T-slot restrictor.
Will clean up idle and off idle crap running.
Will clean up idle and off idle crap running.
Carb issues, 3 circuit vs 2 circuit.
Hey guys,
First post.
I've been a professional tech for 38 years, and have done a lot of quality work on a lot of cars over the years. Carbs don't scare me, well, until now.
I have a 1050 dominator on a 472" big block Ford. Its a 3 circuit. it runs super rich at idle and off idle. It has annular boosters and I think it may be just too big of a carb. My cam is not that radical. I don't want to start messing with air bleeds yet. Its a 8896-2. I installed the progressive secondary linkage for the street, and blocked off the rear power valve. 88 jets in the front, 92 in the rear. Just looking for a good baseline.
The engine has about 6" vacuum at idle in park, so I put a 2.5 PV in it. Currently running 18* initial and 34* total timing.
I have a piece of MIG wire bent in half and put in each intermediate feed in the body. I also removed the intermediate air bleeds completely to take them out of the picture (theoretically anyway)
As soon as you crack the throttle, you can see fuel coming out of the annular booster and the thing just loads up.
Main question is, do the annular boosters flow that much more than the doglegs? The previous build on this engine had C9 heads and a dual plane intake and a 850DP. I still have that carb in case I need it for a donor to convert this thing to a 2 circuit. I had 88s square in that carb.
The high speed air bleeds are 59s. The idle are 38s.
Can anyone help me out? The car is for sale, but I would really like to get it dialed in and maybe take it to the track this year at least once.
First post.
I've been a professional tech for 38 years, and have done a lot of quality work on a lot of cars over the years. Carbs don't scare me, well, until now.
I have a 1050 dominator on a 472" big block Ford. Its a 3 circuit. it runs super rich at idle and off idle. It has annular boosters and I think it may be just too big of a carb. My cam is not that radical. I don't want to start messing with air bleeds yet. Its a 8896-2. I installed the progressive secondary linkage for the street, and blocked off the rear power valve. 88 jets in the front, 92 in the rear. Just looking for a good baseline.
The engine has about 6" vacuum at idle in park, so I put a 2.5 PV in it. Currently running 18* initial and 34* total timing.
I have a piece of MIG wire bent in half and put in each intermediate feed in the body. I also removed the intermediate air bleeds completely to take them out of the picture (theoretically anyway)
As soon as you crack the throttle, you can see fuel coming out of the annular booster and the thing just loads up.
Main question is, do the annular boosters flow that much more than the doglegs? The previous build on this engine had C9 heads and a dual plane intake and a 850DP. I still have that carb in case I need it for a donor to convert this thing to a 2 circuit. I had 88s square in that carb.
The high speed air bleeds are 59s. The idle are 38s.
Can anyone help me out? The car is for sale, but I would really like to get it dialed in and maybe take it to the track this year at least once.
1 - 13 of 13 Posts
Personally I'd block the PV, jet it square at 92 and lock the distributor out at 34*.
99% of idle mixture problems are because your not idling on the idle circuit.... big cam, no initial timing = throttle blade open too far - ie. transfer slot overexposed and the transition circuit on an 8896 is richer than Bill Gates... your going to have problems with this scenario. Not enough initial timing xplains alot about why the engine doesn't have any vacuum at idle as well... unless something is mechanically wrong.
Also the PV dosen't work like your thinking, obvious by you installing a 2.5 to combat the rich idle and transition to the main.... like I said I think with your combo, you are best to just block it off and jet square. FyI the PV dosen't have anything to do with the idle circuit or the vacuum the engine develops at idle despite what Holley prints in its stupid tuning quick reference. There are really good very detailed explanations of what and how the PV works already on the forum here, it's quite involved so I'm not going to re-write the book....
A 1050 8896 will run fine on a 472 BBF with the proper setup of everything releated.
Will
99% of idle mixture problems are because your not idling on the idle circuit.... big cam, no initial timing = throttle blade open too far - ie. transfer slot overexposed and the transition circuit on an 8896 is richer than Bill Gates... your going to have problems with this scenario. Not enough initial timing xplains alot about why the engine doesn't have any vacuum at idle as well... unless something is mechanically wrong.
