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Re: Back with rough spot around 2500 rpm [Re: pjc360] #2421286
12/20/17 02:01 AM
12/20/17 02:01 AM
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garnett kansas
rhad Offline
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my thinking on the toggle switch is that it may be causing resistance thereby lowering the voltage/amperage draw run a jumper from the battery directly to the box that the toggle switch controls


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Re: Back with rough spot around 2500 rpm [Re: pjc360] #2421393
12/20/17 12:23 PM
12/20/17 12:23 PM
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the turn on lead doesn't need to be high current, it should work all way down to 10v or so. all it does is tell the ignition box to turn on. the bigger voltage wire that he has running to the battery is what provides the ign the real power.

seems you have good ignition and timing.
you have good compression.
the only other thing needed is fuel right?

what is the baseline tune on the carb you have and how is the carb setup now???

Re: Back with rough spot around 2500 rpm [Re: krautrock] #2422159
12/22/17 01:26 AM
12/22/17 01:26 AM
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Originally Posted By krautrock
the turn on lead doesn't need to be high current, it should work all way down to 10v or so. all it does is tell the ignition box to turn on. the bigger voltage wire that he has running to the battery is what provides the ign the real power.

seems you have good ignition and timing.
you have good compression.
the only other thing needed is fuel right?

what is the baseline tune on the carb you have and how is the carb setup now???


Carburetor is a quickfuel super street series 680cfm vacuum secondary carb.
I’m running 65 main jets and 75 secondary jets.
.031 idle feed restrictors, .065 idle air bleeds, .033 high speed air bleeds.
A 9.5hg power valve with .049 pvcr’s.
Floats are set half way up the sight glasses.
Idle mixture screws are about 3/4 to 1 turn out.
This isn’t a fuel issue I know it’s ignition.
I keep thinking it’s the crane box but what’s throwing me off is how this missfiring clears up once I take away the vacuum advance.
So that leads me back to rotor phasing.
But I have checked rotor phasing and it’s good.
So this is very strange I just don’t know what’s causing this.

Re: Back with rough spot around 2500 rpm [Re: pjc360] #2422188
12/22/17 02:52 AM
12/22/17 02:52 AM
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RapidRobert Offline
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Quote:
This isn’t a fuel issue I know it’s ignition.
I keep thinking it’s the crane box but what’s throwing me off is how this missfiring clears up once I take away the vacuum advance.
the vac can does three things, adds timing/shifts RF/increases reluctor gap. Are you saying the problem completely dissappears when the can is capped? something might be loose inside the dist that is being moved when the can shifts. I would cap the can & bump the timing up to where it is when the can is operational & see if it straightens out (grab your dialback). You're sure the RF is close enough when the can is deployed? iirc you said the reluctor gap does not change when the can is pumped up (it changes-gets wider on a regular dist) not sure how this dist is getting around that but it is a good thing). if you duplicate the timing & that ain't it then it has to be something in the dist functioning. (& this is a steady 2500+ miss correct?) EDIT & the can has no vac leak?

Last edited by RapidRobert; 12/23/17 03:26 PM.

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Re: Back with rough spot around 2500 rpm [Re: RapidRobert] #2422726
12/23/17 06:02 PM
12/23/17 06:02 PM
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Originally Posted By RapidRobert
Quote:
This isn’t a fuel issue I know it’s ignition.
I keep thinking it’s the crane box but what’s throwing me off is how this missfiring clears up once I take away the vacuum advance.
the vac can does three things, adds timing/shifts RF/increases reluctor gap. Are you saying the problem completely dissappears when the can is capped? something might be loose inside the dist that is being moved when the can shifts. I would cap the can & bump the timing up to where it is when the can is operational & see if it straightens out (grab your dialback). You're sure the RF is close enough when the can is deployed? iirc you said the reluctor gap does not change when the can is pumped up (it changes-gets wider on a regular dist) not sure how this dist is getting around that but it is a good thing). if you duplicate the timing & that ain't it then it has to be something in the dist functioning. (& this is a steady 2500+ miss correct?) EDIT & the can has no vac leak?


