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351C M-Code engine Timing issue!
#1
On my stock 351C 4V closed chamber M-code engine
4- speed manuel
21 in hg at idle
I run 95 unleaded fuel

Stock dual vacuum diagram distrubutor only hooked up to the advance to portet vacuum on  Carb metering plate/timed vacuum
Idle is 1000 cant go below since timing is so high initial
If i pull the vacuum hose and feel if it suck if i open trottle alittle it doesent do anything. The vacuum canister has been checked its not cracked if i install it at direct manifold vacuum it goes straight to 30’s deg at idle!

I have alot of pinging at WOt

The timing is set at 12 initial and 36 total here it drives great 

If i retard timing to 6 initial no pinging but the throttle response is terrible and it runs really bad, hesitates bogs ect.

Brand new 670 cfm quickfuel brawler carb vac sec stock jets ect

New stock fuelpump
New cap/rotor/plugwires/plugs/ignitor 2 pertronix and a new coil. 
New intake gaskets 

Can anyone help me im really lost here!  I can be the only one expericing this issue


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#2
Similar issues have been discussed several times in the forum. I would do a search, it's in the"More" tab at the top of the page.

Also, please go to the Introduction section, in the "Forums" tab and introduce yourself and your car.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#3
(06-14-2018, 11:48 AM)Meyer Wrote: On my stock 351C 4V closed chamber M-code engine
4- speed manuel
21 in hg at idle
I run 95 unleaded fuel

Stock dual vacuum diagram distrubutor only hooked up to the advance to portet vacuum on  Carb metering plate/timed vacuum
Idle is 1000 cant go below since timing is so high initial
If i pull the vacuum hose and feel if it suck if i open trottle alittle it doesent do anything. The vacuum canister has been checked its not cracked if i install it at direct manifold vacuum it goes straight to 30’s deg at idle!

I have alot of pinging at WOt

The timing is set at 12 initial and 36 total here it drives great 

If i retard timing to 6 initial no pinging but the throttle response is terrible and it runs really bad, hesitates bogs ect.

Brand new 670 cfm quickfuel brawler carb vac sec stock jets ect

New stock fuelpump
New cap/rotor/plugwires/plugs/ignitor 2 pertronix and a new coil. 
New intake gaskets 


Can anyone help me im really lost here!  I can be the only one expericing this issue

MEYER,
Couple of things here,
if your timing is correct, you should not have 21hg of vacuum at idle.
that engine in stock form with great idle quality should produce about 17-17.5 '' of vacuum.
It is possible that the harmonic balancer has slipped somewhat.
Also, your vacuum advance seems a little much.
when I first got my 71, I had that much vacuum at idle, and I knew it was not right.
I found that I had a 2v cam and 4v heads, probably NOT your problem.
how about disconnecting and plugging the vacuum advance for now and see how it runs.
I would see how much timing I could run before it spark knocks.
Also you need to see how much vacuum advance your vacuum canister is supposed to have.
Do you have the older style with the threaded nipple on the advance side ? if so they use washers to control the rare and amount of vacuum advance.
Everything you describe suggests you are getting too much advance.
Boilermaster
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#4
Its a bone stock car checked the adavnce slot today its at the 13L position wich produce 26* Advanced timing initial 12 = 38 total

If i lower it to 10 initial it should produce total 36 wich should be perfect for a 351C but it still pings/knocks!!!

I have the factory double diagram vacuum advance on it no hex in it to adjust only shims/washers
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#5
you have the advance side hooked up to ported vacuum and the retard side unhooked?

Look at this diagram-do you have the thermostatic valve still. If so, you might try this set up.

http://1970mgr.org/302_2V_ImcoACalltrans.gif

If you don't want to try that, is the spare port open? It needs to be to allow the advance to work properly.

Fianlly, you can swap the advance canister for a single port one that is tuneable and may get closer to where you want to be. You\may want to check to see that you dampener hasn't slipped and that your timing numbers are indeed accurate.

