1975 Cowl Induction

[Vetman]

Cooler intake air makes more power due to higher density and more oxygen to boost the bang. The 73 to 75 C3 cars used a hood cowl induction system to access cooler air but the system was compromised by underhood intakes and a flap to block external air except at wide open throttle, WOT. The flap often fails to open over time due to solenoid failure or poor adjustment of the throttle peddle switch. I removed my cowl flap, rubber seal and solenoid some years ago to let more cold air in or hot air out. My car no longer had the original air cleaner and rubber seal to the underside of the hood and instead had a 14” round chrome air cleaner. This looks good but draws in hot air from the engine bay.

I have now made my own intake surround based on an Edelbrock 1002 air cleaner as shown in the attached photo. I wanted to keep the bling but also to use the cowl system without pulling in any hot air from the radiator and engine. This is working well and measurements of intake air temperature compared to surrounding temperature indicate a 20 deg C reduction during fast runs. This equates to about a 4% power increase and a great sound. This difference may increase for summer temperatures and headers.

Any comments?

 

[Daytona Vette]

Looks good
As the intake appears well protected from consuming grit etc., could you not, now use a wider gauze mesh on the Filter to allow even more air in ?

 

[Vetman]

Looks good
As the intake appears well protected from consuming grit etc., could you not, now use a wider gauze mesh on the Filter to allow even more air in ?

The mesh is better than suggested by the previous photo see photo below.

 

[Daytona Vette]

The mesh is better than suggested by the previous photo see photo below.

Yes enlarge the image and the mesh looks good - should be a good setup

Many moons ago, I put some Ram Stacks on my twin SUs on an MGB, I covered the orifices with some steel mesh held in place with jubilee clips and then realised that I had reduced the intake area by about 40%, so the Ram Stacks came off.
My C3 Vette originally had an ex-Hollywood Marine big block out of a power boat, It would only run good with the bonnet off - It was a truck block with a higher deck and the Vette had a normal rise bonnet and consequently only a small pancake filter - so now a high output crate big block with a high rise bonnet and normal pancake filter, plus extra ducts to feed the cold air in and the hot air out.

 

[Roscobbc]

Get shot of the triangular air filter - or at least the foam filtering medium. These have a reputation for soaking up petrol from the occasional spit-back. When you get the next spit-back the element can catch fire with an obvious result....

 

[Vetman]

Get shot of the triangular air filter - or at least the foam filtering medium. These have a reputation for soaking up petrol from the occasional spit-back. When you get the next spit-back the element can catch fire with an obvious result....

Thanks for the fire concern you raise. I will consider this for a future revision. I would be reluctant to simply remove the foam. I was aware of the issue but wondered if this was due to overdue washing of the foam filter and a longer term build up of flammable deposits.

 

[Forrest Gump]

Looks like a nice solution. I've been thinking on and off for years about how to do something like you've done.
Theres a long thread on the US forum where the guy has made a duct that takes air from the gap between the top of the radiator and the rad frame, leading to an enclosure around entire 14" air filter. It becomes quite a dominant feature of the whole engine bay that I don't like.
I've read that about those triangular foam filters, but hard to believe Edelbrock haven't by now addressed that problem if it was a known design risk?

 

[Vetman]

Looks like a nice solution. I've been thinking on and off for years about how to do something like you've done.
Theres a long thread on the US forum where the guy has made a duct that takes air from the gap between the top of the radiator and the rad frame, leading to an enclosure around entire 14" air filter. It becomes quite a dominant feature of the whole engine bay that I don't like.
I've read that about those triangular foam filters, but hard to believe Edelbrock haven't by now addressed that problem if it was a known design risk?

Thanks for the response. Not only Edelbrock but many others supply the triangular foam air filter so probably low risk but better to avoid the risk. I will try a 10” circular air filter instead.

I have seen photos of home made cold air intakes without the hood cowl intake and the ducting runs forward to above the radiator. This is a longer route which probably negates any ram air benefit at legal speeds and may suffer some heating of the air between radiator and carburettor.

I will post again if I change the filter.

 

[Roscobbc]

Thanks for the response. Not only Edelbrock but many others supply the triangular foam air filter so probably low risk but better to avoid the risk. I will try a 10” circular air filter instead.

I have seen photos of home made cold air intakes without the hood cowl intake and the ducting runs forward to above the radiator. This is a longer route which probably negates any ram air benefit at legal speeds and may suffer some heating of the air between radiator and carburettor.

I will post again if I change the filter.

Perhaps the inclusion in your designs of a K & N filter top would be an alternative answer to a filter medium.

 

[Vetman]

Perhaps the inclusion in your designs of a K & N filter top would be an alternative answer to a filter medium.

I have now modified the cold air induction to use an Edelbrock Pro Flo circular air filter. Took the car for a run today and was pleased with the performance and saw up to 23 deg C cold air benefit. I will St ick with this for now and re-assess when I fit headers next year. I did not see an open top K&N that would fit my enclosure. Also could these be set alight by a flaming backfire. Any instances reported?

Photo of the new arrangement attached and also the temperature gauge I use.