Thank you Herr Schlizaugen! Schnappen der heels! It happens quite a lot while setting up spark and mixture on modified engines too. Once the mixture is evened out the spark advance figures can be quite a lot compared to std stuff. Blowby as well while mixures are set then spark advanced disappears when cylinder pressures are where they need to be.
Ignition Modules
- Thread starter Steve K
- Start date
The basic Pertronix units and similar are excellent because they totally take away the dizzy shaft lobe wear element. Worn bushings might still have an impact though.
Hi.
Perception is reality. So if both you and your customer are happy then that is all that matters.
For the record I am still not convinced about cause and effect, but I am not going to comment further.
Welcome to the forum Sj B.
Cheers.
Perception is reality. So if both you and your customer are happy then that is all that matters.
For the record I am still not convinced about cause and effect, but I am not going to comment further.
Welcome to the forum Sj B.
Cheers.
Comment is what forums are for.
And worn centrifugal advance pivot bushes...
Hi @Whippet, I see this ignition thread has sparked a bit of conjecture as to how could improved ignition reduce oil consumption which reminded me of similar anecdotes. In discussions over a few pints of excellent Hook Norton ale I was educated that piston rings don’t seal by spring pressure against the walls but by the actual combustion pressure forcing the ring outward and downward as per Fig 1.9.2
It’s my conjecture that the uneven lobes Sj B observed resulted in variations in how much (if at all) the points actually opened for each cylinder which would vary the dwell time the coil would have to charge up or to even spark leading to some cylinders fouling plugs. Add a few decades of wear and the rings if taken off the pistons would likely fall out of the bore, which leads to the next conjecture that the fouled plug resulted in minimal combustion pressure insufficient to push the rings against the bore wall allowing a minute film of oil to remain on the walls.
Sj B also mentioned some cylinders were detonating and my colleagues reckoned that the block ‘ringing’ could also induce Fig 1.9.5 increasing the blowby and also leaving minute amounts of oil on the walls. As per the aged Repco service manual below, 1/10 of a drop of oil would equate to 12 gallons per 100 miles so making the ignition work for all cylinders could indeed be the causation for the observed reduction in oil smoke and consumption.
Cheers
AlexB
Ah, my long-standing best reference book! I've always been amazed by piston rings and their effective manufacturing.
Hi AlexB.
I also have a copy of the Repco reference that you cite from my apprentice days. As you know I prefer objective information against subjective, so I am pleased that you use reference publications to inform and support your comments, which is so uncommon these days.
I agree that worn Kettering points based distributors cause variations relative to other cylinders for consistent ignition timing. I also agree that correct mechanical advance curves are important to maximise engine power output, which are the points Sj B made in the above posts.
I agree with everything in post #54 except the last sentence. The part I don't understand or accept is the stated cause / effect of the oil burning, which is what I mentioned in post #58. I still don't understand how improved accuracy in ignition advance and relative timing between cylinders explains this statement from post #59: "We did oil every 1000km, Pen HPR mineral. She stopped oil smoke and burning oil within the first 1000km. Amazed we were. Same oil, just better spark timing and spark duration."
AlexB you and your colleges thoughts on block "ringing" with reference to fig 1.9.5, may have some merit, I don't know but I consider it's unlikely. I consider that significant engine oil consumption is mostly due to worn/broken piston rings & cylinder bores, which you also mention. What still confounds me is why the oil consumption "allegedly" stopped. In saying all of this, I don't know how many and what the designs are of the rings in a 1934 Buick, so maybe there is more going on than we are aware of.
Separate but related:
I read something recently that changed my prior understanding of compression ring functions. The first compression ring is mainly used for containing combustion pressures, and requires a pressure drop across the ring to ensure it remains seated on the ring land in the piston.
The second compression ring is mainly used for oil film control and to vent the top compression ring.
