Backfiring engine...

I'm not a guru by any stretch, but two things come to mind - first, after firing her up, shut down and pull a plug to see if it's dry or wet (maybe the floats are too high, or needle/seat still has a bit of rust or dirt in there letting too much fuel through ... or a clog is keeping it from getting enough)
Second, check the timing, with all you've worked on, the timing may be out a bit and just needs a little adjustment to get her firing at the right time.

Pull the valve covers and see if you have a broken spring, stuck valve or bent push rod.

I'll just add to check and make sure your're getting 12v to the coil. Larry found I was only at 6v due to a miss wired balast resistor. She used to pop from the carb once in a while.

Go to basics first. There are only two reasons an engine like yours won't run.

1) not getting fuel or 2) ignition not firing.

First pull a spark plug wire from a plug. Pull back the rubber spark plug insulation from the internal plug connector. Brace it so it is close to a chassis ground. Maybe a bolt on the intake manifold. Then fire the engine and observe to see if the wire is grounding out.

If it is, reconnect it to the plug and go to the carb.

Take off the air cleaner. Climb in the engine compartment so that you can see down the throat of the carb clearly. Observe the choke flap.

Is it open or closed? Does it move freely with your finger?

Hold open the choke, look down the throat of the carb, operate the throttle. Does fuel squirt from the "accellerator jets?

If everything is good so far, if it is a Holley carb get some rags and place them under the fuel level screws on the sides of the fuel bowls.

You need a wide slotted screwdriver. Open the front one first. Ideally, the fuel level will be right at the edge of the hole. If it pours out and is obviously above the top of the hole, expect that the carb is likely flooding and look for the cause. Most likely will be debris between the float valve and its seat. You will need to disassemble the carb to clear it.

If this is a Holley carb, the original brass floats are know to fail and collapse. The current blend of ethanol in todays gasolene, accellerates that failure since the ethanol will slowly errode the brass floats away and they will fail with absolutely no warning.

If you haven't replaced the floats with plastic foam ones, then you should do that now also.

The safest thing to do is to replace the float inlet valves.

You can repeat this for the rear.

If the fuel bowls are empty or almost empty, expect a blocke fuel filter or even a blocked fuel pick up in the tank (since you said you saw rust flakes in the fuel).

These are the immediate treatments and if you get it running and it is still missing and/or running rough then it can be any multitude of aliments from minor to serious requiring an engine rebuild.

I hope you problem is minor and easily repaired.

I would pull the distributor out and check the shear pin. It sounds like at this point, it is probably bent (at least) which would throw off the timing. When the shear pin does finally go, your timing will really go bad!

Thanks guys for the input so far

It definitely is not a sheared distributor pin – I had the distributor out to check that, and once out, I noticed how bad some parts were, replaced what was bad, and installed the Pertronix kit.

The carb had some rust, but I had the carb apart, completely cleaned it, tested whether all internal lines were open etc… Every single part of the carb seems to work as it should, everything that needs to move, is able to move freely – the electric choke works. Btw, the carb has an “Edelbrock” label, but has “Weber USA” stamped in it…lol The car came with this carb.

I get fuel – tested and cleaned the lines, tested the mech pump, installed an extra translucent filter, to be able to check cleanliness fuel, and supply – both are OK. When I simulate a pedal push, the carb squirts.

My later attempts yesterday were unsuccessful – now the engine doesn’t even wont to start… :-/

Pulled distributor wire coming from coil, and cranked the engine – I get sparks, but can’t really judge whether those were good solid sparks, or weak ones. Will check whether I get sparks at plug level.

Could try to run a jumper wire from battery to coil too, and see what happens.

One thing that keeps me puzzled – such a Pertronix kit has two wires, a black one that needs to be connected to the negative side of the coil, and a red one that needs to be connected to positive side of the coil. Now where is the negative energy supposed to come from, or is it the coil itself that “produces” a negative field? I left the ground wire of the distributor connected for what it is worth…

I’ve been reading about jumping timing chains too, and if that were the case, then the TC mark should be off when #1 is at TDC, correct? – could double check that too I guess…

Lot's of good ideas. I'd check these two first:
Late ignition timing
Power valve

Based your description of the way it ran, I'd go with power valve. And checking is not just about seeing that it isn't ruptured, it's taking it out and pushing against a new one of same strength, to see if it's gone hard during the winter. I had a boat once that ran like you describe, changed the power valve in the Dominator, ran perfectly after that.

