Intake manifold

dbs328 · Post by **dbs328** » Tue Jan 17, 2012 2:59 pm

Can some one give me the pro's and con's about puting a Dual-Plaine or Single-Plane intake on a 79 spider. Can you use either one?

katsi · Post by **katsi** » Tue Jan 17, 2012 3:33 pm

Depending on where you live, you may or may not be able to legally change the intake and carburator on 79. The biggest advantage to changing out the intake is getting rid of all the smog equipment. I said good bye to the technicolor intake a couple of years ago. It makes things much easier to maintain, gives you more power and really opens up the left side of the engine compartmebnt.

dbs328 · Post by **dbs328** » Tue Jan 17, 2012 3:43 pm

What kind of intake did you use?

Kent124 · Post by **Kent124** » Tue Jan 17, 2012 4:07 pm

79s came stock with a dual plane manifold. Those have two smaller holes that "match up" to the carb barrels (28mm & 32mm).

Single planes from a 1974-1978 will bolt up to a a 2L (stock 1979 engine). They have one large opening, as shown below. Single planes let more air into to the engine increasing horse power. The upgrade to a single plane intake is usually done in conjunction with installing a 4-2-1 exhaust on the car to take advantage of the increased air flow into the engine.

Installing a single plane requires removing emissions equipment that is on the stock dual plane manifold. If your area does emissions testing on cars you might be out of luck.

Kent124 · Post by **Kent124** » Tue Jan 17, 2012 4:09 pm

For the upgrade people also change out the carb to something like a 32/36 DFEV or 34 ADF.

If you are sticking with the stock carb you might as well stick with the stock (dual plane) manifold.

dbs328 · Post by **dbs328** » Tue Jan 17, 2012 4:18 pm

Can you tell me more about 4-2-1 exhaust ?

124JOE · Post by **124JOE** » Tue Jan 17, 2012 4:35 pm

early cars had a manifold that has 2 holes for exh into the down pipe witch joined into 1

some mid style had a manifold that has one pipe as the down

and later ones have 4-2-1 also

because they flow better

Kent124 · Post by **Kent124** » Tue Jan 17, 2012 4:48 pm

This is 1/2 of a 4-2-1 exhaust. It's called a 2-1 down pipe. They came on fuel injected (FI) spiders from 1980 forward. Some of the 1979s also had a 2-1 down pipe but they are not very common and had a special exhaust manifold that is difficult to find.

If you decide to go down the 4-2-1 exhaust route your best bet is to buy an exhaust manifold and down pipe off a FI spider.

katsi · Post by **katsi** » Tue Jan 17, 2012 5:05 pm

dbs328 wrote:What kind of intake did you use?

I used one from an earlier model (I think it was a 74) and went with the 34 ADF. Both of which I purchased off of ebay. The intake was 80.00 and the carb was 24.00

. I know, go figure.

Anyway, looks exactly like the one in the picture Kent 124 sent. Their are a few things to watch for when changing this out on a 79. You can look it up as their are lots of step by step instructions here on the forum. Just make sure to block off the extra exhaust tube. You will have to figure out how to plug the hole. I used a peice of sheet metal and just unbolted the extra tube and then put the peice of sheet metal behind it, then hit it with a little spray paint. It made a perfect template on the sheet metal. I then cut out the plug with a dremmel, drilled the holes and bolted it back on the block using the new plug as a sort of gasket (I used a little high temp silicone too).

To be honest, it's much more difficult sourcing the parts than actually swapping them out.

Unless, some nimrod bolted your intake on with the motor out of the car and didn't bother to think about which holes he used the studs and nuts and which holes he used the bolts on. I had to remove the master cilinder to get the intake off my first 79 because some jerk did that.

I remember that really sucking!

DocGraphics · Post by **DocGraphics** » Tue Jan 17, 2012 5:09 pm

Heres a pic of the older style one I have yet to install (off a 74 1800)
This shows the double holes coming out of the 4-2 manifold & into the double hole 2-1 down pipe, then to a single exhaust pipe, the 4 bolt is the early style (6 bolt on newer)
The stock manifold on my 78 is a 4 to 1, with just 1 hole in the bottom of the manifold that the exhaust pipe hooks to.

dbs328 · Post by **dbs328** » Tue Jan 17, 2012 5:20 pm

Thank's Every One for your help. I learn some thing every day about a Fiat

Kent124 · Post by **Kent124** » Tue Jan 17, 2012 5:22 pm

Katsi's let me know if you ever want to unload that ADF for $24

dbs328 · Post by **dbs328** » Tue Jan 17, 2012 5:29 pm

I have exhaust like the first picture but I have 4 holes not 6. Is that OK ?

dbs328 · Post by **dbs328** » Tue Jan 17, 2012 5:37 pm

Ok I will, Now I need a single-plane intake. Does any one have one?

Kent124 · Post by **Kent124** » Tue Jan 17, 2012 5:42 pm

If it is currently installed on the car you are good to go, for the most part.

Can you take pictures of your current intake manifold and post? Maybe someone already installed an 1800 intake on it (hope, hope).

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