personally but I used these #s for 3900 heads that John posted here: http://www.fullthrottlev6.com/forums...d-flow-numbers

And I compared them to the numbers posted on the WOT site for 3500 heads here: http://wot-tech.com/shop/gm-60v6/str.../prod_237.html

There is a pretty big difference in those exhaust port #s, both ported and un ported.

So where did I go wrong and which set of exhaust port numbers should I be using?
Roy

[bszopi]

You are looking at 3500 (LX9) head numbers from WOT-Tech, not 3500VVT. Completely different heads.

[SappySE107]

Those are not my numbers for the 3900 heads. It also says there was no tube on the exhaust, so that doesn't work to compare with.

http://60degreev6.com/forum/showthread.php/46051-3900-flow?highlight=3900+flow

[Fastmax32168]

You are looking at 3500 (LX9) head numbers from WOT-Tech, not 3500VVT. Completely different heads.

Well, you are right about that, and to be honest I had forgotten all about the 3500VVT. My original post was to compare the power I could get out of the LX9 which is available cheap and easy to me, to the power I would get if I spend the additional cash for the 3900, which the yards seem to want much more for, and retrofitted it back to non VVT technology for my next project.
So they are different heads yes, but they are also what I was looking to compare. But my lack of clarity may account for some of the exhaust port confusion.
Roy

[Fastmax32168]

Those are not my numbers for the 3900 heads. It also says there was no tube on the exhaust, so that doesn't work to compare with.

http://60degreev6.com/forum/showthre...ight=3900+flow

OK thanks.
Roy

[NateD4]

Why would you want to take the VVT stuff off? You can regrind the cam (though I seriously doubt its even needed). The VVT can be tuned using an HP tuner or EFI Live. You could probably lock it out just as easy. Especially if you can find a shop that has a tuner already, you'd just have to pay their license fee for the VIN.

Perhaps I'm missing something but the VVT is there to do two things. 1) Give you better cruise numbers, and 2) To give you the cam advance and retard you need for high and low RPMs. Removing it seems like a lot of trouble compared to just setting a fixed value in the computer.

Just my thoughts.

I'll be sticking with the VVT on the 3900 I'm building.

Also I'm not sure why you think the 3900s are expensive. They are pretty darn cheap (which is why I picked one). I think I payed less then a grand for the entire engine with accessories, harness and computer.

Another cheap engine is the 5.3L V8. I've seen a complete drive train package from one of those go for less than $1500 with reasonably low mileage.

[Fastmax32168]

Why would you want to take the VVT stuff off?.

Because I can.
Roy

[NateD4]

Not sure it makes sense to me... Have fun I guess though.

[SappySE107]

You don't make much sense either. If you want to discuss the merits of DBW and VVT, start a new thread please.

[ForcedFirebird]

You may not have posted them personally but I used these #s for 3900 heads that John posted here: http://www.fullthrottlev6.com/forums...d-flow-numbers

And I compared them to the numbers posted on the WOT site for 3500 heads here: http://wot-tech.com/shop/gm-60v6/str.../prod_237.html

There is a pretty big difference in those exhaust port #s, both ported and un ported.

So where did I go wrong and which set of exhaust port numbers should I be using?
Roy

Roy, those numbers are taken from a member's post before and after on the same bench that we have no way of knowing how it compares to our bench. I was just showing an example at FTv6 because of all the love the 3800 gets over there.

Why would you want to take the VVT stuff off? You can regrind the cam (though I seriously doubt its even needed). The VVT can be tuned using an HP tuner or EFI Live. You could probably lock it out just as easy. Especially if you can find a shop that has a tuner already, you'd just have to pay their license fee for the VIN.

Perhaps I'm missing something but the VVT is there to do two things. 1) Give you better cruise numbers, and 2) To give you the cam advance and retard you need for high and low RPMs. Removing it seems like a lot of trouble compared to just setting a fixed value in the computer.

Just my thoughts.

I'll be sticking with the VVT on the 3900 I'm building.

Also I'm not sure why you think the 3900s are expensive. They are pretty darn cheap (which is why I picked one). I think I payed less then a grand for the entire engine with accessories, harness and computer.

Another cheap engine is the 5.3L V8. I've seen a complete drive train package from one of those go for less than $1500 with reasonably low mileage.

Not sure it makes sense to me... Have fun I guess though.

Nate, You keep plugging up everyone's threads with your ideas about the 3900. In fact the 3900 initial purchase price is generally double the cost of a 3500 and need more to make fit in most applications. How about YOU prove everyone else wrong before stating so based on your assumptions about the 3900. People here already have real life experience with the 3900 and 3500, until you have results it's all talk.

[NateD4]

Perhaps I'm not familiar with the purchase price of a 3500 but I paid around $600 for the 3900 I have (around $800 shipped). And I got it with 17K miles, harness, computer, A/C Compressor, starter, alternator and all sensors etc... pretty much everything I need for a swap.

As I also said the LS4 (5.3L) from the FWD Chevy SS and Grand Prix seem to also be selling at an affordable $1500 complete with transmission.... Are the 3500's really that much cheaper? I guess you could probably pick one up for a few hundred bucks with higher mileage on it.

[bob442]

some of them can be had for 150$ and fit in a 4 door car to pick up

[Joseph Upson]

some of them can be had for 150$ and fit in a 4 door car to pick up

Two seaters to.