Need help debugging some unscheduled/unwanted ignition.

[heinz wittenbecher]

I'm in need of some debugging help (again
I'm getting an occasional pop out the air intake. I suspect it's a sticking
intake valve ??

(Using Rance EFI)

I've tried various settings and have tried to monitor (with computer) to see
if mixture is rich/lean just prior to pop but have not been able to pin it
down.

It's been doing the occasional POP ever since rebuilt heads installed, which
were installed same time as the EFI.

'Occasional' means 5-6 pops in 3000 miles. If anything it seems that the
pops occur when under power, but light, i.e. climbing a long gradual hill.
Of course next time it's just cruising along and it pops... perhaps it just
wants to be sure I'm staying awake

BTW, did the 3" exhaust and Flowmasters last week. Definately better
accellaration. Have some pics to post but have to finish building my GMC
computer first to get at my website.

TIA - Heinz - www.bytedesigns.com/gmc
'76 Transmode, Langley, BC

 

[thomas g. warner]

My guess is when they rebuilt your heads they did not put enough valve stem
clearance on one of the valves so when it gets really hot it sticks. If my
memory serves me correctly Joe Mondello has some informtion about it at this
site. http://www.en.com/users/thall/olds/ofind.htm

>I'm in need of some debugging help (again
>I'm getting an occasional pop out the air intake. I suspect it's a sticking
>intake valve ??
>
>(Using Rance EFI)
>
>I've tried various settings and have tried to monitor (with computer) to see
>if mixture is rich/lean just prior to pop but have not been able to pin it
>down.
>
>It's been doing the occasional POP ever since rebuilt heads installed, which
>were installed same time as the EFI.
>
>'Occasional' means 5-6 pops in 3000 miles. If anything it seems that the
>pops occur when under power, but light, i.e. climbing a long gradual hill.
>Of course next time it's just cruising along and it pops... perhaps it just
>wants to be sure I'm staying awake
>
>BTW, did the 3" exhaust and Flowmasters last week. Definately better
>accellaration. Have some pics to post but have to finish building my GMC
>computer first to get at my website.
>
>TIA - Heinz - www.bytedesigns.com/gmc
>'76 Transmode, Langley, BC
>
>
>