71 LA 340 timings moved!! how?? looking for help

[Shane pearce]

And this is with the initial set "where?" Have you pulled the dist. apart? Broken advance spring? PLEASE lose the word "dizzy." Thank you very much

Sorry.. sadly used to the UK language hence the Dist wording you don't like, bit like boot is trunk, bonnet is hood, Motorway is freeway, etc etc but I do try lol!!

Maybe I'm confused I thought initial timing was what I'm reading off the crank pulley at idle with timing light, which is 31 at idle (950rpm) is this not the initial? then there is the max advance (when weights and springs have done there thing? where I've seen up to 50.

But get this... just put back on the old dist cap and rotor arm and it started much easier, and it idled quicker without stalling (I don't have any choke at all, flap removed so got the odd splutter for first 60 seconds) (the old cap and arm had only covered 500 miles but changed it anyway when I serviced her)

Anyway checked timing again which I saw the 31 at 950rpm, revved it up all roughly the same and still seeing 50 when quickly revved to 4k ish but its much more revvy and seems to run stronger... whe nI say revvy I can stab the gas real quick hit 3k and back down to idle in around 2 seconds and there is now no hesitation or miss at all.......

So, Do I leave it as is? it does have a rather extensive build, high compression ratio, 418 stroker, cam is Comp cam XE274H 242 duration @.50 .492 lift and I did not build it so really don't know and sadly I don't know any tuners local that I would trust to even know what they are doing.

I have seen the odd muscle car running high advance but I know it don't make it right, or do I wind it back and see? it has way to much power anyway for the tiny 275/60/15 BF Goodrich its running lol!! I'm tubbed and relocated leaf springs so can run bigger but only 8.5" wide Rallye wheels and budget just will not allow new wheels and tires as need to change gearing and dumb 3500 stall converter and that's already costly..

 

[AJ/FormS]

The most important timing is power-timing. 50* is about 16 to 18 too much; you HAVE to back it up, no maybes, if you value that engine. Let the idle timing be whatever, but get the power timing down to 32/34 maximum for now.
You will need a dial-back timing lite, OR a timing tape, OR you will have to calibrate your balancer.
Then you just pull the timing out until no matter how hi you rev it,the timing no longer increases to past 32/34.Then let the idle timing be whatever.Now maybe you can run pump gas which I heard in your country is pretty low-octane.

And then once the power-timing is reset, you can re-connect the Vcan.
And then we can talk about the hesitations,bogs, or PT pinging,that might have developed.

 

[Shane pearce]

How do you know it moved? Are you SURE of what it was ? My 408 runs at about 30 degree advanced. You did not state what you think it should be set at.

I'm afraid not, I don't know what it was set at, I only checked timing after it did the rapid popping when I gave it some, which is not that often so could have been an issue for 100 miles but didn't feel it until I booted it some, I just assumed the timing was high at 32 degs initial and as high as 50 degs fully advanced.

I think it is 32 degs initial after the onset of the issue. How much slop is in the timing chain? I'm not a fan of the tensioners. Mine had broken the guide on the spring side right at the pivot. The flat spring had slid down to the bottom of the cover.

Correct, and checked belt for slack and got none at all..

How about a broken advance spring in the dist?

Have checked and springs are good

With no load on the engine it is common for the engine to want between 50 and 60 degrees of timing at cruise rpm. So you can't hurt it with a true 40/50 after 2500 rpm with no load.

This is also why the Vcan will someday have to be re-connected. The engine wants what it wants, and if you don't give her what she wants,she will complain about it, just not as loudly, or as often, as when it detonates.

I don't know what the big deal is, just put the power-timing back to where it's supposed to be, tighten the clamp and if it idles ok you're done. Then index the D housing to the block with a chisel mark,and keep your eye on it.
I mean 50 less 32 is 18 in the D. If you reset the power-timing to 34 then you will have 16 initial, And that is pretty close to perfect.
Now if it comes in too slow or too fast, well then some springing is in order. But your test shows only 6 degrees added from idle to 2500,and only 10 degrees added by 3500,and only 18* by blipping to guessing 4000; so that looks pretty tame.The curve appears to be pretty safe for the combo.

