Popping/backfiring/shifting issue

When I installed my Eddy carb. I put in a pressure regulator at the same time. With a standard mechanical pump, I was near 7 PSI until adjusted. That pump may be putting out more PSI than you think. Regulator is a good idea.

No line lock on the truck yet. Just foot braking off the converter for the time being. Eventually I would like to have a trans brake put in but this is someday down the road. I beleive the multiple spark discharge is all the time. I could be wrong.

As far as the modulator goes I adjustd its few times and that got normal driving shifting correct. Never seemed to effect wide open.

I will be putting a regulator on that stock pump as soon as the engine get put back together. I have it in my cart ready to go.

Thank you for the diagrams on the governeror I'll be checking into that...sorry for the short reply guys I'll give more details shortly!

Page 1 of the instructions states "above 3,000 rpm there is simply not enough "time" to fire the spark plug more than once"

To me, popping and backfire mean spark scatter.
And if it's not the 6AL, then it's probably the dizzy.

But that's just my experience.
You could be seeing something I never have.

On the popping/backfire issue, I've experienced that on 2150 carbs before. In my case, it was always the same problem, a bad accelerator pump, an easy fix. I'm not saying the accelerator pump is bad, but perhaps it doesn't have enough pump volume when the pedal is lifted to let it shift. Then when the pedal is matted again, the engine is needing more pump volume at that engine speed than the accelerator pump is providing. However, once the shifting problem is resolved, that should not be a problem needing resolved as lifting the pedal to get it to shift won't be necessary. On the larger carb idea, I would use a CFM calculator and put in your RPM and go by that on your carb size. They are accurate. A matched combination will provide the best performance whether racing or just driving to get groceries.

Angelo, modulator settings do not effect WOT shifts, they are controlled by the governor pushing against line pressure on a different land on the 2-3 shift valve, 1-2 is still being controlled by the throttle boost valve according to the diagram. Basically, the valve body is a hydraulic computer, weighing engine load (modulator and throttle boost pressure) against road speed (governor pressure) to determine when to shift, the downshift valve applies line pressure to a different part of the shift valve train to either force a downshift or hold a gear longer.
 

Frank Wyatt wrote

On the popping/backfire issue, I've experienced that on 2150 carbs before. In my case, it was always the same problem, a bad accelerator pump, an easy fix. I'm not saying the accelerator pump is bad, but perhaps it doesn't have enough pump volume when the pedal is lifted to let it shift. Then when the pedal is matted again, the engine is needing more pump volume at that engine speed than the accelerator pump is providing. However, once the shifting problem is resolved, that should not be a problem needing resolved as lifting the pedal to get it to shift won't be necessary. On the larger carb idea, I would use a CFM calculator and put in your RPM and go by that on your carb size. They are accurate. A matched combination will provide the best performance whether racing or just driving to get groceries.

Thing is he is above the accel pump travel at the RPM he is running when this happens, foot to floor and only backs off a little to get it to shift into high.

If racing go for a Holley carb and shelf that Eldy. I believe that is the only good place for a Eldy carb and even more so when racing because of the fuel PSI issues.
I run Holley's on my cars I have dragged raced, 2300 v2 on a stock AMC 304 and v4's from HPDP 650 to 750's on a built AMC 360. I also run a full MSD set up on the 360 as it is my drag only car.

I think the governor is what the issue could be.
I run a full manual reverse shift pattern TH400 on the drag car after burning up a new trany with just 2 1/4 mile runs. Not enough vacuum from motor (big cam) to shift.
It also has a custom 3000 stall converter now.

Now the 304 car is a street car, TF999 (HD TF904 but less than a TF727), and I would also have to back off the throttle to get it to shift into high but with the rear gear the car had the times or speed did not change thru the lights in 2nd or 3rd gear at just under 90 MPH, 2.89 rear gear.
Car did have a shift kit and would shift normal til you got on the gas and would chirp the tires going into 2nd gear. This car only used a down shift rod no vacuum so I adjusted it to be the best it could be both on the street and at the track. I was building the track car and did not want to start making a lot of changes.

I would find a transmission shop that does race tranys and run it by them on the shifting to see what they have to say.
I am sure once the shifting is tanking care of the miss / back fire will not happen.
If it does then fix that issue.
As they say "Only fix 1 issue at a time" because if you try fixing all at the same time and now you have other issues what did you "fix" before that caused this new issue?

