help, car is running like crap after 1.7 roller rocker install

[black87gtbeauty]

i just recently installed 1.7 cobra rockers, now the car runs like hell, it idles fine, there are no engine noises like taps or knocks, but when you give it gas it sputters pretty bad and it feels like its only running on 4 cylinders. i have already replaced the tfi, cap and rotor and all the plugs, also all of the rockers adjusted perfectly i went through the firing order, brought them to 0 lash and tightened them 1/4 turn.

so if anyone has had something similar happen please help me out
thanks

 

[proxses]

I thought Cobra rockers were bolt down types?
I had a similar problem caused by the rockers holding the valves open just a bit.
Try backing off of them just a bit.
And what do your plugs look like, what are they gapped at?

 

[black94gt50]

make sure all ur vacuum lines are plugged up correctly and everything, alot of times that can cause things like this to happen

 

[Michael Yount]

Your technique for installing the rockers is incorrect. With the lifter on the base circle of the cam (valve closed) you need to tighten the bolt until you're at zero lash, then put a torque wrench on it and tighten to 18-20 ft-lbs. while counting the number of turns it takes to reach that torque - should occur between 1/4 and 1 turn.

Sounds to me like you have a vacuum leak of some sort, or something hooked up incorrectly. You didn't connect the egr valve directly to vacuum did you?

 

[04sleeper]

1/4 turn? They are the bolt down Cobra rockers right?

 

[Paul Perreca]

probably a vaccuum line - but usually the idle would be a little messed up by a vac leak wouldn't it?
Paul Perreca

 

[8950HO]

Your technique for installing the rockers is incorrect. With the lifter on the base circle of the cam (valve closed) you need to tighten the bolt until you're at zero lash, then put a torque wrench on it and tighten to 18-20 ft-lbs. while counting the number of turns it takes to reach that torque - should occur between 1/4 and 1 turn.

Sounds to me like you have a vacuum leak of some sort, or something hooked up incorrectly. You didn't connect the egr valve directly to vacuum did you?

I think it`s best to only use the torque wrench for the final torque spec...not to count the final number of turns for the lifter preload spec.

Here`s why.If you use the torque wrench method,it`s not as accurate.

Try this.Using a rachet,obtain zero lash...then tighten while counting the number of turns until you feel the rocker bolt "snug down",(you will feel this point).

Now at this point,there is no more lifter preload available....However.you are nowhere near the final torque spec of the rocker...see what I mean.The torque wrench method is not as accurate.Try it both ways and decide for yourself.

 

[trueblue01]

Isn't it different adjustment for stud and pedistal mount? He never said what heads.

 

[black87gtbeauty]

i have gt40 p heads so the rockers are pedestal mount, and im pretty shore that all of the vacuum are hooked up right, the only thing that i did diffrent this time is i plugged up the one vacuum line that goes from the front side of the maniflod to the smog canister, could that cause the problem or are the rockers the problem

 

[90mustangGT]

I had a similar problem once. I called CraneCams and they told me 3/4 to 1 1/2 turn.

Turn the bolt while rotating the pushrod back and forth with your fingers, and when you feel the tension and cant turn it with your fingers, you are at 0 lash. Then tighten down to 18-20lbs and you should only be able to turn 3/4ths to 1 1/2 turn.

 

[Michael Yount]

Crane Cams' website has a very clear description of the process --- go there and read; that's one of the sources of the 1/4 to 1 turn spec -- the number of threads/inch on the bolt combined with the geometry of the rocker translates 1/4 to 1 turn into the correct amount of preload on the lifter.

 

[90mustangGT]

Oh yeah, with the Crane Energizer series RR's, you need different pushrods. They don't tell you that, but I called crane when I had problems and they told me this and that it was common. The RR's from crane are cheapest, but there are hidden costs.

 

[jimilane]

The valve train is non-adjustable.

Torque to 25 and leave it. Then after a few minutes go back and retorque because some of the lifters will have been on the lobes. The vavlve spring will push the piston in the lifter, down into the lifter. This will loosen the torque just a little. This is the way I've done it many times with no problems.

I have never put the lifter on the base circle of the cam for non-adjustable valve trains...and haven't blown anything up.

One thing to watch for though is leaving parts out that will make the rocker sit lower to the head. If you preload the lifter too much, it will keep a valve open at higher RPMs.

I usually have about .020 - .030 preload. It's hard to check preload without the manifold off. The way I check the preload is to slide the end of a regular paperclip between the little wire clip and piston of the lifter. It should slide in with just a little resistance. You'll be able to tell. If you don't have the manifold off, you really can't check the preload that well. Zero lash, and then up to one turn will give you the correct preload. This is mainly checking for valvetrain geometry...

You can only change the amount of preload by changing the height of the rocker in this case.

If you do set it to zero lash, then turn it more than 1 time, you probably have left a part out. More than one turn will give you MORE preload then you need.

The lifter on the base circle is more for an adjustable valve train where YOU HAVE to set a certain preload YOURSELF. You find the zero lash with the lifter on the base circle, then tighten a certain number of turns for the preload. If you can measure the preload, you don't need to worry about how many turns you are making. You just need to worry about the hight of the rocker arm and where it's hitting the top of the valve.

You might want to check the geometry again. You might need some different parts.

Make sure the rocker isn't binding on the valve retainer from being to low.

Make sure the roller is not rolling too close to the edge of the valve.

Jim

 

[HappyG]

you use pedestal shims to adjust the "non-adjustable" pedestal rockers., they usually come with the set of pedestal mount rockers. if not order a set from crane or ford. if evrything is hooked up correctly, sounds like a valve is being held open.

 

[black94gt50]

yes i had 1.7's that were non adjustable before and the longer pushrods are a good idea.I just took them off and got stud mounted ones and converted my heads over to a screw in stud kit u can get the kit from comp cams.Its a real nice kit for the price u get everything u need plus pushrod guide plates, but thats a little extra money plus you would have to sell the rockers u have ow and buy new ones