[Image: 1_01_07_15_8_53_18.png]

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!
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#6
Meyer, welcome to the forum and as Don C suggested, please tell us about yourself and car in the Welcome section. (if you have not already done so!)
I'm NO expert, don't pretend to be, there are far more knowledgeable members to give advice, but as I too have a 351C 4V 4 speed and had much the same issues getting it to run right, my configuration may help. As well, Boilermaster has good information in his reply above.
So here's what I have for timing, cam, compression, carb and distributor. Rebuilt 351C 4V, .030" over, 10:1 KB 148 dish top pistons, Melling MTF 2 cam, just a tad better lift than stock, Holley 670 Street Avenger carb, similar to yours, and a factory distributor WITH modifications and Pertronix Ignitor II module and matching Flamethorwer coil, (very important!!). My initial timing is 16 degrees with 20* set into the distributor, 10L slot or .410" width for a total mechanical of 36* plus about 6* of vacuum advance running off the timed port on the carb. The vacuum is 17-18 hg hot at idle. Carb jets are 65 primary 67 secondary with a 'heavy' spring in the secondary vacuum motor. The distributor springs are a Mr.Gasket 925D and a factory heavy spring set with just slight free-play. See picture below.
When the motor was first rebuilt, it had 11:1 flat top pistons and I could never get it to run on 91 Shell non ethanol fuel, best I can get here. A subsequent issue gave me an opportunity to drop the comp ratio to 10:1 with cylinder pressure between 195 and 205 psi.
I'll not go into more right now as it could get confusing, but in a nut shell, the results I now have give a strong pulling motor with no ping at all under heavy acceleration. It's all about balance to get it all working together. Your motor may need slightly different settings than mine, no two engines are identical, but you need a place to start.
Good luck with it, keep us informed.
Geoff.
Just read Jeff's post and he has a good point about the vacuum canister, change it to a single adjustable type. There will be a set-screw in the tube for adjustment.


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#7
(06-15-2018, 08:38 AM)Jeff73Mach1 Wrote: Only have advance side hooked up not the retard side






you have the advance side hooked up to ported vacuum and the retard side unhooked?

Look at this diagram-do you have the thermostatic valve still.  If so, you might try this set up.

http://1970mgr.org/302_2V_ImcoACalltrans.gif

If you don't want to try that, is the spare port open?  It needs to be to allow the advance to work properly.

Fianlly, you can swap the advance canister for a single port one that is tuneable and may get closer to where you want to be.  You\may want to check to see that you dampener hasn't slipped and that your timing numbers are indeed accurate.
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#8
If you keep the double vacuum advance, whether or not you are using the ported vacuum switch on the thermostat housing, you need to connect the port at rear of the advance to manifold vacuum, and make sure the front port is connected to the timed (ported) vacuum connection on the distributor.

High initial timing should not prevent your carburetor from idling down. Either something is keeping the primary throttle plates from closing or the secondary throttle plates are not adjusted correctly. Unless, someone drilled holes in the throttle plates, trying to adjust it and drilled too large. I would suspect a vacuum leak, except for your very (too) high vacuum reading. Are you sure your vacuum gauge is accurate?



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#9
(06-15-2018, 12:36 PM)Don C Wrote: If you keep the double vacuum advance, whether or not you are using the ported vacuum switch on the thermostat housing, you need to connect the port at rear of the advance to manifold vacuum, and make sure the front port is connected to the timed (ported) vacuum connection on the distributor.

High initial timing should not prevent your carburetor from idling down. Either something is keeping the primary throttle plates from closing or the secondary throttle plates are not adjusted correctly. Unless, someone drilled holes in the throttle plates, trying to adjust it and drilled too large. I would suspect a vacuum leak, except for your very (too) high vacuum reading. Are you sure your vacuum gauge is accurate?


Are you sure on that Don? It seems to me that if the retard function is getting full vacuum and the advance is getting ported vacuum that the effect of the combination would be to cancel one another out at any time other than idle or cruise. The thermostatic switch was to limit vacuum until the engine heat caused it to open and retard timing was it not?

[Image: 1_01_07_15_8_53_18.png]

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!
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#10
Denmark uses the RON method rating for octane. North America uses (RON+MON)/2, also referred to as AKI. 95 RON= 90 AKI, 99 RON=93AKI. I believe Shell sells 99 RON in Denmark. You might gibe that a try to see if it reduces or eliminates the pinging. How did it behave before the new carburetor? Chuck
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