170 with surging issue

[TNcowboy]

Hi guys
New to this forum and need a little help

I've got a '67 Bronco with a stock 170...1100 carb and load a matic distributor

The idle is slightly rough, but barely perceptible. It does buck and surge when either accelerating or cruising.Vacuum is 17.5 and has a very slight needle wobble...less than an inch of vacuum. Timing is set a 6 degrees.

I've rebuilt the carb. When I did I noticed that the power valve was stuck open. I was able to lube it and get it to move freely. I changed rotor cap wires and plugs. I've installed a Petronix ignitor. The distributor diaphragm is working as it should. The old coil primary circuit was out of spec so I changed it out to a petronix 1.5 ohm unit I changed out the fuel pump and fuel tank....wanted larger capacity and the truck had varnish old gas in it so I changed the pump as a precaution. I installed a fuel regulator because the pump is putting out almost 9 psi.

This weekend I changed out the spark plugs again, warmed it up and drove it around the farm...still surging. Back at the shop I pulled the plugs..see pic . Plug 1 still looked new..insulator still white, plug 2 had a little color to it, plugs 3 and 4 were carbon fouled, plug 5 had a brown tone, plug 6 did as well but slightly lighter.

I'm going to do a compression check but was wondering if you all had any insight into this

Thanks

 

[wsa111]

Welcome aboard.
If your oil pump shaft is 5/16" i would replace the loadamatic with one of my DS11's or HEI'''s & i also have a nice DUI. However you would have to run manifold vacuum to the vacuum advance or change to a later carb. that is not a loadamatic design.
See my listings in the small six for sale section. Bill wsa111

 

[chad]

looks 'all over the place' frm those plugs. Has compression test "shown w/in 10% of each other"?
If so start w/a good ign tune, run onto carb tune if warrented.

W E L C O M E !!!
to the best forum on the site!
Ck 'the Handbook' and:
https://fordsix.com/app.php/page/archives
if U stick around (hope U do) put up ur rig'n needed specs for diagnosis.
"The truck" is not enuff 4 me to do so... Oh wait, I C it now...just helps if in
a 'footer' to referr to on each post (not necessary to find 1st post every time)...
sorry - now, how did U find us?

 

[TNcowboy]

I've ordered a new compression tester....mine doesn't have an 18mm

But re the Ignition tune up and carb work, that's all been done. Having said that, IF, the compression test is in spec I'm thinking that the Ignition is suspect although why the plug reading is so varied I don't know since everything is new but the distributor...and why that pattern?

Also I had an extra ignitor so I replaced that....no change

I wondering if the valves in holes #3and4 are the problem.

I'll post compression readings when the new tester arrives

Thanks for the help

 

[B RON CO]

Hi, I would be concerned with a fuel pump putting out too much pressure. It looks like the middle 2 cylinders are very rich. That could explain the surging as well. I think maybe the carb is not as good as it should be. Maybe the throttle shaft is worn and wobbles, allowing a vacuum leak, or the float level is off or ???
I might be getting from your info that the Bronco has been sitting around for a while. The engine may run better the more it runs.
Take the compression test and see how that looks.
Good luck

 

[wsa111]

While your waiting for the compression gauge, advance the initial advance to in the 10-12 degree area. Road test to see if that helps.
Have you checked the float level?

 

[TNcowboy]

Hi, I would be concerned with a fuel pump putting out too much pressure. It looks like the middle 2 cylinders are very rich. That could explain the surging as well. I think maybe the carb is not as good as it should be. Maybe the throttle shaft is worn and wobbles, allowing a vacuum leak, or the float level is off or ???
I might be getting from your info that the Bronco has been sitting around for a while. The engine may run better the more it runs.
Take the compression test and see how that looks.
Good luck

I've got a regulator post fuel pump set to 4 psi so that is no longer an issue. Also just rebuilt the carb, float is set at 1 3/32" per specs. Throttle shaft feels good...no wobble. We took a 4 hour ride early in the fall and it ran like a sewing machine. I did put a new 23 gallon stainless tank in only to find that it had a sending unit leak so I pulled that, cleaned it since I found welding slag in it that had plugged the filter. Actually swapped tanks to a 23 gallon Krawlers Edge tank...much better tank...swapped filters. I'd changed the fuel line from tank to pump earlier.

Seems odd that anything from the carb would only foul holes 3 and 4. I'm thinking that the compression check will show valve issues there

Here's a picture of her. I just need to get her to run as good as she looks

 

[TNcowboy]

I did try that and didn't help. Float level is spot on

Frustration level is advanced too!

 

[chad]

from me mate bubs:
"...Here are the Stock 1962 144 or 170 Tune up specs
Distribitor rotates CW firing order is 153624
Autolite BF-82 plugs gaped at .034.
Basic Points setting gapping them at .025 but for the very best performance your looking for a Dwell setting of 37 Degrees.
Base timing is set to 4 Degrees BTDC for a Standard ( Stick) trans and 12 Degrees BTDC for a Automatic trans.
Idle RPM is 550 to 600 RPM for a Standard Trans and 500 to 525 RPM with an Auto Trans in Drive, parking brake set,
Fuel pressure is 4.5 PSI

To get most accurate tune up with a orginal point ignition always use of a tach / dwell meter, and also a timing light. This is the procedure I have used for decades to quickly do a precision tune up.

