304 timing issue???

1978CJ5beast

1978CJ5beast

New member
man o man where do I start......two month ago I got a 1978 CJ5, at some point alot of time and upgrades where put into it. A few weeks after i got it home, i noticed it took quite a bit to get started and i had to hold down the accelerator to maintain RPM before it would idle and not die, not to much longer i noticed a popping sound in the exahust and it would back fire.....since then here is the list of what i had done, normally one fix would lead to another issue. so i will just list what i have done and what issues i am having as of today.

All new 1406 Edelebock Carrb
HEI with new 8mm wires
all new spark plugs, all plugs cleaned and free trash
new valve covers and gaskets
new fuel lines, fuel pump and fuel filter
new hoses all around
new timing set
new gaskets from timing set, water pump, fuel pump
so prior to today and a crap load of timing tweaking the V8 304 was still back firing from the carb, shifted the Harmonic Balancer and there was alot of play, so i got a new timing set gears, and chain....

we did everything by the book, line up sprocket dots, counted the links, lined up the harmonic balancer to the TDC mark, took #1 spark plug out found compression stroke, rotated HEI, .........

so after the timing set change and double checking the #1 again for piston head, its still back firing from the carb, the one last check i have to do is rotate the HEI 180 just incase i was somehow on the exhaust stroke.....

minus the exhaust system popping and what not, this thing ran fairly well up until about two weeks ago. I have found out this thing had been hillbillied and jerry rigged so badly i just dont think its used to having good parts and being tuned properly lol IDK. It went from amazing fun, tearing it apart and putting it back together but now im just getting frustrated.......i have been reading post after post on this same topic and I think because of that i have checked almost everything prior to writing this, of course i could have checked everything otherwise it would have found the issue and would be writing this

HELP
 

Does it get better or worse as the engine get hot
 
Mine did something similar...the guy I got it from replaced everything under the sun from the fuel system to most of the ignition system until he finally gave up and dumped it cheap cause he couldn't get it to run.. Like you I chased the problem for a few days unroll I finally found a hairline crack in the intake manifold, so when it was cold it did ok but as it warmed up the crack would get larger and make it worse..
 
That's a loaded question, before all the new parts as it warmed up the better it ran but then the popping and back fires started, so first we did a carb rebuild. Didn't change anything, changed all the fuel parts, pump hoses and filter, no change, said screw it and got a new carb and HEI and wires, got it to run and the popping and exhaust back fire was gone. But there was a timing issue, figured that was from the HEI install. Call the manufacture, read all the manuals..decided to check the harmonic balancer, well come to find out there was alot of HB movement with minimal rotar movement in the HEI, ie. lose timing chain....so opened her up, low,and behold lose is not strong enough a word, more like,the timing chain was like a rubber band, so changed that today. Got,it all tightened up and put back together, by the book, re-installed the HEI, did the whole 1st piston, dowel compression TDC thing....no,**** same thing, backfire through the carb again, now I will,say due to the thunderstorm that rolled in the one thing we haven't done since the rebuild is rotate the rotar 180, I pray to all that is holy, that we just move the harmonic balancer during the put back together phase and when the mark was,lined up we were on the exhaust stroke not the compression....but. Ugggg
 

No crack n the manifold, and again the backfire from the carb only came after we started rebuilding and replacing carb and HEI, so I'm sure it's a timing issue, but IDK just frustrated at this point, but far from given up
 
Is there any side play in your distributor shaft and have you checked your vacuum advance diaphram?
 
This happened when I first got my cj5 when it had a 304. I think what I did to fix it was recalibrate my carb and increase the throttle a bit. However, eldebrocks are finicky I have found. It's kinda hard to remember everything I did when it was screwing up. Can you take a video of what is happening and post it?
 

