I say fueling and think carb, but maybe not?

'75 Cutlass with a stock 350. Only mods are an Edelbrock Performer intake and dual exhuast. New double roller timing set and timing is bang on 20* BTC without vacuum advance (HEI), and the vacuum advance is normally connected. Carb was rebuilt about 3 years ago by Sparky's carb who came highly recommended. It ran well except it seemed to have some pinging, especially when cold under part throttle acceleration. I double checked timing and even disconnected the vacuum advance the latter of which helped slightly but it was still there. WOT experienced some pinging but not as much as part throttle. Also, it's hard to start at times, especially warm when it cranks forever before starting. Cold wad fine, and hot if I started it within 3 minutes of turning it off was fine.

Fast forward to this year. The car ran as described when I dropped it off at the port (in October of last year actually) to get shipped back to the States. When I picked it up this Feb, it barely ran. Turns out the brand new plugs somehow got super fouled out black looking en route. The only guess I have is they let it idle on full choke a long time, but I'm only guessing.

So I swap out the plugs and fuel filter (with check valve) and it idles fine with 22 in/hg vacuum, cold starts easy, but then tries to die after a few seconds. Sometimes it does, sometimes it doesn't. Feels like the bowl was only half full, ran out, but then is catching up almost/just in time. Warm and hot starting are still the same. The new and worst issue is it seem to be running very lean across the board. This is backed up by my recent wide band 02 sensor install. Initial throttle tip in, it frequently tries to stall and goes up near 18:1 AFR, then settles back to around 14 and accelerates when at part throttle. WOT also bogs, then accelerates, but seems like it's surging and is around 14-15:1 AFR.

Any input? Seems like the carb, right? I have checked for vacuum leaks extensively and found none. Where should go from here?

 

Time to learn what all those links and levers do on the outside of the carb. If you haven't read the CSM or carb books, that will help. If each one is in place and working smoothly, things go better.

The fuel level is crucial, and is controlled by the float and inlet needle. Even a tiny particle of dirt can prop open the valve and flood the carb and produce black plugs.

The choke will THEORETICALLY never blacken the plugs, because 1) it is opened to the proper cold operation setting as soon as the engine develops vacuum, and 2) it continues to move open as the engine warms up, even if the throttle is not blipped. The throttle blip serves only to release the Fast Idle Cam in order to attain a lower idle speed. Proper choke plate position is not hindered by Fast Idle Cam positioning.

It might be time for you to become trained in basic carb service. Usually a cleaning and re-assembly will suffice- especially if all the adjustments have been done by a talented service man such as Sparky.

 

It seems strange that it pinged. Even with the stock lean calibration, even on 87 I ran 60+ degrees part throttle. My current motor with 9.5 to 1 is a different story. I would adjust your APT, start a turn at a time and go from there.

 

I forgot to mention I run 93 octane all the time.

 

I would try a new ethonal resistant accelerator pump like Cliff Ruggles sells. I wonder if your double roller timing set is off and therefore throwing off cam timing. There is no way a 7.8 to 1 350 should ping on 93 octane.

 

I need to learn about carbs for sure. Don't really have a ton of free time at the moment though to start into a new major project and have the car taking up a spot for a while. Might just have to send it off to get fixed if it isn't something quick'ish/easy to fix. I was just trying to zero in on that being the issue before I did. Thanks for the explanation of how the choke works btw. I obviously didn't have a good understanding but it makes sense. I wonder how they managed to foul them out then.

Had the pinging issue before the timing chain/intake/dual exhaust by the way. I was hoping the new chain would fix it, but it didn't. Also, the car has been running on non-ethenol Japanese gas until it got back to the States, so I don't think that's the cause. Not saying the carb doesn't need fixing, but not because of that. It also has a new dizzy on it (stock weights/springs) which didn't help.

Would a new fuel pump be worth trying? Could there be something physically wrong in the engine like cracked piston that has a sharp edge that causes a hot spot? I just learned one of the heads had been replaced once upon a time due to overheating/warping. I did check and they are both crappy #8's.

 

I think that the question you must ask yourself (and you almost have) is, "Did somebody f**k with it between when you dropped it off and when you picked it up, and if so, how?"

Worked fine one moment, picked up a month later after an ocean voyage, now not working - What has changed? Did you log the odometer reading when you dropped it off?
There's an old saying (well, there should be...) that what happens on the docks, stays on the docks.

- Eric

 

What is your total timing set to?

Vacuum advance is designed to create spark earlier when vacuum is prevalent. During idle and other high vacuum situations (cruise) the advanced timing allows the burn to start sooner to better burn the mix. At WOT the vacuum is (in most cases) >3inHG so the VA is not really a factor. I'm guessing your total timing is 36*+ and causing pinging.