Can does not have a vac leak, I have checked the air-gap with and without vacuum advance while holding the distributor in my hand and applying vacuum to the vacuum advance with a mighty vac.
But when it’s in the engine and spinning at 2500 rpm it’s possible it looks a little different then how it looks in my hand.
Someone had mentioned that maybe the oil pump drive bushing could be wiped out causing the inconsistency in timing at 2500.
And it is a steady miss at 2500 that’s affecting every cylinder.
I will cap the vacuum and bring the distributor timing up to 43-44 degrees where it is when vacuum advance is hooked up at 2500 rpm and I’ll bring the rpm up and check every cylinder with the light and report back.
Since it’s chiristmas weekend I’m not sure when I’ll get to it but I’m gonna try ether today or tomorrow or Monday.

Re: Back with rough spot around 2500 rpm [Re: pjc360] #2423245
12/24/17 08:14 PM
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Turn the photo upside down and that’s a picture of the rotors position directly under the number cap terminal.
That’s with 18 degrees of initial timing plus another 12 degrees added by the vacuum advance.
So that’s a total of 30 degrees of timing at idle with initial plus vacuum.
That’s idling with 20hg of vacuum.
When I have the throttle held at 2500 rpm in nuetral the vacuum is around the same as it is at idle, maybe slightly less around 18-19hg.
So at 2500 rpm in nuetral the rotor should be roughly in the same exact spot that it’s inn while idling with 20hg of vacuum.
To me the rotor looks like it’s within range as to not cause any misfires or spark scatter inside the cap.

90E58874-DA84-49BD-A26D-5E6DDCA55A34.jpeg
Re: Back with rough spot around 2500 rpm [Re: pjc360] #2423266
12/24/17 08:32 PM
12/24/17 08:32 PM
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I still have the modified reluctor That will move the rotor forward 5, 10, or 15 degrees.
Looking at the picture of the rotors position with vacuum advance while zoomed in on it close I
Guess the rotor could come forward a little more, I’d guess maybe 5-10 degrees.
I just don’t know if that’s going to solve the issue or not.
But I can give it a try easily enough.
Last time I tired moving the position of the rotor I made my own slot on an old reluctor which moved the rotor a little too far forward, probly around 20-25 degrees and that made the missing worse at 2500.
That was before I got the modified reluctor from ehernberg.
I’m not an expert on rotor phasing and I’m not sure if rotor phasing can cause a missfire on all 8 cylinders or not.
Maybe at 2500 rpm the rotor is being pulled back a little bit further then what the picture shows when it’s idling and that’s whats causing the missfiring.
The most interesting part of this issue to me is how taking the vacuum advance away seems to clean it up.
So again that leads me back to rotor phasing.

Re: Back with rough spot around 2500 rpm [Re: pjc360] #2423456
12/25/17 07:00 AM
12/25/17 07:00 AM
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Cotati, CA
Dave Hall Offline
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You've got the hole cut. Shine the timing light in there when it's running and having a problem.

Re: Back with rough spot around 2500 rpm [Re: pjc360] #2423486
12/25/17 12:08 PM
12/25/17 12:08 PM
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Quote:
I’m not sure if rotor phasing can cause a missfire on all 8 cylinders or not.
Maybe at 2500 rpm the rotor is being pulled back a little bit further then what the picture shows when it’s idling and that’s whats causing the missfiring.
The most interesting part of this issue to me is how taking the vacuum advance away seems to clean it up.
RP is the same on all cyls (the spatial distance gap) but if the "gap" is borderline it can be random missing as different cyls have different charateristics but to KISS, the ans is yes. some of these Q's are redundant but you say capping the hose completely elims the issue? What Dave said, shine your light in there while IDLING & see where RP is at in relation to the cap terminal "bulge with (A) the can capped & (B) with it plumbed into manifold & the can will shift it CCW (SB). I'm assuming you have a dialback, get it running at 2500 & note the (total) timing then plug the hose & twist the dist to get the timing degrees back up to where it was with the can operational. NAPA has a rotor (# MO-3000 iirc) that has a .060" longer blade that helps with phasing ($8.xx out the door iirc) cuz it is the total gap that is in question, the circumferential gap (that you see with the light) & the radial gap (longer rotor helps with that) & if the total gap makes the "required" voltage greater than the "available" voltage from your particular ign setup then it will misfire & the required voltage is greatest at WOT at which point the can is non op (but this is a steady cruise from 2500 on up correct?. Short version: circumferential & radial distance is too great/reluctor gap issue (but we covered that potential)/too much timing (way less likely) but do get a number/cracked cap/bad plug wire(s).


