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Discussion Starter · #23 ·
What vehicle, so we know what/how the wire routing and circuits are laid out??

you mentioned condenser....is it a points distributor??
It's an 85 GMC c2500. When I took the original engine out, I took pictures of most of the wiring and so just rewired everything the same. I Think that is all set up correctly?
It's a GM style HEI distributor with the ignition coil sitting on top of distributor cap, I'm not sure if that is a points distributor? (Sorry my knowledge is limited on these). Like I said I replaced the distributor cap ignition coil and rotor but the distributor shaft that meshes with the camshaft is from the original engine. When I took it off the engine before, I left it in the garage so figured it would be reusable, but the circuits around the rotor (what I thought was called a condenser) do look a little rough, so that's why I was thinking maybe those might be the issue.
 

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HEI does not use points. A condenser is a tubular gadget with a wire coming out on it, it is also called a capacitor. These are used to smooth voltage wave forms by absorbing peaks and filling in valleys. These are typically used with points to suppress sparking a rory the contacts which causes metal erosion from one contact and deposition on the opposing contact as well as not allowing a sharp voltage cut off as the points open which reduces coil output high voltage by slowing if not stopping the collapse of the primary magnetic field winding resulting in low to no secondary coil high voltage being generated. In HEI this switching is being done by a power transistor so there is no spark and arc going on but still what could be described as sloppy or surging voltages are created but these are managed by a miniaturized capacitor inside the module. I have to apologize as when I here the word condenser or capacitor my brain connects that with points as with electronic ignitions these devices are seldom seen. They can be externally mounted on electronic distributors from time to time to suppress electrical noise from entering the battery power lines these often referred to as B+ wiring or primary wiring.

The HEI carries the coil in the cap, this is surrounded by terminals that on the outside connect the spark plug wires while on the inside have a bare metal lug usually made of brass. In the center is the rotor. It takes the high voltage coil output and directs it to the appropriate lug in cylinder firing order. On the Chevrolet the rotor turns clockwise as does the crankshaft. Not everybody does it this direction so this isn’t a general rule of engines across the worlds manufacturers.

The rotor in the Chevy HEI also covers the mechanical spark advance system that mounts to the top of the rotating shaft that is gear driven by the camshaft. The advance is actually a concentric short shaft device that rides on the cam driven shaft and is connected to the driven shaft by springs and counter weights to where the stub shaft can be advanced in position or that advance removed compared to the driven shaft as the driven shafts rotation speed thus engine RPM changes. The base of the concentric shaft has a tooth pattern that looks a lot like a gear. This gear is often called a reluctor but that term while used generally for engineers would refer to only a specific type module which I’ll skip over as this is confusing enough. The module has a magnetic sensor that reads the passing teeth of the ‘reluctor’ each passing tooth affects a magnetic disturbance in the sensor. This is read by a micro amplifier in the module which interrupts the B+ voltage flow through the power transistor as it passes from the negative side of the coil to ground. Note points do the same thing mechanically operated by a small cam inside their distributor. So here in HEI the power transistor is shut off the primary magnetic field in the coil collapses which forces the secondary winding to produce a high voltage which passes through the center terminal of the rotor out along its arm conductor to the lug terminal it is aimed at of the cap. The next step is that terminal is wired to the appropriate spark plug in the firing order.

All 4 cycles engines use 720 degrees of crankshaft rotation to fire every cylinder, so an eight cylinder engine has a cylinder firing every 90 degrees. In the 720 degree cycle the timing marks on the damper pass the static TDC point twice, For the Chevrolet this has cylinder number 1 and cylinder number 6 crossing the TDC marks every full cycle. Depending on how the manufacturer numbers cylinders and describes its firing order there is a passage of the prime cylinder designated as number one and its opposite in every 720 degree cycle.

Note the cam and distributor turn at 1/2 crankshaft speed or 360 degrees for every 720 degrees of crankshaft rotation.

Because the timing marks cross TDC twice in a full crankshaft cycle it is easy to install the distributor on a Chevy or Ford what is described as 180 degrees out of time. This is harder to do on Chrysler engines as they use a one way shape on their drive system to reduce the chances of getting this wrong.

