hey guys i have a lot of black crap in the carb my guess is due to it back firing threw the carb. my ?? is is this caused by timing if so how prone are the timing chaines to streatching and causeing this the last time i saw this it was on my gf's stepdads 351 and you could move the chain about a half inch

 

What year truck and what engine? Could be caused by several thing, including a stretched chain. BTW, all chains stretch under load.

 

all chains stretch but is your base timing set right???????

 

I would check your camshaft timing. The gears and the chain wear and stretch over use. The gears installed by the factory, aluminum with plastic teeth, were soft, designed to eliminate noises. The teeth often fell off, and the aluminum wore down, retarding the camshaft timing.

The chain accumulates all this wear. The following is an easy check to determine the amount of slack, slop or wear, in your timing chain.

It is not necessary to remove any components as long as you can see the timing marks clearly. It can be done with one person, but a second person can be helpful if the distributor cannot be easily seen while turning the crankshaft from the front of the engine. This test cannot tell if a chain has jumped; it can, however, tell you if there is enough slop in the chain to have let it jumped.

Tools: Breaker Bar with socket to fit the front crankshaft bolt

1. Mark the TDC or 0 mark on the damper clearly. Ensure the rest of the timing marks can be clearly seen; clean them if necessary. You may find it useful to scrape a little chalk over them to highlight them.
2. Remove the distributor cap and place it out of the way. You must be able to see the rotor while turning the engine with the breaker bar. It usually is not necessary to remove the spark plugs, but some high compression engines may require it to get an accurate reading.
3. Turn the engine in its normal rotational direction until the TDC or 0 mark is lined up with the pointer.
4. IMPORTANT: Do NOT turn the crank backwards just to line it up. Doing so will give erroneous results. You MUST rotate the crank in ONE direction only. If you overshoot, just go around again. This is where it may be helpful to remove the plugs.
5. Once the TDC and 0 marks are lined up and while watching the rotor, rotate the crank in the opposite direction. When the rotor begins to turn, STOP. It may help to have a helper push against the rotor's direction of rotation. (Remember, it will be going backwards at this point.) They can feel it begin to move more accurately than you can see it begin to move.
6. Note the value of the timing mark the pointer is indicating. It will be BTC, because you went in reverse of normal rotation.
7. This value is the amount of slop your timing chain has in degrees of rotation. Anything less than 10 is safe, but performance begins to fall off after 5.
8. If you have anything over 25, STOP driving that motor and get the chain and gears replaced! I have seen a motor run with up to 45 degrees - but I wouldn't risk it myself.

 

thanks for your help guys and it is an 460 in a 85 350 crewcab dually with all the holes for every hitch you could imagine in the bed so im sure its seen it fair share of abuse xit runs great most of the time but i having the black crud in the carb i want to make sure

thanks again
tony

 

how good is the motorcraft 4v carb on these engines i just found the tag on mine and that is what i have if its not a good one im gonna replace it rather then have it rebuilt

thannks
tony

 

Backfiring through the carb can be a leaking intake valve. Check compression.
Also, backfiring can be agrevated by a lean condition.

 

Backfiring through the carb can be a leaking head gasket. Check compression.

 

littleme13

What did you learn?

 

I can't imagine how a leaking head gasket would allow flames to pop out the carb but I'll bite. How does that happen? I know a leaking valve or burnt valve seat will cause you to backfire though. Or the EGR could be stuck open from carbon build up. That is a long shot though if you ask me.

 

When the head gasket is leaking between the cylinders this will happen.
littleme13 you need to do some basic trouble shooting. I would check the compresson and cheack your timing like banjopicker66 posted. You might allso check your distributer cap and plug wiers. Let us know what you find out.
Good luck
Bill

 

airharley, i havent been able to figure that one out either, it just doesnt sound right to me, but ive seen it with my own eyes on my truck...the carb was too lean and it would get a loud bang out the carb if i mashed the throttle....and as for carbs, ditch the stock carb and buy a good rebuilt 650 or 750 Holley vacuum secondary, dont buy some 20 dollar back shelf OEM holley that no one wanted in the first place....buy one thats in good shape and has adjustable bowl floats, and make sure the little idle mixture screws on each side arent loose in their settings....banjopicker went a little more into detail than i would have about checking for timingchain slack, personally i think that if the harmonic balancer moves at all without moving the rotor then the chain needs replaced, i could move mine 10-15 degrees before moving the rotor so i changed the chain and now it wont move at all without the rotor turning too, and the motor runs 100 times better....when u replace that chain use one for a 1970 460, it will add a little more power 4 ya...

 

banjopicker: that is an excellent method! one of those nice simple things that somehow I never thought of...

 

The carburetor on that engine should be a Holley 4160 series with a Motorcraft (Ford) PN on it. The accelerator pump is under the front float bowl and is prone to a warped cover. The proper adjustmeent is: hold the throttle wide open (engine off of course) and checkthe play between the loading screw on the end of the pump lever on the throttle body and the lever coming out from under the float bowl. Max clearance should be .015". The pump lever should pick up as soon as you begin to open the throttle. If it has been backfiring a lot, you will need a power valve too. Be warned, they are not cheap for these carbs, it is a 2 stage power valve. You will also need bowl and metering block gaskets, a pair of transfer tube O rings and bowl screw seals. Be very careful of the vacuum lines, they will be quite brittle, I know mine are. Check your vacuum advance also.

 

thanks for all your help guys and sorry i havent posted in a while was in the middle of moving so computer was down but i did find play in the timming chain only about 5 deg but since i have to pull the motor to replace ever seal in it due to oil getting very expensive im going to replace the chain and probably the carb while im at it as my budget grows so will the motor im guessing the head gaskets are ok have to check compression yet but it doesnt burn any oil and isnt losing any coolant but ill know more later again thanks for your help

tony