I am in the process of rebuilding my 3.8 engine and ran into a push rod problem. It seems that between decking the block, installing a new cam, and installing new lifters the stock pushrods (8.686 inches) are too long by alot (maybe .070). I did some research and found that Comp Cams makes a pushrod for a Ford 460 that is .060 over the stock Ford 460 length (8.616 inches). They are part number 7844. They are 5/16's in diameter and have H-H ends. I used them and they fit perfect. Hopefully somebody else can use this info instead of shimming the rocker shaft. It only cost me $20 for 12 plus shipping. Thanks!
I had a valve job done on a pair of TR heads, which inluded milling the gasket surface for straightness. The car runs fine but would it be good to get a set of different lenght pushrods to compensate for the material removed during milling?
You would only have to get a new set of push rods if the lifter preload becomes too high.
Don't want to sound too ignorant, but how do you know if the preload is too high?
Does this mean that it compresses the valve spring when it's not suppose too? Would checking the compression tell you if you had too much preload (i.e. to low of a pressure)?
I'm fooling around with slightly longer than stock pushrods (.030") and I notice that the rocker arms are definitely "tighter" but I didn't see any compression of the springs.
Thanks,\Carl
Hi Carl! I would not mess with longer pushrods. This is how you check preload.... First bleed down the lifters. They fill with oil when the engine runs. If you dont have a bleeding tool you can still bleed down the lifter. Just cut an old pushrod. You need about 2-3" of pushrod. Put the lifter in a vice (make sure you back up the lifter with a piece of wood so the lifter does not get nicked up). The base of the lifter is against the wood. Place the cut pushrod into the top (plunger) of the lifter. Compress the vice a little at a time. You will see the oil bleed out.
Now that the lifter is bled you can check preload. Place the lifters back in the engine. MARK WHICH LIFTERS GO WHERE!!! VERY IMPORTANT!! Place the rest of the valve train back in. You have to check each valve when the valve is totally closed (lifer on the base circle of the cam and not on the lobe). Now check how much the pushrod depresses the plunger off of its base (the retainer clip). It should only depress the plunger very little around .030 inches.
You dont want the preload to be too high. That would cause low vacuum and will burn a valve seat.
If you need more help email me Antjohn7@optonline.net