For all you engine guys

[drew8mc]

I'm a newbie at wrenching, so I am trying to learn as much as possible.

I'm trying to diagnose a poor idle in my 327. Below is a video of the vacuum gauge coming directly off the manifold. From the verbal descriptions, it sounds like this is a vacuum leak. I have checked all over the carb gasket, manifold gasket, throttle body, and all hoses. I took off all hoses and inspected each one, even recut the ends. I've sprayed the area over and over with carb cleaner and I can't find any leaks. I hear no hissing sounds.

https://goo.gl/photos/LsXgjzLkKYtYZhP6A

The next step is to check my timing, but my vacuum is so low, I'm guessing this is not a timing issue. Should I just pull the manifold and reseal it? It looks to be sealed all along the edge with silicone or some other sealant. I'd love to know what all you guys think.

[notsolo]

Power brake booster?...Distributer shaft wable?

[drew8mc]

The vacuum gauge is hooked up to the brake booster line, so it isn't active. I just went and checked the distributor shaft. It is supper solid with no play at all.

[Boog]

Maybe this vacuum tuning chart will help.

[geezer#99]

Check and set your initial timing at 14 degrees first. If that doesn't change it much then you might need to do the intake gaskets.

[68c10airstream]

If the distributor has Not moved, again NOT moved, and you check timing and it's retarded a lot, advance it to spec, say 6-12 degrees before tdc and then look at the vacuum gauge. If the vacuum is still low and fairly steady, say 12 inches i believe your timing chain is very sloppy and jumped teeth.

A test for a healthy engine is this, warm up engine, disconnect coil wire from cap and ground it, throttle closed (not on fast idle cam) and hook up the vacuum gauge to the booster line at the carb base (not at the booster because of the check valve built in) and crank the engine over. If the engine is healthy and does Not have a jumped timing chain/retarded cam timing cranking vacuum should be 1-5 inches of vacuum. If not you are digging in.

Years ago a shop called me on a front drive 3800 v6 no start after every electronic part was replaced and when he was talking to me someone was cranking it over in the background. I heard the starter zinging over real fast and said he had a jump timing chain and told him to do the vacuum test. He called an hour later and said NO vacuum. I told him "start digging in". Timing chain had allowed a 3 tooth jump, one more tooth and i think valves would have hit. Good luck!!

[drew8mc]

OK. I adjusted the timing to both 12 and 14 degrees advanced (it was significantly retarded beforehand) and there was no change in vacuum, although the vacuum read a steady 7 instead of jumping like the video. Idle seemed smoother but still jumps around by 30 to 50 rpm.

I have not tried removing the coil yet. Perhaps tomorrow.

[cableguy0]

Before you go chasing a ghost we need to check the engine itself. First thing to do is run a compression test. That will give some insight into the mechanical condition of the engine. If you dont have a compression gauge set get one. They are cheap and a completely necessary tool especially when working on older engines. If the engine is worn or has a cam wiping out etc the compression tester will show you. If the engine isnt in good mechanical condition it doesnt matter what you do with tuning its not going to run right.

[drew8mc]

OK.. i disconnected the coil and did the vacuum test again. I got somewhere between 2 and 3. It fluctuated.

I then did a compression test. Here is a photo of the spark plugs and then a diagram of the results.

[Rickysnickers]

Those look like some seriously fouled plugs. Does you truck blow a lot of smoke?

[drew8mc]

No. Not a lot of smoke at all. It starts hard sometimes and requires a firm foot on the throttle to start. It smokes some then. I want to keep this running until next winter and then over the winter I want try and build a new engine and swap it in the spring.

[drew8mc]

I did a ton of tune up work on the truck this past weekend. The biggest thing is a new carb. I went with a Quickfuel Slayer 600 cfm. I also put in a new thermostat (it overheated right in downtown Portland), new fuel filter, and new air cleaner. I also installed an in-line fuel pressure gauge and put in new plugs. I had to bend my throttle rod in weird ways to get it to the length I needed. I have a new one at the correct length that just arrived today.



Holy Crap! It's a like a new engine. Pulls so much harder now its unbelievable. I thought the engine was just a dog and headed for a rebuild, but man, what a difference.



Also found out I have late model camel humps. Casting number 3927186. From what I have read they are the later heads with accessory holes. Cool. I know these have been beaten by any modern head, but its still pretty cool, set up as an old school hot rod.