Thanks for the info, I guessed the vac advance was removed as its been mechanically curved by weights and springs? and I've read a few Mopar posts were they have disconnected there vac, I can only assumed as previous owner is so rude and up himself that if you question anything he did he threw his rattle out the pram!! so just gave up trying when he got mates to also troll me, they even stated that when I do put it up for sale in the future they are going to waste my time by pretending to want to buy etc... we are talking grown men here 40+ years, crazy child like antics or what.. I can only guess he was pissed he had to sell?? but who knows lol!!

So really here on my own and although the net is great it can be wrong and its very hard to explain in a forum sometimes.

The reason didn't just re-time it was I'd rather find out the cause of the sudden advance, or so I thought as it now seems it could well be set at these levels???? hope you understand my ways lol!! I just saw it like seizing a turbo and just putting a new one on without figuring why it seized in the first place, although I know its a bit easier to set timing over replacing a turbo... but anyway its dark now so tomorrow I'm going to drive it and push it some and listen for that popping, which I honestly think has gone now, just by replacing new dist cap and arm with the old ones?? I guess next step is a rolling road while they mess with retarding the timing to a more normal level.

Take a permanent maker and draw a line across the balancer, reset timing to 12 initial for now, tighten distributor and drive it.
Check balancer to see if line is straight across or if it shifted from the center, ring slip.

A distributor with mechanical advane will have some movement , depending on how light the springs are, large the bushing or slot is will determine how much.
It's also possible to reverse the polarity on the pick up wires, and end up changing the timing by a lot.

Key here is...did the idle rpm ever change from what it was before? or was it just performance that went away?.....32 idle would have it well above 1000 rpm at idle.

Hey, checked the balancer already and appears fine, but will do as you outline over the weekend.. the balancer looks like an expensive one although I know that don't mean it can fail.. its a Pro Sport bonded steel high performance application??

Thanks to all for your input and advise hopefully all will be well in due course lol!!

 

[67Dart273]

ARE YOU SETTING / READING THIS WITH THE VACUUM ADVANCE UNHOOKED?

 

[nm9stheham]

The 50 degrees is not 'power timing' as AJ calls it. It is with vacuum advance added, but that does not happen when you have the throttle wide open.

The are 3 separate advance types that you are working with:
- Initial advance typically in the 10-20 degree range at idle, with the vacuum advance hose plugged. The mechanical advance is 0 at this time. This initial advance is what you set with the timing light at idle.
- Total timing ('power timing') low to mid 30 degree range achieved at somewhere around 2500-3000 RPM, with the vacuum advance hose plugged (to simulate the throttle being wide open). This is the combination of the initial advance plus the mechanical advance in the 'dizzy'. The mechanical advance if stock is typically 20-22 degrees, so if you want this limited to, say 34 degrees, then the initial advance will be around 12 degrees.
- Vacuum advance timing: For the Mopar system, this only come when the engine is revved up for cruise and at light to moderate cruise throttle. It adds to the initial and mechanical advance and can move total timing up into the 50+ degree range under light throttle, cruising conditions. This is an important factor in fuel economy at when cruising.

Get the initial and total in line with what AJ has listed or you have some very real risk of detonation and engine damage.

 

[sireland67]

Why are you so afraid to move the distributor, just do it, you can always move it back to where it was.

 

[crackedback]

XE274H in that engine should run at 20-22 initial and 850-900 rpm. Verify the balancer hasn't slipped.

XE274 is 230 at .050 unless this is some other grind.

If it won't idle down, look for a vacuum leak.

 

[GeorgeH]

Just because you don't hear detonation doesn't mean it's not happening.

 

[nm9stheham]

XE274H in that engine should run at 20-22 initial and 850-900 rpm. Verify the balancer hasn't slipped.

The OP needs to be aware that he has to modify the distributor to limit the mechanical advance if he puts in 22 degrees of initial and uses the stock distributor; without distributor mods, he will have well over 40 degrees of total advance (even without tany vacuum advance), which is not wise.

 

[Tooljunkie]

Op,you stated you didnt know what timing was before this started. Im assuming the cap/rotor may have something to do with the popping. Reset your timing as others have stated, at least a few degrees.

 

[Max1196]

"as its very high revving and super quick up and down rev range." Your timing question, Are you sure that's the only thing in question, or is there more to it (bent stuff)?

 

[67/6barracuda]

If someone mention this already im sorry didn't see it. Possibly to light on the advance springs? If its acting up during rev's there's a chance the springs are not opening in a control manner. It could be bouncing around as its opening. Sometimes people the lightest springs they can find in order to get the motor to rev up quicker sure the advance cams open more aggressively but like I said it can cause the advance cams to bounce around causing issues.

