Carburetor (dominator) Recommendation
09-03-2018, 03:48 PM
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Carburetor (dominator) Recommendation
I have new naturally aspirated engines, 580 cid, Dart Pro1 325, solid roller (704/698 lift - 264/272 dur, I/E). Engines made right at 700hp @ 5600. Props are 18x29 4 blade cleavers on SSM4. Now that engines are in the boat I want to finish tuning but have concerns with the 3 circuit 1050's that are on there. I recently installed Daytona Sensors for idle stabilization but timing alone didn't do the trick. The previous locked timing at 34* would allow a 1000 RPM idle in neutral and about 600 in gear but struggling. To aid with starting I added an advance curve to the distributors while they were out during engine build but that seemed to hurt the idle. With the new ignition I'm back to 30* initial and 35* total with 10* start retard. I'm close to back to where I was with about 550 RPM idle and struggling around the dock. I could continue to add initial timing but not sure that'll get me to a more comfortable 700 rpm idle. I was preparing to go into the carbs to improve the idle but wondering if I'm wasting my time improving idle on 3 circuit carbs that may never be right in the mid range because of the intermediate circuit. I thought of converting these to 2 circuit and starting from there but now thinking about just starting with new carbs.
I see that Holley has changed up the dominators quite a bit in the last 5-10 years. I don't exactly know what my current dominators are, they are a newer style than the original but not the current style. They came with the boat and had a custom builders decal on them. I contacted him but he wasn't any help in identifying them but did suggest and offer build me new 2 circuit carbs. I'm wondering if I'd be better of starting with a new Holley Gen III Ultra 1050 such as the 80902. I looked at Holley's marine version (80903) but it is 3 circuit and that doesn't appear to be ideal for these applications. I also looked at the Quick Fuel M-4710, marine 1050 and QFT FX-4700. I think these 3 are the best choices for a 1050. Also woder if an 1150 would be worth considering.
I'm aware of the marine / non-marine implications and don't want to start that **** storm. I'm fine paying the additional for a marine carb however performance and drive ability are priority.
I'm interested in your opinions on the best carb for my application. Not sure I understand the pro's/cons of Holley vs Quick fuel since they're under the same ownership have the same tech support. They seem to have the same features and both are more advanced than what I currently have.
The carbs look a little different but inside are they the same ?
Will they perform the same or is one better?
Which one would be better out the box and require less tuning?
Is one easier to tune?
I don't expect this to be completely plug an play, I've worked on many Holleys and am prepared to dial these in. Hopefully I can find something that'll be a better starting point than what I have and need only basic adjustments to get up and running better than I am now. Would prefer not to have to deal with a carb specialist and go through the back and forth with them to try to get something that'll work like it should. Hopefully the new Holley or QFT will have all the things in place for me to get things right by simply adjusting and replacing jets/restrictors/bleeds.
I appreciate all input.
I see that Holley has changed up the dominators quite a bit in the last 5-10 years. I don't exactly know what my current dominators are, they are a newer style than the original but not the current style. They came with the boat and had a custom builders decal on them. I contacted him but he wasn't any help in identifying them but did suggest and offer build me new 2 circuit carbs. I'm wondering if I'd be better of starting with a new Holley Gen III Ultra 1050 such as the 80902. I looked at Holley's marine version (80903) but it is 3 circuit and that doesn't appear to be ideal for these applications. I also looked at the Quick Fuel M-4710, marine 1050 and QFT FX-4700. I think these 3 are the best choices for a 1050. Also woder if an 1150 would be worth considering.
I'm aware of the marine / non-marine implications and don't want to start that **** storm. I'm fine paying the additional for a marine carb however performance and drive ability are priority.
I'm interested in your opinions on the best carb for my application. Not sure I understand the pro's/cons of Holley vs Quick fuel since they're under the same ownership have the same tech support. They seem to have the same features and both are more advanced than what I currently have.
The carbs look a little different but inside are they the same ?
Will they perform the same or is one better?
Which one would be better out the box and require less tuning?
Is one easier to tune?
I don't expect this to be completely plug an play, I've worked on many Holleys and am prepared to dial these in. Hopefully I can find something that'll be a better starting point than what I have and need only basic adjustments to get up and running better than I am now. Would prefer not to have to deal with a carb specialist and go through the back and forth with them to try to get something that'll work like it should. Hopefully the new Holley or QFT will have all the things in place for me to get things right by simply adjusting and replacing jets/restrictors/bleeds.
I appreciate all input.
09-03-2018, 08:13 PM
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The idle stabilization will increase timing to keep rpm up. What’s the rpm set for that? Mine is at 700 and stays there. I would put initial at 12-14 or so. Let idle stabilization do its thing. Put the boat in gear and tune the idle. See how that works out. I’m by no means a carb guru but if your initial is 30 you’re not letting idle stab do it’s job.
