One other question , since I went through this before figuring out what I did wrong , have you plugged the heat crossovers ?? I plugged mine and did not lean out the jetting and had a super rich condition . similar problem to yours with fuel sitting in the manifold . Pulled the crossover plugs out and problem gone .
Dale, It is very unlikely the idle recipe holes you have are going to cause wet flooding, same for the crossover plugs in the head-intake area (unlikely) . IN FACT A hot manifold can HIDE a rich problem by quickly evaporating the fuel before you see it. Here are some things to check. Use an insulated type 1/4" thick 1976 BBB gasket with the plastic buttons on 4 corners and 4 seperate throttle holes to support (sandwich) a warped carb, guard against perculation & heat soak. Torque the bolts to 75 INCH LB's or 6 to 7 foot lbs.. LOCK the choke valve open securely. An open choke can be pulled almost closed as more air passes in front than behind it and you can not see it happen. Throw away the wire clip from the needle. It often throws off the seating of the needle and causes flooding. Make damed sure you have the fuel pressure at 3.5 to 4.5 lbs with a .135 seat.(6 lb will flood it) Use a trusted or new float. Install the float piviot pin the proper direction (left vs right) with the curved end standing straight up. Make sure the ball is seated in the accelerator pump or it may "pull over" into the front barrels and flood the eng. Air horn gaskets range from .027 to .060 thick and some guys use two gaskets to compensate for warpage. This willl raise the rear meetering rods and may cause them to come completely out of the rear orfices (FLOOD). If it's warped too much, send it to someone who has an unwarping kit. you can then stop worring about warpage. I have the tools and fix all mine and my friends. YOUR CARB IS FIXABLE.
Gary thanks for bringing up two items I never thought of , #1 different thickness air horn gaskets and #2 that using a thicker gasket bringing the secondary metering rods up . I have had the secondary problems before and did not realize why , now I know how much to compensate .
Yes. The vacuum is high at idle and this pulls down the power piston. When you get a cam with overlap, the vacuum signal isn't great enough to do the job. I needed a lighter spring to make the power piston to come down at idle. The spring I used was one of an assortment that came with a Q jet calibration kit I got from TA Performance. As an update on my progress, I've reached a similar place that Dale he was at. My modifications have made the carb too rich. I'm in the process of trying to go smaller with some of the orifices. I went to 0.124" on the idle bypass air and pressed a 1/8" brass tube with a 0.096" hole in it. I've inserted the idle tubes I got from Cliff Ruggles and am now at 0.039" (maybe still to big? I still confused with this one because the tube was at 0.040" when I took the carb apart in the first place). I used the old check ball trick to reduce the lower air bleed from 0.080 to 0.072. I might try to plug the upper air bleed and try smaller again. I'm pretty darn sure that I don't have any vacuum leaks and I went as far as to take the intake off and install thicker gaskets with additional sealer around the intake ports. This did nothing to raise my idle vacuum from 10 in. At this point, I think that the only way to raise the vacuum is to tune the idle circuit correctly. When it runs closer to 14.7:1 a/f, I imagine it may pick up on the vacuum signal(?) I say this because the vacuum really jumps when you increase the idle speed slightly (at 850 rpm or so, I think) with the throttle plate adjustment screw. I could be wrong with this theory though... The thing that bugs me is that I probably should not have gone straight to 0.039 on the new idle tubes I got from Cliff. I should have tried something smaller, even though the "original" tubes were larger. I also wish I had a drill bit between 0.046 and 0.052 so I wouldn't have had to make such a big jump with the Idle down channels. Oh well, I've got a backup carb that I'm rebuilding... so I hope I get at least one of them running correctly. I had some success with my first attempt at the idle circuit mods on the first carb, but all of my other experiments have only resulted in a richer carb with no improvement with regard to the rpm drop when shifting from N to D. God forbid that I bite the bullet and actually pay for someone to set up the carb for me... I do feel that I'm getting close to figuring it out. We'll see...
I'm where your at too. Stupid thing is eye watering rich at idle. Vacuum readings are poor. Re sealed the intake. Blah Blah..Blah Blah. Thing of it is, its running better than the demon 750. Anyone have Cliff Ruggles book? I understand it has some ballpark set-ups by your build. If I post my specs, can anyone give me the numbers?
At least I have company when it comes to it being rich. I haven't done anything with it since I put the old carb back on. But am thinking of going back to the stock needle and seat in the modified carb to see if the larger .135 one from Cliff's kit is just too much.
I bought Cliffs book. Been studying it and trying stuff. Still to darn rich at idle. But............I noticed that the power piston is limited in travel on my 71 carb after I put the base on. I was reading how the 75 up has an adjustment for this. So I got to wondering. I grabbed a junk base and knocked out the plug between the mixture screws and discovered a screw that adjusts the stop. I had to heat it to get it to turn. Then I did my good base. Stay tuned as tomorrow when I re-assemble this carb, I'll fire it up in the stock position, then I'll drop it and see what happens. Will this help.............Maybe. Will this be another "learn from me what doesnt work"?..............Probablyou:
Ya know, I thought the travel on the '71 carb I modified seemed very limited compared to others I have. Maybe you are on to something here. :TU:
I've not been doing much on the car lately and I've been very slooow with rebuilding the 2nd carb. This one is really gunked up with deposits and I'm going to sandblast it soon. I measured all the idle circuit orifices and all had the same sized as my original carb (before I started messing with it) EXCEPT: - The upper idle bleed is HUGE... 0.065"+/- - The idle down channel is HUGE... 0.060" - Someone blocked the idle bypass by plugging the main body (above the base plate) Hmmm... I'm tempted to try this setup after the rebuild just to see what it does... but I can't imagine that NO idle bypass is a good thing. After this fails... I'm going to try to figure out how to re-size the idle down channel and upper idle air bleed to usable sizes (or what I believe is a usable size). I think It'll soon be time to call Cliff again and beg for input. ray: (someone's gotta be willing to give up a Buick recipe for a 455 and TA212-like cam... "Pardon me pal, but can you help out a fellow Buickian who's down on his luck?") As a recap... my original carb runs, but idle is rich and rpms drop 300 rpm or so from neutral to drive. I'm hoping to figure out a decent recipe to set both carbs up to. I've still not put more than 200 miles on since the rebuild so I haven't tried really nailing it yet. The plugs look good with a slight hint of detonation issues. I'm running a little Sunoco 112 octane with the 93 octane to get rid of detonation for now... Anybody know if press-in down channel restrictions are available anywhere? I'm currently trying to scheme a way to take a piece of thin brass plate and fashion a new restriction.
If he gives you some specifics, please pass them along as I am running the 212. I'm focused on my body work now when time permits. I decided to leave the tuning gremlins alone until after the car is painted. It runs pretty decent with the old carb on to get me by. :TU:
I'll do my best Dale. I promised one of my carbs to a guy in the UK with a similar engine to use for his break-in... if I can figure this out. I'm going to try to find some drill bits between 0.046 and 0.052 to do some fine tuning with the idle down channels. I'm thinking of trying to cut a small brass disk and solder it right over the original press-in orifice. Then maybe I can drill a 0.048- 0.050 hole and see if this cuts down on the richness. (crossing fingers)
