Turbo For 711

[fordguyhey]

Does anyone know of a good turbo and manifolds for a 711? I know it's probably not worth it, but I've got a B-61 10 wheel dump truck with an awesome running 711 in it. I know they're prone to blowing head gaskets, but I still want to try. The motor i've got is the later model with more head bolts so maybe it will last a little while...

[ThaddeusW]

Does anyone know of a good turbo and manifolds for a 711? I know it's probably not worth it, but I've got a B-61 10 wheel dump truck with an awesome running 711 in it. I know they're prone to blowing head gaskets, but I still want to try. The motor i've got is the later model with more head bolts so maybe it will last a little while...

The 711 was not meant to run a turbo. Something about lacking fire rings comes to mind (if they blow head gaskets without the turbo I would hate to see how easy it would be to blow one with the extra boost). Also the pistons lack the necessary oil coolers present on the 673 Turbo motors. I have heard of it being done but your are going to eventually ruin your perfect motor.

[terry]

I ran one for alot of years, never had a problem to speak of, just don't push it to hard. Terry

[Underdog]

Does anyone know of a good turbo and manifolds for a 711? I know it's probably not worth it, but I've got a B-61 10 wheel dump truck with an awesome running 711 in it. I know they're prone to blowing head gaskets, but I still want to try. The motor i've got is the later model with more head bolts so maybe it will last a little while...

I recently aquired a turbo set-up for a 673 thermodyne, including all manifolds and fuel pump. I am not sure if these parts will work on a 711. Perhaps others on the forum can elaborate.

I have been debating whether to put the turbo on my own 673P, as I have been told that none of the thermodynes had piston cooling jets. The jets first appeared on Maxidyne engines. If this is incorrect, I am sure I will hear about it as well

Gregg

[vanscottbuilders]

Gregg,

You are right - you will hear about it!

This is an old and ongoing topic here at BMT -

First - (I know this wasn't exactly your concern) The 711 engine was never produced by Mack in a turbocharged configuration. There was, however, at least one aftermarket conversion available. And, several of our members have reported successful operation - even with homemade set-ups. It's probably not recommended for anyone except the real experimental folks here. The later produced 711's with the revised head bolts did work very well in stock form. The head gasket problem was no longer a real issue. The engine has a reputation for good short trip operation - and perhaps not so great for over the road usage. The 711's I have driven have all been a great improvement over the 673's of the same period. The torque increase is very noticeable. I like a good 711 for restorations today.

Second - the normally aspirated 673P, although the latest and greatest of the Thermodyne line, did not have the oil cooled pistons for turbo operation. A home made turbocharging arrangement will likely end with disappointment.

The later turbocharged 673's did, however, have oil jets to cool the pistons and these were very successful for many operators. If memory serves me - these engines were the C series of 673 engines. Best to check that fact out.

Early turbo-charged 673's worked pretty well in stock form and when kept within the recommended operating parameters. Improper operation, and/or excessive hot-rodding led to early demise. Just like life!

The Maxidynes use substantially more boost pressure than previous Mack diesels, and do have piston oil cooling, engine block and head construction, ring configuration and bearing surfaces to handle the design loads. These engines are very close to bulletproof, and could withstand the most ham-handed of operators.

Nice F model in your avatar!

Paul Van Scott

[other dog]

The Maxidynes... are very close to bulletproof, and could withstand the most ham-handed of operators.

Nice F model in your avatar!

Paul Van Scott

That's exactly why they gave me one to drive!

[theakerstwo]

I recently aquired a turbo set-up for a 673 thermodyne, including all manifolds and fuel pump. I am not sure if these parts will work on a 711. Perhaps others on the forum can elaborate.

I have been debating whether to put the turbo on my own 673P, as I have been told that none of the thermodynes had piston cooling jets. The jets first appeared on Maxidyne engines. If this is incorrect, I am sure I will hear about it as well

Gregg

This is correct. T%he first piston coolers was on the maxidyne or ENDT 673 B and C. Not the eary ENDT 673.The eary engine had 9/16 head bolt studs and only 18. The good ENDT 673 with piston coolers had 5/8 head bolt studs and was 20 of them per head.

The 673 turbo and manifold with 18 head bolt engine will bolt up to the 711. In most cases you had to dump the turbo drain into a adapter that was between the air compressor and the pan.Some of the latter engines and it may be the 5/8 stud engine used a side plate on the right rear over the lifters that had a fitting in it to dump the oil from the turbo.If i was going to turbo a 711 i would take the fuel pump off and remove the sanrovace on the pump drive and get a straight drive coupler drive from a turbo engine and then retard the timing 2 degrees. Remove the govenero cover and remove the smoke screw from the fuel stop cam. Then set rack forward only two threads at the most. That was if i remenber .070 of rack. That all that engine needs with the hi compression pistons.It will need more air cleaner if its like most. But i dont know what air cleaner it has.

[Underdog]

Thanks everyone for all the info. These engines were before my time and I am still trying to learn as much as I can.

Paul you are right to say that is a nice F model, and thank you! It is a clean, good running 673P, so I hesitate to modify it in any way. Stay tuned, the turbo & fuel pump, etc. I have may soon show up for sale.

It was a lot of fun getting that picture, too. It was taken as I went a few laps on Mack Truck's test track at the old Engineering Center in Allentown 10/30/10. If you look close, my friend Bill is trying to keep up with his IH Emeryville!

Gregg

[Rob]

My 1964 711 has been turbocharged since April, 1966. It was a retrofit from Mack to keep the valves from burning in the heads by pushing more air into them. The byproduct of this was more power. My grandpa had purchased three B61's with 711 engines and not one ran 100,000 miles before needing the valves done because of burning. These trucks were also retrofitted with turbocharging and supposedly they were good trucks afterward. This is as I remember grandpa telling it many years ago.

