SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: berkbryan on June 25, 2014, 03:26:42 PM
-
I have a small backfire at idle only out of 1 side of the engine when I Rev it it goes away what would cause this
Sent from my SM-G900T using SoCal Jet Boats mobile app
-
Popping through the carburetor or the exhaust?
There are numerous potential causes to a back fire.
Ignition secondary cross talk (arcing in the cap).
Lean miss,
Sticking valve,
Mis. adjusted valves,
Exhaust leak,
Vacuum leak,
Ignition primary issue,
Bent valve,
Cracked valve seat,
Blown head gasket between cylinders,
First thing to, which has zero costs associated, is to do a compression check, be sure this is done with the carburetor full open, no spark.
Second thing to do is a complete ignition system check, plug gap to cap condition.
Third thing is to run it and do a spray test with some carb cleaner looking for a vacuum leak.
Fourth is look for a cracked/leaking header pipe,
Beyond that, I got little/nothing.
GT
-
Popping through the carburetor or the exhaust?
There are numerous potential causes to a back fire.
Ignition secondary cross talk (arcing in the cap).
Lean miss,
Sticking valve,
Mis. adjusted valves,
Exhaust leak,
Vacuum leak,
Ignition primary issue,
Bent valve,
Cracked valve seat,
Blown head gasket between cylinders,
First thing to, which has zero costs associated, is to do a compression check, be sure this is done with the carburetor full open, no spark.
Second thing to do is a complete ignition system check, plug gap to cap condition.
Third thing is to run it and do a spray test with some carb cleaner looking for a vacuum leak.
Fourth is look for a cracked/leaking header pipe,
Beyond that, I got little/nothing.
GT
exhaust and only at idle I did a compression check 125 on all 4 cylinders pulled valve cover don't see anything wrong
Sent from my SM-G900T using SoCal Jet Boats mobile app
-
I did put a new bowl on 1 of my carbs and then it started popping out the exhaust
Sent from my SM-G900T using SoCal Jet Boats mobile app
-
I did put a new bowl on 1 of my carbs and then it started popping out the exhaust
Sent from my SM-G900T using SoCal Jet Boats mobile app
So it didn't pop before the new bowl?
Lean pop.
Find the plugged port in the metering block or put the correct gaskets on and you should be GTG...
GT
-
So it didn't pop before the new bowl?
Lean pop.
Find the plugged port in the metering block or put the correct gaskets on and you should be GTG...
GT
thanks I will try that
Sent from my SM-G900T using SoCal Jet Boats mobile app
-
Well found the problem removed rocker arms so valves were completely closed put 30 psi of air to each cylinder and on # 2 air was just blowing out the exhaust so burnt or bent valve
Sent from my SM-G900T using SoCal Jet Boats mobile app
-
Well there you go... That sucks butt hairs..
Guess what kills exhaust valves?
-
I know I know I know!!!!!
Lean condition!!!!
Sent from my iPhone using SoCalJetBoats
-
I know I know I know!!!!!
Lean condition!!!!
Sent from my iPhone using SoCalJetBoats
What else????? ;)
-
Well found the problem removed rocker arms so valves were completely closed put 30 psi of air to each cylinder and on # 2 air was just blowing out the exhaust so burnt or bent valve
Sent from my SM-G900T using SoCal Jet Boats mobile app
Then how did that cylinder make 125psi during your compression test?
-
Then how did that cylinder make 125psi during your compression test?
my compression tester has a Schrader valve
Sent from my SM-G900T using SoCal Jet Boats mobile app
-
What else????? ;)
would having the timing to advanced do it
Sent from my SM-G900T using SoCal Jet Boats mobile app
-
Rerversion.........
Your compression tester needs to be replaced. ;)
-
Rerversion.........
Your compression tester needs to be replaced. ;)
Funny you bring this up GT, you scared me out of running wet headers when I was putting my motor together. so I ceramic coated them and sealed them up lol.
Sent with my Fingers
-
What else????? ;)
HMMM now your taking me back to my mechanic days!!!
Well lets see,
Valve margin to thin
valve seat cut to deep
sticking valve
I think thats about it.
I have a set of Ka heads if that would help you out. they need to be cleaned up but are complete .
-
Funny you bring this up GT, you scared me out of running wet headers when I was putting my motor together. so I ceramic coated them and sealed them up lol.
Sent with my Fingers
Did you weld the weap holes closed?
GT
Sent from my SGH-T989 using SoCal Jet Boats mobile app
-
HMMM now your taking me back to my mechanic days!!!
Well lets see,
Valve margin to thin
valve seat cut to deep
sticking valve
I think thats about it.
I have a set of Ka heads if that would help you out. they need to be cleaned up but are complete .
thanks for the offer but I have a Ford 460
Sent from my SM-G900T using SoCal Jet Boats mobile app
-
Did you weld the weap holes closed?
GT
Sent from my SGH-T989 using SoCal Jet Boats mobile app
no I did not
Sent from my SM-G900T using SoCal Jet Boats mobile app
-
no I did not
Sent from my SM-G900T using SoCal Jet Boats mobile app
Did you cap the water lines at least?
Cold air can suck right in at lower engine speeds.
Almost sounds like a guide issue, tight guides will do weird stuff.
Get it pulled apart so we can conduct a forensic discussion...
Sorry for the woes.
GT
Sent from my SGH-T989 using SoCal Jet Boats mobile app
-
Did you cap the water lines at least?
Cold air can suck right in at lower engine speeds.
Almost sounds like a guide issue, tight guides will do weird stuff.
Get it pulled apart so we can conduct a forensic discussion...
Sorry for the woes.
GT
Sent from my SGH-T989 using SoCal Jet Boats mobile app
no I did not I will get it pulled apart ASAP boats the never ending projects lol
Sent from my SM-G900T using SoCal Jet Boats mobile app
-
Did you weld the weap holes closed?
GT
Sent from my SGH-T989 using SoCal Jet Boats mobile app
Brass plugs for now. Always a pain since I have to retighten them every day I go out
Sent with my Fingers