A good tune up follows this order of work.
1. Set the plug gap to .034
2. Set the points basic setting to .025 after its running set the Dwell Angel to factory spec of 37 degrees.
3. Now you need to set the timing to the 6 degrees (with stick Trans) or 12 degrees (Auto Trans) base timing vacuum line disconnected and plugged. You can also try more base timing to as much as 16 degrees but if there is any hint of pinging when you try it driving it up a slight grade then back it off until it stops. Reinstall the vaccum line to the Distribitor after setting the base timing.
4. With engine warmed up good, the intake and exhaust valve lash is set to .016 hot.
5. With warmed up good and the choke blade is fully open too. Set the Idle mixture to its Lean Best Idle. ie set to highest idle RPM then turn the mixture screw in 1/4 turn to lean it. See Addistional Notes below.
6. Set the curb idle speed to 550 to 600 RPM if standard Trans. Set idle RPM's to 500 to 525 RPM with an Auto trans in drive parking brake set, wheels chocked with block of wood, or you can have someone set in it and hold the brakes.
7. Repeat 5. & 6. To see if it improves anymore. When properly tuned these engines (when warmed up) will restart without even touching the gas pedal.

Addistional Notes
You might also test your coils output with the volt / ohm meter to see that it's within spec. Or you can do it by watching the spark color (a Bright Blue) and the lenght it can jump to cap terminal (from 1/2 inch or more).

While doing the tune up settings to the carb mixture and curb idle setting the engine needs everything installed and hooked up just as it will be operated! This includes having the Air Cleaner with a clean air filter installed and the PCV hooked up if your engine has one. If you want to use a Vacuum gauge then hook that up to the Intake Log below the Carb you would be looking for about a steady 17 inches of vacuum at idle RPM. Good luck in your tuning. A good upgrade for these engines is a Pertronix Ignitor engine still looks stock but gives you a hotter spark..."

I like a DSII system or hybrid DSII/gm 4 pin...& that additional few degrees advance above stock ford specs (a pollution control measure back then). Let us know~

 

[Dr_Dan_WWW]

That sure is a fine looking Bronco. Is that the original color? Did you restore it?

It's strange that it ran well in warmer weather, and then you made a few changes and now it surges. These guys on here are really smart on the inline 6, and I take their advice all day long. Of course, experience shows that often times these issues are the one's that we "just know it can't be that one, because I checked it over and over" - and then comes that big "Oh duh!" moment. Point: question what you believe is absolutely certain it can't be.

Let us know what the compression readings are.

 

[chad]

nature ofa log head is the 3 / 4 get "all the juice" (a la` the fouling) - end cyl get less.
If U have been lurkin around here much U may have seen the sadness around the typical cracked
heads (just ask Seth). Somehow he found 3 out of 4 cracked at the 3 / 4 port area. Wonder if
a lill spray of starting fluid at that area would tell if U have a crack? Cold weather? Less probs
after 7 - 10 min of running, etc can B some clues too.
How did you find us ?
How long have you been running this engine (or amount of mi U put on) ?
What's goin on w/tail pipe emissions? radiator level? oil inspection? U seem to have some mechanical experience.
Often familiarity w/the LOM SCV system can help U go far in diagnosis: https://fordsix.com/ci/Loadomatic.html

 

[B RON CO]

Hi, what is your fuel pressure with the new regulator in place? My gut still says fuel pressure or carb issue. Good luck

 

[TNcowboy]

Thanks for the replies

I found you all from Classicbroncos.com. It seems that almost everyone with a 6 wants to install a v8 and while I bought her with that idea...I just couldn't be the bonehead that took a survivor this clean and make irreversible changes. Actually, to show you the popularity of the little 6, one member there suggested that I might have a bad intake gasket. With the crack Idea he may be on to something there.

I bought a 75 for making a LUBR but this one is going to stay stock with very few exceptions

Fuel pressure is 4.5 psi but I can dial it down. I really am beginning to suspect the power valve in the 1100. I did free it up an it operated smooth BUT that is not a guarantee that it's still operating while running. The potential for cracks is not good news but I will check it out. It does not see to matter if the engine is up to temp; still a surge.

Even with all the downsides of the 1100/Load-a-Matic, I really want to keep her stock IF possible, especially in light of fact that original examples are becoming more rare and it's cool to see how they left the dealer unmolested. But, I believe that vehicles were made to drive, not be admired as garage queens so I may have to change carb and distributor but only if all else fails.

 

[TNcowboy]

That sure is a fine looking Bronco. Is that the original color? Did you restore it?



Let us know what the compression readings are.

It is the original color..Holly Green...not the original paint
I did not restore it but I am going to do a frame off restoration probably next year.

