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DRLA 45 backfiring out of carb and exhaust (SOLVED)
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evanfrucht
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PostPosted: Mon May 10, 2021 9:26 am    Post subject: DRLA 45 backfiring out of carb and exhaust (SOLVED) Reply with quote

Hi, so as some of you may be aware I've been building an engine the last few months. I'm behind updating that thread and have a specific issue I thought I'd address separately. I started it for the first time yesterday and it went OK. Overall, many things that could have gone wrong did not and I feel semi accomplished. NO weird internal noises. Valve train nice and quiet. AND No Leaks! I did a couple things right I guess.

BUT I'm having a very frustrating and annoying time right now. I'll try to keep this simple...

Fired right up on the stand and sounds decent, but it is not running nearly as smooth as I would expect. Lots or burping/coughing through carbs and backfiring out the exhaust too at times... not actually shooting flames but you can feel/hear a larger pulse every so often. I also noticed cylinder number 1 throat was kinda burping coughing little tiny puffs of smoke here and there

I thought at first maybe I screwed up the valve adjustment, or something came loose... but that has been triple checked at this point and I'm good there. Cam dots are lined up for sure also. Firing order is correct too (that has been checked about a dozen times)

I had a timing light on it while I was breaking in the cam and at about 2500 RPM I seem to have major timing scatter (looks like 10-20 degrees variation?) The timing light is showing a LOT of scatter all throughout the RPM range actually. Does this make sense as the cause for my misfiring and backfiring and such? How much timing scatter is acceptable before it just literally runs like shit? Obviously you want none, but things are not ussually perfect..

This Is a Pertronix III SVDA distributor... I bought it on sale before I knew any better (give me a break will ya Laughing)

Now I'm very frustrated wondering if I have some shit ignition system OR if I have some other weird problems with the carbs or something.

What would you do to figure out what's going wrong?

The only spare distributor I have is the original one from my 67' beetle that goes with a 30pict1. Really wish I had more spare ignition parts to swap in... to verify issue before I just buy new ignition system.
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PostPosted: Mon May 10, 2021 9:46 am    Post subject: Re: New build, running rough, backfiring, suspect ignition. HELP! Reply with quote

10-20 degrees of scatter is way too much.

You can use the SVA distributor as a test. Just set it up to about 7.5-10 degrees BTDC and don't hook up the advance. It should idle smooth.

If you need to rev it, and hold revs, like to continue break-in, just advance the timing by hand and a light.


It will let you confirm the distributor you are running now is the culprit.
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PostPosted: Mon May 10, 2021 10:08 am    Post subject: Re: New build, running rough, backfiring, suspect ignition. HELP! Reply with quote

could be a few different things..like dead cam...yes dead cams can also be quiet....did you deburr the lobes? use cam shield?break it in properly and change the oil AND FILTER at the 35-40 min run time as should be done? IS THERE A CLUGED IDLE JET?( CLOGED OR PLUGED=CLUGED) ARE THE CARBS PROPERLY SYNCED FOR BOTH FUNCTIONS? GOOD PLUGS?GOOD WIRES? COIL CONNECTED CORRECTLY? VACUME LEEK?DIST .....GOOD GAS?ENOUGH GAS?INTAKES TIGHT?BANNABANNA IN THE TAIL PIPE? Shocked VOLTAGE?
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PostPosted: Mon May 10, 2021 10:28 am    Post subject: Re: New build, running rough, backfiring, suspect ignition. HELP! Reply with quote

mark tucker wrote:
could be a few different things..like dead cam...yes dead cams can also be quiet....did you deburr the lobes? use cam shield?break it in properly and change the oil AND FILTER at the 35-40 min run time as should be done? IS THERE A CLUGED IDLE JET?( CLOGED OR PLUGED=CLUGED) ARE THE CARBS PROPERLY SYNCED FOR BOTH FUNCTIONS? GOOD PLUGS?GOOD WIRES? COIL CONNECTED CORRECTLY? VACUME LEEK?DIST .....GOOD GAS?ENOUGH GAS?INTAKES TIGHT?BANNABANNA IN THE TAIL PIPE? Shocked VOLTAGE?

Yes it could be a million things. BUT I have done some simple diagnostics and it seems my timing is wonky (as in scatter.)

