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

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Looks wonky to me.
But if at least the intake is right , then it is as nm9 said, a 277* cam. And I'd guess probably 110 LSA cam in at 108.5.
That is way more than A bit of a cam, and should in no wise pull 19" of vacuum at typical idle-rpms of 750ish.
And the 67* ABDC intake closing angle will drive the Dcr right into the basement, unless you have decent static. That cam wants 10.5Scr,to get 165psi, at the 67*ICA.
With 8/1 Scr, the Dcr would come in at 6.3 and 117 psi cranking cylinder pressure. And you would need a great-big-'ol TC to get off the line, and 3.91s to
keep moving
So I say wonky cuz things don't seem to be adding up. Starting with the 19" of vacuum.

Going back to post#16: what you can do is pull the intake off, put the #1 cylinder at TDC overlap, and lay a short straightedge across the lifter bodies. I think this is what nm9 was talking about,sorta,lol.Rotate the crank back and forth a few degrees,until all four edges of the two #1 lifters are touching the straightedge. Then read the previously proven balancer. It should be BTDC, and within about 4 to maybe as far as 8 degrees.This will run, and run well.

I'm gonna guess the exhaust duration on that cam should be close to 8 degrees bigger than the intake. That would make it 285*. Doing the math on that and assuming a 110LSA I get an exhaust closing point of 34* ATDC. Couple that to your 30 from the degree wheel for a total overlap of 64*. Straight up would be half way between those two or 32*. Since you are at 30* on the intake, your balancer should read 2 degrees at split overlap , and I make it to be advanced. Remember I guessed at the exhaust duration and LSA and ICL,lol. But when you measure the split overlap, the guessing will be over.
Alternatively, you will need to recheck the whole caboodle with the lifters pumped up, or solids swapped in, and checking springs on the valves.Then the guessing will also be over.
Well except for the wonky 19" vacuum reading.But then again, if the ignition idle-timing reading really was 50* advanced, maybe 19" is possible;IDK, I've never tried that,lol.
And after all that, if the split overlap comes in OK, then a compression test will help clear things up.There is a HUGE performance difference from 117psi to 165 psi. And a large difference in ignition timing requirements as well.
 
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Well actually, I was talking about putting the dial indicator right on the lifter body, by either pulling the intake or rigging up some sort of substitute pushrod that would ride directly on the outer lifter body.

This looked wonky to me too at first. It is mirrored left to right from some cam timing diagrams. But then I got it. For anyone trying make sense of the OP's cam timing presentation, just remember that this is the degreeing on the damper. To look at it in the right way, then imagine the timing cover pointer moving around at the outside of this wheel in a COUNTERCLOCKWISE direction. (Think about it: If you are a bug riding on the damper, the timing cover point moves CCW to where you are.)

Then realize that the order of getting to the valve timing events is:
1. Ex Open
2. In Open
3. Ex Close
4. In Close

Yeah, AJ, I thought about if the engine cold get to 19" of vacuum with this duration with 50 degrees of initial.... I seriously doubt it, but like you, I have not ever tried that LOL
 
OK, on the compression, OP. Yes, it sure sounds this a low CR, wide duration cam situation. AJ makes a very good suggestion to take cranking compression readings.

And yes, if the exhaust lift is that low, then for sure that lifter has leaked down. If you ca, just fire it up for 10-15 seconds and get that lifter pujped up and then shut it down and see what you get.

Also, put the damper at TDC for #1 firing, make a mark on the distributor body directly below the #1 spark tower on the cap, then pull the cap, and see how far off the rotor is from that mark. If it is way off, then the rotor and/or cap may be indexed wrong to the distributor.
 
AJ/FormS said:
Looks wonky to me.
But if at least the intake is right , then it is as nm9 said, a 277* cam. And I'd guess probably 110 LSA cam in at 108.5.
That is way more than A bit of a cam, and should in no wise pull 19" of vacuum at typical idle-rpms of 750ish.
And the 67* ABDC intake closing angle will drive the Dcr right into the basement, unless you have decent static. That cam wants 10.5Scr,to get 165psi, at the 67*ICA.
With 8/1 Scr, the Dcr would come in at 6.3 and 117 psi cranking cylinder pressure. And you would need a great-big-'ol TC to get off the line, and 3.91s to
keep moving
So I say wonky cuz things don't seem to be adding up. Starting with the 19" of vacuum.

