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MG MGB GT V8 Factory Originals Technical - hydraulic tappets
|im ready to torque the heads on today but am curious about two thing. first, should i soak the tappets in some kind of oil or fit them dry? second, what is the recommended preload on the rover engines, and how should i check it? ive heard to use different gauge wire as well as making marks on the pushrod before and after theyre installed. any suggestions?|
|My machine shop recommended that the tappets not be filled with oil and that you run a slight risk of doing some damage if they are pumped up at the first start, He did recommend that the the engine be prelubed by turning the oil pump with a drill.|
It was also suggested that some GM assembly lube be poured over the cam before the galley is sealed up before the first start.
RPI has a section on lifter preload for the Rover engines, and I think it is 040 to .060, but you should check their site. TA performance, a Buick specialist here in Phoenix say you can go up to 065.
You can check preload with a wire type spark plug gauge (not the type with the "U" the type with the "L").
Alternatly, you can assemble the rocker tower with the pushrods installed. On a lifter with the tappet riding on the base circle of the cam, count how many turns of the bolt it takes from the time you meet resistance of the tappet's spring till the tower is tight. The thread pitch should give about 0.066 in per turn, but you'll have to correct this by the rocker ration to get the preload right. I shimmed mine to get about 3/8 of a turn on the bolt, which I figured was about .045 preload. You'll need to do this at both ends of the rocker shaft on both heads then check the middle cylinders to make sure the preload is good there too. I used Melling pushrods and tappets and had the heads trued, and I had to add about .050 of shims under the rocker towers.
By the way does the 300 water pump clear your alt mount?
yeah it looks the same as a v6 water pump, with the outlet angled more down than the 215. i found a v6 pump at the parts yard today just to have a close look, and it should fit right on, with no clearance problems. ill check the preload tonite and let you know how its going. thanks for the help.
what did you use to shim your rocker pedestals?
|I used .025 aluminum shims made from some scrap sheet I had in the shop. I sheared them into squares about an eighth of an inch bigger than the pedestal, stacked them together and drilled them on a drill press. I make sure I had plenty of clearance for oil flow and carefully deburred them.|
I've read of having them ground, but that seemed like overkill to me.
|well, i picked up some cam grease (moly graphite) and lubed up the tappets and cam. i also got one of those "L" spark plug gauges and checked the preload. all of them wre between .043 and .046 so i think im fine. thanks for the help.|
This thread was discussed between 26/10/2002 and 03/11/2002
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