Engine bench start... won't
May 20th, 2013, 10:18 AM
#41
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180 degrees out on the crank or the cam? I'm confused, I must admit. In my mind neither the compression or the exhaust stroke should have the intake valve open, which means going 180 degrees on the cam would still be wrong. I measured it by looking at the pushrods top while turning back and forth in small increments on the balancer not, and then seeing that the balancer timing mark was at 12 BTDC.
It's quite likely I'm overlooking something here.
It's quite likely I'm overlooking something here.
May 20th, 2013, 10:31 AM
#42
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Yes, that's why it's frustrating.
You're probably overlooking something very simple, and if even one of use were there we might catch it, just by virtue of being another set of eyes, but we've got to rely in text for our information.
As far as the 180°, I was referring to the rotor in the distributor.
The round diagram on the cam card represents one cam rotation (or one distributor rotation), which is to say two crank rotations, so 180° of the rotor = 360° of the crank.
- Eric
You're probably overlooking something very simple, and if even one of use were there we might catch it, just by virtue of being another set of eyes, but we've got to rely in text for our information.
As far as the 180°, I was referring to the rotor in the distributor.
The round diagram on the cam card represents one cam rotation (or one distributor rotation), which is to say two crank rotations, so 180° of the rotor = 360° of the crank.
- Eric
May 20th, 2013, 10:33 AM
#43
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Ah, gotcha. My point still stands, then. :P Yeah, this is a frustrating way to troubleshoot, but it's all I've got right now.
I installed the cam dot to dot, like in the CSM, for reference.
I installed the cam dot to dot, like in the CSM, for reference.
.
May 20th, 2013, 12:06 PM
#48
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The mind is a mysterious thing, it seems.
May 20th, 2013, 03:44 PM
#51
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If the rocker arms on the opposing cylinder in the firing order start to open/close as you move the crank balancer slightly to each side of TDC/0 degrees then the other opposing cylinder is on the compression stroke.
Put half of the firing order on top and the remaining half on the bottom like this:
1 8 4 3
6 5 7 2
The numbers directly above and below each other are the opposing cylinders, so if the rockers open/close just on either side of TDC/0 on the balancer on #6, then #1 is on the compression stroke. If #1 rockers open/close just on either side of TDC/0, then #6 is on the compression stroke.
Put half of the firing order on top and the remaining half on the bottom like this:
1 8 4 3
6 5 7 2
The numbers directly above and below each other are the opposing cylinders, so if the rockers open/close just on either side of TDC/0 on the balancer on #6, then #1 is on the compression stroke. If #1 rockers open/close just on either side of TDC/0, then #6 is on the compression stroke.
May 20th, 2013, 04:20 PM
#52
Yes that means it's on TDC, but not necessarily on the firing stroke. Remember that it's every other time around that the TDC is on it's firing stroke, not every time. Take out #1 plug, have somebody bump the starter and when you feel the whoosh of the compression at the time the mark comes around to TDC, then the rotor should be pointing to the #1 cylinder.
TDC. Any engine should start at that point. Good
Luck
May 21st, 2013, 01:17 PM
#53
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On a point ign. if you know #1 is on comp. stroke, you can line up timing marks to what the book calls for, attach a test light to coil wire, (dist side), and ground, turn key on, rotate dist. until light just comes on. Engine will be in time.
May 21st, 2013, 01:25 PM
#54
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I'm fairly (that is to say completely) certain the ignition timing has been right at some point, either as I originally installed the distributor, or as I installed it 180 degrees rotated afterwards/swapped wires.
May 21st, 2013, 01:55 PM
#60
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Someone has to be the first. I've seen first-hand how things can come less than perfect from the factory. My first HEI came with seven metal towers and one plastic tower, for example. Of course I didn't take a picture. 
But I digress.
But I digress.
May 21st, 2013, 03:13 PM
#61
Seth that sucks that you have to be away from it that long. I know it will eat at you until you get back to it. Most of us have been where you are right now scratching our head on a similar problem. My guess is you have changed a lot around trying this and trying that. IMHO when you get back to the car start from step 1 and re check everything to do with the timing. If it is backfiring through the exhaust as you described something is way off.
May 22nd, 2013, 03:09 PM
#66
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It's an aftermarket HEI that came from my running '71 engine. It's now back on the '71 engine, running flawlessly again. The same battery was used for attempting to start the engine that is used to start the running car with the '71 engine.
