LA360 initial timing too high - are there different timing covers?

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Jason Ford

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Hello all. I've lurked around here for a while (lots of great info that helped me on my 73 Scamp project - thanks), but I've not been able to find info on my current issue... Timing way to high.
Background, 73 slant car that I transplanted a 78 360 into it. I bought the 360 used, but was "told" it was a fairly recent rebuild with 30 over pistons and a mild cam. Before I installed the engine, I did pull the heads and had those re-worked (it did have 30 over pistons). I also pulled the timing cover to check the chain/timing - everything looked correct and new. I did install a Edelbrock 318/360 intake, 600cfm Edelbrock carb, and a Pertronix billet distributor (stock no mods to springs/etc).
The engine is running in the car, but when I tried to set timing I couldn't see the marks no matter how much I cranked the distributor in either direction (standard light - no adjustment). I set timing by ear, then set the carb up to max vac - about 19 inches. I checked TDC (not with a stop but with a screwdriver in the hole just to see that things were close - they were). Today I picked up an adjustable light. With the engine adjusted by ear - using the dial the marks line up at around 50 degrees. If I crank the disty down to 30 or so, it starts running poorly and pops out the pipes. I'm not getting any starter kickback @ 50, not over heating, so I don't really believe the timing is at 50 initial (oh yes - vac/adv disconnected; idle around 900)... So, were there different covers with different marks through the years? If so - any idea how to identify? Any other ideas? Also - I've tried two balancers - the stock on and a new one from summit, both read the same. Sorry for the long post, and thanks to those who read it!
 
Sounds like a slipped hamonic balancer ring or an early balancer woth the timing marks on the other side pf the engine. But that would be an internal balance damper, not an external balance damper a 360 has, unless the 360 was balanced internaly with the old damp[er.
 
You are on the right track "checking" but you do NOT want to trust a screwdriver. Us a piston stop, which you can buy or make. Unhook battery, screw stop into no1 hole after making sure piston is "down a ways". slowly wrench engine until it stops. Make a mark onto the damper under TDC. Reverse the engine and wrench it around backwards until it again stops. Make a second mark. True TDC will be halfway between your temporary marks

I made this one........and have had it.......since the '70s. Yeh, I'm old

stop2-jpg.jpg


If you buy one, make sure you fiddle with it and install a lock nut so the stem doesn't "waddle around"

pow101330-1-web.jpg
 
IIRC, your timing marks on the cover should be over on the driver's side. Pre-70 SBM timing marks cast into the cover were on the passenger side.

If you checked the timing marks versus TDC and found them to be on 0, then the damper ring has not slipped. And since you tried 2 dampers, including a new one, then that seems like it can be ruled out. How close was 'close'? I agree.... the screwdriver method can be 10-15 degrees off. Use a piston stop.

Do you have the adjustable light set correctly? I hate tome mention 'read the instructions' buuuut.... LOL

Do you have an MSD ignition system?
 
^^If you have accurately checked the mark as above, and it won't run "where you think" it's timed, then the cam timing is probably wrong
 
Thanks for the replies. The original balance looked correct for a 360 (based on google searches), the after market one was a summit pro street - It has graduated marks up to 60, which I thought would help me figure things out - pics attached.
The marks are on the driver's side. I do have a piston stop, and using it to find TDC is the plan for this evening - I'll take some pics. I just went back and re-read the instructions on the light, there wasn't a specific setup procedure. The manual just says turn the dial until the marks align, then what the dial reads is the advance. No MSD, it has the Pertronix ready to run distributor. It has the HEI module inside. Thanks again

360a.jpg


360b.jpg


pro-street.JPG
 
When you use that light, you align the 0 marks on both damper and cover when you vary the dial. The pickup line to the timing light is on the #1 cylinder, right?

Some timing lights get fooled by an MSD ignition and its multiple pulses, which is why that question was asked.
 
