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Old 09-27-2020, 02:07 PM   #1
Russ/40
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Default Question on Cam Gear Marks - UPDATE

The current status of my miserable running V8.

I decided to start from scratch on this motor. I pulled every piston rod assembly, and inspected for any broken rings. No broken rings. I had a set, so I replaced them anyway.

I pulled all valve assemblies and replaced all valves and springs. This corrected the fact it did have the wrong springs, they were the 52/53 springs. I used flathead valves. I touched up all seats to correct any non-concentricity. An lastly replaced my lifters with adjustables, correcting any lash errors. Lash set to 12 intake and 14 exhaust.

After comparing the cam gear with another, matching bolt patterns and matching marks. I left the cam and crank gears in place. The cam itself has been run in another motor so I was convinced the cam itself is a good 77B.

I disassembled the distributor checking and resetting points to .015". Used new plugs.

The test run on the stand gave a very nice idle, and throttle response did not create any loud exhaust pops, ran a rebuilt 97 for carburetion that gave some adjustability at idle.

Net result I cannot get timing correct. With the distributor at typical settings HELMIT DISTRIBUTOR TYPE it idles slow at 25 degrees advance. When setting up a timeing marker, i used a dial indicator for TDC number one, and included a degree scale for testing.

Side distributor timing set for 1/2 increment advance, like every other flathead I've had which was correct. Net is again 25 degrees advance at idle. Vacuum brake is screwed all the way in, but will still advance to about 35 degrees with RPM.

What the heck am I missing here. It's hard to start and not running as it should.
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Old 09-27-2020, 02:38 PM   #2
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Default Re: Question on Cam Gear Marks - UPDATE

Congrats on fixing the mechanical problems, Russ. My money's on the shorter valve springs having been the trouble.
Now...is there any way this thing's trying to run on just the passenger side points? Like the driver side isn't making good contact or not closing for some reason?
If I'm thinking right, the pass side opens first, and then driver side later to fire the coil.


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Old 09-27-2020, 02:55 PM   #3
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Default Re: Question on Cam Gear Marks - UPDATE

Did you double check the TDC mark on the pulley when you had the engine apart?
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Old 09-27-2020, 05:03 PM   #4
Russ/40
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Default Re: Question on Cam Gear Marks - UPDATE

There was no TDC mark except the one I created with heads off and a dial indicator. This is a 41 block with the factory correct pulley and crank mounted fan. I did use an 8BA crank.

Terry, would that cause so much advance? I can check it. I even used a different distributor this time. There was too much advance on the other distributor before. I'll have to look up which set is responsible for timeing as well as dwell.

Last edited by Russ/40; 09-27-2020 at 05:10 PM.
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Old 09-27-2020, 07:39 PM   #5
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Default Re: Question on Cam Gear Marks - UPDATE

I believe LH set is timing of the spark. RH side provides longer dwell time. Since RH side opens earlier it seems (in my mind anyway ) that if the LH side were not making contact for any reason, then the RH side would be doing the switching of the coil and it would happen earlier.
Now, I have not studied enough to say how much earlier but it would sure be earlier.



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Old 09-27-2020, 07:45 PM   #6
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Default Re: Question on Cam Gear Marks - UPDATE

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There was no TDC mark except the one I created with heads off and a dial indicator. This is a 41 block with the factory correct pulley and crank mounted fan. I did use an 8BA crank.
Yes, I am well aware that there are no original timing marks, but you say you are checking the timing, so must be checking them against some added mark. The question was, was the added mark checked when you dissembled the engine this last time? It is easy to get the mark off using a dial indicator IMO. I would start by rechecking the mark. It about has to be mismarked or a distributor problem. Two distributors both having the points not functioning seems odd, but anything is possible.
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Old 09-27-2020, 11:46 PM   #7
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Default Re: Question on Cam Gear Marks - UPDATE

Yes, the timeing marks were developed before I put the heads back on. I first located the location I wanted my marks for easy viewing. I then found TDC using a dial indicator. I then made my pully notch where it could be seen. I then mounted my degree scale with ZERO as my TDC mark on the block, matching the pully. Photos attached, but the engine was not at TDC for the photo.
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Old 09-28-2020, 06:56 AM   #8
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Default Re: Question on Cam Gear Marks - UPDATE

