The only difference in the carbs is that an ac car had a solenoid that increased the idle speed... should not be any difference in the accel. pump....
Something like that shouldn't matter then. I prefer to cruise with all of the windows down anyways. Thanks.
Update. Got a carb kit from a local Standard Auto Parts. I fixed the accellerator pump, and also tried to richen up the mixture. Still backfires. I had the hood open and had my father stand off to the side of the car. I put it in gear and put one foot on the gas and one on the brake. I slowly worked the gas pedal down putting a load on the engine while the brakes held the car in place. My father says the backfiring is shooting back up through the carb. I have a very weak spark and the back cylinder on the drivers side isnt even firing. Its not the plugs or the wires. The vaccuum advance is working and is not the cause of the backfire problem. Im thinking it may be the coil. Friday im changing the coil out and also running a compression check on the motor and hoping its not an intake valve.
I would change the cap, rotor, wires, and points/condenser. It does'nt sound like a fuel problem, sounds like misfire or cross fire. To replace the above is under $100 it is just good insurace for a better running engine.:TU:
Cap, rotor, wires, points, and plugs are all new. The condensor and coil are not new. I'll definately change those next. Thank you.
I had same things happening on my 66',it started to fire up the carb and than it lost couple cylinders.I have found 2 bad spots,timing chain has been 1 tooth off and resistor wire was toasted.It was giving 3,5V to coil.Long time in the past someone cut whole wire harness under dashboard and connected wires with copper connectors:spank: .Resistance wire isnt copper so it melted over time.It even has 2,3Ohm until you feed it with electricity,than it jumps up to 10,2 Ohms wich is bit to much.Check voltage on pink wire on coil,if you have stock coil there should be about 9,5V.If coil would be shot you would have weak spark on every cylinder. Just my 2 cents.
When doing a compression check on the Nailhead, what should my compression guage read for good compression?
Update. Compression check is showing 130-133psi on all cylinders. The coil WAS the cause of the weak spark. I put a new coil in and it ran smoother and fired on all cylinders. The backfire through the carb is still there when under load, and a carb rebuild will be next.
Brian, Now that you know what the compression is on all cyls.... you know that the engine can be made to run right, with tuning....Numbers above 90 psi are good to go with.... Go thru each system, one at a time untill you find all the problems and correct them.... Do the primary electrical first [points/condenser] then the secondary electrical [coil,rotor,dist.cap, wires, spark plugs] look for cracks, carbon tracks, wire leaks to ground, burned wires around exh. manifolds, breaks ect.... Then and only after the electricals are done then look at the carb.....
The photo montage of your 66 Riv GS is nice! is that a smokey burnout in one of the pics? impressive with the various issues you are tracking down. my stock 66Riv GS won't do a burnout. perhaps too much traction with the 17x8, 255/55's? I foot brake with the left foot to try and hold back the beast, bring the rpm's up to 1800 with SP kickdown, let go of the brakes for fun acceleration...but no burnout on dry pavement.
Thanks Doc. Everything else is good and in good working order. Rather than rebuilding this carb, what other options are there for carbs for this motor? I've been told by a few people to not put a Holley on a Nailhead. o No:
Brian, Pard, I have been running holleys on nailheads since the early 60s and would not have it any other way.... i currently have a 600 cfm ''shoebox'' holley on the 425 of my 64 riv. and a holley 1050 cfm 3 barrell on the 410 cu.in. nailhead that is in my 65 skylark GS... I ran a 850 and a 950 three barrell holly on a 401 that I had in a 64 lark that was a screamer... It is just like any thing else, for everything that you are doing to a car there is always some one who will not agree with it....but.... the proof is the results.... the holleys are easy to work with , reliable, and get good milage for their size and the performance is top notch....my riv runs strong, and gets 18 mpg... good for a 425 cu. in. engine in a 4800 lb car....:Smarty Back in the 60s holley was the premium carb for performance cars.... carter was making a 500-550 cfm carb, rochchester was about the same,,,,,, the only way you could come up with more flow was to add carbs.... hence 3-2s, 2-4s, 6-2s even 8-2s.... then holley came out with one carb that flowed more cfms than a lot of multiples,,,, 850 cfms, 950 cfms ect. and then the 1050 cfm 3barrel .... that was grandady to the 4500 dominator carb..... 1 carb, one kit to over haul, one set of linkage.... much better..... throttle response is crisp, and the carb is reliable.... GM, Ford, and Chrysler all used holleys on high performance engines and on truck engines..
I had read thru all of this and it does sound like you are getting a electrical problem going on. I did see where you had replaced the coil and it got better. It could be that the resistor wire is bad from the ignition switch. If you have the points set that has the points attached to the small round coil I have heard over and over again that those are not good to use. I would get the one that has two separate parts. If you have a dwell meter make sure that you have that right on the money. using a feeler gauge does not work very well. I think the dwell is at 30 for those. You can then try to set the dwell at 32 or at 28 and see if it gets any better. When you change the dwell you must reset the timing. The other thing that I would check is to see if the ground strap from the engine to the firewall is good. You would be surprised how important this wire is to the engine running correctly. Usually you will get a backfire from not getting a big enough pump shot. but if it just keeps going pop pop pop I would then look at the electrical parts. The points might be new but they might not be any good. Also check over the connections there you might have something grounding out or maybe when the vac canister is moving the wiring is getting grounded out. It could be that when you are on the floor the vac canister has moved far enough so as it does not get grounded anymore. I like the Holley myself. I think that you wont go wrong by using a 750 or 850 cfm carb Buicks always like big carbs.
So what about putting squarebore(holley) on the spreadbore(q-jet) manifold.If i remeber right Doc said that i should NOT put square even with flange....o No:
holley made a spreadbore, in 600 cfm [which to me aint big enough for serious performance, they are good on cruisers.] and 800 cfm. I dont think they are still in production but I see one on ebay from time to time... It actually would be just about as easy to get a sq. bore manifold and cut out the partitions between the front and rear barrels but you still will have to use an adapter because of the wider bolt pattern of the holley... but that works better than a sq bore to spread bore adapter....As for the cfm question,,,, go back and read my above post real close.....
Doc,i had no idea that there are square bores for nailheads....if so,now i know what will be my next 2 purchases. Btw do you have a decent square intake for a Nail?
Yep, I have a sq. bore intake that I have already removed the front and rear barrell partitions,,, making it alot better performer.... it weigh 40 lb for shipping purposes..... I have also ground all the casting flash off the outside of it... I will take $50 plus shipping...
