Joseph Pickarts Posted January 15, 2016 Share Posted January 15, 2016 I have a 1990 rb with a '79 235 motor. The tag says its an etz 675. It's not stock. Has an air to air, bosch injection pump and mated up to a 13spd. Just kind of wondering what these had for Jake's and whether it would be a dynatard or Jake Brake. Also how to tell if it's a 2v head. I just can't find much about it on the internet.Thanks Quote Link to comment https://www.bigmacktrucks.com/topic/43517-79-mack-235hp-jake-brake/ Share on other sites More sharing options...
Superdog Posted January 15, 2016 Share Posted January 15, 2016 a 675 could have either a Jake or dynatard.Easiest way to tell a 2 valve head is the injectors go in the top. Quote Link to comment https://www.bigmacktrucks.com/topic/43517-79-mack-235hp-jake-brake/#findComment-320009 Share on other sites More sharing options...
Joseph Pickarts Posted January 15, 2016 Author Share Posted January 15, 2016 So my next question would be what is the best way to tell the difference. It has some setup that doesn't work. Has the 12v running to the valve covers and has the electric selenoids under which I would assume runs off oil pressure? Quote Link to comment https://www.bigmacktrucks.com/topic/43517-79-mack-235hp-jake-brake/#findComment-320010 Share on other sites More sharing options...
b61mack Posted January 15, 2016 Share Posted January 15, 2016 If it is a jake it would have a spacer about 2-3" under the valve cover with a wire going thru the plate, if dynatard it would have a wire on top of valve cover. a 2 valve will have a stamped steel valve cover. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/43517-79-mack-235hp-jake-brake/#findComment-320043 Share on other sites More sharing options...
Joseph Pickarts Posted January 16, 2016 Author Share Posted January 16, 2016 Does anybody know the best way to get a rebuild kit for the dynatard or would I be best off switching it to a Jake style? Quote Link to comment https://www.bigmacktrucks.com/topic/43517-79-mack-235hp-jake-brake/#findComment-320129 Share on other sites More sharing options...
b61mack Posted January 16, 2016 Share Posted January 16, 2016 A Dynatard is nothing more than a noise maker, a Jake on a E6 Mack is a little better. Watts sells Tecbrake same as Jakebrake. you might give them a call, they can get some hard to fine parts. Quote Link to comment https://www.bigmacktrucks.com/topic/43517-79-mack-235hp-jake-brake/#findComment-320161 Share on other sites More sharing options...
Joseph Pickarts Posted January 18, 2016 Author Share Posted January 18, 2016 So I did some investigating. From what I gathered most motors equipped with a factory installed dynatard had a b in the engine model. And it takes a special cam to work the dynatard. So if my engine is stamped etz675 does that mean it doesn't have that cam and the dynatard was added later in the motors life? Quote Link to comment https://www.bigmacktrucks.com/topic/43517-79-mack-235hp-jake-brake/#findComment-320400 Share on other sites More sharing options...
theakerstwo Posted January 18, 2016 Share Posted January 18, 2016 A safe way to check is pull a valve cover and have some one turn the engine slow while you check valve clearance on a exhaust valve.If it has a dynotard cam at some point your going to have about a 1/8 lash.If you never find that lash it may not be a dynotard cam. Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/43517-79-mack-235hp-jake-brake/#findComment-320411 Share on other sites More sharing options...
Joseph Pickarts Posted January 20, 2016 Author Share Posted January 20, 2016 Okay so now say it does have a dynatard cam. And I have power to the valve covers. What would my next step be. Replacing the selenoids and seals under the valve cover? Quote Link to comment https://www.bigmacktrucks.com/topic/43517-79-mack-235hp-jake-brake/#findComment-320848 Share on other sites More sharing options...
theakerstwo Posted January 21, 2016 Share Posted January 21, 2016 Have you check to see if you are getting current to the wires on the valve covers? Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/43517-79-mack-235hp-jake-brake/#findComment-320891 Share on other sites More sharing options...
Joseph Pickarts Posted January 24, 2016 Author Share Posted January 24, 2016 Yes. I am getting the propper 12v to the valve covers Quote Link to comment https://www.bigmacktrucks.com/topic/43517-79-mack-235hp-jake-brake/#findComment-321409 Share on other sites More sharing options...
theakerstwo Posted January 25, 2016 Share Posted January 25, 2016 The pull the covers and when running apply 12 volts to each selnoild to see if they are working.Also look for oil leaks on the rocker shaft. Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/43517-79-mack-235hp-jake-brake/#findComment-321422 Share on other sites More sharing options...
Joseph Pickarts Posted January 30, 2016 Author Share Posted January 30, 2016 Selenoids are working with 12v applied. Didn't take off valve covers but could see through crankcase vent holes Quote Link to comment https://www.bigmacktrucks.com/topic/43517-79-mack-235hp-jake-brake/#findComment-322212 Share on other sites More sharing options...
br549 Posted January 30, 2016 Share Posted January 30, 2016 If memory holds correct, when we would buy an new dynatard switch for the 2 valves it always came with a spacer ring about 1/8" thick, every truck we pulled apart did not have the spacer ring in it. It seem like we had found some under the solenoids when they wasn't working good and we took them out and they worked better. I assume some of the first ones used, but I never seen one that did, it came with a new one and I guessed people just put it in there. We found a lot of solenoids that would come loose where they thread into the rocker arm. You might try a valve adjustment. It's doubtful but you might ck and see if mack still offer's mack remack dynatard rocker arm for the engine. Quote Link to comment https://www.bigmacktrucks.com/topic/43517-79-mack-235hp-jake-brake/#findComment-322213 Share on other sites More sharing options...
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