May 27th, 2013, 08:30 AM
#67
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Well, it's time to go to basics and assume nothing is correct. Not even the drilling/ marks on the timing sprockets. Is there any chance you got a cam ground for the 45 degree engine, in a 39 degree block, or vice versa?
If the cam events are not correct, then no amount of fiddling with spark timing is going to help. This is yet another reason to use the PUFF OF AIR method to ascertain TDC compression... if the cam is way off, you will likely get a weak compression signal. At 12 BTDC between intake and exhaust strokes, you could reasonably expect both I and E valves to be open, yes. The E is just closing, and the I is just opening, thus term "overlap." Near TDC between compression and power strokes, no valve should be open, for that would release the compressed mixture and the power contained therein.
The cam card I saw above was lacking a lot of info, poorly made. I saw open-duration figures, but no numbers for exactly when the opening and closing occur. But, from the duration, and assuming that the lobe is symmetrical, you should be able to determine "about" where the valve events should take place- opening and closing, and lobe centerline or max lift or "top" as you say... [At first I thought it was a typo and you meant "stops"]
Mechanically find the piston true TDC by piston stop or at least a wire contacting the piston. Verify your balancer's timing mark and timing tab are providing accurate information, and showing balancer's mark in alignment with the tab's zero when the piston is in fact at TDC. This can be done before any major dismantling, while the balancer is still in place.
Can you degree the cam? Even with poor accuracy like with a homebrew system? A handmade or printed degree wheel on cardboard would be a start.
So, start with timing cover removal, which you were going to do anyhow. Put the crank at TDC and photograph the setup *as found*, before altering things. Chalk or a paint pen [white-out, etc.] makes the timing marks easier to see. If all is well, you won't have to dismantle further.
Re-verify that with crank sprocket timing mark at 12:00 straight up, the cam timing mark is either 12:00 or 6:00- one is TDC between compression and power strokes, the other is TDC between exhaust and intake strokes. There is usually a "V" cast into the block at the top of the timing cavity to help you visually align the cam gear mark if it's at the 12:00 position. Be aware that some aftermarket sprockets have several marks on the crank sprocket, with each one being a slightly different amount of cam advance. In any event though, the crank's KEY will be right about in line with the axis of the left bank of cylinders, at TDC #1. It sounds like you used an alternate timing mark... with the crank key [and thus the crank] not correctly positioned with respect to the cam.
Put crank at TDC with key more or less in line with #1 cylinder.
photograph the crank and cam sprocket timing marks being in proper alignment.
Put on your best degree wheel & dial indicator, and record all pertinent cam events- opening, centerline ["tops" as you say], and closing, for both I and E valves. Openings and closings can be at various amounts of lift. The ones I have seen are zero lift [hard to detect], 0.006" lift, and 0.050" lift. Any of these will require a dial indicator for any sort of accuracy. It is assumed that you have one and know how to use it, or will get/learn, or turn this job over to a competent advisor. The lobe centerline or max lift is usually pegged by recording the crank position at some small amount less than max lift, on either side, then assuming that the center is halfway between. So, if the lobe max lift is 0.380 then record crank positions at oh say 0.350 lift- one on the way up, and one on the way down. Midway between those positions will be the lobe centerline.
As long as the cam events are happening within a degree or 3 of where they should be [again, I did not see those numbers specified on the cam card], then the cam timing is correct and you should be able to spin the engine and get a strong compression signal. I find a small CORK makes a good pressure detector too though they do tend to fly away and get lost, and/or scare the crap out of you if you forget you corked the spark plug hole and later spin the motor.
Once compression and cam timing is in place, it sounds like you have a good handle on how to set spark timing properly, so it should be no problem to achieve joy then.
If the cam events are not correct, then no amount of fiddling with spark timing is going to help. This is yet another reason to use the PUFF OF AIR method to ascertain TDC compression... if the cam is way off, you will likely get a weak compression signal. At 12 BTDC between intake and exhaust strokes, you could reasonably expect both I and E valves to be open, yes. The E is just closing, and the I is just opening, thus term "overlap." Near TDC between compression and power strokes, no valve should be open, for that would release the compressed mixture and the power contained therein.
The cam card I saw above was lacking a lot of info, poorly made. I saw open-duration figures, but no numbers for exactly when the opening and closing occur. But, from the duration, and assuming that the lobe is symmetrical, you should be able to determine "about" where the valve events should take place- opening and closing, and lobe centerline or max lift or "top" as you say... [At first I thought it was a typo and you meant "stops"]
Mechanically find the piston true TDC by piston stop or at least a wire contacting the piston. Verify your balancer's timing mark and timing tab are providing accurate information, and showing balancer's mark in alignment with the tab's zero when the piston is in fact at TDC. This can be done before any major dismantling, while the balancer is still in place.
