500, 472, 425, 368 Discussion, Open element air cleaner in Cadillac Engine Technical Discussion; I've been reading through this forum trying to absorb some knowledge to prepare me for tuning up my newly acquired ...
I've been reading through this forum trying to absorb some knowledge to prepare me for tuning up my newly acquired 1975 DeVille. I have seen many references to installing an open element air cleaner as a quick and easy way to get a little performance increase. It make complete sense and would also get rid of some of the clutter under the hood. Couple of questions. I ordered a Mr Gasket 14" open element kit. There's no way it will fit. I don't know why I didn't see the obvious that the stock air cleaner housing is offset to clear the a/c compressor. I see Edelbrock makes a 10" x 2" unit that should fit. Is that a large enough element? Second question. Can I just eliminate that thermac sensor in the stock housing and plug the vacuum line? It seems that the only thing it does is open and close the valve in the neck of the stock housing which will no longer come into play. Also, there is a breather thingy that goes into the stock housing from the valve cover. Can I just put a generic breather cap on the valve cover to fill the hole? Thanks.
Automobile(s): Cadillac 78 Seville, 78 Coupe de Ville, 92 Sedan de Ville
Re: Open element air cleaner
You can buy spacers to raise the air cleaner as long as you have the hood clearance. I think the performance gain is debatable but I usually put them on or just flip over the lid on the stock one. I never have put a chrome one on my Caddys though except my 350 Seville.
On my cars the lid is replaced with a lid from a diesel: 1" more height. The
hold down bolt will need some adjustment. On those with limited clearance,
I used a lower half from a Toronado, which sits lower on the Qjet. The oiled
element I use, claims when dirty to outflow a clean paper filter. Bruce Roe
I must say I'm surprised by these responses. I have spent several hours in the last couple of weeks reading this forum paying special attention to threads where guys like me are asking for advice on things they can do to right away to improve the performance of a 472/500 short of major modifications. The most common advice, it seems, is tuneup (plugs, wires, cap, rotor, curve kit, etc.) drain the cat, bigger exhaust and an open air filter. I have read several posts making the point that the stock air cleaner housing cannot possibly allow 700 to 800 cfm into the carb. So are you guys disagreeing with that or I am I misunderstanding what an open element air filter is? Appearance aside (I was thinking of using the black version of the one I linked to) is a 10" x 2" filter large enough to get the job done? And what about disabling the stuff that is connected to the stock housing?
Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
Re: Open element air cleaner
What you want is more torque, not horsepower. You only need to flow 700 cfm to the carb on wide open throttle for an extended distance. The distributor curve kit mod is worthwhile, it provides more low end torque. The best bang for the buck would be a lower rear axle ratio. Low restriction air filters on a street driven car IMO provide little more than a manly noise when leaving a stop sign. Drag race the same car, air filter on then off would net maybe a tenth better acceleration if that. Drag race the same car with a lower rear axle ratio and it will beat the other car. (to the gas station!) There's nothing wrong with disconnecting the breather system to the air filter as long as the new breather has a filter within it and is cleaned every once in a while.
It might do better with the new advance kit in the distributor, along with an adjustable vacuum advance canister, and maybe an advance limiter, like a Crane 99619-1, limiting vacuum advance for bumping the initial timing up to about 12 degrees, or more if it will not buck the starter.
Maybe the Sanderson headers will fit that car ?
I doubt that a hot rod style air cleaner would provide much gain on a street engine. I used to flip the lid on the '68 Sedan De Ville and that provided all the induction drama one could want under heavy acceleration and still remain low profile enough to not draw unwanted attention from the authorities. Recurving the ignition (or replacing with a VERY high discharge unit like an MSD) as well as a good carb tune ( or replacement with something more modern) would help too.
Someone mentioned a twin snorkel air cleaner. Some GM products had these and it might pay to do some research. Also, a freer flowing catalytic converter may help too.