I recently flow tested a new pair of LS7 heads and intake manifold. I realize LS7 head flow data has been previously posted but I thought I’d add a bit more data to the mix. The heads were casting #8452. The test valves are oem. Apparently the titanium intake valves are on hiatus for a while, but I managed to scare up a couple for testing and mockup. The intake head flow is as follows:

Lift __.100 _.200 _.300 _.350 _.400 _.450 _.500 _.550 _.600 _.650 _.700
#1 Int. 75.5 162.7 245.5 279.1 305.8 326.4 344.5 360.2 370.7 333.7 336.1
#2 Int. 75.3 163.5 244.0 277.0 303.8 323.7 342.2 359.4 370.6 332.3 335.9

The heads were tested on a SF 600 flow bench.
The intake ports were tested with a radius flow plate on a 4.155” test bore.
I then tested the same ports with an LS7 intake manifold bolted in place:

#5 Int. 74.9 157.7 228.2 254.8 276.9 293.9 306.5 317.4 325.4 331.4 302.2
#7 Int. 75.0 158.3 227.6 254.5 276.0 293.7 306.5 316.9 326.0 331.4 304.8

Due to word wrapping I trimmed a couple of lift points off below .300" and above .700".
As you can see the intake manifold extended the flow peak by .050”, though it reduced peak flow by 45cfm. The flow peak is within the designed lift curve. This is very impressive flow under the peak. Great job designing and machine finishing the ports, chambers and seats.
On the exhaust side, the exhaust ports flow is as follows:

Lift ___.100 _.200 _.300 _.350 _.400 _.450 _.500 _.550 _.600 _.650 _.700
#1 Exh. 57.5 118.8 176.7 207.3 221.7 229.7 235.9 240.8 243.9 246.2 247.9
#2 Exh. 26.2 115.4 168.5 194.4 206.2 213.4 218.5 222.9 225.6 227.8 228.9

The #1 exhaust port was tested with a 1.875” dia. Pipe 2.5” long.
The #2 exhaust port was tested with out a test pipe.

The runner volumes are as follows:
#1 intake runner = 259.0cc
#3 intake runner = 259.4cc

#1 exhaust runner volume = 86.4cc
#3 exhaust runner volume = 85.0cc

#1 combustion chamber volume = 70.0cc
#3 combustion chamber volume = 70.4cc

This should go a long way in helping explain why the LS7 is such a great value. The airflow technology in the cylinder heads and intake system alone makes the engine package a hot rodder’s dream. The brain trust that developed the port, seat and chamber profiles deserve wide applause. Congrats on a job well done all.

Richard

 

Awesome Data Collection Richard! Thanks.

 

Excellent data. Helps illustrate how even the well-designed LS7 intake manifold can knock down flow. I'm curious how the LS7 intake manifold competes against a ported FAST 90mm intake for a cathedral port LS1? For example, if you had an ETP 265 cathedral port head (with similar flow numbers to the LS7 head), would a ported FAST 90 knock the flow down less than a factory LS7 intake on LS7 heads?

 

Cool, someone finally tested with an intake. Yeah, it's neet to see that the ls7 intake prolonged the high lift flow; however, fairly well pre-dicted that the intake would limit flow to some extent, as high as 13% in the higher lifts.

Edit: That's a significant drop in air flow from .600 up without the intake. I guess valve angles are too shallow and/or the shortside is to steep? Any head experts wanna touch on this one???

 

great here comes LSX with another $8,999,999,999.05 plastic intake

 

DO A SEARCH--------287and change

 

The intake ports designed airflow achieves the objective peak flow a bit past the cams max lift. It appears that the design of the short side radius, throat dia., valve seat profile, valve back cut, and combustion chamber shape are optimized to produce as much flow within the maximum valve lift window. This design is not by accident. Yes, it's possible to rework certain aspects of the short turn radius, seat throat and valve seat to raise the point at which maximum flow occurs. Usually at the detriment of flow losses in the lower end of the lift range.

Good stuff.

Richard

 

Great info on the LS7 heads and intake!


BTW, are the intakes on the street yet and if so who has them?

 

Thanks for the numbers! I'd love to see a ported LS7 head flowed with intake vs. a nice cathedral port LSX head with similar intake runner volume and FAST 90/90.

 

Best LS7 post yet! Thanks Richard!

I'm not sure that I can agree that this is a "well designed" intake! I'll post a pic later which shows how the #2 cylinder's inlet flange interferes dramatically with the air intake from the throttle body thus preventing a good intake charge to the rear intake passages!

 

Like I said, in this config, exhaust is enough for the intake.

I don't think there is a reason for these huge flowing exhaust ports on an N/A app. Once again, as long as port is right size and shape I don't think the numbers are as important as the intake side. Reason is, the exhaust is at all times at much greater pressures than 28" of water/mercury or whatever indicates.

If someone can get the intake side flowing to 350CFM with the intake mani attached then everyone will be happy.

With the LSX normally the intake bolted up results in less than 300CFM even with the best heads ( 350,360CFM ) attached to them. So there is a gain as things stand currently.

 

Well consider that if you improve the exhaust side of the head you can also delay the opening of the exhaust valve which will promote better BMEP through the range of the motor based on pro-longing the power stroke while at the same time avoid pumping losses as the better flowing exhaust port still allows the exhaust gases to be removed without the piston having to physically push them out

 

Interesting that @ .600" the intake knocks the 370cfm down to 326, but @ .650" it only knocks 333cfm down to 331 then goes really downhill @ .700". Makes you wonder if playing with porting that intake a la Mr. Mamo, real gain could be found in there.

 

I had an unpopular opinion that the exhaust side did not need so much duration
to "help" it, even though the split % doesn't look "great".

 

awsome info.
I too would love to see a ETP 265 head and a ported fast 90 incomparision.

 

yes buts whats the price difference between the two setups?? be good to compare that as well

 

Not really.
Price wont really matter.
The ET combo would acturally have to be the 255 heads as the 265 dont work as well with a fast intake, or stock valvetrain LS1 parts.
The LS7 combo would bo for those with large bore motor's and the ETP's would be for the 408 cubic inc crowd.
They wouldn't compete against eachother as far as setup goes so price wouldn't really matter.
Either way I am 99% sure the LS7 combo would destroy the Fast combo and mainly because the LS7 intake is much better.

 

I agree. 290 cfm is the most you can flow out of a Fast intake, whereas stock LS7 intake can flow 330 cfm

 

Quick question guys. Most heads are flowed without an intake right? If so that would mean that ls7 heads/intake flow pretty damn well together.

 

You are damn right about that Adams.
The LS7 combo flows better them most LSx style heads without the intake.