Thanks all, I think I've figured it out. It is a valve timing issue. The pic below is after using the piston, stop. The black marks in the red boxes are were it stopped on each direction. I didn't measure, but can see it is close enough for government work! Now that the mark was proven, I then rotated back to TDC and checked where the disty was pointing - almost straight forward, see other pic. Then, still at TDC, I put 60 psi of air in with a leak-down tester; of which about 30% was leaking. A quick trip back to the rear of the car to put my ear on the pipes, and I could hear where that 30% was going. Well, at least I'll get a new chain and gear set out of this :). Thanks all

360_tdc.JPG


disty.JPG
 
If you have some idea of the cam, you can actually measure valve timing and double check it. For stock cams, there is a procedure in some of the service manuals. You can download many of 'em free, at Mymopar. Otherwise you can pull the driver side valve cover, put an indicator or even just visually watch the no 1 valves. If you can't "degree" the balancer, you can figure them by inch measurement around the thing and mark it.
 
Jason Ford said:
Thanks all, I think I've figured it out. It is a valve timing issue. The pic below is after using the piston, stop. The black marks in the red boxes are were it stopped on each direction. I didn't measure, but can see it is close enough for government work! Now that the mark was proven, I then rotated back to TDC and checked where the disty was pointing - almost straight forward, see other pic. Then, still at TDC, I put 60 psi of air in with a leak-down tester; of which about 30% was leaking. A quick trip back to the rear of the car to put my ear on the pipes, and I could hear where that 30% was going. Well, at least I'll get a new chain and gear set out of this :). Thanks all
Click to expand...
How does this prove the cam-timing is off?
I mean you could assume it's off.................. But 30% leakage doesn't prove it.
And the dizzy can be installed anywhere and the wires just moved to where they need to be.
 
AJ/FormS said:
How does this prove the cam-timing is off?
I mean you could assume it's off.................. But 30% leakage doesn't prove it.
And the dizzy can be installed anywhere and the wires just moved to where they need to be.
Click to expand...
Hi AJ, correct it is an assumption. But what I didn't mention is that with the air in the cylinder - I rotated the engine and the leak almost stopped at around 40 degrees BTDC (engine was fighting me with pressure in it, so hard to be exactly sure where the leak stopped), so the valves are closing; just at the wrong time. Perhaps it could be something other than valve timing, but I think that is the most likely culprit and the next place I'll check.
 
Jason Ford said:
Hi AJ, correct it is an assumption. But what I didn't mention is that with the air in the cylinder - I rotated the engine and the leak almost stopped at around 40 degrees BTDC (engine was fighting me with pressure in it, so hard to be exactly sure where the leak stopped), so the valves are closing; just at the wrong time. Perhaps it could be something other than valve timing, but I think that is the most likely culprit and the next place I'll check.
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Correction. After TDC, not before.
 
I believe your polarity on dist is reversed, we run a stock mopar dist with a 4 pin hei module. Had same thing happen, switched motors and dist and exact same issues
 
Good on the TDC mark... sure looks pretty close. Your screwdriver-on-the-piston feel is better than average!

Ummmmm...... when the damper is at 0 and the engine is at TDC, there are 2 cylinders at TDC: #1 and #6. One will be at the top of the compression stroke and the other will be at the top of the exhaust stroke. So if you tested the wrong one (the one at the top of the exhaust stroke), then naturally the exhaust valve will be open, and will close if you rotate the crank to so many degrees after TDC. (Which sounds like it is what you found..... so are you testing the wrong cylinder?)

Did you look at the rotor positions and then the cap position to see if the rotor was pointing almost directly at one of the cap's spark towers? (I.e., rotor phasing correct?) And then trace from that spark tower to see if that spark wire was going to #1 or #6, and test on that cylinder?
 
40* BTDC may not be wrong at all, depending on the cam installed.

The fun cam, the 268*/110,in at 106 has the following events
Intake opens at 28* BTDC, closes at 60*ABDC.

The 292*/108 cam has these events, in at 106:
Intake opens at 40* BTDC,closes at 72* ABDC

The stock 318cam is a 240/248/112 cam and it has these events;in at 108:
Intake opens at 12* BTDC,closes at 48ABDC

But 40* ATDC, is either a wrong interpretation of the degree wheel, a slipped balancer ring or a dead engine with a seriously mislocated cam, as in will not run.