The additional problem is where the driven gear is part of the distributor as it is removed from engagement from the cam’s driving gear you get a rotation that moves the oil pump drive such that the when the distributor is reinstalled to the alignment marks you made before removal the pump drive is misaligned and the distributor will not drop to its seat. The trick with the Chevy is to set the distributor in with the housing and rotor align with your initial position marks and very lightly apply a tiny bit of force on it with its retainer clamp and bolt. here you just don’t want the housing to rotate as you turn the crankshaft, so this doesn’t take more than finger tight pressure. Then you rotate the crank which will rotate the distributor shaft, when the distributor drops onto its seat the ignition is timed to where it was before you took it apart.

A lot to read and grasp but if you don’t get your arms around this concept of how the Chevy distributor works you’ll find yourself in a fight with this thing every time you have the distributor out. Additionally something to look for in the set up is when it’s in the factory position the vacuum advance can points at the number 6 cylinder and the rotor at number 1. However in reality no matter what housing alignment you have regardless of which cap terminal the rotor is pointing at you can wire for number 1 there and go around the firing order from there. The possible problem is you might have physical conflicts with the vacuum advance can and the intake manifold. If you’re 180 out you can just start number 1 cylinder in the number 6 distributor terminal and wire the firing order in the clockwise direction from there, not like I never have done this.

Bogie
 

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Discussion Starter · #25 ·
Hey guys,

Checked spark plugs, they all look good :( I also double checked any plugged holes into the intake manifold, so I think we can rule out extra air getting in.. will flip the distributor 180 tomorrow just to see and also advance/retard ignition timing again, but I'm thinking that the internal cam/crank timing must be off. When I try to turn it on it's still backfiring gas out of the carb and has combusted it a few times. Its a 3 keyhole crank sprocket and I'm preeettyyyy positive I put it on the key on the standard timing alignment and aligned the two circles properly, but maybe not? Or the timing chain slipped? Like I said im kind of at a loss, about to start searching for a mobile mechanic...
 

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Hey guys,

Checked spark plugs, they all look good :( I also double checked any plugged holes into the intake manifold, so I think we can rule out extra air getting in.. will flip the distributor 180 tomorrow just to see and also advance/retard ignition timing again, but I'm thinking that the internal cam/crank timing must be off. When I try to turn it on it's still backfiring gas out of the carb and has combusted it a few times. Its a 3 keyhole crank sprocket and I'm preeettyyyy positive I put it on the key on the standard timing alignment and aligned the two circles properly, but maybe not? Or the timing chain slipped? Like I said im kind of at a loss, about to start searching for a mobile mechanic...
The three groove gear really isn’t enough to mess the engine up as much as you seem to have on your hands. This is just a tuning adjustment that moves the cam a little to favor more mid range torque through the factory standard position to a position that favors top end horsepower. The changes are rather subtle almost mot enough to perceive without a dyno as it’s more a global shift of the torque and power curves around a fixed reference point, that being the factory position.

An easier way to test for 180 out is just pull the plug wires and start with number 1 into the number 6 terminal, then in the clockwise direction wire the firing order from there. Then test this way you don’t introduce the funky distributor gear rotation pulling the oil pump shaft so the distributor is almost guaranteed to go back in off another tooth. There are 12 teeth on the distributor gear that’s a 30 degree per cam revolution and 60 degrees crank since the crank rotates twice to once of the cam. So a tooth off is a way bigger deal than often appreciated.

Always get your positions of distributor housing marked to intake, rotor to housing and the cap position to the rotor marked before you undertake distributor removal.

The factory distributor position is with the rotor pointing at the number 1 cylinder with the vacuum advance can pointing at number 6. This aligns the rotor to the housing and the housing to the block this with the crank at TDC firing number one. The catch-22 in this is cylinder number 6 is half way through the firing order so it is 1 complete crank rotation after number 1 so again the timing marks align with the pointer. So you have to be sure where the crank is thus the cam in this relationship. The quick and dirty way is a finger in the number 1 spark plug hole feeling for compression, another way is pop the left side (from the driver’s sitting behind the wheel perspective) rocker cover to watch the valves cycle. When both are closed on number 1 the timing marks should be approaching if not at the pointer. Number 6 at this time would be finishing exhausting and starting intake if you had both sides rocker covers off you would see this with the exhaust closing and the intake starting to open, needless to say if number 6 had a spark put to it at this time you would get a really big bang from the intake.

Bogie
 

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Discussion Starter · #27 · (Edited)
Sure I can try this. The only thing is, when I set the valves before, I set them when each piston was at tdc compression(which I found by watching the valve movement and waiting until the exhaust just opened, and then backing up to tdc). so if it's somehow 180 off, doesn't that mean I actually set them at tdc exhaust? So just flipping the distributor wouldn't really solve the issue since the valves aren't properly set? I probably should have just done the EOIC adjustment method...
 

