I took my "other" car out today after playing around with the timing and taking it on various runs. I can't seem to solve my problem which I thought was timing (it could be I may just ****). First off the car is a '69 Oldsmobile with a 455 in it. The car starts great, idles great, and under normal driving and accelerating its great...But, When I put her to the floor or close to the floor I get this rattle clanging noise in the engine. Can anyone give me an idea of what is going on? Is it the gas??? I run lead additive (stock unrebuilt heads) and octane boost. I still kinda am guessing timing, I have no light and pretty much am playing around with it. HELP Thanks Mike
it's called "detonation" and it means you need to put super in the tank instead of that cheap *** regular.
BTW lead additive is a waste of money,so are most octane boosters. spend your money on a good timing light instead. Crane makes an adjustable vacuum advance for that style distributor,around $22.00
Nope not regular...spending the big bux on super. Any type of fuel you guys use ie. amoco, shell...What else can I do? Thanks for the replys Mike
not to sound like a retard but are you sure its not some crazy exhaust vibration? ive seen and ridden in alot of cars that you think the bottom ends going to explode on the top end but itsjust a lose hanger on the head pipe vibrating against everything
Exhaust vibration is a good bet. Maybe a "carbon knock". Those 69 motors are high compression and low octane fuel-even today's super-doesn't feed them like they need. Carbon/deposits in the combustion chamber/valves/piston tops-can build up and then a piece breaks off and closes the clearance between the head and the piston--voila--knock. (It sounds just like a rod bearing knock). We used to warm up the engine then pour Dextron or Marvel's Mystery Oil or brake fluid thru the carb while revving the motor up to clean out the deposits, Followed by a high speed p*** on some deserted 2 lane blacktop. overspray
What you sre hearing is what the first hamber mentioned...detonation, or pre-igniton. This can be solved a few ways. For one use super high octane gas, which is pretty hard to find and expensive, but this may not even solve your problem. You probably just advanced the timing a bit too much. Back it off a bit and also make sure that your va*** advance is hooked up to a ported va*** source instead of a manifold va***. This will drastically change where your timing kicks in and ensure agreement and maximum cooperation between your carburetor and distributor. Also, when you mess with your timing, remember it changes the fuel needs of your engine, so adjust the carb accordingly. The more advance you give the spark the more fuel you are going to need (up to a certain point, at which the motor wont even run anymore). And of course the more you retard the timing, the less gas you will need. Another suggestion, if none of this works is to use head gasket shims to lower your compression ratio. However, im pretty sure you just have simple timing/fuel delivery problems. The way i set my timing since my motor is pretty hopped up (no factory specs), is to set the timing as advanced as i can get it and not get detonation at a full throttle (to the floor) romp while rolling in second gear. If it doesnt detonate then, then it wont ever.
Now that IS funny! It probably is the timing, but my buddy's 38 was making a "clanging" noise a while ago and it turned out to be the gear on the starter was sliding in and out as he drove. Weird deal - The starter worked fine otherwise but when he got on or off the fas it would slide in and out and make a racket as it hit at either end of it's travel/
A lot of guys have already covered it pretty well. $100 Test: One way of getting higher octane is to get yourself some racing gas. But at 5 or 6 bucks a gallon, it's pretty expensive. Free Test: Yup, retarding the spark should help. Another Free Test: You could also try trickling your garden hose into the engine while running at a high idle. Don't get too much water, as you don't want to hydrolock it. $20 test: Not to give too much of a commercial plug, but you could toss in a couple of bottles of Techron Concentrate (make sure it says Concentrate). That has been shown to safely remove the carbon from intake valves and combustion chambers. Even continues to work after you've refilled your gas tank because the softening/loosening process has alsredy started. But the water trickle method is free -- as long as you don't destroy the engine through hydrolocking it.
Thanks everybody for your suggestions, I have alot of ideas to try. I don't know what I'd do without the HAMB oh yeah pay a $60/hr shop rate and have parts I don't need bolted on and replaced. Thanks again guys!!! Mike
Mike? I'm not too familiar with Oldsmobiles but, if the distributer is in the back, loosen the clamp at the base of the distributer and turn the whole distributer clockwise a very small amount. Try the car and maybe do this 3 or 4 times. If the detonation gets worse start turning the distributer the other way. If the dist. is at the front a counter clockwise rotation will retard the timing ( which is probably what you need. Don't go too far. If I was you, I'd take the car to a mechanic and have him check it - it won't take more than about 10 minutes and it shouldn't cost very much. Worth the risk of daminging your pistons from the detonation? Good luck man and let us know what ya find.
Annother common clanging noise could be the torque converter bolts loosening up. Drop the dust shield (if its still there) and take a wrench to the three bolts holding the converter to the flex plate. If they are loose, remove them one at a time. Put a drop of RED Loc***e on the threads and put the bolt back in. Turn engine untill you can access the other bolts and repeat.
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