1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Question about huge BP's

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Old 08-28-08, 03:25 PM
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Thanks

Thanks to DivinDriver for the link. Looks like a great read. In the parent directory there are some FSM's too. Excellent resource!
Old 08-30-08, 09:07 AM
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Found some info that might help

Racing Beat says on the sheet that goes out with the template

drill holes at 15º angle and chain them to make the bridge

cut the housings 1/4" extra from the top and bottom of the bridge

5/32" into the rotor housing chrome surface
Old 08-30-08, 10:46 AM
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Originally Posted by -xlr8planet-
Found some info that might help

Racing Beat says on the sheet that goes out with the template

drill holes at 15º angle and chain them to make the bridge

cut the housings 1/4" extra from the top and bottom of the bridge

5/32" into the rotor housing chrome surface
Thanks for that I always wondered why the bridge on the housing was longer than teh bridge on the iron.

I did some port sketching last night. Not going to bother uploading the pictures again, but here is the direct link:

https://www.rx7club.com/showpost.php...postcount=2833
Old 08-30-08, 12:16 PM
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Originally Posted by M4st3r0fn0n3
Thanks to DivinDriver for the link. Looks like a great read. In the parent directory there are some FSM's too. Excellent resource!
That's Sgt Fox's manuals archive, mentioned in the FAQ. Credit to him for all that work. I just happened to remember the Downing book was there, and talked about bridge ports, s'all.
Old 08-30-08, 03:38 PM
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So I got these templates here. First is a little smaller than the next.


As you can see, the seal is still intact.

But as for this one:



Zuh? I wonder how people got around this? What do you do with the seal in this situation?
Old 08-30-08, 03:40 PM
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I like the 2nd one, because it leaves more support for the corner seal, but I fear it may move the powerband higher than needed. The upper port looks healthy.

Also, does it seem like the top port closes later than the bottom?
Old 08-30-08, 03:42 PM
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Lay the larger template over the smaller one, then lay each one over an iron. The first one looks about the size that I used on my 1/2bp.
Old 08-30-08, 04:02 PM
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Alright, hold on.
Old 08-30-08, 04:06 PM
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Here ya go. Big over small over stock.

Old 08-30-08, 04:07 PM
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The big bridge looks to have the bridge open before the port, where as the smaller port seems to open the port and bridge at the same time.

EDIT: Open earlier as the rotor tip, not a straight line. Also I know the big bridge works and has been used before, but the whole coolant thing has me mystified.

Last edited by Jeezus; 08-30-08 at 04:09 PM. Reason: Info
Old 08-30-08, 09:25 PM
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The small one is for a bridgeport that retains the whole coolant seal

the other looks more for a Jport....

here, Ive been working with the small one

I started today. I gave it about 4 hours of work
No work on the bowl or manifold side port ... yet

Im using a dremmel and a small carbide bit. Its all I was able to find




ok, here we go


and this is as far as I was able to go today

Old 08-30-08, 09:45 PM
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Ah, one question. I see the stock port, and the inside, do I also grind on the inside or do I just "flare" out from the stock port? MSPaint in a second..
Old 08-30-08, 09:50 PM
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So I can just port it like this? Sorry if I am asking a lot of questions, or really stupid questions. I just want to make sure I don't hit any water passages or end up making a hole.

Oh, and thats not a j bridge... I will show you a J-bridge
Old 08-30-08, 09:54 PM
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Mmmm... J port....

Thats a nice porting job there! I guess I am making it out harder than it is?
Old 08-30-08, 10:12 PM
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Originally Posted by Jeezus
Ah, one question. I see the stock port, and the inside, do I also grind on the inside or do I just "flare" out from the stock port? MSPaint in a second..
My limited english skills are not letting me undestand what you are trying to tell me...
Old 08-30-08, 10:18 PM
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The red being if I lay the dremel down at an angle to the bottom of the stock port, to the top of the bridge port boundary.
Old 08-31-08, 12:49 AM
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My best suggestion is to read through the Engine Building and Porting section over at NoPistons.com. They have a group of very serious and knowledgeable builders over there that make most of us look like first graders. I read through that entire sub-forum before I even bought porting tools, templates or a rebuild kit.
Old 08-31-08, 11:06 AM
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Originally Posted by trochoid
My best suggestion is to read through the Engine Building and Porting section over at NoPistons.com. They have a group of very serious and knowledgeable builders over there that make most of us look like first graders. I read through that entire sub-forum before I even bought porting tools, templates or a rebuild kit.
+1

I read the whole thing twice, and I still cant understand how to modify the bowl properly.

I dont have the tools to grind at an angle, thats a problem too
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