Can you degree the cam? Even with poor accuracy like with a homebrew system? A handmade or printed degree wheel on cardboard would be a start.
So, start with timing cover removal, which you were going to do anyhow. Put the crank at TDC and photograph the setup *as found*, before altering things. Chalk or a paint pen [white-out, etc.] makes the timing marks easier to see. If all is well, you won't have to dismantle further.
Re-verify that with crank sprocket timing mark at 12:00 straight up, the cam timing mark is either 12:00 or 6:00- one is TDC between compression and power strokes, the other is TDC between exhaust and intake strokes. There is usually a "V" cast into the block at the top of the timing cavity to help you visually align the cam gear mark if it's at the 12:00 position. Be aware that some aftermarket sprockets have several marks on the crank sprocket, with each one being a slightly different amount of cam advance. In any event though, the crank's KEY will be right about in line with the axis of the left bank of cylinders, at TDC #1. It sounds like you used an alternate timing mark... with the crank key [and thus the crank] not correctly positioned with respect to the cam.
Put crank at TDC with key more or less in line with #1 cylinder.
photograph the crank and cam sprocket timing marks being in proper alignment.
Put on your best degree wheel & dial indicator, and record all pertinent cam events- opening, centerline ["tops" as you say], and closing, for both I and E valves. Openings and closings can be at various amounts of lift. The ones I have seen are zero lift [hard to detect], 0.006" lift, and 0.050" lift. Any of these will require a dial indicator for any sort of accuracy. It is assumed that you have one and know how to use it, or will get/learn, or turn this job over to a competent advisor. The lobe centerline or max lift is usually pegged by recording the crank position at some small amount less than max lift, on either side, then assuming that the center is halfway between. So, if the lobe max lift is 0.380 then record crank positions at oh say 0.350 lift- one on the way up, and one on the way down. Midway between those positions will be the lobe centerline.
As long as the cam events are happening within a degree or 3 of where they should be [again, I did not see those numbers specified on the cam card], then the cam timing is correct and you should be able to spin the engine and get a strong compression signal. I find a small CORK makes a good pressure detector too though they do tend to fly away and get lost, and/or scare the crap out of you if you forget you corked the spark plug hole and later spin the motor.
Once compression and cam timing is in place, it sounds like you have a good handle on how to set spark timing properly, so it should be no problem to achieve joy then.
May 27th, 2013, 09:49 AM
#68
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Wow, any questions I had bumbling around in my head about the procedure I was planning have just been answered; thank YOU. o.O
The cam card had a second side I forgot to photograph, that's why you don't see very much good info on it. Once I get back to my workshop in a few weeks, I'll take photos of all of it.
I'm getting a dial for measuring bellhousing runout anyway, I assume it works for this too. A primed hydraulic lifter and a unburdened pushrod will do the job, yes?
The cam is a Howard's Cams Hydraulic Flat Tappet 510011-12, verified it by looking at the number on the thing before installing it. http://www.summitracing.com/parts/hr...1-12/overview/ This has different info, but not the degrees of opening or closing. Will have to wait for the rest of the cam card for that.
The cam card had a second side I forgot to photograph, that's why you don't see very much good info on it. Once I get back to my workshop in a few weeks, I'll take photos of all of it.
I'm getting a dial for measuring bellhousing runout anyway, I assume it works for this too. A primed hydraulic lifter and a unburdened pushrod will do the job, yes?
The cam is a Howard's Cams Hydraulic Flat Tappet 510011-12, verified it by looking at the number on the thing before installing it. http://www.summitracing.com/parts/hr...1-12/overview/ This has different info, but not the degrees of opening or closing. Will have to wait for the rest of the cam card for that.
May 28th, 2013, 06:35 PM
#69
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at TDC between EXH and INT strokes, your intake should be just starting to open. It should max out at the Intake Lobe centerline unless I am mistaken, usually round 100-120 crank degrees ATDC, and stay open well past BDC, anywhere from 30-40 degrees up the compression stroke to damn near halfway up [90 degrees BTDC] for really rowdy cams.
Do a compression test before proceeding further. I bet it's very low.
http://www.summitracing.com/parts/hrs-510011-12
has a teensy bit more info on that cam, but no specific opening and closing event positions.... why is this a secret?
