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500hptaylor

  • Karma: +0/-0
anybody running predator carbs?
« on: February 16, 2010, 03:37:02 PM »
I just bought a predator carb that I want to try out. Is anyone running these. It seems simple and great in theory but the only downside is that I have a vaccum advance dizzy. Not to keen on running manifold vac to the dizzy. Oh yeah its on a 454 with 650 ponies. The only reason Im going with the predator is so I can get my idle down a little more. I couldnt get it lower then 1100-1300 with my holley.

Let me know what you guys think,thanks
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IRRebel

  • Karma: +16/-0
Re: anybody running predator carbs?
« Reply #1 on: February 16, 2010, 05:32:20 PM »
Be cool to see you do it and the results!  :thumbup:

I asked the same question about six months ago, and while some had seen it done, noone on here had done it or heard of how well it worked or not. I have 2 Predators for a Blower idea I got in mind. (gets me in trouble every time......)

Check some of the Hot Rod sites, theres a lot of good info over there.

http://www.hotrodders.com/forum/predator-carb-v-s-holley-750-dyno-chart-92700-2.html

Thats one link. These guys didn't like it very well at all, lol.

On the street and on the water are two different things though. We are generally idling, cruising at half throttle or so, or WOT. Intermetiate settings are not really required.  ;D We go from an idle state to flat foot to get on plane and either stay there or back off the half or so to cruise.

Good luck! 

Ray
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"Life's journey is not to arrive at the grave safely in a well preserved body, but rather to skid in sideways totally worn out shouting 'Holy Shit what a ride!"---Crewcheif22 AKA Keith

GT Jets

  • Karma: +192/-0
Re: anybody running predator carbs?
« Reply #2 on: February 16, 2010, 05:59:03 PM »
Never had much love for the Predator or the vacuum dizzy..

Maybe just me...

You got nothing to lose.. :thumbup:

GT
  • Boat #1: 1992 Carrera 20.5 Elite (I/O bitches)
  • Boat #2: 19' Bubble deck Jet BBC Berkeley
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If i get some free time tonight at work, ill play with it and post it for everyone to see.

Time to man up and yank it John!  :banghead:
Ray

propless

  • Karma: +12/-0
Re: anybody running predator carbs?
« Reply #3 on: February 16, 2010, 07:12:47 PM »
 No personal experience with them, but I've looked at them a few times and thought about using them.  From what Ive heard, if you get them tuned right (or get lucky) they work well.  The bad point of them is finding someone who really understands how to tune them, and getting the parts to do it.

 You might have better luck starting a thread about how to get your Holley to idle right.  ;D

 Oh yea,
 X2, get rid of that vac adv dizzy.
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Welcome to the club of broken boats :o  Pay here$ bend over and move along.

gregb

  • Karma: +1/-0
Re: anybody running predator carbs?
« Reply #4 on: February 16, 2010, 09:45:58 PM »
I had one one my boat for a while.  I will say it had the best throttle response of any carb I've ever had on it, almost violent.  +1 for the cool factor also.  My setup idled about 900, but I have a smallblock and it's nowhere near your power level.  Downside, hard to get parts for, not that it has a lot inside, but the bowl gaskets aren't easy to come by.  Uses lots of gas.  Take a look down the throat when you get yours running and you'll see  what I mean.  Kind of tempermental also, sometimes it would fire right up, other times, not so much, and sitting in the middle of the lake trying to get it started is not what I want.  It never failed to start, but when your retrieving a skier and floating downriver I want to know that it's going to fire up the minute I hit the key in case I need to get out of the way of something.  It's a simple carb, it was not hard to tune.  I loved the throttle response, just not enough to keep using it.  I tried it on my Mustang, and it wouldn't run worth a s***.  I think it works better with an open exhaust.  That's my experience. 
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500hptaylor