Good luck and keep us posted on the fixes.
Dave ----

Dont worry the Eddy is going to get shelved for a 670 Street Avenger I beleive. I have always been a Holley guy, the Eddy is just what came on it. I do run this thing mostly on the street and it has good manners, but I'm building it for "stop light" races for lack of a better term. I run 1/8th mile often. The goal with this truck is to be able to scare myself so that I don't drive like an idiot but also have fun with.

Yes I am far above accelerator pump travel when this happens, I'm all in it and then as mentioned back out just enough to get a shift  into 3rd and then I'm back in it all the way.

I'm starting to agree that the governor is the culprit here. I'm also agreeing in that I think the backfiring issue is also due to it...remember it does not always happen, just more frequently than not. Like I said it has good street manners shifting otherwise. I'm just worried about vacuum loss at wide open, I have never put a gauge on it to see what it pulls but I'm willing to bet it's probably around 12-14 psi at idle which is just enough for the brakes and trans.

As I mentioned I do beleive this thing needs around a 2500 stall converter. Whatever is in it (I'm assuming whatever a stock car stall speed is) is just not cutting it for what I do with it.

I guess I'm going to have to dig into my transmission a little bit or stop down and talk to my buddy who worked at one of the local trans shops and see what he has to say. He told me putting a converter in it would probably help but who knows.

If it helps, here's a quick pull of it NOT doing it because of shifting manually 2-3 with the ratchet shifter instead of being in drive.

At the top of the run I'm touching 5,000rpm. I would say at the shift it was about 3500. The mid range is super strong in this truck.

https://youtu.be/oedJi_ltlWg

I'm not sure how to embed videos.

Are you flashing the converter?
By that I meant foot on brake but motor at idle till the green (or 2nd to last yellow for my street car) comes on and floor it. This will "flash" the converter over stock stall a little.

Because of the high gear in my street car, being a auto and had a Lock Right locker with street tires I would run a little higher tire PSI to get a little tire spin and flash the converter to help get the RPM's up and out of the hole. The car also had leaf springs and the front of the spring pack was clamped to act like MOPAR SS springs used in the late 60's. Again did not want to do a lot as I was building a drag only car but had to control wheel hop.
Street car on trailer in drive after a race yep 15.70 in the 1/4 mile

Drag only car 13.xx in the 1/4 but runs the numbers all day long with low .00x RT numbers


As for hurting your self driving crazy I would get that way with a road race car I built. I would park it for a few weeks then pull it out for a week till to crazy and park it again! I was not racing it enough.
When drag racing I never had that issue, guess I got it all out on the track as I was going just about every weekend?
Dave ----

I'm foot braking holding the RPMs up against the converter then all in once the tree goes green.

I have been running 235/75 bald Firestone all seasons with about 30-35lbs in them and I was getting massive wheel spin and 0 traction...I still managed to pull a 9.6/89+ mph in an 1/8th mile with a second gear start and a MASSIVE bog off the line. I have finally put spring clamps on it but I will be putting traction bars on it this year due to some wheel hop issues I was having. I have yet to air down on the drag radials I am putting on and have not tried with the clamps yet to see what it will do. I am confident with the engine running better, a 1st gear launch and good traction I will be deep into the 8s, enough the track wants a driveshaft loop and a helmet.

I would run the ratchet shifter all the time to stay in the power band but due to I beleive a stretched cable I cannot get the trans to manually shift into first...so all my launches have been in 2nd unless I start in drive. That is how I figured out that I need to pedal it...

I had a long (maybe too long?) post typed and lost it.
Try clamping the springs first: flate stock cut to over lap the springs on each side so you can put a bolt thru them.
Flat on top of spring with bolts, flat on bottom with lock nuts and tighten to clamp the spring where the other leaves ends, you may only need 2 clamps on each front of the spring. Do not clamp the rear of the spring and if it has factory clamps loosen / remove them to let them work.

On traction bars I don't think you will find ones to fit.
The rubber bumper needs to hit where the bolt goes thru the main leaf or you can bend the springs.
Also hard to adjust for different track conditions as you need to change out the rubber bumpers so you need to have a bunch in 1/2" leanth.