This CO brief exchange says it's a "nearly stock cam"
https://classicoldsmobile.com/forums...d.php?p=381180
Yep, a dial indicator will do nicely for cam lobe lift assessment. Typically they come with a magnetic base and 2 arms so you can find a favorable position for the shaft. Ahem. You will still need a degree wheel for the crank position readings. They are not too expensive but the wait for delivery might bother you, and they usually DO NOT fit the 3/4" Olds crank snout bolt in my experience, so you have to modify to suit. Any stiff wire can make a suitable pointer for the degree wheel.
I see your cam lobe lift is on the order of 0.280-0.295", so at 0.260" might be a good place to take crank readings to determine intake lobe centerline location. Sometimes on the way down you have to force the lifter to follow the cam, because the dial indicator alone won't do it. I have used lifters galore so I tend to use a spare lifter, dismantled, cleaned, and then assembled with e.g. cyanoacrylate [Krazy] glue to form a solid lifter, to avoid any plunger motion.
Last edited by Octania; May 28th, 2013 at 06:51 PM.
May 28th, 2013, 06:48 PM
#70
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Well, there's your problem...
at TDC between EXH and INT strokes, your intake should be just starting to open. It should max out at the Intake Lobe centerline unless I am mistaken, usually round 100-120 crank degrees ATDC, and stay open well past BDC, anywhere from 30-40 degrees up the compression stroke to damn near halfway up [90 degrees BTDC] for really rowdy cams.
at TDC between EXH and INT strokes, your intake should be just starting to open. It should max out at the Intake Lobe centerline unless I am mistaken, usually round 100-120 crank degrees ATDC, and stay open well past BDC, anywhere from 30-40 degrees up the compression stroke to damn near halfway up [90 degrees BTDC] for really rowdy cams.
I don't see any 0.050" checking numbers there (maybe the other half of the card), but it sure looks like the intake peak should be around 110° ATDC (80° BBDC), and not where it is.
Now, 110°ATDC is darned close to being the mirror image of the 12° BTDC that you observed, which, if I'm not mistaken, would point to you being 180° out in your measurements, so I'd want to be absolutely sure of your exhaust and power strokes.
Now, 110°ATDC is darned close to being the mirror image of the 12° BTDC that you observed, which, if I'm not mistaken, would point to you being 180° out in your measurements, so I'd want to be absolutely sure of your exhaust and power strokes.
- Eric
May 28th, 2013, 10:08 PM
#71
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Compression test showed 110 PSI to 135 PSI, some cylinders had a lot more oil than others.
How well will the printed cardboard degree wheel serve me?
I can certainly take a seized lifter and use that instead.
Eric; I just re-read what you said, and you're talking about the crank being 180 out, which means 90 degrees on the cam. Now it makes sense. I was forgetting that the crank moves 720 degrees during the duration of the four strokes.
How well will the printed cardboard degree wheel serve me?
I can certainly take a seized lifter and use that instead.
Eric; I just re-read what you said, and you're talking about the crank being 180 out, which means 90 degrees on the cam. Now it makes sense. I was forgetting that the crank moves 720 degrees during the duration of the four strokes.
June 9th, 2013, 01:32 PM
#73
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Gentlemen.
e2PVVgx.jpg
I will be tearing the engine apart again Tuesday, and checking everything I can.
e2PVVgx.jpg
I will be tearing the engine apart again Tuesday, and checking everything I can.
June 11th, 2013, 11:36 AM
#74
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I feel dumb. My crank gear has TWO marks, as shown in the first picture - and as shown in the second, I aligned the cam to the wrong mark. -.-
lQE59K0.jpg
gVMjljo.jpg
This error has been rectified, verified TDC on #1, so it should be good now. Checking the engine over one last time (just to see if I missed something) before buttoning it up once again.
lQE59K0.jpg
gVMjljo.jpg
This error has been rectified, verified TDC on #1, so it should be good now. Checking the engine over one last time (just to see if I missed something) before buttoning it up once again.
June 11th, 2013, 11:42 AM
#75
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Ah HA. Off about as much as I suspected (I ASSume those are "before" pictures, with the cam mark at the 8:45 positon at TDC).
Be sure to take pictures before you put it back together, so you convince yourself it's right, in case you have second thoughts.
You'll be happier now.
- Eric
Be sure to take pictures before you put it back together, so you convince yourself it's right, in case you have second thoughts.
You'll be happier now.
- Eric
