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Discussion Starter · #1 ·
Hey friends,

My old 65 mustang (V8 289 with a new holley carb) is in trouble.

It was driving great for a year or so. A few days ago it had trouble starting. When it did start, it had a very rough and uneven idle, and very low power when driving - like it wasn't running on all 8 cylinders, felt like.

When i revved it in idle, it backfired and a lot of black gunk shot out of the exhaust (picture of the gunk on my driveway included).

It then idled OK, but there was A LOT of think white smoke and a strong gas smell - I might have flooded it with all the starting attempts, though.

I pulled a spark plug and it's very black, and oily (picture of the spark plug included).

I took an oil sample, you can see new oil in the shot glass on the left, and my dark-looking oil on the right.

Anyone have any advice on:
1) what could be the cause/problem of this?
2) how to proceed? How to i fix it?

Thanks so much to you all in advance!

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You may have more than one issue. 1st did this just start or was it after the car sat for some time? Good chance the carb needs a rebuild, especially if you have been running ethanol gas. You could have a stuck float, a damaged needle valve, a blown power valve etc. all would cause flooding conditions.

I would also suggest you post this over in the Vintage Mustang Forum. There are some real experts on the 60s engines there.

How old is the oil? Over time it is normal to get dark, but if it happens quickly it could mean the engine is ready for a rebuild and the rings are leaking. You need to start with some basic diagnostics.

1. Vacuum check
2. Compression Check

These will help identify the condition of the engine. If it checks out OK, then you need to look at rebuilding the carb and doing a tune up.
 

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You may have more than one issue. 1st did this just start or was it after the car sat for some time? Good chance the carb needs a rebuild, especially if you have been running ethanol gas. You could have a stuck float, a damaged needle valve, a blown power valve etc. all would cause flooding conditions.

I would also suggest you post this over in the Vintage Mustang Forum. There are some real experts on the 60s engines there.

How old is the oil? Over time it is normal to get dark, but if it happens quickly it could mean the engine is ready for a rebuild and the rings are leaking. You need to start with some basic diagnostics.

1. Vacuum check
2. Compression Check

These will help identify the condition of the engine. If it checks out OK, then you need to look at rebuilding the carb and doing a tune up.
All good ideas..... Simple things first
Check for moisture under the distributor cap or if any of your spark plug wires have gone bad or have rubbed through.. If your not firing correctly, unfired gas will by pass your piston/rings......
How many miles on your engine?? My first thought was timing chain/gears?????
Pull your dipstick and smell the oil.... If it smells like gasoline, change it before you try to start it again...
 

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Discussion Starter · #6 ·
First of all, thanks to all of you for the many and interesting replies! You're great0

I'll answer your questions as best i can:

  • as far as I know, the egnine was never rebuilt
  • the odometer says 25.000 miles, seller said 125.000 miles. No knowing how many times it really rolled around, though.
  • the carb was changed about 1.5 years ago from the original autolite 2100 to a holley 500 cfm street avenger
  • I had driven the car quite recenttly, most recently was a week before the issue. 3-hour drive and it drove like a charm
  • the oil is abouit a year old. I've driven about 1000 miles since the oil change.
  • i don't think the oil smells like gasoline, but i'm terrible at smelling things so not 100 sire :)

I'm pulling the rest of the spark plugs today to see how they all look individually. New ones have been ordered and are in the mail. I've also got a new set of spark plug wires sitring around, so I will take this opportunity to switch them out as well.

Once the plugs/wires have been replaced, I'm gonna try to start it, just to see what happens.

Basically next actions:
  • pull/inspect all plugs
  • put in new plugs
  • put in new wires
  • check float level (there's a little glass window on the side of the holley carb
  • If all the spark plugs look equally black/oily, was thinking about making the mixture a bot leaner too

After this i'll try to start her up, see what happens.

I'll post back here with the results, any further advice is greatly appreciated - keep it simple i'm a bit of a hobbyist/noob ;)
 
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