2x4 Dominator carb issues.

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rewguy
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2x4 Dominator carb issues.

Post by rewguy »

565 BBC. 14.5-1, solid roller. Don't know much background on the engine except that it supposedly made 1030 hp at 7600. The carbs are 2-1150 Quickfuel 3 circuit tunnel ram carbs. They have 1:1 linkage, but actually the problem was identical even with progressive linkage. All logical things have been checked a half a dozen times. Float level, transfer slot exposure, etc. The car is 3350 lbs, TH400, 6000 converter, 4.30 gear, 28x10.5 tire. When brought up to say....2200 rpm, and floored......sputters, hesitates, bucks, and about 60 feet out roars to life and kills the tires. I talked to JMarkaudio, and we converted the carbs to his billet 2 circuit blocks. Put in a base tune-up that he suggested. He has been a huge help through all of this, and I hate blowing his phone up because I'm certain that answering questions gets old quickly. Basically we are in the same boat as we were in originally. We started out with 35 squirters front and rear. We tried 31's front and rear. We tried 40's front and rear, and even bigger also. The 35's seem overall the best. The best....crispest idle and easiest starting we found yet was with .037 IFR and .036 idle air bleed. But the huge hesitation and stumbling was still there. We opened up the IFR to .038, and then the idle air bleeds to .038 as well, and the idle quality dropped, and it didn't sound as crisp, felt lazier, and started harder. The main jets are BLP 112's on all 8. (I was told they were equivalent to a holley 94..?) Where to go now? Looking for any ideas.
And to be clear......we borrowed a pair of 3 circuit CFM 1050 Dominators off of a small block car, and it ran flawlessly......So it is absolutely a carb issue with no doubt.
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Re: 2x4 Dominator carb issues.

Post by prairiehotrodder »

obvious answer - the carbs are to big.

sorry probably not the answer you were looking for.
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rewguy
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Re: 2x4 Dominator carb issues.

Post by rewguy »

well...... on Kevis Self's recommendation, we made 2 1050 dominators work on a 820 hp 406 in. sbc. So I do find it hard to believe that 2 1150 carbs wont work on a 565 with 210 more hp. And JMarkaudio didn't mention anything about the size being an issue either.
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Re: 2x4 Dominator carb issues.

Post by prairiehotrodder »

yes i'm sure you are right. I was just commenting based on the fact that the 2 1050's worked and the 1150's don't. I also have a tunnel ram with 2 750's on a 540 BBC. You are making 300 hp more than me so i don't have any experience to offer in that ballpark. Whats different about the tuneup on the 1050's that makes them work so good ? Is your squirter all used up by the time you floor it ?
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Re: 2x4 Dominator carb issues.

Post by prairiehotrodder »

can you change pump cams to delay the squirt ?
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Re: 2x4 Dominator carb issues.

Post by Steve.k »

I take it no trans brake? It can be two things either to much pump shot or not enough. Check shooter size and lower two sizes at time. If no change ( there should be) try bigger. You can make gains with pump cam changes also. You likely way below powerband of engine so its going to be difficult to set at 2200.if you were launching at 4400 doubt there be a problem.
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Re: 2x4 Dominator carb issues.

Post by ijames »

I'm assuming no WBO2, so have you had someone staring at the exhaust pipes when you hit it? If it's too much pump shot, enough to get sputtering and missing, I would think that you should see some nice puffs of black smoke from the pipes as it goes way rich. (Old school FTW :-).) If it's rich you then need to decide if it's a timing issue where the total shot is ok but it's all in way to quick, or if the shot is too big. Either way, first determine if it's going rich or lean on the hit and then adjust the tune.
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rewguy
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Re: 2x4 Dominator carb issues.

Post by rewguy »

No wideband. The car will not come up clean on the brake at all. The carbs that worked had the same exact yellow pump cams, and the same exact squirter size, and the same volume acc. pump housings. There is absolutely no black soot that we saw in the dozen times we tested it?
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Re: 2x4 Dominator carb issues.

Post by MadBill »

With no trace of black smoke one could reasonable assume it's going lean until proven otherwise. What size pumps are you using and regardless of pump cam color and hole, have you checked for full stroke on all of them?
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Re: 2x4 Dominator carb issues.

Post by jmarkaudio »

No issue answering, just a busy time of year for me that makes getting a call tough sometimes. I sent out a care package today, some different pump cams to try and some set screws. When you get the pump cams call and I'll give you instructions for them.
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Re: 2x4 Dominator carb issues.

Post by af2 »

I will say in the off season I will be talking to Mark for the 2 1050 on methanol. I have not had to tune the 1 carb I got from him 2 years ago! It came dialed period!! Good people!
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Re: 2x4 Dominator carb issues.

Post by af2 »

I will say also regardless of carbs the stall had everything to do with the launch. I have to go at 6000 or it hiccups below that .
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Re: 2x4 Dominator carb issues.

Post by ustahava67 »

.038 idle air bleeds seem small. most 2 circuit stuff I play with is in the .065-.076 region
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Re: 2x4 Dominator carb issues.

Post by rewguy »

Mark told me he likes to see the idle mixture screws out between .75 and 1.25 turns when correct on this 2x4 setup
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Re: 2x4 Dominator carb issues.

Post by rewguy »

Guy at Quickfuel claims the carbs NEED to be flowed or we will be chasing our tails....... seems a bit hard to believe....but?
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