I don't have a boost gauge in either this B61, or my B67, but I'd bet pressure build was slight.

Rob

[Underdog]

My 1964 711 has been turbocharged since April, 1966. It was a retrofit from Mack to keep the valves from burning in the heads by pushing more air into them. The byproduct of this was more power. My grandpa had purchased three B61's with 711 engines and not one ran 100,000 miles before needing the valves done because of burning. These trucks were also retrofitted with turbocharging and supposedly they were good trucks afterward. This is as I remember grandpa telling it many years ago.

I don't have a boost gauge in either this B61, or my B67, but I'd bet pressure build was slight.

Rob

Rob, do you know if any other modifications were done along with adding the turbo? If the desired result was to add more air, was the fuel pump changed as well or left alone?

I would say a pyrometer is more telling than a boost guage for these old engines.

Gregg

[220cummins]

My 1964 711 has been turbocharged since April, 1966. It was a retrofit from Mack to keep the valves from burning in the heads by pushing more air into them. The byproduct of this was more power. My grandpa had purchased three B61's with 711 engines and not one ran 100,000 miles before needing the valves done because of burning. These trucks were also retrofitted with turbocharging and supposedly they were good trucks afterward. This is as I remember grandpa telling it many years ago.

I don't have a boost gauge in either this B61, or my B67, but I'd bet pressure build was slight.

Rob

Thats what I always thought. Mack recommended adding this kit to help the valve problem and cooling overall. Not to mention the power increase.

Edited December 1, 2010 by 220cummins

[fordguyhey]

My 1964 711 has been turbocharged since April, 1966. It was a retrofit from Mack to keep the valves from burning in the heads by pushing more air into them. The byproduct of this was more power. My grandpa had purchased three B61's with 711 engines and not one ran 100,000 miles before needing the valves done because of burning. These trucks were also retrofitted with turbocharging and supposedly they were good trucks afterward. This is as I remember grandpa telling it many years ago.

I don't have a boost gauge in either this B61, or my B67, but I'd bet pressure build was slight.

Rob

Well that puts the nail in the coffin as far as I'm concerned. Now I absolutely have to do it. So, again, if anyone has the necessary parts for sale, please let me know.

-Ryan

[Rob]

Rob, do you know if any other modifications were done along with adding the turbo? If the desired result was to add more air, was the fuel pump changed as well or left alone?

I would say a pyrometer is more telling than a boost guage for these old engines.

Gregg

HI Gregg, I do not know if anything other than the syncrovance eliminated from the injection pump was done, or not. This truck is original as far as the engine block and heads and had little over 77,000 miles when it was turbocharged. Everything external looks to be 100% original.

Rob

[vanscottbuilders]

Gregg,

I have heard that Mack did recommend some low pressure turbocharger retro-fits for the early 711's. They didn't actually produce any 711's with turbos from the factory. The kits were to correct a problem with a specific run of 711 serial numbers, as I understand it. And Rob is correct in pointing out that these were really "turbo-normalized" applications with pretty low boost pressures, as they were intended for head & valve cooling purposes primarily.

Regardless, it still doesn't make the 673P a likely candidate for turbocharging. However, if you look around, you can find a 673C-ENDT factory turbocharged 205 hp engine that was, in fact, an original Mack option in your truck. That makes the most sense to me.

If originality isn't a real concern, a good 237 is a way better idea. In either case, the engines are available pretty reasonably, and are almost bolt-in retro-fits.

Paul Van Scott

[Rob]

My 711 engine that is turbocharged has much greater power than the B67 with an ENDT673 engine from what I've experienced. In fact, the 711 probably does not pull like a 237, but it's not a long way from it. I've never pulled anything of significance however the guy I received the truck from told me it didn't have any problems pulling a gross weight of 90,000 to the elevator. Until it broke a stratoflex fuel line and stopped running, it was used a lot during harvest.

This is the truck I call "Yella Dog".

Rob

[Underdog]

Gregg,

I have heard that Mack did recommend some low pressure turbocharger retro-fits for the early 711's. They didn't actually produce any 711's with turbos from the factory. The kits were to correct a problem with a specific run of 711 serial numbers, as I understand it. And Rob is correct in pointing out that these were really "turbo-normalized" applications with pretty low boost pressures, as they were intended for head & valve cooling purposes primarily.

Regardless, it still doesn't make the 673P a likely candidate for turbocharging. However, if you look around, you can find a 673C-ENDT factory turbocharged 205 hp engine that was, in fact, an original Mack option in your truck. That makes the most sense to me.

If originality isn't a real concern, a good 237 is a way better idea. In either case, the engines are available pretty reasonably, and are almost bolt-in retro-fits.

Paul Van Scott

My truck and engine are original and in good condition. That is a factor in my decision. I have my eye on another complete truck, a 1970 F with a 237 to do my work and keep my '63 for shows and such. The seller though is asking about double what I think it is worth, so we will see how that goes.

Gregg

[cfesting]

The later produced 711's with the revised head bolts did work very well in stock form.

How can one visually identify a 711 with the newer, revised head bolts? Is it the number of head bolts used?

Thanks!

[jddodger]

Yes, the older version had 18 head bolts, while the updated version had 20. Look at the outer corners of the head on the intake side. One larger size bolt would be the older style. Two bolts the same size as the rest would be the newer style.

[theakerstwo]

Yes, the older version had 18 head bolts, while the updated version had 20. Look at the outer corners of the head on the intake side. One larger size bolt would be the older style. Two bolts the same size as the rest would be the newer style.

The old 711 had a corner head bolt as in 3/4 and two per head.