Just rebuilt and backfires through carb?

[Twinwagoneer]

Total rebuild and checked TDC and timing what else am I forgetting? Should crank but doesn't.
Any thoughts?

[Stuka]

check the cam timing and the ignition timing. One of them has to be off for it to backfire through the carb and not want to run.

[billyrb]

I would think that timing is 180 degrees off. You may have the TDC on the exhaust stroke rather than the power stroke.....

[MountainJeep]

I just experienced this problem bringing a 87 Waggy from sea level to Denver. It would backfire through the carb on start up. I had to reset the timing to 20*btdc and lean out the carb to get things running right.

running 4bbl carb on rebuilt 360

[Smooshy]

When does it backfire, when starting? when giving gas?

[Twinwagoneer]

Well checked TDC and it was correct. Then tried moving the firing order around one pin ,nothing. Tried moving the dist one way than the other then it really blew Have good spark and fuel but still spitts up through the carb.Help

[fredws]

How did you check TDC?

[PAJEEPER]

Yep sounds 180 off to me your rebuilt carb may now have a blown power valve now due to backfiring.

[Kukur]

Mine did the same thing in Nov. after my rebuild... I was dead sure my TDC was correct... it was 180' off. I felt like a moron as my buddy rolled on the floor.

Then even with the timing a bit off... it ran rough. Like Mountain Jeep I had to really advance my ignition to around 20' to make it run right.

[kong]

After my rebuild, mine did that too. I wasn't a 180 off, but just had it retarded too far (about 90 deg).
I just eyeballed it and then it started right up. Here's what I did:

moved cylinder #1 to tdc.
then adjusted the distrib timing so the leading edge of the rotor was lined up with the cap contact of cylinder 1.

it fired up and it ran really rough. I just adjusted it from there.
Kind of rudimentary I know, but it was quick and easy.

Kong

[Twinwagoneer]

Well I tried the 180 on the last try and gas really flew so I was right on the TDC comp.stroke
Had to run and pick up the wife and wait for the fuel to evap. I am at the first step. Im at TDC the comp. stroke , rotor at #1cyl. leanned the carb out. Now what?

[mechanic58]

Did you have the heads surfaced? If so, your rocker arms may need to be shimmed. After surfacing the heads, you'll shorten the "X" dimension of the pushrod. When the lifters get pumped up the valves won't go all the way closed. Causes backfiring among other things.

[mechanic58]

P.S. The easiest way to diagnose this is to do a compression check. You may have cylinders with little or no compression...some may be fine. It doesn't always affect all the valves equally accross the board.

[Stuka]

are you sure you got the cam timing right? As it seams your ignition timing is correct.

[Twinwagoneer]

The head were not resurfaced but checked comp in all cylinders and were all fine. I* am at a loss, can not think of any thing that I missed these engines are one of the easiest ones to work on
and rebuild.The only thing I can think of is the cam.I will pull the vale covers off to see what is going on.

[Twinwagoneer]

Well took the vale covers off and everything is in line and all vales are openning and closing.
tried retard and advanced the distb. but no luck.
Spaying a big bullseye on the engine but have to find the bullets for the pistol right now while the paint dries!

[billyrb]

I'm assuming you have checked all the things listed below, but I'll ask anywho....
1. Have you checked to make sure you are getting spark at each and every plug?
2. Have you checked to make sure that your distributor is properly tightened?
3. Have you checked the inside of the cap to make sure you aren't experiencing arcing?
4. Is the cap tight?
5. Have you checked for a HUGE vacuum leak?
6. Could you have a problem with your Ignition Control Module?

[JeepBountyHunter]

Mine did the back fire crap tonight on me, left me stranded in a car wash. Had to get a tow from a flatbed....will hear from the shop in the am......but I'm certain the power valve is messed up because the last back fire was short of being a mini nuke!...Lit up that car wash bay and skearred a few people in the next bay over! Dang thing really sounded like it went out of time.....then again why not...it has 123,000 on it. I'm miffed, because I just had a lot of other things done to this Jeep, to have this pop up out of the blue.

[Twinwagoneer]

Check on 1-6 and double check. Changed out dist with another running one and carb to make sure.Will pull the engine and put old 360 back in
till I figure out whats wrong.I have a funny idea that its a wrong cam. Thanks.

[billyrb]

I wish you luck, my friend.

btw, on another note, you joining us for the East Coast Invasion in May?

[Greg Ordonez]

I saw something like this once,and it was plug wires in correct order- just wrong direction on distributor cap! (real easy to "check" and still be wrong).

[billyrb]

Twinwagoneer, did you ever figure out what was wrong?????