When I put the timing light on it at 2500 rpms i dont see a steady timing mark in the same place every fire. The marks move around as much 20+degrees every time the light flashes. So much so it would basically impossible to set inital or full advance on this thing with any sort of accuracy.

I did use a good amount of the supplied red cam lube from Web Cam. I used a good break in oil and overfilled it almost an extra quart. I did not let it idle at all and ran it for 30 minutes at 2000-3000 rpms, even though it was popping and backfiring bit the whole time. I would hope the cam ain't screwed already. RUNNING Web Cam 252 on EP12 with CB Ultra Light lifters. Didn't mess with the lobes but inspected the cam carefully and Web Cam does debur them properly in house. I did polish the lifter faces tho.

Gas is brand new. I plan to change oil soon but I havent got that far yet lol. Valves been triple checked. Rebuild carbs with the parts and guidance from McDragracer(Rick) the Dellorto guru. He advised me on jetting to start with and I bought all new jets and carb kits from him. New bearings, etc. Sodablasted and ultrsoninic cleaned all parts and careully inspected to make sure no blocked passages. Set float height per specs. Set the idle speed screw for both carbs so that throttle plates expose 1/2 of the first progression hole. Then roughly hooked up linkage based upon that for initial startup ( I have the snail sync tool but I was trying to break In cam so I havent been able to let it idle yet to fully sync carbs.) I've heard using the snail at higher rpms can break the tool? Bypass screws are in all the way currently Idle mixtures are out 4 turns.

Does not seem to have a vaccum leak, as Im almost postive I would recognize that immediately. This seems different. The throttle responds very quickly and revs up and down nice and crisp. Overall it seems like it wants to run well but the timing is shit... atleast that's my hunch. However my lack of experience leaves me a little in the dark here.
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PostPosted: Mon May 10, 2021 10:51 am    Post subject: Re: New build, running rough, backfiring, suspect ignition. HELP! Reply with quote

any times Ive found that can be timing lights or wires....or both. Ive never seen it affect any thing at idle. take off cap and see whats jiggling around,slop play, loose missing springythingy. you can also just throw in a nother dist... also.. take off the reluctor wheel and rotate it 90 degrees do this 4 times to find the best running position.... mine had a rough running position and 3 good positions...I dont have a clue why.
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PostPosted: Mon May 10, 2021 11:13 am    Post subject: Re: New build, running rough, backfiring, suspect ignition. HELP! Reply with quote

mark tucker wrote:
any times Ive found that can be timing lights or wires....or both. Ive never seen it affect any thing at idle. take off cap and see whats jiggling around,slop play, loose missing springythingy. you can also just throw in a nother dist... also.. take off the reluctor wheel and rotate it 90 degrees do this 4 times to find the best running position.... mine had a rough running position and 3 good positions...I dont have a clue why.

You say you have the same distributor and moved the wheel around? This is the 009 SVDA style pertronix III, not the billet one. Which one do you have? I'm asking because reading stuff online I see that the billet version has much better reviews, where as people report having issues with the 009 style body ones.

It could maybe be the wires somehow but I don't think so. I assembled wires myself with proper crimper using a roll of this stuff https://brillman.com/product/7-8mm-cotton-braid-spark-plug-wire/ I have 12mm NGK plugs in the 7 heat range, forget the exact number. I use this same Snap on timing light on my other car and it shows the timing mark literally in the exact same spot every flash. That's what's makes me suspicious
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PostPosted: Mon May 10, 2021 12:01 pm    Post subject: Re: New build, running rough, backfiring, suspect ignition. HELP! Reply with quote

If I'm going to hook up my old distibutor with points is there any problem hooking it up to the Flamethrower III coil (0.32 Ohm) or do I need a stock blue coil?

Also pretty sure I read somewhere that people have experienced the flamethrower 3 pickup working better with a normal coil ( or that it doesnt work properly with the matching coil Pertronix says is supposed to go with it???) if anyone knows anything about that please enlighten me
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PostPosted: Mon May 10, 2021 12:49 pm    Post subject: Re: New build, running rough, backfiring, suspect ignition. HELP! Reply with quote

evanfrucht wrote:
mark tucker wrote:
could be a few different things..like dead cam...yes dead cams can also be quiet....did you deburr the lobes? use cam shield?break it in properly and change the oil AND FILTER at the 35-40 min run time as should be done? IS THERE A CLUGED IDLE JET?( CLOGED OR PLUGED=CLUGED) ARE THE CARBS PROPERLY SYNCED FOR BOTH FUNCTIONS? GOOD PLUGS?GOOD WIRES? COIL CONNECTED CORRECTLY? VACUME LEEK?DIST .....GOOD GAS?ENOUGH GAS?INTAKES TIGHT?BANNABANNA IN THE TAIL PIPE? Shocked VOLTAGE?

