Intake manifold for 219 head

[Eriks]

I'm putting a 219 head with Isky cam and dual sidedrafts on a L18. The 219 head has 1.50" intake ports, so I need to find a intake manifold that can match that size. I see Cannon manifolds for sale on Ebay but I read that they are only 1.25".

 

Any advice where to find a 1.50" intake manifold ? 

 

If you have one for sale let me know. Thanks :)

[datzenmike]

Just port match it with a carbide tip die grinder, hell I use an ordinary electric drill. Taper in for as far as you can reach.

[Eriks]

I see that is an option. However I'd like to see if there already is a finished product out there. E.g. I've read about Nismo manifolds.

[Z-train]

On a L-18,you should be considering port velocity more than you are. Mike's advice is appropriate for your app.

[Eriks]

What is a good port velocity? What is a bad port velocity? Please explain, thanks. 

[Z-train]

Port velocity is the speed at which the charge moves thru the manifold & ports.The smaller the port the faster the speed. Think of sucking thru a small(diameter) straw vs. a big one.Unless you're cammed & ported for high RPM operation,a "big" manifold runner could hurt you more than help.And if you follow Mike's intructions,you'll be fine.

[Eriks]

Thanks, I read that air speed must be at least above 200 feet/second to create a minimum of momentum. When knowing what engine I suppose it is fairly easy to calculate the maximum diameter on intake to acchieve this.

[banzai510(hainz)]

The Cannons it might be a little to thin if porting them out

The old nissanmotorsport and the Mikuni mans are 1.5 hole size

 

Since your in Norway check out Datsport in Australia. Barry(BAZ) might have soemthing

[Z-train]

Thanks, I read that air speed must be at least above 200 feet/second to create a minimum of momentum. When knowing what engine I suppose it is fairly easy to calculate the maximum diameter on intake to acchieve this.

All things are not equal. I have a 2.3 stroker that I am using a un-touched L-16 manifold on and I am make huge numbers down low(which was the plan).Depends where you want the power.

[Eriks]

Interesting. Now I just made some calculations: The L18 with a 1.25" intake must exceed 1600 rpms to gain 200feet/second airflow. With a 1.50" intake the rps has to exceed 2300, this if the air pressure in the cylinder is a perfect 1 bar the moment the intake valve closes. I suppose we can assume it will always be a little less, meaning that the rpm figures in reality will be slightly higher. 

 

Anyway you've made a good point for me considering what intake to choose. 

 

I just wonder, If I use a 1.25" manifold on a 219 head that has a 1.50" intake port, will not the airflow slow down again when entering the head and before arriving the cylinder?

[nad015]

I have just bought one of these

http://www.weberperformance.com.au/product_info.php?products_id=878

 

They are made by powerplay in Australia

Here's a link to the powerplay website http://www.powerplay.net.au, but they don't show the manifolds on their site.

They are $299 aud from powerplay.

And they can supply a high quality big port manifold gasket for $23 aud.

 

They are to suit 45mm dcoe carbs minimum.

 

And are 38mm port size at the head end.

 

This is what baz from datsport would recommend to you.

 

Also Stewart Wilkins Motorsport in sydney Australia casts his own manifolds aswell and are nissan Motorsport copies or something

But you would have to contact him to confirm

[datzenmike]

Interesting. Now I just made some calculations: The L18 with a 1.25" intake must exceed 1600 rpms to gain 200feet/second airflow. With a 1.50" intake the rps has to exceed 2300, this if the air pressure in the cylinder is a perfect 1 bar the moment the intake valve closes. I suppose we can assume it will always be a little less, meaning that the rpm figures in reality will be slightly higher. 

 

Anyway you've made a good point for me considering what intake to choose. 

 

I just wonder, If I use a 1.25" manifold on a 219 head that has a 1.50" intake port, will not the airflow slow down again when entering the head and before arriving the cylinder?

 

How did you calculate this? Would like to try on a manifold I'm going to make.

 

In theory when the piston reaches BDC the cylinder should be full and the valve should instantly shut to seal the air in. In the real world the intake stays open another  48 degrees on an L16????? Much longer on racing cams. This is because the air doesn't and can't stop moving instantly at BDC and continues flowing in from inertia. The higher the speed of the air the more that will continue flowing in. A small port at low RPMs or a larger port at ultra high RPMs can exceed normal air pressure in the cylinder if it is captured by closing the valve at the correct time. The engine does less work and actually over fills the cylinder... like having a turbo charger on it. Not a huge amount but it is free for the taking.

 

Port air speed must be maximized BUT the port must not be so small that it restricts air flow at higher RPMs. In this case the engine works even harder to get less air and power abruptly drops off.

[Eriks]

Well, I made a very simple calculation. First, the cc of the L18 engine is 1770. I multiplied that with 1000 rpm and divided everything by 60 seconds. That should give something close to the engines total air/gas consumption per second at 1000rpm, which is 29,5 liter. 

 

Secondly I calculated the volume of a 200 feet long 1.25" pipe, which is approx. 48 liter. 

Finally I calculated how much the rpm had to increase for the engine to consume 48 liter (1000 divided by 29.5, multiplied by 48) and the result was 1600 rpm. 

 

Of course in real life, as you mention yourself, there are many variables to consider, but I guess this little math exercise makes us closer to the answer. 

[Eriks]

I have just bought one of these

http://www.weberperformance.com.au/product_info.php?products_id=878

 

They are made by powerplay in Australia

Here's a link to the powerplay website http://www.powerplay.net.au, but they don't show the manifolds on their site.

