sredmyer Posted May 14, 2017 Share Posted May 14, 2017 Well I had the Monte out for a leisurely drive over to a friends house today. The friend was not home so I just decided to cruise around a bit and then head back home. Part of that cruise included an old country road that is flat and straight for a couple of miles so I decided to open her up. Unfortunately when I let off the accelerator she didn't slow, in fact she continued to accelerate. The engine was racing wildly, I never looked at the tach so I don't know how high it actually rev'd. Any way with in a few seconds I realized that the accelerator must be stuck so I put the car in neutral, shut off the ignition and guided her to the shoulder. The engine popped (loudly) a couple of times and continued to run even after I had shut off the ignition (dieseling I guess) and only stopped as I got the car to a stop. I sat there a moment thinking about what could have happened, pressed the accelerator a few times and it seemed fine so I attempted to restart the car. It started right up and immediately went to full throttle without me giving any gas so I shut it off and called a wrecker. Once I got the car home I looked a little closer at it but still do not see an issue other than the engine evidently slung the alternator belt as it was wrapped around the fan. It was not broken (nor damaged) it had just slung off. Anyway, I removed the breather and looked and it appeared the throttle was working fine but it also looked like the secondaries might be stuck open. I did have a flash light to really check but when I opened the choke plate for the secondaries, it looked like I was looking straight into the intake manifold. Has anyone had this happen to the Q-jet before? Quote Link to comment Share on other sites More sharing options...
sredmyer Posted May 14, 2017 Author Share Posted May 14, 2017 Ok, solved my own problem. Seems when I kicked it down the bracket that hold the accelerator cable actually pulled forward just far enough to trap the linkage for the secondaries. So my thought was right (secondaries were in fact stuck open) but unfortunately I was unable to see well enough down the venturi to see for certain what was going on. All better now car starts and idles just fine. However, the popping (more of a couple bangs actually) I heard when the engine was running away seems to have been the muffler...the beast is extremely noisy now Quote Link to comment Share on other sites More sharing options...
MCfan Posted May 14, 2017 Share Posted May 14, 2017 Man, when you stick your foot in it, you REALLY stick your foot in it! Glad the exciting ride didn't turn into a wild ride or something worse, Steve. Since your exhaust is now louder, I suggest you check your system over to find any potentially dangerous exhaust leaks under your car. You may have just blown out some baffles in your muffler(s), but I suspect you opened a seam or a pipe connection somewhere. Apparently, some unburned air/fuel mixture pushed out by a dieseling engine ignited somewhere in the exhaust system. It is surprising how much louder an exhaust system is with just a small leak. In any case, it sounds like it was more than a couple of backfires through your carburetor. Your '70 SS has 10.25:1 compression ratio and is more likely to diesel when shut off while hot, especially with an open throttle - mine does it on occasion with the throttle closed. I'd be more worried about the high revs on an unloaded engine that apparently occurred to throw the alternator belt. Hopefully, you killed it in time to avoid valve train damage. Glad you successfully diagnosed and solved the problem. Think I'll go out and make sure my accelerator cable bracket is tight ... Quote Link to comment Share on other sites More sharing options...
sredmyer Posted May 14, 2017 Author Share Posted May 14, 2017 Yes I am also concerned about the valves...specifically the springs. My understanding is these big blocks like to break springs when they get over rev'd. After putting belts back on, the car seems to run fine just very noisy...hopefully there was no damage caused. As to the exhaust, I now have a massive hole in the back of one of the mufflers (see picture). It blew it wide open. Now I really need some exhaust suggestions. 1 Quote Link to comment Share on other sites More sharing options...
GatorDog72 Posted May 14, 2017 Share Posted May 14, 2017 As to the exhaust, I now have a massive hole in the back of one of the mufflers (see picture). It blew it wide open. Now I really need some exhaust suggestions. Holy Smokes!! That's what I call a backfire!!! Quote Link to comment Share on other sites More sharing options...
monte70car Posted May 15, 2017 Share Posted May 15, 2017 I had some old flowmaster that broke down on the inside car would always pop we thought it was the valves. Quote Link to comment Share on other sites More sharing options...
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