Port Molds

Have an interesting technique, tool or just anything related to porting? Post it here . . . please no bashing anyone for the model of engine they are working, we're here to share ideas . . .

Postby Spike_TD » Sun Feb 15, 2004 11:34 pm

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Postby willeng » Mon Feb 16, 2004 12:06 am

rtv silicone is suitable for port moulding.

There are many books available on this subject, The chevrolet racing engine by Bill Jenkins, shows some & it's a good read to.
This will help!
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Postby rx7carl » Mon Feb 16, 2004 11:43 am

I wish I could post a picture here. I tried to just pour in the rtv. But it wont cure in the center because its not exposed to the air. What did work very well for me is this. I blocked one end of the port with a piece of sheetmetal. Then I sprayed a mold release compound into the port, covering all the walls. Then put in some rtv and smeared it around to create a "skin" inside the port, then let dry overnight. Then each day I repeated the process to build it up so it had some strength and would hold its shape. I built up layers till it felt fairly thick, but the center remained hollow. This greatly helped in the removal process as I could collapse it a bit to get it out without damage.
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Postby SWB » Mon Feb 16, 2004 1:00 pm

You can get silicone or latex molding materials from either Bill Mitchell or Cylinder Head Abrasives, both are on-line. Chicago latex is another manufacturer who makes this material. I have not ever seen cheap molding material. I've heard of people filling the ports with an expanding foam like they make Nerf toys out of (foot balls etc.) but I don't know where to get that? The advantage to the foam is that it's super quick to cure, where as the latex or silicone materials usually take 12-24 hours.

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Postby Spike_TD » Mon Feb 16, 2004 4:40 pm

[color=#000000]I was thinking of doing exactly the same thing rx7carl. The TDI ports have a protrusion that blocks almost half of the port right before the valve guide. Getting a solid mold out wouldn
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Postby rx7carl » Mon Feb 16, 2004 5:27 pm

Its a PTFE based release agent/dry film lubricant. Stuff is slicker than snot. I got lucky using the hollow method. Such a complex shape would have never come out in one piece if I made it solid. But it holds its shape beautifully, and can be filled if necessary for more rigidity.
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Postby 98-1074649673 » Mon Feb 16, 2004 6:11 pm

Alcohol and vaseline mix the two together and use a small acid brush to coat the area with the mixture. The alcohol will evaporate and leave a thin coat of vaseline. Your port mold will slip right out. Well thats what I've been told anyhow, haven't had time to actually make any port molds yet . . .

Postby Greg » Tue Feb 17, 2004 6:39 am

I was looking around on the net to find what people are using to make port moulds and read about a product called Blu-Sil molding rubber. you can get it from:
Perma-Flex Mold Co.
1919 East Livingston Ave.
Columbus, OH 43209.
apparently US$125 a gallon but that was a couple of years ago.
here is a LINK TO THE ARTICLE that I read it in. Its about making "Flow Boxes", basically a clear plastic version on a chamber and its ports that you can port, cut valve seats on and flow test. It's a brilliant idea, once I get my bench made I am going to do some playing with them. It would be nice to be able to throw it in the serdi and cut a seat, flow it, then build it back up again and try another tip profile to see what difference angles/radiuses/seat widths make to airflow.
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Postby willeng » Tue Feb 17, 2004 6:56 am

Makes elastosil---It's great, contact them with your application & they will fix you up with the supplier & the right gear.
Sometimes RTV won't set due to the catalyst not being stirred through enough---mix measured, directed amounts & stir well.
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Postby Unkl Ian » Sat Aug 13, 2005 5:36 pm

Found this on www.eng-tips.com ,
in the Automotive-Engine and Fuel Engineering forum,
talking about port areas and velocity:

"get some two part pour-able rubber low durrometer (12-15) from Walco" www.walcomaterials.com
The author recommended "GE-25" .
Unkl Ian
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