Need help: vortec head swap backfires
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Joined: Jul 2021
Posts: 65
Likes: 3
From: Ridgefield,CT
Need help: vortec head swap backfires
I’ve got a modified ‘87 L-98.
Last thanksgiving one of my original heads cracked.
i replaced stock heads with vortec 906s w/ LS-6gm comp springs- longer spark plugs
scoggins Dickey tpi vortec intake
rebuilt the distributor
replaced the fuel control relay n a thermal fuse
git a new memcal (brain) for the comp from a pro in Canada (specifically for the engine mods)
im putting in new plug wires tomorrow
here is my current status
with the comp connected-
engine backfires hard immediately upon starting n I shut it down.
it surges n then a violent backfire.
with the comp disconnected- the engine idles, minor pops, engine shakes, if I step on gas, minor backfire. You can smell fuel faintly. It’s acting like fuel is not being burned, n it’s misfiring. I’ve tried timing at 6 deg adv- it shakes n backfires worse. Currently it’s at 0 deg advance.
TY
Gary
Last thanksgiving one of my original heads cracked.
i replaced stock heads with vortec 906s w/ LS-6gm comp springs- longer spark plugs
scoggins Dickey tpi vortec intake
rebuilt the distributor
replaced the fuel control relay n a thermal fuse
git a new memcal (brain) for the comp from a pro in Canada (specifically for the engine mods)
im putting in new plug wires tomorrow
here is my current status
with the comp connected-
engine backfires hard immediately upon starting n I shut it down.
it surges n then a violent backfire.
with the comp disconnected- the engine idles, minor pops, engine shakes, if I step on gas, minor backfire. You can smell fuel faintly. It’s acting like fuel is not being burned, n it’s misfiring. I’ve tried timing at 6 deg adv- it shakes n backfires worse. Currently it’s at 0 deg advance.
TY
Gary
Thread Starter
Advanced
Joined: Jul 2021
Posts: 65
Likes: 3
From: Ridgefield,CT
Datalog
FYI: I’ve never done this yet- but I have the gear to datalog. Is someone able to diagnose a datalog without the computer connected. That’s currently the only configuration where motor does not surge n violently backfire.
Thread Starter
Advanced
Joined: Jul 2021
Posts: 65
Likes: 3
From: Ridgefield,CT
Firing order
Firing order is good. 18436572 What’s weird is to set timing I’ve had to rotate distributor cap ccw a lot-the cap section of the electrical connections should be parallel with firewall, but it’s rotated towards front of engine- it’s pointing at no 7 spark plug. Not sure if I need to reset my distributor.
engine is missing- just put new distributor plug wires in/ it’s still missing.
if I touch throttle- engine pops n backfires ( without computer connected)
its worse with comp connected
engine is missing- just put new distributor plug wires in/ it’s still missing.
if I touch throttle- engine pops n backfires ( without computer connected)
its worse with comp connected
