Squeaking out of the rear pipes - yipes!

-
D

dartley

Well-Known Member
Joined
Jun 21, 2006
Messages
459
Reaction score
3
Location
NY
Car: '72 Duster.
Engine: 360 crate.
Exhaust system: TTIs, Flowmasters, new pipes from headers to mufflers (all new from engine back to mufflers, and pipes behind mufflers older but in like new shape).

This is odd. Since getting the car's exhaust changed the car is squeaking. It's not a metallic sound like metal to metal, but it sounds just like a mouse is squeaking actually, and loud enough to barely hear over the exhaust note.

I've been all over the exhaust and can not see any contact areas that are improper.

Does anyone have any ideas, or should I just go back and look for metal on metal? Thanks in advance,
 
Are the hangers clamps and all the bolts tightened up ? Maybe its a vibration of a pipe in a slip joint like into the muffler etc.
 
I plan to double check, but I don't think so. Thanks for your reply and I will let you know if that is it.
 
Nah there's nothing rubbing at all that I can see.

I think that the timing is way the heck out on it. Why? Because the engine is running rough, a bit hot (200 the other day) and does not breath above 3000 rpm. Also, the sound that I am hearing sounds more internal than any metal rattling noise. I'd had this noise in the past in another engine and it turned out to be timing then too.

But the problem is, these crate Commando engines - 306/300 in my case - have very ambiguous timing marks on the crank damper. I had not timed this thing in years and when I re-timed it recently I think I forgot which mark to set it too, and whether it's a mark for idle timing or max (3000 RPM) timing.

If anyone has one of these engines and can post a picture (of the timing mark, that is) I'd be obliged.
 
Could be a very small leak acting like a whistle. Check for carbon spots at the connections.
 
It's not a whistle. I said it's a squeek, but it's probably best described as a chirp, and it's most prominant at the tailpipes ... like "wroooommmmm ... blat blat chirp chirp chirp"
 
Sounds to me like the back pressure when you let off the gas is causing some sort of tension release which is causing something to come loose and squeak.

My guess is just as theirs, check the hangers, see if the rubber on any of them squeaks when moved around by hand. Also check the sleeving if you didn't weld the exhaust together. Maybe the clamps are just loose enough to allow it to slip around when every thing's just right.

Those are my guesses. Shake the exhaust around by hand, see what happens. Wiggle it side to side, front to back.. by the description it honestly does sound like somethings just ever so slightly loose.
 
Well timing is fine - got a new digital timing light with RPM and advance setting features ... should have gotten one long ago - took my wife to buy me one as a present.

Found that the initial timing was spot on at 10 deg adv, but the total was only 29 deg @3000. Seems the vac adv is not hooked right because hooked or blocked it makes no diff to total timing - the only way I can get 35 deg adv @3000 is to set init adv to 16 deg. It runs better now, but I can't get the idle down below 1100 rpm no matter what I do (was 800 before with init adv @10 deg).

Maybe someone who runs a street demon 625 can help me here ... the vac line is plugged to one of the bottom male fittings on the right(passenger) side of the carb - opposite side of carb from the throttle linkage. I had plumbed it that way because I did not see any other place to hook it to, but after checking vacumn there in comparison to the other fitting right next to it there is a huge diff. ...

The other fitting is giving me 15 in of vac at idle - this is where I plug my vac operated heater vent fitting (fac a/c cars has vac controls, not all manual). They work fine so this is the correct hookup.

The two fittings are identical and on the same axis (manifold vac?), but the one I have plumbed to the vac adv gives 0 in vac at idle and jumps to 15 in briefly on throttle blip, then back to zero at a steady 3000 rpm.

None of this has any affect on the chirping of out of the back tail pipes, so I will need to actually crawl around under there for a better check. But I am wondering if the noise might be detonation/preignition. Why I'd only hear this after the new exhaust though does not seem logical.