Also the PV dosen't work like your thinking, obvious by you installing a 2.5 to combat the rich idle and transition to the main.... like I said I think with your combo, you are best to just block it off and jet square. FyI the PV dosen't have anything to do with the idle circuit or the vacuum the engine develops at idle despite what Holley prints in its stupid tuning quick reference. There are really good very detailed explanations of what and how the PV works already on the forum here, it's quite involved so I'm not going to re-write the book....
A 1050 8896 will run fine on a 472 BBF with the proper setup of everything releated.
Will
"The high speed air bleeds are 59s. The idle are 38s." I think that is backwards. Are you sure the floats are not too high or bad?
I know the PV isnt contributing to idle issues (unless it blown). The reason I mentioned it, was because I advanced my timing to 18*, I was only getting around 4" of vacuum. With a 6.5 PV, that sucker never closes at 4", so it was open all the time and was absolutely contributing to my off idle richness.Personally I'd block the PV, jet it square at 92 and lock the distributor out at 34*.
99% of idle mixture problems are because your not idling on the idle circuit.... big cam, no initial timing = throttle blade open too far - ie. transfer slot overexposed and the transition circuit on an 8896 is richer than Bill Gates... your going to have problems with this scenario. Not enough initial timing xplains alot about why the engine doesn't have any vacuum at idle as well... unless something is mechanically wrong.
Also the PV dosen't work like your thinking, obvious by you installing a 2.5 to combat the rich idle and transition to the main.... like I said I think with your combo, you are best to just block it off and jet square. FyI the PV dosen't have anything to do with the idle circuit or the vacuum the engine develops at idle despite what Holley prints in its stupid tuning quick reference. There are really good very detailed explanations of what and how the PV works already on the forum here, it's quite involved so I'm not going to re-write the book....
A 1050 8896 will run fine on a 472 BBF with the proper setup of everything releated.
Will
So I took the carb off last night because I wanted to see where the transfer slots were. The primary was almost completely exposed, while the secondary was covered up 100%. In the process of checking all that, I felt a bind in the linkage so I fell down the rabbit hole fixing it. I have the carb 100% completely apart on my bench now, throttle shafts and all.. no biggie, but it just set me back a little. I need to bend the link shorter to get it right. It probably would have been fine the way it was, but I don't want any issues.
I need to get another PV plug. Thats a good idea about taking them both out (at least for diag purposes).
I've set up a lot of carbs in my career, but never a dominator, and not many double pumpers. Mostly vac secondary carbs and Quadrajets.
Thanks for the help, I appreciate it sir.
Yep, I saw it with my own eyes. (with a magnifying glass of course). According to Holley's spec sheet on this carb, the bleeds should be Idle- 53, Intermediate- 63, and High Speed- 40. I don't know what the hell to think about that. LOL. I'll swap them back I guess."The high speed air bleeds are 59s. The idle are 38s." I think that is backwards. Are you sure the floats are not too high or bad?
The floats are dead nuts. I was thinking of dropping them a little though.
Thanks for the input, sir. I appreciate it.
I’ve had better luck pv,s in. But thats me. 2.5 should fix you up. And make sure back barrel slot is jus visible. Not to open.I know the PV isnt contributing to idle issues (unless it blown). The reason I mentioned it, was because I advanced my timing to 18*, I was only getting around 4" of vacuum. With a 6.5 PV, that sucker never closes at 4", so it was open all the time and was absolutely contributing to my off idle richness.
So I took the carb off last night because I wanted to see where the transfer slots were. The primary was almost completely exposed, while the secondary was covered up 100%. In the process of checking all that, I felt a bind in the linkage so I fell down the rabbit hole fixing it. I have the carb 100% completely apart on my bench now, throttle shafts and all.. no biggie, but it just set me back a little. I need to bend the link shorter to get it right. It probably would have been fine the way it was, but I don't want any issues.
I need to get another PV plug. Thats a good idea about taking them both out (at least for diag purposes).
