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Circa 1975 318ci 4-Barrel conversion Engine Timing Question

JWKetron

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Good day,

I recently purchased a very low milage 1975 fury custom 2-door. The second owner installed an edlebrock four barrel intake manifold to match the engine as well as an aftermarket 4-barrel edlebrock carb with electronic choke. He removed most all emissions controls prior to my purchase. Stock 1975 timing with a factory set up 2-barrel caeb indicates 2 degrees before TDC. Looking toward 1977 when Plymouth offered a 4-barrel set up for the 318, the 1977 data shows 10 degrees before TDC. I have noticed a valve chatter inside the engine under load while driving within a certain rmp/load limit traveling down the road. The noise goes away as I let up on the gas. Does not chatter at idle. My engine is currently timed for the 2 degree mark, I have checked it. I now have a 4 barrel carb on it. Could changing the timing help compensate for the 4 barrel? I want to cure the valve chatter since I am now running a entirely diffrent carburetor therfore now some-what modified. The engine is a stock civilian 318 passenger car engine. Only mod was the intake and carb as well as air cleaner. Looking to cure the valve chatter to keep the low milage engine in good shape and preserved. Do I need to change the timing with the 4 barrel installed?

Thanks,

Jon

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Good question….surprise answer. In general, your engine will run better and more efficiently with quite a bit more initial timing advance….maybe 10-15 degrees (guess), but limit your total advance to 34-36 degrees to prevent spark knock.
Since you only have a few degrees initial advance AND experience a “rattle”, I’m going to guess 1. Spark knock caused by a vacuum leak or 2. Not spark knock at all…maybe a tired lifter, worn rocker arm, slight bend in a pushrod….or “maybe@ a tiny exhaust leak
 
Valve chatter ? Not. Your engine is pinging. Forget about stock specs, many were listed for emissions purposes back in the day. What he ^^ says is a good start.
 
Seeing it was a smog motor with an EGR and now that's gone can make things harder to get right. I assume your valve chatter as you call it is detonation/spark knock.
 
Thank you gentlemen for all the advice. I purchased the stated timing device above, thank you. I will look into these other potential issues and will need to advance the timing as stated. Noticed the head gaskets have slight leaks as oil deposits are around them, potential issue too? I will need to replace these down the road. Would octane rating fuel matter? The manual suggests 87 octane. I have non-ethanol 93. Is that too high? The manual also states grade number 2 which is equivalent to 91 octane. I have the factory catalytic converter still on the car. Would a risoline additive for oil be a bad idea? The manual states to add no additives due to the converter. Didn't know if the additives may help if there is a stuck valve or such. I will also check for vacuum leaks.

Jon
 
That era had issues with valve seals coupled with the emissions crap and a carb with a choke.
Everything worked against them to create carbon buildup in the combustion chambers.
It might be best to plan on pulling the heads off and cleaning up the carbon as that is likely what is causing it to knock.
You could have a shop look at the heads to see how much the valves have sunk (if any) and check the guides.
Might be able to just hand lapp the valves and install new valve seals and run it.
You may want to remove the cat or get a new one. I'd just remove it.
 
Thank you gentlemen for all the advice. I purchased the stated timing device above, thank you.

Jon

Hey Jon;
Just a word of warning on the timing light, keep the pickup (it clamps around #1 plug wire) away from the exhaust manifold-----it will melt and become useless (they cheapened the plastic).
And keep the light itself away from heavy vibration and don't drop it-----lol.
One more thing, watch some vid's on u-tube on how to use it-----supplied instructions -----not real helpful
 
Hey Jon;
Just a word of warning on the timing light, keep the pickup (it clamps around #1 plug wire) away from the exhaust manifold-----it will melt and become useless (they cheapened the plastic).
And keep the light itself away from heavy vibration and don't drop it-----lol.
One more thing, watch some vid's on u-tube on how to use it-----supplied instructions -----not real helpful
The cords can get wrapped up in a spinning fan very easily. THere are a lot of good direction from the posts above. SHow us a picture of where the vacuum advance connects to the carb.
 
Thank you all for the tips and information. Here are pictures of the 4 barrel carb and intake manifold.

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I have better luck setting the timing "by ear" to where the specific engine likes it, rather than by the book spec.

Loosen the distributor hold down, but only so much so that you can still turn the distributor with moderate effort.