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I’m guessing that these are hydraulic lifters.

All your doing with the preload is setting where the inner plunger calls home.

Most lifter specs are 1/2 turn beyond zero clearance that you find by rotating the push rod. Figure that if your rocker stud is a fine 3/8ths thread that is 24 threads to the inch which is .04167 inch of vertical movement per full turn. So half a turn is moving the inner plunger .020835 inch which is roughly half a millimeter.

This is nothing more than a place along the length of travel the plunger has between being bottomed in its bore or against the retainer at the top of its bore.

For a pumped up lifter when you tighten it it will hold the valve off its seat by the distance in number of turns you made on the adjustment nut until the oil trapped in the bottom chamber under (not in) the plunger is bled off by the pressure of the valve spring. This will continue till the spring seats the valve. There is no more magic to this, this is not the same as setting lash on a solid lifter cam. Its not even really setting a preload, it is setting a closed valve running position for the plunger in the lifter’s inside bore.

I like to just go through the firing order simply because the engine I build tend to rather rusty cam timing so when you use these flat rate shop processes you can get into trouble with these long duration cams. So I start with cylinder number 1 at TDC firing, this has both valves closed. Then rotate the crank 90 degrees clockwise as you face the front of the engine. This is the next cylinder in the firing order adjusting that cylinders valves then repeat you way through the firing order in 90 degree increments till your back at number one which will be 2 full turns of the crankshaft. If you have a decent damper it will have 90 degree marks beyond the TDC mark if you don’t have a marked damper you will find the Proform Harmonic Balancer cover to be a useful device, they run about 30 bucks. I never had any luck keeping timing tapes on the damper for very long so I just don’t bother with them.

Again you need to allow time for the lifters to bleed down till the valve gets seated. The pressure testing you did a while back only tells you the lifter hasn’t bleed down. Really once you get a feel for this you don’t need to wait for the recently adjusted lifers to bleed down. Once you have the lifters for the cylinder of interest on the heel of the lobes for that cylinder all you need do is loosen the current adjustment then come back and tighten the nut while rolling the push rod between thumb and forefinger till it resists your turning. Note where your wrench is and add half a turn, move on to the next valve or on to the next cylinder in the firing order, rinse and repeat till your back to number one.

Lifters can be slow to let down when the engine isn’t running, their internal metering is dynamic as they're raised and lowered at engine speeds so don’t expect fast bleeds when the engine isn’t running simply because if they all bled down you’d have a lot of valve train clatter on start up. Basically you just need to get a couple three cylinder to fire off the starter to get things going, if your timed correctly close and it fires the lifters correct to their preset adjustment very quickly on those cylinders that had valves hanging open and bleed down while sitting.

Bogie
 

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Can you take a picture of the installed distributor and carburetor? Are they original to the truck?

An 85 C20 should have a stock large cap HEI , which would not have an external coil. There might be a small external condenser that is used to filter ignition noise, but the truck will run without it. Most of the high GVW trucks also have simple emissions, with a very conventional Quadrajet without any electric connections,
 

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Discussion Starter · #30 ·
Again you need to allow time for the lifters to bleed down till the valve gets seated. The pressure testing you did a while back only tells you the lifter hasn’t bleed down. Really once you get a feel for this you don’t need to wait for the recently adjusted lifers to bleed down. Once you have the lifters for the cylinder of interest on the heel of the lobes for that cylinder all you need do is loosen the current adjustment then come back and tighten the nut while rolling the push rod between thumb and forefinger till it resists your turning. Note where your wrench is and add half a turn, move on to the next valve or on to the next cylinder in the firing order, rinse and repeat till your back to number one.

Bogie
Hey Bogie this is originally what I had done to set the valves with no oil in the lifters I had twirled the pushrod between my fingers until it wouldn't twist anymore, and then gone 3/4 of a turn more and rotated the engine 90 degrees and checked for any loose ones. When I had read about this method it had said you shouldn't need to go more than 2 full engine rotations (4 crankshaft turns) but I had gone around 4 and was still getting semi loose pushrods, so that's why when all this first started I figured I did that method wrong and switched to adjusting lifters when the piston is at tdc.

This is what everything looks like. New 650cfm carb from AutoZone and the distributor is new rotor and cap but original housing.

