All Big Six Powered by Cadillac airbox mod

Relates to all big sixes

Dipstik86

Well-known member
I do have a brand new Hedman header I got from an estate sale that I wanna sell but if it doesn't I may install it in place of my efi manifolds and see what that gives me
 

Frank

Famous Member
Supporter 2022
Supporter 2021
The qft is night and day better than the worn out edelbrock. It's a mechanical secondary as well but this one allows me to get a stable idle. Didn't notice any fuel economy drop or power loss either. The air box is now routed to cold air via the rad cradle rectangular opening kinda behind the headlight bezel and what a different that made!! Runs way better when it's over 40° ambient and gets better mileage and doesn't vapor lock on the highway when I go fishing anymore like it use to with the open air filter element.
I got ya! All the reports on here indicate that QF is a good carb, and very tunable. Does it bog if you open the secondaries quickly with the mechanical? . . .
Cold air intake is extremely beneficial - the density loss is 1% for every 5* F temperature increase. I consider them a must in my southern climate. Consider: under-hood air at 130* vs ambient air at 70* = 12% density difference. If metering is correct, a 160 hp 300 engine will gain 19 hp with the fresh air. Plus the benefit of keeping the carb and fuel cooler. And it's quieter. There is a low temperature limit, and that is when a factory snorkel with the hot air stove and modulating valve is ideal IMO.
 

Dipstik86

Well-known member
Nope it doesn't bog at all. I have the 40% secondary actuation arm on it now but may try the 60% and see what that does
 
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