Hey guys! I am finishing up my restoration of a 72 GT. Engine rebuilt, new everything. Sadly it is running poorly. It acts like it has weak spark. Runs fine until I give it heavy throttle. I am only getting 11.5 v at the + coil terminal(batt voltage 13v). Is this normal? I know it is fed by a resistor wire from the fuse block but this seems a little weak. All ignition components are new and has a new weber. I did find a bad float needle valve but it has been replaced. Any suggestions?
Voltage to coil
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Well, pretty much. I did replace pistons with flat tops @ .040 over. Replaced the cam with a slight upgrade, nothing radicle. The ignition is stock with new points, coil, cap & rotor and wires.
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A while back I baught a new set of spark plug wires listed at the auto parts store for my Opel GT, my spark was weak, they all measured 30k ohms resistance. The FSM states no more than 10k ohms. The car ran like a dog with those, I returned them immediately.
Most people here on the forum replace the stock ignition with the Pertronix electronic conversion. I just installed the Pertronix 2 with the .6 ohm resistive Flame Thrower coil after running the Crane XR700 for years which utilizes the original stock coil & resistance wire. I can assure you that spark is no longer an issue, in fact some of the intermittent low idle problems have disappeared.
Most people here on the forum replace the stock ignition with the Pertronix electronic conversion. I just installed the Pertronix 2 with the .6 ohm resistive Flame Thrower coil after running the Crane XR700 for years which utilizes the original stock coil & resistance wire. I can assure you that spark is no longer an issue, in fact some of the intermittent low idle problems have disappeared.
I have checked the resistance of the plug wires, all are way below 10k ohms. I have a new coil from Opel GT Source, not the stock one. My real question is about the 11.5 volts feeding the coil while running and if that is normal. I am using the original resistor wire to feed it and am not sure if there is not too much resistance.
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Yes, that is "normal" coil supply voltage, and perhaps a bit higher than usual. When the engine is stopped and the ignition turned on, the coil supply voltage may actually be quite close to battery voltage, since the coil current is very low. At high rpm and under load, when the coil current is higher, the supply voltage can be as low as 9 volts.
IIRC, the OEM resistor wire has approximately 3 ohms resistance. Ohm's Law (V=IR, or Voltage equals Current times Amps) suggests that 9 volts and 3 ohms happens at 3 amps coil supply current. Or thereabouts...
I believe that your issue isn't likely the resistor wire. It might be a bad spark plug, or a defective spark plug wire(s), or bad points, or a bad coil. Or it might have nothing to do with the ignition system. What makes you believe the issue is weak spark?
Thanks for your quick responses! I got it idling ok and it seems to run fine under light throttle but heavy accel makes it really start to miss. I have double checked the whole ignition set. Like I said, it's all new. So is the carb although it was running very rich and when I checked the float adjustment I found the needle defective. I have replaced the needle and seat and believe I have the float set correctly. It is a Redline Weber set up so I am assuming the jets are correct. I have not adjusted the lifters while running and have read that could be a problem but that makes no sense to me. I spent the last 25 years in the auto repair biz but haven't dealt with this old school stuff since high school, lol. I have never had to adjust hydraulic lifters while running. The lifters are new also by the way.
Hey, thanks for any advise you can give this old fart.
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Have you checked the initial (aka "static") timing, as well as vacuum and mechanical (aka "centrifugal") advance?
Static timing, with the vacuum advance and retard hoses disconnected and plugged, should be at TDC, or up to 5 degrees advanced. That is checked and set using the flywheel ball and block pointer, tucked way back behind the exhaust manifold. To check timing advance, you need an adjustable timing light. Not everyone has one, but it is, in MNSHO, essential to maintain these cars.. At 3500 rpm, the timing should have advanced to ~36 degrees BTDC. If not, I suspect the mechanical advance mechanism is stuck. Simple check: remove the distributor cap, and gently rotate the rotor counter-clockwise. If it doesn't rotate about 10 degrees then "spring" back, the advance is stuck.
Ahh, There is not a chance that Redline send you a Weber properly jetted. Might be close, but it is impossible to properly jet a carb "out of the box". I assume it is a 32/36 DGEV?
What is the float set to (mm closed and hung open), and what are the jets (main and idle), what is the mixture set to (# of turns from full-in), and what air corrector and emulsion tubes are in the carb?
Proper jetting requires either a wide-band Air/Fuel/Ratio meter (such as an AEM), or using spark plug colour and seat of the pants engine operation, with an assortment of jets to check what works best.
That is an old wives tale that Opel CIH hydraulic lifters need to be set with the engine running. Same as pretty much any Chevy small block. Piston at firing TDC, loosen rocker nut so rocker arm rattles, then tighten to remove rattle, then tighten an additional 3/4 to one turn
No worries, that is why us old farts belong to this site.
Is this the coil purchased from OPGTS?
Edit:
Higher quality OEM Bosch high-output ignition coil. Provides best reliability and durability. Features calibrated output for original-style Opel ignition systems, with correct impedance and proper voltage range to prevent arching within cap.
I trust OPGTS instructions provided with their parts. Wondering if OPGTS suggusts keeping factory resistor wire with this coil if using ignition points.
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Edit:
Higher quality OEM Bosch high-output ignition coil. Provides best reliability and durability. Features calibrated output for original-style Opel ignition systems, with correct impedance and proper voltage range to prevent arching within cap.
I trust OPGTS instructions provided with their parts. Wondering if OPGTS suggusts keeping factory resistor wire with this coil if using ignition points.
