I am putting a complete factory 2-4's setup on my '65 GS that I am restoring. My car is a 4-speed and this setup is off of an automatic car (as most are). My question is around the vacuum advance port on the rear carb--I know on most other manual transmission Buick carbs from this time frame that instead of having manifold vacuum on that port, they have ported vacuum (only has a signal when throttle plates start to open). Should the same thing be true for the correct rear manual transmission carb for a 2-4's setup? If so I can easily modify the one I have to be ported vacuum on the vacuum advance port. I know that backing off on the timing at idle on a manual trans. car like that makes it idle better than with the vacuum advance at full travel since there is no residual load on the engine like in an auto car.
Are you sure what you have isn't already ported vacuum? My rear carb is from a '65 and it is ported, unlike my '66 qjet which was manifold vac. Ported works much better for me with the mild cam because the idle speed is more stable with accessory loads.:bglasses:
What is the number on your rear carb? If you can post it, I will compare it to mine tonight when I get home. I was pretty sure that it was manifold vacuum like all my other AFB's, but I could be mistaken.
Mine is stamper on the front bottom right side 40516, under that is ?D5. My front carb is 3645SB, with CD5 below that. I wish I knew what these numbers mean.
Joe, Your carbs might be replacements... That #40516 doesn't show up in any of my Buick literature. I believe the SB designation was for AC Delco service replacements. I think the CD5 is a date code. Brian, The 65 manual makes no mention of the dual carb (rear) vacuum advance hose location being different for a manual trans. It does state, in the section on distributors that the source is manifold vacuum not ported vacuum. Here are the dual carb #'s; 3645s front, all 1964 - 1965 3634s rear, manual 1964 3924s rear, manual 1965 3646s rear, auto 1964 3925s rear, auto 1965 Which one is yours? o No:
I will look at the number when I get home tonight. I do know that my front one is the 3645s. I actually have two setups and they both have the same carb numbers on them.
I'm also curious as to what carb you have. When I got my setup, I was told the front carb was from a '66 and the rear was from a '65.:bglasses:
Both of the rear carbs I have are 3925s So in reality I need a 3924s on my car. Anyone know what the difference is in the 3924s and 3925s? I have known since I got them that it was an automatic carb in the rear, but it ran perfect on my car before I disassembled the car to restore it.
There aint much... A different metering rod and fast idle cam. Also, 2/32" less to the float level adjustment on the 3924. I would say, if they ran good the way were then leave 'em. :TU:
Mine runs good when warm, but stumbles on hard acceleration when cold and I've tried everything and can't get the cold operation to be as good as it was with the qjet. It also seemed to be running rich at high speed when I had it dyno'd. Perhaps it is not jetted properly, I need to check that now that I know it's the wrong carb.:bglasses:
I think my problems are all ignition related. Knocking & pinging is what I can expect if I get on the throttle to hard to fast. :eek2: I am hoping that a hot HEI converted distributor will cure my ills. :Brow: Joe, Your carbs may not be wrong, I just don't have much accurate info on the 66 carb #'s. I looked in another source book that has carb #'s for 66 but not any application info. :rant: Perhaps WildBill or Supercat can chime in here and assist me. They should know what's what on a 66. :TU:
Hi guys this post is for carb #'s from the 66 service manual. they are listed as follows: for the single carb setup: 3921s for the 401 auto 3923s for the 425 auto 3922s for the 401/425 manual For the dual carb setup: 3645s all front (auto and manual) 3925s for the rear auto 3924s for the manual Hope this helps on some of the questions Al :beer
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++ the Rear Dual 4-Bbl 3924s was used in 65' with gears --- the Dual 4 Bbl 3925s was only used with the Auto. Trans. as noted in the 1965' Buick Manual . I'm lkn for a 3925s if you want to part with it ! oneaero at Yahoo dot com Jon