Going back to post#16: what you can do is pull the intake off, put the #1 cylinder at TDC overlap, and lay a short straightedge across the lifter bodies. I think this is what nm9 was talking about,sorta,lol.Rotate the crank back and forth a few degrees,until all four edges of the two #1 lifters are touching the straightedge. Then read the previously proven balancer. It should be BTDC, and within about 4 to maybe as far as 8 degrees.This will run, and run well.

I'm gonna guess the exhaust duration on that cam should be close to 8 degrees bigger than the intake. That would make it 285*. Doing the math on that and assuming a 110LSA I get an exhaust closing point of 34* ATDC. Couple that to your 30 from the degree wheel for a total overlap of 64*. Straight up would be half way between those two or 32*. Since you are at 30* on the intake, your balancer should read 2 degrees at split overlap , and I make it to be advanced. Remember I guessed at the exhaust duration and LSA and ICL,lol. But when you measure the split overlap, the guessing will be over.
Alternatively, you will need to recheck the whole caboodle with the lifters pumped up, or solids swapped in, and checking springs on the valves.Then the guessing will also be over.
Well except for the wonky 19" vacuum reading.But then again, if the ignition idle-timing reading really was 50* advanced, maybe 19" is possible;IDK, I've never tried that,lol.
And after all that, if the split overlap comes in OK, then a compression test will help clear things up.There is a HUGE performance difference from 117psi to 165 psi. And a large difference in ignition timing requirements as well.
Click to expand...

Thanks AJ - For clarification I could not get the idle to stabilize at 750, in that range it would sputter and die. Idle smooths out around 900-950 range, but even there would die moved from Park to a gear. I dropped my compression gauge, so I don't trust it. I'll pick up another this evening and take some measurements. If I go as far as pulling the intake, wouldn't be best to just pull the cam and read the stampings (they should be on the end that engauges the disty - correct?) - or does meassuring the overlap give something that I'm not understanding? Thanks
 
nm9stheham said:
OK, on the compression, OP. Yes, it sure sounds this a low CR, wide duration cam situation. AJ makes a very good suggestion to take cranking compression readings.

And yes, if the exhaust lift is that low, then for sure that lifter has leaked down. If you ca, just fire it up for 10-15 seconds and get that lifter pujped up and then shut it down and see what you get.

Also, put the damper at TDC for #1 firing, make a mark on the distributor body directly below the #1 spark tower on the cap, then pull the cap, and see how far off the rotor is from that mark. If it is way off, then the rotor and/or cap may be indexed wrong to the distributor.
Click to expand...

Thanks MN9 - I will get a compression reading and reading on where the disty is a TDC this evening. Thanks
 
I can't see from the pix but does this engine have a choke plate on the primaries? If so and it is closed while you did this adjustment, that may explain the 19" of vacuum. Are you trying these adjustments full warmed up or cool/cold, right after start up? The engine has to be fully warmed up, and the choke plate fully open before you do this.
 
nm9stheham said:
I can't see from the pix but does this engine have a choke plate on the primaries? If so and it is closed while you did this adjustment, that may explain the 19" of vacuum. Are you trying these adjustments full warmed up or cool/cold, right after start up? The engine has to be fully warmed up, and the choke plate fully open before you do this.
Click to expand...

It does have choke plates. The engine was fully warm and choke open when I was trying to adjust and got 19". At one point in this process, I did adjust the choke to be about 1/3 closed warm. If I recall, I could get the timing a bit lower with more choke but it was still popping out the pipes. Couldn't the 19" be the result of higher than normal idle (900-950)? I double checked my gauge with a hand pump, and it appears to be accurate.
 
Yes, a higher idle speed will certainly raise the vacuum levels. Your more recent descriptions may be pointing to a carb setup issue. If you got a more stable idle with the choke plate 1/3 closed, then that is a sign.
 
nm9stheham said:
Yes, a higher idle speed will certainly raise the vacuum levels. Your more recent descriptions may be pointing to a carb setup issue. If you got a more stable idle with the choke plate 1/3 closed, then that is a sign.
Click to expand...