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Re: Back with rough spot around 2500 rpm [Re: RapidRobert] #2423519
12/25/17 12:51 PM
12/25/17 12:51 PM
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a tip on drilling the inspection hole. i use a step drill. cuts a nice hole and doesn,t leave a raggedy outside edge on the cap.
beer

Re: Back with rough spot around 2500 rpm [Re: RapidRobert] #2423668
12/25/17 05:34 PM
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Originally Posted By RapidRobert
Quote:
I’m not sure if rotor phasing can cause a missfire on all 8 cylinders or not.
Maybe at 2500 rpm the rotor is being pulled back a little bit further then what the picture shows when it’s idling and that’s whats causing the missfiring.
The most interesting part of this issue to me is how taking the vacuum advance away seems to clean it up.
RP is the same on all cyls (the spatial distance gap) but if the "gap" is borderline it can be random missing as different cyls have different charateristics but to KISS, the ans is yes. some of these Q's are redundant but you say capping the hose completely elims the issue? What Dave said, shine your light in there while IDLING & see where RP is at in relation to the cap terminal "bulge with (A) the can capped & (B) with it plumbed into manifold & the can will shift it CCW (SB). I'm assuming you have a dialback, get it running at 2500 & note the (total) timing then plug the hose & twist the dist to get the timing degrees back up to where it was with the can operational. NAPA has a rotor (# MO-3000 iirc) that has a .060" longer blade that helps with phasing ($8.xx out the door iirc) cuz it is the total gap that is in question, the circumferential gap (that you see with the light) & the radial gap (longer rotor helps with that) & if the total gap makes the "required" voltage greater than the "available" voltage from your particular ign setup then it will misfire & the required voltage is greatest at WOT at which point the can is non op (but this is a steady cruise from 2500 on up correct?. Short version: circumferential & radial distance is too great/reluctor gap issue (but we covered that potential)/too much timing (way less likely) but do get a number/cracked cap/bad plug wire(s).


Ive checked timing with and without vacuum advance at 2500 .
With vacuum where it starts missfiring is 42-43 degrees.
Without vacuum it’s 32-33 degrees.
The rotor I am running does have a longer blade.
All of the electronic vacuum advance firecore distributors come with a longer blade rotor.
The length of the blade on the firecore rotor is the same length as the napa M03000 rotor.
I have a napa M03000 rotor in my tool box and I have compared it to the rotornthat cane with my firecore distributor they are the same length on the rotor blade.
Awhile back I had done a gear swap on the 8 3/4 that I put in that truck, went from 3.55s to 4.56s and I never got around to re-gearing the front Dana 44 axle to match.
So now the truck is at a shop waiting to have the front Dana 44 axle geared to match the rear axle.
We have over a foot of snow on the ground this morning otherwise I would have ran over and grabbed it today to do a couple more quick tests on the issue and then brought it back.
But without 4wd I’m not sure I could even drive it back to the house from the shop.

Re: Back with rough spot around 2500 rpm [Re: pjc360] #2423673
12/25/17 05:45 PM
12/25/17 05:45 PM
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Quote:
Ive checked timing with and without vacuum advance at 2500 .
With vacuum where it starts missfiring is 42-43 degrees.
Without vacuum it’s 32-33 degrees.
And with the timing giving 32-33 degrees at 2500 RPM with the hose capped, it is NOT missing? EDIT If NOT missing, can you plug the can in & twist the dist CW to get the total back down to 32/33.