Motor vehicle Vehicle Car Automotive exterior Gas
 

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Your just getting a starting point, if there is no oil in the lifter there is nothing to hold the position you set except a soft spring inside the lifter so rotating the engine will relocate the plunger, that doesn’t matter as the engine fires up and oil pressure is established the plunger will close the distance back to your ‘preload’ position. The plunger has about .150 inch of travel in its bore between sitting at its deepest which rides on a machined ridge to the top where it is against a retainer, well actually the push rod cup hits the retainer it is a separate piece that caps the plunger.

You can set the ‘preload’ anywhere in the travel length of the plunger an it will hold that position once the cavity under the plunger fills with oil. This simply is oil pressure fills the reservoir inside the plunger which opens lightly spring loaded inertia valve mounted to the outside bottom of the plunger. It admits oil to cause the plunger to raise till gap are closed and resistance from the valve spring holding the valve on its seat is encountered. At that point the valve closes and traps the oil in the cavity. Motion of the lifter wants to shuttle the valve open to closed when pump up occurs this shuttle effect when the preload position is exceeded allows the valve to open to bleed the excess oil out and reestablish the preload position, but this is a little ahead of the story.

Engine oil pressure flows into the cavity as the plunger moves up removing any lash until the resistance of the valve spring with the valve on its seat stops any further movement. At this point the light spring under the inertia valve closes it and the oil trapped in the cavity hydraulically locks the plunger to the lifter body.

That’s it; wherever you set the plunger in it’s permissible range of travel it will stay there because engine oil pressure cannot overcome valve spring pressure holding the valve closed on its seat.

The only thing the lifter can do once this initial adjustment is set is to close any gaps that develop in the linkage between lifter and valve stem. Pump-up occurs when the valve spring looses control of the valve. When this happens the valve is bouncing on its seat because the spring has lost control of the masses of the valve train parts or the spring has gone into surge where it’s natural harmonic frequency is exciting it to bounce uncontrollably. If these things happen and they are typically a function of over-revving the springs abilities then gaps appear in the valve train linkage to which the plunger will move up to close. When the set preload dimension away as plunger movement upward is enough to keep the valve from seating the cylinder looses compression the power drops off. This is the pump-up event, it lasts till the lifters bleed off the excess oil that raised the plunger allowing the original preload setting to reestablish itself.

On the other side of the coin are lifters that tick. This at start up is open valve spring pressure forcing oil out of the bottom cavity either through a leaky inertia valve and/or around the plunger. Some racing lifters do this as they are designed with built in cavity leakage to prevent pump up or speed recover from such events. A lifter that ticks all the time is leaking oil past the inertia valve or around the plunger faster than the lubrication system can keep the cavity filled.

I’m going to stop here as this is a lot to absorb. There are tricks for racing that are done but I think the details will conflict with getting to a basic understanding of how hydraulics work.

Here’s a link to a cut away view, it‘s for a VW lifter but they all basically are the same functionally with some detail part differences like the picture calls the inertia valve a check valve which is its function, they also show it as a ball valve but often this is a flat spring loaded disk. At the top the side push rod oil groove on American designs is simply a metering hole into the plunger’s reservoir which might have a metering restrictor.


Bogie
 

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Hey Bogie this is originally what I had done to set the valves with no oil in the lifters I had twirled the pushrod between my fingers until it wouldn't twist anymore, and then gone 3/4 of a turn more and rotated the engine 90 degrees and checked for any loose ones. When I had read about this method it had said you shouldn't need to go more than 2 full engine rotations (4 crankshaft turns) but I had gone around 4 and was still getting semi loose pushrods, so that's why when all this first started I figured I did that method wrong and switched to adjusting lifters when the piston is at tdc.

This is what everything looks like. New 650cfm carb from AutoZone and the distributor is new rotor and cap but original housing.

I think you have your valves to tight, when spinning the push rods in your fingers until tight you are pushing the plunger down in the lifter bore and don't even know it, if you are tightening the rocker nut until you can't turn it anymore you have tightened it to much, you should still be able to turn the push rod with your fingers at zero lash. How to adjust your valves. loosen up all your valves turn the engine till you have compression on #1 cylinder. Once you have it on TDC, you adjust the following valves #1,3,4,8, exhaust & #1,2,5,7, inlet. Then you turn the motor over once back to the timing mark, you are now firing on #6. You adjust #2,5,6,7, exhaust & #3,4,6,8, intake. Done. When adjusting the valves i use the up and down method with your fingers on the push rod just slightly raise the rod up and down until no more up and down you should still be able to twist the push rod, at this point tighten the rocker nut 1/2 turn only.
 