Thanks - but the excessive initial timing it wants has me stumped. The carb is a new eldy 600. I set it up by adjusting both screws to 1.5 turns; then adjusted each (turning both the same amount in 1/4 turn increments while also adjusting idle screw) until I got max vac. Then tweaked both separate from each other a minor amount looking for stability of needle and/or additional increase.

Even when I increased idle screw to say ~1500 RPM and pull the advance down to below 30, it starts backfiring. So based on what you folks have taught me so far, even if the carb wasn't perfect, it looks like the cam in this engine is probably working against it - correct? Or do you think the timing and backfiring could be all carb related. I'll do a compression check this evening. Thanks again for the help!
 
When you say backfirinng, do you mean back through the carb? Or popping out of the exhaust pipes? Backfiring up the carb is typcially the timing being whacked out.

Be sure you look at the spark rotor position versus TDC and the distributro cap towers. That is rotor phasing. If it is out of whack, then it will crossfire to the wrong post on the cap; that issue can certainly change with timing adjustments. But it would not explain the engine being smoothest at 50 degrees advance.

What is the history of this engine, and what else can you tell folks about it?
 
You know what, A while back someone mentioned the pick-up polarity. I made a mental note of it. Now that popping in the exhaust has come out, it is time to verify that polarity.Ok that was JunkyJimmy post #14.
This is easy-peasy. Just disable the vacuum advance,put the timing lite on #1, and check the idle timing. Then slowly increase the rpm while watching the damper marks. The advance mechanism should advance on a steady march to it's maximum. There should not be any spark drop outs, no retarding at any time, and no jumping around of the mark, other than a couple of degrees that might be chain-slack.So to recap; you want to see a steady march to; timing- all-in.If you see missed sparks,double sparks, or if the timing goes to retard at any time, or starts dancing around, then STOP! Reverse the pick-up polarity. Retard the timing a bit, and start her up. Reset the base timing to 16ish, exact number not important. Then repeat the slow revving to all-in rpm looking for the steady march.And freedom from popping.If/when it works right, you will be able to reset the base-timing to something much more reasonable.

But, if your advance mechanism is working correctly, then you will have to verify the rotor phasing.
And if the rotor phasing is correct, then you will have to verify no water or other contaminants in the fuel. And if that's good, then,clean out your slow-speed circuit. You may have to boil out the metering block in a high-powered carb cleaning agent, to clear out the emulsion tubes, and IdleFeedRestrictions.

But before you go through all that, verify that the manifolds or headers are not sucking air at the head flanges. If air enters the headers there, you will for sure get exhaust popping.
 
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To check the pick-up polarity, wouldn't it be easier to just swap the wires connections with short wire jumpers?

FWIW, the pickup polarity being reversed would not change the timing on the damper, just the position of the distributor to get the timing set right. So by itself, it would not cause the timing set to need to be 50 degrees advanced. BUT it really WOULD effect the rotor phasing. So that is a good thought.

Checking the mechanical advance is a good idea. It might gives some clues.

Just a dumb question for the OP: You are putting the timing light pickup clamp on the spark wire to the #1 cylinder right? Just looking for anything clue.
 
Its not polarity. I'm using a pertronix ready to run disty. Only two wires, red/black and they are correct. I dbl checked rotor position, and at TDC the rotor is pointing at #1 (I had checked that early on, but a lots happened since then and needed to refresh my memory).

Now for the good (or not so good part). I checked compression on all 4 cylinders of the drivers-side bank (just easy to get to). All 4 read right around 100 PSI (95-107). Choke plate was open, as well as throttle plate. This is "dry", but it was running 2 days ago... Just too much cam for stock compression?
 
Did your gauge have a solid seal around the spark plug hole? Dang.... that IS looooow. I think you get some sort of prize for that.... Is this with a good compression gauge? (You mentioned not trusting yours.) DCR is coming in at the 6.3 to 6.4 range with GOOD cranking compression, based upon a 280 cam at 110 LSA and 106 ICL. That would be around 120 psi cranking.

Knoxville itself is not at all that high an altitude. Are you way up in the Smokies somewhere at 3000-4000 ft? I doubt that is the issue....

