3.9L LZ9 engine internal upgrade & performance?

[SappySE107]

You didn't need a larger valve for the intake to gain flow, so why would you need a larger exhaust valve when the same pressure increase exists on the exhaust stroke?

[Joseph Upson]

You didn't need a larger valve for the intake to gain flow, so why would you need a larger exhaust valve when the same pressure increase exists on the exhaust stroke?

It appears more practical to go with a larger exhaust valve being the smaller of the two and space limitations and given your pointing out that the exhaust runner is not optimized to the same extent as the intake, that suggests one more reason to start with that side since it would hinder any further increase on the intake side in its current state.

Desktop Dyno is not state of the art in engine simulation but it does show a significant enough increase in performance for me to make it a worth while consideration provided the size valve I was considering could be made to work. The purpose is to make changes that will improve performance instead of just turning up the boost pressure. Increasing the size of either valve would do this, I chose the exhaust side. The idea never had anything to do with a need.

[mrtohil]

New intake valve seats are installed. Pics are in the Photobucket. After I'm done with cutting the seats, I'll flow the heads again and see what was gained/lost. Unfortunately I could only get pics of the new valve on the new seats, and not on the original seats.

[Joseph Upson]

New intake valve seats are installed. Pics are in the Photobucket. After I'm done with cutting the seats, I'll flow the heads again and see what was gained/lost. Unfortunately I could only get pics of the new valve on the new seats, and not on the original seats.

What size valves did you use?

[mrtohil]

We have started to cut the angles on the seats to match the new valves. The first valve seat came out alright but the contact point on the valve was a little too close to the edge. We moved the cutting bit in a hair and cut the next seat. This one came out much better, in both the contact point and in the actual cut.

The new valves specs are:

Intake: 2.00in
Exhaust: 1.550in

Stock sizes are:

Intake: 1.87in
Exhaust: 1.525in

[SappySE107]

I like those sizes. Got any pics?

[mrtohil]

Sorry I haven't been updating more frequently. So far I have reflowed my heads with the new seats and valves. I actually lost flow through most of the valve opening until the top end where I gained significantly, which to be honest was a little disappointing. There is this one area in the seat where we think might be affecting the flow. We'll see after I make some minor changes and reflow the head. I'll try to post actual numbers and pics later.

[mrtohil]

Okay, here's the latest on the project. After careful porting of the seat to eliminate a small step behind the seats, I was able to bring the head back to some good numbers which I will post. I am also working on fitting LS1 roller rockers to the heads.

As was shown on a previous post, the heads can be improved upon with just good port work & stock hardware. And if you choose to leave it at that, is acceptable. But of course, we have to push the envelope (or at least I do because I'm curious). So I stuck LS1 valves. Sent a pair of valves to Ferrea Racing Components to find feasibility of custom valves. And behold... the stems are almost the identical (stock: .313... LS1: intake: .3135 exhaust: .313). The exhaust valve size is almost identical (stock: 1.524.. LS1: 1.550). The difference come in the length (slightly longer, will post exact numbers later) and the intake size (stock: 1.870... LS1: 2.0). Si I decided to try it out. I replaced the seats for the intake and cut both to accept the new valves. I also unshrouded the chamber around both both valves, primarily on the intake side. After initial testing after re-porting to size out the intake port to the new seat, I actually lost flow numbers (Of course I wasn't sure what would happen. I know that bigger is not always better. I knew that there was a possibility that I would have a pair of nice ported paper weights and I might have to start all over, which is still a possibilty). After inspecting the head, it was found that there was a small ridge behind the seat. So the seat was actually just jutting out into the airflow. So I touched up the seat edge to make the transition as smooth as possible. Retested the heads, and much improved numbers.

