TBernecker

Hi folks,

With my 403 temporarily out of the car (in order to overhaul it) I am currently running an Olds 350 in my 1979 Custom Cruiser. From the casting number 3B 557752 is assume it is a '77-'80 350. It ran almost perfectly, idled very smoothly and emissions checked out fine - until I had to do some work and lost most of the finetuning. Also, the car has been sitting for a year now. It will idle now, but not smoothly. Now I want to reset everything properly, starting with ignition. So here`s the question: Can anyone tell me what basic ignition timing is for a '77-'80 Olds 350? The sticker with all the specs is still in the engine bay, but it is of little use to me as it`s for the 403. My repair manual lists the performance specs by vehicles/VIN, which is also of little use as I do not know what car my 350 derives from.

olds 307 and 403

The timing setting should be set the same on the 350 as the 403. It should be 20 degrees at 1100 rpm. I find these motors like a lot of timing advance.

TBernecker

Alright, i reset the initial timing to 20 degrees. It was somewhere around 10-12. Now I have better and more powerful pickup from idle - which makes sense I guess. The engine still isn`t idling smoothly though. And something is pinging/chattering inside. Do valves need readjustment in Oldsmobile engines? Could it be that some rocker arm nut has come loose?

Spark plug cap is set to o.60 which is correct according to the information I could find, the vaccuum meter I hooked up to the intake manifold reads 20-21 whatever-the-unit-of-measurement-is, which is in the suggested range between 18 and 22. The carb is just two years old, I can find no vacuum leaks.

olds 307 and 403

Try adjusting the idle mixture screws. What rpm is the idle set at?

TBernecker

I did avoid touching those as they were set during the last emissions testing. However now I saw that all 8 plugs are white, so I gave both idle mixture screws one turn out. Idle is smoother now, even if there still are occasional misses and the plugs are still kinda white. Maybe I`ll give it some more.

It seems hard to explain as the car was running fine before sitting for a year. Maybe the combination of lean mixture and too little timing advance somehow worked for a while...

Idle rpm is set by best guess as my newly-procured-but-crappy chinese multi-meter doesn`t work. Anyway, I`ll get there eventually

That leaves the issue of the ticking / chattering noises, but I guess that`s material for a seperate thread!

TBernecker

Hi everyone

I put a 350 in my Custom Cruiser as its original 403 needs repair work. I was idling and running great until it sat for a year. Afterwards it turned worse.
By now I got the idle to near where I want it by resetting timing advance and idle mixture (see spearate thread). What`s left is a strange noise issue. In drive, while idling it`s a tick-tick-tick noise. During acceleration it turns into a pinging/chattering noise. I can only assume it`s something related to valves.

Timing advance is set to 20degrees, I only run 95 octane fuel, the enigne is suposed to be low mileage and the seller claimed it was overhauled at some Point...
Anyway, I opened up the valve covers, there is no sign of slack. And nthing to adjust. As there is oil on top of all rocker arms I assume the oil is getting there.

I heard that These engines are sensible to oil. As I don`t trust the dipstick (aftermarket, chrome, looks odd) I drained it and refilled with 5 Quarts of 20W50 plus some o,3 Quarts of STP additive for older engines. Can it hurt to try adding another 0,5-1 quarts? That would be the easiest guess. Or could it be that this oil is too thick? Any other ideas on what to check?

svnt442

I would take the covers off again and do a good inspection of the bridges. The factory ones can be prone to breaking and sometimes it can be hard to see. Remove the rockers and do and give everything a good once over to make sure it's in good condition.

oldcutlass

No reason to start multiple threads. How many qts of stp did you add? Try declining your timing 5 degrees.

TBernecker

Alright, I will check the bridges. Covers are still off anyway, so that`s an easy one!
It was a small bottle of STP, so around 0,3 Quarts / Liters. I did swap the filter with the oil btw. The repair Manual says 5 Quarts should be added in that case. Thing is I can`t be sure whether the engine has the original oil pan... So I might just add some more to make sure it isn`t just low on oil.
Of course I can step back on the timing advance and see what happens. Thing is these noises were there before I reset the timing - and it was retarded about 10 degrees before that.

About the threads: I wanted to start a new one as I thought this isn`t (only) about ignition timing any more.

TBernecker

i unscrewed all the bridges, inspected the rockers and the pushrods. Everything seems to be in good order. I put everything back in its original place and torqued it down to spec - 25 ft lbs. Then the noise was worse... I tried adding half a liter of oil. That changed the noise but it`s still there. At least I know now that the issue is connected to the valve mechanism.

So I clearly made a mistake somewhere. Do I maybe have to torque the rocker bolts again after the engine was turned over (as some lifters were obviously up when I torqued the bolts down the first time)?
How can I determine which one of the valves is noisy?

TBernecker

I got a decent dial-back digital timing light that shows rpm as well. Set initial timing to 20° at 1100 rpm. Torqued donwn the bolts on the valve lifter bridges to spec again. Opened up the idle mixture screws (rebuilt stock carb) until I reached maximum rpm. Set curb idle to spec.
There still is a slight pinging noise at idle and some chattering under load and the engine is shaking at idle.
Total timing at 3000rpm is around 50°. At ilde, vacuum advance (hooked to manifold vacuum) adds 20°, to a total of 40°. Does that sound right? Any other ideas what might be wrong?

TommyTheCat

I also have a 78' 350 in my Rocket 88.
I had a new edelbrock carb installed which ran great, and a month or two after I was having some idle issues,
I took it in and apparently it was having some issues with the butterflys, and had to be adjusted.
not sure that has anything with your issue, but maybe something to look into.

olds 307 and 403

That sounds about right for timing.

oldcutlass

The total timing number of 50* @ 3000 rpm, is that with or without vacuum advance?

olds 307 and 403

I assume with vacuum advance since has 40 at idle with the vacuum advance. Otherwise, way too much.

TBernecker

That is 50° @ 3000 rpm WITH vaccum advance. BTW I did have an overheating condition before. The starter wouldn` t turn when the engine was hot. It was fine on a cold engine, starter, all wires and the battery are new. So I assume it was too hot around it. Stock manifolds. Maybe retarded timing and/or too lean mixture caused that heat to build up. Plugs were a little white. With the new timing setting the plugs look better now, I will see about the starter.

oldcutlass

Back your timing 2* and see if your hard starting goes away.