Back off the timing a smidge.

Test drive and see if the pinging is gone*.

If it is- advance approximately "half a smidge".

Test drive again. Did the ping return?

Yes- back off that half a smidge.

No- you can try to add a "quarter smidge" of timing, or be happy that you are "dang close" , and that the ping is gone.


*if the ping is not gone, retard the timing another smidge or half smidge.
 
I have better luck setting the timing "by ear" to where the specific engine likes it, rather than by the book spec.

Loosen the distributor hold down, but only so much so that you can still turn the distributor with moderate effort.

Back off the timing a smidge.

Test drive and see if the pinging is gone*.

If it is- advance approximately "half a smidge".

Test drive again. Did the ping return?

Yes- back off that half a smidge.

No- you can try to add a "quarter smidge" of timing, or be happy that you are "dang close" , and that the ping is gone.


*if the ping is not gone, retard the timing another smidge or half smidge.
Technical terms! metric or SAE? :lol:
 
Wanted to provide an update as I worked on the car yesterday. Utilizing the amazing timing gun mentioned above I was able to t
This needs to be adjusted properly. The pin on the carb should be at the back of the slot.
Hello, could you please specify a little more? Do you mean in this picture?

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Wanted to provide an update as I worked on the car yesterday. Utilizing the amazing timing gun mentioned above I was able to t

Hello, could you please specify a little more? Do you mean in this picture?

View attachment 1634690
Yes that picture THe pin on the throttle should be at the back of the slot. THe transmission kick down should start moving as soon a s the throttle opens. With the throttle wide open, the kickdown lever on the transmission should be full open. If not the apply pressures will be low and it could cause transmission damage and slippage.

mopar kickdown linkage2.JPG
 
Over the weekend I looked into timing the engine. No matter what degree I moved to pinging occured during normal acceleration with a lite press on the gas pedal. I tried 4 degree before, 6, 8, 10, even 16 with no success. I reset the idle speed on the carb to 750 each time after adjustment, factory spec. After testing again I then disconnected the vacuum control on the factory distributor and the ping went away at normal acceleration and load. Minor ping occurred when I layed into the gas pedal with the vacuum control disconnected. This tells me the vacuum control diaphragm may have failed. I have a new control on order although will likely have to remove the distributor from the engine for replacement. If I do this I might see about having someone put the distributor on a sun machine or equivalent if I can even find someone with an old distributor testing machine. Would you all concur with my current conclusion?

Jon
 
Yes that picture THe pin on the throttle should be at the back of the slot. THe transmission kick down should start moving as soon a s the throttle opens. With the throttle wide open, the kickdown lever on the transmission should be full open. If not the apply pressures will be low and it could cause transmission damage and slippage.

View attachment 1634692
Interesting you mention this as the transmission currently slips between 2nd and 3rd while driving. The previous owner had it the way you see in my previous picture. I will fix this and mimic the exact way your picture shows. I hope the automatic trans is not damaged. Do you have any tips or walk thru on how to adjust this linkage? Looks like the edlebrock has identical set up like your factory carb shown in your picture.

Thanks for your help

Jon
 
Issue 1, timing- you are going the wrong way! Try 0 degrees, that's book spec for my 73 and that's where it likes it.

Issue 2, kickdown- Mike is exactly right. Worse, if you keep driving it like that you will (not might, but WILL) burn out third gear. The throttle cable/kickdown bracket is different between 2 barrel and 4 barrel intakes.
Not sure if a 4 barrel style is available repro, but you should either find one or do some mods to put that throttle pressure in the right place...or you will be rebuilding that transmission...soon.

A length of threaded rod can be welded or "barrel nutted" to extend the linkage.
 
I appreciate the info and response. I will try timing as you mentioned first before removing the distributor for testing. All other degrees failed the ping test. I tested the vacuum pot, it is working and holds vacuum. Regarding the trans kickdown. I will have to get creative as there is no adjustment on this later 1975 edition. Edlebrock sells an adaptor although my issue appears to be the 2bbl clevis rod is too short. Any ideas? Pictures attached of the current set up and the trans slips briefly when shifting into 2nd already. The previous owner had the car this way and may have already ruined the trans. I hope not. Will not be driving again until I fix the kickdown linkage issue.

Jon
 
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