  • Karma: +0/-0
Re: anybody running predator carbs?
« Reply #5 on: February 17, 2010, 06:01:25 AM »
I know how they perform on the blower and they are unreal. Like you said greg the throttle response is wicked. And I like that theory of variable venturi. The holley will not respond to my cam what so ever with the timing that I have to run. Believe me Ive taken it to some very reputable people and thaey just ask were in the hell did you get that cam. Ive tried two holleys so far and I wont dare try a edelbrock. So I figure if I can get a predator dialed in I will be able to have some idle quality (so I can go thru the wake zone without the geezers yelling) You ever try idling thru a wake at 1300 rpm sux especially after a few refreshments at party cove. I know they have a few cams (in the carb) that I can try, and that they are a totally different breed when it comes to tuning. I guess for every adjustment you make you have to turn back 1/8 turn (backlash)? Im in Ohio so it will be a couple of months before it gets on the water. I will let you know how it works.  For those of you running big cams whats the secret for idle quality. Usually on my track cars I could give a S*&t but not on a boat especially ours. Thanks guys.
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500hptaylor

  • Karma: +0/-0
Re: anybody running predator carbs?
« Reply #6 on: February 17, 2010, 06:17:56 AM »
One thing I forgot to mention is that the predator responds well to tunnel rams and single plain manifolds. Also 1-2'' spacers. They like big plenum. I have heard that if you try to run dual plane they are hard to tune. Plus alot of people from what I have heard mount them wrong. They are designed to be mounted a couple different ways, but for boats and some cars they need to be mounted with the bowl faceing front just so you guys know, I guess this is a common mistake. I'll get it going next month or so and let you guys know the results if it dont work at least I tried it. 

As you can tell I have alot of work to do before it gets back on the water>
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gregb

  • Karma: +1/-0
Re: anybody running predator carbs?
« Reply #7 on: February 17, 2010, 07:39:23 AM »
Just wondering, what size holley are you running and why are you running a vacuum advance on the distributor?
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500hptaylor

  • Karma: +0/-0
Re: anybody running predator carbs?
« Reply #8 on: February 17, 2010, 08:46:14 AM »
Greg, I have ran a 750,850 and tried a dom. I stick with vaccum advance because I spent a chitload on the dizzy and I have just always ran them. I have always liked the economy of a vac secondary carb as I do cruise quite a bit. Im used to them I guess. As far as Idle quality goes you know how high compression engines are they usually dont want to idle lower than 1100 or so.
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gregb

  • Karma: +1/-0
Re: anybody running predator carbs?
« Reply #9 on: February 17, 2010, 08:56:40 AM »
You should post some more specs, cam size, timing, initial and total, compression, the more info you provide the better folks are able to offer suggestions.  I've only got a 383SB, but it runs a lot better with the timing locked out. 
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GT Jets

  • Karma: +192/-0
Re: anybody running predator carbs?
« Reply #10 on: February 17, 2010, 08:57:52 AM »
Greg, I have ran a 750,850 and tried a dom. I stick with vaccum advance because I spent a chitload on the dizzy and I have just always ran them. I have always liked the economy of a vac secondary carb as I do cruise quite a bit. Im used to them I guess. As far as Idle quality goes you know how high compression engines are they usually dont want to idle lower than 1100 or so.

What boat is this on? If it's a jet, the vacuum advance is your Achilles heel, as far as the idle is concerned, I had a 13.5:1 468 that idled at 780 all day long, it is the cam duration and lift that determines if she will idle or not. What kind of vacuum numbers did you see at "idle"?

I would love to see this get figured out. The Predator may work well for this application, but I feel you have another issue... :thumbup:

GT

You should post some more specs, cam size, timing, initial and total, compression, the more info you provide the better folks are able to offer suggestions.  I've only got a 383SB, but it runs a lot better with the timing locked out. 

X2  ;)
  • Boat #1: 1992 Carrera 20.5 Elite (I/O bitches)
  • Boat #2: 19' Bubble deck Jet BBC Berkeley
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If i get some free time tonight at work, ill play with it and post it for everyone to see.

