3.9L LZ9 engine internal upgrade & performance?

[SappySE107]

Did you use a tube on the exhaust and a clay bell shaped entrance on the intake?

[mrtohil]

As you can see, these heads are already good to begin with. These heads flow better than many V8's in the classroom. They flow significantly superior to the 3.1L heads and an older Grand Prix GTP engine (iron head & block, 90degree V6, can't remember displacement), Pre and Post. Mostly what is left to do is port match and cleanup.

[mrtohil]

"Post" Exhaust specs: 1: 52.60; 2: 101.30; 3: 134.10; 4: 155.70; 5: 170.30; 6: 172.

The Max CFM for the exhaust is 172.00 @ 0.700
Average CFM was 136.09.

[mrtohil]

"Post" intake specs: 1: 67.10; 2: 131.90; 3: 191.10; 4: 236; 5: 250; 6: 257.30; 7: 261.10

Max CFM for the intake is 261.10 @ 0.700.
Average CFM was 199.21.

[mrtohil]

Here are the post specs after significant porting was done. These numbers can be taken at face value if 1. your using the same valves and 2. if you don't port match the exhaust. As you can see by the pics (check link earlier on this topic), the exhaust manifold gasket is significantly bigger than the exhaust port. And, since I don't have an exhaust manifold to see if the the wide opening is the actual size, I am very hesistant to port out to the gasket. So the exhaust is cleaned up in the port.
The second issue is that I am possibly getting undercut valves (aka competition valves). These have less material behind the valve, which means less surface area to obstruct the airflow going past the valve. This could also alter my CFM numbers.

[mrtohil]

Pre Exhaust specs: 1: 52.60; 2:100; 3:137.20; 4: 150.10; 5: 154.70; 6:155.80; 7:156.50

Here the max CFM for the exhaust is 156.50 @ 0.700
The average CFM was 129.56.

I went to 0.700 because I could. I would go to 0.700 on the intake later in the post to include this, but the increased flow value is not significant.

[mrtohil]

Pre Intake specs: 1: 62.40; 2:128.60; 3:186.60; 4: 218.90; 5:232.10; 6:238.50

As you can see the max CFM for the intake is 238.50 @ 0.600.
The average CFM was 177.88.

[mrtohil]

There are the specs for my heads. The figures that stay the same will be spelled out here. The head were flowed at the industry standard of 28.0in of H20. The intake valve diameter was set @ 1.870in. Exhaust valve @ 1.524in. Valve stem diameter was set @ 0.313in. Bore @ 3.930in. Stroke @ 3.310in. These figures were constant for pre & post(even though this is not really the post yet, I'll explain later).
I will also refer to 1-7. "1" being 0.100in. of valve opening, "2" equals 0.200in. of valve opening, etc. Results after the valve opening are in Cubic Feet per Minute (CFM).

[mrtohil]

This quarter is cylinder head performance. We are preflowing, porting, and post flowing the heads. I will post the pre and post flow numbers here. Unfortunately my scanner isn't working so I can not just post the print out of the specs.

[mrtohil]

OKay, back to LZ9 performance!

[gectek]

those are on an assembled engine. they will look like that, but you have to use the plugs so that everything works right

and as long as the ports on either the block deck or the cyl head deck are large enough...shape doesnt matter

There are no freezeplugs on my 3900 heads, nor is there any proof that there are left and right heads. There is proof that there are not, and I am looking at them.

In all likelyhood your heads are different than mine. There is a cap at the back end of both of my heads that I call a freeze plug because it's made of metal and that's what it looks like.

If you swap the heads around leaving everything else the same and bolt everything back in place, water will poor out the back of the cylinderhead and there will be no return coolant flow from the front and that's why I address them as left and right.

Some others address them as front and rear all because of a technicallity that prevents them from being bolted on either side of the engine without making a modification, that being removing the freeze plug, coolant outlet cap "thingy" (whatever you want to call it) from one end of the head and placing it at the other if you want to move the head from one bank to the other and have the system function normally.

You may not think much of it, but I like to know details like this. As for the deck surface, I should have taken pictures when I thought to do so upon seeing the unusual pattern, understand I'm referencing from one end of the cylinder head to the other end of the cylinder head on the same cylinder head, in other words folding the surface in half does not produce a mirror image.

I'm talking about the plugged holes in the back of the heads posted in the pictures for others who may be wondering.

[SappySE107]

There are no freezeplugs on my 3900 heads, nor is there any proof that there are left and right heads. There is proof that there are not, and I am looking at them.

i thought this thread was about the 3900 i was talking about the 3900...the 3500 non vvt and the heads have the same pn also...but you are right...there is a coolant temp sensor, but idk how they actually come...ive ordered them in, but i havent looked at them, lol

Coolant sensor shouldn't be a problem as I can see a hole in what appears to be the same location on the front of the aft cylinder head. There is a cutoff date showing up on GM Parts direct, I was on the wrong GM site which showed some different prices. The direct site is showing the same price for both heads but an 06 and 06-07 distribution. I would really like to get to the bottom of the connecting rod length differences that have come up which show the same kind of cutoff date.

Something has to be different between these engines and there's no telling how close they are to documented specs. Two different rod lenghts have to be corrected for by either a piston change or crankshaft change.

Speaking of which, the 05-06 crankshaft is more expensive than the 07 crankshaft, I don't believe it's safe to swap anything across years as far as the rotating assembly with these engines, especially since when ordering parts the VIN number is almost a requirement. I distinctly remember the 3900 crank looking a little bit more trim than my 3500 crank and I'm almost positive I wrote that in a thread some time ago. It maybe heavier or possibly stronger from additional processing that is no longer being performed.

http://www.gmpartsdirect.com/catalog/frameset.cfm

[gectek]

i thought this thread was about the 3900 i was talking about the 3900...the 3500 non vvt and the heads have the same pn also...but you are right...there is a coolant temp sensor, but idk how they actually come...ive ordered them in, but i havent looked at them, lol