Look into Cal Tracs https://www.calvertracing.com/caltracs.html
If they don't list them for your truck call them, easy to work with them and great service.
I run a set on the drag car with new stock leafs and HD gas shocks out back.
I was at 1 track that was vary slick to the point some racers were thinking of not running. I may a little adjustment to the bars and it made a big difference. 4 link guys were changing holes for the bars, a lot harder & longer than me with the cal Trac's.

Up front I run 90/10 shocks and 6 cly springs (v8 motor) no sway bar but some may want to run a sway bar to limit front end rise. 6cly spring compress more with the weight of a v8 and store more energy to push the front up for weight transfer.
If you don't have this book find a copy
https://www.amazon.com/Door-Slammers-Chassis-Dave-Morgan/dp/0963121707
I just saw the price! That has to be a miss print as it cant be that much.
Anyway it is a great book for setting up a car / truck.
Dave ----

Angelo Voltura wrote

I'm foot braking holding the RPMs up against the converter then all in once the tree goes green.

I have been running 235/75 bald Firestone all seasons with about 30-35lbs in them and I was getting massive wheel spin and 0 traction...I still managed to pull a 9.6/89+ mph in an 1/8th mile with a second gear start and a MASSIVE bog off the line. I have finally put spring clamps on it but I will be putting traction bars on it this year due to some wheel hop issues I was having. I have yet to air down on the drag radials I am putting on and have not tried with the clamps yet to see what it will do. I am confident with the engine running better, a 1st gear launch and good traction I will be deep into the 8s, enough the track wants a driveshaft loop and a helmet.

I would run the ratchet shifter all the time to stay in the power band but due to I beleive a stretched cable I cannot get the trans to manually shift into first...so all my launches have been in 2nd unless I start in drive. That is how I figured out that I need to pedal it...

Way too much PSI in the tires, I would say try 28 PSI and use a good drag racing tire gauge.
Thing is once you get a little traction you will most likely get wheel hop.
Check the post above on home made spring clamps till you get Cal Trac's (hint hint).
Then try flashing the converter. You may have to play with accel pump shot as you may get a bog off the line. Little by little you have to work on each issue till all fixed.

If you have good traction and cant overcome the bog you can try to up the tire PSI to get a little tire spin but this can hurt the short times.
It is all trying 1 thing at a time till you get the best from that change and move on to the next to do the same. Test & tune is great for this.

Hope you are running a drag book log? Taking air temps and other weather conditions fi the track list them on the time slip. Then note how the run went with times from the slip and how you felt the run went.
Any tire spin, bug off the line, shifted to early or late, backed out at the line so not to brake out, etc.
This will also help with tuning the truck or any changes you want to make and be able to look back to see what it did. Don't over look the air temp to change times.

I also found it helpful at tracks where you only got 1 run before racing. I could go back to the log book and look up different air temps even at different tracks or even a track I had not been to before to get a dial in time with just that 1 run.
I used log books from Summit Racing and started it with the street car.

For reaction times (RT) do you do the same thing every time before you get to the track?
Yep can have an effect on times. Eat a big heavy meal 1 time and then the next candy bars your times will be different. Same goes for thru out the race day, I know that can be hard but if you want to win races it is what you have to do.
I got other tid bits too LOL
Dave ----

I have yet to clamp the rear springs, I was going to clamp just the fronts of them. I do think it has factory ones on it, but are loose. I haven't looked at it in a while with it being winter time, so I will have to check.

As far as traction bars, Lakewood does make some for spring over axle trucks that are long enough that the snubber lines up properly, but I was thinking about getting ones that tie right to the frame rails with heim joints, similar to caltracs.

My truck currently has mismatched stock Autozone shocks so they need to be replaced as it is and I can bet the coils are original. I am not sure how the thing holds an alignment but it does! The rear shocks are just some Gas Magnum Monroes, nothing fancy. I do want 90/10s for the front. Good call on the 6 cylinder springs. I have no way to set up a front sway bar as far as I know it never had one so I don't know how exactly it would hook up. Im definitely going to give that a read.

