Backfiring

[barnett468 418]

your timing is probably off and it may be jetted lean.

when are they glowing?

what is the timing at when they are glowing?

what are the answers to the other questions?

 

 

[Her69fastback 3]

The timing is at 12. They are glowing after it’s been running a little bit. Seams to be running rich to me. 

[Her69fastback 3]

It’s idleing high to me. Have to have it turned up to keep it running 

[1969_Mach1 333]

At idle the header tubes start glowing red?  I wouldn't keep running the motor like that until you have some solutions.  It's running too lean. ignition timing is too retarded, motor is running far too hot.  Are the timing markings on the damper correct?  Or has the outer ring slipped?

Do you have something simple wrong like a vacuum leak somewhere?  Have you tried to cover the top of the carb with your hands at idle?  If so, what happens, idle smooths and speeds up, engine dies?

[barnett468 418]

1 hour ago, Her69fastback said:

The timing is at 12. They are glowing after it’s been running a little bit. Seams to be running rich to me. 

this is not specific enough so we need more info.

are they glowing at idle?

are they glowing at high rpm when you hold the throttle open?

why do you think it is running rich?

what is the engine temp at idle and while driving at around 40 mph?

what is the outdoor temp?

 

if they are glowing red at idle, do the following:

disconnect the distributor vacuum line and leave it disconnected.

recheck the timing at idle.

advance the timing 4 degrees and listen to the engine rpm. if the rpm increases noticeable and the engine still runs smoothly, leave the timing there and lower the idle as much as possible then see if the headers glow red.

 

 

 

 

 

[Her69fastback 3]

Thanks for all the help.  Have to go to work. I’ll work on it Sunday again. Thanks again for all the help. It ran good with the two barrel in it. Just wanted to dress it up for her. With all your guys help I’ll get it back on the road for her . 

[barnett468 418]

where do you live?

if you live close to me I can look at it for you.

[Her69fastback 3]

I live in Kansas City missouri 

[barnett468 418]

44 minutes ago, Her69fastback said:

I live in Kansas City missouri 

Well unfortunately that is just slightly east of me by about 1500 miles, but hopefully you can improve it at least some on your own with info from here.

 

IDLE TIMING VS TOTAL TIMING (IGNITION TIMING CURVE)

The complication with ignition timing is that there is basically an ideal setting for idle, and an ideal setting for high rpm, and the stock distributors sometimes need to be modified slightly to achieve close to optimal timing throughout the rpm range, especially if the compression and/or cam has been changed from stock. If you get a tach or have a fairly good ear, I can help you with changing the timing curve if it seems like it will make a reasonable difference. There is another thread on this forum from another person that has all my posts regarding exactly how to do this this, but that thread is extremely long and a little hard to follow so I can whittle the process down into something more clear if you need to do this.

 

[Her69fastback 3]

Have only driven the car twice cents I have done the work. Once to have the exhaust hooked up. Didn’t have this problem then. The last time we drove it is when everything started to happen. The damper doesn’t look like it is bad to me. Everything is painted. I put a make on it at 12 degrees. The headers start to glow setting at idle . I’m on seven days a week at work for two weeks. So I’m not going to have time to work on it. I’ll try to answer all your guy questions. This is getting over my head I think. It my not be as bad as I think it is. Thanks again for everyone’s help

[unilec 57]

You need a piston stop to find top dead centre, then you can mark your damper.

 

[barnett468 418]

Dont stress over it. The glowing headers are likely just a timing issue as i mentioned. Checking and adjusting the fuel level is extremely simple also. i or someone else will give you step by step instructions on how to check and adjust the fuel level if it needs to be adjusted. The adjustment only takes around 30 seconds. No real need to worry about a piston stop right now. They are a handy tool but are usually not really needed unless you just want to know if your ring on your damper has slipped. A tachometer is far more useful and some timing lights have them. Some auto parts stores may loan them also. You can also buy just a portable tach for as little as $15.00, however, some of these may not work with electronic ignition like you have.

https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=tdwell+tachometer&_sacat=0&LH_TitleDesc=0&_osacat=0&_odkw=timing+light+tachometer

[Her69fastback 3]

I checked the floats this weekend. If you bump the side of the car with it idling gas comes out the site hole. I check the time by pulling the hose from the distributor. I will recheck it this weekend by unhooking the vacuum line at the carburetor & pinch it off. How many vacuum lines should I have hooked up on the carburetor? I have the big vacuum line from the back of the carburetor hooked up to the valve cover on the passenger side. The other one is hooked up to the carburetor for the distributor.i have one more & that’s for the transmission that’s hooked up to the back of the intake. I’m going the buy a vacuum gauge this weekend. Where’s the best place to check vacuum? Car is no power brakes . 