Waiting on the new Compression tester; soon as it comes in I'll run a check and let you know what I find

 

[TNcowboy]

nature ofa log head is the 3 / 4 get "all the juice" (a la` the fouling) - end cyl get less.
If U have been lurkin around here much U may have seen the sadness around the typical cracked
heads (just ask Seth). Somehow he found 3 out of 4 cracked at the 3 / 4 port area. Wonder if
a lill spray of starting fluid at that area would tell if U have a crack? Cold weather? Less probs
after 7 - 10 min of running, etc can B some clues too.
How did you find us ?
How long have you been running this engine (or amount of mi U put on) ?
What's goin on w/tail pipe emissions? radiator level? oil inspection? U seem to have some mechanical experience.
Often familiarity w/the LOM SCV system can help U go far in diagnosis: ci/Loadomatic.html

the plug readings are making more sense. Don't know about the tailpipe emissions but the coolant level is good..just had the radiator rodded and I flushed the system. The oil is fine.

I did study the LOM SCV system and it does offer unique challenges. Funny how so many long time Bronc owners don't know that much about it. Probably because it was only in the 66 and the 67.. that plus so many broncs had their 6's pulled for v8s

 

[chad]

I've been sendin folks frm CB over here (& many other sites) as the membership is quite unique (world wide experts, right sized egos). I used to get hounded offa CB for interest in the falcon/ThriftPower motors (& all i6, i8s) 10 yrs ago and more recently. It's great to C more there interested in these stout lill guys ( plez ck in w/our 'big six' forum too !!!). Not only that but "less bolt ons" too is beginning to lift my hopes...


Part of the curfuffel may B they are che**y guys?

AND the LOM/SCV did end in '67 but has a long backward history as well ('49 in Ford).

For me (was 70% off rd woods wrk truck 30 yrs) the i6 is v e r y worthy. Looking at a circle (the crank shaft) and noticing the bent8 (a "V" shape) and the 6 (how the rods come off/angle into connect) versus the 8's, the long and the heavy nature of the crank - I (possessing no automotive theory) intuited "a better off rd idea". My tq comes on at 1500 RPMs (see below signature). This means less slip of a tire in dirt. Here (actually 'the Handbook') I saw "the bigger the 1v the more tq" and found a low hood solution in the RBS ('74) carb. Startin to run on here...U have the post '64 motor so can upgrade to DSII (dizzy hole) and post LOM/SCV carb (would not need the 'feedback' system). Something to think about if still throwin trouble codes ina wk or 2...

 

[TNcowboy]

I've been sendin folks frm CB over here (& many other sites) as the membership is quite unique (world wide experts, right sized egos). I used to get hounded offa CB for interest in the falcon/ThriftPower motors (& all i6, i8s) 10 yrs ago and more recently. It's great to C more there interested in these stout lill guys ( plez ck in w/our 'big six' forum too !!!). Not only that but "less bolt ons" too is beginning to lift my hopes...


Part of the curfuffel may B they are che**y guys?

AND the LOM/SCV did end in '67 but has a long backward history as well ('49 in Ford).

For me (was 70% off rd woods wrk truck 30 yrs) the i6 is v e r y worthy. Looking at a circle (the crank shaft) and noticing the bent8 (a "V" shape) and the 6 (how the rods come off/angle into connect) versus the 8's, the long and the heavy nature of the crank - I (possessing no automotive theory) intuited "a better off rd idea". My tq comes on at 1500 RPMs (see below signature). This means less slip of a tire in dirt. Here (actually 'the Handbook') I saw "the bigger the 1v the more tq" and found a low hood solution in the RBS ('74) carb. Startin to run on here...U have the post '64 motor so can upgrade to DSII (dizzy hole) and post LOM/SCV carb (would not need the 'feedback' system). Something to think about if still throwin trouble codes ina wk or 2...

Well I'll tell you Chad, at Super Celebration east this year there were still a few 66 and 67's that were rock stock with 6's. Though I gotta say that the vast majority weren't. Still it's funny how the originals draw attention. Probably because they're rarer and they give a great glimpse of how they were when new and unmolested

One other thing...you don't see that as much with the 289/302 trucks...remaining stock..so these little 6's seem to be unique in that way as well

I may have to eliminate the LOM system but my first choice would be to keep it stock. We'll see...I want to drive it and reliability is important. If so I'll keep the original parts so it can be restored to stock

 

[bmbm40]

That is one nice looking Bronco! As you stated if you swap out the loadomatic just keep the parts and you can go back to stock anytime. I have all the parts that came of my 66. Engine, trans everything.
How many miles are on it?

 

[TNcowboy]

That is one nice looking Bronco! As you stated if you swap out the loadomatic just keep the parts and you can go back to stock anytime. I have all the parts that came of my 66. Engine, trans everything.
How many miles are on it?

Odometer shows A little over 68k. And I believe that is correct judging by everything else. Body is original including the fenders, doors, and tailgate since the 66-67 were different from later years

I'm hoping I don't have to change parts out basically so that when I lift the hood it can be a learning platform for bronco buffs that want to know the roots of the truck

 

[wsa111]

Thats one fine Bronco.
Hope you find the problem.
Do you access to a wideband A/F tester. That may help you find the culprit.