You have effectively a whole point less of compression, so either things are pretty worn out or that cam is pushing 310 degrees duration! Which sure as heck is not a MILD cam LOL. OR the cam is reeeeely badly retarded. It would take an intake closing angle of around 80 degrees ABDC to drop the stock SCR to that level of DCR (around 5.6) and get 100 psi cranking pressures with good rings.

I think you need to re-do your cam timing first on the lifter body, and see what you really have cam wise. Or see if you can find some ID on it. And it won't hurt to do the other side and record them all in detail and try another compression gauge.

BTW, I recall a Vega engine 'back in the day' with the usual really worn cylinders, and it would take 30-40 degrees of ignition timing advance and would idle noticeably better.
 
Some one could have tried to advance the cam by adding a 4 degree key in the cam but installed it backward. I have done it several times......but i degreed the cam and figured it out. If you pull the cam, pay close attention to the cam key way. does it look half sheared off? If so, is the key making the sprocket move forward or back.
That is some low compression. even for someone like me. that live at 6600 feet.
 
New gauge, but I'll try to verify it in something. Not that high, 1200' or so. I don't think the engine is worn all that much. I've had it running for a while over several driveway idles - round the block trips. There was no noticeable oil burn or blow-by. Keep in mind that the lifters have leaked some; so I would think the compression, after it had really ran for a while, would be 10-20ish psi higher. I'm really just thinking (hoping) that the cam installed wasn't a good fit. I'm going to pull the intake and measure directly on the lifters to see what they say. And/or see if there are markings on the cam.

In the mean-time. Anyone have any thoughts on a decent cam for: 360, 30 over, stockish heads (shaved a bit, but probably not enough to impact CR much - and I don't know the valve size - probably stock for 1978), 4bbl RPM intake w/600cfm eldy, schumacher headers into duals - 2.5"). 904 w/stock converter, The rear is still the /6 rear, but I was hoping to change that in the real-near future to something in the 3.55 range once I get the engine sorted. 15" 60 series tire/wheels. Manual brakes and aftermarket AC... Just a street engine, no real performance goals. But I want don't really want to change springs or rockers with this engine if I can avoid it. I was thinking the Comp High Energy 260H or 268H. But as I said before, cams are somewhat "magic" to me! So if those that know better could chime in, I would appreciate it.

My end goal is to get the car sorted with this engine, then go with an upgraded 360 at a later date (still a street engine tho).

Thanks again - I've learned a lot so far!
 
Cudafever said:
Some one could have tried to advance the cam by adding a 4 degree key in the cam but installed it backward. I have done it several times......but i degreed the cam and figured it out. If you pull the cam, pay close attention to the cam key way. does it look half sheared off? If so, is the key making the sprocket move forward or back.
That is some low compression. even for someone like me. that live at 6600 feet.
Click to expand...

Thanks Cudafever - I replaced the timing gear, and it looked like a standard key, but I'll dbl check when I go to pull it. The set I removed was a single keyway, and the set I installed was a 3 keyway 0/+4/-4. I did install on 0.
 
Well let's wait and see what you really have before moving on. There are just too many variable as yet.
But the cylinder pressure, the Idle vacuum/timing, and the bit of a cam, are just not adding up.Well they are but nobody wants to say it yet, or I missed it.
 
If your intake lifters leak down, the durations go down and the cranking compression will go UP. So it will only get worse when the lifters pump up. And I don't think your loss of exhaust duration shown on your timing wheel will not be enough to effect air movement in and out at low engine speeds and thus lower cranking compression.

Unfortunately, I don't think you can yet rule out serious cylinder or ring wear based on the data presented and the limited running use. With enough wear to drop cranking compression, you won't necessarily get a ton of blowby or oil smoke out of the breathers at low RPM's; BTDT. Who knows if the rings were seated right.....

Your cam choices are right where I would go. Keep the lifts in the.440" range or thereabouts to keep the stock springs and such. I would tend to stay with a shorter duration to keep the low RPM torque up higher for street cruising.
 
I pulled the cam. Its an Elgin E1223P. I found the specs online. I guess this was the guys idea of a "mild cam".

