GM 243 Head Max Ported Intake Flow
GM 243 Head Max Ported Intake Flow What kind of intake flow are people getting out of max ported GM 243 heads with oversized valves? I have to use the GM 243 head for the class I want to run.
On The Tree
Joined: Mar 2020
Posts: 168
Likes: 110
From: Weatherford TX
318cfm @ .600" with a 228cc Intake Runner
226cfm @ .600" with a 82cc Exhaust
3.900" plate with 2.040" Intake 1.575" Exhaust
This is using a SF-1020 Flowbench, most using a SF-600 will show about 10-15cfm more.
226cfm @ .600" with a 82cc Exhaust
3.900" plate with 2.040" Intake 1.575" Exhaust
This is using a SF-1020 Flowbench, most using a SF-600 will show about 10-15cfm more.
301CFM @ .600
233CFM @ .600 (W/PIPE)
3.900 PLATE with stock valves (2.00/1.55)
I did these myself, I did not cc them.
the reason the exhaust flowed so much is because I modified the shape of the valves. Minimal material was taken from the ports. I'll cc them next time the engine is apart, but the ports are still very small and the engine is very torquey still.
WHOOPS. I noticed now the original post said oversize vales and max ported. thats what i get for quick reading.
233CFM @ .600 (W/PIPE)
3.900 PLATE with stock valves (2.00/1.55)
I did these myself, I did not cc them.
the reason the exhaust flowed so much is because I modified the shape of the valves. Minimal material was taken from the ports. I'll cc them next time the engine is apart, but the ports are still very small and the engine is very torquey still.
WHOOPS. I noticed now the original post said oversize vales and max ported. thats what i get for quick reading.
Last edited by Kfxguy; Sep 9, 2020 at 11:21 AM.
TECH Senior Member
Joined: Jun 2016
Posts: 22,303
Likes: 3,619
From: Central Cal.
301CFM @ .600
233CFM @ .600 (W/PIPE)
3.900 PLATE with stock valves (2.00/1.55)
I did these myself, I did not cc them.
the reason the exhaust flowed so much is because I modified the shape of the valves. Minimal material was taken from the ports. I'll cc them next time the engine is apart, but the ports are still very small and the engine is very torquey still.
WHOOPS. I noticed now the original post said oversize vales and max ported. thats what i get for quick reading.
233CFM @ .600 (W/PIPE)
3.900 PLATE with stock valves (2.00/1.55)
I did these myself, I did not cc them.
the reason the exhaust flowed so much is because I modified the shape of the valves. Minimal material was taken from the ports. I'll cc them next time the engine is apart, but the ports are still very small and the engine is very torquey still.
WHOOPS. I noticed now the original post said oversize vales and max ported. thats what i get for quick reading.
TECH Addict
Joined: Jul 2013
Posts: 2,189
Likes: 123
From: Portland, Oregon
301CFM @ .600
233CFM @ .600 (W/PIPE)
3.900 PLATE with stock valves (2.00/1.55)
I did these myself, I did not cc them.
the reason the exhaust flowed so much is because I modified the shape of the valves. Minimal material was taken from the ports. I'll cc them next time the engine is apart, but the ports are still very small and the engine is very torquey still.
WHOOPS. I noticed now the original post said oversize vales and max ported. thats what i get for quick reading.
233CFM @ .600 (W/PIPE)
3.900 PLATE with stock valves (2.00/1.55)
I did these myself, I did not cc them.
the reason the exhaust flowed so much is because I modified the shape of the valves. Minimal material was taken from the ports. I'll cc them next time the engine is apart, but the ports are still very small and the engine is very torquey still.
WHOOPS. I noticed now the original post said oversize vales and max ported. thats what i get for quick reading.
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TECH Addict
Joined: Sep 2010
Posts: 2,898
Likes: 467
Their stage 2 program is excellent.
Actually, they would have been perfect for my old ls2 408 stroker.
When looking at flow numbers, especially peak flow numbers remember that's only one factor to consider of many. Looking at?thr mid lift numbers .400 to .500 are also very important.
Example - I had a set of old GMPP LS6's cleaned up in the chambers and given a new valve job. Lost 1 cfm of flow from 303 cfm to 302 cfm at .600 but they gained. ~ +10 cfm in?the mid lift numbers.
TECH Senior Member
Joined: Jul 2009
Posts: 8,034
Likes: 663
I agree. I got a set for a future engine build too. I wanted to do a ls3 stroker though. A 402/408 or a 416 would be a great street stroker with TEA 243 stg 2 porting and a 102/102 FAST setup IMHO.
Saw a chart saying 336 cfm at .700" with a 2.055" valve in a cathedral port head.
Have a 317 head I'm going to port to see what I can get out of it with an oversized valve.
Have a 317 head I'm going to port to see what I can get out of it with an oversized valve.
TECH Apprentice
Joined: Apr 2019
Posts: 365
Likes: 133
From: California
To get a set of 243 heads to flow you need to work on the throat, bowl/pocket porting, and pinch points like the rocker stud boss, and pushrod pinch point. The only thing I didn't touch on my 243s is the pushrod pinch point.
TECH Addict
Joined: Sep 2010
Posts: 2,898
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243 heads also seem to gain a lot in flow compared to other heads when ported.
Is it because they were underdone from the factory?
A gain of nearly 100cfm from stock to a tea stage 2 program is a huge improvement.
Is it because they were underdone from the factory?
A gain of nearly 100cfm from stock to a tea stage 2 program is a huge improvement.
TECH Fanatic
Joined: Jan 2017
Posts: 1,758
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Everyone keep in mind raw flow numbers do not indicate a good head that makes power. It's all about airspeed and the fine details the porter takes to shape the port in such a way that can maximize both flow and speed. You can have a high cfm head that doesnt make power and a head with less cfm that makes great power.
Everyone keep in mind raw flow numbers do not indicate a good head that makes power. It's all about airspeed and the fine details the porter takes to shape the port in such a way that can maximize both flow and speed. You can have a high cfm head that doesnt make power and a head with less cfm that makes great power.
TECH Senior Member
Joined: Jul 2009
Posts: 8,034
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