Yes it could be a million things. BUT I have done some simple diagnostics and it seems my timing is wonky (as in scatter.)

When I put the timing light on it at 2500 rpms i dont see a steady timing mark in the same place every fire. The marks move around as much 20+degrees every time the light flashes. So much so it would basically impossible to set inital or full advance on this thing with any sort of accuracy.

I did use a good amount of the supplied red cam lube from Web Cam. I used a good break in oil and overfilled it almost an extra quart. I did not let it idle at all and ran it for 30 minutes at 2000-3000 rpms, even though it was popping and backfiring bit the whole time. I would hope the cam ain't screwed already. RUNNING Web Cam 252 on EP12 with CB Ultra Light lifters. Didn't mess with the lobes but inspected the cam carefully and Web Cam does debur them properly in house. I did polish the lifter faces tho.

Gas is brand new. I plan to change oil soon but I havent got that far yet lol. Valves been triple checked. Rebuild carbs with the parts and guidance from McDragracer(Rick) the Dellorto guru. He advised me on jetting to start with and I bought all new jets and carb kits from him. New bearings, etc. Sodablasted and ultrsoninic cleaned all parts and careully inspected to make sure no blocked passages. Set float height per specs. Set the idle speed screw for both carbs so that throttle plates expose 1/2 of the first progression hole. Then roughly hooked up linkage based upon that for initial startup ( I have the snail sync tool but I was trying to break In cam so I havent been able to let it idle yet to fully sync carbs.) I've heard using the snail at higher rpms can break the tool? Bypass screws are in all the way currently Idle mixtures are out 4 turns.

Does not seem to have a vaccum leak, as Im almost postive I would recognize that immediately. This seems different. The throttle responds very quickly and revs up and down nice and crisp. Overall it seems like it wants to run well but the timing is shit... atleast that's my hunch. However my lack of experience leaves me a little in the dark here.


How stable is the voltage on your 12 volt feed to the engine - the automatic dwell adjustment of those Pertronix Ignitor units can be modulated by spikes and electrical noise on the 12 volt rail. And that turns into timing scatter.

Bad battery connectiion ? Loose wire ? Alternator or dynamo with worn brushes, bad voltage regulator, worn out ignition switch ?

Try it with points.
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PostPosted: Mon May 10, 2021 12:58 pm    Post subject: Re: New build, running rough, backfiring, suspect ignition. HELP! Reply with quote

When the distibutor is locked in position I can rotate to rotor by hand by about 40 degrees give or take. There is resistance, it feels like light spring pressure, but it can be rotated. I assumed this was normal, as if I was just feeling the advance mechanism. Other than that it doesnt have much slop if I just touch it lightly.
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PostPosted: Mon May 10, 2021 1:00 pm    Post subject: Re: New build, running rough, backfiring, suspect ignition. HELP! Reply with quote

mikedjames wrote:
How stable is the voltage on your 12 volt feed to the engine - the automatic dwell adjustment of those Pertronix Ignitor units can be modulated by spikes and electrical noise on the 12 volt rail. And that turns into timing scatter.

Bad battery connectiion ? Loose wire ? Alternator or dynamo with worn brushes, bad voltage regulator, worn out ignition switch ?

Try it with points.

Thanks, I'm running it on a test stand with just the battery powering it attached to the starter and I have a large cable grounding the battery to my test stand.

So basically the generator is not hooked up for the test stand... only running on battery. It was fully charged overnight before tho

Could that be a major issue?
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PostPosted: Mon May 10, 2021 3:23 pm    Post subject: Re: New build, running rough, backfiring, suspect ignition. HELP! Reply with quote

EDIT*** It did not actually fix the problem but my timing light is not showing scatter anymore... shit...

