I built the convertible I am currently driving in the late 90's and started driving it in 2001 or 2002. Ever since I starter driving it I have had a problem with spark knock on a light to mediun throttle after the engine is up to operating temps. I also have had some overheating problems, and from changes I have made to airflow past the radiator have made that managable. Fathers day weekend going to a run I had a muffler go to hell. I tried to get the same mufflers that I had used to replace them, but they were no longer available. When I built the car I went through a walker catalog and by size and inlet and outlets used an OE type muffler ( wanted a fairly quiet car). Since I couldn't get exactly the same muffler, I took the car to a local muffler and explained to Tracy what I was after. He called his supplier and ordered a couple of mufflers that they recommended. Since they were shorter I had him install they and make the pipes longer. Long story short, last night we drove to Hampton for a small show, the temps were down, and no more spark knock. I am guessing the OE muffler was too restrictive and caused these problems. Anyone heard of such things like this?
That's an interesting scenario. I'm curious to see some responses. And to your question, no I've never heard of this phenomenon, but there's a whole lot of stuff I haven't heard about.
I know some engines are incredibly sensitive to timing regarding both pinging and overheating....a 289 Ford being one. I could totally see that being your problem,now that you mention it.If the front end is working well pulling in plenty if air and fuel and combusting it,then the back half of the operation isn't holding up its end of the bargain,things are going to get jammed up,and where's all that heat going to go....?Its going to stay right in the motor and ping and overheat. I bet you saw a jump in power with the new mufflers too...? Scott Posted using the Full Custom H.A.M.B. App!
I have had mufflers collapse internally and cause that kind of grief, so a too-small new one could do it too, I suppose.
The engine is a 455 Olds, and they are not really prone to overheating, and are fairly forgiving to timing issues. The mufflers are my only answer, and I could see that if they were collapsed, but this has been going on since day one. I was a professional mechanic for yhears, and thought I had seen everything, but I guess not
Do you remember what your old mufflers were designed for? It is possible that you got a hold of something designed for a quite small engine and they just couldn't flow enough for the 455. Sounds like you put some miles on it, surprised you didn't destroy the exhaust valves. Glad to hear it is improved now.
Anybody here ever buy an old car with a flathead with single exhaust? First thing (traditionally with a still-running Ford/Merc) to do is go to the muffler shop, and fit it with 'TWIN PIPES'! Wow! Mileage gets better, acceleration noticeably increases, car looks/sounds like a hot rod...and the Temp Gauge is a point cooler! Flathead V8s make the best example, but backpressure in anything is worse than a nagging wife... Overheating...poor performance...cheated out of overall efficiency...then divorce court. 'Plugged-up' exhaust is a very real symptom here in Cali. We've had gasoline diluted with liberal spirits, exhaust systems compromised with catalytic converters, legalese applications from fuel delivery thru cam timing and ignition restrictions. Smog stations have esoteric checks for exhaust restriction cause-and-effect, not the least being 'leaded' fuel somehow inserted into the restrictive fuel port! (ergo, plugged up cat) History repeats itself: remember the ol' potato in the exhaust trick? When the engine wouldn't start, it overheated the driver...
Some mufflers won't prevent a pipe from being installed too deep and bottoming out on the back end. Could cause a lot of heat if just on one side and pushing half the exhaust through the crossover in the intake.
I know you know better, but were the mufflers that went sour put on backwards? And, as to a single exhaust, it is not about it being single but being physically too small to carry the volume of exhaust in that particular installation. Twice pipes simply increase flow. The same can be had by increasing size. AND, in some cases pulse flow is increased by singles, when the headers are built to create it. Exhaust is a black art. Most over the counter 'convenience' headers are a matter of more is better, and are not tuned to take advantage of the pattern that exists between the pulses that are the result of timing. Some free-flowing mufflers are also quiet. Noise is not correlative to power. The best sounding engines I have ever heard were 'Y' blocks with glass-packs; and in stock form were hardly war horses. My guess is that the manufacturer of the original muffler created the collapsed muffler for something other than a hugemongus Olds motor. I ran a 409 with turbo mufflers in a mid-seventies GMC pickup that sounded like a kitten purring but was a tiger when it came alive. I experienced no overheating even with the original sick-six rad and no shroud. I don't know enough about your installation to comment on timing or heating. Just the mufflers. If the new ones work have the numbers etched in the glass, or tattooed. Something that works is a godsend. A lot of combinations work against a man trying to make something that has never existed before. Sorting things out takes grit. Good luck on your quest. The car sounds like something a man could be proud of, enough to make it right. How about more pictures of it, for those of us who like Olds powered anythings?
You said mufflers so I assume dual exhaust. Maybe one side was not flowing or restricted and forcing the exhaust through the heat riser passage to the other side.
I had a 455 olds in my last truck. It had cherry bombs out the side, I did get a little annoyed driving long distance but, I miss that sound and that engine every time I think about it.
Restricted exhaust will cause overheating. Am a bit surprised it happened at part throttle. They must have been very small or something the matter with them.
My guess is that at part throttle timing curve, fuel mixture and back pressure ganged up on the cooling system. Might want to look at part throttle timing and/or fuel delivery now.
I don't know what they fir, I just got a walker caralog and got the largest 2 inch mufflers I would fit in the space. They had like a 19 inch can center inlet, offset outlet. I felt that with duals they would work, I guess I was wrong. Pinging gone and runs cooler now
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