I've set up a lot of carbs in my career, but never a dominator, and not many double pumpers. Mostly vac secondary carbs and Quadrajets.
Thanks for the help, I appreciate it sir.
8896-2 Holley Questions!
Is this carb a 3 circuit and is it easily tunable?:confused: Thanks!
www.yellowbullet.com
You will want to follow JMarkaudio's recommended set up in this thread... Mark is an unbelievably good, nationally known carburetor builder.
1) Main Air Bleed .026
2) Intermediate Air Bleed remove entirely
3) Power Valves blocked
4) Main Jet square at 92 (to start)
Will
Update on the beast.
I took all of your advice and took the carb off. I adjusted the front and back throttle blades to where the transfer slot was just square using the butterfly as a mirror. Where it was, I was using my primary for idle speed adjustment only. and the secondaries were completely closed. The MABs are 53 and the IAB are 38.. I don't own an assortment of bleeds, so I went with the biggest on the MABs to hopefully delay the initial signal.
Man, I thought that there was no way this was going to idle with those openings. I thought for sure I'd have to drill holes in the butterflies. Boy was I wrong. This thing popped right off and idled about 2000 rpm. Knowing that the transfer slots were perfect, I decided to use timing to bring the idle down. By the time I got it down to 1000rpm or so, my initial timing was 0*. Temp started to climb, so I figured that was a no go.
I put the timing back and started closing the idle adjustments down, 1/4 turn at a time, both front and back, until I had it at about 800... I was sure that the transfer slots were all but completely covered at this point. I got the idle speed down, adjusted the mixture to highest vacuum (6" only) and took it for a drive. The idle is very nice and I actually have adjustment now.
Still loading up part throttle. I still have a 2.5 PV in it, which I'm sure is the issue there. I have a PV plug coming for the primary block. I already have the secondaries blocked.
Brought it in and went down 2 jet sizes. I'm now 86 pri, 88 sec. Holley tech told me months ago that due to the difference in design between the dogleg and annular boosters, that the annular boosters need to be jetted down about 4 jet sizes due to the increased flow. Second road test was MUCH better. I was able to open it up a little. This thing is a beast.... it really is.
I was seeing a significant flat spot a couple times during the road test and figured that its because the transfer slots are most likely covered completely at this point.
I'm not going to do anything else until I get the PV plug for the front.
One thing to note as well. I had an issue with it dieseling after shutting it down before.. Not anymore.
I plan on taking the carb off again just to verify the transfer slots are where I think they are. I don't know if I'll be able to go back to just using my primary for idle speed adjustment. I believe that's why it was dieseling because the over exposed transfer slots was providing fuel.
Thanks for the help guys. Any more feedback is greatly appreciated.
I took all of your advice and took the carb off. I adjusted the front and back throttle blades to where the transfer slot was just square using the butterfly as a mirror. Where it was, I was using my primary for idle speed adjustment only. and the secondaries were completely closed. The MABs are 53 and the IAB are 38.. I don't own an assortment of bleeds, so I went with the biggest on the MABs to hopefully delay the initial signal.
Man, I thought that there was no way this was going to idle with those openings. I thought for sure I'd have to drill holes in the butterflies. Boy was I wrong. This thing popped right off and idled about 2000 rpm. Knowing that the transfer slots were perfect, I decided to use timing to bring the idle down. By the time I got it down to 1000rpm or so, my initial timing was 0*. Temp started to climb, so I figured that was a no go.
I put the timing back and started closing the idle adjustments down, 1/4 turn at a time, both front and back, until I had it at about 800... I was sure that the transfer slots were all but completely covered at this point. I got the idle speed down, adjusted the mixture to highest vacuum (6" only) and took it for a drive. The idle is very nice and I actually have adjustment now.
Still loading up part throttle. I still have a 2.5 PV in it, which I'm sure is the issue there. I have a PV plug coming for the primary block. I already have the secondaries blocked.
Brought it in and went down 2 jet sizes. I'm now 86 pri, 88 sec. Holley tech told me months ago that due to the difference in design between the dogleg and annular boosters, that the annular boosters need to be jetted down about 4 jet sizes due to the increased flow. Second road test was MUCH better. I was able to open it up a little. This thing is a beast.... it really is.
