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Rebuild/replace Advice? '64 Mack C


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I bought a retired Mack C series with the EN707 Thermodyne gasoline powered engine (5 speed manual tranny). It had not been run in a couple of years other than very short distances. When I was ready to put it in the shop and have Mack give it an inspection and full tune-up, however, it was running very rough, wouldn't power up hills, and backfired and smoked alot.

Mack cleaned it up, cleaned the carb, replaced all the plugs, points, distributor, etc and sent me on my way several thousand dollars poorer. Til I hit the first incline and it lost power, backfired, and smoked.

Now they talk about a carb rebuild but they dont do it and suggested I talk to the local deisel shop - they are interested in doing it and can get the kit, but are suggesting it is a timing issue and that that should be addressed first after speaking to a New York collector who has worked on these. Question - I am assuming this is going to be a major repair as the engine is tucked forward against the cab - hours = $$$ and I am waiting for an estimate. I have no idea how far to go with these repairs. Is a rebuild a better idea? (I've read not). Is a replacement engine a possibility or would that cost be way too high?

I'm stuck as I'm not a mechanic, and the boys at the fire hall while good intentioned, had no idea the engine developed such bad performance while in storage when I offered to buy it and make it roadworthy again.

Would especially appreciate if anyone has any references I might be able to follow for others who have done this or who have access to parts. Will be needing a replacement windshield, need to find a pair of electric booster reels (originals were stripped off and used to create two brush units - a 4x4 and one atop a mini-tanker), and would love to find a full set of original aluminum marker lights as these have been replaced one at a time by cheap looking plastic ones from the local truckstop.

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for I have promises to keep and miles to go before I sleep, miles to go before I sleep - Robt Frost

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Bruce,

Your C model looks like it is in good condition. The 707 is a very basic engine and very reliable, who ever tuned it must not have completed the tuneup correctly, as once they replaced the ignition parts they should have set the timing on both distributors then set the carb, and given it a test ride (up hills). The fuel system could be causing the problem, and you could have problems with dirty fuel in the tank (from sitting), this will clog the filter, fuel pump and carburator. The engine has easy access, so that is not a problem.

You should see if the mechanic that did the tuneup did a compression test. If not that is the first step- to perform a compression test on the engine to make sure the basic engine is in good condition. Let it warm up and also check the oil pressure which should be at 15-20 pounds at idle hot, and 50-60 pounds at road speed hot. Then pull the plugs and check the compression, and should be at least 100 pounds per cylinder and within 20% of each other. Once you have confirmed that these are not a problem, and you have a solid engine, you can then move forward with diagnosing the problem climbing hills.

After sitting for several years you should change the fuel filter(s), check the fuel pump (to insure it is putting out enough pressure and fuel while going up a hill), and check that the filter on the carb is clean. The carb can be rebuilt, locally and will cost about $250, however there are carb shops that specialize in older carbs that can bench test the carb and rebuild it for about $400-450.

You might want to try another test, if you drive on level road, and try for maximum acceleration, does it backfire then? If so the backfire and smoke could be caused by the timing but more likely is a problem with the accelerator pump not adding fuel and causing the engine to run lean for a short time and cause the backfire.

The booster reels, windshield and marker lights are available, if you post a listing in the parts wanted area on this website you may find them here, or if not check on the SPAAMFAA website as there are other C models that have parted out and these should be available.

Good Luck,

Firemack

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Firemack - thanks very much for your ideas! The Mack dealer has an older mechanic who supposedly "loves" the old rigs and he and I have talked over the months that they have had the truck at the shop (some trouble getting parts). Most everything you mention was done with decent results, except, I suspect,the road test! I am upset that obviously they did NOT check the timing after replacing all the components per my work order.

The carb was cleaned, filters changed and over the past 1 1/2 years I have idled it as much as possible - enough to require refueling on two different occasions. It idles well, runs flat ground great with quick acceleration to 40, but then loses power. On an upgrade, it loses power at 30 and starts to backfire shortly after being put under load climbing the hill - back to level, it's fine. The manager at Mack suggested a carb rebuild and spoke to one of his off duty mechanics about doing it on the side, but then he instead referred me to the shop next door, a diesel shop, to talk to their lead man.

