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Discussion Starter #1
Hi again,
Another problem I hope you guys can help me with.
My engine kills sparkplugs. See the picture .. basicly kills them after 20 of idle . Obviously things are very wrong . Spark plug is the equivalent of the old one I can get in Europe but iam getting new msd iridium plugs. But they new plugs obviously won’t fix the first problem. Engine has new carbouretour and a new distributor and and the leads are all working and tested altought I get new ones in the next days. When I connect my vacuum gauge the the manifold I get zero or almost zero vacuum.. why is that ?? Why’s wrong ? The guy that sold me the car said it was setup for drag racing .. have I got a very different cam to standard?? The engine is a bbc 1978 open up to 468 that’s all I know .. what can I check ? The initial timing is 16 but even likes to go higher and has no problem .. still burns my spark plugs regardless.. has my harmonic balancer slipped ?? So the timing is off ?? Does the cam ( don’t know which it is)in my car cause to have super low vacuum at idle ?
Do I have a leak ? Please give me all you’re input:))
 

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Going with the spark plug is black and sooty, the motor is running quite "rich". Too much gas, or in some cases, improper combustion flame. I would start with too much gas. If the carb is new there could be multiple reasons it is running rich - incorrect idle setting, wrong jets, float adjustment, leaking internally, etc.

Regarding no vacuum at idle, where exactly are you connecting the vacuum gauge?

How does the car idle - smooth, rough, stalls?

From what you have said and the little I can see in the pic, you probably have a pretty aggressive cam. This will cause a rough idle, low vacuum and vacuum to "jump" around. It will also require much more in depth and precise tuning.
 

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Discussion Starter #4
Vacuum gauge is connected to intake manifold . Vacuum advance plugged . All ports of carbouretour plugged . Joined into a t piece of the intake manifold going toward the power brake and pcv valve and transmission.i disconnect the tube from transmission and hook myself into there . The idle I personally think doesn’t sound as it should be. Rough:) not nice in my opinion..the carbouretour is running nice as I can tell and I do t wanna play around with settings since i installed it brand new I started up right away and seems sound .. just adjusted the floats . Cannot really adjust the idle screws without the vacuum gauge reading right ?
 

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I agree with SouthBay2s that your plugs indicate your engine is running rich.
If it were me, I would run a separate vacuum line for the PVC valve... since the PVC valve acts like a "controlled vacuum leak" and it could be effecting your vacuum to the power brake booster and transmission vacuum modulator.
It looks like you have a Holley carb. Look at the back of the carb on the throttle plate portion... there should be a large port that you can use to connect a 3/8" vacuum line to your PVC valve. Use the vacuum fitting in your intake manifold for the power brakes and trans.

You mentioned the engine was set-up for drag racing... and that leads me to believe you have a high duration/radical/aggressive cam. These types of "racing cams" do not like to idle for extended periods of time. They were designed to run at higher engine RPMs. Does your engine seem to run smoother if your rev and hold your engine RPMs at 2000 - 2500 RPM?

It also looks like you are running an HEI distributor. Can you confirm that you have at least 12 volts to the power wire that is connected to the "BAT" terminal on the HEI cap (ignition switch turned to "RUN" position and engine NOT running)?

To get an accurate vacuum reading, try connecting your vacuum gauge to the small port that is located on the throttle plate portion on the front of the carb (next to the accelerator pump). Be sure all of the other vacuum lines are connected or plugged.

Do you run your engine with the vacuum advance canister (VA) of the distributor connected?... and if so, is it connected to a full time vacuum source or a ported vacuum source? Connecting your VA to a full time vacuum source may also help smooth out your engine and increase your vacuum at idle... but there are other distributor adjustments that should be looked at if you plan to connect your VA to a full time vacuum source.

What could you or anybody recommend for a initial timing on a aggressive cam?
If you have a larger duration cam (aggressive cam), I think 15°-16° initial timing BTDC is a good starting point (with the VA disconnected).
 

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It looks like it is very rich to me as well. Show us a picture of where the vacuum gauge is hooked up at. Is the choke plate opened all the way?
 

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Discussion Starter #9
the choke is open all the way when warmed up.closed when starting as it should be. its automatic choke on a brand new holley street avenger 870. it had a holley 3310 (780 cfm) before .has a fuel regulator installed now with 5-6 psi.float levels are set in fact could be a bit in the low side. i will today change the pcv hose to the carb instead.it does indeed sound better when at high rpm. what else i have notice is that the engine gets warm within seconds..2 mins of running and you can't touch exhaust and the the rocker covers are warm.engine also shakes when on idle .800 rpm.rought idle basically.hei has full 12v now after fully rewiring the car with americanautowire kit.
i did not connect the VA since i have installed it..thinking of getting the engine setup first running and knowing what aim doing.
here comes the funny part..it kills sparkplugs..the car will idle and drive short distance sound my parking lot just to test things. then next day the car misfires and even won't start.new sparkplugs in and voila starts and runs fine again.but the plugs that has been in before for lets say 30 mins of running time are dead .i tested them on my other car and no spark!!

when you guys say its a radical cam and lets assume it is ..how long can it sit in idle at my drive or traffic lights before the sparkplugs get fouled ?with a radical cam in the car will it ever be street drivable?
 