But if anyone could help out with any of this ... the vac hookup, the init adv idle speed and setting, or the chirping, I'd be obliged. Best regards,
 
Maybe you can get an adj. vacumn advance module or check arm on module that advances plate andfill it in a little to start advance sooner but advancing initial doesnt seem like a good idea Might cause a lean burn situation i,m not sure.
 
Refering to my own comment, above, restated here for convenience:

"Found that the initial timing was spot on at 10 deg adv, but the total was only 29 deg @3000. Seems the vac adv is not hooked right because hooked or blocked it makes no diff to total timing - the only way I can get 35 deg adv @3000 is to set init adv to 16 deg. It runs better now, but I can't get the idle down below 1100 rpm no matter what I do (was 800 before with init adv @10 deg)."

Well, I spoke to the Demon carb dudes and he agreed that my vacume attachments are correct as made. I really thought so. I think I am not seeing the vacume adv because it's already all in by the time it's at 1,000 rpm idle. Can anyone varify this? ... or can anyone tell me of another way to check the vac adv in the distr?

next, I tinkered with the timing and carb (I have not had alot of time because of more pressing issues), and through adj the carb I got the idle speed down to about 970, init adv with vac block or unblocked is 16, total is 33.

The engine is shuddering though and I don't even like running it ... it must be detonating and I am more and more sure that that is what the chirping is. I hope I don't bend all my valves.

My next step is to fill with 91 and add a booster to see if that helps. If it does than that's my answer and then I just have to back down the init timing. If it does not, than either the engine is already toast or I have no clue.

I do think it's tuning related though - I think that the TTIs and bigger pipes are breathing better and causing a condition that I don't know if I'm a competant enough tuner to account for.

Please, anyone who thinks they can help me out - I will be very very appreciative ... there are virtually no shops around here that work Mopars and I don't have much free time to tinker with the car. I really really like this car and would hate to let it go because I can't get it to run right. Thanks in advance.
 
Another update. On the way home yesterday I stopped and picked up a 16 oz. Octane booster (104 w/o MMT). Then I went down to the service stations, added the whole container and then filled 'er up with 8+ US gallons of 93.

Then I drove around a few miles slowly while the whole thing mixed with the 7 gallons of 89 that were already in there.

The result? ... it's f-a-s-t! ... marginally faster than the straight 89. But still chirps and idles a bit rough. So it appears it is not the timing that is causing detonation, since I figure the octane rating is now at least 94 and it made little if any difference. I am seeing in various other posts here as well that 16 degrees init timing is about what is to be expected when total is 33-34. I had always thought that we wanted 35 total with these engines and 10 init ... gues not.

So I went back to the service station I bought the gas at - they have a good reputation for their repairs in the neighborhood - and asked one of the mechanics to have a listen. He seems to think that it's missing on one plug and running lean at the same time. I had checked 4 of the plugs in the recent past - pulled two more or less randomly from each side - and they were all fine. But he and I agreed that it's probably the last plug I'd pull that is the culprit if any are - LOL.

The engine was way to hot for me to start pulling plugs after the ride, so I will attempt to get to that in the next few days or so. I will post back then.

If anyone has anything to add, please feel free to do so.
 
Checked all the plugs on Sat. Some diff between them, the best were dry and a bit brown and the worst 2 or 3 had just s smidge wet on them. These are AutoLites with only about 100 miles on them, but they all look pretty good; none grubbed up and none dry/white.

One thing ... as carefully as I pulled the wires, the second one - and the only one - got stuck on the plug and left the connector on the plug. The plug itself was one of the more wet ones, but still not gummed up.

I jammed the connector back in all the way, but I don't know if I'm gonna need a new wire set now; shame because they're good quality and not too used.

At any rate after all that it runs about the same as before. The chirp most comes in when the engine is settling back to idle after a rev-up. No oil coughs out, and no other symptoms. It's sounds like "vvvvvvvvvrrrrrrrrroooooooooooom, barble, barble chirp chirp chirp".

It's really weird.

EDit: I plan to replace just that one wire and see if it makes a diff.
 
You must log in or register to reply here.
-

Back
Top