ORIGINAL: w8ye
ORIGINAL: mike early
I always assumed the dots were lined up with the crank pin and centerline of the cam shaft lobes. From what you are saying, the cam is meant to be advanced a bit. Perfectly understandable, I've degreed cams in my Small Block Ford many times. Even have a cam wheel and dial caliper, etc for this procedure.
You've mentioned this before. My apparently retarded (no pun!) situation yield a great idle, but gives up top end, I think you've said. I had forgotten that. But I don't think I've replaced any bearings since I read your post, and since forgotten. I am glad you reminded me. I got plenty of room on the idle to give away. It idles at 1500 with a 16x10x3blade. 2000 would be fine.
I didn't get a chance to pick up the bearings from the LHS today. I'll install them tomorrow night and take a photo of the crank-pin through the open back plate when both valves are open the exact same amount. I''ll shoot for 1 tooth BTDC.
Where did hear about the 5ยบ advanced? I guess if you are positive the dots are lined up, and that's what it turns out to be, it's self-evident. But I can never be sure where them damn dots end up after I've slid everything together.....
What we are shooting for is that the valve overlap interval is to cross over TDC on the overlap stroke. But if the cam is set with the dot at 6:00 and the crank pin is straight up then from my experience, the exact point where both valves are cracked open a slight amount (the same amount level across the rocker arms) is slightly before TDC and not exactly on TDC.
This over lap is the period where booth valves are open a little bit even though one may be open more than the other. This band actually covers some 25 degrees? It will vary by your valve clearance settings. You can see the range of it by blowing in the exhaust with the carb open and observing the air coming out the carb during the overlap period.
The Saito has more teeth on the cam gear than the Y-S, OS, Magnum, ASP, SC etc so one tooth off may be hard to figure out? On the other engines, you can pull the cam cover off and see where the cam is.
I had a ASP 120 that would only turn a 15 X 6 good. It was sick with a 15 X 8. I looked at the cam and it was one tooth advanced. I set the cam back one tooth and that engine screams with a 15 X 8. Saitos are not so drastic being 1 tooth off and will still run pretty good but they run best when set correctly.
The way the logic goes, if you are advanced one tooth, the idle is great but you loose the ability to swing an inch of prop.
If you are retarded one tooth, the top end is great but it will not idle worth a toot.