3.9L LZ9 engine internal upgrade & performance?

[mrtohil]

OKay, back to LZ9 performance!

[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]

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]

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]

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]

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]

"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]

"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]

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.

[SappySE107]

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

[mrtohil]

I used the clay on the intake. The exhaust was left open. Later this quarter I will get different sized tubing to find which works optimaly with these heads to make headers.
Before I forget, wasn't there someone selling exhaust header flanges for 3.5/3.9? I've been looking for them to be able to port the exhaust correctly and so I do that exhaust tubing test later. And if someone has a picture of the exhaust manifold to exhaust manifold gasket relation, that would be awesome! I'm not really looking forward to buy some stock exhaust manifolds so I can port correctly only to not used them because of the headers made.

[SappySE107]

You don't size headers by flow on a bench and you shouldn't port exhausts out to gaskets or flanges. Flowing without a tube gives you a false peak reading as well.

Ill have more 3900 flanges soon but they are meant for 1.75" tube. Primaries are sized by output of the motor and also powerband.

[mrtohil]

I checked the volume on my heads. I think GM was shooting for 36cc. I got 36.4cc on head "A". 35.8cc for head "B". After decking the heads I ended up with 33.5cc on "A". And 34cc on "B".

[mrtohil]

I also want to inform that I currently disassembling the 6spd manual that comes mated with the LZ9...the F40. I am also taking pics and posting in under my photobucket. I'll be posting what I find here also.

[mrtohil]

Latest update.... I'm having my camshaft made be Racer Brown. The connecting rods are being made by Cunningham Rods. It'll be about 2 months time to make. Which unfortunately will be outside the window for the final quarter for school. Looks like I'm going to have to take the course again...this fall...could be worse.