I am having trouble with what i think is a slight ping at about cruiseing throttle. it goes away if i let almost all the way off and it goes away (i think) when i get into it.

Im running a rebuilt engine with the small spark plugs. 9.1 to 1 static compression (.040 overbore and .040 off the block)
Im using a megasquirt for port injection and to run my timing.
the odd thing is that the light ping does not seem to depend on my timing settings. I backed off my timing at 45mph cruise by 20 degrees and it still didn't go away.

my only three guesses right now are that my spark plugs could be to hot a range, or the air under the hood is getting too hot, or lastly i have only adjusted the valves once since I built the motor and haven't had a day to to it again yet so could my dynamic compression be way too high somehow?

The spark plugs I am using are NGK ur4.
any ideas?

I would suggest giving the UR-5 a try and see what happens as it's a cooler plug and stock for that type head, I'd only suggest the UR-4 if you were having issues with rich fuel problems or some oil bypass. Also at that throttle/load what is your O2 gauge reading? (Maybe you need a smidge more fuel instead?)

-D.Idiot

I think i will jump to UR6 tomorrow. I'm planning to lightly turbocharge as soon as the kinks are worked out NA. Thanks

I thought I had this happening, it turned out that I had a tiny leak in the exhaust manifold gasket, and it sounded like pinging.

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'81 W150 on Propane... Oversize valves, Oregon Camshaft cam, 10:5 static CR, Distributorless ignition, megajolt timing controller, PowerTrax lockers.

Maybe pull your spark plugs and inspect them.
a blistered plug could indicate a lean/hot condition in a particular cylinder.
this cylinder then runs hotter due to lack of cooling effect of fuel, the hotter cylinder then encourages detonation.
One may be running lean as even fuel distribution on the slant is difficult I believe.(oops just remembered the megasquirt)
just a thought.
Brendan.
Here is a good article on detonation.
http://www.contactmagazine.com/Issue54/ ... asics.html

PS. also try some higher octane fuel or add octane and see what happens.
Extra Hot exhaust valve would encourage detonation too.
that valve lash is looking like a good idea too.
Let us knw how you go.
Brendan.

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1963 AP5 Valiant 225 PB 904 Stock except extractors & 2 1/4 inch exhaust.


1962 S series valiant 225 PB auto. factory every thing. Full restoration job.
Currently on hold till AP5 is on the road.

X2, Use a rubber hose with one end in your ear and the other to listen around each port for a leak. You may get lucky and it's just that.

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Mattelderca
78 NYB (gone now), two S series, three old Snow Cruisers and a Doo.

So it is a slight exhaust leak. But I'm not going to put a new gasket there just yet since i will be replacing it in a couple months when I switch to the exhaust manifold for the turbo.
Thank you all for the help.