Didn't do much today...

Checked whether timing chain jumped or not - #1 reaches TDC on the TC timing mark, so it didn't.

Figured out the carb is an Edelbrock 1411:


As far as I can tell this thing has no such thing as power valves...

Found a parts list, manual, and tuning manual of this carb on the net, but not a single word about a power valve.

I'll see whether I can get the coil tested tomorrow.

If you have spark and you have fuel, it should fire.
Squirt some engine starting fluid in the carb. Not just a little, a ten second squirt, with the throttle plate held open so it goes into the intake manifold.

Verify there are no vacuum caps missing from the carb.

It should start, run for ten seconds then die. If it does, it is the carb or the fuel system.

You will need to know if you have fuel pressure at the carb connection.

If you do have pressure, fuel and spark, and it still won't run, the issue is internal engine.

How many miles does the engine have? You will have all of the issues to check for, including a failed valve stem, i.e., a dropped valve.

The hydraulic lifter CJ Clevelands have the reputation for the valves separating near the head of the valve.

Most likely though is that the valve seats are carbonized and you need to pull the heads and do a "carbon-valve job" as we used to say here.

I've now reread this thread, and I'm with PanteraDoug, try the simple stuff first. But if I read the post right, you haven't checked the timing? Putting the dist back "in the same position" isn't accurate enough. And yes, an engine with too late timing will backfire, especially when getting a little throttle, and will run miserably.

So, set the timing, before you start to tear stuff apart and buy lots of stuff.

Other good advice from above: yes, read the plugs. Wet with fuel means either too rich a carb or no spark. Bone dry means no fuel.

Last general advice: To check the carb, put on another, you probably have one on the shelf or a friend has? Same goes for dist/ign box. But one thing at a time, this is trial and error until it's solved.

But first things first, how's your timing!

quote:

Originally posted by Kid:
Didn't do much today...

Checked whether timing chain jumped or not - #1 reaches TDC on the TC timing mark, so it didn't.

Figured out the carb is an Edelbrock 1411:


As far as I can tell this thing has no such thing as power valves...

Found a parts list, manual, and tuning manual of this carb on the net, but not a single word about a power valve.

I'll see whether I can get the coil tested tomorrow.

carb as on my GT5S Kid, indeed ,Edelbrocks do NOT have power valves. Lucky i would say , as on my vette's Holley i had to deal with those little "bastards" , they can break from a backfire ! OK, now they have protection against back pressure : a one way ball-valve the size of a ballpen tip ....

Those Edelbrocks have a far more solid solution for that : the 2 needles with different diameter shafts, going up and down with vacuum , and this way restricting more or less the opening in a jet underneat.

So "no" vacuum is rich, alot vacuum gives "poor".When and how much is istalled with choosing the springs pushing on the rods against vacuum and rods diameters . Simple and solid !

Had the same problem with my Vette at the time ... and it was ALL ignition related . I also changed the breaker points with a Pertronix kit AND a new coil ( designed for the kit and needing full 12V feed ! ) .Runs perfect.

I installed a relais , giving full batterie power to the coil and operated by the existing ignition switch.

Good luck !

Gonna give it a go again later today, and double-check everything.

These days it seems hard to find a timing light in an auto parts shop. Looks like I have to special order one...lol.

Used to have one though, but gave it away as it spend years on the shelf unused, and now I need one...duh.

Tadaa, the old lady is running again.

The one thing I apperently did wrong, was set the static initial timing on 0°

The manual though, says to start with about -6°, some reading showed most people even go for up to -12°.

I set mine on -10°, and by the first key turn, the enige fired up without a single backfire, not even when I pushed the throttle, so timing it was indeed...

Next thing - how do I figure out what timing is the right one - how to find the "sweet spot"

I know George says to turn the distributor CW until the engine reaches the point where it no longer runs faster and faster, but I have the impression I can make mine run quite faster than it already does, and afraid to start driving with too much advance...

Any advice?

quote:

Next thing - how do I figure out what timing is the right one - how to find the "sweet spot"

Maybe visit www.tuningmadeeasy.com?

good news Kid ! ... and , just take a timing light and go up to 34...36° , no ? rev it high enough to be sure ALL advance is in . That's what i did, (i do not have vacuum advance).

Maybe...

Went for a ride, without firewall... Even in Belgian weather, it then gets really hot inside...lol The sound on the other hand was quite right!