Yes I agree, I was kind of just bombing around and not expecting anything. I ran another set of bald 275/60 Cooper Cobras on 25psi and I got all KINDS of wheel hop especially tearing you know what out of a corner. Wheel hop is definitely an issue and I am willing to bet the rear springs are stock from 1979. I have managed to pull a 1.8 60 ft however.

I am getting a bog off the line but I attributed that to a second gear launch. In drive in 1st gear it will obliterate the tires without a thought, so traction is more the issue than anything. Not only that, but there is no weight and having a roll pan back there probably doesn't help.

I have not started a log book yet as I wasn't doing it frequently enough yet. I figured I would as I get my setup dialed in a bit more. Most runs are on video so that does help me. My reaction times are usually on point. We run a half second delay and I almost always cut a what would be an even .00 light or up to .20 but on the half second delay they read out .500 or .600. I am very consistent in my reaction times.

Being winter do up a set of clamps for the front of the spring only.
The rear may have a set factory clamps that are loose but make sure they are with the fronts clamped.
This would take little money and time and can be a big help in controlling wheel hop as that is the first thing you have to stop.

I don't know if I would go for the frame mounted bars. It turns it into something like a 4 link but you cant adjust center of gravity for lift like a 4 link does.
Also how can you adjust preload or for track changes?
At least with the old school traction bars you can change the rubber to adjust it.
I just can't see spending money for something that may only work a little when you can get something that will work a lot for a little more money.

And start a log book even if just fooling around. First it helps on filling in a log book for when you do this more and you can see from run to run and week to week what is going on.
Dave ----

Being winter time it is put away until at least May, but with the top end being off the engine right now due to a flat cam lobe that will be priority first. But yes I will put clamps in the front of the springs, I already have purchased a set of stainless clamps last year but never got around to installing them.

I do follow what you are saying but I believe they are adjustable with the heim joints though I will probably opt for Lakewood style bars for now.

I may do that on my laptop now that way I can keep a record of everything I need to do in order to make her quicker. Thank you for the advice, I eat it up,

Dave, FWIW, Torqueflites use a throttle rod or cable, no vacuum modulators ever on Chrysler transmissions. The BW35 and BW6 used in AMC products some had vacuum modulators, most used a throttle push cable. Ford went to vacuum modulators around 1960 from a throttle rod, the rod was kept for strictly WOT downshift purposes (you should see what the 430 Lincolns used, the throttle relay bell crank was on a spring loaded bracket, that depressed at WOT and operated the downshift rod).

Angelo, if that flat cam lobe is an exhaust valve, it will cause all kinds of back firing and popping, ask anyone about the "rubber camshafts" in Chevy small blocks in the 70s and 80s. They would idle fine, sometimes rev nicely in Neutral, but under any load, pop, pop, pop through the intake.

It is on the number 2 cylinder intake lobe. Lack of lubrication from my own negligence took it out on me driving to work one morning, fortunately it was over a period of time so there was no large metal chunks floating around, and the oil filter took care of most of it. Good flush and everything up top and down below was nice on disassembly and very clean, so I can get away with running it for now while I put my 429 together.


I knew I should have replaced those valve seals instead of continually putting oil in it. Live and learn!


Edit: I'm not sure if I mentioned it but the cam is aftermarket and I don't know what is in it as far as a grind number. But it is sure far from stock.

85lebaront2 wrote

Dave, FWIW, Torqueflites use a throttle rod or cable, no vacuum modulators ever on Chrysler transmissions. The BW35 and BW6 used in AMC products some had vacuum modulators, most used a throttle push cable. Ford went to vacuum modulators around 1960 from a throttle rod, the rod was kept for strictly WOT downshift purposes (you should see what the 430 Lincolns used, the throttle relay bell crank was on a spring loaded bracket, that depressed at WOT and operated the downshift rod).

You are right as my street car with auto uses a TF999 with the AMC bell housing.
Now if you were talking of my drag car with AMC motor and using vacuum modulator you have to look at early Jeeps as they used a TH400 with the AMC bell housing. Some also used an adaptor and the BOP bell IIRC.
Now being it came from a Jeep it had a 4x4 out put shaft that had to be changed to a 4x2 out put shaft and that could be from any GM TH400 auto.
When dealing with AMC and making them live and go fast you have to know all the ins & outs
Dave ----