Timing frustrations

[Big Red Mach 1]

Well the intake is back on with the turkey pan installed. That thing was interesting. I can see why some prefer intakes that don't need it. I think I should have dry fit the pan into place long before I had everything beaded with the gasket maker because they sure as hell don't fit well right out of the box. If I ever do this again, I'll fit it and bend it to shape well before I'm ready to install. I torqued it down 10,15,20. Then waited about a half hour and did another pass at 20, and it needed it as everything settled into place. I'll let it cure overnight, then hit it at 20 one more time. Hoping it's a good seal everywhere.

Tomorrow's agenda;

Valve Covers - Bend the baffles to not hit the rockers like they were.

Cylinder inspections with scope.

Compression test

New Plugs. Autolite 25's

Cap, rotor wires back on.

Wiring harness back on and hooked up

Carb hooked up.- I'll run the mixture screws in and back them out 1.5 turns for a starting point.

All vac ports plugged.

Set timing and check vacuum at idle. We'll see what we get.

 

[Big Red Mach 1]

Bit of a progress report.

Dry cylinder test shows

1-200

2-210

3-210

4-200

5-205

6-205

7-185

8-190

I obviously don't love 7 or 8. Visual inspection of them reveals absolutely nothing out of the ordinary. Pistons look great. cylinder walls look great, all spark plugs look the same. I don't have overheating issues, or any oil/coolant mixing issues. Two lower numbers right next to each other has always said head gasket to me, but I'm just not seeing it.

Again, this was a dry test. And probably too dry. I know that at times I was running so rich I had to be washing down the cylinder walls. And since I haven't given this a chance to really run yet, I'm definitely not flowing oil like I would be running. I'm going to wet 7 and 8 with some oil and see what I come up with. As always, stay tuned...

 

[Don C]

The spreadsheet in this thread will help you get a handle on the variances

https://www.7173mustangs.com/thread-compression-altitude-calculations?pid=115411#pid115411

 

[Big Red Mach 1]

Thank you Don. Here are my results. I feel like I should have just waited to do the compression test until after I got her running and dialed in as best I could. Doing a cold and dry test might not have been the best idea. I did add about a teaspoon of oil. the 185 came up to 190. The 190 cylinder did not move. I really think those cylinders are not at all lubricated.

 

[Stanglover]

Well, obviously that "ding" in the #1 piston didn't hurt it too much!

 

[Don C]

At least with #7 coming up to 190 they are all within 10% now.

 

[Big Red Mach 1]

Well, obviously that "ding" in the #1 piston didn't hurt it too much!

For sure. At this point I've fully bought into the idea that it probably was a piston stop accident, and that it's more than likely been there a loooong time without incident. You can even see the small divot from what may have been the tip, and the wider impact behind that may have been the threads. Not that this was certainly the exact tool used, but you get the idea. #1 only, and inline with the plug hole just makes sense. 

He should have borrowed your #2 pencil. 

 

[Big Red Mach 1]

At least with #7 coming up to 190 they are all within 10% now.

I love that glass half full attitude!!! Need more of that these days. :wrench:

 

[tony-muscle]

Well, obviously that "ding" in the #1 piston didn't hurt it too much!

For sure. At this point I've fully bought into the idea that it probably was a piston stop accident, and that it's more than likely been there a loooong time without incident. You can even see the small divot from what may have been the tip, and the wider impact behind that may have been the threads. Not that this was certainly the exact tool used, but you get the idea. #1 only, and inline with the plug hole just makes sense. 

He should have borrowed your #2 pencil. 

I don't think it would have made it all the way up to the threads. The impact would have been on the tip alone. At that point either the crank stopped, or the piston stop broke. Probably the former.

My real time job is failure analysis. So after you have a hypothesis that passes all the tests then you build a model to test it. So, who is willing to sacrifice their engine so we can test this theory? 

 

[Stanglover]

Well, obviously that "ding" in the #1 piston didn't hurt it too much!

For sure. At this point I've fully bought into the idea that it probably was a piston stop accident, and that it's more than likely been there a loooong time without incident. You can even see the small divot from what may have been the tip, and the wider impact behind that may have been the threads. Not that this was certainly the exact tool used, but you get the idea. #1 only, and inline with the plug hole just makes sense. 

He should have borrowed your #2 pencil. 

Ah, so that's what a piston stop tool looks like eh! I think I'll stay with my #2 pencil with a rubber. (not a condom)

I have to agree with Tony Muscle, if the red arrow, threads, made it into the piston, there would be a hole right through it, not just a divot.

 

[Don C]

Except they don't all look like that. Here's what one from one of our favorite (not) companies, Proform, looks like

 

[cv_72mustang]

Hi, Love this tread. Well done and great tenacity in finding solutions. It's been a very long time since I looked for TDC. But I think last time I was about 20 and used my pinky finger.

 

[Stanglover]

Except they don't all look like that. Here's what one from one of our favorite (not) companies, Proform, looks like

 Similar but different. For someone who actually has not seen one or even knew they existed, I'm kind of surprised they have a threaded center piece. If that were to set too low, there's Big Red's divot. My logical brain tells me it ought to be a spring loaded sliding center piece with some sort of marking on it so, like my pencil, one can see or feel as the piston reaches TDC. Maybe I've got it all wrong, but that's the way I think it ought to be. However I realize the travel is not directly up and down with it screwed into the plug hole. Perhaps it ought to be more like a mini dial test indicator with a little finger that transfers to a dial. OK, now I'm getting way too elaborate!

