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Expert
Posts: 1348
  
Location: Valley Forge, Pa. | I've been trying to track down the issue with my rough running motor[1960 318/PF/2bbl] for years with no improvement. Its been going on so long that I really don't pay much attention any more but every once in a while I try something different. Funny thing is I don't remember if it ran poorly before I rebuilt it 8 years ago. I rebuilt it because it had a broken oil ring.
It has a rough idle, rough at slow smooth accelreations, and roughnest at steadly lower RPM crusing. Accelerates smoothly with more fuel. I have changed every part of the ignition several times including the dist. and recently went to H.E.I. that has built in coil so the ignition itself should be eliminated as the issue. No change. Its not like a dead miss like a bad plug or something but but more like lack of fuel miss. If that makes sence?
As far as timing, I time my car by how it runs. I don't use a light. I find it much easier to pull my dist and change points and all so between replacing dists and tuning, I probably have pulled the dist at least a dozen times so even if my timing is off some NOW, I must have had it correct many times in the past as I would advance or retard it tiny amounts each time I had it out until it was running its best.
Thought it might be vacuum and the gasket on the intake appeared not to be seated properly. I sprayed carb cleaner around carb and intake with no change but still I replaced the intake gasket with no change. Plugged the vacuum with no change. Have had 6 different carbs including a new ZIPP remanufactored and an NOS one [rebuild each carb also] and no change. Adjusted valves[hot] 3 times. I haven't tried that in a while? 3 times with no change. I can't believe I coud poorly adjust to same results 3 times?
I can't think of anything else. I Figured that even if I didn't solve the problem, doing all I did would at least make some slight change that might start me in a direction? I even bypassed the whole wiring harness and used a resistor coil directly wired to the battery with no change.
I checked my compression and got 120 to 122 all the way around but thinking about it now, I think I took that with a cold motor and I know I didn't open the throttle at the time. It allways fires emmediately before 1 revolution which is a good sign. It did seemed to be lacking in power this time when I towed my boat for 7 HRs. I usually run mid range gas but with the tow, I ran hi-octane + I added a bottle of 104+. It never pings anyway but it did help some pulling the big hills of up state Pa and N.Y.
I wonder if I checked the compression correctly but a garage that tried to find the problem also got 125-127 all cyls. Its not great but its even and I don't think compression should be an issue?
Just wondering, IF the compression were low enough to affect it how a motor runs, would higher octane fuel make a difference? Speaking of that, a friend just gave me 10 gallons of leaded AVGAS. What is the octane? I'd like to burn it off in my Suburban. What is a good safe proportion?
As always, venting my frustrations,
Karl.
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Expert
Posts: 1740
Location: Alaska | First off, what color is the avgas? If it is red, it is 80-87 octane ( not likely because has not been produced for some time) If it is a blueish color (most likely) it is called 100 octane low lead. It still has a fairly high lead content, about 2 PPM but lower than the old avgas. It won't hurt your engine but will cause some lead build up on the plugs, but also it won't help your engine run any better. OK, I know too much trivia.
A compression reading of 120-125 psi on a cold engine sounds completely normal to me. Does it use much oil? My first thought is a vacuum leak, even though you checked for it, could there be a crack in the intake manifold not visible, on the under side? IIRC, you don't have power brakes, a possible source of a vacuum leak. |
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Expert 5K+
Posts: 7809
 
Location: Williams California | Generally, if compression is below 70 PSI, that cylinder will not fire. If all cylinders are equally low, it could indicate a slipped timing chain. I've owned many different gauges, and found none to rear anywhere close, but as long as all cylinders are fairly even, you should be OK.
---John |
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Expert
Posts: 2264
Location: McComb, Mississippi | Hook up a vacuum gauge and see what the gauge reads. A healthy engine will normally be between 16-21 inches at idle. |
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Expert
Posts: 1740
Location: Alaska | a vacuum gauge was a very useful tool on the older engines, if read properly it could tell you a lot about the condition of your engine. The old Motor books had a very detailed section on how to read a vacuum gauge. |
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Expert
Posts: 3402
Location: Chestertown, NY ( near Lake George) | Could we at least check the timing, kinda basic, no? May not cause your issue but wouldn't it be nice to know as a baseline. |
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Expert
Posts: 3035
Location: N.W. Fla. | The lower the C/R is the less octane you need. A '60 318 is advertised @ 9:1, probably used Regular that would have been higher octane than now. Guessing low 90s. Are you sure the carb is clean? Once thought I'd broke something in the engine, but it was a bit of a dirty carb that spray on Gum out solved. Really old spark plug wires sometimes cause problems, or even a bad tranny mount in some cases. |
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Extreme Veteran
Posts: 594
Location: Melbourne, Australia | Karl, I cant remember if your car has boosted brakes or not but there is a valve on the oval boosters that can leak quite badly. 14 years ago or so, I installed a fresh engine in my worn out engine bay (car had sat for 30 years) The motor fired but idled poorly, sometimes stalling.... culprit was the booster leak... I plugged the line and got the motor running fine quickly after discovering this. Colin |
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Expert
Posts: 1348
Location: Valley Forge, Pa. | Actually a vac. guage is one thing that I personally have not done yet. I have had it timed by others trying to find the issue. 3 garages have had their chance. I gave them the shop manual and several books on correct specs. They all gave up.
Again, I have had 6 different carbs on it. ALL have had carb kits installed after they did nothing different as they were. I sent 2 carbs to a machine shop and had them put in new shaft bushings and machined the shafts to make them probably much closer tolerences than stock. I sent one out for a complete proffesional $250 rebuilt. Man it looked great! But no difference.
Unfortunately the car is a money pit that I just like so much but it has really been very good to me.
