BronsonA2150 Posted January 24 Share Posted January 24 My 94 e7 has an engine brake, but I’m not sure if it’s Jacob’s, dynatard or something else if there is anything else. How do I tell? I don’t see Jacob’s anywhere on the housing like my Cat has Quote Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/ Share on other sites More sharing options...
Freightrain Posted January 24 Share Posted January 24 I would assume Jacob would still have the valve cover spacer to make room. I thought dynatard was internal and wouldn't need the spacer. My .02 1 Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-567568 Share on other sites More sharing options...
tjc transport Posted January 24 Share Posted January 24 if the engine tries to shut off at idle with engine brake on, it is a Jacobs. if the engine brake shuts off at idle on it's own with switch still on, it is a dynatard 2 Quote when you are up to your armpits in alligators, it is hard to remember you only came in to drain the swamp.. Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-567582 Share on other sites More sharing options...
BronsonA2150 Posted January 24 Author Share Posted January 24 19 minutes ago, tjc transport said: if the engine tries to shut off at idle with engine brake on, it is a Jacobs. if the engine brake shuts off at idle on it's own with switch still on, it is a dynatard You sure about that? Mine has electronic throttle so I figured anything would be wired through computer to shut off with rpm, throttle, etc. Quote Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-567589 Share on other sites More sharing options...
fjh Posted January 24 Share Posted January 24 23 minutes ago, BronsonA2150 said: You sure about that? Mine has electronic throttle so I figured anything would be wired through computer to shut off with rpm, throttle, etc. Look at the engine if there is a 2 inch spacer between the valve cover and the head its a jake! Quote Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-567595 Share on other sites More sharing options...
Joey Mack Posted January 24 Share Posted January 24 I bet its Jacobs 680 Quote Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-567598 Share on other sites More sharing options...
BronsonA2150 Posted January 24 Author Share Posted January 24 19 minutes ago, fjh said: Look at the engine if there is a 2 inch spacer between the valve cover and the head its a jake! Appears to be! Quote Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-567600 Share on other sites More sharing options...
Joey Mack Posted January 24 Share Posted January 24 Jacobs 2 Quote Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-567602 Share on other sites More sharing options...
The Heinz Posted January 24 Share Posted January 24 It'll be a 680, possibly a 680B. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-567604 Share on other sites More sharing options...
tjc transport Posted January 24 Share Posted January 24 3 hours ago, BronsonA2150 said: You sure about that? Mine has electronic throttle so I figured anything would be wired through computer to shut off with rpm, throttle, etc. sorry, i missed the 94 year in your post. i was referring to mechanical engines. 1 Quote when you are up to your armpits in alligators, it is hard to remember you only came in to drain the swamp.. Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-567625 Share on other sites More sharing options...
BronsonA2150 Posted January 24 Author Share Posted January 24 2 hours ago, The Heinz said: It'll be a 680, possibly a 680B. Either one of those work better than the other? Quote Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-567626 Share on other sites More sharing options...
fjh Posted Saturday at 01:02 PM Share Posted Saturday at 01:02 PM nope its crap shoot if they work better or not! Oil pressure was an alleged problem with these ! They added an external oil line kit sort of helped! But problem being were only cracking one valve open ! Again not getting rid of all the compression needed for good braking ! Just my opinion! 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-567647 Share on other sites More sharing options...
The Heinz Posted Monday at 02:44 PM Share Posted Monday at 02:44 PM On 1/24/2025 at 5:53 PM, BronsonA2150 said: Either one of those work better than the other? I don't know if any of them are better than the other, I don't think there was much difference between them. Quote Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-567840 Share on other sites More sharing options...
Joey Mack Posted Monday at 02:45 PM Share Posted Monday at 02:45 PM They suck... 2 Quote Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-567841 Share on other sites More sharing options...
Joey Mack Posted Monday at 03:05 PM Share Posted Monday at 03:05 PM If you need lash specs. I can post pictures from the book. I will need to know HP, Turbo type and p/n. Quote Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-567844 Share on other sites More sharing options...
BronsonA2150 Posted Monday at 06:43 PM Author Share Posted Monday at 06:43 PM 3 hours ago, Joey Mack said: If you need lash specs. I can post pictures from the book. I will need to know HP, Turbo type and p/n. Yes I probably will when I do an overhead. By the way, where do you come up with Mack repair manuals? Website I ordered my cat stuff from has nothing for Mack Quote Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-567875 Share on other sites More sharing options...
Joey Mack Posted Monday at 06:45 PM Share Posted Monday at 06:45 PM I worked for Mack for 12 years. I went to several schools,and co workers would also give me their books.. 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-567878 Share on other sites More sharing options...
cruiseliner64 Posted Monday at 07:25 PM Share Posted Monday at 07:25 PM 39 minutes ago, Joey Mack said: I worked for Mack for 12 years. I went to several schools,and co workers would also give me their books.. Lucky sod..... Paul 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-567886 Share on other sites More sharing options...
67RModel Posted Monday at 08:04 PM Share Posted Monday at 08:04 PM Did / does Pacbrake make a compression brake for E7s? Quote Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-567889 Share on other sites More sharing options...
BronsonA2150 Posted 8 hours ago Author Share Posted 8 hours ago On 1/25/2025 at 7:02 AM, fjh said: nope its crap shoot if they work better or not! Oil pressure was an alleged problem with these ! They added an external oil line kit sort of helped! But problem being were only cracking one valve open ! Again not getting rid of all the compression needed for good braking ! Just my opinion! Interesting. So I’m brand new to these engines. These Jakes only open 1 valve? On my 3406 the slave pushes down the bridge therefore opens both. I have it in for an overhaul right now and have been doing a fair bit of research for the Jake on it as they were always pretty less than impressive also unless you could find the diamond in the rough 349a. But it looks like the Jacob’s version for these Mack’s are the same operating principal as the more common (poor performing) 346’s on the 3406 cats according to the brochures. As you said, I think lack of oil pressure was the big reason they didn’t perform well. The 349a’s cured that with a trigger piston and larger oil reservoir to increase pop reaction, but supposedly the triggers wore in the bore and made them junk after so many uses Quote Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-568192 Share on other sites More sharing options...
Joey Mack Posted 7 hours ago Share Posted 7 hours ago On Jacobs, oil pressure is let in through the electric celenoid and it opens the outer exh valve via a piston pushing on a reset screw in the bridge. The inner exh valve is also opened during normal cam operation during deceleration. Quote Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-568194 Share on other sites More sharing options...
Mark T Posted 7 hours ago Share Posted 7 hours ago 15 minutes ago, Joey Mack said: On Jacobs, oil pressure is let in through the electric celenoid and it opens the outer exh valve via a piston pushing on a reset screw in the bridge. The inner exh valve is also opened during normal cam operation during deceleration. That's a 690 Quote Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-568195 Share on other sites More sharing options...
Joey Mack Posted 7 hours ago Share Posted 7 hours ago And 680's. Dynatard is all different.. where am i wrong. I am rusty. Quote Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-568196 Share on other sites More sharing options...
Mark T Posted 7 hours ago Share Posted 7 hours ago The 690 has the pin through the bridge. 680s have the legs that hit the bridge Quote Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-568197 Share on other sites More sharing options...
Joey Mack Posted 7 hours ago Share Posted 7 hours ago Yep. That's right. Pushes the bridge opening both valves.. Quote Link to comment https://www.bigmacktrucks.com/topic/75063-what-engine-brake-do-i-have/#findComment-568198 Share on other sites More sharing options...
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