Ford Mustang Forum banner

1 - 20 of 20 Posts

·
Registered
Joined
·
213 Posts
Discussion Starter #1
Recently did a carb conversion on my 91 5.0. I figured it would be a good time to put new lifters and pushrods in. When I finished up the motor, and fired it up- the lifters and or rockers were clattering. I thought that maybe the lifters had to prime. After about 5-10 minutes shut the car off and pulled a valve cover to investigate. My rockers arms are torqued down(25lb-ft) but rockers are loose. I'm thinking either the lifters didn't prime, pushrods are too short or lifters are a different height. They are Summit lifters and Comp Cams pushrods. What am I doing wrong??!! This was not making a peep before I swapped the lifters and pushrods.
 

·
Registered
Joined
·
887 Posts
Are you sure you got the right sizes? They could have even accidentally sent you 2 different sizes(1.6/1.7)
 

·
Registered
Joined
·
6,328 Posts
what rockers are you using? what length pushrods did you buy?
 

·
Registered
Joined
·
13,138 Posts
What rockers are you using? What ratio? What length pushrods did you buy? What cam are you using?
 

·
Registered
Joined
·
213 Posts
Discussion Starter #5
Rockers are the stock pedestal mount rockers. Pushrods are stock length. Its almost as if maybe the lifters are a different height or the plunger sits down farther causing the lifters to sit down farther. The cam hasn't changed.......the only thing that has changed are the lifters and pushrods. Both are oem replacements. I pushed down on the rockers on the pushrod side and the lifters feel tight(primed up) but maybe they are not? Or the lifters are a different height. Also- I didn't prime the lifters beforehand.
 

·
Registered
Joined
·
6,328 Posts
did you use the proper procedure to tq them down? lifter should be on the base circle of the cam...unless the summit brand is a different length..
have you tried to pull the distributor and prime the motor using a drill? to make sure the oil pump is working?
 

·
Registered
Joined
·
36 Posts
If these are factory rockers, there is no procedure unless I was told different. The way I was told, install them and torque to 25lb ft and your done. Is this not correct? And would the lifters not be primed by now especially after a 10 minute idle? (read 1st Post)

I am also in the same boat as SilverPony. I installed only new lifters and mine are loose as well. I was told that I had weak springs and yes I can open the valves by hand with a socket and extension pushing down on the spring only. The weak springs make sense but why only after new lifters?

Scott
 

·
Registered
Joined
·
36 Posts
I installed Melling lifters but not sure of the part number. I let mine soak over night and I made sure that all lifters were down in there bore before I installed the rockers. Now whether they were on the intake side or the exhaust side is questionable. Mine still rattled for a few seconds and then quietend down but they still rattle at certain points as I drive. I used the same rockers and the same pushrods so that shouldn't be the problem. Can you pull a pushrod and check the length or at least check with Summit to get the length they are supposed to be? Also check and see if you can open a valve by hand. You may also be able to find out the dimensions of your lifters if you search enough.

Scott
 

·
Registered
Joined
·
213 Posts
Discussion Starter #11
Guys- I may be wrong here, but I think there is an issue with aftermarket lifters being a different height. As far as the procedure for tightening them down, I'm obviously no expert, but why would they have to be on the base circle of the cam when your tightening down against the pedestal? Either way, I did try to both methods of bolting them down, but still came up with loose rocker arms. I did some checking and the comp cams pushrods for this motor are 6.248 inches. The Ford racing pushrods are 6.270. Yet both are oem replacements!! Whats to say summit lifters aren't different than the stockers? By the way- I did install the old pushrods- they tightened up the rockers only slightly. Still loose though.
 

·
Registered
Joined
·
213 Posts
Discussion Starter #13
Yup- gonna get an adjustable pushrod. Any tips on how to do this? Thanks for all the feedback so far.
 

·
Registered
Joined
·
6,328 Posts
to use an adjustable pushrod,you either have to convert a hyd. lifter to solid(in your case,you'll have to convert a new one since they are a different brand,to rule out different size from ford lifters),then measure,then add in your desired pre-load..you'll also need an 8" caliper for this,to measure the adjustable pushrod..you'll then have to convert the lifter back to normal after you measure

less preload = more noise..preload spec is .020-.060"

or..you can remove your valve springs,install soft checking springs,remove the dizzy,prime the lifters by spinning the oil pump with a drill,then measure..the lifters wont bleed down with the soft spring pressure

if you try to measure with stiff valve springs and a hydraulic lifter,the lifter will bleed down too quick and you'll never get an accurate measurement

maybe you should just buy some ford replacement lifters lol

FWIW,stock pushrod length is 6.272"
 

·
Registered
Joined
·
213 Posts
Discussion Starter #15
Funny you should say that! I bought some Ford racing lifters from Summit, along with new Ford racing pushrods, only to find that "custom pushrods" may be required. WTF?!! So now.........pull the intake and swap lifters, or no? I'm going INSANE!!
 

·
Registered
Joined
·
6,328 Posts
thats your call lol

you already have a second new set of lifters?
 

·
Registered
Joined
·
6,328 Posts
As far as the procedure for tightening them down, I'm obviously no expert, but why would they have to be on the base circle of the cam when your tightening down against the pedestal?
just to clear it up,when the lifter is on the base circle,the valve is closed..you dont want to install the rocker and tq it down when the lifter is at peak lift on the cam lobe(valve would be open)..might not get a proper tq reading,preload,etc..
 

·
Registered
Joined
·
6,328 Posts
anytime you change ANYTHING in the valvetrain,pushrod length needs to be measured..period.
 
1 - 20 of 20 Posts
Top