NA 20B ITB intake manifold worth saving? Pics
 

This manifold came with a 20B I purchased. Obviously it wont work as is, but I was wondering if its salvageable with a 90 degree bend added, or if I should have a new one made. Basically wondering if it will be worth the additional cost to start from scratch to eliminate the sharp bend that will have to be added. You guys have any ideas. Thanks, Mike

I would definitely chuck the LIM and build it from scratch. Use a nice constant radius bend with a couple inches of straight tubing leading into the intake ports. The bend on that LIM has the air nosediving into the bottom of the intake ports rather than flop straight in.

IMHO, i'd try it out before just chucking it, it doesn't look THAT bad, and it depends on your time frame/budget. does it not work as it due to hood clearance? you could just get shorter stacks you know... that.s what i would do, and then see how it performs.

compare it to the stock 20b LIM and if it's not any worse then the stock, it will be fine, plenty of people make great power on the stock LIM.

i think that IS the stock cosmo LIM...

I would save it, I don't think the sharp bend is going to make a drastic change if your not going too wild with your porting. I'm not sure what the specs of your 20B are.

The runners are slightly on the short side for a streetport/small bridge.

It is strikingly similar, but it lacks the indented runners. I do not believe it is the stock manifold.
It is cool. I would sell it and build something to suit your own needs. You'd have to fabricate something to use it anyways, might as well fab the whole thing right.

Just use it. It looks complete, so get the car running sooner rather than later. If it doesn't meet your expectations, modify it or make your own.

Keep it mate !! the manifold might be short but the stacks make up for the length anyway , people use the stock 20B intake with good results so this will work better anyway, dont worry that much about sharp angles they are not that bad it will still flow a good amount.
As a comparison a few years ago we tested an IDA manifold with nice curved runners on 50mm throttle bodies and on the same street ported 13b 4 port motor an IDF manifold with 90 degree runners ( and I mean proper right angles ) on 50mm throttle bodies and to our surprise it made the same HP , torque was up a little bit , so our conclusion was that the size/length off the runners/throttle bodies might affect HP/TQ more than the right angles/sharp angles on the intake manifold.

If hood clearance is a concern, you can make a new set of stacks that bend over the motor with the length you want.

Kinda like Xtreme Rotaries' setup
http://img520.imageshack.us/img520/176/imgp2826fj2.jpg


You can make it work..... i would

Not to hijack, but what throttle bodies are those?

Kinsler

I'm going to tackle this project so I may ask some rudimentary questions. Hopefully you guys will bear with me as I figure this out...

Currently I'm thinking of having a 3/4 inch flange made which will have secondary butterflies right next to the block to prevent overlap from the half bridge at idle/ cruise. GATO has the flange in stock, and I'll get Kinsler to make the throttle plates/ linkages/ ext...

- Should I crush the aluminum tubes to make them oblong, or port a block of aluminum so that it has the rectangular rotary ports on one side transitioning to circles on the other? I'll need a second flange anyways since I will not be welding on the flange with the throttle bodies.
- What size pipes should I use for the primaries/ secondaries?
- The 20B intake ports are at a slight angle. Is it worth the hassle to have the flange machined to at the same angle to eliminate the step/ slight airflow disturbance?
- Should I have an actuator open the secondaries at a specified RPM/ throttle percentage, or use a mechanical non linear throttle linkage to control them (http://www.kinsler.com/images/NewPro...e_Animated.gif).
- Do you think the secondary butterflies will hinder airflow significantly?

Backwards. You WANT to idle/cruise on the bridged ports. What kills the idle and drivability is the vacuum in the port pulling exhaust gases up into the port where it can dilute the air going into the engine. The higher the exhaust pressure, the lower the intake manifold pressure (meaning the higher the vacuum), the more exhaust gases gets pulled up and the worse it runs. If you put a butterfly to close off the runner, you will be maximizing the vacuum, making it worse not better. If you put the butterflies in the primary ports, you would force all airflow through the bridged ports, cutting down on vacuum in the port so the engine will run smoothly.

On my half bridge FC engines (stock intake setups), I did everything I could to idle on the secondaries. I made an extended secondary stop screw and minimized airflow through the primary blade, adjusting idle by opening the secondaries. I had to move the brake booster hose to the primary side of the intake plenum because there wasn't enough vacuum on the secondaries to work power brakes. Pretty much the only air going to the primaries at idle was coming through the fuel injector air bleed system. The car had drivability almost like a stockport.

My current engine is a full bridge, and I modified my Holley throttle body so there was no primary/secondary action, just for this reason. What causes the bucking is not airflow through the bridge, what causes it is LACK OF airflow.

with my P port, i ended up drilling a couple of holes in the throttle plate, and it did the same thing, less intake vacuum = less exhaust gas being pulled up = better drivability.

i can get it to idle without brapping even, although thats boring

Looks like you guys just saved me from going down the wrong path. Thanks!

Could someone help with the following questions?

- What size pipes should I use for the primaries/ secondaries?
- The 20B intake ports are at a slight angle. Is it worth the hassle to have the flange machined to at the same angle to eliminate the step/ slight airflow disturbance?

Thanks again,
Mike