They are $299 aud from powerplay.

And they can supply a high quality big port manifold gasket for $23 aud.

 

They are to suit 45mm dcoe carbs minimum.

 

And are 38mm port size at the head end.

 

This is what baz from datsport would recommend to you.

 

Also Stewart Wilkins Motorsport in sydney Australia casts his own manifolds aswell and are nissan Motorsport copies or something

But you would have to contact him to confirm

 

Thanks Mr. nad015 

[banzai510(hainz)]

those calculations hurt my head.

Make this Simple run, a 40mm sidedraft set for the street

 

theres a guy in England that has stuff also(cant think of the name but someone will chime in). maybe cheaper for you to get something from there.

 

 

I have a Cannon in my mess of junk stuff, but best to just run that on a 1.25 intake port head

[datzenmike]

Well, I made a very simple calculation. First, the cc of the L18 engine is 1770. I multiplied that with 1000 rpm and divided everything by 60 seconds. That should give something close to the engines total air/gas consumption per second at 1000rpm, which is 29,5 liter. 

 

Secondly I calculated the volume of a 200 feet long 1.25" pipe, which is approx. 48 liter. 

Finally I calculated how much the rpm had to increase for the engine to consume 48 liter (1000 divided by 29.5, multiplied by 48) and the result was 1600 rpm. 

 

Of course in real life, as you mention yourself, there are many variables to consider, but I guess this little math exercise makes us closer to the answer. 

 

Then lets refine this some more. The engine has to turn twice for every intake stroke so 1,000 RPMs is only 500 intake strokes.

 

At 1,000 RPMs 14.75 liters is flowed through the intake (total)

 

There are 4 ports so 14.75 L divided by 4 = 3.6875 L / second / per cylinder. Or 3.6875 L through each port.

 

 

I calculated a single cylinder volume of 442.38cc per cylinder or .44238 L X 500 divide by 60 = 3.6875 L / second / per cylinder.

 

 

Sound right? It's still 1,000 RPMs just less volume.

 

1.25" pipe is 31.75mm diameter which is 3.175 cm..  pi R squared is...  7.91 sq cm diameter.

 

100cm = 1 meter

1,000cm = 10  meters

10,000cm = 100 meters

100,000cm = 1 kilometer.

 

A kilometer long 1.25" wide pipe has 100,000 x 7.91 = 791,329 cc divide by 1,000 = 791.32 liters in it

 

@ 1,000 RPM it would take 215 seconds to use that volume up. 3.58 minutes. That's 16.74 kilometers per hour or 10.36 MPH or 15.24 feet per second

 

@ 6K this would be 62.37 MPH or 91.4 ft/sec.

 

 

............... Yeah, Ive missed something obvious and gone off the track. :lol: :lol:

[DanielC]

Another issue to consider.  the fuel that leaves the carb is not completely vaporized,  there are still droplets of liquid fuel, with the air.  If the velocity of the air is too slow, the liquid fuel tends to fall out odf suspension, and the engine runs lean, and excess fuel puddles in the intake manifold.

 

At BDC, the piston is really not moving that much, well at BDC, not moving at all.  10 to 20 degrees BBDC, to 10 to 20 degrees ABDC, the piston is not moving much.

 

Here read this.

http://www.datsport.com/racer-brown.html

[Eriks]

Thanks for correcting me. Of course on a four stroke the air consumption is half my estimate due to the engine turning twice for each intake stroke. 

 

And of course the air is not travellig through just one 1.25" barrel but four :) 

[datzenmike]

Absolutely. Maximum  piston speed is when the crank and the rod are at a right angle. Somewhere well above half way up the cylinder. Longer rods dwell longer at TDC and BDC than shorter ones

[datzenmike]

Thanks for correcting me. Of course on a four stroke the air consumption is half my estimate due to the engine turning twice for each intake stroke. 

 

And of course the air is not travellig through just one 1.25" barrel but four :)

 

We need to fine tune this. I think I'm off track. There must be a way to work out the air speed easier. If I remember I'll ask one of the engineers at work. 

[Eriks]

Another issue to consider.  the fuel that leaves the carb is not completely vaporized,  there are still droplets of liquid fuel, with the air.  If the velocity of the air is too slow, the liquid fuel tends to fall out odf suspension, and the engine runs lean, and excess fuel puddles in the intake manifold.

 

I believe that is the "secret" of the two barrel Offenhauser intakes, that they create a jet stream in the lower barrel that atomize the fuel mix. 

[RandyWanger]

 

theres a guy in England that has stuff also(cant think of the name but someone will chime in). maybe cheaper for you to get something from there.

 

Any idea who this guy is? I'm after an intake manifold/carbs for my L18. Thanks.

[banzai510(hainz)]

http://www.datman.co.uk/

[EricJB]

 Very few aftermarket parts are plug and play. Most can be improved for your needs. Even if you found a Manifold that was close, you're still are going want to gasket match it. I managed to get my Cannon intake ported for 48's on the carb side, and 1.625 on the head side without breaking through. It is thin in spots, but it works, and that just makes it lighter, right?

 

Dont make it bigger for an L18, just taper it to match the head. Smooth transition, Just as others have recommended.

 

 

 

 

 

[banzai510(hainz)]

Thats a Cannon?

Maybe you should fix mine up. I was going to sell it for 75$

but maybe I shold keep it