Vt not starting after rocker install (backfires)

[losh1971]

Right now you need to refit your old rocker assemblies. There is no adjustment as such. You measure preload and go from there if the new rockers have to much preload then you could shim but until you have measured the preload and posted the results you won't know what thickness shim to need to have. Ideally you will measure the preload with the Hi Ratio Rockers and then order rods to suit. Too much preload and you could **** the cam.

 

[losh1971]

I had some problems when I fitted my 1.9 rockers and ended up removing each one and measured the preload as recommended. I then posted the results. Mine developed a bad rattle and I along with a few others thought it was the new rockers but it was something else that the extra lift which made other worn out components rear their ugly head.

 

[losh1971]

Do you even have a torque wrench that goes down to 25lb? If not you will struggle to get an accurate preload measurement.

Also not sure if you know or not but the original factory rocker bolts are TTY and need to be thrown away.

 

[07GTS]

if u have them loose and it seems ok u need to shim up the rockers to get proper pre load as has been mentioned, and also keep an eye on the roller/valve contact patch should be central, should not be running engine with loose rocker bolts just need to setup to suit properly

 

[Milesvtcalais]

if u have them loose and it seems ok u need to shim up the rockers to get proper pre load as has been mentioned, and also keep an eye on the roller/valve contact patch should be central, should not be running engine with loose rocker bolts just need to setup to suit properly

Yeah. Sigh. I've tried all afternoon. Can someone please tell me what shimming is and pre load? Anyone on the gold coast who can do it for me? I'll give you $100

 

[ant797]

Yeah. Sigh. I've tried all afternoon. Can someone please tell me what shimming is and pre load? Anyone on the gold coast who can do it for me? I'll give you $100

Just put the old kit back in and have a beer guaranteed even if you do get it working by the sounds of it going to be a constant drama

 

[07GTS]

shimming is a measured way to lift up the rocker to suit which also can change the rocker/valve contact area which u need to keep central, u usually adjust the rocker height to make the contact central thru its motion then adjust push rod length to suit pre load, too much pre load and valves stay open or too little and u can damage the valves

 

[strgas]

Pre load is the pushrod on the lifter . To much preload like you had sees the pushrod to far or too much preload and can bottom out the lifter plate inside the lifter turning it from hyd lifter to a solid lifter in turn holding the valve open .
To little preload can lead to top end rattle and hammering of the lifter and dislodging the lifter clip into the sump then the oil pump destorying the engine . Longer pushrods are used when the cam has been ground and the base circle reduced enough to require a longer to now matcj new lobe profile .

 

[losh1971]

Just put the old kit back in and have a beer guaranteed even if you do get it working by the sounds of it going to be a constant drama

HRR can make a decent improvement over stock and once set up right shouldn't cause any ongoing problems. Mine are awesome and certainly increased the RWKW. But they need to be set up right and yes if not done right it can cause issues.

 

[losh1971]

TBH if your preload is so much that it's opening valves I think the rods are too long. My HRRs really needed more preload on some valves, none of them had too much. The problem with a second hand set of Comp Cam ones is as sort of mentioned they may have been designed for an aftermarket cam and not stock.