Here is the quick check;
pop the driver's side Valve cover off,put the #1 piston at TDC on the OVERLAP stroke.Rock the crank back and forth about 10 degrees each way, and watch the rocker arms. If the cam is in close enough to run, then,the exhaust should be just closing and the intake should be just opening: as the crank rotates thru TDC,plus/minus a few degrees. The lifts will be very nearly the same, but depend a lot on lifter bleed-down. This is a quick check only, and may save you a couple of hours work if the overlap centerline timing seems close.
 
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nm9stheham said:
Good on the TDC mark... sure looks pretty close. Your screwdriver-on-the-piston feel is better than average!

Ummmmm...... when the damper is at 0 and the engine is at TDC, there are 2 cylinders at TDC: #1 and #6. One will be at the top of the compression stroke and the other will be at the top of the exhaust stroke. So if you tested the wrong one (the one at the top of the exhaust stroke), then naturally the exhaust valve will be open, and will close if you rotate the crank to so many degrees after TDC. (Which sounds like it is what you found..... so are you testing the wrong cylinder?)

Did you look at the rotor positions and then the cap position to see if the rotor was pointing almost directly at one of the cap's spark towers? (I.e., rotor phasing correct?) And then trace from that spark tower to see if that spark wire was going to #1 or #6, and test on that cylinder?
Click to expand...

Thanks - The rotor was pointing almost straight forward - where my number 1 is wire is.
 
AJ/FormS said:
40* BTDC may not be wrong at all, depending on the cam installed.

The fun cam, the 268*/110,in at 106 has the following events
Intake opens at 28* BTDC, closes at 60*ABDC.

The 292*/108 cam has these events, in at 106:
Intake opens at 40* BTDC,closes at 72* ABDC

The stock 318cam is a 240/248/112 cam and it has these events;in at 108:
Intake opens at 12* BTDC,closes at 48ABDC

But 40* ATDC, is either a wrong interpretation of the degree wheel, a slipped balancer ring or a dead engine with a seriously mislocated cam, as in will not run.

Here is the quick check;
pop the driver's side Valve cover off but the #1 piston at TDC on the OVERLAP stroke.Rock thecrank pack and forth about 10 degrees each way, and watch the rocker arms. If the cam is in close enough to run, then,the exhaust should be just closing and the intake should be just opening: as the crank rotates thru TDC,plus/minus a few degrees. The lifts will be very nearly the same, but depend a lot on lifter bleed-down. This is a quick check only, and may save you a couple of hours work if the overlap centerline timing seems close.
Click to expand...

AJ - I think you might be right. I pulled the timing cover, and the marks were in the correct position. You are also correct on ATDC//BTDC - I mis-remembered the marks. See pics. It would help if I knew the cam that was installed, but unfortunately I purchased this thing as is and the person I bought it from wasn't the builder. I'll go pull the valve cover now and see what that looks like. So even if it has a cam with a lot of overlap - I should be able to get initial time to something lower than 30, correct? Could the disty drive gear be off and cause this?

timing_marks.JPG


bal.JPG
 
Since you have it tore down, and IF you know the cam specs this would be a GREAT time to degree it and see where it sits.......you may want to change it
 
Are those pics current or archived?
What does the second pic attempt to show?
You can put the dizzy in a bazzillion different ways and make it run. Well maybe not quite a bazzillion, but at least 8. It's just common practice to put it in where the factory puts it, cuz then the wires are where the mechanics expect to find them.It is possible to put the reluctor on the wrong way, but then the rotor tip ends up in never-never land.
It is very difficult to verify dot-to-dot withe the gears installed. It requires you to estimate the centers of the cam and the crank, and then imagine a straight line connecting those imagined centers and the two dots. This is hard enough to do on the bench, never mind in the chassis.
There is no cam I have ever installed up to the 292/292/508 that I couldn't make idle at 5*advance.Key-word is make.
IMO, there is no cam I have ever installed,in a stick-car,that I didn't like far less than most guys will tell you to run. I like to run my 230*@050 Hughes HFT at 14/16initial.. It likes 32/34 for WOT, sometime after 3200 on 87E10, and it likes 45/55 at cruise. I give it what it likes, rather than forcing her to take what I might think she should be able to handle. Overlap has nothing to do with ignition timing, as it concerns street cams.
But the camshaft split overlap period should occur very near to TDC on the balancer ,very rarely retarded, and usually up to 6 or 8* advanced.
 
