Can anyone tell me which of the 350 Buick stock 4bbl intake manifolds flows the best, is the best overall part to bolt on a 1970 350 block, with AC and TH 350 tranny? I read somewhere that some years are better than others, as far as performance, etc. Thanx! Kurt
Anything pre-AIR/EGR will be equal. I think the 350 got the emissions stuff in 73, so 68-72 should all be the same.
Why is there sludge inside my intake? I had a little time this evening to tinker with my Skylark, so I was going to check the carb adjustments, since it's been running so rich. I discovered what looks like an exhaust leak, coming from where the thermostatic choke coil mounts to the intake. Black soot like you see inside a tailpipe. I unhooked the coil rod from the carb, and unbolted the choke coil housing. This is a 2 piece unit, with the coil, rod and upper housing being one part, and a "bowl" which sits in a hole in the manifold. The soot is leaking from between the flange on the bowl and the intake. Like everything else on this car, there is rust on this part of the intake, causing a slight cupping, and an area where the soot leaks out. I am sure this is exhaust. Why would exhaust leak from here? I looked at the inside of the intake, and there is alot of this soot inside it. I cleaned the area, and formed a seal with Permatex, bolted the unit back on, and am waiting for it to dry before I go any further. I am going to eventually replace this intake, especially with this rust damage. Do all 4bbl intakes have this hole for the choke coil, and why is there soot in my intake - exhast valve leak? I see that you say all pre 1973 intakes are exactly the same, I just want to be sure about that, since I am going to need to replace this rusted one. My 2bbl intake has an indentation for the choke coil to sit in, no hole in the manifold, I wonder if they made any 4bbl intakes without this hole. Thanks! Kurt
I went ahead and posted in the "Bench" forum, since it doesn't seem to get much interest here. Thought this may be a carburator related question, but since it's not specifically about Quadrajet, maybe I'm posting in the wrong forum here? Not sure where to post Intake Manifold questions. Thanks
Though it is not related to carburetion, it is carb related. You are seeing the effects of the rich metering in the intake since it is the exhaust that heats the choke coil in this application. The exhaust is drawn from the crossover in the heads, and directed through the intake to heat both the intake and the choke coil. The heated intake is used to reduce the required fuel from the carb due to thinner air, and it reduces distribution issues from a cold intake. Suggestion: unless you are looking for pure stock, try using the heated aire cleaner and a carb w/an electric choke. It will reduce the lost power from the extremely hot intake, and still not create problems with distribution in cold weather. Food for thought. ray
Thanks for the response, I got the same type of reply in the "bench" forum. I'm not sure what you mean by "heated air cleaner" and if I use carb with elect. choke, do I discard the choke coil and cap off the hole? Thanx
With respect to the choke revision, the electric chke replaces the standard hot air heated choke. You will br replacing several trouble-prone components with the electric set-up. First, let me explain the hot air set-up. The incoming air entered the air cleaner, where, if it was not close to 100 deg F, the snorkel valve would close, forcing the engine to breathe through the snorkel air routed around the exhaust manifold. The heated air cleaner consisted of a fitting around the exhaust manifold which allowed air to circulate around the pipe. The incoming air would be pulled around the exhaust, and heated by same. A sensor in the air cleaner controlled the valve, hence controlling the temperature. As the incomomg air reached 100 deg or so, depending on the application, the valve would start to open to the cooler air from the snorkel directly. As long as the incoming air stayed above the set temp. the valve would pull cool air into the carb. This hot air, during warm-up, was also routed through the exhaust crossover, allowing further heating to warm the choke coil. This system could be identified by the pipe at the back of the carb, which used the heated incoming air as a pre-heat source. The choke coil pulled its air from the intake crossover, through a calibrated vacuum leak in the choke housing. The resulkting super-heated air was used to control the choke coil opening rate, based on ambient air temperature. The trouble begins here. If any leaks in either the choke t'stat, where it SEALS against the housing. Leaks were common here, and created either a slow opening or incomplete opening due to the low temps encountered by the coil. The leak resulted in outside air being allowed into the housing, and mixing with the hot air, lowering its temp. Also, frequently, the customer, wanting the air entering the air cleaner to be as cold as possible for power, eliminated the control system in the air cleraner, reducing the temp of the air entering the choke housing. Other issues, such as plugged pipes at the choke housing, or plugged vacuum leak inside the choke housing caused its share of problems as well. When you install the electric heater, some tips: 1. make sure that the electric supply to the choke coil is switched by the ignition, preferably through the oil pressure switch, as the factory did. This is not essential. Just make sure that the supply is not connected directly to the battery. It will drain the battery, and prevent the choke from closing. Also, be sure that the seal between the choke plate and the housing is removed, as this connection will be the ground for the coil. One more caveat: do not assume that the heated air cleaner can be disconnected at this point. The heated air provides intake heating, promoting fuel distribution, and reducing the necessary time for warm up. Questions? Let me know... Ray