 

[Shane pearce]

Hope we all had a good Christmas.... so today I thought I'd get back on it and while there replaced the MSD Blaster 2 for a Blaster 3 coil, checked timing once again and still sitting at 32 at warm idle, so I adjusted the timing back and its now sitting at 17 at idle.... so at that point I took it just up the road, as it was idling nice and sounding? I don't know? stronger? lol!! anyway not out the close give it a little bit of throttle and got a bloody loud back fire out the exhaust, then it stalled out on me... I was super low on fuel so put a gallon in got it to start after a few attempts, but now don't like to idle and the back fire is still there. god dammit!!! so now parked up as dark now....

Any ideas? and to add I noticed today a noise from what sounds like driver side valve cover, kinda like a rattle, not a knocking or tappety sound??? could this be related?? its been -5 temp wise here in England and its not been used in well over a week.. I'm guessing valve cover off, but other than anything obvious not sure what I'll be looking for?

I'd really appreciate any advice people, I must say of all the cars I've owned this is my first old old muscle and the steepest learning curve I've experienced to date!! I guess no experience with timing, carbs and coils etc is really screwing me over

 

[nm9stheham]

Well, the cussing part of the language is identical on both sides of the pond LOL

Have you rechecked the timing at idle after of this? The prior suggestion that the timing was hung up at a highly advanced position may be the answer. You have moved it back, now it may have ''un-hung-up", and may have jumped back to the old idle piston in the distributor and it is far too retarded.

And does it advance smoothly as you increase revs, with the vacuum advance line plugged? You're gonna have to put the timing light on it a lot to figure this out, IMHO.

No way to guess on the noise from under the valve cover... pull it and examine. Take pix and post of any thing suspicious.

 

[67Dart273]

I'd really appreciate any advice people, ,......................

What have you actually DONE, besides play with the timing? I outlined how to check timing marks which in my head is absolutely essential

in addtion, "there is" some possibility that the cam drive has slipped. If you read through some of the factory service manuals, there is a procedure in there to check that. Otherwise, simply "wrench" the engine back and forth and "feel" for the play in the timing chain while watching the distributor rotor. The object is to estimate how far the crank moves (linear measurement or degrees rotation) before the rotor moves. When you do this a few times, "back and forth" you can "feel" where the chain takes up slack

A backfire can be several things, including timing, an open plug wire or other high voltage "open," a valve hanging open or burned, or even just no/ poor shot from the carburetor accelerator pump

Download service manuals:

Free service manuals

and

MyMopar - Mopar Forums & Information - MyMopar Tools/Reference

I could SWEAR I posted this, I've done so "so many" times. CHECK THE TIMING MARKS!!! for accuracy. You need a piston stop. I made this one and have had it since the early 70's

You can buy them online, make certain you figure a way to lock the plunger so it does not move.

Unhook the battery for safety. Remove no1 plug, make sure the piston is "down a ways." Install the stop device, and "wrench" the engine around until the rotation stops on the device. Make an accurate temporary mark onto the balancer, under the TDC mark on the timing tab.

Rotate the engine opposite direction until it again stops, and make a second temporary mark under the timing tab. Now you have two marks, and true TDC will be halfway in between. If the original mark is accurate, that is where it will be

READ THIS ARTICLE, it has been posted here many many times...........post 4 of this thread. I would have posted this directly, l but the "new improved" software on this site sucks so bad I am not going to spend the time arguing with it

Ignition timing chart

 

[Tooljunkie]

Advance in distributor hanging up. Not much else will cause this.
Either vacuum or mechanical but someting is sticking and not returning to initial timing.

