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.

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.


Terry

Re: Question on Cam Gear Marks - UPDATE
 

Did you double check the TDC mark on the pulley when you had the engine apart?

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.

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 :confused:) 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.



Terry

Re: Question on Cam Gear Marks - UPDATE
 

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.

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.

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 .

Re: Question on Cam Gear Marks - UPDATE
 

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.

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.

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.

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.

Re: Question on Cam Gear Marks - UPDATE
 

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.

Re: Question on Cam Gear Marks - UPDATE
 

That doesn't sound like fun! :)

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.

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--

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.....

Re: Question on Cam Gear Marks - UPDATE
 

Have you run engine with a vacuum gauge connected?

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.

Re: Question on Cam Gear Marks - UPDATE
 

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

Re: Question on Cam Gear Marks - UPDATE
 

I no longer believe there is any valve timeing issue. Why would you suggest it in lieu of the overall story? Im open...

Re: Question on Cam Gear Marks - UPDATE
 

sorry russ, i follow the story, but its evolved over many days, and if i spoke of something irrelevant, its my memory, not the story thats the problem. just trying to help...best wishes

Re: Question on Cam Gear Marks - UPDATE
 

Russ, You say you haven't actually checked valve timing....the way I see it, if you're a tooth off, 44 teeth on the camgear divided by 360 degrees means each tooth gives just over 8 degrees. That equates to 16 degrees at crankshaft. being one tooth off would also advance the dissy by the same 16point whatever degrees. Then, depending on exactly where the points plate in distributor is located, could easily make up the rest of the ign advance you're seeing. As others have said, you need to degree in the camshaft first. And yes, a vac gauge will show if your valve timing is out, a very handy diagnostic tool I reckon. Good luck, Brian

Re: Question on Cam Gear Marks - UPDATE
 

If you look in the plug hole watch the valve operation, as the exhaust just is about closed the intake will just start opening, when you have both valves equally just a little open the piston should be at tdc for most cams

Re: Question on Cam Gear Marks - UPDATE
 

Kurt is spot on with his advice.

Re: Question on Cam Gear Marks - UPDATE
 

Further to Kurt's advice, if you observe through No6 plug hole, the valve overlap will occur as No1 is at TDC on the firing stroke.

Re: Question on Cam Gear Marks - UPDATE
 

When I install the cam gear, I always check for "Split overlap". We were taught that in shop in high school. Some early engines, like water pumps, didn't have timing marks. You don't need a dial indicator to tell you , You have a problem.

Re: Question on Cam Gear Marks - UPDATE
 

Ol Ron, can you explain the term "split overlap"? I am not familiar with that term and how you check for it.

Thanks, Zeke

Re: Question on Cam Gear Marks - UPDATE
 

Cam overlap is the time when both the intake valve and the exhaust valve are open around TDC. Split overlap is where both valve are at the same height above the valve seat and should be at TDC. I think the way Ron is using it is check TDC against both of the valves being in the same position.

As Kurt posted above: ...as the exhaust just is about closed the intake will just start opening, when you have both valves equally just a little open the piston should be at tdc for most cams

Re: Question on Cam Gear Marks - UPDATE
 

I might be wrong but overlap is something associated with performance engines. When I observe a flathead with a stock cam the exhaust closes then the inlet starts to open. They are not both open at a similar height at the same time.

But the bottom line is that the point at which the exhaust has just closed and the inlet is just about to start to open is the point at which the piston should be at TDC.

For reference, No.6 valves behaving as described above will coincide with No.1 at TDC having just fired. (On the firing stroke).

Re: Question on Cam Gear Marks - UPDATE
 

Yep, but that is what the term means. Guess you could call it "zero" overlap. :)

Re: Question on Cam Gear Marks - UPDATE
 

I welcome any and all advice. With the new thread, I know it's gotten hard to follow.

I think I have eliminated any valve timeing concerns. I have a Sun machine, but the RPM and dwell functions are inop.

Re: Question on Cam Gear Marks - UPDATE
 

Mart, i think im seeing what you described as to the cam check. With number one at TDC both valves are closed. At that time, number 6 exhaust is almost closed. Any clockwise rotation closes the 6 exhaust and begins opening 6 intake. This puts to rest any concern about valve timeing, right?

Terry, I checked the points, both sets are closing, so it is running on both sets. When I get it running again, I'll try to measure the dwell. What should dwell be on a helmet type dizzy? Also will see if my tightening up the advance springs have retarded the timeing any.

Not going to be able to run it again today. Was 108* yesterday and supposed to be 105* today. Can't run it without heating up the garage.

Re: Question on Cam Gear Marks - UPDATE
 

Dwell in the 34-36 degree range will be about right.



It finally cooled off here...last couple weeks have been pretty nice in 70's and 80's. I do hate the summer weather, especially when our 95-105 temps combine with high humidity here.



Damn, this engine is being a pain in the butt!


Terry

Re: Question on Cam Gear Marks - UPDATE
 

Russ, Please clarify "almost closed".

From memory, with a stock cam in a flatty, as you reach TDC, The exhaust will have just closed and the inlet will be about to start opening. If the exhaust is closing after TDC then the timing may be out.

There are 44 teeth on the cam gear, one tooth is 8.18 degrees. So if you were one tooth out, the overlap (rocking) of the valves would occur 16 crank degrees after or before TDC, depending on which way you were off.

In other words, it should be obvious if it is wrong.

If it isn't obviously wrong, it is probably right.

Mart.

Re: Question on Cam Gear Marks - UPDATE
 

Russ, you said in your earlier thread that this is an Isky 77B grind.
The specs for this cam state inlet opens 19* BTDC and ex closes 19* ATDC.
So, at exactly TDC, both valves should be slightly open should they not?
OK, you've located TDC. So you know where the crank is....now you need to degree in the cam so you know where it is.
And then, when cam timing is correct....since the distributor is driven off of the front of the camshaft, if timed up correctly on a timing fixture, the ignition timing will be right!

I still reckon you're one tooth off on the camgear/crankgear, that advances everything 16 point something degrees [crankshaft degrees]. Then, I dunno how your distributor is set up, but it could quite conceivably be advanced, adding up to the 25* you're seeing at idle.

Re: Question on Cam Gear Marks - UPDATE
 

Ya Brian, I only know one way to do these cam deals, so difficult to relate to just sticking them in. I know it is common practice, but I'm not a fan of tearing engines back apart chasing issues, LOL. Besides if your looking to maximize performance it's just about a requirement.

I'm sure Russ thinks I sound like a broken record (and I could be dead wrong), but I find it difficult to attempt to troubleshoot a problem like this without 100% nailing down all the basics.

Re: Question on Cam Gear Marks - UPDATE
 

The dwell on my Sun machine doesn't work so I hook up a separate dwell meter.

Re: Question on Cam Gear Marks - UPDATE
 

I agree with Brian.

Re: Question on Cam Gear Marks - UPDATE
 

Hey Mart, The intake opens just before the exhaust closes, so both valves are off their seats at the same time near TDC but only for a few degrees which is called overlap. The exhaust stroke is overlapping the intake stroke for a few degrees.
Good subject for a video on Mart's Garage.
Bill