99 L29 454 build

[Scottm]

Tons of great news and great pictures, but I keep forgetting my camera. After some training I ran the flow bench myself so my machinist could keep doing other stuff. It was slow going at first while I was getting the hang of it. And the bottom line is... These heads flow well, as they should, considering a 2.06" intake with 238/240cc runners. I tested only 2 cylinders on the driver's side head, cyls 5 and 7. First the head was run bare with a flow guide, and then with manifolds attached. Each test was run at 28 inches of water differential and ambient temp of 80F. Cfm flow is calculated by multiplying a % reading from a manometer times the max flow of the range setting used. For example, Range 4 has a max flow of 298 cfm, so 50% on the manometer means 149 cfm flow.

Lift .100 .200 .300 .400 .500 .600
#5 Int (good port) 80.2 153.5 192.2 233 264.4 295
#5 Ex 52.5 100.9 133.8 161.6 177.6 190.4

#7 Int (bad port) 74.5 149 199.6 237 268 283
#7 Ex 52.5 104.9 138.3 164.8 176.4 192

#7 Int stock mani 71.5 138.6 171.4 190.7 205.6 214.6
#7 Int mod stock 75.7 141.5 174.3 198.1 214.9 225
#7 Int Edel Vict Jr 75.0 149 195.2 230.6 256.3 266.7

There are so many interesting things to see. First is the peak flow, 283 bad/295 good. I figured it would be close to 300. The rule of thumb for performance engines is hp can be roughly twice the peak intake flow number, assuming good intake manifold, exhaust, comp of about 10:1, and cam of 230-240 degrees at .050. By that rule, these heads are capable of about 600 hp. Of course it will never make that much in emissions legal trim with the stock manifold. Unmodified, the manifold kills flow by 70 cfm. And this was with the manifold completely bare, so air was flowing in from all around. In the truck the flow will be even more restricted. The port matching I did increased flow throughout the range. The Victor jr naturally was much better. But I am surprised to see that even it restricted flow to less than the bare head flowed. Maybe that's why tunnel ram manifolds are known to make the most power.. Tomorrow I will post pics for sure.

Edit: The spacing on the table I made was lost. I might need to post an excel graph or a picture of the table to make it easier.

 

[Scottm]

I have pics on my phone too, duh.. The first pic is the valve lifting thing I made. The second pic also shows the flow guide I made out of 3/4 inch thick acrylic. Maybe my flow guide works better than most, (and probably a lot better than ridges of clay) to explain the high intake flow.

 

[L31MaxExpress]

Seems like it will starve a bit at 454 cubes, but should work ok for a lower rpm setup. Stock truck intake will be done by 4,000-4,500 rpm anyway. The long runner length and multiple tight bends will kill off rpm potential before the flow does.

My ported L31 manifold with the spider and plenum top with throttle body in place at WOT hit 280+ cfm. Fairly consistently through all ports. 7 ports duct taped off. With the manifold in place on the head was still in the 275 cfm range at 0.550 lift.
.
Head flow through a ~215cc intake port and ~62cc exhaust port. 2.02/1.60 valves.
.200----------138-------107
.300----------192-------138
.400----------241-------164
.500----------274-------183
.600----------291-------193
.700----------295-------199

 

[L31MaxExpress]

Some of the work I did on the L31 manifold. It was
obvious GM hit their power goals on the 350 Vortec and did not care how terrible the manifolds really turned out. I took the best of the 3 I had and cleaned it up. I am glad I had the larger head ports to match because the factory manifold to factory head port alignment was simply terrible. I also opened up the entry to the runners and gave it more of a radiused bellmouthed entrance as much as possible. I also opened the openings up to the very edge of the plenum top, good or bad.

Looking forward to seeing the rest of your work and the end results. I would like to build a 496 with an extrude honed factory L29 manifold and put it in a 454 SS clone but a 96+.

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[Scottm]

Wow that's huge flow on a head/manifold combo. It will make big power with enough fuel. What are you using for an ecm?

 

[L31MaxExpress]

Wow that's huge flow on a head/manifold combo. It will make big power with enough fuel. What are you using for an ecm?

Green/Blue LS (came out of a 2005 6.0L DBC van) with Mexican GMT800 L31 base tune. Injectors are 48 lb/hr units to run on E85.

 

[Bu327]

Congrats Scott, looks like some good numbers. Now you’re gonna want to lift those valves that far!

 

[Scottm]

Thanks! I had my stock cam reground to lift around .520 iirc.

 

[Scottm]

Here's a pic of the stock manifold on the head. There are gaskets between the mani halves and on the head, and there is an injector in the #7 cyl. The second pic is an example of what makes this stuff so time consuming. Working that boss and going to a button head screw may not do anything, but then maybe it will reduce turbulence and add a ft-lb of torque...

 

[Christian Steffen]

Tons of great news and great pictures, but I keep forgetting my camera. After some training I ran the flow bench myself so my machinist could keep doing other stuff. It was slow going at first while I was getting the hang of it. And the bottom line is... These heads flow well, as they should, considering a 2.06" intake with 238/240cc runners. I tested only 2 cylinders on the driver's side head, cyls 5 and 7. First the head was run bare with a flow guide, and then with manifolds attached. Each test was run at 28 inches of water differential and ambient temp of 80F. Cfm flow is calculated by multiplying a % reading from a manometer times the max flow of the range setting used. For example, Range 4 has a max flow of 298 cfm, so 50% on the manometer means 149 cfm flow.

Lift .100 .200 .300 .400 .500 .600
#5 Int (good port) 80.2 153.5 192.2 233 264.4 295
#5 Ex 52.5 100.9 133.8 161.6 177.6 190.4

#7 Int (bad port) 74.5 149 199.6 237 268 283
#7 Ex 52.5 104.9 138.3 164.8 176.4 192

#7 Int stock mani 71.5 138.6 171.4 190.7 205.6 214.6
#7 Int mod stock 75.7 141.5 174.3 198.1 214.9 225
#7 Int Edel Vict Jr 75.0 149 195.2 230.6 256.3 266.7

There are so many interesting things to see. First is the peak flow, 283 bad/295 good. I figured it would be close to 300. The rule of thumb for performance engines is hp can be roughly twice the peak intake flow number, assuming good intake manifold, exhaust, comp of about 10:1, and cam of 230-240 degrees at .050. By that rule, these heads are capable of about 600 hp. Of course it will never make that much in emissions legal trim with the stock manifold. Unmodified, the manifold kills flow by 70 cfm. And this was with the manifold completely bare, so air was flowing in from all around. In the truck the flow will be even more restricted. The port matching I did increased flow throughout the range. The Victor jr naturally was much better. But I am surprised to see that even it restricted flow to less than the bare head flowed. Maybe that's why tunnel ram manifolds are known to make the most power.. Tomorrow I will post pics for sure.

Edit: The spacing on the table I made was lost. I might need to post an excel graph or a picture of the table to make it easier.

You're a damn hero for testing the heads with the intake manifold. I've always wondered how much it sucks lol nice work!