There I was told he had looked it over (to determine the type of engine that it was) and called a restoration shop in New York where they discussed the power under load - the builder seemed to lean towards it being a timing issue and I was adamant that I don't want it going back to the Mack people (they charge $20 more per hour for one thing!) to finish what they should have already done.

The diesel shop manager feels it is better to complete the tune-up (timing check and possible repair) before going to the carb/ rebuild.

I have joined spaamfaa and was hoping this might be the summer I could make a few of the SE area musters to start talking one on one with other collectors for advice and tips.

Right now I'm stuck between a shop and a high place (the shop is in Chattanooga and my firehouse is around Lookout Mtn requiring climbing several modest grades) not knowing if I should tow it home and find an independent mechanic or give the pros one more chance. I'm crossing my fingers right now that the diesel shop will do the fix and not break my bank but I have to consider my options if I keep getting told "now there's one more thing that needs to be done ..." !

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for I have promises to keep and miles to go before I sleep, miles to go before I sleep - Robt Frost

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I don't Know a lot about these motors or the distributor's that it has, but years back my dad had an International R220 with a 501 gas motor and it was doing something like yours is doing The trouble has inside the dist.the advance was froze shut and it would not advance the timimg when the engine called for power. Just a shot in the dark BULLHUSK

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Bullhusk,

Good suggestion, the distrubutor advance should be checked also, as the timing and backfiring usually go together.

Bruce, they should have checked this when they replaced the points, but it is always worthwhile to have them check it again, as it should not take long to pull the caps and check to see the advance is working, as I had that same problem on one of my distributors last year. Also make sure they check the fuel pump pressure as it could be running out of fuel, (or the carb float could be out of adjustment) and fuel pumps sometimes can be marginal and run on the level but not keep up with the fuel required to take it up a hill.

I travel to Chattanoga about once a month, maybe I can stop and see the truck when I am in town.

Firemack

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Thanks, Bullhusk - I have mentioned these suggestions to the manager via email. They are a diesel shop but he seems intrigued to tackle this old gas guzzler!

Firemack - for the next 2 months, you can probably see it on the backlot at the Chatt Mack/Volvo (on E 23rd off the 4th street exit of I-24). Because of this service failure, he is bending over backwards to help me. If work has begun, it will be a block away at S.E.Diesel.

for I have promises to keep and miles to go before I sleep, miles to go before I sleep - Robt Frost

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Bruceb,Let us Know how you make out with this I also am curious to know what was wrong? Oh by the way i do remember how my dad fixed it all he did was pulled the cap and cover off checked to make sure the springs were ok then sprayed this stuff he called cow piss inside to free it up(I think it't called nutbuster) something i think you can do yourself, Firemack seems to know these motors maby he can walk you through it, because i don't know if the guts are the same BULLHUSK

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  • 5 months later...

Bruceb,Let us Know how you make out with this I also am curious to know what was wrong? BULLHUSK

I posted a request last month seeking someone who may know someone here in the SE (I'm in Chattanooga) who has knowlege and experience, and access to parts to help with the old Mack, but have had no replies - this is the letter I got from SE Diesel outlining the problems - they did full tests and found the engine in ok shape in regards to the carb, plugs, and timing, but found issue with compression in cylinder #6. They say they can do the repair using machined parts, but that any inexact fittings could lead to catostrophic failure of the engine and they would rather not do the repair unless the factory parts can be located. They have searched for months now, phone calls, emails, and linking to other shops but have had no luck. The Mack still sits, paint fading, on their lot. Many suggest an engine swap, but I cant afford or rationalize a $10,000 fix to a $4000 rig.

From SE Diesel : Hello Bruce,

The valves are not seating in the head.

Problem could be valve, valve insert, or

piston burnt in valve, or a number of other

possible problems that caused the valve not to seat.

By the valve not seating the engine cannot fire due to loss

of compression.

We have called our Suppliers and have not found the parts needed.

No valves, valve inserts or head gasket.

We put the valve cover back on engine and have pulled out of the shop.

There is the possibility of removing the head and after measuring the valves

and inserts if they are needed we can match them to get something that will work.

But that will still leave us with the possibility f not getting a head set.

If you have any availability for the head gasket set, head gasket,

valves, valve guides, valve inserts, valve keepers and other components

needed to remove head, rebuild and install head.

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for I have promises to keep and miles to go before I sleep, miles to go before I sleep - Robt Frost

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  • 1 month later...