 

[Shane pearce]

What have you actually DONE, besides play with the timing? I outlined how to check timing marks which in my head is absolutely essential

Hi 67Dart273 very helpful post I'm sure I'd seen that pic but can't see a post from you with this???... sadly the internet and forums are hard to communicate on at best of times as so many people and misplaced info can be put out there.. mainly the "dreaded vac hooked up or not" I did say its NOT running vac advance at the start but sadly people still not seeing it.... why its not? I really don't know but there is a small bolt in the end of the hose the other end is connected to the Holley 750 so its not fallen off and remember I've covered 100's of miles with no issues and crazy power, took me a few drives to get used to the power as it just wants to spin out lol!! back then anything more than 1/4 throttle would result in tyre smoke at any speed.. anyways... my piston TDC tool as just arrived from Summit today, can't buy such a tool here in backward England... so will now follow your guide and links tomorrow as its 15:25 here and already getting dark and very windy :-(
I've done a little more than just played with timing... but countless times I was told to just "retard the timing already" but I wanted to figure why it seemed to have shifted but went ahead and did it after checking a few things., to which point I'm now very loud backfire out the tailpipes if I give anything more than cruising. I get one loud bang and I lifted!!, refuelled and same again, on a side note I've now noticed previous guy had white marked on the crank pulley where its at now at 17 at idle of 950-1000rpm.

I have made sure

1. the timing/crank pulley had not spun, which it has not as all timing marks line up when dist rotor is pointing at No1 and at least roughly TDC on No1 bore. but kind of knew this as its running bad so obviously an issue.

2. I have checked for timing chain slack, although its only covered around 1200 miles since full rebuild and not abused but to be honest I'm getting pretty much instant movement when turning engine back or forth so seeing zero noticable slack.

3. checked the timing mark was not jumping around as someone stated in regards to electrical work I had done, but guy confirmed the dist was not touched from the ballast to the dist and its not jumping about its got a very tiny amount of movement, but it increases and decreases smoothly.

4. I had checked the distributor for anything obvious but seemed OK but I'll put my hands up, not sure how I remove the insides to see the springs we speak of... right or more like wrong I assumed that..... they were OK as advance is stable and smooth increase decrease. My bad..

I've looked online and finding nothing, but was hoping for a step by step guide to rebuilding the distributor be it text and photos or video but all I find is Chevy/GM stuff.. Does that pick up wheel just pull off? heck I just don't want to break anything as very little is on shelf here in the UK unless you drive common American cars.. Vett's Mustang's, Firebirds, camaro's, 80's trucks, caddies, Dodge Rams, etc

Someone mentioned if my Dist is stock it needs work?? did not understand that? as although its a factory unit its converted from points to elec, weights and springs changed to get required curve? so not what I'd call stock??

May sound strange to bring it up.. but I suffer from an illness M.E which does effect my brain processing, speech (and text) get confused fairly easy along with cronic pain 24/7 so not asking for pity but a little "idiot cushioning" as also dosed up on fentanyl patches for back injury.. its safe to say my car is in better shape than me and both 44 yrs old... But I refuse to give up my passion and ownership of my life love of American vehicles.. I even have a disabled parking permit for the Duster lol!!

 

[Shane pearce]

Umm the silence is worrying lol!! anyhow today at long last the rain stopped so I could uncover the troublesome Duster.. I ended up pulling the dist altogether and found??.... totally nothing that seems out of place, shaft is free spinning with ease, weights in place springs in place, its pretty stiff to get them to move but they do move free, the vac seems to be seized but its disconnected anyway... I'm really getting to the end now :-( I'm guessing the issue is not ignition related at all.. since bringing the timing back to 17 it no longer idles once warm, its getting too warm IMHO, although temp gauge says all is fine, when I restart the start starts slow as if battery is dying, but its not.. so I guess advance timing back to silly numbers so I can at least drive it the 5 miles to long term store.. anyway here are some pictures but they tell nothing.
<iframe width="480" height="360" src="Duster Dizz Slideshow by Shane Pearce"></iframe>

 

[nm9stheham]

The symptom of the engine not cranking over fast is a classic symptom of too far advanced initial ignition timing. It will crank a tiny bit then almost stop, and then do that over and over again. Is this what you are experiencing?

 

[Shane pearce]

Hi... its fine when cold and idles, but once warm its does this and its a slow crank for a split second from the get go, like I said the engine just feels too hot for the short time it runs, it then constantly stalls, I struggled to get home lol!! thing is it was timed at 32 at idle before hence this post and now only 17.. so very confused... I'm thinking I may have a sticking valve causing the loud backfire. thing is engine has so much upgrades its hard to figure where things need to be... I've triple checked plug wires and they are correct

 

[nm9stheham]

Hi... its fine when cold and idles, but once warm its does this and its a slow crank for a split second from the get go

Sound like classic too much timing... that is one operating limit to initial timing.... advance ignition timing until you get hard start problems like this when hot, and then back it off.

