"If it ain't broke, don't fix it"
"If it ain't broke, fix it until it is"

Either of the above describes my situation. Rebuilt engine must, according to the cam supplier, be started up and immediately taken to 2500 RPM and held there several minutes. I foolishly started restoration on the working but dirty carbs (throttle shafts were very rattly)and I have the necessary parts and machine work in hand, and have read lots of tuning advice.

The question: with the jets centered and throttle shaft between the carbs connected, what should be the initial settings for the jets, the choke mechanism idle limit screws and the throttle butterfly limit screws, in order to start up and keep running? Not worried about running too rich for a few minutes; it's easy to change plugs and oil if necessary. Surely the factory must have faced this question several hundred thousand times, once for each car...Once I am running the rest of the tuning should be straightforward.

At least I didn't mess with the distributor, and don't plan to until later. It seemed to be OK when the car was running before The Great Teardown.

Any guidance, with occasional rude comments if appropriate, would be gratefully received!

Al

Standard 'base' tuning for a set of SU carbs is to screw the jet adjuster up until it (gently! as goes for all adjusters on any carb, obv.) it tops out on the carb body, then three full turns out.

Unless the carbs are wildly unsuited for the motor (totally wrong needles, improper fuel bowl level setting, etc), this should be good enough to make it run half decently. At least as good as it needs to be for cam break in.

The recommendation mostly has to do with the rather casual nature of the lubrication the cam lobes get in a B18/20 motor. There's no direct lubrication. There is some drip down from the lifters, but they aren't directly lubed either - they just get some of the oil that comes down from the pressure fed rocker shaft/rockers. Some of that oil goes down some dedicated drain holes, some drains on top of the lifters to lube them, a very small amount probably leaks past the lifters.

The main way they get lube, then, is by crankcase windage. The spinning crank with it's pressure fed bearings constantly spewing oil out (especially the rod bearings) makes quite an oily fog inside the block. The cam lobes are positioned fairly decently to get splattered by the rods. (Note that the lobes are not able to take advantage of any pre-start up lubing by spinning the oil pump)

It's still a somewhat indirect way to lube something, and that's a pretty stressed friction surface (especially if you have double valve springs and a big lumpy cam). One of the reasons lifters can be problematic in a OHV redblock motor. If you started the motor and let it idle calmly for a while, it's possible that the lobes wouldn't get adequately lubed, and gall slightly before they've developed that finely honed working relationship with the lifter.

You should use assembly lube on the lifters as well, sometimes the new cam will come with some special grease, if not you should use something similar - not a thick oil that will drain off before the thing gets completed and installed and started.

Also, modern oils have sharply reduced levels of zinc in them (more precisely, whatever chemical compound ZDDP actually is). Zinc is very good for sliding steel surfaces like a cam lobe/lifter. This is partly because modern engines have fewer such interfaces (more roller style lifters/cam followers), but mostly because catalytic converters don't like zinc from whatever oil gets into the exhaust. This obviously isn't an issue for (most) pushrod redblock cars. So either search out an oil with a higher ZDDP content, or add some ZDDP directly. Lucas makes a 'break in oil' which is a BUNCH of ZDDP in a bottle, on a brand new motor I'll put a whole bottle in for the first 1000 miles or so, then switch to something like 1/3rd a bottle in every oil change. I started doing this after having some repeated lifter issues in the PV's motor (big cams, double valve springs, plenty of revs used frequently).
--
'63 PV544 rat rod, '93 Classic #1141 245 (now w/16V turbo)

3 full turns out is 1 turn too many. 2 turns out equals 12 flats when turning the nuts. Counting the flats is the easiest way of keeping tabs on where you are. As you'll be starting from cold you'll start out using the choke but try and come off that as soon as you can, but keep the revs up to about 2-2500 for at least 20 minutes by using the carb throttle screws. The engine should speed up as it settles down and gets warm, just don't let it get going too fast. Fine if you have a rev counter but if not a dwell meter usually has one. Best to know what the revs are rather than guessing.