Ok I dont want to jinx anything but I installed my old distributor and it seems to have basically solved the problem. It's still needs some fine tuning I imagine, but overall no more constant popping and random backfiring. Also, now it appears to have literally zero timing scatter using my timing light at the pulley.a
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PostPosted: Mon May 10, 2021 3:38 pm    Post subject: Re: New build, running rough, backfiring, suspect ignition. HELP! Reply with quote

WELL, I guess I just got lucky for a second...

It's still doing the exact same thing as before pretty much. Popping through carbs and backfiring here and there. Now it also seems to not really rev up that nicely. It almost feels like it wants to die or something and kind of vibratez or something when I rev it up to what feels like maybe 3-4K rpms.

Really need help trying to diagnose this issue.
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PostPosted: Mon May 10, 2021 4:36 pm    Post subject: Re: New engine build backfiring out both carbs and exhaust. HELP! Reply with quote

I know that you are addressing an ignition issue.
But can I ask if you have setup your carbs correctly?
IIRC, You have 45 DRLA's. It really doesn't matter for the following questions.

Did you set the float level?

Did you set the throttle plates at .003" open?

Is the linkage in sync?

Do the carbs throttles open at the exact same time? You can check this by holding the throttle shaft lever on one carb and gently trying to move the hex/cross bar/linkage.
If one of the carbs tries to open, while holding the other closed. Your linkage is not in sync. This will cause a funky running condition. Much like you are describing above. Funky timing excluded.
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PostPosted: Mon May 10, 2021 6:06 pm    Post subject: Re: New engine build backfiring out both carbs and exhaust. HELP! Reply with quote

67rustavenger wrote:
I know that you are addressing an ignition issue.
But can I ask if you have setup your carbs correctly?
IIRC, You have 45 DRLA's. It really doesn't matter for the following questions.

Did you set the float level?

Did you set the throttle plates at .003" open?

Is the linkage in sync?

Do the carbs throttles open at the exact same time? You can check this by holding the throttle shaft lever on one carb and gently trying to move the hex/cross bar/linkage.
If one of the carbs tries to open, while holding the other closed. Your linkage is not in sync. This will cause a funky running condition. Much like you are describing above. Funky timing excluded.

Thanks! Yes I did set the float. I set the throttle plates so that half of the first progression hole was exposed.

I just did what you say with the linkage and held one carb closed while gently engaging the throttle and I get no movement off the throttle stop on the other carb.

Honestly at this point I dont know if its ignition related.

It also doesnt sound right when it revs up I've been noticing now. Like it kinda sputters out or something and starts vibrating kind of. Doesnt not sound good at all, I hope this will be simple to fix...
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PostPosted: Mon May 10, 2021 10:56 pm    Post subject: Re: New engine build backfiring out both carbs and exhaust. HELP! Reply with quote

Ok so small update. This all may be carb and tuning related. After messing with idle speed screws I have gotten it to idle pretty well at 800 rpms however something still isn't quite right becuase its backfiring from the carb and exhaust when I rev it up. Also REMEMBER, I'm running this on a test stand so it has no load on it. (Possibly making the eaxhuasr backfire more pronounced ?) Honeslty I can live with the exhaust backfiring occasionally if I'm confident in the tune and everything else, it's the puffs of smoke out the carb that bothers me )

It doesnt backfire at all when idling also. It's only when in the 1500-4000 rpm range where it backfires. It's the worst around 2000-3000 rpm... backfires in the exhaust a lot and also backfires in the carbs. Mianly the number 1 carb throat only, but it also does it occasionally on the number 4 as well I think. Small little puffs of smoke come out and make a burp/cough sound. The exhaust pops but it isnt a very violent bang if that makes sense. Also I cant see any actual flames I'm the tailpipes or anything but I do have long headers.
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PostPosted: Mon May 10, 2021 11:14 pm    Post subject: Re: New engine build backfiring out both carbs and exhaust. HELP! Reply with quote

give it some gas. Bigger main jet for starters.
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PostPosted: Mon May 10, 2021 11:33 pm    Post subject: Re: New engine build backfiring out both carbs and exhaust. HELP! Reply with quote

FreeBug wrote:
give it some gas. Bigger main jet for starters.


