Is the 4.3L an 'Interferrence' motor

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WE7X
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Is the 4.3L an 'Interferrence' motor

Post by WE7X » Sun Nov 24, 2019 6:37 am

My 98 van
If a timing chain breaks, do the pistons usually hit any open valves?
215K, and today the engine started and ran fine for 30 minutes, then was parked for a couple of hours.
Upon returning, the motor did not want to crank, but after a couple of tries, it cranked a couple of seconds and then almost stopped and they spun normal again. That was repeated a few tries, before I had it towed to a shop.
I also noticed the speedometer jumping from 0 to 100 MPH and every place in between at times. The seems like it must be some sort of ignition issue, nut I do not see the connection to the speedometer.
I am prepared for it to be a timing chain, but concerned about potential piston to valve interference, like many foreign motors I am more familiar with.
WE7X aka Rod Johnson
Forest Green Metallic '98 LS AWD
Issaquah, WA

Captn. Crunch
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Re: Is the 4.3L an 'Interferrence' motor

Post by Captn. Crunch » Mon Nov 25, 2019 6:40 pm

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Featured snippet from the web
The GM 4.3L v6 is a non-interference engine in that the valves open into reliefs cut into the pistons such that they will not contact the piston even if the valve is open to max lift with the piston at TDC. As such, if the timing chain has broken, turning the motor over will not harm anything.May 1, 2012
https://blazerforum.com › forum
Captn. Crunch
"I don't beat my rig-I use it to it's maximum potential"
1994 Safari conversion (sold) and miss'n it!
1999 Safari SLE AWD junked
2003 GMC Safari AWD SLT
cast iron Torsen equipped front diff
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Re: Is the 4.3L an 'Interferrence' motor

Post by doyoulikeithere » Sun Dec 01, 2019 2:48 am

You Da Man Crunchy !!
:supz:
2016 Yamaha XSR900 - Silver.
2006 Kawasaki KLR 650 - Red.
1990 Astro - AWD
1987 Astro - With 5 Speed & 4wd.

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Re: Is the 4.3L an 'Interferrence' motor

Post by Captn. Crunch » Thu Dec 05, 2019 2:46 am

Thanks!
I’ve never understood why someone would design something like a zero clearance engine when you don’t have to. Things break-design it to live to fight another day.
Captn. Crunch
"I don't beat my rig-I use it to it's maximum potential"
1994 Safari conversion (sold) and miss'n it!
1999 Safari SLE AWD junked
2003 GMC Safari AWD SLT
cast iron Torsen equipped front diff
S-10 leafs-G80 rear w/3.73’s
2” body lift w/Falken Wildpeak AT’s

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