351-W pings badly with vacumn advance hooked up

junkyardjeff · September 28, 2008, 01:39:16 PM

I have a rebuilt 80s 351-W in my 55 sunliner that pings very badly with the vacumn advance hooked up even with premium fuel,its a 80s block and heads with a factory cast iron 4 bbl intake and also has a factory duraspark distributor. Its supposed to have a RV grind cam but has a 302 firing order and has 2.79 gears in the rear end,I have set the timing from 10 degress BTC to almost TDC with the advace at full vacumn and ported with the same results. It runs fine with the vacumn advance disconnecdted and the timiing at 10 to 12 BTC but I heard that a vacumn advance is needed for economy and I am trying to get all I can from this boat before going to a automatic overdrive trans. Its also running a little rich but I did not want to lean it out before I get the pinging proble resolved so is it time for a adjustable vacumn advance or a custom tweeked distributor. Jeff

Charlie Chops 1940 · September 28, 2008, 03:53:04 PM

Jeff,

Do you know what the advance curve is? Check it with a light?

Charlie

enjenjo · September 28, 2008, 07:39:42 PM

All gears or just high gear?

junkyardjeff · September 28, 2008, 08:23:18 PM

It seems to ping in all gears and I am not using a EGR valve,its worse in third with the vacumn hooked up and I have no idea what advance curve it has. Jeff

enjenjo · September 28, 2008, 08:56:21 PM

In most cases I have found that there is just too much compression to run as much advance as you would like. you might be able to connect a knock sensor to that system that would retard the spark when needed, but still allow more advance when the conditions are right.

UGLY OLDS · September 28, 2008, 09:26:06 PM

This is going to sound crazy ....BUT.. Do you have access to an EGR valve to try :?: Like Frank said ..These engines have REAL issues with compression...Installing an EGR valve may cool the combustion charge enough to resolve the issue...As you have found, retarding the timing does nothing but kill the performance ..FAST....
The 351 in my kids Dodge has 9 to 1 compession & requires premium with octane booster added at times ....He still gets a "rattle" in high gear at times....

No amount of tuning or re-jetting on my part has resolved it..... :?

Bob.............

junkyardjeff · September 28, 2008, 09:38:43 PM

If I can find a 4 bbl carb spacer for the EGR I could try it and see what happens,its supposed to have 8.5 to one compression but who knows. It runs great with the vacumn advance disconnected and might stay that way if a solution cant be found. Jeff

wayne petty · September 28, 2008, 10:40:04 PM

do you have a vacuum gauge?

some vacuum hose that fits it... some tees.. does your timing light have an advance knob>>

??
one of the brass HF brake bleeder kits works great for this test also...

can you clean the marks on the balancer... then paint a single line at 10 degrees and another double line on each side of 0..... and see if you can fill in the numbers so you can read them... (that way.. you know which one you are looking at...)

disconnect the vacuum advance.. fire up the motor... set the timing light to 0... see what the base timing is... write that down...

turn the knob till the mark moves to 0... write the number down off the timing light... it should be the same...

have someone bring the rpms up till the timing stop advancing.. while it is held there... turn the knob to bring the mark to 0... let the engine idle... write the number down off the timing light...

set the knob to bring idle timing mark to 0 .. hook up the vacuum hand pump to the advance... pump it up.... quick turn the knob to 0 the timing mark... then let the vacuum off...

write that number down also

if you take those numbers you should be able to see how much mechanical you have and how much vacuum...

you still need to see when the mechanical starts to move and when it stops moving.. ... and when the vacuum starts and when it stops...

then see how much vacuum using a tee is applied at what speed to the vacuum advance ....

you do need a tachometer to do this.. a one built into a digital volt meter or the dash ... as long as you are under the hood and someone is watching the tach... watching the rpms when you move your hand to when it starts moving and when it stops...

i have a 1957 vintage snap on dist-o scope in storage... but i broke one of the tiny neon lamps... after my brother overhauled the electronics... and i have not been able to find any neon guys who can make the tiny bulb.. maybe i will have better luck now that there are more glass blowers here... i have not looked in a decade... the snap on man said.. let him send the 150 pound machine in to the service department... yea sure..

next time i get in the storage that far.. i will roll it out and snap some pictures... it is beautiful... all shiny and red... i was even thinking of calling the peterson and asking them if they want my 1950's shop equipment for their displays... just never got to it... it would be nice as it all came out of a shop less than 2 miles from the peterson..

C9 · September 29, 2008, 08:42:46 AM

Wayne, take a look at an Allied Electronics catalog.

They have a lot of off the wall parts as well as a lot of bulbs.

We ordered from them quite often when I worked for the power company.
(Southern California Edison)

They have a website.

I have a new print catalog as well if you have the bulb number.

IC2 · September 29, 2008, 09:22:46 AM

One thing that none of the other posts mentions tho you make a reference to - a Ford with a Ford dizzy needs PORTED vacuum, not manifold vacuum. You may be in the 20+ degree advance mode even at idle when you should be in the 6 to 8 degree area. Any 351W that I have built has told me very quickly when I use the wrong carb port

and I've done that!!

Another item to check - the vacuum advance can (most of them, anyhow) has an adjustment reached thru the vacuum port. It may need tightening or if it has come unthreaded, the can will then need replacement.