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Discussion Starter · #1 ·
Have a friend with a 70 olds cutlass 350/th350. Engine is mostly stock. He installed a pertronix lobe sensor last spring. Last fall he installed a performer intake and a holley 600 vs carb. Was never able to get it to idle correctly. He had a q-jet rebuilt and installed it, car still wont idle. I went over to help him yesterday. Car will not idle below 1000rpm. dies in gear. Checked the timing, Vacuum advance is not working (told him to get a new one). at 1000 rmp timing was at 20* advanced. tried to retard the timing and reset idles speed to no avail. everytime we turned the timing back the car would stall. It is sunning pig rich, if I lean the idle mixture it stalls. while its running, it is very rough/shaking. any ideas where to start? Could the bad vacuum advance be causing the issues? any help would be appreciated. TIA Ken
 

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When he installed the Pertronic, did he use their coil. Also they say you don't need a full 12 volts to run their product,8 is enought. But I have talked to them, and they say maybe you need a 12 volt wire. I would try it. Also, I would check the distributor, and make sure it is in the right position. I would also do a compresion check,may have broken valve spring. Valve train problems are a problem with Olds.Timming chain may have jumped. Also if you know you have a bad vacume addvance, replace it. Also check for a vacume leak. Also check the plug wires are on correct. Olds goes counterclock wise, not clock wise like a Chevy.
 

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Discussion Starter · #3 ·
We tried a 12v jumper with no difference in idle, cap, rotor and wires are new. double checked firing order also. its good. He is running an msd blaster2 coil, but it was recent addition as he thought his stock one was bad and causing the rough idle problems. Can not hear any valve noise(no ticking or clacking) so i dont think its valvetrain related- but could be wrong. Ill have him run a compression test so we have a baseline. It has run kinda crappy from day one, he thought it was carb related- hence the upgrade from 2bbl to 4 bbl. now the problem is worse. Do olds motors have adjustable rockers?
 

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Rockers are not adjustable, and shouldn't need adjustment on a stock motor.

It really sounds like a spark problem to me - shaking and rich could mean raw fuel being spit out through cylinders firing at the wrong time.

Also, like on Chevies, the outside of the stock balancer can "walk," causing the timing line to move. You should confirm TDC with a screw device or a dial indicator.

If all else is good, strong spark verified, TDC verified, spark plug wires confirmed to right cylinders and rotor on right, then use a dial indicator off of #1 rocker to check cam timing (or follow the Chassis Service Manual directions for using a ruler) because high-mileage models CAN jump a tooth on the timing gears (somewhere around 105,000 miles)

- Eric
 

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Discussion Starter · #6 ·
he is running a compression check tonight just to make sure everythings ok. Iv heard of problems with the pertronix lobe sensor ( reads the lobes that used to open the points instead of a hood that slides on the shaft). Im wondering if something is up with that. The cam timing could be off, it has a new timing chain but neither he nor I installed it. it was replaced when the motor was freshened up just before he bought it.
 

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I had an '72 Olds 350/350 and it did that for quite awhile. Had the carb rebuilt, tune up, nothing worked. Turns out the timing chain needed to be replaced. It was fine after that.
 

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Discussion Starter · #10 ·
What kind of vacuum reading are you getting when at idle? is it steady or fluctuating?
vacuum gage bounced a little but not much, it was between 17 and 20"
 

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Ken,
I believe it is in the valve train but, If anyone of your friends has a stock dist I would try that first. I have had a Olds 350 and my BIL had a 330 both had the same problem you are describing. Neither one made any ticking sound but his was a bad camshaft and mine was a bad timing chain and 2 valve springs were shorter then all the rest. I have no idea how that was and the motor looked untouched for a long time, in fact I had to pry the valve covers off!!
If the dist doesn't clear it up you will have to take it apart and inspect the entire valve train. There is no telling what the PO did when it was "freshened up"
My 1970 - 77 Chiltons Manual says a Intermitten fluctuation at idle is ignition miss or sticking valve
If it fluctuates as engine speed increases it is a Ignition miss, blown head gasket,leaking valve or weak valve springs.
 

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Discussion Starter · #12 ·
Ken,
I believe it is in the valve train but, If anyone of your friends has a stock dist I would try that first. I have had a Olds 350 and my BIL had a 330 both had the same problem you are describing. Neither one made any ticking sound but his was a bad camshaft and mine was a bad timing chain and 2 valve springs were shorter then all the rest. I have no idea how that was and the motor looked untouched for a long time, in fact I had to pry the valve covers off!!
If the dist doesn't clear it up you will have to take it apart and inspect the entire valve train. There is no telling what the PO did when it was "freshened up"
My 1970 - 77 Chiltons Manual says a Intermitten fluctuation at idle is ignition miss or sticking valve
If it fluctuates as engine speed increases it is a Ignition miss, blown head gasket,leaking valve or weak valve springs.
It seems to clear up while driving, but once you come to stop it wants to stall. Im trying to talk him into pulling the engine and giving it a once over. He has all the paperwork for the work that was done before. a local machine shop did the work. The thing i find troubling is now work was done to the heads. paper work states that no headwork/valve job was needed. Engine had 100000 on it at the time. looks like they might have cut a few corners. the teardown was done due to a broken timing chain.
 

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Discussion Starter · #16 ·
Well its not looking good, He ran a compression check, 5 cylinders were in the mid 80's one in the 70's and 2 in the 60's. now we have to figure out why. dont have anyway to do a leak test. Told him to hook his air compressor up to 1 cylinder, shoot some air in and listen for whistle in the intake, exhaust, or oilpan/valve cover. We'll see what happens next.
 

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Well its not looking good, He ran a compression check, 5 cylinders were in the mid 80's one in the 70's and 2 in the 60's. now we have to figure out why. dont have anyway to do a leak test. Told him to hook his air compressor up to 1 cylinder, shoot some air in and listen for whistle in the intake, exhaust, or oilpan/valve cover. We'll see what happens next.
Ken,

I hope you remembered to tell him to be sure both valves are closed on the cylinder he puts compressed air into. BTDT lol
 
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