The only way I found that crack in the manifold was I noticed a very faint discoloration and it just looked odd so I hit it with a shot of brake clean and the idle jumped.. Just to be double sure I put some jb weld over it and it was the prob..but there are lots of things that can give you those symptoms
 
@sweet, 1st going to recheck for proper 1piston TDC, possible rotar rotation 180, I also read the same symptoms can be from way to lean fuel as well...this has not been played with since the install. We kinda took for granted the Edelebock, install and start up advertisement.....hope it's as simple as that, I'll feel dumb but I'll have alot of me parts and tuned right....I'll see about the video
 
Have you done a compression or leak down test? If not might be a good thing to do. You just might have a valve or valve train issue. Back fire through the carb is usually more mechanically related.
 
No, have not,,tested either, but minus the finger over the plug whole bumping the ignition, seems to be solid compression on all 8 cyl. The carb back fire only started after I started rebuilding the replacing the carb, then adding the HEI... Although a mech issue my initial trouble shooting is to start right before the issue started, ie carb, HEI and timing.

Thanks, I'm going to look into what it takes to test both, the more I know, means the more I can do later, if need be.
 

1978CJ5beast said:
@sweet, 1st going to recheck for proper 1piston TDC, possible rotar rotation 180, I also read the same symptoms can be from way to lean fuel as well...this has not been played with since the install. We kinda took for granted the Edelebock, install and start up advertisement.....hope it's as simple as that, I'll feel dumb but I'll have alot of me parts and tuned right....I'll see about the video
Click to expand...

Yah eldebrock aint no plug and play carb. Id go Holley if I could do it again, it's more forgiving.

And yah I'm in Marietta, ga.
 
I think you are 180 out. Just went through this on mine over the winter.
If you installed dot to dot as the instructions say to do, it is wrong!! They changed the way they mark the sprockets and didn;t change the directions... They now have you install dot to dot,,,,,but,,,, then rotate the motor 360* to be on the compression stroke for #1 right now you are on #6 compression stroke (180* out). It took me a lot of searching to find this out (I did the same as you). Pull your dist up and spin the engine one whole turn (360*) and put dist back in and I think you will be good to go as far as the timing go,s. Double check that you don't have any of the wires crossed.
 
Last edited:
69jeepcj said:
I think you are 180 out. Just went through this on mine over the winter.
If you installed dot to dot as the instructions say to do, it is wrong!! They changed the way they mark the sprockets and didn;t change the directions... They now have you install dot to dot,,,,,but,,,, then rotate the motor 360* to be on the compression stroke for #1 right now you are on #6 compression stroke (180* out). It took me a lot of searching to find this out (I did the same as you). Pull your dist up and spin the engine one whole turn (360*) and put dist back in and I think you will be good to go as far as the timing go,s. Double check that you don't have any of the wires crossed.
Click to expand...

100% right. It was 180 off, we figured it was being we just swapped the timing chain, and everything else has been quadruple checked prior to that. So now she rumbles nice and deep...still need to tweak the electric choke, opens to slow, and tune the mixture, still getting some deep popping sounds in the exhaust under the jeep. So I did a compression text ( all between 135-142) so more than Likely just need to replace to manifold gasket,....if its not due to the mixture...thanks for the help


Gotta love a CJ

Here she is all prettied up!
 

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1978CJ5beast said:
100% right. It was 180 off, we figured it was being we just swapped the timing chain, and everything else has been quadruple checked prior to that. So now she rumbles nice and deep...still need to tweak the electric choke, opens to slow, and tune the mixture, still getting some deep popping sounds in the exhaust under the jeep. So I did a compression text ( all between 135-142) so more than Likely just need to replace to manifold gasket,....if its not due to the mixture...thanks for the help

Gotta love a CJ

Here she is all prettied up!
Click to expand...

Nice picture! Looks like mine :)
 
I know right, but to get to that point, I had gotten a new carb, timing set, and HEI. Things I wanted to do eventually, cuz I did get performance part, just didn't think I would be making that many purchases this soon. But it is a CJ
 

Your engine looks great. I need to switch to HEI, I keep saying that and never do.
As to your slight popping, what is your Inital timing set at. When is it popping? at idle, crusing, accelerating, when you let off of it, ect.
 
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