Not to start another world-famous Corral.net intake pissing match, but here goes.
I have a Weber IDF manifold that I want to mate up to some TFS 11R 205 heads. The heads have the 1262R port, 2.25" x 1.40". This intake's port is...a bit smaller than that.
The carb side of the intake has ports 1.877" in diameter that taper down right away.
The head side of the intake has 1.82" x 1.03" ports. That's way smaller than even a 1250.
So obviously getting the intake anywhere close to the head port size will require quite a bit of hogging out.
So if I open up the carb side of the intake to its full 1.877", that's an area of 2.77 in2. If I open up the head side of the intake to a 1262R, that's roughtly 3.45 in2. Which makes me think I'm going to have a bit of reverse taper as the area of the carb side opens up to the area of the head side. Then the head intake port tapers down to the valve, giving me a kind of double-cone runner with a possible dead zone halfway through where I lose velocity.
Here's my caveat - this isn't a race engine. It doesn't need to be competitive in any class, spec, or specific scenario. These are the parts I want to use. I acknowledge that it would make way more power with a Super Vic and a carb on top, but that's not what I'm going for.
With that being said, when I go to match everything up, what should I shoot for as far as port shape and size to minimize any unwanted characteristics?
just slap it together and run it... smaller intake ports is ok to run on a larger head.... it's not a racecar as you said.. for the trouble of porting it to get it to it's full potential it's just not worth it.. it will be fine as is.
No expert here, but I haven't seen many experts suggest porting to the opening in the head. The opening in the head is smaller than a 1262R anyway (as you noted) and you would never want to port to a gasket as the spacing between ports makes it unlikely for a perfect match. I got mine close using a gasket and noting these offsets when transferring the measurements to the intake minus about 0.02" all around so the intake port will always have some adjustment room. When I got it close, I used a borescope turned backward to visualize the match and tweak it from there. Also, if the port will need to remain smaller to keep a taper, these same experts claim that you want the roof of the port to match first, followed by the side with the highest velocity if it's curved (like a Supervic is on the outer ports.) I'm sure someone will correct me here if I got this wrong.
You can see that it was difficult for me to match radii perfectly, not that it matters much. I went ~3" into the port to keep the taper smooth. Likely b--rad's advice is fine in your case, however.
Thanks for all of the discussion so far. I've seen lots of people say that it's fine for the intake to open up into the head port, you just don't want to go the other way.
Thanks for all of the discussion so far. I've seen lots of people say that it's fine for the intake to open up into the head port, you just don't want to go the other way.
I think if you took the valve out and measured every half inch you'd find that the smallest part of the port is at the pushrod pinch. They're actually bigger at the turn to slow the air down so it'll turn down into the cylinder.
I would open the the top to the true 1.877 dimension. If you port the runner exit to 1.200"x2.00" (2.4 sqin) you will have an equivalent circle size of 1.70" which gives you some taper. You could go to the 1.28"x2.10" (2.688 sqin) runner exit and have an equivalent circle size of 1.81" which would be no taper. I would not match the intake to the head port size. My notes have the CNC 205 head pinch at 2.479sqin so a 1250 size runner exit is essentially the same size as the pinch and gives some taper to the runner. Your choice......... I gotta go take a piss.......
Is there a steel-core version of the 1262R? I'm running the 1262S3 on my 302 because everyone hates the non-steel Print-O-Seals. Does the 1262R have an equivalent steel core version?
I would open the the top to the true 1.877 dimension. If you port the runner exit to 1.200"x2.00" (2.4 sqin) you will have an equivalent circle size of 1.70" which gives you some taper. You could go to the 1.28"x2.10" (2.688 sqin) runner exit and have an equivalent circle size of 1.81" which would be no taper. I would not match the intake to the head port size. My notes have the CNC 205 head pinch at 2.479sqin so a 1250 size runner exit is essentially the same size as the pinch and gives some taper to the runner. Your choice......... I gotta go take a piss.......
So you want the outlet of the intake to be close to the size of the pinch point of the head's runners. What is the best taper, is the same for EFI or carb, and is it measured as a size per inch change?
Would you know if that CNC 205 head notes you have would be the same for a 170TW with a CNC 205 program run in it? I'm doing a TFS R lower with no upper, just a plenum, housing an intercooler.
Different intakes present different challenges, for this one I feel one of those two options will work best. The pinch point varies with 11R model, and if you have a cnc program run, you will have to ask the shop if they get into changing the pinch area.
Different intakes present different challenges, for this one I feel one of those two options will work best. The pinch point varies with 11R model, and if you have a cnc program run, you will have to ask the shop if they get into changing the pinch area.
I'm planning to use the injectors on the throttle bodies, which should point straight at the intake port. We'll see how good the line-of-sight to the valve is.
I'm planning to use the injectors on the throttle bodies, which should point straight at the intake port. We'll see how good the line-of-sight to the valve is.
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