Spark plug gap closed fresh rebuild

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Craig Nedrow

NADAR UNDER THE RADAR
Joined
Sep 1, 2018
Posts
1,102
Reaction score
2,354
Location
Washington State
First Name
Craig
Truck Year
1973 (have two), 1985
Truck Model
K10, K20, C20
Engine Size
350, 454, 6.2 Detroit
I have been the recipient of much good humored help on this forum, but as a machinist, and Like Ricko says "just because it's old, doesn't mean it's bad, and just because it's new, doesn't mean its good. I knew nothing when I started, now I know that, after 60 years of wrenching, 40+ years machining, there is lots to learn. Personally if that was my engine, it would be coming apart. If something has hit the piston, I would not want to find out when a hole has developed and you are oil blowing everywhere. Happened once to me.
 

mlparkey

Junior Member
Joined
Oct 28, 2021
Posts
9
Reaction score
8
Location
Oak Lawn
First Name
Mark
Truck Year
1986
Truck Model
C10
Engine Size
5.7
A spark timing issue is not going to cause that. That's impact damage. The only thing that's going to impact a sparkplug electrode is the piston or something floating around in the cylinder. If you didn't drop that sparkplug before installation then there's a mechanical issue with that cylinder.
 

Nardulli

Supporting Member
Supporting Member
Joined
Jun 18, 2024
Posts
26
Reaction score
45
Location
St Louis
First Name
Jim
Truck Year
1985
Truck Model
C15
Engine Size
350
I didn't notice any chunks hanging around in the cylinder with the bore scope. There was small pock marks on top of the piston and some carbon flakes I believe. What should cranking compression be and do I just remove that plug for the compression test ?
Don't know exactly - but north of 175 psi. Take out all plugs. Crank on each cylinder with the tester installed, let it pulse 4 times. you should not see a variation of more than 10% hole to hole.
 

Cdog_96

Member
Joined
Jan 15, 2022
Posts
46
Reaction score
31
Location
Aiken
First Name
Clay
Truck Year
1983
Truck Model
K10
Engine Size
454
Sorry have been busy, I checked the cylinder and looked good with bore scope. The timing was way too far advanced, the tbi computer was putting it way out of spec. I got the timing right and all is good, plug looks good and no misfires
 

nvrenuf

Full Access Member
Joined
Jul 30, 2010
Posts
1,981
Reaction score
2,522
Location
Mobile, Al.
First Name
John
Truck Year
1991
Truck Model
K5
Engine Size
454
@Cdog_96 Glad it's running good now.

Just to say it, while setting the timing are you disconnecting the wire by the harness bulkhead connector down below the wiper motor / master cylinder? (I think it's tan /white stripe)
 

Cdog_96

Member
Joined
Jan 15, 2022
Posts
46
Reaction score
31
Location
Aiken
First Name
Clay
Truck Year
1983
Truck Model
K10
Engine Size
454
@Cdog_96 Glad it's running good now.

Just to say it, while setting the timing are you disconnecting the wire by the harness bulkhead connector down below the wiper motor / master cylinder? (I think it's tan /white the connector below wiper motor is what I was disconnecting
 

BillK

Member
Joined
Feb 11, 2021
Posts
43
Reaction score
27
Location
Waldorf Md
First Name
Bill
Truck Year
1985
Truck Model
Blazer
Engine Size
350
I'm not an engine builder, but I am not sure how the timing being off will smash a plug like that.

Detonation will close up a plug just like that :(
 

Forum statistics

Threads
44,401
Posts
956,721
Members
36,714
Latest member
MartinK5
Top