Switched From Dynatard To Jake

[MACKTRUCKS4]

Awhile back I had my cam reground in my 1994 E-7 400, one of the lifters went bad. The motor had a Dynatard on it and I replaced it with a Jake. From what I gather that cam was ground for a Dynatard from the factor. Now the problem I have is seems the Jake does not work like it does on my 2000 V-MAC III, which was built from the factory. It seems to work as good as the Dynatard did, which was not that good. I set the valves as I should for a Jake, but when I turned over the motor to go to the next valve in order, I went back to the other valves that I already set, and it seemed they were really loose ( like they were going to make noise, but they didn't) I was wonding if the valves should be set differently? I went over the valves twice to make sure I did them right and I'm sure I did. Could the settings on the Jake be tightened up to make the Jake work better? Like say .060" I have the setting on the slave piston set at .080" as per Jacobs installation chart. Oil pressure is 30lbs @ idle and 60lbs. @2000RPM. The Jake I used was a new set-up, so I don't think it needs to be rebuilt. Model is a 680B

[rhasler]

Awhile back I had my cam reground in my 1994 E-7 400, one of the lifters went bad. The motor had a Dynatard on it and I replaced it with a Jake. From what I gather that cam was ground for a Dynatard from the factor. Now the problem I have is seems the Jake does not work like it does on my 2000 V-MAC III, which was built from the factory. It seems to work as good as the Dynatard did, which was not that good. I set the valves as I should for a Jake, but when I turned over the motor to go to the next valve in order, I went back to the other valves that I already set, and it seemed they were really loose ( like they were going to make noise, but they didn't) I was wonding if the valves should be set differently? I went over the valves twice to make sure I did them right and I'm sure I did. Could the settings on the Jake be tightened up to make the Jake work better? Like say .060" I have the setting on the slave piston set at .080" as per Jacobs installation chart. Oil pressure is 30lbs @ idle and 60lbs. @2000RPM. The Jake I used was a new set-up, so I don't think it needs to be rebuilt. Model is a 680B

It sounds like you already know this, but it can't hurt to check. The valves should be adjusted cold (temperature stabilized below 100 degrees) and static (engine stopped) in firing order 153624. Valves are adjusted at 30 degress after TDC. Make sure to use the correct valve set marks on the flywheel. It will take two complete revolutions of the engine to adjust all of the valves. Intake valve lash is .016" exhaust is .024". Later camshafts (1996 and later I believe) had different valve settings for the exhaust valves. The exhaust valves on the later cams were adjusted to .028".

[fjh]

The jake does not work any better than a dynard on these engines .Comparing it to a more modern engine is not a fair comparison.As for the set what you experianced is normal for setting valves on a dynatard cam (loose valve lash 1 back).Your set is fine! I would not atempt tweaking the jake set any more than 1 or 2 thou tighter you could end up with bent valves.80 to 85 depending on turbo #nos is spec i beleive.

[theakerstwo]

I have worked on engines since the jake started and i have seen and corected the fact that some guys have tighen the jake lash up and that is only a story they hear on the radio. Like been stated be carefull with the lash and dont experment withe the lash setting. Here is a look at why your tighter than factory lash setting will not help but be some less than usefull.When you set lash closer than it should be that makes the valve start to open faster due to the timing efect on lesser lash. Of if the valve opens faster now or another way of looking at it the piston will be at a lower postion in the hole than normal so that means the air being compressed to use as a compression brake is not compressed as much as if the piston was alowed to come on up at a normal postion.The pop off air pressure is not as much now is another way of looking at it.If you put more lash in the jake it would let the piston be at a higher postion in the hole and would be a better brake but dont you know jake brake has tested this and found the best lash for that brake. They have all to lose and nothen to gain by printing the incorrect lash info.I have hear this story since the early 60s and if dont help to try and change what has been tested.When you play with the jake lash you stand a change of having valve to piston contact if another problem was to happen.I also have found there is not any difference in the braking power in the two brake systems. If you have all of the parts for the dynatard and want to sell them contact me.

[fjh]

I have worked on engines since the jake started and i have seen and corected the fact that some guys have tighen the jake lash up and that is only a story they hear on the radio. Like been stated be carefull with the lash and dont experment withe the lash setting. Here is a look at why your tighter than factory lash setting will not help but be some less than usefull.When you set lash closer than it should be that makes the valve start to open faster due to the timing efect on lesser lash. Of if the valve opens faster now or another way of looking at it the piston will be at a lower postion in the hole than normal so that means the air being compressed to use as a compression brake is not compressed as much as if the piston was alowed to come on up at a normal postion.The pop off air pressure is not as much now is another way of looking at it.If you put more lash in the jake it would let the piston be at a higher postion in the hole and would be a better brake but dont you know jake brake has tested this and found the best lash for that brake. They have all to lose and nothen to gain by printing the incorrect lash info.I have hear this story since the early 60s and if dont help to try and change what has been tested.When you play with the jake lash you stand a change of having valve to piston contact if another problem was to happen.I also have found there is not any difference in the braking power in the two brake systems. If you have all of the parts for the dynatard and want to sell them contact me.

Glen Having said what you have said About the jake is all true! The dyna tard being a diftrent animal I have set the exhast a little tighter on them and had some good results acheiving better engine braking even three thou tight on the exhast provides better engine braking But you need to be mindfull of the rpms you DO not want to go into over speed AT ALL with the tight setting.

[MACKTRUCKS4]

I have worked on engines since the jake started and i have seen and corected the fact that some guys have tighen the jake lash up and that is only a story they hear on the radio. Like been stated be carefull with the lash and dont experment withe the lash setting. Here is a look at why your tighter than factory lash setting will not help but be some less than usefull.When you set lash closer than it should be that makes the valve start to open faster due to the timing efect on lesser lash. Of if the valve opens faster now or another way of looking at it the piston will be at a lower postion in the hole than normal so that means the air being compressed to use as a compression brake is not compressed as much as if the piston was alowed to come on up at a normal postion.The pop off air pressure is not as much now is another way of looking at it.If you put more lash in the jake it would let the piston be at a higher postion in the hole and would be a better brake but dont you know jake brake has tested this and found the best lash for that brake. They have all to lose and nothen to gain by printing the incorrect lash info.I have hear this story since the early 60s and if dont help to try and change what has been tested.When you play with the jake lash you stand a change of having valve to piston contact if another problem was to happen.I also have found there is not any difference in the braking power in the two brake systems. If you have all of the parts for the dynatard and want to sell them contact me.

I have all the dynatard parts and want to sell them. I sent you a PM.