Which IDF manifold is better.

[ward00]

Getting ready to start putting pieces together for a 2 liter overbore build for a 124 Coupe. The question I have is what dual IDF manifold is best. I have seen the ones that people call waffles. The one I currently have on my spider has individual runners that look like the one at the link.

https://www.ebay.com/itm/FIAT-124-134-I ... :rk:1:pf:0

I recently took my IDFs off my spider which has the individual runner type of manifold and boy what a mismatch in size of the manifold openings to the carb throats above. I would have thought that it would be much closer. Is it that the manifold was not specifically made for IDFs (is so then I understand)? In any case its a real good candidate for porting.

But back to my question, what type of dual IDF manifold should I start off with (any one have experience with the one at the link). Is there a benefit of the waffle over the runner type.

I don't mind porting it (like will be done on my Spider), but is there a "best" IDF manifold?

And if anyone has one, want to sell it?

[ward00]

So it looks like the intake manifold at the link in my previous post and the manifold on Spider is made by Pierce. Any idea why they don't port the intake opening to at least match the diameter of the throats of the 40 IDF. Looking down my IDF's you can see a portion of the intake manifold sticking out and blocking air flow (at the maximum its about 1/8 of an inch). Wonder how much horsepower this is costing and how much it affects jetting. Very tempted to take the manifold off and grind away the obstruction.

[fiatfactory]

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[ChrisSRT]

I have a waffle manifold I'd be willing to part with as well as some valve train parts.

[AndyVAS]

Almost all manifolds are cast with "extra" material. It is expected that they will be ported by the end user. Look at larger production items such as an intake for a SBC or SBF. Several places offer CNC machined versions to correct this.

To answer your question about the best... well... they are equal. As cast, there are definitely some differences and a flow bench will show it. Should you develop a CNC program for these, I would be shocked if it resulted in differences between brands of manifold. Some of the manifolds would have 1mm removed to get the CNC port and others 1.5mm or 2mm or 3mm. But at the end they would all be enlarged to the same finished size.

So pull off your intake. Trace out the gaskets on the flanges. Get to work grinding.