The vacuum secondary has everything to do with it. It won't work if it was a mechanical secondary. Apparently you just don't understand how this works. The only difference in a 750 with closed secondaries is the idle circuit in the secondaries. And the vacuum secondary carbs come with a leaner transition slot fuel circuit because they are more of a street carb. If it's tuned for the particular application it will work. I've done it on a heavy car with a stock 302.
Sheesh.. you can lead a horse to water.......... I should have dug this out of my bookmarks early on in this thread. Here is everything you need to compare physical dimensions between various Holley carb sizes. Sometimes the brain tricks the mouth.. errr, fingers.. into thinking they know what the heck they're actually talking about. http://www.lbfun.com/warehouse/tech_info/fuel & intake/CarbList.pdf Like I said in the above.. look at the differences between a 2300 series 500 cfm 2bbl and A 750 cfm carb. Almost EVERYTHING ELSE CAN BE CHANGED BECAUSE IT IS ALL BOLT ON STUFF.. WHICH WAS ACTUALLY DESIGNED TO BE CHANGED FOR EACH INDIVIDUAL APPLICATION. Aside from those items, emulsions, air bleeds and IFR sizing can easily be modded to suit the application. And THAT.. is what tuning a carburetor is all about. NOT just bolting it on, setting the idle speed and twisting the mixture screws without understanding the differences between IFR, transition slot exposure, and HS/LS air bleed requirements. Which ultimately leads to false interpretations of negative performance/mileage impacts of this carb vs that one. I also constantly see most people don't even understand the relationship between front and rear transition slot exposure in comparison to the engine combo's requirements. I fix this area a LOT as many don't get it right and chase their tails around while adding.. or even sometimes subtracting.. unnecessary pump shot duration/volume to lean the black soot from the pipes or cover up the holes. Some people can tuna fish.. but just can't tuna carb to save their lives. Not because they aren't smart enough, but because they don't spend the time to understand what's needed to get there. Anywho, I'm sure glad the OP finally wised up and bought the "right size carb" for his application since it will now be a torquey speed demon with super crisp throttle response and good gas mileage compared to that humongous 750 cfm giant he was originally considering. Plus he'd probably have had to jack the idle speed up to 1,200 rpm and get a big stall converter to keep from stalling out at the stoplights too. Would have been a big ole' fat turd. Wait'll you guys see the HP 850 I'm eyeing up for my little 331. Probably won't run worth a damn either. lol
Just picked up the carb, and it turns out its not a 650...its a 600 vac. sec. (Holley 1850). $40...and another $30 for a rebuild kit on my way home. Now if I can get this thing bolted on and remotely tuned...
That's funny that you think I don't know how a vacuum secondary works. You can disagree all you want, but if the O.P. had gone ahead and installed that carb on his 302. He would not have been be happy with it.
That carb will "do ok" for your current combo but you will be limited in tuning capability due to the secondary metering plate having no jets(only pre-drilled orifices). If/when you get more serious about future engine mod's these are a few complimentary parts that are well worth the few extra bucks. I've done/ran many over the years, helped a few members around here with similar mod's, and they just plain work. It'll turn your little 600 into nearly what that 750 carb would have allowed you right out of the box. http://www.summitracing.com/parts/qft-34-2 or this one is the one I prefer to use http://www.summitracing.com/parts/hly-34-6/overview/ http://www.summitracing.com/parts/knn-85-0400 Use a drop down base style air cleaner with the tallest element possible. Preferably at least 3" in height x 12" - 14" diameter and be sure to stay away from the dinky small diameter "cool looking" units as they don't help straighten the airflow before it hits the boosters. In fact, cutting the choke tower off and using the stubstack listed above could actually cause buffeting around the boosters and cause erratic A/F ratios with those small diameter setups. Also avoid using the filtered style tops as they cause similar disruptions in the incoming flow direction.
always run what you can afford if you have 70.00 in a carb that performs well that's a good deal nowadays carbs are like cam shafts and intakes everyone has an opinion what works best the main thing is rebuild it bolt it on tune it and enjoy the ride
Just finished rebuilding the carb. I had to chase missing bolts all over town, but I got it all together. Cleaned the garage and moved turd in. Mocked up the intake/carb/air filter on the bench... the air filter dont fit. Here we go again. I'll keep tinker with it to see if I can get it put together this week. Thanks for all the inputs guys. Northern
Install the intake and carb yesterday, but ran out of daylight for cranking and tuning. My son came over today to get it fired, and after an hour chasing plug wires, she lit right up. 5 minutes of tuning and it seems to run like a top. Water leaks all over the intake kept me off the street. I guess you're suppose to seal the threads on all those plugs... road test postponed till tomorrow. I'm not sure what to do for the kick down linkage. The carb has the lever for it, but it connects at half throttle. I dont know how to correct that connection. Any input?
can of worms # 2025..I ran mine without one for years...it just downshifts the transmission, I did this myself when passing or any other time I wanted to get on it hard.
On most older trannys the kick down linkage adjusts at wide open throttle use thread sealant on the plugs or on any bolt that passes through a water passage
You need one of these and will likely have to tweak the rod slightly to increase overall length.. https://www.holley.com/products/fuel_systems/carburetor_components/brackets_and_linkage/parts/20-41
Yep...thats exactly what I need! Thanks KC... Yeah...spent an hour last night re-pluggin the intake. Its not as easy on the car as it was on the bench... I have a pantry full... but I try to get them out 1 can at a time so yall don't run me off the forum.. lol
Was looking at the holley link for the extender... in the "Features" description, one of the key attributes for this thing... "Very Handy". The creativity of Holley's marketing department is overwhelming... that was just too funny to not share...