BTW, do you guys over there go to winter-type fuels at the pump? Fuel blend changes in winter can make the fuel more volatile and cause some strange changes in behavior for carbed engines. Pump fuels are being designed exclusively for FI engines now... carbed engines be damned!

Dumb question..... do you have a timing tape on the damper so that you can make these readings of 17 and 32 degrees and so forth? If you don't have a timing tape, how are you reading these advanced numbers?

Another dumb question: If you do have a timing tape on the damper, are the advanced timing marks to the left of the 0 mark on the timing tape when looking at the engine from the front of the car?

And yet another dumb question: By any chance do you have an MSD ignition and are you using a 'dial-back' type of timing light?

 

[Shane pearce]

Sound like classic too much timing... that is one operating limit to initial timing.... advance ignition timing until you get hard start problems like this when hot, and then back it off.

BTW, do you guys over there go to winter-type fuels at the pump? Fuel blend changes in winter can make the fuel more volatile and cause some strange changes in behavior for carbed engines. Pump fuels are being designed exclusively for FI engines now... carbed engines be damned!

Dumb question..... do you have a timing tape on the damper so that you can make these readings of 17 and 32 degrees and so forth? If you don't have a timing tape, how are you reading these advanced numbers?

Another dumb question: If you do have a timing tape on the damper, are the advanced timing marks to the left of the 0 mark on the timing tape when looking at the engine from the front of the car?

And yet another dumb question: By any chance do you have an MSD ignition and are you using a 'dial-back' type of timing light?

As far as I'm aware its only the diesel here that has a blend change in winter, I run what we call Super unleaded – 98 RON best available here.
I have a Pro sport timing pulley so its marked 0 through 60 checking with basic timing light, + - and No1 lead no dial back

I'm using a normal Mopar 4 wire ignition box and stock 4 point ballast to a modified to elec Mopar dist and a MSD blaster 3 coil

 

[nm9stheham]

OK good on the timing light and the non-MSD system.

So to be sure, the timing tape's numbers go 0 on the left end and 60 on the right end on the top? I know it is dumb to ask, but am just making sure the tape is not on backwards....It is hard to catch little things over the internet.

OK, your 98 RON is similar to our 93 octane here. The formulation may still change to make the fuel more volatile in winter... easier to fire off when cold. (Diesel mix changes are a different thing.)

 

[T56MaxTorq]

The backfire occurred after the coil change and ignition timing adjustment. I’d put the old coil back on. But then you say you have a 4 point ballast. Any msd coil is designed to be wired to 12 volts, not a current limiter like a ballast. The ballast was originally designed for an older style coil that had a different amount of turns. You backfired because you don’t have enough spark energy (due to the ballast) at higher rpm to light the mixture and a full mixture dumped into the headers instead. Spark energy is weaker at higher rpm, greater number of cylinders/plugs, dwell setting, temperature, coil turns, primary voltage, etc. in this case, your coils primary voltage is probably around 6 (if I can remember back that far) when it needs to be 12. Which in reality it’s operating at 14 when the generator is helping charge the battery.

You need to bypass the ballast for the coil so it is fed 12v w/ ignition is hot. There is a lot of mopar ignition ballast resistor removal threads on the internet if you need a walkthru. You can also simply use alligator clips and jump the resistor at the terminal lugs but a full ignition system rewire is what I’d do. Recheck ignition timing after any adjustment and try again. I hope this is your issue

 

[Shane pearce]

OK good on the timing light and the non-MSD system.

So to be sure, the timing tape's numbers go 0 on the left end and 60 on the right end on the top? I know it is dumb to ask, but am just making sure the tape is not on backwards....It is hard to catch little things over the internet.

OK, your 98 RON is similar to our 93 octane here. The formulation may still change to make the fuel more volatile in winter... easier to fire off when cold. (Diesel mix changes are a different thing.)

Hey buddy.. its actual engraved into the billet pulley so deffo correct way. (wish I knew how to post a pic here as didnt work out above lol!! see if this works)

I'm also informed by Shell that there is no change to winter gas formula.

On a side note guy who posted after you has a valid point... wish MSD had advised this upon purchase as I'd bought the ballast that goes wit hthe Blaster 3, personally I thought it was just the raised lead connection that was different to the Blaster 2 Grrr!! the shipping will cost twice the price of the part, so may just go down the GM HEI module mod and be done with them Ballasts ;-)