Finding TDC on a flathead motor

[Bayless]

It's a long story why my '48 Prefect sidevalve has only one side of the timing mark and how I got myself into this situation. My problem is now timing a motor without a proper timing mark. More specifically, if I can find TDC then I can fabricate the other half of the timing mark and future timing will then be easy.

Thanks for any help short of remove the head. Ok, if remove the head is all you can offer then go ahead and say it.
Bayless

 

[DrEntropy]

The valves have side covers?

 

[DART]

I have no experience in this, but my thought would be to pull the plug, drop in a straw and turn the engine by hand watching when straw rises the furthest. Wouldn't that be TDC, or 2 strokes off?

 

[tony barnhill]

Dale - it would either be TDC on compression or the exact opposite...Doc's onto something....when #1 is at the top of its apex, the valves should be set for the compression stroke for it to be in time...I've neer seen a flathead that didn't have access to the valves from the side....that's the place to start, IMHO.

 

[DrEntropy]

One step at a time here... I'm kinda thinking it has covers on the side of the block...two in this case to allow access to valve gear.

 

[DART]

Doc's post came in while I was typing mine...and you both know much more about wrenchin than I ever will.

 

[DrEntropy]

The straw will play its part, Dale. I prefer a chopstick... First we need to know if the valve timing can be determined visually on one of the two possible TDC positions.

 

[bcliff]

Don't know much about the "later" cars (mine is a 34 Model Y), but I know some had a timing pin in the front cover. Unscrew it, turn it around and put it back in. Push in lightly while turning the engine over SLOWLY. there is an indent in the cam gear that the pin will dip into at TDC. Same as on a Model A Ford. And no I'm not all that old, I just know old stuff.
Bruce

 

[DrEntropy]

I'm concerned there've been too many "cooks" in there before us, Bruce. If there are covers onna valves it can be determined empirically which TDC is the firing position.

 

[Bayless]

Bruce you would have been right had I not made some changes. The original '48 motor had the timing pin you described. It was really shot before I got the car. I converted a '58 motor by using the front cover from the '48 to use the original motor mounts. The '58 had entirely different mounts. The '58 cover had an external timing mark to align with a mark on the pulley and does not have the dimple in the timing gear. That was my big mistake, not marking where that mark belongs. The first attachment below shows that plug just above the motor mount (long black bar) and near the fan belt.

There is a valve cover on the side Doc. You can see it in the second attachment and get an idea of the difficulty of getting to it. Maybe you and Tony have some magic there that I don't know but if all we want it for is to determine whether valves are open or closed then I can do that with the old finger in the spark plug hole trick. Also the plugs sit well back in the squish area between the valves, a good way from the piston. In fact, it might even be possible to see the valve heads through the plug hole. You can see the spark plug placement in the third attachment. I can't think of anything else that might help but I am open to any suggestions anyone may have.

Thanks,
Bayless

 

[DrEntropy]

The "finger in th' plug'ole" will get you close, a chopstick or other dowel and slow rotation by hand can put you near enough TDC to establish a way to index it. If you just need TDC, it won't matter which stroke it's on. I was under the impression you needed to find #1 TDC *firing* for dizzy indexing.

/bcforum/images/%%GRAEMLIN_URL%%/blush.gif My bad!

sorry!

 

[Bayless]

Oops, sorry for not being clear. I have the dizzy indexed and the engine runs. In fact it seems to be timed pretty well now. It was all done by trial & error though. Get it close enough to start then test drive, top gear a fairly low rpm and accelerate fairly hard. Advance until it pings then back off util it stops. Actually that's what the owner's manual recommends. Well, start with the timing pin instead of my "best guess" starting point. I would really like to get a set of external marks to give me a better reference.

 

[tony barnhill]

I'm like Doc - I thought you wanted to get it exactly on TDC - compression stroke - to check the valves & to make sure the distributor is timed correctly so you could carve a TDC mark on it.

 

[Bayless]

No, again, I apologize for not making it clear the first time. I'd just like to make a permanent finger for the front cover to line up with the mark on the pulley at TDC. Hoped someone might know of some magic trick or something that I hadn't heard of or thought of. If not, I'll probably have the head of again someday. Of course, I'll probably forget to mark TDC then too.

 

[Dave Russell]

If not, I'll probably have the head of again someday. Of course, I'll probably forget to mark TDC then too.

This would be the only totally reliable & accurate way to find TDC. Due to the offset between plug hole & cylinder, as you know, a chopstick down the plug hole would have to be at an extreme angle to reach the piston & would likely just get broken off as the piston rises. Just don't forget to mark things next time. Shades of Ford flat heads. At least you don't have to mess with the valve gear to remove the head.
D

 

[DrEntropy]

Geez Dave... I ain't suggesting he cram a chopstick in the hole at BDC and crank away!! /bcforum/images/%%GRAEMLIN_URL%%/jester.gif

Rather that he get close with the finger-in-the-dike check, and hand turn it with the stick in there when it's close to TDC... Prudently drawing it out incrementally when it begins to 'pinch' as the piston is SLOWLY coming to 'apogee' would be a given....


I ain't th' "Here, hold my beer... watch THIS!!" *CRUNCH!* type.

Figger'd he'd got it this far, he'd be aware it takes finesse. /bcforum/images/%%GRAEMLIN_URL%%/laugh.gif

 

[Dave Russell]

I didn't think that you were the crunch type. It's just that on many flat head engines there is only about .080" clearance between the head & the block "bridge" between valves & cylinder. Not much room & kind of an extreme angle to tell tdc very accurately.
D