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Hey Bogie this is originally what I had done to set the valves with no oil in the lifters I had twirled the pushrod between my fingers until it wouldn't twist anymore, and then gone 3/4 of a turn more and rotated the engine 90 degrees and checked for any loose ones. When I had read about this method it had said you shouldn't need to go more than 2 full engine rotations (4 crankshaft turns) but I had gone around 4 and was still getting semi loose pushrods, so that's why when all this first started I figured I did that method wrong and switched to adjusting lifters when the piston is at tdc.

This is what everything looks like. New 650cfm carb from AutoZone and the distributor is new rotor and cap but original housing.

View attachment 623611
I think you have your valves to tight, when spinning the push rods in your fingers until tight you are pushing the plunger down in the lifter bore and don't even know it, if you are tightening the rocker nut until you can't turn it anymore you have tightened it to much, you should still be able to turn the push rod with your fingers at zero lash. How to adjust your valves. loosen up all your valves turn the engine till you have compression on #1 cylinder. Once you have it on TDC, you adjust the following valves #1,3,4,8, exhaust & #1,2,5,7, inlet. Then you turn the motor over once back to the timing mark, you are now firing on #6. You adjust #2,5,6,7, exhaust & #3,4,6,8, intake. Done. When adjusting the valves i use the up and down method with your fingers on the push rod just slightly raise the rod up and down until no more up and down you should still be able to twist the push rod, at this point tighten the rocker nut 1/2 turn only.
 

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Discussion Starter · #34 ·
Hey Jay,

Yeah what I was saying is what I had done originally, what I changed after is as you are saying I moved the pushrod up/down as I tightened it until no up/down movement (with the piston at tdc compression) and then went 1/2 turn more. Still getting backfire out of the carb, so I'm thinking it must be off a tooth or two. Going to open up the timing cover and take a look today, I'll let everyone know what I find.
 

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Hey Jay,

Yeah what I was saying is what I had done originally, what I changed after is as you are saying I moved the pushrod up/down as I tightened it until no up/down movement (with the piston at tdc compression) and then went 1/2 turn more. Still getting backfire out of the carb, so I'm thinking it must be off a tooth or two. Going to open up the timing cover and take a look today, I'll let everyone know what I find.
I,m Sure you also triple checked your plug wires?
 

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Discussion Starter · #36 ·
Yup about 4-5 times now. I flipped the cables on the distributor (put 1 in the 6 position and followed gm order) and still getting flame out of the carb. Going to pull the timing cover and see what's up
 

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Discussion Starter · #37 · (Edited)
OK, cam/crank timing is correct. So am I still messing up setting the valves? I loosened them all the way and then tightened until there was no up/down movement of the pushrod(being careful to make sure I wasn't pushing it down with
my wrench) and then went half a turn more. I'm not sure if there is oil in the lifters, but even if there is it should be ok because as everyone's stated on this thread its incompressible and should eventually bleed out, correct? Also, is it correct to use the timing mark I made with the piston stop on the damper to set tdc, or should I use the notch on the damper?
 

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Another trick you can do and is about bullet proof is besides moving the pushrod up and down, is to lift up the end of the rocker arm tip up and down off the valve stem tip before you find zero lash and slowly tighten the rocker arm nut down while being careful not to be pushing pressure on it so too give a false reading if your using stock stamped rocker arms but if your using a poly lock type rocker arm then its a lot easier as you can just turn the poly lock with your fingers.

I have it loose to where I can move the rocker arm off the valve tip and I start to tighten the poly lock nut or in case a stock type rocker arm not I will tighten it slowly until I can't move the rocker arm no longer off the valve tip and then I check the pushrod to see if it will move up and down. I don't bother the spin method as it throws you off way to easy especially if your new to this sort of thing. I will go back and forth checking the pushrod up and down movement and also the lifting the rocker arm tip up and down until I have no lifting on the rocker arm tip.

After that I verify by backing the nut or poly lock just enough to start to get a hair lift on the rocker arm tip and then check the pushrod up and down. I then will tighten it back up just enough to get back to where the rocker arm tip won't go up or down off the valve stem and recheck the pushrod and then give it what ever turn past zero lash the camshaft company calls for on there lifters. I have done it this way for over ten years now and never have had it fail me and its always been spot on. I tried the spin method the first few times I did it and thought I had it correct but did not.

I had that trick shown to me and have never failed it since.
 
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