Camshaft Model Or Series: Performance
Year: 1964 - 2003
Make: Chrysler
Engine: 273 - 360
Camshaft Type: Hydraulic Flat Tappet
Intake Valve Lift: .441"
Exhaust Valve Lift: .441"
Advertised Intake Duration: 288°
Advertised Exhaust Duration: 298°
Intake Duration @ .050": 218°
Exhaust Duration @ .050": 228°
Lobe Separation: 109°/119°
Recommended Lifters: HL-2011
Quantity: Sold As Each
 
Good info. I looked it up too and the durations are 276/288. LSA looks like 114 with a 109 ICL 'as ground'. Not terribly radical buut.

To be able to compute out to the cranking compression you found, with your cam:
- was installed wih little or no advance (That's not the same as putting the key at 0 degrees.)
- the head gaskets are Felpro 5883PT's
- the pistons are deeper dished or lower compression height truck pistons

With the cam out, it would be easy to put in another one, like a 260 or 256ish range with the same lift. (Crane, Lunati Voodoo or Comp XE/HE. Is that your thought?

Do you feel like pulling heads and looking things over and putting back in some thinner head gaskets? (Mr Gasket 1121G) I know I would want to put some sort of bore gage on a few bores to see if there is taper or out-of-roundness, and see how far the top edge of the pistons are from the deck and the dimensions of the piston top's dish.
 
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nm9stheham said:
Good info. I looked it up too and the durations are 276/288. LSA looks like 114 with a 109 ICL 'as ground'. Not terribly radical buut.

To be able to compute out to the cranking compression you found, with your cam:
- was installed wih little or no advance (That's not the same as putting the key at 0 degrees.)
- the head gaskets are Felpro 5883PT's
- the pistons are deeper dished or lower compression height truck pistons

With the cam out, it would not be easy to put in another one, like a 260 or 256ish range with the same lift. (Crane, Lunati Voodoo or Comp XE/HE. Is that your thought?

Do you feel like pulling heads and looking things over and putting back in some thinner head gaskets? (Mr Gasket 1121G) I know I would want to put some sort of bore gage on a few bores to see if there is taper or out-of-roundness, and see how far the top edge of the pistons are from the deck and the dimensions of the piston top's dish.
Click to expand...

nm9 - Thanks, I'll trust your specs. I couldn't find this cam in Elgin catalog, but found it on a speed shops site. I did use a felpro gasket when I installed the heads. The pistons didn't seem to have much dish (I've seen worse), but this is my first SBM - so no real reference. Although they were pretty deep in the hole - didn't measure but it was probably pushing -0.100 Yes, I'm looking at just putting in another cam in the 260 or lower range. I have a bad habit of feature-creep, and I was only planning to use this engine to help me sort out the rest of the car. So even if it is more worn than I had hoped, it isn't going to see a whole lot of duty anytime soon... Besides, this always give me a good excuse for the future upgrade. I'll get a cam installed and degree'ed, retest compression and report back.
 
Just to update... Installed the Comp 260H cam this weekend. I installed it straight up, and double checked with a small homemade degree wheel. Based on this homemade setup, CCL and open/close were about 2 degrees retarded. But I figured that could be well within the margin of error with my equipment, so left it as is instead of trying to change things without data I was more sure of. After break-in, it now idles smooth @ 15 degrees initial advance. Compression went up some, ~ 120 on the two I checked. Still need to better adjust the carb, but all in all a much better running engine. Thanks for all the help.
 
Good deal.... thanks very much for the update and congrats on the good result. Yeah... low compression ratio and a big cam can be problematic; it'll work if wound out but be doggy at low RPM's...

With that cam installed 2 degrees behind straight up, the cranking compression comes out to around 115 psi (based on certain assumptions), so things are making sense. And the initial timing is looking normal. I would not hesitate to advance it some if you have the time to limit the total mechanical advance. But, with the low-ish DCR (still in the mid 6's), I would not be surprised if you could approach 40 degrees total or even a bit more and not have any detonation issues.

Good luck on sorting out the rest of the car!
 
Thanks for up dating this thread. To many time a problem is fixed but never reported back. Which make at thead useless for future reference.
This is now, a great thread for someone who want to put a performance cam in,.... But hasn't learned or isn't aware of the pit fall that could happen.
You have installed the performance cam that "fit" your combo. And without driving it, you are already happier.
I bet your "butt" odometer says it faster too!:)
 
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