711 ?

[Red Horse]

Well guys I bought a B-61S for the cab and it looks like the 711 in it is in much better shape then my old 673. No smoke and it sounds great. I have no experience with 711's. I came into the industry in the mid 60's when my company still had 673's and then transitioned to Maxidynes.

What should I be looking for and what should I expect? The engine is a 1965 and I'm putting it and the quadbox that came with it, in my B-68X . I will have a 10' dump on it and I intend to use it every now and then to grab a load of stone for my driveway and/or help out at the fairgrounds. The 673 that repowered this old gasser is like I said, a smoker and it is noisy- plus its a Duplex so I think 'm ahead with this swap.

[HK Trucking]

1965 was about the time that Mack began using the "fire ring" type head gaskets on the 711. This stopped a lot of the chronic head gasket failures that the 711 was prone to previously.

Look at the head studs. If it has all 5/8 head studs then it is equipped with the fire ring head gaskets.

If it has 3/4 head studs at the corners of the heads and the rest of the head studs are 5/8 then it has the old type head gaskets.

Other than that, not much difference in terms of durability compared to a 673, and the 711 has a little more horsepower & torque.

Yanking out that duplex and replacing it with a quad box is a very smart move.

[mack4ever]

my engine is a 711.there is nothing wrong abaut that engine.

[vanscottbuilders]

I have a 1966 R-600 with the original END711-NA and it runs great.

It does have the later fire ring type head gaskets.

Horsepower and torque are greater than the END673-NA.

Check in with OldMacksRus.com for more info on the

exact numbers.

I think you will like the swap, especially with more gear

possibilities.

Paul Van Scott

[Rob]

I think you will be pleased with the 711 engine given the parameters that you plan to use it under. I have a 1964 B-61S that was built as a natual aspirated engine but now has a "Mack" factory conversion turbocharging kit added to it. The paperwork I received from the Mack museum shows this truck was converted in 1967 in Chicago with new cylinder heads, injection pump, intake manifolds, and a couple other small parts that I can't discern. It sure runs strong, and smooth with a good "whine" when spooled up.

My understanding from a customer of mine that ran Macks almost exclusively in the 1960's was that 75,000 miles on a set of heads with that engine was a lot as they liked to burn valves attributed to heat. This conversion to turbocharging solved that problem by blasting cool air into the engine reducing the cylinder head temperature. This of course had the added bonus of producing more power as the fuel rate was increased, and timing retarded.

My grandpa bought and operated a lot of Mack trucks during the late 1950's to the mid 1970's. I vaguely remember him talking a few times of having cylinder head problems with relatively new tractors, but I was young then, and didn't pay the attention I should have.

All in all, I think you will have good service from this engine if maintained well. I sure would not be afraid of it.

Rob

[theakerstwo]

I think you will be pleased with the 711 engine given the parameters that you plan to use it under. I have a 1964 B-61S that was built as a natual aspirated engine but now has a "Mack" factory conversion turbocharging kit added to it. The paperwork I received from the Mack museum shows this truck was converted in 1967 in Chicago with new cylinder heads, injection pump, intake manifolds, and a couple other small parts that I can't discern. It sure runs strong, and smooth with a good "whine" when spooled up.

My understanding from a customer of mine that ran Macks almost exclusively in the 1960's was that 75,000 miles on a set of heads with that engine was a lot as they liked to burn valves attributed to heat. This conversion to turbocharging solved that problem by blasting cool air into the engine reducing the cylinder head temperature. This of course had the added bonus of producing more power as the fuel rate was increased, and timing retarded.

My grandpa bought and operated a lot of Mack trucks during the late 1950's to the mid 1970's. I vaguely remember him talking a few times of having cylinder head problems with relatively new tractors, but I was young then, and didn't pay the attention I should have.

All in all, I think you will have good service from this engine if maintained well. I sure would not be afraid of it.

Rob

I remember them turboing that engine but i never did one because i had left mack by that time but i remember them taking out the syncrovance and making the pump a straight drive so it would not advance the timing. I dont think at that time they were setting the fuel up and was mainly trying to get the engine to stay together.

[Rob]

I remember them turboing that engine but i never did one because i had left mack by that time but i remember them taking out the syncrovance and making the pump a straight drive so it would not advance the timing. I dont think at that time they were setting the fuel up and was mainly trying to get the engine to stay together.

I think you are correct Glenn. The work order ticket that I have states "timing retarded and fuel turned up to XXX percent; I think it is only about 5% though. I will have to dig into my files and post the paperwork.

Rob

[Red Horse]

Guys- thx for all of your input. We pulled the engine and its sitting in a box trailer that I won't get to untill Monday when I can check out the head bolts. I'll Keep you posted. The truck was built in September 1965 so hopefully it has the new style head gasket .

By the way, it was sold through Birmingham Ala. branch and original owner was Lawrence Lucas. One of the orders also indicates "Davis Trucking" as the customer and Prentiss Truck Sales, Lafayette Ind. as the dealer but that ticket was written in August and then the unit was assigned to Birmingham Mack in September. History is half the fun of these things. My B-68X was ordered in May 1960 by Albert Welch Inc. a good sized Boston Excavating contractor. They are still in business today and a buddy of mine isa field super for them. He mentioned this to one of the owners (grandson) whose comment was.."yeah- we probably still owe on it"!

Bob

[Red Horse]

Guys, Thanks for your input. The motor is sitting in a box trailer and I will check it out Monday and confirm the stud sizes.

Bob

PS You might have seen this B-61s in the classified section of WOT a couple of issues ago. It was the red one in FLA. I was told it was an early 60's but was actually built in Sept. of 65. Hopefully that is good news. Was delivered by Birmingham Mack to a Lawrence Lucas. The original order for the truck was through Prentiss Mack, Lafayette Ind. and the customer was Davis Trucking but somewhere along the line, the order was assigned to Birmingham Mack and their customer.

[Red Horse]

Guys, Thanks for your input. The motor is sitting in a box trailer and I will check it out Monday and confirm the stud sizes.

Bob

PS You might have seen this B-61s in the classified section of WOT a couple of issues ago. It was the red one in FLA. I was told it was an early 60's but was actually built in Sept. of 65. Hopefully that is good news. Was delivered by Birmingham Mack to a Lawrence Lucas. The original order for the truck was through Prentiss Mack, Lafayette Ind. and the customer was Davis Trucking but somewhere along the line, the order was assigned to Birmingham Mack and their customer.

Didn't think my first post went through??