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holley tells me that the 5 emulsion bleeds from top to bottom are:
29, 29, 29, blank, 29. i am reading that the lower holes effect the high rpms. so maybe another blank in the 3 hole? |
I guess we will all do some more research, but from memory most Demons run 2 and 4 as blanks, 31s for the other 3.
Since Demon no longer exists, a lot harder to find this sort of info now: http://static.summitracing.com/globa...em-1282010.pdf I'll see what QFT offers. |
Gonna try blocking 3 set of the emulsion bleeds and see what effect it has - will leave the 29s in #1 and #3 and block #2 and #5 (#4 already blocked).
From other searches it seems like jmarkaudio (he seems to have good standing in the robust community that favors emulsion bleed tuning) recommends it: Anyone found a good tune for Holley Ultra HP 850? • Speed Talk "Excessive emulsion is a large part of the issue, the Ultra 850 is fine otherwise. .026 main air bleeds, put .026 emulsion bleeds in the top and 4th emulsion, plug the rest. Move the idle feed shown in the link below, try either a .035 or .036 idle jet. 92 square jets to start with PV's plugged with non oxygenated fuel. Jet as needed for best performance for the engine needs and fuel characteristics. If you need a PV for the street, put one in the primary only, jet the primary down 5 to start, repeat jet the primary as needed. Use a 6.5 PV minimum." Seems he knows more about this than I do... Since I am generally satisfied with the primary side performance, gonna start with the secondaries. Sound reasonable? |
fastd .... go to Mark`s site . racingfgelsystems /my fun forum and you will see so much stuff of tuning Holleys , carb theory , emulsion tuning etc your head will hurt . There are a LOT of extremely knowledgeably guys there who are more than willing to help .
That`s where I went for my "education" . Bob |
Bobcat,
Thanks but couldn't find the website...can you post the link or a slightly better address? Regards Phil |
Sorry for the fat fingers . Try : racingfuelsystems-Myfunforum.org.
Having problems with my Mac since I put the new hard drive in and haven`t been able to attach the address as a link . I just tried the above address and it worked for me . Bob |
I don't think this should be that hard. You should be able to get it close with jets, PVs, and PVRs. I also wouldn't get too wrapped up with the O2 sensor. They can lead you in the wrong direction.
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Hi Phil,
You will see on the racingfuelsystems website, that there is a thread that mentions how an engine can still idle well with a PV plug fitted and NO main jets fitted as a test. Finally somebody has admitted that Main and PVCR does not affect idle quality. If your metering blocks have the IFRs up high, I would moved them down to where they "should be". Gary |
I agree - a lot of good reading. Spending a lot of time and posted there a couple of times.
But as to the comment that main jets won't effect idle quality - that may be accurate but not sure about the pv...I know I had that problem so my physical evidence says that pv does effect idle (maybe that's an indication of the problem?). Anyway, blocked off 2 more of the emulsion bleeds but unfortunately didn't richen up enough. Drivability is better and it's smoother through the mid range. Going to decrease the remaining emulsion bleeds from 29 to 21. |
Gary,
Regarding the idle jet relocation: I think it is a good idea but my reading of the materials says that the idle jet positioning is not directly impacting my lean issue. I read that it should help cars with low vacuum create a steadier flow and idle and off idle - I am not sure about the impact on the main circuit though; I think that 11" is not on the low side. I am reluctant to go for it - I break about 50% of the stuff I try to fix... |
Yes, I agree it will not alter your current problem, just something else to address.
I can't for the life of me work out why the IFRs ended up above the fuel level. Every other carb I know has ALL fuel jets below fuel level, and all air above, makes sense. The trouble with the larger Holleys is the same down leg booster is used across carbs from 650 to 1050. Can you see the signal strength at the main well must be not as good on the larger carbs. I like annular boosters for that reason, they sacrifice a little maximum airflow for a stronger signal. Remember, the carb won't flow 850 until 1.5 inches of manifold vacuum occurs, if ever. Have a look at how Troy from TMP carbs does his. http://www.tmpcarbs.net/carb_gallery_p1.html Virtually maximum venturi diameter, even egg shaped, with annular boosters. Gary |
i saw the video of the annualar boosters - they look like a big improvement over stock...
the guys on racingfuel website are hardcore drag racers i think so dont think everything (or alot of the things) they recommend will apply. however overall it makes me feel like that there much better carbs that my holley 850 xp. did you see the tmp weber blocks for holley 4150 design? pretty cool but i think "tuner" doesnt like them wondering what my next is going to be if the 21 emulsion bleeds dont richen it up...? |
btw, thanks for sticking with me on this Gary.
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If you don't mind spending a bit more money, I'd highly recommend Braswell carbs. Quick Fuel is good too. You can sell your Holley on Ebay.
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Gonna try and stick it out with this Holley but getting close to the end of my rope.
Are there any particular Brasell or Quick Fuel Carbs that you recommend? |
Do you need a choke? Prefer vac secondaries or mechanical secondaries? For your engine, IMO, I would reach for a Quick Fuel Q-750.
There are all kinds of carbs out there and we've pretty much tried every brand. I personally prefer Quick Fuel based on what we've seen on the dyno, and to narrow that down, the Q-series due to the range of tune-ability. Any way you go, I wouldn't buy a "universal" carb from a parts house (Summit, Jegs, etc.) I would contact someone who builds custom carbs: Patrick from Pro Systems, Dave Braswell, etc., so that you can get the right parts the first time and get help with tuning. We offer custom Quick Fuel carbs. We build them from parts based on the engine's specs. |
blykins
thanks for the info...gonna try a couple more rounds with my existing carb. Prefer mechanical secondaries; don't use a choke but maybe I should...it's a pain to warm this one up. |
If you need a choke, you'd have to go to an HR or SS series if you went QFT.
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