Do you want to do a 3900 swap? whats stopping you

[ericjon262]

I don't have anything to prove it, but I've seen many different flow benches test many different heads, and have similar results. something to remember here, is that 60 v6 heads open into the cylinder away from the wall, LS heads open down along the wall.

[geoffinbc]

Right but your talking valves only .020" different in size and a head casting light years apart. Vortec heads are better than camel hump heads. So it's easy to believe an LS1 or LS6 can out flow old small block heads. But with valve sizes .130" apart that is a huge difference. Along with that bigger valve goes a bigger port so I just can't see a 3900 flowing as much as an LS6. Are there any numbers from the same bench or even the same brand of bench to prove otherwise?

[ericjon262]

3900 heads with a 1.87" intake valve flows as good as an LS6 head with 2.0" valves?

LS1 heads have 2.00 inch intake valves and flow more and old camel humps with 2.02 intakes...

[geoffinbc]

3900 heads with a 1.87" intake valve flows as good as an LS6 head with 2.0" valves?

Found this website of head flow for ls1, ls6 and other heads, plus cam specs. Mimicing a ls1/6 setup you should see roughly the same horsepower per cylinder as an ls6 which should put the 3900 at 300 crank hp

Ls6 heads seem to flow close to stock 3900 heads in nearly all lift points. Thats a 400 hp v8 so about 50 hp/cylinder. Should be doable as well with a 3900 even though displacement per cylinder on a 3900 is slightly less.

http://www.smokemup.com/tech/ls1.php

[ericjon262]

Searched for head flow numbers for lx9 and didn't find anything but going off memory I thought it was around 220 cfm at .500 or maybe .550 lift.

I have seen two different head flow numbers for the lz4/9 WOT tech flowed them to about 245 at a very useable lift of .500. Another test was 255 cfm at .500 lift. So lets say 250 cfm. Exh for the lz4/9 was 170 cfm at .500 lift for both tests.

stock lz9 with a cam swap and 75mm cable tb which the lz4 intake manifold has a 75mm opening factory, should do 300 crank hp. No lx9 is going to hit that with just two mods. Lx9 advantage is abundance and ease of swap. Its a good candidate, but you are right, its not the step forward for the amount of work and extra work that most are willing to take to get that extra 50 hp from an lz9.

my next engine will most likely be an LZ4, I like the idea of the 3.9 inch bore, which is probably part of the reason the LZ4/LZ9 heads flow better than the LX9 I think 300 hp should be doable.

Searched for head flow numbers for lx9 and didn't find anything but going off memory I thought it was around 220 cfm at .500 or maybe .550 lift.

I have seen two different head flow numbers for the lz4/9 WOT tech flowed them to about 245 at a very useable lift of .500. Another test was 255 cfm at .500 lift. So lets say 250 cfm. Exh for the lz4/9 was 170 cfm at .500 lift for both tests.

stock lz9 with a cam swap and 75mm cable tb which the lz4 intake manifold has a 75mm opening factory, should do 300 crank hp. No lx9 is going to hit that with just two mods. Lx9 advantage is abundance and ease of swap. Its a good candidate, but you are right, its not the step forward for the amount of work and extra work that most are willing to take to get that extra 50 hp from an lz9.

[ericjon262]

Stock LX9 heads flow about what LS1 heads flow, I wouldn't doubt the LZ heads outflow them. the TB is useless if you run a cable throttle, would need to be replaced either way. at this point, I feel like removing the VVT aspect from the LZ engines is backwards, yeah, you get the better flowing heads, but it's not the full step forward that it should be. the LZ9 computer is also very tunable, much more so than I thought using tunercat obd2. eventually, I plan to contact Mast Motorsports about their line of VVT LS cams, since the design principle is pretty much the exact same as the LZ engine's.

Ms3 pro controls the vvt cam beautifully throughout its whole range of motion

Even more reason not to have additional sets made up.

I don't think a lot of people realize that you need the spacers because most haven't gotten that far with the swap or don't think a cam is an option for the engine. The previous discussions about this are fairly buried on this site.

In general, car forums are dying and the aftermarket imo is too. Its so niche. Most people buy a new car and just drive them these days. People are more interested in the latest hand held phone or tablet or electronic gadget, video game system, than restoring or modifying a car that the money isn't spent on cars. Not only that but the lack of economic growth and confidence plays a role too.

Discussions about needing the spacers might be buried on this site, but a simple google search on the lz4/lz9 swap turns up info about the camshaft swap and special cam bearings being needed so I think the knowledge is out there for those that search for it. I think Marc at BCC realized this and sticks to making products that move instead of designing and making new ones. There is nothing wrong with that.

I see a lot of people like keeping things simple and cheap like a iron head 3.4 or lx9 when doing a swap. Its strange because the lz4 is a 3.5 and has a bigger tb, bigger intake runners, and better flowing heads than a lx9, yet no real demand for the lz4 is there let alone the lz9. I think this is because with a lz4/9 you need the spacers, then the cost of the cam and the springs and pushrods, plus the teardown and install of the parts. With an lx9, none of this is necessary so its cheaper and easier for a smidge less power. Not worth it to most people who just want to get something in so they can drive the car.

LZ heads flow as good or slightly better than ls1 heads, which doing the math, can do 300ish bhp with a cam swap and a tune. My own research has shown this of people who have swapped cams. You would think the demand would be there but its not yet. Like I said maybe in a few more years or after a few more document the swap as lots of people don't like to be pioneers.

[carbon]

I started this thread to do a little bit of research on whether or not I should run a batch of cam bearing spacers like what BCC made up. It appears that not too many people that visit this forum aren't doing a 3900 swap, and a few that are, are looking into keeping the VVT. Maybe later down the road it will be worth it to have extra sets made up, but I can't justify the extra cost on top of the two sets for myself just to have them sit on the shelf waiting for a buyer.

I don't think a lot of people realize that you need the spacers because most haven't gotten that far with the swap or don't think a cam is an option for the engine. The previous discussions about this are fairly buried on this site.

[farmerz24]

Ms3 pro controls the vvt cam beautifully throughout its whole range of motion

[caffeine]

I'm interested in spacers if the cost isn't outrageous.

I started this thread to do a little bit of research on whether or not I should run a batch of cam bearing spacers like what BCC made up. It appears that not too many people that visit this forum aren't doing a 3900 swap, and a few that are, are looking into keeping the VVT. Maybe later down the road it will be worth it to have extra sets made up, but I can't justify the extra cost on top of the two sets for myself just to have them sit on the shelf waiting for a buyer.

[caffeine]

A '7165 also happens to be only 5 pins away from an 85 Camaro ECM, plus wiring in the MAP sensor in the engine bay.

[caffeine]

I've also been interested in trying a '7165 with $12p. $12p has a programmable PWM output that would probably be perfect for VCT