Sunday, September 16, 2012

Approaching the final assembly of the engine we had to address "lifter preload" only to find no real accurate way to measure it. Some builders use an indicator off the rockers while others scribe lines on the push rods then measure with a dial calipers. We ended up making up a simple tool to clip directly unto the push rod and then position a dial indicator off the tool. I made this from a spring style paper clip available at any office supply store and bent some brass shim stock then crimped it onto the paper clip. First the new Lunati 64501 cam was lubed up and installed. This cam was picked over the stock 401 and Edelbrock cam for it's slightly higher rpm range of 1200-5500,
Advertised Duration (Int/Exh): 256/262, Duration @ .050 (Int/Exh): 213/220, Gross Valve Lift (Int/Exh): .484/.507, LSA/ICL: 112/108, Valve Lash (Int/Exh): Hyd/Hyd. A new Comp Cams 3118 timing set was then slid on. Finally new Lunati hydraulic lifters 71977PR were dropped in along with the push rods and then the rockers.
Since we had cut the valve seats earlier and not the valve stem length, this through our preload measurement out. The preload ended up being too light. Now we could have went with longer push rods, and then a shim kit for under the rocker bridges, but being on a tight (cheap) budget we decided if a shim could be added to lighten up the preload why can't material be milled off the rocker bridges to make it heavier? Preload was measured then a formula was trigged out to determine how much to mill off the bottom of the bridge. A fixture was made up to hold the bridge in a milling vise and each side was cut separately from each other determined by the formula. The one drawback to this, is that the bridges must be kept at their position and not mixed up.  In the future if any valve work is done the correct way then new bridges will be needed. Next time we will address the timing cover.


Anonymous Anonymous said...

I don't understand half of what I just read, but I'm glad to see you're still posting!

5:47 AM  

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