Engine rattle

Steveman · 10-31-2009, 05:31 PM

Hi there,
I have noticed that my 67 engine has a distinct rattle when its pushed hard, usually up hills or hard accelerating. I'm pretty sure its not the tappets as it definitely sounds like something loose. I've had other cars with tappet issues and it sounds different.

The only obvious thing I've found is the kick down lever, which seems to be very loose. I've fitted a bigger washer to it but it still seems to shake a lot. The reason I think it might be this is because going over a bumpy uphill section the rattling starts and stops in time with the bumps.

Could it be anything else? And if not, is the kick down lever normally pretty loose? Can it be tightened at all?

Any help appreciated.

jkucyj · 11-01-2009, 09:58 AM

I'd wrap the kick down in shop rags or towels and tape or sip tie them to it. Then go down a bumpy road or on e you know it will make this rattle on. Make sure it is just the kick down before you continue driving with a bad valve, you know what I mean. Hopefully it's just a rattle. If it is, I'd use a couple layers of heat-shrink (insulation used in wiring, Autozone, Advanced....) on the actual kickdown levers at the trans and carb. Then cut some rubber washers out of some hose or an old tire (anything rubber). Put one on both sides. That should take care of your kickdown rattle.

Steveman · 11-01-2009, 07:40 PM

Cheers for that. I'll give that a shot and see if it makes any difference. Hopefully not a valve as you say but it definitely sounds like a loose rattle if that makes any sense.

fordman289 · 11-01-2009, 08:06 PM

If it's happening only under load then it sounds to me like it's pinging. Does it sound like rocks rattling around in a coffee can? You may want to look at the timing and fuel mixture, or you can try running a higher octane fuel.

The kickdown linkage is always pretty loose, not a real precision fit. I doubt that is your problem.

Greg

jkucyj · 11-02-2009, 10:25 AM

You're right about the kickdown not being a very precision piece of equipment. But it's a more positive thought than internal engine noise.
So Steveman, if for some reason it's not the kick down, we need some more info. What size engine are you working with, do you have any mods? Also, I see you're in New Zealand (nice) what octane fuel is regular over there? Is it the same crap we have now with 10% ethenol? I had to go from 87oct to 91 to get the pinging to stop.
How old are the spark plugs? over a year.... replace them. I'd dust them off with some 100grit sand paper if their not to old. Just to get the carbon off. I do mine once a month. I also drive my big block like I stole it.

Steveman · 11-03-2009, 08:17 PM

I'm running the standard 390 with (I believe) a slightly different Holley carb set up. (can't tell you what model it is though - it came with it) I'm running it on 95 octane but we also have available here 91 and in some places 98 (but this is not advised for this car due to the ethanol content or something).

I have had trouble with it running too rich in the past and fouling the plugs. The plugs were new and I'd clean them monthly. Now its not running as rich as it was but its possible that its pinging if I've leaned it back too far?

For some reason when 'properly' adjusted one side would run lean and the other rich. So the mixure is set differently for each side. I've never really experienced pinging before, so presumably it sounds like a metallic rattle in the engine?

jkucyj · 11-04-2009, 05:47 AM

WOW! I wish I could get a hold of some of that gas! I'm sure you all pay for that premium stuff though. Normally... pinging from running to lean is found in the higher RPM's at wide open throttle. I'd say try to stick with the 91.
You haven't changed enough on the air/fuel ratio just by switching gas. There should be a model number on the choke barrel if you take off the air filter. Look that up on google or something and it will give you the cfm rating. A stock 390 should have anywhere from a 600-670cfm carb.
The screws on the sides do NOT adjust air/fuel ratio. They are idle air control screws and they adjust vacuum at idle. In order to actually lean the carb out (depending on model) you will have to replace the two small brass jets in the front bowl.
Example: My Holley 750 is running rich because I have a big 750cfm carb on an engine with only 370ci. It came with #70 jets in it and I will replace them with #66 or 67's to lean it out. Before any of this happens I need to install a wideband so that I can rely on an accurate a/f ratio instead of sniffing the exhaust.