I was seeing a significant flat spot a couple times during the road test and figured that its because the transfer slots are most likely covered completely at this point.
I'm not going to do anything else until I get the PV plug for the front.
One thing to note as well. I had an issue with it dieseling after shutting it down before.. Not anymore.
I plan on taking the carb off again just to verify the transfer slots are where I think they are. I don't know if I'll be able to go back to just using my primary for idle speed adjustment. I believe that's why it was dieseling because the over exposed transfer slots was providing fuel.
Thanks for the help guys. Any more feedback is greatly appreciated.
You might try idleing it off the secondary throttle screw. I have never found a 2.5 power valve useful.
I thought annular boosters reduced air flow?????
All that 58 MAB is going to do is create a fuel curve that gets leaner as RPM increases... which what 8896s do anyway. Rich AF at idle and part throttle then lean at WOT.
Smaller 26 MAB will reduce emulsion and flatten the fuel curve out as RPM increases. Only then you will be able to make rational decisions about what it needs for jetting.
Removing the intermediate circuit bleed will lean out part throttle by increasing emulsion......
FYI annular boosters increases the signal to the main well - pulling more fuel.... that "jetting down" comment dosen't mean anything in this context because it's a system with many parts that affect the calibration.... the MAB, the number and size of emulsion bleeds in the metering block, size of the main well passages, main jet size.... that stuff is completely different from your old 4150 with downleg boosters to a 4500, all of which are annular boosters.
Now why Holley still has the calibration of the 8896 so f'd up is beyond me... the 3 circuit 4500s were orginally designed for (I believe) the Boss 429 NASCAR program and they were actually setup to meter as individuall barrels, ie. Each barrel was isolated to an intake runner with no plenum... why they keep that calibration around and sell it as the correct fit for single carb applications just astounds me....
Will
Smaller 26 MAB will reduce emulsion and flatten the fuel curve out as RPM increases. Only then you will be able to make rational decisions about what it needs for jetting.
Removing the intermediate circuit bleed will lean out part throttle by increasing emulsion......
FYI annular boosters increases the signal to the main well - pulling more fuel.... that "jetting down" comment dosen't mean anything in this context because it's a system with many parts that affect the calibration.... the MAB, the number and size of emulsion bleeds in the metering block, size of the main well passages, main jet size.... that stuff is completely different from your old 4150 with downleg boosters to a 4500, all of which are annular boosters.
Now why Holley still has the calibration of the 8896 so f'd up is beyond me... the 3 circuit 4500s were orginally designed for (I believe) the Boss 429 NASCAR program and they were actually setup to meter as individuall barrels, ie. Each barrel was isolated to an intake runner with no plenum... why they keep that calibration around and sell it as the correct fit for single carb applications just astounds me....
Will
But the 9375 3 circuits work great and are said to be the best ones Holley made!!All that 58 MAB is going to do is create a fuel curve that gets leaner as RPM increases... which what 8896s do anyway. Rich AF at idle and part throttle then lean at WOT.
Smaller 26 MAB will reduce emulsion and flatten the fuel curve out as RPM increases. Only then you will be able to make rational decisions about what it needs for jetting.
Removing the intermediate circuit bleed will lean out part throttle by increasing emulsion......
FYI annular boosters increases the signal to the main well - pulling more fuel.... that "jetting down" comment dosen't mean anything in this context because it's a system with many parts that affect the calibration.... the MAB, the number and size of emulsion bleeds in the metering block, size of the main well passages, main jet size.... that stuff is completely different from your old 4150 with downleg boosters to a 4500, all of which are annular boosters.
Now why Holley still has the calibration of the 8896 so f'd up is beyond me... the 3 circuit 4500s were orginally designed for (I believe) the Boss 429 NASCAR program and they were actually setup to meter as individuall barrels, ie. Each barrel was isolated to an intake runner with no plenum... why they keep that calibration around and sell it as the correct fit for single carb applications just astounds me....
Will
1 - 13 of 13 Posts
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