Gear drives are a terrible device.Transfer severe vibrations and harmonics to the cam from the crank. They do absolutely nothing for performance but appeal to the boast factor. Bill Jenkins used for years the stock plastic gear and link style chain. Said because it is a low mileage app the plastic gear would never get enough age to fail. Many good experienced builders use Cloyes or Melling industrial (truck engine)roller chains. The true rollers so hyped wear at a ferocious rate due to the excessive number of parts involved in rollerizing a roller chain. If folks really wanted to make a significant difference in cam drives they would without question use a toothed belt conversion. The quality of that has no equal. To the valve train it is like an ice cream cone would be to us on a 99F day. I use the stock link chain with a steel gear or a truck style Cloyes or Melling roller. In the last few years I did drag motors I have chucked brand new shiny lightened holes blister packed gear sets in the garbage can. They are rarely accurate and I have had one out 11 degrees and one set out 7. In both cases I pulled a Cloyes truck chain set up or stock 426 hemi setup and discovered they were bang on the money and didn't even require an offset. Why spend more for junk? It doesn't make sense. The new hemi may have some issues but millions have been built and are on the road. Hopefully Cloyes makes a replacement. don
-- Edited by Don on Friday 7th of November 2014 02:37:32 PM
-- Edited by Don on Friday 7th of November 2014 02:40:38 PM
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SR Dragster because old people need to have fun too!
The chain is breaking because the computer puts the engine into 4 cylinder mode can someone explain? My idea was to shut off 4 injectors but are the valves held open or what puts more stress on the chain?
Randy, you are correct in that, the fuel flow to the injectors is cut off...But, also the valves on those 4 cylinders remain closed, using VVTI (Variable Valve Timing) technology. Somehow with the valves closed, they are able to pump air through those cylinders, so not to lose power from the compression. I have no idea how they are able to achieve this.
But I'm thinking that this is likely the reason why the tension in the timing chain increases when the engine switches over to 4 cyl., maybe the electronic system has a dwell, or something, that cause the 4 de-activated cylinders to run at full compression for a split second.
The Hemi, is an interference engine, which means the valves will hit the piston, if they remain open.
-- Edited by Gazoo on Saturday 8th of November 2014 06:03:41 PM
The MDS system when active puts less stress on the chain. The lifters are what drop the 4 cylinders. Lifters are oiled last, they have solenoids in the valley for 4 cylinders to not allow them to pump up.
System has been around since 05, I bet its bad parts. Tensioner likely breaks first. Maybe chain slaps a bit when MDS is on.
Vvt is controlled in the cam sprocket.
Non vvt engines 03-08 seem to be fine.
Maybe when MDS and cam timing changes puts slack in the chain.
I have an 03 5.7 and 2010 6.1, both are not effected, I may use a double roller chain when I get around to using them.
