I'm trying to help a neighbor time an 8BA and I'm not familiar with them. Can someone tell an easy way to know the engine is at TDC? I read the manual about loosening the screw on the side and moving it to change timing. But without a timing mark on the balancer I'm having trouble. Thanks in advance.
You need the Mart-O-Matic Handy-Dandy Bent Wire Flathead TDC indicator wand. Two bits of bent 1/8" welding wire. The one piece (wrapped round the head nut) just acts as a guide for the other piece. That has a 90 deg bend, and about 2" beyond the bend. The bend allows the end to sit on the piston. As you go past TDC the wand rises and starts to fall. With a little To-ing and Fro-ing you can stop the motor with the wand at it's highest and that's a pretty good indication of tdc for getting a motor running. You want the piston to be on the compression stroke before putting the wire in the plug hole, so watch the exhaust valve through the plug hole, turn the crank till it closes, and then turn it one complete turn more. This should put that cylinder at roughly tdc on the compression stroke. Mart.
Thanks for the suggestions. How simple the water deal is, why didn't I think of it?? Mart, I'm ashamed to admit but I even tried a piece of punk but it bent and never had the TDC feel to it. I like your brazing rod idea, won't scratch or hurt anything in there. I will mark the crank for the next Schmoe that sets timing. You guys are the shit!
the only way to find TRUE top dead center is with a piston stop and a degree wheel, the piston stays at TDC for a few degrees so you have to turn the crank one way until the piston hits the piston stop, then the other, read the degree wheel in both places and split the difference. Do this until you get the same reading in both places, then zero will be TRUE TDC
Every 8BA I've had was equipped with a crank pulley that had a little dimple or pimple at the timing mark when aligned with the pointer that sticks out of the timing gear cover........I think when they are aligned the motor is at 2 degrees before TDC.......you can then adjust accordingly, but it will get your motor running....... My $.02 Brucie
5C, I understand what you are saying about TRUE TDC. I'm looking for a quick and dirty method to get it running. The neighbor is one of the 70 year old, look over your shoulder, "what are you doing now" neighbors. It ran before he "worked" on it. I'd just like to help him get it running. Thanks to everyone for the help.
On an 8BA, there is a timing mark at initial advance point, a dimple on pulley flange thaty aligns with a spike on front cover. Just plug vac line and set timing with a light at idle like a modernish car. Plenty good enough for a filling station tuneup. For serious work, interference method (which can be done on a flatty with heads on) is only way to do better than within 2-3 degrees of perfect TDC.
This is something I discovered for myself many years ago--and I couldn't believe what my eyes told me until I read the same thing from Smokey Yunick! I guess I'm insecure. At least engines with offsets and long rods like SBC's and Flatheads have what Yunick calls "dwell" at TDC, roughly 3 degrees of rotation in which vertical motion is either non-existent or imperceptible. My first serious measuring tool was a Wehrmacht surplus dial indicator I found in a junkshop in Stuttgart. When I rebuilt my '48, I decided to add a TDC mark, and hooked the thing up over the piston and hung a big borrowed degree wheel on the front. I happily and easily located TDC within point oh oh nothing of a gnat's eyelash, then decided to repeat the experiment while closely watching the wheel. TDC was nearly 3 degrees wide, and this severely traumatized my brain because I could not account for it until many years later I began to read Yunicks thoughts on rod length and the improvements possible through longer rods. I've never done anything with short rod engines (I SPIT upon your stupid little con rods!!) or with any engine lacking either piston or crank offset, but I understand that sometging like a 302 Ford with a minimalist rod has a sharper break between UP and DOWN. Get a big wheel and try it--you'll be amazed, it's so counterintuitive. On an OHV, you can usually stop the piston woth a simple boly through an old spark plug as the stop; With a flathead, piston is way out of line with hole, so a flex block is needed if head is on. Best is a tie-wrap with a largish plastic buckjle, pushed in and across til it hits the far wall and carefully held in place by a helper. On any engine with heads off, you just bolt a strap with a suitable stop bolt across the cylinder. Drill is to rotate engine by hand until it hits stop, mark pulley or degree wheel, rotate other way and mark again. It will take you about an extra 30 seconds to repeat a couple of times to be sure you bracket TDC at the same spot to be sure your stop did not shift if using the hand held way. True TDC is half way between stop points. Old way shown in 1950's cam manuals was to use dial indicator to place piston same short distance down hole on each side of TDC, but this seems harder to do and easier to screw up than a solid THUD against an immovable object.
Thanks Bruce. Like the cable tie idea. I had a thought about my moving wand idea. If you use the wand to locate rough tdc and put a mark (or a pointer - could be part of the bent wire guide) say an inch below the highest point and then allow it to fall an inch and a half or so (roughly 1/4" at the piston). By carefully turning the engine so it raises back up to align with the mark, and make a mark on the front pulley (in line with a fixed pointer) then rotate past tdc and past the pointer on the other side of tdc, then turn it backwards and carefully align with the mark again, mark the pulley again. Half way between the marks on the pulley will be about as accurate as you can get without pulling the head. The above might sound confusing, but anyone familiar with the technique I am trying to replicate will see what I am trying to describe. At the end of the day it's an old flatty, it will live with the timing somewhere near. Mart.
You are describing an nearly exact equivalent to the olde dial indicator way shown in ancient Isky books and described by the HRM gurus of the 1950's! Just find two points equidistant from top, so results if carefully done should be same as interference exactly. Interference just removes the need for care in keeping the moveable device the same at each attempt and reading marks carefully--the piston simply hits an immovable object each way and stops. Your way is purely mechanical, and of course needs a cleverly designed arm to go in there and repeat properly. I'm aware of one other way, shown in an old flyer for a Lisle tool co. device for timing flatheads: put in something that just GROUNDS against the piston, turning on a 6V test light at moment of contact!
Also, as you point out, factory marks are probably not really any closer than a visually determined TDC, AND your carefully determined timing point on a rod should just be where experimentation starts on finding where YOUR engine likes its timing set.
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