Agree! Sounds like it is really lean. Like dying for fuel! A quick test would be 2 cans of starting fluid! If it evens it out, you know you gotta go richer!
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PostPosted: Tue May 11, 2021 6:44 am    Post subject: Re: New engine build backfiring out both carbs and exhaust. HELP! Reply with quote

evanfrucht wrote:
Ok so small update. This all may be carb and tuning related. After messing with idle speed screws I have gotten it to idle pretty well at 800 rpms however something still isn't quite right becuase its backfiring from the carb and exhaust when I rev it up. Also REMEMBER, I'm running this on a test stand so it has no load on it. (Possibly making the eaxhuasr backfire more pronounced ?) Honeslty I can live with the exhaust backfiring occasionally if I'm confident in the tune and everything else, it's the puffs of smoke out the carb that bothers me )

It doesnt backfire at all when idling also. It's only when in the 1500-4000 rpm range where it backfires. It's the worst around 2000-3000 rpm... backfires in the exhaust a lot and also backfires in the carbs. Mianly the number 1 carb throat only, but it also does it occasionally on the number 4 as well I think. Small little puffs of smoke come out and make a burp/cough sound. The exhaust pops but it isnt a very violent bang if that makes sense. Also I cant see any actual flames I'm the tailpipes or anything but I do have long headers.


I think virtually everyone is right here.... Wink

It sounds like you have SEVERAL problems overlaid onto each other. You are askimg is it a timing problem or a fuel problem.....and the answer is probably....yes.

Yes....carb tuning issues (and virtually anyone knows more about carbs than I do).......but if you got it to change from backfiring from both carbs to one by tuning......but.....the timing shifts are still happening......I would say you have ignition issues.

A couple of things to check.
You are on a test stand with no alternator running yet? Most of the Pertfonix 2 and 3 from what I havd read.....do not work well with low or widely variable voltage. I think this was already mentioned.

The wires you are using. The Brillman link notes they are "suppression wires"....but only talks about the insulation materials in that link. It does not mention what the core of the wire is made of.

I found other notes from Brillman that suggests they are copper core. You cannot use solid/copper/metal core wires with Pertronix 2 and 3. A good discussion of it here up through Pertronix 2. Scroll down in this thread to a letter back from Pertronix.

https://www.jalopyjournal.com/forum/threads/pertronix-and-copper-core-wires.391152/

Ray
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PostPosted: Tue May 11, 2021 9:57 am    Post subject: Re: New engine build backfiring out both carbs and exhaust. HELP! Reply with quote

Thanks for all the advice so far. I've been talking to Rick (mcdragracer) the carb guy. I sent him a short video and we talked on the phone for a while trying to figure it out. He thinks its sounds pretty good but needs tuning. I'm going to keep working on the carb tune and see what that does.

Today I will pull the plugs to check them, I'm going to drain oil and then also check the valve adjustment again.

I think I was having some issues with the pertronix unit. Possibly this was due to me running it on the stand WITHOUT the generator hooked up. It hard to say... putting my old points distributor on didn't seem to completely or immediately fix my problems, but rather just seems to have improved things.

Could my mismatched stock distributor I have on there now have such an incorrect advance for my engine and that could be causing my popping and such in the mid rpm range when I rev it. The fact that the engine idles nicely, then pops under acceleration, it makes me wonder this?

Also I'm not sure about those Brillman plug wires but I know these are specified for electronic ignition and they also sell a regular copper core version that is a different part number. I'm pretty sure a lot of places sell those exact same modern wires that are meant to look old. Brillman might actually be the company that has them made or makes them... not sure. They are spiral core wires. I cut and assembled the wires myself and they did not have a copper core as far as I could see, the core was a dull grey color. Not sure what all that means really tho... lol
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PostPosted: Wed May 12, 2021 2:58 am    Post subject: Re: New engine build backfiring out both carbs and exhaust. HELP! Reply with quote

I don't like testing new external components on a new engine, nor do I like running a fresh engine with no load.
Now you know why. Or, at least the first part, and the second part is hindering your ability to have more clues.


To break in a FRESH engine, IMo it is safest to jet it a step richer idle jets and run a few degrees extra advance VS what you would normally expect.

After the engine is broken in and rings fully seated you can find out if your organically grown plug wires interfere with the astron3000 ignition module.

Problem could be unrelated, but it's just not worth the stress. I'll pull the distributor off my own car if I have to.
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