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With the crank at 0 degrees, and the crank and cam sprocket dots lined up with the dots at 12 and 6 o'clock as you show, #6 cylinder is the one that should be firing, not #1. If the rotor is pointing at the #1 spark wire tower on the cap with the cam set as you show, then the firing order is theoretically 180 degrees out.

How it is running with 50 degrees advance with that situation, I have not yet figured out! Perhaps the cam is really whacked out on the cam timing, with the cam key ground waaaaay off from where it should be, or either sprocket's keyway is indexed wrong (which has happened). Note that the crankshaft's keyway looks to be in the right post in your pix, and that makes sense with the damper lining up correctly.

Sounds like doing some thorough checks on the cam timing is in order at this point! Doing as AJ suggests is the starting point: rock the crank back and forth past 0 degrees and watch the intake and exhaust on #1; they should be both slightly open in this situation; they will typically be open equal amounts at a few degrees of crank rotation BTDC.

Then get the degree wheel on it and find the exact cam timing.
 
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I put a degree wheel on the balancer, and used a dial gauge to measure int/ext opening closing (keep in mind its not ran in a few days, so I'm sure the lifters are down some). But I did get something close to normal (although it looks like ext closes a bit late too me; However, I'll be the first to admit that I only have a high level understanding of cams) - I put the data on the wheel in the second pic. I did rotate through 4 times taking each measurement, then averaged to help with any human error. Does this look normal to those that know?

For future reference, here is a site to get a degree wheel in various sized - just print and stick: Printable Timing Tape - All Sizes - Imperial
36-_wheel.jpg
timing.jpg
 
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That presentation took me a while to view right LOL. But I think I got it figured out.

It looks generally OK. But the exhaust duration (252) is shorter than the intake duration (277), which is not seen in SBM cams, and so that says the exhaust lifter has very likley leaked down and is throwing off the results. If the exhaust opening and closing angles were moved 13 degrees in each direction (to widen the exhaust duration to match the intake duration), then the cam timing would come in at about 5 degrees advance, which is close to where it likely should be.

To be properly accurate, then you'd have to take measurements right on the lifter bodies.

So were your pistons dished ones? And what is your cam supposed to be? I have to wonder how low the DCR is in this thing, which is requiring you to put in lot of initial advance to make it idle OK. And getting up to 19" vacuum with this cam duration is not making any sense at all.....
 
nm9stheham said:
That presentation took me a while to view right LOL. But I think I got it figured out.

It looks generally OK. But the exhaust duration (252) is shorter than the intake duration (277), which is not seen in SBM cams, and so that says the exhaust lifter has very likley leaked down and is throwing off the results. If the exhaust opening and closing angles were moved 13 degrees in each direction (to widen the exhaust duration to match the intake duration), then the cam timing would come in at about 5 degrees advance, which is close to where it likely should be.

To be properly accurate, then you'd have to take measurements right on the lifter bodies.

So were your pistons dished ones? And what is your cam supposed to be? I have to wonder how low the DCR is in this thing, which is requiring you to put in lot of initial advance to make it idle OK. And getting up to 19" vacuum with this cam duration is not making any sense at all.....
Click to expand...

Thanks for bearing with me... Yes, I assumed the ext had leaked down some. When I tried to measure lift, ext was in the low 0.360 range; while int kept reading around 0.430ish. If my vac gauge is accurate, it was pulling right around 19 at idle, with only about 0.5 fluctuation. Unfortunately the only thing I know about the cam is that its not stock. I was told the engine was a basic rebuild with a mild cam when I purchased it. I did pull the heads, and the pistons were dished - and were 30 over stock, and were down in the hole a bit. So I assume the CR is still around stock values (8'ish:1). When I had the heads off, I had a shop do a valve job and check the heads. They had to shim a few springs, and told me that the valve seats required some heavy grinding. Which is why I wanted to make sure I didn't have to much advance and risk damaging them again. But at this point, I'm wondering if I should ignore my OCD and just put it back together; setting ignition time the best I can. Not looking for much out of the engine, just a weekend cruiser. Thanks
 
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