[barnett468 418]

2 hours ago, Her69fastback said:

I checked the floats this weekend. If you bump the side of the car with it idling gas comes out the site hole.

ok, as long as now gas comes out when you don't bump the car when it is idling, i would leave the level alone for now.

[Her69fastback 3]

I pulled the front bowl on the carburetor. It has 66s for the jets. Should I go up to 68s?  I’m thinking my kickdown linkage mite be making rumble back through the carb. When I took it loose it popped back . I was going to get the new jets tomorrow after work & see if that helps the running lean.

 Thanks again for everyone’s help. 

 

 

 

[barnett468 418]

13 minutes ago, Her69fastback said:

I pulled the front bowl on the carburetor. It has 66s for the jets. Should I go up to 68s?  I’m thinking my kickdown linkage mite be making rumble back through the carb. When I took it loose it popped back . I was going to get the new jets tomorrow after work & see if that helps the running lean.

 Thanks again for everyone’s help. 

 

 

 

the jets are not your main problem but since you have them, you might as well install them and see if they help anything.

 

[Her69fastback 3]

I thought if the headers are turning red at idle wouldn’t that mean it’s running lean? 

[1969_Mach1 333]

Possibly, but more common is ignition timing.  Your main jets are not influencing the A/F mixture at idle.  Most main jet sizes do not represent the diameter of the orifice, but the number 66 main jet has an orifice of 0.066" diameter.  That is much larger than the idle channel restrictors which is why main jets typically do not influence the idle A/F mixture.  Most Holley 4160 and 4150 series carbs have idle channel restrictor diameters in the range from 0.029" to 0.035" depending on the carb.

I have seen plugged or partially plugged idle channel restrictors cause extremely lean and poor idle conditions.  The motor will act just like it has a big vacuum leak.

I know Barnett has been helping you with this issue.  You say the idle speed had to be turned up high to keep the motor running.  Aggressive cams can cause that but I would not go down that road.  Is your carb new?  Are you familiar enough with it to rebuild it?  At some point you have to make certain everything is correct.  If all other simple stuff looks correct it might be worth opening the carb, freshen it up, and making certain all passages are clean in the metering block, main body, and base plate. 

[barnett468 418]

1 hour ago, Her69fastback said:

I thought if the headers are turning red at idle wouldn’t that mean it’s running lean? 

no, if you read my previous posts, they say timing. it is impossible for it to be so lean that the headers turn red at idle, plus the main jets have nothing to do with idle. my comments about it also possibly being lean were not related to the glowing headers as much as the timing was.

[Her69fastback 3]

I checked the vacuum today. At vacuum at crank was almost nothing. Started it  it was just below 15 when it warmed up it went to between 15&20. Vacuum advance is working. When I sucked on the hose the arm moved. I rechecked timing with hose unhooked from card & pinched off. Still at around 12. Still backfiring when you turn it off. I’ll get a video of it when I turn it off. 

[1969_Mach1 333]

A video will help.  For myself, I cannot tell from these posts if it's backfiring or you have engine run-on (dieseling) because the idle speed is too high or something is too hot.

Was the vacuum reasonably stable when it was between 15 and 20 inches?

[Her69fastback 3]

[Her69fastback 3]

Yes it is was. Have to have idle up so it will stay running in gear. The backfiring is coming out the exhaust

[barnett468 418]

2 hours ago, Her69fastback said:

I checked the vacuum today. At vacuum at crank was almost nothing. Started it  it was just below 15 when it warmed up it went to between 15&20. Vacuum advance is working. When I sucked on the hose the arm moved. I rechecked timing with hose unhooked from card & pinched off. Still at around 12. Still backfiring when you turn it off. I’ll get a video of it when I turn it off. 

ok, xlnt. there will be very little vacuum until the engine is actually running.

15 hg means you do not have a "huge" cam, therefore, your cam is contributing from very little to nothing to the popping sound problem.

now, your headers should not glow at idle with only 12 degrees of advance so maybe it is advancing a lot with the vacuum hose connected?

your timing marks may be off as i think someone suggested.

now, does the timing increase at idle when you connect the vacuum hose?

at idle, with the dist vacuum hose disconnected, advance the timing exactly 4 degrees and tell us if there is a noticeable increase in engine rpm and if it still idlres smoothly, or if you cant really tell if the rpm increased. you may have to move the timing back and forth from the current position to the 4 degrees more advanced position a few times to get used to the difference in rpm if there is any.

 

[barnett468 418]

ok, from what i can tell by the video, that after sound is likely either a timing issue or a throttle plate that is open too far or high compression, but it is definitely not jetting. It is sort of similar to "dieseling" that mach 1 mentioned, and dieseling is often caused by a throttle plate open to far, ignition timing, very hot engine, and/or high float level.

do you know what your compression is?