Serious timing issues

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Jul 29, 2005 | 09:33 PM

adamsre

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From: Eastern, NC

Serious timing issues

OK I have been having some major overheating/timing issues w/ my 71 429. I have a 79 f-150 w/ a 1971 ltd 429 rebuilt engine. I have the duraspark dizzy, edlebrock performer rpm intake, dove-c heads, L&L headers, holley 770 truck avenger, msd 6a box. My truck had a slight ping and hesitation even on premium but ran awesome until I put a weiand alum water pump and L&L brackets on it and hooked up the vac advance (was plugged before). When I did I bumped the dizzy and screwed the timing up. Well to keep it as short as I can after changing the t-stat to a 180 and flushing the sys I still have hesitation and it will always runs hot. I checked the total timing with the base at 10btdc and it was wayyy too high like 48 deg at 2800 rpm. I checked the dizzy and it has a recurve kit w/ 13L slot used. How can I reduce the total timing? I have tried every position of base from 2-30 deg. I can keep it from running hot with the vacuum advance plugged, but it has a bad stumble and will shut off in the road.

Jul 30, 2005 | 03:05 AM

Bear 45/70

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From: Union, Washington

Quote:

Originally Posted by adamsre

First off, did you check the timing with the vacuum hose disconnected? and to the ported vacuum or to the manifold? 10 deg. initial and 13 deg in the dist. (26 deg. at the crank) will give you a total of 36 degs. 10 + (13X2)= 36 which should work ok. It sounds like the vacuum is connected and doing what it will do, advance the timing at low or no load conditions to improve mileage. Check it with vacuum hose off and plugged. I suspect your overheat problem will be gone if you do this or it is caused by something else.

Jul 30, 2005 | 10:32 AM

adamsre

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From: Eastern, NC

I did check w vac hose off and yes I am using the correct vac port on the carb above the throttle plate. I do not get what you are saying to do? This is what I am doing 10 deg w/ vac disconnected and using the 13L slot.

Jul 30, 2005 | 12:38 PM

Bear 45/70

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From: Union, Washington

Quote:

Originally Posted by adamsre

Something is not adding up. 13 deg in the dist will give you 26 deg of advance at the engine crankshaft(at the damper where you are aiming you light. With 10 degs initial advance and 26 deg mechanical advance you have a total advance of 36 degs. If you are getting more than 36 then either the vacuum hose is hooked up while you are checking the total advance (you must disconnect and plug the vacuum hose to the advance unit will check timing) or something is broke in the advance system. The vacuum advance is designed to give you additional timing advance above and beyond the total mechanical advance to improve gas mileage at low load conditions and 48 degrees with no load is not unreasonalbe with the vacuum advance connected. If the dist is in the 18 deg advance slot th you will have 46 degs of advance 10+ (18 X 2) =46. are you sure the dist is using the 13 deg slot?

Jul 30, 2005 | 05:06 PM

adamsre

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From: Eastern, NC

yeah, I have taken the dizzy apart a few times. I just got back from Kragen auto parts with a new dizzy that has a 10L and 15L slot. Could I use the 10L slot and 10-14 deg base timing? I am unsure what the base timing for a 71 ltd 429 is. I think around 10. would it be better to use the 15L and 4-6 base timing? Yes I checked w/ the vac hose off that is why I just bought a new dizzy. I really wanted the crane, but another $370 was not in my budget.

Jul 30, 2005 | 05:51 PM

fasthauler

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From: Hesperia, CA

You might check the vacuum advance diaphram module, Look down into the vacuum port and see if there is an allen head inside. If there is then the degrees of vacuum advance is adjustable. You can adjust it by putting an allen wrench thru the vacuum port. If I remember clockwise decreases the advance, counter clockwise increases it.

Jul 30, 2005 | 10:31 PM

Bear 45/70

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From: Union, Washington

Quote:

Originally Posted by adamsre

Yes you can. If you use the 10 deg slot you can run as much as 16 degs initial advance which. When you change the advance curve it is irrelevant what the factory base timing is. Shorten the advance curve, boost the initial to make up for it. I would still like to know how a 13 degree curve in the dist and 10 initial would cause 18 degs total.