engine rebuild-backfire-what I've done so far...
Thread Starter
3rd Gear
Joined: Apr 2004
Posts: 3
Likes: 0
From: West Sacramento CA
engine rebuild-backfire-what I've done so far...
1) compression test. Compression was good in all cylinders and held without bleeding off.
2) timing-started at 4 degrees BTC and went to almost zero. Not much of a change
3) wires- in the correct locations and ok
4) plugs-not fuel fouled..
5) Dist. cap-no cracks
any other ideas?
and- if the compressions ok, does this mean that there are no "tight valves"??
thanks
Russ
2) timing-started at 4 degrees BTC and went to almost zero. Not much of a change
3) wires- in the correct locations and ok
4) plugs-not fuel fouled..
5) Dist. cap-no cracks
any other ideas?
and- if the compressions ok, does this mean that there are no "tight valves"??
thanks
Russ
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: engine rebuild-backfire-what I've done so far... (goshawk)
Backfires occur mainly because the intake valve is open when the plug fires. You need to check carefully that the timing chain is installed with the cam sprocket in the correct position.
Race Director
Joined: Dec 2000
Posts: 17,551
Likes: 26
From: El Paso Texas
Re: engine rebuild-backfire-what I've done so far... (goshawk)
I"m assuming you mean backfire from the intake.
You're positive the distibutor isn't a tooth off or 180 degrees off, and that the firing order is correct? I had a similar situation once and was positive it was right....I was one wire off. Triple check it.
I say this because as you stated "not much change". That means there was some change, correct? Just not enough? I could be wrong (happened once or twice before), but it sounds like your distributor is a tooth or two off. Did you mark the relative positions of the shaft to the body and the body to the intake on disassembly?
You shouldn't have good compression if it was a valve train issue. What procedure did you use to set valve lash?
Ignition coil good?
Tell us what you find out.
You're positive the distibutor isn't a tooth off or 180 degrees off, and that the firing order is correct? I had a similar situation once and was positive it was right....I was one wire off. Triple check it.
I say this because as you stated "not much change". That means there was some change, correct? Just not enough? I could be wrong (happened once or twice before), but it sounds like your distributor is a tooth or two off. Did you mark the relative positions of the shaft to the body and the body to the intake on disassembly?
You shouldn't have good compression if it was a valve train issue. What procedure did you use to set valve lash?
Ignition coil good?
Tell us what you find out.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Re: engine rebuild-backfire-what I've done so far... (goshawk)
Spark plug wires crossed; 5&7 are the most common culprits.
Lifter preload could be too tight. Talk to us about how you adjusted the lifter preload.
Check the "TOOLS" "Tech Tips" section for the procedure I recommend.
Jake
[Modified by JAKE, 9:18 PM 5/7/2004]
Lifter preload could be too tight. Talk to us about how you adjusted the lifter preload.
Check the "TOOLS" "Tech Tips" section for the procedure I recommend.
Jake
[Modified by JAKE, 9:18 PM 5/7/2004]
