hawk2881 Posted February 2, 2009 Share Posted February 2, 2009 I have this 1975 rs700 l with the 866 V8 and the 12 speed trans. it has 330,456 original miles on it, that came from army corp. of engineer. I was woundering when should the main and rod bearings be rolled, and the turbo change out, and what is the valve adjustment intervals? The Dynatard engine break seem's weak, what kinda tune up spec's are there that i can check to see if it is just out a spec. On the mack 12 speed trans is there a filter that needs to be changed looks like a filter up on top of it but i can not get to it very well to see what it is, cant get it off scared going to break off the mounting brackets. Also this truck has a 18000 pound fron axle is this common in this series a truck or if this a after market something. What is the steering box worm gear end play spec's. What is the turbo boost pressure at full fuel at hard pull what is normal oil pressure engine hot at idle and at like 1800 rpm what is oil spec's for the engine multi grade or like a 30wt. what is the factory governed rpm what is the exhaust temp max at hard pull?Sorry so many quastions but i know nothing about mack engines and I really need this truck to keep my grinding operation going. thank you for all that reply. Quote Link to comment https://www.bigmacktrucks.com/topic/8187-when-to-turn-the-main-bearings/ Share on other sites More sharing options...
fjh Posted February 2, 2009 Share Posted February 2, 2009 I have this 1975 rs700 l with the 866 V8 and the 12 speed trans. it has 330,456 original miles on it, that came from army corp. of engineer. I was woundering when should the main and rod bearings be rolled, and the turbo change out, and what is the valve adjustment intervals? The Dynatard engine break seem's weak, what kinda tune up spec's are there that i can check to see if it is just out a spec. On the mack 12 speed trans is there a filter that needs to be changed looks like a filter up on top of it but i can not get to it very well to see what it is, cant get it off scared going to break off the mounting brackets. Also this truck has a 18000 pound fron axle is this common in this series a truck or if this a after market something. What is the steering box worm gear end play spec's. What is the turbo boost pressure at full fuel at hard pullwhat is normal oil pressure engine hot at idle and at like 1800 rpmwhat is oil spec's for the engine multi grade or like a 30wt.what is the factory governed rpmwhat is the exhaust temp max at hard pull?Sorry so many quastions but i know nothing about mack engines and I really need this truck to keep my grinding operation going. thank you for all that reply.I don't have all of your answers But heres a coupleIf the engine is indeed a 375 hp then it should be (painted silver and have a 12 speed behind it.)-2150 to 2300 rpm is fine perfer 2150 loadednote if the no load rpm goes adove the 2100 say closer to 2500 then it is 325 hp engine The valve set wil be intake 16 exhast 24 for either.-Boost sume where around 15- 20 psi'!(Guessing on this one)-pyro 1000-1150-Dynatard is always weak get use to it! -oil psi 30-40 idle 650 rpms-oil recomend 15/40 -30 w ok-turbo depending on how hard it was worked ,replacing the turbo not a bad idea depending on what your plans are to do with the truck.-Bearings is a work thing ,if it has 10 to 15000 hours on the clock not ,a bad idea to roll in NEW bearings !- axle it may have been born with that axle depending on application crane dump ect.The steering end play thing is not somthing I put in the memory bank sorry!good luck with your unit! Quote Link to comment https://www.bigmacktrucks.com/topic/8187-when-to-turn-the-main-bearings/#findComment-30238 Share on other sites More sharing options...
Packer Posted February 2, 2009 Share Posted February 2, 2009 I don't have a lot of experance with Dynatards butJake brakes will break down the 'O' rings and let oil seep by.This will cause the brake to loose it's effectiveness.A set of 'O' rings, a pick and some 'O' ring grease might make a great differance.This can be done on the engine in maybe an hour.Also, make sure the valve settings and Dynatard lash is on the money.Packer Quote Keep a clutchin' Link to comment https://www.bigmacktrucks.com/topic/8187-when-to-turn-the-main-bearings/#findComment-30240 Share on other sites More sharing options...
fjh Posted February 2, 2009 Share Posted February 2, 2009 I don't have a lot of experance with Dynatards butJake brakes will break down the 'O' rings and let oil seep by.This will cause the brake to loose it's effectiveness.A set of 'O' rings, a pick and some 'O' ring grease might make a great differance.This can be done on the engine in maybe an hour.Also, make sure the valve settings and Dynatard lash is on the money.PackerPacker has a good thought there! I have seen the solnoids come loose check em while doing the valve set !(Which by the way will set the dynatard as well its built in to the rocker!)Also you can cheat some on this setting to get better performance set your exhast to 22 or real tight to 23!A little bit goes along way. 0 Quote Link to comment https://www.bigmacktrucks.com/topic/8187-when-to-turn-the-main-bearings/#findComment-30243 Share on other sites More sharing options...
mackmixer Posted February 3, 2009 Share Posted February 3, 2009 "I was woundering when should the main and rod bearings be rolled,"You can measure the clearance of the main and rod bearings with Plastigage to help you decide whether to roll new ones in.Do the mains individually so the crankshaft will still be centered with adjacent main bearings pulled up tightly.Be sure to remove all the Plastigage that squeezes on the crankshaft.......... Quote David Link to comment https://www.bigmacktrucks.com/topic/8187-when-to-turn-the-main-bearings/#findComment-30260 Share on other sites More sharing options...
hawk2881 Posted February 10, 2009 Author Share Posted February 10, 2009 Packer has a good thought there! I have seen the solnoids come loose check em while doing the valve set !(Which by the way will set the dynatard as well its built in to the rocker!)Also you can cheat some on this setting to get better performance set your exhast to 22 or real tight to 23!A little bit goes along way. 0 thank you all for your help!! I am not understanding the valve settings? I have not yet pulled the valve cover to loook yet but would .023 be less tight than .022. my engine is silver and has a 12 speed mack trans. behind it and 44,000 ibs axles with 18,000 front. this is the nicest 1975 trk i have ever seen looks like it just came off the lot, not a scratch. i am using this trk to haul wood grindings out of the mountains to a generation station to make electricity. this trk is almost to nice to drive in the mountains. I not sure if it a good deal but i got it for 5k with new tires all the way around. The o-rings that i should check are they easy to see, or anyone have a book i can buy. or know where i can buy one thanks again for everyones help Jeremy Quote Link to comment https://www.bigmacktrucks.com/topic/8187-when-to-turn-the-main-bearings/#findComment-30543 Share on other sites More sharing options...
fjh Posted February 11, 2009 Share Posted February 11, 2009 23 is looser than 22 .silver indicates that likly You have a 375 hp engine then.Once the valve cover is off the orings are under the solnoid in the middle of the rocker ! if the solnoid is tight the orings will be fine! Quote Link to comment https://www.bigmacktrucks.com/topic/8187-when-to-turn-the-main-bearings/#findComment-30605 Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.