i installed crane 1.6 roller rockers and after the install my car idles at 1000-1200 sometimes and then when it comes down to 800rpms it will surge up and down.the engine is a 93 speed density.performance is fine and they are not noisy either.thanks in advance for any help.

 

hate to say it but you're gonna have to re-run the valves. sounds to me like they're too tight chief. if thats the case the valve isnt being allowed to close properly.

 

Would that make it surge like that? What way do you recommend installing them?

 

All the valves were set at 1/2 turn past zero lash. Thats not too tight. I never had this problem before and have set many valves. The directions call for 1/2 - full turn past zero lash.

 

anyone else have any ideas?

 

Put a vacuum gauge on your intake, if the needle is bouncing, recheck the valve lash. If you have access to a scanner, check the MAP for the same thing. Good luck.

 

so you say if the map sensor numbers are bouncing around you think the valves need reset?

 

Check your vacuum, and double check the rockers...

 

MAP, vacuum, same thing. If it is erratic, then you probably have some tight valves.

 

i will check my vacume reading.....thanks

 

Valve lash too tight.

I've been through it.

If they are ProMagnums, I only went 1/4 turn past. 1/2 turn was too much on my heads.

 

the map sensor is only reading 8hgs ov vacume at idle when warmed up.

 

and please dont do what i did. Mine were to tight the first time and my first cam..... ended up shaving my cam and replacing a bunch of stuff that could of been avoided. Now the car is in the shop getting a bent valve replaced and a nice valve job, new lifters, and new 1.5 rr's non-self aligning. shouldnt have the problem again after this either

good luck

-Mike

 

ttt

 

MAP isn't the same as vacuum, it the "opposite" of vaccum.

Barometer - MAP = vacuum

A stock cam will pull 20"Hg. Barometer is typically 30"Hg.

30 - 20 = 10"Hg = typical MAP reading in a stock cam.

8"Hg at idle seems a little on the low side for MAP (22"Hg vacuum), although mine would bump into the high 8.X's at times when the cam was stock.