I've been trying to do everything I can[$5000+] on the brakes to make it stop well but all I can do is pray no one does something stupid in front of me. Soon, I am hoping to put a the hydra-boost system that uses the P.S. pump for power brakes. See what another $1500-2000 will do?
There are so many things I could have done with the $10,000+ that I have spent on the handling, brakes, and poor running. I FINALLY after a couple $1000 got the handling to the point that I can take my hands off the wheel at 80 MPH and it will go straight down the road. Mostly that was no one knew how to align it, junk COKER tires, rebuilding everything related, and the final nice improvement, putting that rubber bushing/coupler on the steering shaft.
At this rate, I hope to have a normally operating vehicle like the rest of you seem to enjoy before someone tells me I am not alowed to drive any more. Might take me another 10 grand but i WILL get there. |
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Expert
Posts: 2264
Location: McComb, Mississippi | After rereading this post, I have another thought. We know the carb is not the issue. What are the chances of having 6 bum carbs? Not very probable. You've replaced the intake gasket and plugged the vacuum port with no change. You have checked/bypassed/replaced the wiring harness and ignition system. The only thing not determined in the ignition system is the timing. Compression checks out okay. Have you by any chance adjusted the valves? I'd pick up a vacuum gauge/pressure gauge, timing light, and feeler gauges. Set the timing so we know that it is not the culprit.(one less variable) hook up the vacuum gauge and observe the needle. It should be steady. Than take the combination vacuum/pressure gauge, disconnect fuel line after fuel pump and check the pressure while you crank the engine over with the ignition system disabled. It should be close to 5psi. Next, drive the car for a few miles to get it warned up. Remove the rocker covers and adjust the valve clearance. You can do this with or without the engine running. I prefer to do it with the engine off. Once done, test drive the car and see if the problem persists.
Edited by plymouth 2016-08-17 11:30 PM
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Expert
Posts: 1740
Location: Alaska | Here's a couple of thoughts, you said it has run rough since you rebuilt it 8 years ago but not before. Could it be possible the timing chain is off one tooth? I believe it still might run but not run right. I don't know you but I think this is not likely. Here is one more thing that might be more likely, it is getting harder to find new camshafts for these engines. Did you install a new one or did you have the old one reground? If it is reground, maybe it was not done right. |
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Extreme Veteran
Posts: 360
| You said you changed every part of the ignition system. Did that also include wires? The symptoms you describe sound like a bad wire or possibly plug to me. The other issue could be the timing is off a bit more than you think.
I think you have hired the wrong people to repair and diagnose the problems you have encountered. The beauty of these cars is how simple they are compared to new cars. The brake system is simple to go through and replace parts. The engine is a basic pushrod design with a carb and most all maint items are easy to access or straight forward. For 10k I would have had your car tip top. My 58 imperial was sitting since 1972. Nothing worked, especially the brakes. The lines and wheel cylinders were full of crap. Few days of purging lines, rebuilding and honing the cylinders got it all working again. I cant imagine why your brake system cost you so much. The entire system can be done new for way less. That would include new lines, cylinders, master cylinder, brake switch, vacuum can, drums and pads with a fully purged working system in the end. Brake system is one of the simplest systems on a car until you get into the antilock brake systems with traction control. Anything without that is so simple especially since the important parts are available new over the counter and easy to replace. |
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Elite Veteran
Posts: 982
Location: Upper Hunter NSW Australia | 58coupe - 2016-08-18 4:59 PM
Here's a couple of thoughts, you said it has run rough since you rebuilt it 8 years ago but not before. Could it be possible the timing chain is off one tooth? I believe it still might run but not run right. I don't know you but I think this is not likely. Here is one more thing that might be more likely, it is getting harder to find new camshafts for these engines. Did you install a new one or did you have the old one reground? If it is reground, maybe it was not done right.
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All good ideas above .........
I know I've arrived a month late for the party but 58Coupe's idea has merit.
Engines will often run with a tooth out on cam timing, and some engines with a tooth or two and I've seen one run with 3 teeth out recently ( my son's engine actually, did the cam timing himself, first year apprentice mechanic,was 3 teeth out and running, though not very good at all I might add )........
Also vacuum loss to the booster or to cracked vacuum lines is one that often gets people, I learn't that one early in my career after spending days trying to find a miss that was from a perforated vacuum booster diaphragm.
Have the valves been adjusted correctly?
Camshaft......is it worn?
Plug wires..........have they been OHMS checked for resistance? or replaced?
Have you had it on an Engine Analyser at all ? , ( Oscilloscope machine ), not one of those hand held ones, a proper workshop one, that will tell you what each cylinder is doing with regard to how the ignition system for each one is working? Older workshops would probably still have one in the corner gathering dust, they are very good older car diagnostic tools.
I wouldn't send my car to a workshop that has pimple faced kids working as mechanics with plug in computer testing skills either, most don't even know what a carburetor or a set of points are now days. If you haven't already done so, try and find a shop that has an older mechanic/mechanics working there as the chances are that you'll get far better results and less ripoff from a so called " old school " EXPERIENCED mechanic than the new age ones that are being reproduced now.
If I lived a few thousand miles closer I'd love to have a look under the hood of your car and have a look at it for you, and the brakes, well , there's gotta be something not right there that's not being picked up by the brake experts you've taken it to, the system isn't overly complicated. Modern electronic assisted systems aside, the basic principle has been the same for many years.
Would love to see the right person looking at your car.............and fixing it!!
Let us know how you go.
Cheers.
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Expert 5K+
Posts: 8445
Location: Perth Australia | My tune up machine
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 tune up machine 004s.JPG (108KB - 76 downloads)
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what is consitered too low compression and what are affects?
