Lifter preload

[Micks87]

I just got my TR back together after a blown head gasket. With a fully charged battery, I fired it up and it cranked real slow and seemed as though something was too tight. I let it run for 30 mins. I restarted it the next day and it cranked very slow again. The idle was rough and it ran rich. The lifters were making noise but not excessive.

I got on the Inet and read some of the posts relating to preload and push rod lengths. My heads were milled so I made an adjustable push rod and messured it at 0 lash. It was .080 shorter than stock (8.693). If I add the .035 for the preload, my rods are only .045 short (I will need 8.650 rods). Is this right and worth the cost of custom push rods? It doesn't seem like that small amount would make a big diff..

Mick

 

[cruzn57]

slow cranking

I'm not sure on the push rod length, but the slow cranking sounds like insufficiant ground, check your ground cable, and any other ground wires that attach to the head, and block.
Also check started draw, (excess amp draw)
I'll be interested to see what tha response is on push rod length!
good luck
cruzn57

 

[qwknuf6 jr]

Originally posted by Micks87
I just got my TR back together after a blown head gasket. With a fully charged battery, I fired it up and it cranked real slow and seemed as though something was too tight. I let it run for 30 mins. I restarted it the next day and it cranked very slow again. The idle was rough and it ran rich. The lifters were making noise but not excessive.

I got on the Inet and read some of the posts relating to preload and push rod lengths. My heads were milled so I made an adjustable push rod and messured it at 0 lash. It was .080 shorter than stock (8.693). If I add the .035 for the preload, my rods are only .045 short (I will need 8.650 rods). Is this right and worth the cost of custom push rods? It doesn't seem like that small amount would make a big diff..

Mick

If I understand ,your stock pushrods will have .080 preload ,
most hyd lifters call for .020 to .060 preload .
I think it would be ok @.080 but you can shim the rocker shaft .050 to give you about .030 preload

 

[Micks87]

Shim with what? I spoke with a machine shop and several parts stores and they don't know of shims for the 3.8. I remember seeing someone who had used shims for a Ford motor but not sure which motor.

 

[blackbuick87]

What is the proper method to measure preload?

I just torqued mine to 25ft lbs and everything seemed fine

 

[MSDGN]

I wouldn't go .080 for preload...should be .030-035...get some custom pushrods the correct size or adjustable pushrods...

 

[qwknuf6 jr]

Originally posted by Micks87
Shim with what? I spoke with a machine shop and several parts stores and they don't know of shims for the 3.8. I remember seeing someone who had used shims for a Ford motor but not sure which motor.

Get some shim stock , mach shop should have some , will have to drill hole for rocker shaft bolt ,goes inbetween the shaft and the mounting pedestal.

 

[qwknuf6 jr]

Originally posted by blackbuick87
What is the proper method to measure preload?

I just torqued mine to 25ft lbs and everything seemed fine

Comp cams has a adj pushrod to measure pushrod legnth , rotate cam to lobe to base and install pushrod and rocker armshaft ,carefully adj the pushrod until all there is no slack in between the rocker and the pushrod , no further .
You will need to remove pushrod and carefully measure ,add preload to pushrod length ...i.e. 8.500 measure pusrod add .030 for preload =8.530 is the pushrod length you need .

Some examples of changing pushrod length are milled heads and block , diff headgaskets ,stock is .060 and felpro is .039,it can all add up ,some cams have different diam. cam bases not sure why .

preload needs to be checked

 

[Scott231]

I posted a procedure article for shimming the shaft bar a long time ago on the www.gnttype.org website in the Technical area. Do a search there for details.

 

[REDS HOT AIR]

I'm running mine very preloaded on sealed power lifters.

stock 87 pushrods with single steel shim head gasket that is a lil over .060 thinner than 86-87 head gasket and I have no problems with it.


do not do that with comp cams lifters..the less preload on them the better ..they will pump up and hold the valves open with higher rpm

 

[6SENSE]

Other than "chatter" is there any other problem that can be caused by not having enough pre-load?

 

[REDS HOT AIR]

if they have little to no preload its possible for them to blow the retainer clip out the top and the lifter come apart

 

[6SENSE]

That dont sound good.
Dont think my problem is that out of hand (I hope), havent even had any false knock over the last 100 miles or so

 

[Quickturbosix]

Lifter preload can effect your power curve. Even something as small as .005 can change it. I think it was on gnttype I read it.

I'am amung the few that use adjustables.

Shim the rocker shaft .035...

Adjust for zero....

Take out the shims...

Reinstall the shafts and your done...

Some say install the adjustables with the threaded end down to keep the threads oiled. But you have to jerk the intake off to to adjust them next time. Mine runs super quite using this method.

 

[GNX423]

After i got my motor back together the last time (cam swap) I had a slow cranking problem. My cam sensor was slightly out of proper position and would crank slowly than it would start up with a roar. Try holding the pedal all the way to the floor (turns off the injectors) and see how it cranks. Just a suggestion

Good luck,
Mike

 

[Micks87]

Try holding the pedal all the way to the floor (turns off the injectors) and see how it cranks. Just a suggestion

Good idea. I'll try that with my new push rods I ordered yesterday. I got some from cv products (8.650"). They are about 1 millimeter shorter than stock. I'm thinking I should have went with the adjustables now. Oh well, we'll see how they work out.

Thanks,
Mick