I'm guessing the person in charge of transit doesn't understand the start/idle characteristics of a 41 year old engine and flooded the S%*t out of it trying to start it. By the way, what kind of plugs?

The car was shipped from Japan to where exactly? Radical change in elevation?
Could you elaborate or this?

This is (in most cases) the accelerator pump

 

Odometer moved less than a mile, but they did F some stuff up. The fender was dented which I didn't notice until after I got it home so I have to just easy that. I'm sure they did something to foul the plugs, but the pinging has been a long time issue.

I haven't check total timing, but I will soon. I just want to point out that the pinging is most noticeable at part throttle though. I will check what kind of plugs were in it as well as what's in there now. The pinging issue has persisted over several sets of plugs though. It (along with averaging 8 mpg) was also the reason I changed the timing chain to no avail.

The car went from sea level to 600' MSL so not much change there. I installed a wideband to help trouble shoot. It's just a crappy "glowshift" brand gauge using the newer Bosch 4.9 sensor. Probably not the best out there, but I'm not running a 600hp monster here. The recent (since I picked it up at the port) lean stumble/surge issue is new and the reason for thr wideband.

I just went down and popped the air cleaner top, then actuated the throttle. The car had been sitting about a week without being started btw. First pump got nothing. 2nd and 3rd got nice steady streams. Looked like I think it's supposed to. 4th, 5th, and 6th got done spurting dribbles, then bone dry after that. Sound about right? How many squirts should I get, and why was there nothing on the first?


I was trying not to present my theories too much as it might lead people to my thinking which might be wrong. I suspect the following though:

-the fouled plugs thing was a fluke and unrelated
-not timing/timing chain/vacuum advance related
-hard starting when warm, pinging, and stumbling/surging might not be related (yes I know that sounds like timing if related)
-recent running lean issue is just the same problem getting worse

Those are my suspicions, but I am open to hearing how wrong I am. If the consensus was "carb" I was going to pull it off and send it for a rebuild (or do it myself of it was kind of easy). Anybody think there could be something in the motor itself buggered up?

 

How many miles on that motor? Those years of 350's were extremely durable and reliable for their time. Even the original nylon timing gear held up better than the late 60's- early 70's 350's. It is possible that your cam timing is off, many sets are far from accurate. I would say if that is the problem, yours is advanced. I believe most sets end up retarded that are off but who knows for sure. 8 mpg, what kind of driving? If that is Japanese grid lock, then probably about right. I know we could get 20 imperial on the highway no problem with our old 75 before the days of ethanol gas.

 

Measure fuel pump output PSI. Needs a steady 5-6 +/-.5. Float level is set at what? How do the plugs read now? I suspect when in transport it had a lot of short on/offs with the choke on. Thats common for that to happen transporting a carburetor car. Dont rule out shet fuel either. Ever had the tank down to look at the pick-up Inspect the fuel lines too. Especially the soft lines.

 

First, I would back the timing off until the pinging stops. It should start up better with the timing backed off a bit.
Then I would check/replace fuel filter, pump and lines.
Check , clean plugs and regap if needed .
Check the base of the carb especially around each side near the back down at the intake for leaks, this could be giving you lean running also the bog.
I would just pull the carb off and have a look see for carbon leaks myself.
After sitting for a week you can expect to pump the gas a few times before it fires up, once its cranking over after about 3 pumps it should be fine if the carb/timing is ok.

Eric

 

The motor has a little ovef 100k on it. The timing set is the double roller everybody on here recommended but I din't recall the brand right now. The 8mpg was mostly stop and go though, yeah.

How would I go about checking the psi from the pump? As much as a tool would cost, I could probably just buy a new pump. Already put a new fuel filter with check valve in it. I have no idea abiut the float level. How would I check? I will probably ou the plugs soon and check them. I have already checked for vacuum leaks pretty extensively, but I will some more. After I check to see what my total timing is now, I'll dry bumping it back a bit.

 

If your asking these questions I will guide you towards finding someone who knows how to do this, especially carb disassembly as thats how you check the float condition and its level. Or youtube to see if its something you think you can do (encouraged). A pressure/vacuum gauge is fairly inexpensive. Reading your vac signal is a great way to tune a carbureted engine.

http://www.amazon.com/Lisle-20300-Va...r/dp/B000CODRF

 

I have a vacuum gauge and I'm getting 22" vacuum at idle. If I were to test the fuel pressure, would I simple pop the hard line off the pump, insert the adapter connected to the gauge, and crank?

 

Yup. The short counterclockwise scale on almost all shop vacuum gauges reads fuel pressure in psi.

- Eric

 

You need to securely clamp the gauges hose to what ever is coming off the pressure side of the pump. This usually requires removing the cone shaped plastic end on said gauges hose. Then crank for a short burst while observing the gauge.