FYI: Cold Air Induction System on 1973

[Don Mason]

Hey Guys, thought some of you might be interested in what I found out this week. I have been working on the cold air induction system on my '73. All of this system had been removed by a previous owner for reasons known only to him. I found the cold air door and related hardware for the hood at a swap meet, including the wiring harness. The activation switch which is under the dash and works off the accelerator had also been removed from the car. Several sources told me that "The General" had quit making that particular part years ago. Some sources even gave me a part number(3986863). Just for the fun of it I checked with a friend in the parts department at my local Chevrolet dealer. Sure enough, the part was discontinued under that number, but he did some research and found that the part is still available from GM under a new number.(1242101). I got the part and it is a direct replacement, works like a charm. Best part of all, the cost was $22.00 as compared to the $75.00 a restoration parts house wanted for a used "vintage" replacement. Just goes to show you, sometimes the best deal may still be at the dealership.

 

[JOE BYRNE]

Does it make a difference Don?

 

[Tom73]

Way to go Don

 

[JOE BYRNE]

Tom...your the 73 guy....will hooking the cold air induction maks a difference? The other owner did the same thing with mine. The flap is gone although the wiring is still there. It has not been a priority but was just wondering about it.

 

[Vettehead Mikey]

Does it make a difference Don?

Makes no difference any '73 owner could prove to me or himself. More of a wizzbang marketing feature than a genuine performance item.

The basic concept has the fatal flaw of not blocking off the underhood inlets while the cold air passage is open, hence no 'ram' effect.

 

[Mac]

There is a difference, Mikey. The motor sounds a bit louder due to the unshielded path for noise. :L

Performance difference? None. Does this mean cold air induction makes my 73 like a ricer? :eek

-Mac

 

[waterboy1976]

Makes no difference any '73 owner could prove to me or himself. More of a wizzbang marketing feature than a genuine performance item.

The basic concept has the fatal flaw of not blocking off the underhood inlets while the cold air passage is open, hence no 'ram' effect.

It was not supposed to introduce a "ram" effect. The door was supposed to use the low pressure area create at the base of the windshield to introduce cooler denser air into the air cleaner. Instead of having the air come up throught the radiator hence warming it up and then into the induction. Thats why they had the air cleaner sealed to the hood to prevent warm air from entering. You all probably knew that but i just had a few minutes to waste.....

 

[Vettehead Mikey]

There is a difference, Mikey. The motor sounds a bit louder due to the unshielded path for noise. :L

You're right, I forgot that part. I usually make my own varooom VAROOM sounds out the window to help the car go faster, and forgot that the cold air induction does it for me

 

[Don Mason]

Hey Guys, I had no idea that a $22.00 switch would create so much discussion. Short answer to one question. HECK NO!! doesn't make a bit of difference in performance, probably never did just a whis-bang doo-dad. The car is really a nice old car and I just want everything to work like it should whether it really does anything or not.
One additional thing i did learn about the switch. The same switch was used into the mid 80s on GM pickups with electronic automatic transmissions. The switch was used as a kick-down for the passing gear. It is located in the same place under the dash at the top of the accelerator. That might be some useful information for those of you that like to go "parts diving" at the local salvage yard. Thanks again guys for the feed-back

 

[Vettehead Mikey]

It was not supposed to introduce a "ram" effect. The door was supposed to use the low pressure area create at the base of the windshield to introduce cooler denser air into the air cleaner. Instead of having the air come up throught the radiator hence warming it up and then into the induction. Thats why they had the air cleaner sealed to the hood to prevent warm air from entering. You all probably knew that but i just had a few minutes to waste.....

Ya, except that there's two big openings in the lower part of the air cleaner assembly that face forward into the hot airstream coming from the radiator and engine compartment........

The flow from these two openings far exceeds that which might come through the wimpy hood opening. Look at the cross sectional area where the hood opening joins the air cleaner.

Another 'flaw' in the design is that the high pressure (not low pressure) area at the base of the windshield also vents down the sides of the cowl through the leaf screens. The air will always take the path of least (leaf?) resistance.

As Mac points out, it sures makes nice QJet honk noises when you get on it though!

 

[Tom73]

Okay, let me jump in here with my two cents worth

Yes, it does make a difference in HP. The cold air induction that was introduced with the '73 is one of the main reasons that the 73 L82 is only 5 HP off of the LT1 of the year before and the 73 LS4 has 5 MORE HP than the LS5 of the year before.

You also need to keep in mind that the cold air induction was never intended to provide all the air that the engine would need at WOT. The hood passage through the hood is not large enough to provide that amount of air. So it still has to draw some air from the engine compartment through the base snorkles. Just that the external air helps cool the underhood air. And cooler air makes more HP.

And it worked. But why was it dropped in '76? By then the Vette had become a cruser rather than a performance car. That cold air induction was LOUD. So it was dropped to keep the sound level in the interior at a lower level.

As I said, just my two cents.

One additional thing i did learn about the switch. The same switch was used into the mid 80s on GM pickups with electronic automatic transmissions. The switch was used as a kick-down for the passing gear. It is located in the same place under the dash at the top of the accelerator.

It is also the kickdown switch for the Vette automatic. The TH400's used the electronic kickdown system while the later TH350's used a manual system connected to the throttle linkage.

tom...

 

[Vettehead Mikey]

Yes, it does make a difference in HP. The cold air induction that was introduced with the '73 is one of the main reasons that the 73 L82 is only 5 HP off of the LT1 of the year before and the 73 LS4 has 5 MORE HP than the LS5 of the year before.

If true, a '73 with a non-functional cold air induction system would be slower on the strip/street, and there would be reports of owners who noticed a difference after fixing it.

I've driven mine in both conditons and cannot tell the difference except for noise.

 

[crause]

All of the parts are still on my 75 but it does not work. How do I go about checking the system?

Andy

 

[steelblue75]

All of the parts are still on my 75 but it does not work. How do I go about checking the system?

Andy

Trace the wires down to the front of the hood area where they conect and check there for power, you should have 12volts at w o t, if you have voltage but can't hear the flapper door snap open, remove the assembly from the base of the hood, check the selinoid for corrosion, clean it up, thats all it took to get mine to work. Hope this helps you