5.0_GT

ok i bought these rockers for my 88 gt, and i bolt them up and there lose ,makes the mustang sound like a diesel , seems like i need longer pushrods, has any body run these rockers? any advice.

Grimace5.0

http://www.cranecams.com/?show=faq&id=3

Lifters (Hydraulic)

Hydraulic lifters have been the choice of the automotive industry for many years for several good reasons. when compared to a mechanical lifter, the hydraulics are:

1. Quieter.
2. Low maintenance.
3. An ability to adjust for thermal expansion of the engine.
4. Built in shock absorber, eases stress on valve train.
5. ?Bleed Rate? can be designed to accommodate different engine RPM ranges.

Today?s modern engines all use either the standard design hydraulic lifter or the new low friction, high performance hydraulic roller design. Hydraulic lifters are the best for street applications, high performance, and mild racing applications where low maintenance is a primary concern.

What is the difference in the design of a Hydraulic and Mechanical Lifter?
Basically, the hydraulic lifter pushrod seat is moveable, the mechanical lifter seat is not. Both lifter types look the same from the outside, with both having pushrod seats held in by a retaining lock. The pushrod seat in a mechanical lifter usually registers upon an internal step inside the lifter body preventing it from moving (thus it gets the nickname ?Solid Lifter?). What?s below the pushrod seat in the hydraulic lifter is a different story. Its pushrod seat is not restricted by a step, but instead sits on top of a moveable hydraulic mechanism which acts like a tiny hydraulic pump. Below this mechanism is valving and a spring to produce an upward force, moving the pushrod seat upward against the retaining lock.

What is Hydraulic Lifter Preload?
Mechanical cam designs require a running clearance or valve lash; hydraulic lifters are just the opposite. When the rocker arm assembly is properly torqued down into position, the pushrod must take up all the clearance and descend into the hydraulic lifter, causing the pushrod seat to move down by .020? to .060?. The distance that the pushrod seat moves down away from the retaining lock is the ?Lifter Preload?. The hydraulic mechanism requires this precise amount of ?preload? for it to do its job properly.

What happens if the amount of Hydraulic Lifter Preload is wrong?
If clearance exists between the pushrod and the seat in the hydraulic lifter, after the rocker arm assembly has been torqued down, you will have no lifter preload. In this case the valve train will be noisy when the engine is running. All of the hydraulic force produced by the lifter will be exerted against the lifter?s retaining lock, and this could cause the lock to fail.
If the opposite occurs and the pushrod descends too far (more than .060?), then you have excessive lifter preload. In theory, a hydraulic lifter can pump up whatever preload you put into it, therefore with excessive preload, as the engine RPM and oil pressure increases, the hydraulic mechanism will pump-up the pushrod seat. This will cause the valve to be open longer and lift higher. This will decrease the cylinder pressure, lowering the performance of the engine. If the preload is excessive it may cause ?backfiring? from the engine. How to correct this situation will be explained in the next sections.


When rebuilding an engine, what can cause Lifter Preload to change?
Almost anything can affect lifter preload. If you do a valve job, surface the block or heads, change the head gasket thickness, or buy a new camshaft, the amount of preload can be affected. Sometimes these changes cancel one another out and your preload stays the same; this is more by luck than design. This is why you must always inspect the amount of preload the lifter has when reassembling the engine and be sure it is correct.

Fast and Easy Way to Check Hydraulic Lifter Preload when using Non-Adjustable Rocker Arms
With the cam, hydraulic lifters and pushrods in place, install your rocker arm assembly. Use the prescribed method in your repair manual and torque down all the valve train bolts in the proper sequence. Pick a cylinder that you are going to check. Hand rotate the engine in its normal direction of rotation until both valves are closed. You are on the compression cycle for that cylinder. (At this position the valve springs are at their least amount of tension making the job a little easier to do.)

Wait a few minutes, allowing the lifters to bleed down. Now, lay a rigid straightedge across the cylinder head, supporting it on the surface of the head where the valve cover gasket would go. Using a metal scribe and the straightedge, carefully scribe a line on both pushrods. Now carefully remove the torque from all valve train bolts, removing any pressure from the pushrods. Wait a few minutes for the pushrod seat in the hydraulic lifter to move back to the neutral position. Carefully scribe a new line on both pushrods.

Measure the distance between the two scribe marks, it represents the amount of lifter preload. If the lines are .020? to .060? apart you have proper lifter preload. If the lines are the same or less than .020? apart you have no or insufficient preload. If the lines are further apart than 060? you have excessive lifter preload. To bring your preload into tolerance, use one of the methods described in the next section if necessary, or call the Crane Tech Line for assistance (386/258-6174).

Methods to Adjust for Proper Hydraulic Lifter Preload There are several different methods for increasing or decreasing the amount of lifter preload, depending on valve train design and how the rocker arm is held onto the cylinder head. Keep in mind that the automotive manufacturers have made changes to the valve train over the years. What may work on one year?s engine may not work for another, even though they are basically the same engine. There is one method that universally works on all these engines, change the pushrod length! Use a longer pushrod to increase preload, a shorter to reduce preload. Crane offers various length pushrods and offers custom length pushrods also.

Using Adjustable Rocker Arms to set Hydraulic Lifter Preload The easiest method to arrive at proper lifter preload is when you have an engine with ?Adjustable Valve Train?. Unfortunately, since 1967 most domestic engines, with the exception of small and big block Chevrolets, have been made with non-adjustable rocker arms. The Crane Catalog shows you several ways of converting your engine to an adjustable rocker arm system. The following sections will describe how to set the preload with adjustable rocker arms.

Hydraulic Lifters Can Be Adjusted at Any Engine Temperature
Since hydraulic lifters can compensate for thermal expansion of the engine, the adjusting can be done with the engine cold; hot adjustment is not necessary.

[b]Adjusting Hydraulic Lifters for Proper Preload In order to adjust the preload the lifter must be properly located on the base circle or ?Heel? of the lobe. At this position the valve is closed and there is no lift taking place. You will need to watch the movement of the valves to determine which lifter is properly positioned for adjusting.

1. Remove the valve covers, and pick a cylinder you are going to set the preload on.

2. Hand rotate the engine in its normal direction of rotation and watch the exhaust valve on that particular cylinder. When the exhaust valve begins to open, stop and adjust that cylinder?s intake rocker arm. (Why? Because when the exhaust valve is just beginning to open, the intake lifter will be on the base circle of the lobe, the correct position for adjusting the intake.)

3. Back off the intake rocker arm adjuster and remove any tension from the pushrod. Wait a minute or two for that hydraulic lifter to return to a neutral position. The spring inside the lifter will move the pushrod seat up against the retaining lock if you give it time to do so. (If you are installing brand new lifters th

5.0_GT

ok...............[&:]

2 kwik

way more than was needed

Grimace5.0

But, complete and accurate.

2 kwik

by the time I read it I did a setj/k

90lxrider

yo my man im running them.....u need longer pushrods....i have all stock heads and lower end... i had to buy 6.350" push rods and they worked perfectly

88stangaruu

Try adjusting them with the engine running <-----Easiest way....if you have an old valve cover, just take a dremel and cut the top out of it and bolt it on the head and crank the car up. Then just tighten them till they stop making noise then go another 1/4 turn and lock em down.

tuff5liter

Grimace is great about doing that. He will answer your question and anything else you might wonder about later on. Just add all his posts to your favorites and you shouldnt ever have any problems on here.