Megiddo Posted July 16, 2022 Share Posted July 16, 2022 I found this air cleaner on a Bronco at the junk yard I looks like it has a vacuum operated door on the back inside that "scoop", but the vacuum motor doesn't work. Is that door supposed to open at low vacuum (WOT) for extra airflow? If so, does anyone know where to find a new vacuum motor? Link to comment Share on other sites More sharing options...
Gary Lewis Posted July 16, 2022 Share Posted July 16, 2022 I think that is an air cleaner off a 460 as they had a back door like that. But I don't know for sure as I don't have one of those air cleaners. Perhaps someone that does can confirm. Anyway, I can't find in the master parts catalog a number for that vacuum motor. However, there is probably a number on it, so if you drill the rivets and pull it out I'll bet we can figure it out. Link to comment Share on other sites More sharing options...
85lebaront2 Posted July 16, 2022 Share Posted July 16, 2022 I think that is an air cleaner off a 460 as they had a back door like that. But I don't know for sure as I don't have one of those air cleaners. Perhaps someone that does can confirm. Anyway, I can't find in the master parts catalog a number for that vacuum motor. However, there is probably a number on it, so if you drill the rivets and pull it out I'll bet we can figure it out. Gary, Jim has Darth's old air cleaner so he should have a picture. Here is what it looked like installed: The heated air motor is closer to the main body on Darth's, maybe it was for a 351 HO model. Link to comment Share on other sites More sharing options...
Rusty_S85 Posted July 16, 2022 Share Posted July 16, 2022 I think that is an air cleaner off a 460 as they had a back door like that. But I don't know for sure as I don't have one of those air cleaners. Perhaps someone that does can confirm. Anyway, I can't find in the master parts catalog a number for that vacuum motor. However, there is probably a number on it, so if you drill the rivets and pull it out I'll bet we can figure it out. Ive seen that aircleaner listed on ebay as a 351HO and a 460 aircleaner. I dont know what it came on but I believe that vacuum closes the door because every photo Ive seen on ebay shows the door wide open without vacuum. I suspect with manifold vacuum it closes and only opens up under heavy load acceleration to allow for more air to be pulled in. Link to comment Share on other sites More sharing options...
Gary Lewis Posted July 16, 2022 Share Posted July 16, 2022 I think that is an air cleaner off a 460 as they had a back door like that. But I don't know for sure as I don't have one of those air cleaners. Perhaps someone that does can confirm. Anyway, I can't find in the master parts catalog a number for that vacuum motor. However, there is probably a number on it, so if you drill the rivets and pull it out I'll bet we can figure it out. Ive seen that aircleaner listed on ebay as a 351HO and a 460 aircleaner. I dont know what it came on but I believe that vacuum closes the door because every photo Ive seen on ebay shows the door wide open without vacuum. I suspect with manifold vacuum it closes and only opens up under heavy load acceleration to allow for more air to be pulled in. The 351HO base is different from the 460 base as the 351HO didn't have the opening on the back. And yes, vacuum closes the opening and it pops open below some value that the 460 apparently goes below at WOT. Link to comment Share on other sites More sharing options...
Rusty_S85 Posted July 16, 2022 Share Posted July 16, 2022 The 351HO base is different from the 460 base as the 351HO didn't have the opening on the back. And yes, vacuum closes the opening and it pops open below some value that the 460 apparently goes below at WOT. Thats what I figure but I know a lot of junkyards on fb list that style air cleaner as coming off a 351 truck and they call it a 351HO air cleaner. I personally wouldnt use it as I would want the air to be cool air out from under the hood and that duct on the back side negates the purpose. Might as well run a open element air cleaner if you are going to have that. I myself am still looking at air cleaners but probably will just use silver solder and fix the split aluminum base of my original one and restore it and just use it. I cant justify spending $250+ for a used OE air cleaner Link to comment Share on other sites More sharing options...