Engine seems to run fine, although idle speed when cold is too high - need to fix that.

Yep, the front grill is missing, but am having the frame chromed again.

34-36 is higher than I would go...

quote:

Originally posted by No Quarter:
34-36 is higher than I would go...

don't know... with stock compression ratio and 98 pump gas as we have here ...??? and i jetted mine on the "rich" side....

How much total advance do you use ? and why not the spec 36°?

Quite simple, my engine builder said max 28 due to compression, cam profile etc. Whether he's too cautious, I don't know, but 1. I can't afford a rebuild, 2. (never thought I'd say it) I have enough power.

quote:

Originally posted by No Quarter:
Quite simple, my engine builder said max 28 due to compression, cam profile etc. Whether he's too cautious, I don't know, but 1. I can't afford a rebuild, 2. (never thought I'd say it) I have enough power.

Ok, i understand.... ..makes me wonder , so as soon as i have made a new exhaust ( stainless steel ) with sensor connections i have a dyno check... to jet my carb right .Would love to see what difference gives 28 and 36° in performance ... must do that !

Limiting a Cleveland to 28 degrees total advance makes no sense at all. It is taking the crispness out of the throttle for sure, as well as any kind of a top end at all.

These engines were designed to perform on 34 to 36 degrees of advance. You can't re-invent the wheel.

28 degrees is simply a statement about the octane rating of the fuel. Sounds like 89 (regular grade here) to me? I might expect this with a supercharger possibly.

The only way you would have to restrict ignition advance because of camshaft timing is if you are not running enough cam, i.e., too short of a duration.

Longer duration would reduce the tendency to detonate, not increase it.

In fact there are longer duration camshafts that have longer duration on the exhaust then the intake in order to reduce cylinder pressure by blowing some out of the exhaust.

34 total from 36 is the only compromise you should make. If you are running only 28, why bother to drive the thing at all? To me, that would be like driving a diesel.

I wish I had a chance to give you a ride in this "diesel"

You do your thing, I do mine. It was just a friendly caution, because too little advance means loss of a little power, too much means loss of all power

quote:

Originally posted by No Quarter:
I wish I had a chance to give you a ride in this "diesel"

You do your thing, I do mine. It was just a friendly caution, because too little advance means loss of a little power, too much means loss of all power

My car hauls a$$ and I think I'm at 32/34 deg total at 2500/3000 RPM...

Today I wanted to take the cat out for a drive, but…the stubborn thing refused to start…grumble, grumble, grumble…

I suspect the ignition again. I get sparks, but rather weak and imo pretty inconsistent. Seen the fact those Pertronix kits like a solid 12V, I tried whether a jumper wire from the battery to the coil made any difference, but it didn’t.

To be continued...

How annoying, right after you thought it was fixed. Are plugs black or wet because of lack of spark? Or dry because of lack of fuel?

as already mentioned Kid, do you have the right coil for the Pertronix you installed ?

Flame-Thrower 45.000 Volt 0.6 Ohm

Yup, wet plugs, but very weak sparks.

Puzzles me a bit why initially everything worked well, but going for one of those Flame throwers is indeed my planned next step.

quote:

Originally posted by Belgiumbarry:
as already mentioned Kid, do you have the right coil for the Pertronix you installed ?

Flame-Thrower 45.000 Volt 0.6 Ohm

Back in town today, went out for a new coil, came back with one of those Flame-Throwers (II, 45T volt, 0.6 Ohm), and made the recommanded electrical changes too (relais etc).

Turn key, and vrooooOOOO0000MMMM, a running engine again

Tomorrow it'll be test drive day, and I'll pull the plugs afterwards, as I still have the feeling the thing can run smoother (note to self - need to double-check timing too).

good news Kid hope test drive will confirm !

yes, amazing how those components really need eachother to perform....took me a long time on the '70 Corvette to figure it out ...but once Pertronix-Flame Thrower-relais it was perfect for the last years ... ( sold that car for the GT5S )

New coil and set-up definitely did the trick - at least so far...lol.

Me happy as it has been while I could really enjoy driving the cat, and the weather today just perfect for a little trip

Lots of thumbs up, and almost scared a biker of his ride, standing still in front of me under a bridge, and playing with the throttle of his Japanese Harley look-alike. One single push of the pedal was enough to make clear to him, he'd better stop trying to impress people with his baby toy