 

[Don C]

The way they work is that you run them down deep enough to stop the #1 piston 15 or 20° before TDC, and mark the harmonic balancer at the timing pointer. Then you rotate it in the opposite direction until it stops again, mark it, TDC for #1 is halfway between the two marks. Trying to determine an accurate TDC by feel when the piston is at the top of it's stroke is nearly impossible because as the piston nears the top the crankshaft revolution it makes a smaller and smaller movement of the piston as it nears the top. Even if you used a dial indicator it would be challenging, due to the tiny bit of slack in the bearings as the crankshaft peaks and starts down. The piston stop eliminates any slack.

Edit: And that's why you have to remember it's in the spark plug hole before you try to crank it with the starter.

 

[Stanglover]

The way they work is that you run them down deep enough to stop the #1 piston 15 or 20° before TDC, and mark the harmonic balancer at the timing pointer. Then you rotate it in the opposite direction until it stops again, mark it, TDC for #1 is halfway between the two marks. Trying to determine an accurate TDC by  feel when the piston is at the top of it's stroke is nearly impossible because as the piston nears the top the crankshaft revolution it makes a smaller and smaller movement of the piston as it nears the top. Even if you used a dial indicator it would be challenging, due to the tiny bit of slack in the bearings as the crankshaft peaks and starts down. The piston stop eliminates any slack.

Edit: And that's why you have to remember it's in the spark plug hole before you try to crank it with the starter.

 Thank you Don, As my signature says, "I learn something new every day" and today, I did.

 However, does TDC need to be that precise, I mean if it is a 1/2 degree either way, the difference in feeling TDC with piston coming up or just starting to go down really going to make that much difference to the total timing. I can't read my marking on the harmonic balancer and pointer that accurately with the motor running at 3000rpm. If it were a race engine, then perhaps I can see that need, but for a classic driven on sunny Sundays ?

 

[Don C]

It'll likely be more like 2 to 4° off. Plus, you'll use that TDC mark to make sure the timing pointer is correct. I guess I'm too much of a perfectionist, errors are generally accumulative, I'm a terribly slow wood worker, engineers make terrible carpenters My wife's Dad was a carpenter/homebuilder, and over the years I've frequently heard her comment on how long it takes me to build something out of wood. To her Dad 1/4" was close enough, to me 1/32" isn't really close enough, but I make do with it. You've heard "measure twice, cut once", for something critical it's more like measure 3 or 4 times, write it down, draw up a sketch, and then cut it .

 

[Stanglover]

It'll likely be more like 2 to 4° off. Plus, you'll use that TDC mark to make sure the timing pointer is correct. I guess I'm too much of a perfectionist, errors are generally accumulative, I'm  a terribly slow wood worker, engineers make terrible carpenters My wife's Dad was a carpenter/homebuilder, and over the years I've frequently heard her comment on how long it takes me to build something out of wood. To her Dad 1/4" was close enough, to me 1/32" isn't really close enough, but I make do with it. You've heard "measure twice, cut once", for something critical it's more like measure 3 or 4 times, write it down, draw up a sketch, and then cut it .

 Not to prolong this extended discussion, but as a (former) machinist, I'm used to working to 1/10000", so I do agree, the closer the tolerance the better it will be and that goes for (almost) everything.

 

[Big Red Mach 1]

Hi, Love this tread.  Well done and great tenacity in finding solutions.  It's been a very long time since I looked for TDC.  But I think last time I was about 20 and used my pinky finger.

Glad it's keeping everyone entertained. At least giving us something to do during this down time with the virus. 

She's all put back together with exception of the fan. Waiting on it to get here. Clutch came fast, fan itself, not so much. Comes tomorrow I believe. I'm not giving UPS a hard time during these times, that's for sure. Just glad we can even still get parts delivered. 

I'm sure I could fire it up for a few, and see what the initial vacuum looks like, but I don't really want to until I can take my time, adjust the timing, dial in the carb, idle speed, etc. without worrying about overheating. I'd like to let her run for a good little while assuming all is well. 

Get those last minute Hg guesses in. 

 

[Stanglover]

Hi, Love this tread.  Well done and great tenacity in finding solutions.  It's been a very long time since I looked for TDC.  But I think last time I was about 20 and used my pinky finger.

Glad it's keeping everyone entertained. At least giving us something to do during this down time with the virus. 

She's all put back together with exception of the fan. Waiting on it to get here. Clutch came fast, fan itself, not so much. Comes tomorrow I believe. I'm not giving UPS a hard time during these times, that's for sure. Just glad we can even still get parts delivered. 

I'm sure I could fire it up for a few, and see what the initial vacuum looks like, but I don't really want to until I can take my time, adjust the timing, dial in the carb, idle speed, etc. without worrying about overheating. I'd like to let her run for a good little while assuming all is well. 

Get those last minute Hg guesses in. 

Without know the cam spec, I'm going with 15" Hg. Stock cam would be around 17" Hg.

Geoff.

 

[Don C]

The idle spec is 13 inches, so I'm going with 12 inches at idle.