Weird missfire or lean backfire at 6000+RPM
08-06-2004, 09:50 PM
#1
Member
Thread Starter
Join Date: Feb 2004
Location: Canada Quebec
Posts: 150
Likes: 0
Received 0 Likes
on
0 Posts
Car: 88 camaro
Engine: L69 305
Transmission: TH350 3000stall
Axle/Gears: 3.42
Weird missfire or lean backfire at 6000+RPM
I got a problem when i rev my engine past 6000RPM it start to make kind of intake backfire or missfire 
in all gear...The A/R meter still reading ok.Valve float with CC 986 spring on 0.509in and 0.512ex of lift 
bether not...
I got a 355 10.3:1 cc - vortec heads with comp cams 986-16 double spring & shave valve guide-Manley pro flo valves- comp cams XE 268 hyd. flat tappet cam-comp cams full roller 1.6 self align rocker-RPM air gap intake-holley 4150HP 650cfm with 71&73 jets (plugs and A/F guage read ok)-MSD 6AL ignition box set at 7000RPM (and brand new MSD wires-3/8 fuel line -edelbrock victor fuel pump-holley regulator pn:12-803-timing 29deg at 3500Rpm
What could it be
in all gear...The A/R meter still reading ok.Valve float with CC 986 spring on 0.509in and 0.512ex of lift bether not...I got a 355 10.3:1 cc - vortec heads with comp cams 986-16 double spring & shave valve guide-Manley pro flo valves- comp cams XE 268 hyd. flat tappet cam-comp cams full roller 1.6 self align rocker-RPM air gap intake-holley 4150HP 650cfm with 71&73 jets (plugs and A/F guage read ok)-MSD 6AL ignition box set at 7000RPM (and brand new MSD wires-3/8 fuel line -edelbrock victor fuel pump-holley regulator pn:12-803-timing 29deg at 3500Rpm
What could it be
08-06-2004, 10:14 PM
#2
Supreme Member
Join Date: Jan 2002
Location: Valley of the Sun
Posts: 3,852
Likes: 0
Received 0 Likes
on
0 Posts
Car: 82 Z28
Engine: Al LT1 headed LG4 305
Transmission: TH350
Axle/Gears: 3.73 posi with spacer
The stock HEI ignition can't fire the plugs at that high of an RPM. You should really upgrade it if you are going to be spinning that fast.
08-06-2004, 10:18 PM
#3
Supreme Member
Join Date: Apr 2004
Location: Staunton,illinois
Posts: 3,067
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1966 impala , 1998 sebring vert,1978 buick regal turbo, 1991 chevy silverado 3/4ton 4x4 lifted
Engine: 283, 2.5,3.8 turbo 350
Transmission: powerglide,auto overdrive, th350,4L80
yes upgrade the ignition for sure ...and be carefull that you arent floating any valves if your running it up to 6000rpm all the time like that
08-06-2004, 10:20 PM
#4
Member
Thread Starter
Join Date: Feb 2004
Location: Canada Quebec
Posts: 150
Likes: 0
Received 0 Likes
on
0 Posts
Car: 88 camaro
Engine: L69 305
Transmission: TH350 3000stall
Axle/Gears: 3.42
The only stock HEI parts is the ditributor and the pickup coil...The coil is a ACCEL-the stock 4 pin module replace by a MSD 6AL.
Trending Topics
08-06-2004, 11:05 PM
#8
Member
Thread Starter
Join Date: Feb 2004
Location: Canada Quebec
Posts: 150
Likes: 0
Received 0 Likes
on
0 Posts
Car: 88 camaro
Engine: L69 305
Transmission: TH350 3000stall
Axle/Gears: 3.42
Comp cams 986-16
Seat Load: 132# @ 1.750''
Open Load: 280# @ 1.250''
Coil Bind: 1.150''
Seat Load: 132# @ 1.750''
Open Load: 280# @ 1.250''
Coil Bind: 1.150''
Thread
Thread Starter
Forum
Replies
Last Post
