318 Idle issues

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TT5.9mag said:
Found your build thread and read through it. Unreal
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I agree. Like I've stated, I'm not a mechanic... I do body and paint for a living and I am somewhat competent mechanically. I do really enjoy learning mechanical things like tuning, diag... so on. I have just been trying really hard to get this correct for the next buyer as I plan on selling it soon. It is close but not yet the way I'd like it to be. The previous owner seemed to have no issue selling something like this.. and I'm sure if he ever chimes in he will just say "wasn't like that when I sold it".
 
Everything is leading back to the crank.

Looks like they took the stock 1970 318 engine, stock pistons and stock rods, and through a 4" stroker crankshaft into it. That would not have matched up to the proper balance for that engine build.

Will it run > Yes, will it be right > No.

Hence the low end vibration.

Another test, mount a half full clear water bottle to the intake/valve cover area (duct tape is your friend).

Then run at an idle and watch the water vibration, then rev it up to 2000 rpm and watch the water vibration again.

Out of balance engine the water will be jumping through the rpm range change.

☆☆☆☆☆
 
George Jets said:
Everything is leading back to the crank.

Looks like they took the stock 1970 318 engine, stock pistons and stock rods, and through a 4" stroker crankshaft into it. That would not have matched up to the proper balance for that engine build.

Will it run > Yes, will it be right > No.

Hence the low end vibration.

Another test, mount a half full clear water bottle to the intake/valve cover area (duct tape is your friend).

Then run at an idle and watch the water vibration, then rev it up to 2000 rpm and watch the water vibration again.

Out of balance engine the water will be jumping through the rpm range change.

☆☆☆☆☆
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Wouldn't that combination push stock pistons up beyond the deck?
 
You mention the vacuum bounces between 13-15 I think.

That is what our magnum did when we had a vacuum leak due to a poorly installed intake (our fault). Once we fixed that, things smoothed out and jumped to around 20
 
Note, we had the same symptom regarding covering the secondaries. The leak was on the underside of the intake.,
 
Cuda416 said:
You mention the vacuum bounces between 13-15 I think.

That is what our magnum did when we had a vacuum leak due to a poorly installed intake (our fault). Once we fixed that, things smoothed out and jumped to around 20
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I have wondered about this as well. I'm wondering if the heads were milled or something and the intake isn't seating properly. It did seem to sit on the engine fine when I dry fitted it. There was not much room between the China wall and the front of the intake. The supplied cork gasket would not have fit under the intake.

I cleaned everything very well, put some contact adhesive on the gaskets and stuck them to the heads. I also added a swipe of sealant around the cooling passages on the head and intake side of the gasket. Then a bead of clear sealant on the China walls.
 
67Dart440GT said:
I have wondered about this as well. I'm wondering if the heads were milled or something and the intake isn't seating properly. It did seem to sit on the engine fine when I dry fitted it. There was not much room between the China wall and the front of the intake. The supplied cork gasket would not have fit under the intake.

I cleaned everything very well, put some contact adhesive on the gaskets and stuck them to the heads. I also added a swipe of sealant around the cooling passages on the head and intake side of the gasket. Then a bead of clear sealant on the China walls.
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I'm convinced our problem was caused by bad machining of the air gap knock off we used. We added gasgacinch and piled up the sealant pretty high on and around the china walls. Let it sit overnight and "that" problem was solved. Now we need to fix the ignition/timing etc.
 
inertia said:
Valves too tight can cause similar, perhaps back the rockers off a 1/2 turn, or re-adjust completely .
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We talked about that, too. I think he's going to go over the valve adjustment.
 
RustyRatRod said:
We talked about that, too. I think he's going to go over the valve adjustment.
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I downloaded and printed a "tech bulletin" from Crane Cams titled "adjusting hydraulic lifter pre-load"

I have never done it before so any tips would be great. These are the gold roller rockers on this engine.
 
67Dart440GT said:
I downloaded and printed a "tech bulletin" from Crane Cams titled "adjusting hydraulic lifter pre-load"

I have never done it before so any tips would be great. These are the gold roller rockers on this engine.
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I like using a light touch. I only go down 1/4 turn from zero preload.
 
Here is what the secondaries look like. They appear to be fully closed to me. I did back the adjusting screw out about 1/2 turn so it barely touches.

20230810_190843.jpg


20230810_190846.jpg
 
They do look closed up pretty good. That begs the question, where is the engine getting air from?
 
TT5.9mag said:
They do look closed up pretty good. That begs the question, where is the engine getting air from?
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Engines can get air from the exhaust. Its a long story so I wont explain it. It also comes from the circumference of the blades.

Watching the video the engine looks as though it has a stammer or some rough running cylinders that's causing the shaking. What's IFR and IAB in that carb?

What do the spark plugs look like?
 
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Hysteric said:
Engines can get air from the exhaust. Its a long story so I wont explain it. It also comes from the circumference of the blades.

Watching the video the engine looks as though it has a stammer or some rough running cylinders that's causing the shaking. What's IFR and IAB in that carb?

What do the spark plugs look like?
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I pulled two plugs tonight to do a compression test. Both plugs looked extremely clean. Light brown I'd say. I got tired at the end of the night but number 1 and 2 are at 145 psi. I will do the rest this weekend.

I don't know what IFR and IAB is.

Thanks.
 
TT5.9mag said:
They do look closed up pretty good. That begs the question, where is the engine getting air from?
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Right. .....and I think it's gettin air from somewhere, too. We've gone over this in depth on Facebook and a little on the phone. He's blocked off EVERYTHING vacuum related on the carburetor and the intake and it still makes no change. That's why I lean toward the carburetor. If I had a good one for him to try, I'd send it, but I don't.
 
67Dart440GT said:
I pulled two plugs tonight to do a compression test. Both plugs looked extremely clean. Light brown I'd say. I got tired at the end of the night but number 1 and 2 are at 145 psi. I will do the rest this weekend.

I don't know what IFR and IAB is.

Thanks.
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Idle fuel restrictors and Idle air bleeds. Neither of which is adjustable on that carburetor I don't THINK.
 
67Dart440GT said:
STREET AVENGER CARBURETOR - Holley https://documents.holley.com/199r10219-3.pdf

This is the manual for the carb.
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It doesn't say, nor does it give a good shot of the top of the thing. I'm pretty sure "none of that" is adjustable on them. That's why I like the Quick Fuel carburetors like I showed you tonight. They are all kinda adjustable.......but yours is not an adjustment issue, I don't believe. I think yours has something wrong somewhere.
 
RustyRatRod said:
Right. .....and I think it's gettin air from somewhere, too. We've gone over this in depth on Facebook and a little on the phone. He's blocked off EVERYTHING vacuum related on the carburetor and the intake and it still makes no change. That's why I lean toward the carburetor. If I had a good one for him to try, I'd send it, but I don't.
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I’d be more inclined to think the intake gaskets are leaking in to the valley before the carb having an internal vacuum leak but I’ve been surprised before.
 
TT5.9mag said:
I’d be more inclined to think the intake gaskets are leaking in to the valley before the carb having an internal vacuum leak but I’ve been surprised before.
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He changed them. Same thing.
 
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