427 SO help needed fustration setting in

[priobe]

Hello all,

I need some advice for some issues that are really confusing me. He we go:

I am currrently finishing up my build and adjusting my webers in the process. I noticed that when I installed my windshield and hood I now here a multiple ticking sound coming from the trans tunnel area. I am pretty sure if the noise was always there I would have heard it. I would like to say it is detonation. The sound comes in around 2500 - 3800 RPm and my A/F meter is indicating 10.5 - 11.2 mixture (rich condition) . I have tried jetting the webers so that they are even more rich than what they arlready are and retarted the timing to initial 0 degrees with a 25 bushing. The noise is still there. I also have tried dumping in some octane booster with the same result.

One funny thing I noticed is that if I gradually increase the throttle the noise is not heard. I was currently running the 2 blue springs in the MSD distributor. So , I decided to use the larger silver springs to see if the timing was coming in too fast. This help alittle but did not solve the problem.

My compression ratio is 9.5:1

One other finding was when I retarded the timing the noise was still there. But when I bumped the timing from 0 to 15 degrees the noise got better. When I first noticed the noise my timing was at 12 degrees. SO it seems like the more timing I added the better the result with the large springs.

Can someone shed some light on this?


One other thing I am running a lighter flywheel and lighter pulley if this makes a difference.

Is it possible that my assembly is too light?


Please help getting fustrated

[Tim Brewer]

I doubt timing has anything to do with it, and definitely not the springs in your dist. It has nothing to do with your flywheel or pullys being too light, no such thing as being too light. If you're sure, (and sometimes it's hard to tell) the ticking is comming from down below, check starter/flywheel alignment. Might have to look under your car while it's running. Check rocker adjustment as well. It helps to have a mechanics stephascope to find odd noises. Sometimes you just got to keep searching, and good luck with those webbers.

[priobe]

I really dont think it is a noise pertaining to the alignment of the starter and flywheel. The noise only happens when under load. Rocker arms would make the noise at idle reving the engine.

I might have to remove the hood and see if the noise are the carbs popping on accelaration.

Thanks for the response.

[Rick Parker]

It could be a small exhaust leak. The 2 Silver springs give a faster advance curve than the Blue ones (you can mix them if you want). 10.5-11.2 is not rich, it is Lean. Get a stethascope and "probe" around, it may be something in your valvetrain too. Without it being under load I doubt it is detonating. Set your initial timing to be around 14-17 with total at 34.

[priobe]

Rick,

I thought the lower the number the richer the mixture?

"AFR
The Air fuel ratio is the most common reference term used for mixtures in internal combustion engines. It is the ratio between the mass of air and the mass of fuel in the fuel-air mix at any given moment.

For pure octane the stoichiometric mixture is approximately 14.7:1 or λ of 1.00 exactly.

In Naturally Aspirated engines powered by octane, maximum power is frequently reached at AFRs ranging from 12.5 - 13.3:1 or λ of 0.85 - 0.90."



Also the silver springs that I am using are the heavy springs not the light springs.

Furthermore, the noise is only heard under aload.


Boy I am really confused now!!!!

[wtm442]

If the ticking sound is faint, it might be a bad plug wire (coil wire, coil, etc) shorting to some metal part of the engine/car. Put the car in the garage, close the door and put towels over the windows. Start up the car and then turn all the lights off. Look around all of the plug wires to see if they are "sparking". Also check any wires that run parallel to each other (and are close to each other) for any distance.

I am assuming that the ticking noise speeds up as the RPM's increase. Yes? No?

"I noticed that when I installed my windshield and hood I now here a multiple ticking sound coming from the trans tunnel area."

I would assume that you have ruled out the hood and windshield as the source of the ticking noise. If not, put some pressure on the hood and windshield and see if the ticking volume or speed changes.

PS Edit - the engine is really not under a load if you are revving the engine in the driveway. Do you hear the noise when driving the Cobra? or just in the garage/driveway when its not moving?

[priobe]

The sound is only heard when driving. The more gas I give the more of the ticking sound their is. After 4000 RPM the ticking sound goes away.

If I gradually increase the gas, the ticking sound is not heard. When you drive the car with moderate accelaration the ticking sound is heard.

[blykins]

The lower the number on the A/F ratio, the richer it is. It's air/fuel, so if the bottom number is low, the quantity of air would be higher and it would be lean....the result would be a high numerical ratio.

[priobe]

blykins,

So at idle the optium setting should be 14.7:1.

What should it be when driving ?

[Excaliber]

14 and higher is pretty darn lean, 10 is rich, could cause black smoke, burning eyes, that sort of thing. MODERN fuel injected computer controlled cars run 14 or so, which is often called 'lean burn'. Takes a HOT spark and specially designed combustion chambers to get a proper burn going.

[blykins]

Some of the other guys can chime in here, but I'd stay to the safe side of lean, even when idling.

I'd aim for somewhere around 13:1.

[Jerry Clayton]

Priobe

If you want to call me at 630-365-6737 I'll tell you where to look

Jerry

[RICK LAKE]

Priobe There is no perfect number for A/F readings . Every motor is different,some run better rich while others like the lean side. For the most tork in a motor 12.4-12.7 is a good range to run. For max HP about 12.7 to 13.2 A/F readings. You are going to have to play with the timing also at the same time. The cam in your motor effects the webers alot more than a carb motor. All the throttle plate screws need to be at the same angle. You need a syncro meter that sits on the top of each throttle body and gives you an air flow reading, 2 of these would be better. What are your fuel pressure readings? You may have a lean out problem between the change over from the primary jet to the main jet. I am not a pro on this setup. The best thing would be to get the weber book at barnes and knoble book store and read it. When webers are running right, they will may 15-30 ft of torque and 20-40 hp more than a carb. Many article have been done on this. 12.7-13.2 is the ideal number for most stock cam motors, your needs a larger window to work in. 12.2 to 13.4. Cam is the big thing and overlap. That 14.7 read is the ideal A/F reading. If you try running this you would burn the motor up, on coasting or coming to a stop the number with FI is even higher but not at normal driving speeds. LM-1 meter will help alot, put you need to get the basic setup first. Syncro carbs first, then base idles mixture screws, then work on the cross over between primary to main fuel jets. I am not 100% how the tubes effect the A/F. Rick Lake

[priobe]

I will try to lock out my centrifical advance and report back my findings.

Also I will resync the carbs at idle and increase the speed to make sure they are still synced

Thanks for the post guys