Where the problem presents itself on inclines only, I am inclined to suspect anyhting that changes in this condition. One problem I've encountered on carb/hill issues is the carb float being set too low. This causes a lack of fuel and stalling. Maybe you hve the opposite problem where the float is sinking of set too high. This might cause excessive fuel which sould flood the engine causing poor performance and smoke.

I might be all wet, but I'd get into that carb (assuming all other simple checks of timing, compression etc pan out within spec).

Good luck

Greg

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Generally a bad valve or one that does not full seat will show up as a miss at idle or a roughness. Looking at the photo of your smoke, Grey color is generaly excessive fuel or an incomplete burn. Has anyone checked to see if the choke is full opening when warm? Is the choke pull off working? The Carb float could have one of 2 problems. A miss adjusted float (too high) or a bad float needle will cause that color smoke by dumping fuel. Another thing to check is the ignition coil out put. The do break down over time and it may not be suppling the needed output under load. The will cause a miss fire because needed voltage at the plug(s) is not trhere. Also the vacuum advance could be not working as suggested. Paul

"OPERTUNITY IS MISSED BY MOST PEOPLE BECAUSE IT IS DRESSED IN OVERALLS AND LOOKS LIKE WORK"  Thomas Edison

 “Life’s journey is not to arrive at the grave safely, in a well preserved body, but rather to skid in sideways, totally worn out, shouting ‘Holy shit, what a ride!’

P.T.CHESHIRE

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Generally a bad valve or one that does not full seat will show up as a miss at idle or a roughness. Looking at the photo of your smoke, Grey color is generaly excessive fuel or an incomplete burn. Has anyone checked to see if the choke is full opening when warm? Is the choke pull off working? The Carb float could have one of 2 problems. A miss adjusted float (too high) or a bad float needle will cause that color smoke by dumping fuel. Another thing to check is the ignition coil out put. The do break down over time and it may not be suppling the needed output under load. The will cause a miss fire because needed voltage at the plug(s) is not trhere. Also the vacuum advance could be not working as suggested. Paul

The 707 was such a low volume engine (apparatus only) and has been gone for 38 years at best. You're not going to have much luck finding viable parts for it. Are you adamantly opposed to swapping it out with a 673 diesel? One of the members on here has a friend with one available super cheap from a fire truck.

My 707C had the same problems you describe did and we found it to be bad gas clogging the filters. The demand on hills was too much for the flow available through the filters.

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Bruce I just wanted to say hello. I live right down the road from you in Chickamauga. I have seen your truck at south eastern diesel before and had commented on it to friends. That's Twice this week I have seen other members trucks and didn't know it. If you need any help I would be glad to lend a strong back and a weak mind to your endeavors. I wish my Dad was still alive he could get her up and running for you in no time. He rebuilt an old Model T (?) Ford pick up before he passed away. Had it purring like a kitten....not to mention his old beloved 8N Ford tractor.

P.S You might check out the fuel supply lines, the rubber....Neoprene hoses they maybe collapsing internally. If you could run a temporary one to the carb and then run it up a hard pull you may find your problem. I had this happen on my Vision and it got where it wouldn't pull itself over a speed bump.

THE GREATEST NAME IN TRUCKS

MACK TRUCKS

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thanks for these additional posts and suggestions - as I've said, I'm at the mercy of the shop as I am not a mechanic. The suggestions about the carb and fuel lines were taken in consideration initially by Mack of Chattanooga who then told me they didn't have anyone in the shop who could do a carb rebuild! I abandoned Mack as incompetent and brought it to SE Deisel - the have considered the options and did find the compression problem. We discussed it, I could spend several hundred dollars as they nickel and dime me at $90/hr to check fuel, lines, floats, pumps, etc and then find we still have the same symptoms being caused by the bad valve.

As to the smoke, the pic can be deceiving, it is blue, not gray (just the strong sunrise coming over the ridge).

My problem with the engine swap is two-fold, one, the newer engine would then be working with all old components possibly starting an eternal domino effect of parts going bad which I can't afford; second is the cost - I found an identical rig up in Michigan in excellent running shape with excellent paint for $8000. I can't see spending 10k on an engine swap when I could get a primo 64 Mack ready to roll. I hesitate to by another one though oonly because it is THIS Mack's history with our department that makes it special. If I were to buy a rig just to own a fire truck, I think I'd research and find something more appropriate to my tastes.

