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Message: <blockquote data-quote="NXcoupe" data-source="post: 646476" data-attributes="member: 11751">No. just use the 1.7's on every valve. It's a great way to waste a whole pile of cash. You do have a camshaft in it, but not knowing the exact specs of it, just guessing what it is, isn't going to allow you to make decisions like that. I would leave as is, it is running well and should continue to do so if you keep things the same. So the engine must have been rebuilt? Well here's another one of my engine builder secrets I'll throw out here for you guys to chew on. I have all my machine work done by a one man shop, keeps my costs down because I don't have to buy over a 1/3 million dollars worth of machine equipment and he does it exactly as I want it done. Well, ran across a customer years and years ago that had this problem, engine sounded great, but after driving for a while, and getting hot, the oil pressure would drop drastically, and the lifters would all start ticking and rattling at idle and especially when you were cruising at 2k rpms. Well I started doing back investigation and after months of looking, I found out the guy who was going to 'build' this guys engine was an 'expert' and ran a brake cylinder hone in the lifter holes to 'clean them up'. Well, problem is, Ford insists on .0005 clearance on the lifter bores. If you run a hone in, even for a couple strokes, you will increase that to over .001. What's the problem? Well most chevy guys do this as a matter of course, well, Ford runs the oil to the lifters, then down to the mains from the cam oil journals. So, if you allow this pressure to bleed off around the lifters, then there is less pressure through the ENTIRE oiling system, get it? Like a hole in an inner tube, the whole system is only as pressurized as it's weakest part. He went with a new block and his troubles went away. I found out my machinist did this to one of my blocks, and I ended up throwing it away. He said the same thing, I do it to every engine I build (marked Chevrolet), I dissussed it with him and now he leaves the alone. this could be what's going on in your case. Check your oil pressure when hot with a manual gauge, shouldn't drop more than 20 psi from cold to hot. Hope this helps.</blockquote>