Time to man up and yank it John!  :banghead:
Ray

500hptaylor

  • Karma: +0/-0
Re: anybody running predator carbs?
« Reply #11 on: February 17, 2010, 09:34:51 AM »
GT, it is on a 18 ft Taylor SJ jet, I have neve had this problem with a vac carb and dizzy. As far as specs go here it is.

Cam-dur.256/266 @.50
 lift-.595/.621
     13.1 comp. 
     LSA is @110
 cylinder pressure is @ 185-195 across the board
       
The timing is set at 36 total timing and was reading around 6-8 inch pounds of vaccum. Everything so far has been right on for some reason I just cant get the idle down. I know Im getting enough vaccum because the secondaries open up well and it performs well. It is just the idle. I was told that it probably wont idle very well with that cam. The carbs that I have tried all had the same results and they were fresh carbs. The lowest I got it to idle was 1100 rpm after that she sputters and dies. I have heard that the predator suposedly helps with idle?
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gregb

  • Karma: +1/-0
Re: anybody running predator carbs?
« Reply #12 on: February 17, 2010, 10:28:51 AM »
I'm no expert but I'd try tuning it with the timing locked out at 36 degrees and the 850 carb before messing with the predator. 
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stc315

  • Karma: +3/-0
Re: anybody running predator carbs?
« Reply #13 on: February 17, 2010, 10:42:57 AM »
I had an old 750 3310 that I was running on bbc that had a nasty solid lifter cam. A crusty mechanic had me drill a small hole in each of the primary butterflies to make it idle. I don't remember what size hole, but they were small like 1/8" or less. It worked though.
  • Boat #1: 1987 Baker Tunnel Jet
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"Too much horsepower is almost enough!!!"

500hptaylor

  • Karma: +0/-0
Re: anybody running predator carbs?
« Reply #14 on: February 17, 2010, 11:19:24 AM »
Yep, been there done that it is a 1/16th bit.still no worky.
Ive built quite a few engines and have never had this problem. I am by no means a professional engine builder but I have had success at it.

Greg I got the predator on the cheap so Im gonna try it see what it does. Not gonna hurt any LOL
I think I will try to lock the timing like you say. I know on the light it is spot on 36 at 3000 rpms.

I'll let you guys know what happens when I pull it back in the shop. Right now I am painting my tow rig.
This is why I like this site so many helpful people.Thanks for the help guys
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GT Jets

  • Karma: +192/-0
Re: anybody running predator carbs?
« Reply #15 on: February 17, 2010, 02:35:31 PM »
GT, it is on a 18 ft Taylor SJ jet, I have neve had this problem with a vac carb and dizzy. As far as specs go here it is.

Cam-dur.256/266 @.50
 lift-.595/.621
     13.1 comp. 
     LSA is @110
 cylinder pressure is @ 185-195 across the board
       
The timing is set at 36 total timing and was reading around 6-8 inch pounds of vaccum. Everything so far has been right on for some reason I just cant get the idle down. I know Im getting enough vaccum because the secondaries open up well and it performs well. It is just the idle. I was told that it probably wont idle very well with that cam. The carbs that I have tried all had the same results and they were fresh carbs. The lowest I got it to idle was 1100 rpm after that she sputters and dies. I have heard that the predator suposedly helps with idle?

Don't take this the wrong way, but I think you have an issue if you are only seeing 6-8" hg at idle, you would need to be in the 10-13 range IMHO to get it to idle under 1000 RPM, how was the cam installed degree wise, it almost sounds too advanced...That is a pretty aggressive stick, but 6-8" sounds too weak to me, for the record, it takes at least 7" to fully pull the vacuum advance in, the vacuum secondaries can be sprung down to I think 3", but don't quote me there...

What type of lifters? Flat solid, solid roller, hydro roller?

Still seems way off IMHO.