Mackdaddy1911a1 - nice to 'meet' you! If I can't get SE Deisel to take the plunge and attempt the repair, I suspect I may just chug the old girl back around the mountain to Wildwood and store it. You would be more than welcome then to come by and treat it as your project while I reimburse you for parts and time - I simply don't have the mechanical apptitude to play with it and the lads at the fire hall are all body shop guys, not mechanics, LOL!

IF, SE gave me a price on the valve job, I might give it a try and see if I can at least nurse the engine along for a few years. Once the cylinder is up and running, I could look to tackle all these other fuel related suggestions.

I've just returned to work as an over the road driver so hope that by this spring I'll reach an agreement with SE Deisel about going for the repair or bring her home. Definitely feeling mellow that I've missed another parade season. thanks everyone, bruceb.

for I have promises to keep and miles to go before I sleep, miles to go before I sleep - Robt Frost

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  • 1 year later...

Update - still in limbo with the Mack - shop never able to find a carb kit and I finally had to move the truck back to Georgia or proceed with their repair plan of removing the head and looking more closely at the bad cylinder (a cost that they could only estimate between 2 and 4 thousand dollars depending on the extent of the repairs and amount of labor to machine unavailable parts). Have a local mechanic who took an initial look at it and made adjustments to the choke which helped some, but still waiting for him to make time to tackle the rest of the fuel line issues (thinking the previously replaced fuel pump may not be large enough). Anyway, poor thing is now pink from being out doors and with the economy I have added nothing to my savings account to be able to fund any major repairs such as consideration of engine replacement. In the meantime, a friend who is a professional photographer got several local models to pose with the Mack and we have put together a fundraising calendar - it came out nice and we are selling it for $11 via paypal with $2 more for shipping til the end of November. If you are interested, go to paypal and click "Make Payment" and input our email address : hookerhosecompany@gmail.com and approve a credit payment of $13 and I will get one (or more!) in the mail to you. Images from the calendar can be seen at our FB page : https://www.facebook.com/HookerHoseCo bruceb.

for I have promises to keep and miles to go before I sleep, miles to go before I sleep - Robt Frost

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  • 2 years later...

  • It's been a while so I am again visiting a couple of websites to update info on the Mack which basically is unchanged. While I moved it to Wildwood to my property two years ago (a Trenton, GA tow company allowed me to park it at their yard for a year), and made of point of at least firing the old girl up and idling the engine for a half hour or so per week, it one day inexplicably failed to start and I never got it running again. Has new batteries but given my forest location, this could be an electrical wire or fuel line chewed thru by hungry rodents (who have feasted as well on my minivan and pickup truck!). Anyway, no change in my financial status or ability to knuckle down and tow it off to SE Deisel to perform the engine work or ability to find a local mechanic. I finally posted the rig as for sale on SPAAMFAA last fall and made a similar announcement on my facebook page (hookerhosecompany) as well as FB pages for SPAAMFAA, Mack and C Model fans. Have had no takers at $3500 so have now decided its time to try and part it out. I am not a garage guy so am limited in my access to tools for parts, and limited in my knowlege of how to dismantle parts from the engine or pump. Anyone interested in mechanical parts would need to travel to the Mack and treat it as a 'you pull it" agreement. I have interested parties for emblems which I have been unable to remove do to the weld method used and difficult access. Also have people interested in the bumper, hand rail on the front of the hose bed, window glass, steering wheel... The Hookerhosecompany FB page has a photo folder of Mack Parts to show the condition of items such as the pitted chrome hand rails and gear rack, the air horns, lights, diamondplate, pump panel, mirrors, windshield, seats, etc. I also have the accessory items such as hoses, adapters, nozzles, extinguishers, vintage SCBA, aluminum ladder, wooden 10' pick pole, hard sleeve suction hoses and the strainer. https://www.facebook.com/media/set/?set=a.678332655518449.1073741825.382116005140117&type=3

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for I have promises to keep and miles to go before I sleep, miles to go before I sleep - Robt Frost

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bruceb:

That outcome is certainly a shame; it's a beautiful truck but you have to do what you have to do. I operated a 1959 Mack "C" model ladder truck back in the day

so I have an affinity for all "C" models. Our ladder truck also ended up in the big Mack graveyard years ago. You gave it a shot, plus all the money and

aggravation, so good luck with parting it out.

bulldogboy

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