So you found TDC turning motor both ways and using your math split in two for the dwell .
Great
You also dialed in the cam with your wheel checking timing .
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Old 09-28-2020, 09:53 AM   #9
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Default Re: Question on Cam Gear Marks - UPDATE

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So you found TDC turning motor both ways and using your math split in two for the dwell .
Great
You also dialed in the cam with your wheel checking timing .
That's my question as well, using a dial indicator can be a bit tricky unless you check it several times from both directions and split the difference. I much prefer a dead stop, but you can do it with a dial indicator. It would be fairly easy to double check it now with a stop placed through the sparkplug hole and turning the engine back and forth.
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Old 09-28-2020, 10:17 AM   #10
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Default Re: Question on Cam Gear Marks - UPDATE

I would have the distributor set up on a machine by someone in the know of how to set up a helmet.. Is the line to the vacuum brake hooked up with no leaks? Maybe try unscrewing the adjustment on the vacuum piston, if it always is pressing on the disk your advance is not working right.
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Old 09-28-2020, 04:34 PM   #11
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Default Re: Question on Cam Gear Marks - UPDATE

I confirmed the TDC marks with the hard stop method, it was on. I was very carefull when I did it with the dial indicator before, going back and forth. Within a degree at least. I have no feel for how much dwell resides at TDC, but would expect that to depend on bearing wear.
Photo shows where it idles, about 25*.

Terry, I havent confirmed the drivers side points are closing all the way yet. Kinda hard getting in there, and I have to drain the radiator and pull it to do anything on my stand. I'd like it if your right about that. I have a Sun machine, and I took a quick look at it before using the distributor but I did not check the dwell, just the point gap and alignment.
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Old 09-28-2020, 05:12 PM   #12
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Default Re: Question on Cam Gear Marks - UPDATE

If you've confirmed the timing marks, cam gear, etc, it about has to be in the distributor.
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Old 09-29-2020, 09:46 AM   #13
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Default Re: Question on Cam Gear Marks - UPDATE

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If you've confirmed the timing marks, cam gear, etc, it about has to be in the distributor.
I agree. I have taken the distributor out and tightened up the advance springs, hoping that will retard the baseline timeing. Have yet to test. Not wanting to heat up the garage today. Expecting 105* today.
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Old 09-29-2020, 11:33 AM   #14
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Default Re: Question on Cam Gear Marks - UPDATE

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Not wanting to heat up the garage today. Expecting 105* today.
That doesn't sound like fun!
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Old 09-29-2020, 11:47 AM   #15
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Default Re: Question on Cam Gear Marks - UPDATE

It can also be where/how the t-slot was put into the cam core. I've seen many mistakes on a variety of aftermarket cams, so nothing would really surprise me at this point. Another option would be to put an "advance plate" on the distributor (like we do on Harman Collins mags), so you have a lot more adjustment in the timing. If it truly has 25 degrees at idle and 35 total, then it explains that hard to start as the starter is trying to overcome the heavy advance at crank speed. Your TOTAL advance should be around 23 - 24 degrees.
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Old 09-29-2020, 01:30 PM   #16
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Default Re: Question on Cam Gear Marks - UPDATE

Was the cam timing checked?, not just by gear marks, but by valve action compared to piston position--
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Old 09-29-2020, 04:50 PM   #17
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Default Re: Question on Cam Gear Marks - UPDATE

Kurt, no that was not done. The reason being, the cam in question was run in my '40 for a period of time several years ago with no problems.

Bored&Stroked's comment as to starter struggling to overcome 25* advance sure rings true. I would never have considered that as I never have encountered this kind of problem. There is always more to learn.....
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Old 09-29-2020, 07:28 PM   #18
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Default Re: Question on Cam Gear Marks - UPDATE

Have you run engine with a vacuum gauge connected?
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Old 09-29-2020, 10:05 PM   #19
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Default Re: Question on Cam Gear Marks - UPDATE

No I have not. I only have the manifold single ports vacuum sources, not a central vacuum. The timeing is so off, I not sure that would be worthwhile. When I get the timeing issue resolved, I'll do a compression check. If that falls short, I'll do a leak down test. Timeing is the first issue of importance in my mind.
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Old 09-29-2020, 10:34 PM   #20
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Default Re: Question on Cam Gear Marks - UPDATE

as Brian suggested, wouldn't a vacuum gauge show improper valve timing?

Last edited by cas3; 09-29-2020 at 10:34 PM. Reason: add
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