ultimatejay

iTrader: (1)

What year center plate iron is in this pic? I am trying to get an intake manifold gasket and having a hard time finding one to match with the large primary oval ports and the EGR hole. BTW- it's a 12a, Thanks

ultimatejay

iTrader: (1)

Damn, forgot the pic.------

Rogue_Wulff

The center ports of the intake are smaller than on the iron. This is by design.
Use a 81-85 12A gasket. It will have the bottom EGR port in it, even you are using an aftermarket intake that blocks it off.

ultimatejay

iTrader: (1)

Thanks, I know about the intake manifold ports being smaller. I'm going to port those out to match the ports in the pic. So 81-85 12a's had the larger primary ports in the irons?

Rogue_Wulff

Porting the intake is not a good idea, from what I've read. It kills the power under about 4-5K.

The irons all had about the same size ports. What intake are you using?

ultimatejay

iTrader: (1)

The engine has a large bridgeport on it and the guy that I bought if from slapped this unported intake manifold from Australia on it to get it running. As you can see from these pics the ports in the intake manifold are way smaller than the ports on the irons. This would cause a major restriction and basically would take alot of power away from the bridge and that is why I am going to match port the intake manifold. In the second pic I put a gasket that has about the same size primary intake ports as the irons. See how much I need to port?

vipernicus42

iTrader: (4)

Read #1 in bold in the link below... then go back and read the entire page from top to bottom. Then don't port your intake manifold that way. There are other, better spots to port the manifold.

http://www.yawpower.com/Flow%20Testing.html

Jon

ultimatejay

iTrader: (1)

In the above link that you provided they are talking about a stock 12a manifold. This is not a stock manifold and the motor is not stock. This motor has a large bridgeport and that is why I am porting the intake. So your saying that guys that are building 800+ horsepower rotories are running stock intake manifold ports? I don't think so. Maybe if this was a stock engine with stock exhaust and stock carb, etc then match porting would cause a loss of power.

Rogue_Wulff

If it is a BP engine, you're not gonna have much low end anyways. I don't know if port matching the intake will adversely affect the power up high, or help it.

But, I still reccomend the 81-85 gasket. Just trim it to match the intake, when you are done opening it up. The early gaskets do not have the lower exhaust passage, and can cause an exhaust leak if you have 81-85 housings.

Latin270

Some guys have experimented w/port matching and seem to like there results. Paul Yaw has done his bench flow tests and all but I talked to a guy at the pan-ams that didnt buy into that theory. Quote " Paul doesnt build drag cars" . This guy did have a 9 sec car to back up what he was explaining to me.

ultimatejay

iTrader: (1)

I'm with you. Every drag racer or race engine builder I ever talked too, piston or rotory, have match ported the intake manifold to heads- runners and they usually port the heck out of the intake manifold runners as well.

I'm just going to match port the openings and do very little manifold runner porting. This motor should be a screamer.

Jeff20B

iTrader: (13)

Y casting. That port below the intermediate ports is what I call the ACV port. There is no EGR.

If your manifold is stock, DO NOT touch the runners. If the manifold is aftermarket, you could probably port match them, but I'd leave a little 1 or 2mm lip all the way around in the aluminum to help fight reversion.

Those are some awesome tips I just gave you. Ask anyone who knows anything about port flow on a rotary, like Carl, and he'll tell you the same (probably more eloquantly though, lol).

ultimatejay

iTrader: (1)

Thanks for the tips, I'll try it.

ultimatejay

iTrader: (1)

Just finished match porting the intake manifold. I did not go to crazy and left 1mm lip like you said. Here are some pics. Let me know what you think.

Thanks,

jarrett

Rogue_Wulff

Before you install the manifold, go to parts store and get a couple 20mm freeze plugs to go in the housings. Dorman part number 555-101.
Doing that will prevent those pesky water jacket o-rings from leaking. Also allows the intake to be pulled off without losing any coolant.

Jeff20B

iTrader: (13)

That'll probably work quite well. You should see my friend's IDA manifold from Rotary Engineering. It was already matched with a 1 or 2mm lip when new. I didn't have to touch it. Really the only thing that needed match porting was the gasket. I'll deal with pictures later today so you can see what I'm talking about.

ultimatejay

iTrader: (1)

Thanks, I would like to see those pics.

Rogue wulff- thanks for the freeze plug tip. That is a great idea. Why didn't I think of that? So easy.

Rogue_Wulff

You did. Right after I told ya the size/part number.....LOL

Jeff20B

iTrader: (13)

Rotary Engineering IDA manifold.

Rogue_Wulff

Oh, I would still advise using the 81-85 intake gasket, just in case there is exhaust present at the port under the primaries.
Intake looks good, to me. I also like the looks of that RE intake......

Jeff20B

iTrader: (13)

We chose to use a '74-'75 gasket because it is the same as '81-'85 even though the rotor housings have thermal reactor ports. This means the intermediate plate will not have exhaust gasses wanting to leak out of the ACV port... unless there is some leakage which there could very well be with old used housings. At least the chrome looks good.

ultimatejay

iTrader: (1)

Thanks, the gasket that is in the pic is not the one I am going to use. I just had that one lying around and used to match port the intake holes. I am going to use the 84-88 like you mentioned.

Jeff, I really like that RE intake. How does it perform?

Siraniko

iTrader: (13)

just get that 12-A bridge running period. then if you need more, bring it to me and I will tune in provided that you bring me cold heine's. Just dont ***** out at top end.

ultimatejay

iTrader: (1)

LOL. Thanks Mel. I am sure I'll be giving you- the weber carb tune master,a call when I get it running. Just got done re-painting the hiddiest orange to gloss black on the engine. Rene just called me and told me my new alluminum radiator should be here tomorrow. And this weekend I am making some solid motor mounts. So by next weekend or earlier I should have this baby running- brap brap brap, gottta love those bridgeports!