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Discussion Starter #11
older video with old carb. how does that sound to you guys ? what can you tell me from the sound?
 

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An easy check is at idle turn the idle mix screws in a little at a time. You should reach a point where the idle starts to drop. This is a good starting point for the idle mix screws. If you turn the screws all the way in and it is still running, advance your timing about 5 degrees(Your idle speed will icrease), turn down the idle speed to around 8-900 rpm, and try the mix screws again. I would also check carefully for vacuum leaks.
 

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I would also find the instructions that came with the carb and go through the adjustment procedure they recommend. My old big block Nova sounded just like yours and would idle for hours. That engine properly tuned should keep the plugs clean for years. Looks like you're running a NGK 5 heat range plug, which should be in the ball park.
 

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I would also find the instructions that came with the carb and go through the adjustment procedure they recommend. My old big block Nova sounded just like yours and would idle for hours. That engine properly tuned should keep the plugs clean for years. Looks like you're running a NGK 5 heat range plug, which should be in the ball park.
I would also find the instructions that came with the carb and go through the adjustment procedure they recommend. My old big block Nova sounded just like yours and would idle for hours. That engine properly tuned should keep the plugs clean for years. Looks like you're running a NGK 5 heat range plug, which should be in the ball park.
I would also find the instructions that came with the carb and go through the adjustment procedure they recommend. My old big block Nova sounded just like yours and would idle for hours. That engine properly tuned should keep the plugs clean for years. Looks like you're running a NGK 5 heat range plug, which should be in the ball park.
Check the transition slots. I have had new holleys bad right out of the box. Holley service over the phone was not a great help.
 

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It sounds like you have an aggressive cam in your engine... but it does not sound like it is too aggressive for street use.
It also looks like you are running a dual plane intake manifold and that should also help with street driving.
What size gap are you running on your plugs?... Even with an HEI, you should only be gaping your plugs around .035.

here comes the funny part..it kills spark plugs..the car will idle and drive short distance around my parking lot just to test things. then next day the car misfires and even won't start. new spark plugs in and voila starts and runs fine again. but the plugs that has been in before for lets say 30 mins of running time are dead. i tested them on my other car and no spark!!
Are you stating that all 8 of the spark plugs that were used in the engine for about 30 mins are all dead/no spark the next day?
Do you have access to an ohm meter? If so, can you check the resistance of a brand new spark and compare that with some of the dead spark plugs that were previously installed and run in your engine.

Once you redo your vacuum lines, can you let us know what your vacuum is at idle (connecting your vacuum gauge to the small port located on the lower/front of the Holley carb).

Shown below are some procedures I use to adjust the idle mixture screws on my Holley carb.
Connect a vacuum gauge to a full time vacuum port (front of carb).
*Turn both idle mixture screws clockwise into the carb until they "lightly" seat... and then turn each screw out (counterclockwise) 1.5 turns.
*Start your engine and note your vacuum reading at idle.
*With your engine still running, turn one of the idle mixture screws in (clockwise) 1/4 turn. What happened to the vacuum reading?
A - If your vacuum increases, turn the other idle mixture screw in (clockwise) 1/4 turn. Keep repeating this process of turning each idle mixture screw in 1/4 turn from side to side until you achieve the highest vacuum level (Note: At some point your vacuum will begin to drop as you turn in the idle mixture screws).
B - If your vacuum decreased, turn the same idle mixture screw out (counterclockwise) 1/4 turn - previous setting. Now turn the same idle mixture screw out 1/4 turn. If the vacuum increased, turn the other idle mixture screw out 1/4 turn. Keep repeating this process of turning each idle mixture screw out 1/4 turn from side to side until you achieve the highest vacuum level (Note: At some point your vacuum will begin to drop as you turn out the idle mixture screws).
C - If your vacuum decreased no matter what direction you turned the idle mixture screws (clockwise or counterclockwise), then your initial setting of 1.5 turns out from seat is the correct setting to maintain your highest vacuum level.
 

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Can you post a photo (... or give a detailed description) where you have the vacuum line from the gauge connected to.
See image below. I would connect the vacuum gauge to the "Full Manifold" carb port.
398350

With the engine running, I would think there should be some vacuum... especially when you rev the engine.

Also, have you tried the same vacuum gauge on another engine to see if you are able to get a higher vacuum reading (maybe the vacuum gauge might be bad).
 

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it looks like you’re hooked up to the wrong vacuum port. Post a picture of where it is hooked up.
 
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