After seeing predators on Bigfoot a long time ago, I now have a set on my ford coupe. I got them because a good friend of mine had a very bad experience with Holley, so he convinced my and a few other friends not to use their products any more. When I started seriously considering Predators, I looked around the internet, and found a lot of people commenting that predators **** for one reason or another, and won't work. I have had Holley vacuum secondary and double pumpers on about 10 hot rods in the past, but only one Q-Jet, and a couple old Autolite 4 barrels. Over the last few months I have learned a little about predators, some good, some bad. One of the biggest issues I had getting my predators to work right at light throttle tip in was the out the back fire flaps. The ones that Predator sells in their rebuild kit did not work for me at all, despite multiple adjustments, and more than 200 miles of street driving. Attached are a few photos of the problem I had with the predator flaps, and the solution suggested by of my friends. On more than one occasion I have been very close to throwing both of them in the garbage and getting a set of 800 cfm edelbrock's, but I stuck with them, and I am starting to get a handle on how to make them work. I plan on finding a ch***is dyno in Portland to see just how well they are working sometime this month. I tried several times to make the predator flaps work, but every time they curled up, exposing the slots in the upper air doors, when this happens, the carb goes very lean at light throttle, and will tend to die when starting out from a stop. After a while I gave up on the predator flaps, and made my own set from a pair of thin leather gloves. The leather gloves have worked great for over 100 miles of in town driving, and stay flat on air doors, keeping the slots sealed off. As soon as I changed the flaps, the engine started running richer at low throttle, so I ended up having to start over on adjusting the air door tension and mixture, but the end result is that it doesn't load up when idling in gear, and it has never backfired or popped back through the carb, even when I snap the throttle open from idle with the car in drive. The car has a TH400 with a stock stall speed converter and a 3.50 rear gear. The fuel economy isn't very good, but I will be working on that next by playing with the metering cams. Hope this helps anyone working on a Predator.
Keep updating this thread. I have always like those crbs, but they are so unconventional that they don't get the credit they deserve.
Note: not very good fuel economy = 7 mpg (city) 496" tall deck chevy, solid roller, 350 cc heads, 7.9 CR, 20% underdriven Bowers 8-71. Question: How do I find confirm/find a possible intake gasket leak on a blown big block? I can't get this thing to idle at less than 1200 rpm in neutral unless I retard the ignition timing a lot. The square double bottom air doors may not seal very well, and perhaps since I am running two carbs, it is just too much leaking to get the idle down any lower. The blade adjustment screw is backed out all the way on both carbs. Perhaps I just need to put in a bigger cam.
we used to have a predator on a pulling truck back 20 years ago, as i recall they come with 3 cams, one for non blown and one for blown and one for alcohol, i think there mostly ment for WOT. i dont recall ever haveing trouble.
Interesting. I have had one for years and haven't run it because I haven't got any idea how to tune it. Please keep posting your progress.
I am running #5 cams on my blower motor, but I think with 20% underdrive it is still fat, so I may change to #4.
If I could find a buddy of mine from high school he could tell you anything you wanted to know about them. He had a small motor mopar in a duster that had a pair of them sitting on a tunnel ram. That thing ran like a bat out of hell!!! He would not set the wheels down till 3rd gear and was running all motor. That was when they first came out in the early eighties i think.
they were out in the early 70s at least. i don't know **** about tem but i know Two Lane Blacktop came out in 71 and the 55 in that movie has a pair of them on a tunnel rammed 454 big block Chevy... i always thought they were cool looking carbs but since i don't like to tune "regular" carbs i have stayed away from them.
Predators are interesting carbs. I got to talk to a Predator Rep at Famoso one night. At the time Predator was based in Tulare, California not too far from Famoso. Tip-in backfire sounds like you're way lean and have figured that out pretty well. At one time, I believe Predator made a carb with a low end accellerator pump. If I'm remembering right, the standard Predator accell pump operated only at full throttle and was more for start-up than anything else. If there is such a thing as a low end accell pump for Predators I wonder if there's a source of supply where you could get a couple. Have you tried running the Predator as a single carb setup? I forget the flow ratings, but saw more than a few big-blocks running at the strip with a single one and doing ok. The engine cam you're running could be contributing to your lean backfire problem as well. Big cams equal low vacuum at low rpms.
Don't know if they are still around, but a company called Extreme Customs in Visalia, CA bought out all of the Tulare facility's inventory a few years ago. Carbs, parts, fixtures everything. Neat trick with the glove leather. I've never run my Predator, but I loaned it to a student who out it on a 347 in a 65 Mustang, and the difference between the Predator and the Holley was incredible. M***ive torque, but it was constantly needing adjustment.
i had em on a blown small blk ..to get the idle down you have to seal the big flaps they are alum so i had to peen them with a hammer to get the to seal if you hold carb up to light source you can see they dont seal off so its like the throttle is open takes a lot of patience and dont loc***e the screws untill your finished,,, i got 12-15 miles gal.
I tried them back in the late 70's. Even had help from the Predator people trying to get them to work on a very stout 331" SBC. Eventually the guy from Predator gave up trying to help and said "they were never made for the street anyway" They went on a dragster after that.
aren't carbs supposed to "****"? i alwaya thought of the Kendig as a big Fish style carb, with a vacuum diaphragm to maintain a constant depression. (think SU)
Interesting, I have noticed that both the upper and lower doors don't really seal that well, leaving lots of room for air to get past. Sounds like that is the next step. Side note: Amazing amount of thermal growth in this engine, the blower belt goes from being way loose with the engine cold, to snug with the engine warmed up.
For anyone considering trying out a predator. If you don't have the small predator manual, you should probably get it, but in case you are frugal, here it the basic way to tune one up. First, the adjustment of the bottom doors is not as critical as on a holley. The typical ebay or craigslist $100 carb does not have the "street idle circuit". On the "standard" version the lower air doors are not directly connected to the fuel supply at idle and does not have any idle orifice or transfer slot like a holley. On my car the bottom air doors don't make a very tight seal, and since I have two carbs, the total air getting past the doors is enough to keep the engine running, even with the throttle stops backed off completely. The vast majority of the tuning is done with the screw in the top of the carb. This screw raises and lowers a fuel block inside the float bowl, this block controls all of the fuel delivered to engine (other than the accelerator pump) and is VERY sensitive. With less than 3 rotations you can go from too lean to run to blowing black smoke all the time. The thread pitch on this screw is very fine, so your not moving the block up and down very much at all to make big changes in idle fuel. WARNING: Don't try to screw the screw on top in or out very far, it has a ball end that is stuck inside the plastic fuel block, and if you turn the screw too much it will break the plastic housing. (I found this out the hard way) Take the float cover off and remove the float if you want to see how it works. The easiest way I found to set up my carbs was using a cheap dial caliper to measure the depth of the screw head from the top of the carb body (not the air cleaner adapter). For mine, the engine seems to like the screws set at about .250" (1/4"). Note that this adjustment is only really controlling fuel mixture from idle up to about 1/8 throttle, if your idles ok, but is rich or lean at WOT, then you need to look at the spring tension on the air doors or change the cam inside the float bowl(s).
Exactly. Of course, many people think that Holley is cutting edge, the best 1950's technology that money can buy.
Worked great on my 64 chevy ran them for about 2 years till i sold the car.That 454 ran real good with them.
The Jalopy Journal
