Will clean up idle and off idle crap running.
Will clean up idle and off idle crap running.
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.
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?
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.
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....