Last edited by RapidRobert; 12/25/17 05:48 PM.

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Re: Back with rough spot around 2500 rpm [Re: RapidRobert] #2423689
12/25/17 06:37 PM
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Originally Posted By RapidRobert
Quote:
Ive checked timing with and without vacuum advance at 2500 .
With vacuum where it starts missfiring is 42-43 degrees.
Without vacuum it’s 32-33 degrees.
And with the timing giving 32-33 degrees at 2500 RPM with the hose capped, it is NOT missing? EDIT If NOT missing, can you plug the can in & twist the dist CW to get the total back down to 32/33.


Yes once I get the truck back from the shop I will perform all the tests you are suggesting.
I will verify where timing is for a second time with vacuum advance connected at 2500 where the missing occurs.
Then I’ll plug the vacuum advance and verify that the missfiring is gone when the vacuum is capped off.
Then I’ll bring distributor timing only up to the same amount of timing when vacuum advance is connected and it’s missfiring and bring rpms up and see if it misses without vacuum advance but at the same timing setting at 2500.
Then I’ll turn the distributor down and plug vacuum advance back inn to get the timing around 32-33 degrees where it is without vacuum advance at 2500.
I’ll report back what I find.
My truck is at the shop waiting to get the front axle grated to 4.56s to match the rear axle.
It is near by but with over a foot of snow on the ground I don’t want to try and drive it with no 4wd, not to mention I don’t have a shop or garage at the moment.
I am moving into a new house at the beginning of January that does have a small garage.
So I’ll be able to mess around with it and not be out in the elements.
I’ve got a lot going on in the next week, we’re moving on the 29th and 30th of the month.
I’m starting a new job on January 2nd.
Just had to get Christmas out of the way with the wife and 3 kids.
And the truck is in the shop waiting to be re-geared up front.
And I still have to figure out this strange missfiring bull crap.
So it’s been pretty stressful to say the least.
Plus I had to give notice to my current job which I do like a lot but this new job opportunity pays 3 dollars more an hour with better benefits and paid holidays and more paid vacation.
So it’s just been a hectic month and I really haven’t had much time to mess with the truck and specially now since it’s sitting at a shop without 4wd.

Re: Back with rough spot around 2500 rpm [Re: pjc360] #2423737
12/25/17 09:47 PM
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You got a lot on your plate, If we cant get this dizzy straightened out I will blueprint a regular one (if it will work with your setup/I will read back thru all the posts to ans that Q) & send it to you.


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Re: Back with rough spot around 2500 rpm [Re: RapidRobert] #2423790
12/26/17 12:16 AM
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Originally Posted By RapidRobert
You got a lot on your plate, If we cant get this dizzy straightened out I will blueprint a regular one (if it will work with your setup/I will read back thru all the posts to ans that Q) & send it to you.


I just need to get the truck back and get in the new garage and have some time to perform a couple more tests.
I’m going to start by bringing distributor timing only up to 42-43 degrees at 2500 and see if it’s still missing.
Then I’m going to retard the distributor timing down to around 22-23 degrees at 2500 and plug the vacuum advance back in to bring it up around 32-33 at 2500 and see what happens.
That should be able to pin point wether it’s soley a vacuum advance problem or if it’s a problem without vacuum advance.
Then I should have a better idea on what direction to go inn from there.
It’s just gonna take a week or two before I’m in the position to have the time to play around with it some more.
But I will report back on this thread after I perform the foloweing tests.

