May be possible stupidity
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Trailering
Joined: Oct 2021
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From: Oakland
May be possible stupidity
I have 78 ford f250 2wd 460 I put a Edelbrock air gap aluminum intake and Edelbrock 1411 carburetor on the truck. It ran very good when I put it in the garage. I checked and rechecked the timing 4 or 5 times to make sure I got it correct. However it’s back firing through the carb. The one thing I didn’t do when I used rags to plug the intake holes and cover the valley for clean up is verify that there was nothing left in the intake holes. My question is if I’m 100% on the timing is there anything else that would cause it too back fire through the carb?
FTE Legend
Joined: Nov 2015
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From: Angier, NC
Ok when "put in the garage" was the work done before this or was in the garage and the work done and now it back fires up the carb?
We need to know so we know what way to go for a fix.
If the work was done before and it was put away because of weather (winter?) and it now has a issue how long was it laid up?
If after the work was the dist. pulled for the intake / carb swap?
When dose the back fire happen start up and just running or when you press on the throttle?
BTW what is the working RPM range of the air gap intake?
IIRC it is pretty high.
Dave ----
We need to know so we know what way to go for a fix.
If the work was done before and it was put away because of weather (winter?) and it now has a issue how long was it laid up?
If after the work was the dist. pulled for the intake / carb swap?
When dose the back fire happen start up and just running or when you press on the throttle?
BTW what is the working RPM range of the air gap intake?
IIRC it is pretty high.
Dave ----
Lead Driver
Joined: Oct 2018
Posts: 7,825
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Check the firing order on your plug wires, and don't forget Ford uses a stupid order starting on the wrong side.
The only way I could see a blockage causing a carb backfire situation is if the rag held the valve open. if this is the case you should be able to bring it around until the intake valve is open and blow it back out of the runner with air .
The only way I could see a blockage causing a carb backfire situation is if the rag held the valve open. if this is the case you should be able to bring it around until the intake valve is open and blow it back out of the runner with air .
Hotshot
Joined: Feb 2004
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From: The Shenandoah Valley
Besides timing being off, a valve held open by trash, etc .... a lean mixture can cause back firing. If the truck is cool and even if the morning is warm, no choke can still lead to a back fire. A torn or wrecked intake gasket can cause a lean condition. The sudden pressurizing of the intake by a back fire blows any fuel mix already in the intake back out through the carburetor in explosive fashion.
Funny. I've had GMs and Mopars and Fords. In time, I came to the view Ford was the one which got it right.
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Trailering
Joined: Oct 2021
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From: Oakland
This all took place over a couple of days it was sitting out side the old stock carburetor wouldn’t hold fuel anymore if it sat for even a day. So I got the truck started and put it in the garage so I could change the manifold and carburetor when it’s running it runs good. Put it in the garage let it cool till the next morning and started taking stuff apart.
Tuned
Joined: Jun 2018
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From: Arkansas
Well you're still going to have that issue considering you installed an edelbrock
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Trailering
Joined: Oct 2021
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From: Oakland
The rpm range on that intake is 1500-6500 everything else is much higher. I figured that it might be possibly a little slower till that rpm range was achieved am I wrong in assuming that. The only other option would be the 2166 which is idle - 5500.
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FTE Legend
Joined: Nov 2015
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From: Angier, NC
So this started after the intake / carb swap if I under stand right and all because the stock carb would not hold fuel.
I think it would have been cheaper to rebuild / fix the factory carb but thats me.
Yes check the firing order first.
I cant see anything like a rag left in a port the cause but if you want to check with out pulling the intake do a compression test.
If a intake valve was being held open you would have no compression in that hole.
If you pulled the dist. recheck the timing with vacuum removed and plugged so no vacuum leak.
How did you adjust the carb once installed and motor up to temp?
Using a vacuum gauge, motor up to temp, timing set, choke off and idle set use the vacuum gauge and adjust the idle mixture screws a little at a time in or out to get the highest reading on the gauge. Turn each screw the same number of turns in or out.
Dave ----
I think it would have been cheaper to rebuild / fix the factory carb but thats me.
Yes check the firing order first.
I cant see anything like a rag left in a port the cause but if you want to check with out pulling the intake do a compression test.
If a intake valve was being held open you would have no compression in that hole.
If you pulled the dist. recheck the timing with vacuum removed and plugged so no vacuum leak.
How did you adjust the carb once installed and motor up to temp?
Using a vacuum gauge, motor up to temp, timing set, choke off and idle set use the vacuum gauge and adjust the idle mixture screws a little at a time in or out to get the highest reading on the gauge. Turn each screw the same number of turns in or out.
Dave ----
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Trailering
Joined: Oct 2021
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From: Oakland
I rebuilt the carb already to many times I think. I took the factory carb apart and didn’t take measurements on the internal parts and ended taking it apart probably 10 time’s more to get them set again adjusting a little at a time till it ran good another moment of stupidity.
The truck will not stay running or get up to temp that’s where my confusion starts not ever had that happen before. I haven’t put the antifreeze back in yet tried dry fire to make sure it fired up before I put fluids in. So I will do a compression check.
The truck will not stay running or get up to temp that’s where my confusion starts not ever had that happen before. I haven’t put the antifreeze back in yet tried dry fire to make sure it fired up before I put fluids in. So I will do a compression check.
FTE Legend
Joined: Nov 2015
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From: Angier, NC
So you cant get it to run.
Yea pull plugs and do a compression test just to make sure all holes got compression and when you put the plug wires back on check the firing order.
The order should be on the old intake, maybe the new one but not always.
Remember Ford has 1234 on one side and 5678 on the other.
The head farthest forward to the front is #1
Do you know if the motor has ever been rebuilt?
Did you do a "dry fit" (no gaskets or sealer) of the intake to motor / heads?
If motor was rebuilt and they decked the block and/or milled the heads the angle can be off between the heads and intake and not sealing.
What kind of gaskets where used metal pan or normal fiber gaskets? I dont know the Ford v8 motors and gaskets used.
I am going to guess / hope it is just a firing order mix up.
Dave ----
Yea pull plugs and do a compression test just to make sure all holes got compression and when you put the plug wires back on check the firing order.
The order should be on the old intake, maybe the new one but not always.
Remember Ford has 1234 on one side and 5678 on the other.
The head farthest forward to the front is #1
Do you know if the motor has ever been rebuilt?
Did you do a "dry fit" (no gaskets or sealer) of the intake to motor / heads?
If motor was rebuilt and they decked the block and/or milled the heads the angle can be off between the heads and intake and not sealing.
What kind of gaskets where used metal pan or normal fiber gaskets? I dont know the Ford v8 motors and gaskets used.
I am going to guess / hope it is just a firing order mix up.
Dave ----
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Trailering
Joined: Oct 2021
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From: Oakland
I did dry fit everything first. I didn’t see any problems. No the motor has never been rebuilt. I bought the truck in 1998 with 55000 original miles on it. It now has 98000 and some change. It spent the first 16 years of its life parked in a garage its soul purpose was to pull a gooseneck horse trailer to ID for horse shows. The next four years it move around Alaska with a lady that worked road construction she used it to move a house trailer from site to site. I’m the third owner and have had the truck ever since. The gaskets were from Edelbrock. The correct fire order 15426378 rotor rotation is to the left standing in front of the vehicle.
Thread Starter
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Trailering
Joined: Oct 2021
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From: Oakland
The compression is 135-145 in all cylinders. So If I understand correctly it is in the timing. So I set the timing with the 12 degrees BTDC So should I have set it at TDC to get the right tooth in the distributor then adjust timing from there. Is that correct way of doing it!