Timing -valves or Ping / rattle normal (1 Viewer)

[sloanstavern]

Howdy – Continuing to refine timing valve and fuel adjustments on ’74 – 40 with an ’86 F2 running a Troll hole carb.

Just adjusted the valves and set the timing to the BB. The engine idles very nice and the power is fine, the only problem is, while warming up to normal range, I get a rattle or ping on hard acceleration under load. No ping if I just rev to 3,000 in neutral, but in gear at mid RPM's 1200-2000 if I stomp on it I hear a loud rattle / ping.

The first thing I thought was pre ignition and was ready to retard the timing a few ticks, but when it gets to full operating temp, it goes away.

Any ideas?
Thanks,

 

[primer7]

What octane gas you using?

 

[sloanstavern]

This last tank is premium ( 91 I think?)

 

[JasonH]

I assume you're using the 86 distributor. How do you have your vacuum advance setup?

 

[sloanstavern]

Yes - '86 electronic dist. It is equiped with two vacum ports, i beleive one is for high alt applications. I have that one pluged and only use the other tied to carb vacum port.

The ping only started with the last round of valve adjustments. I wonder if I am hearing a rocker or something else, but it that is the case, why do I not hear it in neutral reving the engine????

 

[1911]

...when it gets to full operating temp, it goes away.

The ping only started with the last round of valve adjustments.

These two statements make me wonder if you possibly have the valve lash on the loose side, and you are hearing the valve rockers rattle until the valve train expands a little at operating temperature.

But it would be pretty easy to retard the timing slightly and see if the noise goes away - if so, then it is a timing/advance issue. If not, then most likely valve train noise.

Has the engine been de-smogged? After you take the EGR off, a stock distributor will advance too soon (too quickly) for the base timing.

 

[ColonelMustardFJ40]

My 76 has two ports on the distributor vacuum diaphragm. One port (distributor side of the diaphragm) retards the timing and the other advances it. Just a bit of information.

 

[sloanstavern]

Thanks X2

My first hunch was valve lash since it began right after adjustment, but I would expect to hear that druing no load reving of the engine as well.

I have enough touble shooting to keep be busy for an evening

 

[Pin_Head]

Valve lash isn't going to have anything to do with preignition. Preignition is load and throttle related and valve noise isn't.

 

[sloanstavern]

Got it - My chalange is I only hear the noise going at high load in a very noisy topless 40 and I am quite hard of hearing. It sounds llike "ping" at times and also like the "rattle" of a rocker. I may sniff arround with stehoscope and see what I hear when not moving.

F/U question - since I can not seem to get valve setting to stick, I want to re-check rocker assembly Torq- shold rocker assembly be torq'd when cold?
Thanks

 

[sloanstavern]

Appears to be valves. I ran at idle with cover off and went arround with heater hose stehoscope and heard some rattles. Torq was fine, and when I adjusted again much much better.

I think my problem has been I under tightened. Now I adjust so the feeler gauge takes some pressure to get in. Will keep farting arround with it but getting closer.