backfire on rebuilt 225 engine

had a chevy 350 after rebuild back fire checked the valves found one sticking part way open.if you have the covers off might want to check these.

wayne

 

I have same issue with a 71 willys cj5 with 225 v6, except it runs OK with the choke half on. Open the choke and it backfires though the carb or exhaust. It idles fine. I took the carb all apart and cleaned, reassembled and same problem. I didn't see anything wrong.Check distributor time and it is dead on. I just bought this jeep just got it running a few days ago when I found this problem. Carb is a Rochester 2 brl

Anybody have any ideas

 

Check for vacuum leaks, vacuum advance, make sure the points are set correctly and in good shape. Places to start.

 

As Nick said, especially if the intake manifold has been off. Very common to have massive vacuum leak from the front or rear of the intake manifold.

 

Hi and thanks for your suggestions, I have checked the dwell angle and set it to 30 deg and timing set to 7 BTDC. No vac leaks that are noted, although it idles very nice, not rough as though there is a vac leak. After setting the dwell it is a little better, very little.
I am stumped???
Ken

 

Sounds like your not getting enough fuel. Bronze filter in top of carb plugged maybe or in-line filter plugged or fuel pump not working properly etc. etc. is my guess.

 

I thought so also, installed new fuel pump and inline filter, removed the bronze filter.
I disassembled the carb and could see nothing wrong, jets clean, all passages clear. tried raising float level and engine acts the same. Reset to proper hight and stll the same.

Back fires through carb and exhaust.
Pulled one plug wire at a time. no diff.
???

May have to bit the bullet and buy new carb. hate to spend $150 for nothing if it turns out to be something else.

 

Just a note for you guys in the cold country....
I want to get it going so I can go wheelin, weather getting warm. Har har
Thanks for all your suggestions.
Ken

 

Did this ever get figured out? I have the same problem right now. Rebuilt 225 backfires and when you give it gas it dies. It seems to be just out of the drivers side. HEI not points. I pulled t-cover marks are on. Pulled v/c no problems. I can't figure it out.

 

Got it.
http://www.earlycj5.com/forums/newreply.php?do=newreply&p=871899

 

new to owning a cj. last time I worked on vehicles was 1968.. Having just received my new , old 1970 I of course wanted to clean her up. Had loud backfires coming out of the passenger side, felt the headers at each cylinder and they were cold, all it was believe it or not was plugs. Apparently It was running on the driver side cylinders only. I am sure I will need advice in the future , all the four wheel stuff is foreign to me as my mechanical skills are minimal. It would be nice if someone posted all the service spec's on the v6, I changed the oil remembering back in 1968 when almost all vehicles used 5 quarts. Everything else escapes my memory. Thanks everyone.

 

The FSM (factory service manual) is what we refer to as the jeep bible. Every jeep owner should have one for their specific jeep. Otherwise you will be getting things wrong and causing yourself more pblms.

 

i've had backfiring out the tailpipe due to air leaks in the exhaust manifold.

 

At the pipe or where it bolts to the block?