GT
  • Boat #1: 1992 Carrera 20.5 Elite (I/O bitches)
  • Boat #2: 19' Bubble deck Jet BBC Berkeley
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If i get some free time tonight at work, ill play with it and post it for everyone to see.

Time to man up and yank it John!  :banghead:
Ray

500hptaylor

  • Karma: +0/-0
Re: anybody running predator carbs?
« Reply #16 on: February 17, 2010, 04:39:50 PM »
The cam was installed 4 degree advanced, thats what it called for. If my vaccum was off by that much how can it function well in all other rpm ranges. I am running flat lifters. I have taken the engine down before and everything was kosher.

Maybe Im just stuck on stupid,HAHA

My buddy is a great engine builder and he says that some cams just dont like to idle low , something about the overlap being so close or something like that? Maybe its in the dizzy, maybe some different springs?
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GT Jets

  • Karma: +192/-0
Re: anybody running predator carbs?
« Reply #17 on: February 17, 2010, 05:09:38 PM »
The cam was installed 4 degree advanced, thats what it called for. If my vaccum was off by that much how can it function well in all other rpm ranges. I am running flat lifters. I have taken the engine down before and everything was kosher.

Maybe Im just stuck on stupid,HAHA

My buddy is a great engine builder and he says that some cams just dont like to idle low , something about the overlap being so close or something like that? Maybe its in the dizzy, maybe some different springs?

I would definitely not say stupid....

Is there a chance that you have the wrong rocker arms or something similar, too much ratio will increase things dramatically and could cause an issue similar to this...And your bud is correct, sometimes idle is not an option on some builds.... :banghead:

GT

  • Boat #1: 1992 Carrera 20.5 Elite (I/O bitches)
  • Boat #2: 19' Bubble deck Jet BBC Berkeley
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If i get some free time tonight at work, ill play with it and post it for everyone to see.

Time to man up and yank it John!  :banghead:
Ray

crewchief22

  • Karma: +66/-0
Re: anybody running predator carbs?
« Reply #18 on: February 17, 2010, 06:41:22 PM »
The cam was installed 4 degree advanced, thats what it called for.


Was the 4 degree advance recommended by the cam grinder or the shop that sold it?  Most cam grinders recommend installing the cam "straight up" and adjust advance/retard for special applications.

110 lobe seperation is not excessively close (rough idle and poor vacuum).

I'm sure you have, but I have to ask anyway, have you verified that there are no vacuum leaks?
  • Boat #1: '77 Hondo Pantera GT Jet
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"Racing is life!  Anything that happens before or after, is just waiting"    Steve McQueen

The problem with America is stupidity. I'm not saying there should be a capital punishment for stupidity, but why don't we just take the safety labels off of everything and let the problem solve itself?

GT Jets

  • Karma: +192/-0
Re: anybody running predator carbs?
« Reply #19 on: February 17, 2010, 06:49:20 PM »
After running your combo with a few "assumptions" through a desktop dyno, idle should be in the high 900's to 1100 RPM..

You have to drive the boat like I drove the Renegade, with the reverse gate controlling the speed at idle... :banghead:

If you get that thing to idle below 900 RPM it will be so loaded up it will probably start fouling stuff.... :mad:

GT
  • Boat #1: 1992 Carrera 20.5 Elite (I/O bitches)
  • Boat #2: 19' Bubble deck Jet BBC Berkeley
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If i get some free time tonight at work, ill play with it and post it for everyone to see.

Time to man up and yank it John!  :banghead:
Ray

500hptaylor

  • Karma: +0/-0
Re: anybody running predator carbs?
« Reply #20 on: February 17, 2010, 07:43:53 PM »
crewchief, the 4 degree was recomended from  the cam grinder and I have no vaccum leaks.

GT your correct if I get around 900 it will load up bad, bt will stay there for a little while, so that is telling me that it is my cam, I guess I will just live with it and do like you say drive with the reverse gate.

Thanks for all the help guys.
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