Rebuilding Etaz 673

[convoyduel]

Looking like I will be into a rebuild of my ETAZ673. What is a good source for reasonably priced overhaul kits? Also, are there any tricks to the ETAZ673? This is my first.

[Lmackattack]

well if you want to go cheep ya can pull both heads,intake,exhaust,etc...all at once if you just plan to do the bottem end. that saves time and $$

Regarding internal parts... I have heard that the older mack brand stuff is now "made in china" and the PAI stuff is now about as good as the mack stuff. However in the last 8 or so years I have seen a few more failures with PAI pistons the last being 3 years ago and 2 failed PAI pistions in the same motor 100,000 miles... they may have improved but dont know.

is that engine just tired or...?

[Superdog]

Dan,

Try agkits.com

[Superdog]

Just curious,did that truck have the RT1110 and 3:65 rears originally?

[convoyduel]

Superdog,

The truck originally had the RT1110 and 3.89's on 34 Camelback. It now has a Fuller 13 and 3.55 Rockwell on Pete air ride. The holes are all still there for the camelback, so we're going to roll a set back under eventually. I found agkits but I didn't see the ETAZ673 on any of the parts lists. As the engine S/N shows its the original engine, I don't want to swap, I want to rebuild.

LMack,

Yes, the engine is very tired. When started it yesterday, it ran for a short while then started bucking, popping and shaking the truck, throwing a lot of white smoke out the pipes. I've never heard anything like it myself other than to say it almost acted like an old mechanical engine with the jake on at idle. When it was running, it seemed like there was a noisy valve or rod, but these old Mack engines are hard to tell which knock is normal and which is not.

[bullhusk]

Well if it's startin to do that you better change the cam & lifters on the rebuild!! BULLHUSK

[Lmackattack]

is this ETZ673 the same as a ENDT676 285hp?

they look the same from the out side? was the ETZ just a Ca emissions motor? Alwasy wondered what a ETZ was desegnated for. seamed kinda rare of a engine?

[rhasler]

is this ETZ673 the same as a ENDT676 285hp?

they look the same from the out side? was the ETZ just a Ca emissions motor? Alwasy wondered what a ETZ was desegnated for. seamed kinda rare of a engine?

Here are the model designations for pre 1980 engines, sorry about the quality of the scan. I'll load it to the wiki as well.

Engine Model Designations.pdf

[b61mack]

is this ETZ673 the same as a ENDT676 285hp?

they look the same from the out side? was the ETZ just a Ca emissions motor? Alwasy wondered what a ETZ was desegnated for. seamed kinda rare of a engine?

The ETAZ 673 is a 300+ (315)HP the liner kits are the same for 237,285,300,315 maybe the 350 2 valve dont know for sure. when you got a basic engine from MACK you bolted your pump, injectors,turbo on and had the same HP. Ron

[HK Trucking]

Yes, the engine is very tired. When started it yesterday, it ran for a short while then started bucking, popping and shaking the truck, throwing a lot of white smoke out the pipes. I've never heard anything like it myself other than to say it almost acted like an old mechanical engine with the jake on at idle. When it was running, it seemed like there was a noisy valve or rod, but these old Mack engines are hard to tell which knock is normal and which is not.

Looks like it's a Dynatard equipped motor?

If so, it sounds like one of the Dynatard solenoids is stuck on.

[Rob]

Looks like it's a Dynatard equipped motor?

If so, it sounds like one of the Dynatard solenoids is stuck on.

I agree and it's just a wire to pull to isolate the problem.

Wonder how it idles at about 1000rpm?

Rob

[Lmackattack]

hmmm... I thought all 2 valve 300+ and 2 valve 350s had the air to air and air to water charge cooler?

[Superdog]

That was a damn good engine.Most of the ones around here got ordered with the RT1110 and 3:65's,but most guys that had them ran 22.5's also.One guy had one in a '78 Cruiseliner,he turned 4th and 5th around in the tranny,it was a real screamer.

[b61mack]

Superdog,

The truck originally had the RT1110 and 3.89's on 34 Camelback. It now has a Fuller 13 and 3.55 Rockwell on Pete air ride. The holes are all still there for the camelback, so we're going to roll a set back under eventually. I found agkits but I didn't see the ETAZ673 on any of the parts lists. As the engine S/N shows its the original engine, I don't want to swap, I want to rebuild.

LMack,

Yes, the engine is very tired. When started it yesterday, it ran for a short while then started bucking, popping and shaking the truck, throwing a lot of white smoke out the pipes. I've never heard anything like it myself other than to say it almost acted like an old mechanical engine with the jake on at idle. When it was running, it seemed like there was a noisy valve or rod, but these old Mack engines are hard to tell which knock is normal and which is not.

You might have broken rings, i have heard a small knock in some and a piece of the ring works its way on top of the piston and you have a small knock it dosent take much. Ron

[RFC]

Just want to say hello been a member for a while but never have time to post anything. I have a endt-676 285hp in my 78 r model. Has a bad cam but I have a spare motor. Got a price from Mack for cam and lifters $3300.00. Cheaper to find another 2 valve in good shape in my opinion. Also I used Agkits for my rebuild on my International DTA-466, truck runs like a raped ape very happy with them.

