Intake port/manifold mismatch.

[Roger 911]

I have 30mm intake ports on my 2.4T heads. I am using Webers with manifolds that are 32mm at the head. I have E cams in the motor. It would seem that I should at least chamfer the intake port to remove the step from 32mm down to 30mm. I do not want to disassemble the engine and formally port the heads. However, I am thinking about removing the motor, putting it on an engine stand, turning it 90 deg, stuffing a plug deep into the intake ports, and grinding the edge out to match the manifold, maybe a 1/2" down. I can vacuum any shavings out, then remove the plugs. I appreciate that I won't have a 32mm port, since it will still reduce in diameter as it goes into the head. However, removing the step would still seem to provide improvements in airflow. Make sense?

Thanks.
Roger

[Flat6pac]

If you had E heads, you would still have the same problem.
Bruce

[Eagledriver]

I have an easier way. Buy some plastic insulator gaskets from someone like PMO. They are about 5mm thick and you can taper them to remove the step.

-Andy

[Roger 911]

"If you had E heads, you would still have the same problem."

Are you sure? Every reference I have read shows E intake ports at 32mm (I know some books also erroneously show T ports at 32mm, but this is not correct). I know the base of the T MFI throttle bodies actually narrows to 29mm, so maybe you are referring to the diameter of the base of E throttle bodies? I have also read that there is potentially a benefit to having the port slightly wider than the manifold base.

"I have an easier way. Buy some plastic insulator gaskets from someone like PMO. They are about 5mm thick and you can taper them to remove the step."

I currently have a set of these, but they are about 35mm. I didn't realize they came in different sizes. I like this idea, if I could get a 30mm set.

[id911T]

Originally Posted by Roger 911

"......... E intake ports at 32mm (I know some books also erroneously show T ports at 32mm, but this is not correct).......................

This statement may be true for the 2.4T, but not all T engines in general. The 2.2T engine came with 32mm ports. It might be easier to find some 2.2T, E heads and just use those.

[Roger 911]

Originally Posted by id911T

This statement may be true for the 2.4T, but not all T engines in general. The 2.2T engine came with 32mm ports. It might be easier to find some 2.2T, E heads and just use those.

Yes, I am aware that 2.2T heads had larger ports. The whole point of my inquiry is to explore a solution that does not require disassembling the engine. Right now, the 30mm spacer seems to be the most appealing. I'll see if I can track this down.

[Henry Schmidt]

Just my $.02 but I doubt you will notice any difference without a complete port job.
Enjoy your car the way it is and address the issue on the next top end overhaul.
Cheers

[Roger 911]

Henry,

Do you think I should get plastic insulators/spacers that are 32mm to match the manifolds? Right now I have manifolds that are 32mm, then spacers at 35mm, then ports at 30mm. Intuitively, this expansion and contraction downstream of the carb seems bad. Wouldn't fuel have a tendancy to fall out of suspension in the 35mm "expansion ring"?

Thanks.
Roger

[Henry Schmidt]

Intuition gets us things like Dilivar studs and boat tailed cases. Thousands of dollars spent over decades to produce ridiculous studs and zero horse power increase.

That said, if you are going to replace the insulator blocks you might as well buy 30mm and put a taper in them to match the carbs as suggested by Andy.

As for "Wouldn't fuel have a tendancy to fall out of suspension in the 35mm "expansion ring"?: there is so much turbulence in an intake port that the fuel will have no trouble staying in suspension.
Cheers

[Roger 911]

Yes, the 30mm spacer seems to be the easiest approach. Any idea if they make 30mm spacers? So far, 32mm is the smallest I can find.

[Henry Schmidt]

Looked on my gasket board and the smallest I have is 33.5mm.
sorry

[bxd]

Roger, I don't know if this is still something you're searching for, but I just spoke to Chris at Turbo Kraft in AZ about this very same problem. He can make a custom set of insulator blocks that taper from and to whatever size you need. He quoted me $120 for the blocks themselves (no studs/bolts).

-Sounds like you already have a set of blocks, so you possibly won't need new studs/bolts. I think insulator blocks come in varying heights, so you might want to pull one off your car and measure it so they can match that height on your new set.

[Roger 911]

I may check this out. I assume they are plastic, so they still provide the thermal barrier?

I wound up ordering a new set of "stock" spacers from PMO a couple weeks ago, assuming they would be smaller than the 34/35mm ones I have. They were not. Apparently the spacers Porsche used on the 2.2T were actually wider than the 32mm ports on those engines. So, I still have this 32/34/30 intake diameter as I move from manifold, to spacer, to port. Maybe it doesn't matter, but it sure seems bad, on paper at least.

Originally Posted by bxd

Roger, I don't know if this is still something you're searching for, but I just spoke to Chris at Turbo Kraft in AZ about this very same problem. He can make a custom set of insulator blocks that taper from and to whatever size you need. He quoted me $120 for the blocks themselves (no studs/bolts).

-Sounds like you already have a set of blocks, so you possibly won't need new studs/bolts. I think insulator blocks come in varying heights, so you might want to pull one off your car and measure it so they can match that height on your new set.

[bxd]

Yes, the insulators from Turbo Kraft are made from the same phenolic material that the PMO blocks are; the guys at TK would be able to give you more detail on this than I can.

If I can offer my two cents on the stepping issue; I've discussed this on several occasions with my mechanic and this is what I've come to understand: -These small steps or variances between the carbs and the heads won't really be noticeable on a dyno. However, by smoothing out the flow, you may (as in maybe or maybe not) notice a slight difference in low-end torque vs. top-end speed (in my case I'd probably lose a minute bit of low-end grunt but gain a very slight bit of top-end speed). But for this to really be something you feel in your foot, the carbs must be in perfect working order, must be tuned correctly, with no air leaks or blockages, and all the gaskets must be air-tight. -And on the street, a slight bump in top-end speed is not really going to be usable anyway, right?

I guess the message here is that this is a system, with air/fuel mixture being of primary concern, and if the carbs aren't in good shape and setup correctly etc., then laminar flow or atomized fuel suspension, or even slight compression/expansion inside the manifold/port is probably not the primary issue. For my money, and since my car runs fairly well as-is, I decided not to get all tweaked over it and opted to address the stepping when I rebuild the carbs sometime in the future.

[Flat6pac]

I have a brand new set of 32s in the background if that would make it easier.
Bruce

[Roger 911]

Originally Posted by Flat6pac

I have a brand new set of 32s in the background if that would make it easier.
Bruce

Thanks, but at this point I think I'll either stick with the 34s I have, or maybe consider the machined 30s.

Roger