[mrtohil]

Session 1: stock, no work performed
Session 2: ported, stock hardware
Session 3: re-ported, LS1 valves
Session 4: re-ported & repaired, LS1 vlaves



........................Lift:..........[0.100].........[0.200]........[0.300].......[0.400]........[0.500].......[0.600].......[0.700]...............Average CFM.............Max CFM

Session 1(intake)_________62.40_______128.60____186.80____ _218.90_____232.10_____238.50_____NA____________17 7.88____________238.50
Session 1(exhaust)________52.60_______100.00____138.20____ _150.10_____154.70_____155.80____156.50_________12 9.56____________156.50

Session 2(intake)_________67.10______131.90______191.10___ _236.00______250.00____257.30_____261.10_________1 99.21____________261.10
Session 2(exhaust)________52.60______101.30_____134.10____ _155.70_____166.60____170.30_____172.00_________13 6.09____________172.00

Session 3(intake)_________59.70_______115.30_____169.00___ _217.60______253.30____273.80_____257.90_________1 92.37____________273.80
Session 3(exhaust)_______53.40________102.00_____136.90___ _157.50_____165.50_____169.60_____172.00_________1 36.70____________172.00

Session 4(intake)_________63.30_______125.40______187.20__ __238.70_____263.70____265.10______266.20________2 01.37____________266.20
Session 4(exhaust)________53.60_______105.30_____145.70___ _163.40_____168.90_____171.10_____172.40________14 0.06____________172.40

[robertisaar]

you LOST flow at .700 intake session 3?

[mrtohil]

Yeah, i actually lost it everywhere until 0.500.

[robertisaar]

i mean, look at the reading .100 less... and then flow was lost?

[mrtohil]

The next step for me now is to check valve to valve clearance and valve to piston clearance. I also have to check what the new valve spring installed height will be and if there wil be any issues with coil bind.
I am currently working to fitting LS1 roller rockers onto the head. I've posted pics of what they look like mock installed. There are four problems with fitting LS1 rockers these heads...but the end result I think is well worth it.
The first is that I needed to find rockers that were not shaft attached. As some as you know, SBC valvetrain is pretty simple. And the setup is simple. The valves are all in a line, non splayed. Also, the intake and exhaust valves are in the same place for every cylinder. So, most aftermarket rockers are mated together in pairs or by bank. This does not work here. LZ9 valves are splayed and on top of that, two cylinders have the valve placement swapped. So I was able to find independent roller rockers.
Second, the mounting pedestals for the rockers are different, but the same. LZ9 rocker pedestals have a wide, almost gem cut look to them. And each pedestal has an aligning tongue, which matched a groove in the head. SBC pedestals look like a tube with a base on it. These aftermarket units have metal bar the aligns them properly to the valve tip. Also, the new rockers are substantially thicker on the pedestal mounting area, both on the sides and for and aft. So, my teachers were able to find someone to machine the top of the original pedestals to match the aftermarket ones, while still retaining the alignment tongue.
Third, inside each pedestal, where the mounting bolt goes through is a little treaded area. This basically screws the pedestal to the rocker. Which is fine if you're using the same mounting hardware. But that is not possible. The mounting bolt for is different for SBC. What's interesting is the bolt thread size and pitch are the same, but the shoulder at the top of the bolt is what's different. So I found better replacements with some allen bolts which are stronger and are the appropriate length. But the threaded section inside the pedestal was not allowing full proper contact of the pedestal to the head. Allowing the rocker to feel loose. Loose bolt and aluminum don't mix well. So I drilled each internal threaded section out. Now there is full contact everywhere on the pedestal and rocker. And the rocker bolts down correctly.
Fourth, I test fit the rockers on different positions on the head. There were no issue with clearance until one. There is one position on each head where the valves are splayed close enough and just foreword and aft of each other to have one rocker body rub against the fulcrum of the other. I believe I'm going to have to grind off a little off the fulcrum to provide clearance.
This can be a fifth, but it will also depend if you have the longer valves like I do. And if rocker to valve tip contact position is important to you. I will have to shim each pedestal differently(if required) to move the rocker upward to have the tip roller be in the proper valve stem tip position.
That's it for now. Hope you like the latest pics and info.

[bszopi]

Where are the pics...?

EDIT: Nevermind... http://s296.photobucket.com/albums/mm174/mrtohil/LZ9/

[mrtohil]

I'm sorry robertisaar, I can't seem to understand what you're asking/stating. Please clarify for me.