Cheers, Robert

[convoyduel]

The dynatard is basically the same as a jacobs engine brake, isn't it? I didn't see any switch in the cab for a dynatard, but i'm not 100% sure what to look for. It acted very much like an engine bucking and fighting a jake brake. The tapping I heard all along sounded more like a valve adjustment on a cylinder, but I haven't pulled anything to even start to look.

[Rob]

The dynatard is basically the same as a jacobs engine brake, isn't it? I didn't see any switch in the cab for a dynatard, but i'm not 100% sure what to look for. It acted very much like an engine bucking and fighting a jake brake. The tapping I heard all along sounded more like a valve adjustment on a cylinder, but I haven't pulled anything to even start to look.

Hi Dan, a "Dynatard" does essentially the same thing as a "Jacob's Engine Brake" but operates different. "Dynatard" uses a modified camshaft profile and electric solenoids over the exhaust rockers to force the cam followers to ride this profile when engaged. There should be a switch on the dash to turn it on or off. Most of the "Dynatard" equipt engines have a single wire attached to the governor section of the injection pump. This wire attaches to a foil strip on the underside of the cover that contacts the fulcrum of the pump rack to force a ground to the system engaging the solenoids. If someone has been into the governor, or taken the cover off and bent the strip it could be making contact at idle which could cause the problems you mention. Herb helped me with one of mine that was doing exactly that.

I'll get you a copy of the adjustment procedure if you like. It is quite simple to adjust but for starters, remove the wire if present and see if the problem persists.

Rob

[convoyduel]

Went and looked for any kind of wire today...no dice. There's no switch in the cab, no wire off of the fuel pump. I started it up for giggles and it ran just fine. I'm very confused. One other note, this engine is governed at 1800. Is that normal for the ETAZ?

[rhasler]

Went and looked for any kind of wire today...no dice. There's no switch in the cab, no wire off of the fuel pump. I started it up for giggles and it ran just fine. I'm very confused. One other note, this engine is governed at 1800. Is that normal for the ETAZ?

My manual shows that 1800 rpm is the full load goverened speed for the ETAZ(B)673C engine. No load rated speed for said engine is 2185 rpm.

[HK Trucking]

Hi Dan, a "Dynatard" does essentially the same thing as a "Jacob's Engine Brake" but operates different. "Dynatard" uses a modified camshaft profile and electric solenoids over the exhaust rockers to force the cam followers to ride this profile when engaged. There should be a switch on the dash to turn it on or off. Most of the "Dynatard" equipt engines have a single wire attached to the governor section of the injection pump. This wire attaches to a foil strip on the underside of the cover that contacts the fulcrum of the pump rack to force a ground to the system engaging the solenoids. If someone has been into the governor, or taken the cover off and bent the strip it could be making contact at idle which could cause the problems you mention. Herb helped me with one of mine that was doing exactly that.

I'll get you a copy of the adjustment procedure if you like. It is quite simple to adjust but for starters, remove the wire if present and see if the problem persists.

Rob

Hi Rob.

Based on what Dan was describing I was also thinking that one of the Dynatard solenoids could actually be mechanically sticking in the applied position even when no actuation current is present, causing 3 cylinders to be braking while the other 3 are running normally.

Back then, if I remember correctly, Mack was using the Dynatard type cams in all their engines,whether equipped with a Dynatard or not, and a special valve adjustment procedure was necessary with these.

If the engine is not Dynatard equipped and this is happening, it's possible the valves have not been adjusted correctly, causing the exhaust valve lifters to ride on the Dynatard portion of the cam profile.

.

[Rob]

Hi Rob.

Based on what Dan was describing I was also thinking that one of the Dynatard solenoids could actually be mechanically sticking in the applied position even when no actuation current is present, causing 3 cylinders to be braking while the other 3 are running normally.

Back then, if I remember correctly, Mack was using the Dynatard type cams in all their engines,whether equipped with a Dynatard or not, and a special valve adjustment procedure was necessary with these.

If the engine is not Dynatard equipped and this is happening, it's possible the valves have not been adjusted correctly, causing the exhaust valve lifters to ride on the Dynatard portion of the cam profile.

.

Hi Herb,

I agree with you on this one. From Dan's description of not having any wiring to attribute to the "Dynatard" setup, I'll bet the exhaust valves are set too tight. If they are it's a possibility the clearance is just great enough to allow for somewhat normal operation but as the engine warms, and parts grow, these clearances shorten up and cause the exhaust cam followers to follow the engine braking profile. I can see how this could be inconsistent in operation.

I think I'd pull those rocker covers and give it a good overhead run before looking too much further. A compression test would be a good thing to do up front also. Got to have the bases covered to make sound and prudent judgement(s).

Rob

[rhasler]

While you're into the engine check the hydraulic lash adjusters on the exhaust rocker arms for sticking/binding.

[fjh]

Went and looked for any kind of wire today...no dice. There's no switch in the cab, no wire off of the fuel pump. I started it up for giggles and it ran just fine. I'm very confused. One other note, this engine is governed at 1800. Is that normal for the ETAZ?

From what I can see of the picture theres a wire to the valve cover disconect that also it apears there is a wire at the fuel pump on the little square cover that is where the switch is located if it is there!I have see lash ajusters stick from time to time That as others have mentioned will cause a miss and white blu smoke!The solnoids under the valve covers can work loose and can cause oil preasure to bypass the solnoid orings and go directly to the engine brake gallery in the rocker shaftThis causes a three cylinder miss and smoke!