The third (oil) ring controls the amount of oil on the cylinder walls and provides a drain back path to the crankcase. See extract from here below: https://www.mahle-aftermarket.com/m...and-literature/pistons-and-rings/pr-40-22.pdf Similar comments here and many other sites: https://hastingspistonrings.com/tech_tip/ring-nomenclature/
So AlexB regarding your second point in #69, it seems that the second compression ring doesn't require combustion gas pressure to control the oil film on the cylinder wall. The reduced combustion pressure energising the first compression ring, may not significantly increase the oil film on the cylinder bore enough to affect oil consumption.
And finally I would be very happy to share a beer or few with you at the Hook Norton Brewery in England and we can solve the problems of the world together.
Cheers.
I also have a copy of the Repco reference that you cite from my apprentice days. As you know I prefer objective information against subjective, so I am pleased that you use reference publications to inform and support your comments, which is so uncommon these days.
I agree that worn Kettering points based distributors cause variations relative to other cylinders for consistent ignition timing. I also agree that correct mechanical advance curves are important to maximise engine power output, which are the points Sj B made in the above posts.
I agree with everything in post #54 except the last sentence. The part I don't understand or accept is the stated cause / effect of the oil burning, which is what I mentioned in post #58. I still don't understand how improved accuracy in ignition advance and relative timing between cylinders explains this statement from post #59: "We did oil every 1000km, Pen HPR mineral. She stopped oil smoke and burning oil within the first 1000km. Amazed we were. Same oil, just better spark timing and spark duration."
AlexB you and your colleges thoughts on block "ringing" with reference to fig 1.9.5, may have some merit, I don't know but I consider it's unlikely. I consider that significant engine oil consumption is mostly due to worn/broken piston rings & cylinder bores, which you also mention. What still confounds me is why the oil consumption "allegedly" stopped. In saying all of this, I don't know how many and what the designs are of the rings in a 1934 Buick, so maybe there is more going on than we are aware of.
Separate but related:
I read something recently that changed my prior understanding of compression ring functions. The first compression ring is mainly used for containing combustion pressures, and requires a pressure drop across the ring to ensure it remains seated on the ring land in the piston.
The second compression ring is mainly used for oil film control and to vent the top compression ring.
The third (oil) ring controls the amount of oil on the cylinder walls and provides a drain back path to the crankcase. See extract from here below: https://www.mahle-aftermarket.com/m...and-literature/pistons-and-rings/pr-40-22.pdf Similar comments here and many other sites: https://hastingspistonrings.com/tech_tip/ring-nomenclature/
So AlexB regarding your second point in #69, it seems that the second compression ring doesn't require combustion gas pressure to control the oil film on the cylinder wall. The reduced combustion pressure energising the first compression ring, may not significantly increase the oil film on the cylinder bore enough to affect oil consumption.
And finally I would be very happy to share a beer or few with you at the Hook Norton Brewery in England and we can solve the problems of the world together.
Cheers.
And here was I, thinking I was sharing some light hearted, worldly experience. Goodness what a dissection. I too have the famed Repco Eng Serv Manual and it too, is only slightly younger than myself. What a kick in the guts.
Quite so, but you do still need the centrifugal advance to be working properly. I've never had a distributor fail in that area though.
I've had a couple of seized ones from POs not lubricating the shaft under the rotor button.
X2
Years ago I visited a friend in the country and he said as we drove down a long straight to town, how his car took a while to pick up and get up to a decent speed. Anyway I checked it over for him and eventually found the advance was partly frozen to the dissy shaft. I bit of WD etc and working it freed it up OK. He serviced his own car but had never known about the felt pad in the dissy and the need for a drop of oil. It transformed how the car accelerated and improved his fuel usage a lot !
jaahn
I have always used a Natural approach to my approach to faulty machines. The odd bit of CRC , WD, dexron 2 , did work. But I need to impart, my very best work, is done when I get nude. Fire the old dissy graph up, and buzz.