Porting a Dorman LS6 reproduction intake
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From: PNW
Porting a Dorman LS6 reproduction intake This feature is on every runner - which leads me to believe it was put there for a reason, whether it's to create swirl or turbulence or basically something that I should just leave alone. Thoughts?
looks like the ones in a Fast intake, I'm sure it's there to increase air velocity but Fast intakes work better and make more power ported which involves smoothing that back and creating a straight runner wall
I knew the Dorman had a fast lower shell but didn't realize they also had copied some of the runner.
I knew the Dorman had a fast lower shell but didn't realize they also had copied some of the runner.
My Dorman LS6 had those as well. I figured since it was cheap enough and I had some time I couldn't hurt it too much with a home port job. I cleaned up all the runners while smoothing everything out and knocking off the excess "glue" where the upper and lower were stuck together. I also opened up the snout a little bit. I used a Dremel with the sandpaper cartridges and also a pointed stone bit for some of the deeper stuff. Cant tell you if it made a difference and it does take some time to do.
Do you think a metal file would work? My FAST 90mm shows up today, but I don't have a Dremel yet. I saw a video on YouTube where a guy was porting a FAST intake with a metal file.
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On The Tree
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I think this Dorman have potential over LS6 manifold easily. Quality of this product is poor out of the box.
Fitting of upper and lower half is not in line and you can port it too. There is also extra humps inside the runners (Cyl 1,2 7,8) cause of bolt holes.
You can port them but be careful theres going to come visible some orange gasket material between the halfs but its okay, just dont be so greedy there when porting.
I wonder often why people here think LS6 intake is 78mm? It is 75mm like all LS1 intakes and throttlebodys.
Dorman intake is 73mm and its badly offset when you look at it with bolted 75mm throttle body, so here is lot of restriction too of you dont take care of it.
Fitting of upper and lower half is not in line and you can port it too. There is also extra humps inside the runners (Cyl 1,2 7,8) cause of bolt holes.
You can port them but be careful theres going to come visible some orange gasket material between the halfs but its okay, just dont be so greedy there when porting.
I wonder often why people here think LS6 intake is 78mm? It is 75mm like all LS1 intakes and throttlebodys.
Dorman intake is 73mm and its badly offset when you look at it with bolted 75mm throttle body, so here is lot of restriction too of you dont take care of it.
. Modding cars is how we roll. 
Well I not trying to discourage anyone from porting these but . But lets keep any expected gains realistic .If you'r going to run stock oem heads behind this , smoothing out that runner wall is not going to gain you much. But if your talking aftermarket or a CNC head with a port width of 1.10 - 1.12 then you may see more . Without opening up intake you can only go up about 3" . The snout can lip is 73 mm and can be increased close to 78 mm but no more in order to maintain the o ring seal. Out of the box Im guessing these flow somewhere between 240 - 250 cfm . So if you can improve it by 5 cfm you are doing great. But double digit plus gains are not going to happen imo. I would like to see one of these opened up , to see if there is any real potential to improve it.
On The Tree
Joined: Feb 2011
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omc8 is totally right about this. If you are budgetbuilder and do all your stuff by yourself like i do, including porting an longtubes etc. i prefer this cause its cheaper than used LS6 intake and it looks like it have better flowing capabilities too over LS6. No science behind me but hope someone prove it someday even with mildly built street engine like many of us here like to build.
I have mine opened up to a true 78-9 on my calipers. The exit into the plenum is bigger I am sure. I will measure it to be positive. I am thinking of eliminating the o ring and using a cheap 80-85 tb from summit or whoever with gaskets. Going to measure runners and see exactly how big they are and where and see if it can't be pulled down into the head port. Their seems to be some room for porting, and if you break through just plastic solder it up....
Im not sure what you mean by non Dorman LS6 . We talking about the Dorman LS6 615-900 ...... unless you saying someone has knock it off . Has he opened it up separated the upper shell from the lower ?