That's exactly the way I adjusted the lifters. The float is set basically level, perhaps I should have followed the measurements ( I don't have a metric ruler/scale ) I have no clue what jets and all are in it as I assumed it would be close enough out of the box to at least run fairly correct as it was sold as a bolt on kit for the 1.9 engine. I will have to rely on spk plug color for mixture clues. They were very carboned up until I replaced the needle valve. They have since been cleaned so I will spin around the block a few more times and go from there. Looks like the top of the carb will be coming off again and I will order a tuner kit for it. Yes, it's a Weber 32/36. I am fairly certain it is a carb problem Thanks!!
That was the first one I got. It would barely spark so They sent an other brand High output. The thing starts right up so I'm probably ok there. Why do you ask?
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A bad condenser will give the symptoms described.
It is brand new but I will test it. Thanks.
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So will a broken ground on your points plate in the distributor. Or a bad ground to the block.
OK, thanks.
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Usually in my experience the problems are on either side of the engine distributor or carburetor not the engine itself. Try dropping a 160 air corrector in the primary main, before you buy one of those jetting kits. See where that gets you. The 170 air corrector is a bit too lean in my experience.
Now if your problems start when you get 2/3 of the way down on the throttle it’s probably a common malfunction of the secondary enrichment circuit, not dependable on the 32/36. Stepping up your secondary main jet anywhere from a 145-170 with the option of blanking off that enrichment circuit is what I’ve done. You can step up your secondary main jet without worrying about the enrichment circuit yet for starters. I had a 32/36 where the enrichment circuit worked just beautifully with the factory jetted 50-140/160 secondary and other brand new ones that ran too lean, near 15:1. I do have the air fuel ratio set up and saw exactly what was happening. They are a great tool, but as I understand not for everyones desire.
Where the plastic float should be is subject for debate. I use the brass float on my 32/36 set at 41/51mm to the bottom of the float and avoid any controversy. The plastic float which you probably have as I understand is set at close to the same height, 40/50, 41/51 take your pick whichever works best (measured with gasket). If you call Redline they will tell you to set the plastic one about the same or lower 17/28mm measuring the top of the float to the lid including gasket. All measurements are done holding the cover vertically with the fulcrum pin at the top.
There are those who set up the plastic float old school at 35/50mm, I’ve done a good bit of research and as I understand it, the original "Weber" in Spain Promex, then LCN, has changed the float a few times from brass, to plastic, to the smaller DFV plastic float. That’s the explanation as I’ve read as to why the float height was updated and changed years ago.
Most all factory jetted 32/36 Weber’s (and this is probably what you have) have been set up for years as this chart describes
Just a couple of suggestions HTH
Now if your problems start when you get 2/3 of the way down on the throttle it’s probably a common malfunction of the secondary enrichment circuit, not dependable on the 32/36. Stepping up your secondary main jet anywhere from a 145-170 with the option of blanking off that enrichment circuit is what I’ve done. You can step up your secondary main jet without worrying about the enrichment circuit yet for starters. I had a 32/36 where the enrichment circuit worked just beautifully with the factory jetted 50-140/160 secondary and other brand new ones that ran too lean, near 15:1. I do have the air fuel ratio set up and saw exactly what was happening. They are a great tool, but as I understand not for everyones desire.
Where the plastic float should be is subject for debate. I use the brass float on my 32/36 set at 41/51mm to the bottom of the float and avoid any controversy. The plastic float which you probably have as I understand is set at close to the same height, 40/50, 41/51 take your pick whichever works best (measured with gasket). If you call Redline they will tell you to set the plastic one about the same or lower 17/28mm measuring the top of the float to the lid including gasket. All measurements are done holding the cover vertically with the fulcrum pin at the top.
There are those who set up the plastic float old school at 35/50mm, I’ve done a good bit of research and as I understand it, the original "Weber" in Spain Promex, then LCN, has changed the float a few times from brass, to plastic, to the smaller DFV plastic float. That’s the explanation as I’ve read as to why the float height was updated and changed years ago.
Most all factory jetted 32/36 Weber’s (and this is probably what you have) have been set up for years as this chart describes
Just a couple of suggestions HTH
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I ran an un-properly jetted Weber for 20 years and 225,000 miles and it worked fine.
If it was my car and it ran good at idle and funky under higher rpms, I would immediately reach for the dizzy and tweak it one direction or the other to try to fix it. Under higher rpms mechanical advance kicks in, you might be a tad too far advanced.
Rotating the dizzy counterclock-wise retards the spark. The tiniest pubic hair of movement can make a huge difference.
Vacuum leaks are the bane of these engines, also. Use a spray can of electrical contact or carb cleaner and spray around the carb and manifold joinings, also the brake booster hose, and listen for any change in the engine running. ANY change means you have a leak.
If it was my car and it ran good at idle and funky under higher rpms, I would immediately reach for the dizzy and tweak it one direction or the other to try to fix it. Under higher rpms mechanical advance kicks in, you might be a tad too far advanced.
Rotating the dizzy counterclock-wise retards the spark. The tiniest pubic hair of movement can make a huge difference.
Vacuum leaks are the bane of these engines, also. Use a spray can of electrical contact or carb cleaner and spray around the carb and manifold joinings, also the brake booster hose, and listen for any change in the engine running. ANY change means you have a leak.
Thanks for the info!
The condenser tests OK. I found my Father's old dwell meter and just can't seem to get the points to set right and the deviation when reving engine has made me opt to install electronic ignition. That just may be the ticket.
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