In researching I have come across the term "crossfiring" ...

What is happening is at the lower RPM's I am getting what sounds like detonation when accelerating!!! But not if I am over say 4k then I can mash the heck out of it with now apparent issues

When using the timing light the trailing advances further then the leading this is when I assume the crossing fire is occuring ... the audible sound occurs under load not while free revving

What has been done ...

The points dizzy has been put away and replaced with the FB dizzy (this was done months before this issue started). since this has started have done the wasted spark mod ... attempted to dial in the trailing using the vaccuum advance with no luck at idle it all looks perfect but once revs are brought up we can see that the trailing is ahead of the leading obviously no bueno

Any ideas as to why this is happening and/or how to remedy?

This engine has approx 500 miles on it and hurting it is a sucky option

 

are the vacuum advances hooked up? what timing split are you running?

 

taking the vaccuum off when initially set the timing ... leading at 0 trailing approx 20atdc ... when bring up to approx 4k (as I saw posted in another thread) .... leading at approx 17 to 18ish and trailing climbs to maybe 24ish ... I say ish as I am going by eye ... (not exact science but have a good eye for that type of stuff)

 

Your leading should be up around 24 or so by 4K. Make sure the centrifigal advance in the dizzy
is moving freely for the leading. Sounds like its sticking. Your trailing should be 0 or more degress
less depending on how you want it but it should never be ahead of the leading.

Also describe your ignition setup better. It may help in helping you.

Crossfiring is techinically when one plug fires out of sequence due to current leakages between
wires, either plug wires or dizzy wires. What you have is out of time firing. That sound you
hear is detonation, which is bad but not fatal in an NA setup. Boost, it can kill your engine.

 

Good thinking on the mech advance I'll pull the dizzy and check that out (or at worse swap another one in)

The light from the timing light has an irregular pulse I mean it's pretty consistant but every so often there is a bloop

Ignition, basically replaced the stock coil with a Accel dual ... but didn't make a differance either way ... got the detonation prior and after

 

What brand of spark plug wires are you using?

 

Have you tried getting in a really dark place and inducing the problem while looking for errant spark jumping around under the hood around the plug wires and the coils?

 

NGK ... well now half NGK half Accel


At night with garage door closed various rpm's .... obviously couldn't do for very long before having to air out the garage

 

Try replacing your wires. I battled for years with a bad plug wire. I got a defective new set. I had replaced everything in the ignition system and i broke down and took it to the dealer and it turned out to be a defective wire.

 

Willl give it a try couldn't hurt ...

 

Cross trigerring is an ignition issue, bad plugs or wires 99%

 

lol see "stripped spark plug thread"

 

well I've swapped the dizzy, I didn't like the sight of all the surface rust



and put this one in



vacuum diaphragms appeared fine on both but as I have multiple dizzys hell I'll just swap the whole thing

Not sure what the below hash marks are for but will look into ....



Today I also changed the jets on the Weber 45DCOE .... and took her for a drive much better idle to 8k not a problem ... shift ..... damnit it started detonating again .... repeated this a few time

Not sure if my assumption is faulty ... I've always know detonation to be related with timing .... if I retard the timing any further the car is difficult to start and frankly runs like poo .....

I want to make a trip or two to Socal before and for Sevenstock but now she's religated to being baby'd to the local weekly meets

 

so step 2 is to actually look at what kind of timing you're running. on both leading and trailing, and it needs to be checked at idle and over 4000rpm

 

timing light died between checking idle and over 4k .... can't complain about that have had it for over 20 years ..... whats throwing me off if it rapped through first with no issues ... hmmm harborfreight closes at 9 guess where I'll be heading (sure it won't last me another 20 )

previous problem was it appeared the trailing was advancing greater then the leading

 

make sure you have the ignitors hooked up to the correct ignition half. if the trailing is waste sparked it will cause detonation. the leading trigger is at the front of the distributor, trailing towards the back half. lower plugs get waste sparked via the dual coil, trailing goes through the leading points on the distributor cap.

i normally just tee off the vacuum line so that leading and trailing advance equally, not a significant gain splitting them.

 

What is the condition of the cap? I seem to get crossfiring issues when the cap/rotor go junk.

 

maybe 500 or so miles

 

Ok armed with a new timing light ..... at idle leading 1 to 2 btdc trailing 18ish atdc ... at approx 4500 (no one handy so my 9 yr worked the throttle, yes was kind of scary) trailing roughly 3 btdc ... leading went off the chart ...

I don't have a aftermarket manual persay ... am working with this brown binder I have with maybe a couple of hundred pages like the below ... so re-reading I'll be doing tonight
(not sure if this binder of info is commom and everyone has a copy of it or if is something that needs to be scanned for everyone to have access)

 

hmm you may have to put it on the chart, it should be between 18-24btdc L, split is up to you.

also the trailing vacuum advance advances more than the leading, so if its hooked up the leading needs to be hooked up.

and then the plug wires need to routed so that they aren't touching each other

 

That's not... entirely accurate.

 

lol, no? i thought the trailing is like 15 degrees and the leading is 5 or 7 depending on which dizzy you have?

 

 

Ok so am I missing the boat on how to adjust the timing back at higher RPM's or is this some goofy crap I am dealing with?

I suspect it may be my fail enlighten me

 

Is your pulley on right? It is possible on some years to install in incorrectly.