Megiddo Posted July 17, 2022 Author Share Posted July 17, 2022 The 351HO base is different from the 460 base as the 351HO didn't have the opening on the back. And yes, vacuum closes the opening and it pops open below some value that the 460 apparently goes below at WOT. Thats what I figure but I know a lot of junkyards on fb list that style air cleaner as coming off a 351 truck and they call it a 351HO air cleaner. I personally wouldnt use it as I would want the air to be cool air out from under the hood and that duct on the back side negates the purpose. Might as well run a open element air cleaner if you are going to have that. I myself am still looking at air cleaners but probably will just use silver solder and fix the split aluminum base of my original one and restore it and just use it. I cant justify spending $250+ for a used OE air cleaner I think, if the vacuum motor was working, that door and the hot air would only come in at or near WOT. So would more warm air be better than less cool air? Does a 351 need more airflow than can come through the snorkel at full throttle? I rarely see anything over 4000 rpm. I guess the limiting factor on air for the motor is the carb. I have a plain 4 barrel Holley at 600cfm. I know the stock 2v carb was something like 480 cfm. I'm not sure what you big motor guys have, but I don't think I've seen a truck with a double snorkel cleaner. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted July 17, 2022 Share Posted July 17, 2022 I hadn't been able to find a vacuum motor. Fortunately Bill Vose offered me his housing when he switched Darth over to EFI. The engine vacuum travels through a green modulator which was located in that indexed hole in the foreground of your photo. This keeps the door from snapping open (or shut) if someone takes a stab at the gas pedal. I now have a 750cfm carb but vacuum secondaries keep manifold vacuum levels reasonable. I'm not sure how much vacuum is required to overcome the spring inside the unit. I wouldn't recommend a mechanical secondary carb on something as heavy as a pickup. Link to comment Share on other sites More sharing options...
Gary Lewis Posted July 17, 2022 Share Posted July 17, 2022 I think, if the vacuum motor was working, that door and the hot air would only come in at or near WOT. So would more warm air be better than less cool air? Does a 351 need more airflow than can come through the snorkel at full throttle? I rarely see anything over 4000 rpm. I guess the limiting factor on air for the motor is the carb. I have a plain 4 barrel Holley at 600cfm. I know the stock 2v carb was something like 480 cfm. I'm not sure what you big motor guys have, but I don't think I've seen a truck with a double snorkel cleaner. I think more warm air is better than less cold air, and apparently Ford did as well since they put that air cleaner on the 460's. But be careful of comparing 2bbl vs 4bbl carbs via the CFM ratings. The two carbs were flow tested at two different vacuum ratings, as explained on this page, and quoted here. Or, read a different explanation at The Carburetor Shop. The cubic free per minute, CFM, rating for 2 BBL and 4 BBL carburetors can not be directly compared. 2 BBL carburetors (and 1 BBLs) are tested with a 3 inch vacuum while 4 BBLS are tested with a 1.5 inch vacuum. .... If you want to compare the CFM rating of a 2 BBL to that of a 4 BBL multiply the 2 BBL rating by 0.707. And Wikipedia says the 2150's used on the 351's in these trucks were rated at, oddly enough, 351 CFM. Multiplied by .707 that says those carbs compare to a 248 CFM 4bbl. Link to comment Share on other sites More sharing options...
Gary Lewis Posted July 17, 2022 Share Posted July 17, 2022 I think, if the vacuum motor was working, that door and the hot air would only come in at or near WOT. So would more warm air be better than less cool air? Does a 351 need more airflow than can come through the snorkel at full throttle? I rarely see anything over 4000 rpm. I guess the limiting factor on air for the motor is the carb. I have a plain 4 barrel Holley at 600cfm. I know the stock 2v carb was something like 480 cfm. I'm not sure what you big motor guys have, but I don't think I've seen a truck with a double snorkel cleaner. Oh, I forgot the dual-snorkel bit. I pretty sure that no truck came with one, although a few of us have created them. I used a 351HO air cleaner, which has a larger steel base than the aluminum ones most trucks got, and grafted on a 2nd snorkel. But others have adopted the dual-snorkel air cleaner from an HO Mustang. Rick/Lariat 85 explained what he did in a series of posts here. Link to comment Share on other sites More sharing options...
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