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Post by ricky8664 on Apr 23, 2023 13:50:15 GMT
Now the engine is running I'm going to replace the standard heads with SD1 versions, which I will have overhauled b4 fitting. I'm intending to fit new rocker shafts, rocker arms and pushrods with new hydraulic tappets.
As I will be fitting these to the existing cam (assuming there is no excessive wear visible when the heads are off) does anyone have any thoughts on whether I need to do a check/adjustment of the camshaft/tappet preload? The heads will probably be skimmed which will raise the CR but fitted with composite gaskets, which will lower it. And obviously, they will not be the original heads. Or is preload adjustment only needed with a new cam?
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Post by harvey on Apr 23, 2023 14:17:59 GMT
Preload only needs to be checked if you alter things from standard. If everything is as standard there's no need to bother. If the heads have been skimmed, but replaced with composite gaskets you should have no problems.
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Post by enigmas on Apr 23, 2023 23:19:33 GMT
Sure you can do what Harvey suggests and it all may be fine, but what if it's not? Since you're refurbishing the top end of the engine and have it apart, why wouldn't you check the preload? It's a simple, straight forward process easily carried out with a piece of thin wire. It's also good engineering practise that doesn't rely on assuming tolerances are correct or wishful thinking.  |
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Post by harvey on Apr 24, 2023 18:38:15 GMT
That bloke at the factory checking the preload on every engine must have slowed up production considerably.
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Post by enigmas on Apr 24, 2023 22:17:06 GMT
Why wouldn't you do it Harvey? There's no references being made to factory assembly production methods nor any of the quality control checks during manufacture. It's a mass produced engine with a broad range of production tolerances. Some engines would run better than others. It's a rhetorical question, but why? Because of production variations and build quality. Any added machining changes tolerances so why not check them as the engine is being assembled, in this case an old engine that's had a life and is being rebuilt. Simple things such as variations in valve stem heights, valve face resurfacing and valve seats cut too deep can affect lifter preload. Hey, we've not even mentioned worn camshaft bearings and slack timing chains? Why bother with an engine rebuild if you're going to half ass the assembly for the sake of a few simple checks.
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