I am just built a 276 CID 1950 Merc, .375 lift Potvin cam, Johnson Lifters, Edlebrock heads,Offenhauser 3/2 Stromberg 97/Joe Hunt MSD Mag,balanced,Red's headers. I'm running one carb during break in and when I put on a True Helmet air cleaner, the RPM's dropped 400 and the motor flattened out at 2900. Removing the air cleaner the RPM's went up 400 and the motor could hit 5000 with no hesitation. I bought the air cleaner from Speedway Motors. Has anyone experienced this problem with this type of filter, or used another vendor's without problems? Any help will be appreciated. Don Buck
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I ran my 354 hemi with four Strombergs for a few years with just small scoops & screens . Ran perfect . Then I put four on my 354 hemi , with k&n filters. Engine wound't rev above 3k. Took the filters completey out ,put the tops back on. Same thing would not rev above 3k. Car runs just fine with small scoops & screens. I think the helmets restrict alot of air. Plus the hemi needs alot of air.
This is not a new problem. Most of us rarely run up the RPMs and never notice the restriction. The small aftermarket air cleaners have been notorious for restricting air for 30 years now. They work reasonably well on the street for keeping out bugs and other big trash. Take them off when racing.
Do your initial tuning and test running with no cleaners...then if anything changes when you put them back on, you know your cleaner is a restriction. This is more than a performance issue, restricted air cleaner causes rich running and rapid piston ring failure! Quite possibly even worse mechanically than running with no cleaner... Aesthetically, I don't know an answer. Air cleaners that look right on vintage rods are generally corks. Big OEM quality paper air cleaners from '60's and '70's cars are for all practical purposes non restrictive (until they **** up 20,000 miles of dirt) but how to package them on an olde car??
Thanks for all the response, we ran the motor on a bench for 1 1/2 hrs 20 minutes at a time. After 3 sessions re torqued the heads and manifold. When I installed the motor in the ch***is, started it up with out an air filter all was good. As soon as I put on the filter the motor dropped 400 rpm. I agree the filters are like a cork. I'll try the K&N and see what happens. I can put the Bug Dome back in and run scoops if necessary. All help is appreciated, Don
I personally wouldn't run no air filters on an engine I cared about lasing for a long time. Effective air cleaners will be a bit bulky at best and more likely not exactly traditional looking. Restrictive air cleaners do more than chop top end, they **** up part throttle carburetor fuel/ air metering. In the past I gutted the typical oil bath filters and fitted a K&N type inside without too much trouble. A good paper filter is said to be a better dirt catcher and not less restrictive than oil wetted gauge types....
I have cut slots in some and covered them with a small nylon stocking. Seems to help. I recommend the scoops and bug screens..... The only large diameter filter that would look good is one from a 3x2 Ford FE , with a custom housing.
I am going to be a bit of a devil's advocate here. Yes, an air cleaner will keep the dirt out. But today cars are seldom driven in a harsh environment (esp. our hot rods). Back in the 50's and earlier half the country roads were dirt. I think in today's would there would be very little difference either way. And yes I run an air cleaner. I have run my car on occasion without and the comments were endless about the damage I was doing.
As a motorcycle rider (with my face in the wind) I wouldn't want half the **** that hits my face to be ****ed into my carburetor.
Air cleaners are a necessity IMHO, even without dirt roads, and most older engines could use better filters at places like crankcase venting too. The problem is that many of the proper aesthetic choices are junk...so build and tune without the things, then put them on. If running and/or plug color change rethink what you are running on top! I think that it is quite possible that the enrichment caused by bad little filters could kill an engine (especially rings) faster than dirt would do the job. Once you have filters that work, keep after things. A good quality small filter might do the job, but it is going to clog up and kill your engine quickly simply because it has so little area.
Out here 3/4 of the roads are still dirt. I drive 4 miles of them just to get to pavement. K&N sez one square inch for 6 CFM so a 4x2 which is more like a 4X1.5 after the ends and the glue would flow about 110 CFM.
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