I've never really messed with Holley's other than an old 600 dbl-pumper years ago that whistled like a tea kettle. I've checked out every Holley parts list I can find and the numbers on mine don't come up, so I contacted Holley and after a couple of days they responded that the numbers I furnished didn't relate to any of their parts numbers. I'm attaching photos of the carb in question and need any information possible. Model number, cfm, specs, reference to a spec sheet online anything. The numbers on the front of the air horn appear to be 80504 and D305. The numbers 6R 4585 B are on the top, passenger side. Any assistance would be appreciated.
An 80508 is a 750 Vac secondary with a rear plate instead of a metering block. Everything else in the 805 list #s shows as an HP (racing) carb. Measuring the butterfly sizes should give you a good comparison as far as size goes, but that's not definite...
From the pics I see annular boosters, and a reverse idle circuit. Could be some factory application and not aftermarket.
I was wondering about the annulars as well. I remember some 80s mid size Chevy and Ford commercial trucks used carbs like that. I agree, probably OEM.
What is interesting is that it has a reverse idle circuit (turning the idle needles out leans the idle mixture) but it has annular boosters. I will look in my listings tomorrow.
thats either a wacky oem or some morphadite someone threw together.......looks like a plain jane 1850, til you see the boosters......weird
The numbers look odd, but the carb looks alot like the late 70's or early 80's auto parts store replacement for the Autolite variable venturi carbs. The reversed mixture screws are "smog era" for sure.
Are all 4 venturie boosters the same on this one??? Could use a bird's eye view of the topside with the choke plate open...
Will take photos from the top and post in the morning. So far I'm lost I've never heard the term annular boosters, so I need to do a little googling to figure out what you guys are talking about. The reverse idle circuits? Good/Bad?
Ok, a little reading got me up to speed on annular boosters, seems like a good thing for a street engine, where throttle response and torque are beneficial
It is possible to switch over to a regular 750 metering block.. Plus you could use the hi-po fuel bowls on it and give it that racer look..
Annular boosters are great for the street! I have a BG carb that has the interchangable boosters and that's what I'm using on it!
I assume you are saying that I could remove the current metering blocks, thus losing the reverse idle feature, and substitute the metering blocks from a 750cfm that has conventional idle mixture screws. How did you arrive at 750 rather than 600 etc.? I'm not arguing, but I don't know how to tell the cfm rating of the carb. Plus I don't know enough to tell if it's a 4150, 4160 etc.
Ok, as promised here is a top view, pass. side view and a shot of the front metering block. I noticed another number 7204 with an 8 beneath it stamped in the top of the front metering block. Don't know what it would refer to. There are no tags etc on the carb and it was purchased new, although some time ago.
I also have no listings in any of my many Holley books. Here's my best guess. It was most likely made on a limited run for someone in the aftermarket. It has a 600 cfm type main body. The annular boosters will reduce the cfm rating some to around the 525-550 range. It should be a decent street carb if used on a mild engine. If you have lots of cam the reverse idle circuits will probably be too lean and it will need to be modified. Hope this helps, G....
Sorry, I goofed! That one looks smaller than a 600... It probably flows anywhere between 535-585 cfm.... It is a 4160 series carb.. You can still do those same mods by using a regular 600 metering block on the front and use the hi-po fuel bowls from a 750 with vacuum secondaries.. If you remove the secondary metering plate and install a secondary block, it becomes a 4150 carb... The fuel bowl screws need to be changed to the longer ones like the ones on the primaries.. Hope that makes sence... I ain't feelin' to good..
The idle passages on a reverse idle carb are different in the body and the base. It's more than just switching the front block. I don't think it's worth the trouble to change it,I would just run it as it is and see how it idles.
It's possible... I'd at least try to remove the restrictor caps on the idle mixtures screws and fine tune the carb with a vacuum gauge....
"Restrictor caps" I'm assuming you mean the little white plastic pieces with the phillips screw pattern? They appear to have a stop on them and only allow approximately 1/3rd of a turn. When I tried to set the mixture with a vacuum gauge turning the screws had no effect on the level of vacuum. I think that part of the problem was that it was idling too fast at the time. I'll idle it down and see what I can do with a vacuum gauge again. This carb & intake combination are a bit odd and I first discussed it in this thread http://www.jalopyjournal.com/forum/showthread.php?t=212926&highlight=thermodyne The company made specific recommendations for a cam and I purchased the cam from Comp. They recommended approx. 12-15 degrees static advance and if I set the timing at that point it doesn't want to idle down to less than around 900 rpm even with the idle screw backed completely out. It seems like I may be having a problem with the carb returning completely to idle so I shortened the return spring slightly trying to get a tighter pull-back. Getting ready for a blizzard over the next couple of days then return to the battle and see if I can get the mixture and idle straightened out.
Ditto on that blizzard.. We're looking at 18 + inches here in Motown.. ... I knew the "big one" was coming sooner or later..