Re: Back with rough spot around 2500 rpm [Re: pjc360] #2426730
12/31/17 10:10 PM
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I’m not quite done moving, I got the truck back from the shop yesterday.
It is geared up front with 4.56s now so I have 4wd back.
Tonight I decided to turn the rev limiter all the way up to 9k rpm on both dials.
I pull the light out and check every cylinder with and without vacuum advance with engine refer to 2500 rpm.
Now the only cylinders that were showing a break in the light tonight are cylinder 6 and cylinder 8.
So I plugged the vacuum advance back in and checked cylinder 1 at 2500 and it’s not missing anymore like it was a couple of weeks ago.
The only change made was I turned up the rev limiter from 6k to 9k.
I don’t know why 6 and 8 are missing but I’m gonna bet money that the plugs in those two cylinders are gonna he fuel fouled or some what fuel fouled.
Or maybe just cylinder 8 will be and I was picking up the miss with the light from cylinder 8 while i was on cylinder 6 since the plug wires are so close together.
I’m going to pick up a couple new plugs tonight and play with it a little more in the morning.
I’m going to set the rev limiter at different settings and see what happens.
Since turning it up from 6 to 9 seemed to take away the missing from the other cylinders.
I’m still not 100 percent sure on what to think of this but I still have a gut feeling something is wrong with the crane ignition box.

Re: Back with rough spot around 2500 rpm [Re: pjc360] #2426993
01/01/18 11:55 AM
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I'm assuming the rev limiter is in the Crane box, otherwise it could be disconnected (we gotta add/run one this season). it is sure looking highly likely.


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Re: Back with rough spot around 2500 rpm [Re: RapidRobert] #2427220
01/01/18 04:40 PM
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Originally Posted By RapidRobert
I'm assuming the rev limiter is in the Crane box, otherwise it could be disconnected (we gotta add/run one this season). it is sure looking highly likely.


Yes the rev limiter is inside the box but I can dis-connect the 12v source to the rev limiter.
Which I may very well try today.
I’m going to try a few other things first and I’ll post the results.
I need to pull the plug in cylinder 8 since it seems to be the one missing the worst at the moment.
And put a new plug inn and start some more testing with and without vacuum advance.
And with the rev liimter set at different rpm’s and with it dis connected.

Re: Back with rough spot around 2500 rpm [Re: pjc360] #2427431
01/01/18 10:26 PM
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pjc360 i thought of you the other day. i thought my msd streetfire died on me. it was just a funny mistake though.
i haven't driven my truck in a month or so, i needed to move it, so i moved my coronet first, the battery ran down so i had to get jumper cables out. i was in a bit of a rush too.

got it moved then went to start my truck, turned the key in the ignition and i could tell it wasn't firing. checked some stuff and then gave up. later i checked resistance on the pickup coil in my dist, seemed fine. i was thinking i would just swap out the dist real quick. then i got back in my truck and turned the key, got one turn out of it and it fired off once and then nothing with the key.
then i remembered the ignition switch in my truck is bad and it wasn't supposed to be turning over with the key, there is a button to bypass it. ign. switch doesn't give the ign 12v in the start position, only in run.
LOL.
i just forgot how to start my own truck...

also, it's wayyyy cold here now and i still have the summer tune on the carb which is actually just a box stock quick fuel HR650 with the transition leaned out. it's just a bit lean in the summer but totally driveable after it gets about 5 mins of heat in the motor. with it in the low 30's to 20's right now it's misses real bad until it's fully warm. it's mostly in the transition circuit. because i have the jets at stock baseline tune.
i thought about bumping the IFR's up to .029 from .028 but i just gave the idle mix screws the smallest turn i could give them (setting is about half turn from closed) and it smoothed it out a bit, driving better now. will prob drill the .028 IFR's to .029 when it warms up.

Re: Back with rough spot around 2500 rpm [Re: pjc360] #2427460
01/01/18 11:15 PM
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So the only thing I was able to get accomplished today was I decided to pull cylinder 8’s plug and it was completely fuel fouled.
Looked like it had been sitting in a chimney to a fire place.
So I threw a new plug in cylinder 8 and left the rev limiter on the crane box turned all the way up to 9k rpm.
Took it for a drive and it’s no better, still missing real bad, and it’s even missing at a lower rpm now then where it normally started missing.
So I’m basically back at square one not knowing what it is causing this or what to do to figure it out.
Back to basically wanting to push this dam truck off a cliff and walking away from it.

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