09-03-2018, 08:56 PM
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Minimum idle was set for 750. I believe 12-14 will be way to low for my camshafts. I started at 26 with 10* of idle stabilization with zero benefits although the timing was advancing. I don't fault the ignition for not doing as advertised, because it was. In fact I first tried it in neutral by simply backing out the idle speed screw. As the rpm dropped the timing went up and back came the RPM but that was in neutral. 30* was the only way it would somewhat idle in gear. My guess is someone before me came to the same conclusion which is why the distributor was locked when I got the boat.
09-03-2018, 11:01 PM
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Definitely big cams. What about vacuum leak? Idle should only involve idle circuit. Naturally you want the stab do have it’s full range. I watch mine bounce from 14 to 34. Still tweaking mine but one is at 700-710 the other is 690-700. Min is set at 700. Neutral is 9-925. Before this I was dropping almost 500 rpm going in gear. My cams aren’t as large as yours and are hydraulic rollers. Next I’m gonna fine tune with myO2s. I just think 30 initial isntoo mich. you’re throwing s lot of timing at it when it’s loaded the hardest getting on plane. Againnot an expert but that doesn’t seem like the answer. Even locked timing seems to have its fair of issues. I almost wonder if that is one of the reasons many people think blowers are unreliable. Lock the timing and detonate just getting on plane. I’d start looking for a vacuum leak. I’d try initial in the 14-16 range. Give stab all the way to max and then try tuning with mixture screws. May not work but that’s where I’d go next.
09-04-2018, 04:48 AM
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Your points are well taken. Adjusting the timing is easy enough to try at this point so why not. Either way I still have concerns about getting the 3 circuit dominator dialed in across the full operating range and would like any input on that subject as well.
09-04-2018, 06:21 AM
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Hey bud.
I would play with some timing settings some more, before replacing the carbs. You can try a few different idle setups and see what works best. Heres what i would try.
16* base. Add 20* of idle stabilization for 36* at 700rpm set point.
22* base. Add 20* of idle stabilization for 42* at 700rpm set point.
of course that will require you to lock the timing manually at 36* and 42* respectively, then upload the map. Then of course build a map/curve that suits your timing curve above idle.
The larger spread of 20 degrees between loaded and unloaded should theoretically help the situation.
If i was buying a carb today for that engine, i would look at an ultra gen 3 dominator 2 circuit. The carb has many nice new features, one of them being the idle tuning thingy they have.
I would play with some timing settings some more, before replacing the carbs. You can try a few different idle setups and see what works best. Heres what i would try.
16* base. Add 20* of idle stabilization for 36* at 700rpm set point.
22* base. Add 20* of idle stabilization for 42* at 700rpm set point.
of course that will require you to lock the timing manually at 36* and 42* respectively, then upload the map. Then of course build a map/curve that suits your timing curve above idle.
The larger spread of 20 degrees between loaded and unloaded should theoretically help the situation.
If i was buying a carb today for that engine, i would look at an ultra gen 3 dominator 2 circuit. The carb has many nice new features, one of them being the idle tuning thingy they have.
09-04-2018, 07:32 AM
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X2 on the new Holley Dom's 
Stay away from Quick Fuel!!! They "look" awesome, but we had one with serious manufacturing flaws and they would NOT stand behind their product!!! Not cool! Plus the Holleys made about 20hp more on the dyno!
Stay away from Quick Fuel!!! They "look" awesome, but we had one with serious manufacturing flaws and they would NOT stand behind their product!!! Not cool! Plus the Holleys made about 20hp more on the dyno!
09-04-2018, 07:43 AM
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Thanks Mild. I'll try something in the teens and ad more stabilization. Doing so will force me to open the blades more to get the neutral idle back to about 1000. Perhaps the blades being open more will enable the additional stabilization to be more effective. Makes sense because with 30* initial and 550 rpm (in gear) I have to open the throttle a little to get up to 700ish rpm. If I understand this correctly, when in gear, I'll ultimately end up with the same combination of throttle position and advance but rather than having to constantly jockey the sticks I'll have the ignition system automatically making the timing changes instead. Thanks to you an Crude for the tip, I'll report back the results.
Still think I'll be replacing carbs at some point because mine have limited tuneability. I'm confident I'll get the 3 circuit to idle as it does have replaceable idle restrictions and the 3rd circuit shouldn't affect the idle. Just not optimistic about being able to get the entire fuel curve dialed in with the intermediate circuit rather than a power valve.
Still think I'll be replacing carbs at some point because mine have limited tuneability. I'm confident I'll get the 3 circuit to idle as it does have replaceable idle restrictions and the 3rd circuit shouldn't affect the idle. Just not optimistic about being able to get the entire fuel curve dialed in with the intermediate circuit rather than a power valve.
09-04-2018, 08:16 AM
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I haven't gotten that far yet. I wanted to get the low end straightened out first then mid range and finally on to top end. Hoping to deal with props, rotation, spacers over the winter.
