MSD testing in Northern Illinois?
10-13-2011, 06:35 AM
#12
Registered
This was my problem from earlier this summer. Bad alternators sending too much charge fried the coil. My symptoms were EXACTLY the same...misfire (and rather loud backfire that scared the $hit out of my wife) at high 4k rpms. Found a wet plug first, but that was a result of the coil going bad.
10-13-2011, 04:32 PM
#13
Registered
Thread Starter
New plugs no
New cap and rotor no
New wires/coil wire no
Jetted up no, jetted down no
This is a new combination for him this year, hasn't ran right yet.
New cap and rotor no
New wires/coil wire no
Jetted up no, jetted down no
This is a new combination for him this year, hasn't ran right yet.
10-14-2011, 12:06 PM
#18
Registered
Thread Starter
This is not my boat, just trying to help him out if at all possible. I don't like the compression to start with.
Single engine 26 foot sleekcraft
The motor started out as a 330 motor, upgraded to eagle 496 rotator.
compression 10.5-1
ported rectangle steel heads
single plane intake
850 holley carb
full MSD ignition
CMI tube top headers
stock 454 (330) oil cooler
The cam they recommended was as follows
Hydrolic roller
610/610 lift
230/242 duration
112 center
In the past it ran fine with 10-1 pistons and a nice flat tappet cam in it.
Only updates from last year to this year were 10.5-1 pistons and the roller cam.
Single engine 26 foot sleekcraft
The motor started out as a 330 motor, upgraded to eagle 496 rotator.
compression 10.5-1
ported rectangle steel heads
single plane intake
850 holley carb
full MSD ignition
CMI tube top headers
stock 454 (330) oil cooler
The cam they recommended was as follows
Hydrolic roller
610/610 lift
230/242 duration
112 center
In the past it ran fine with 10-1 pistons and a nice flat tappet cam in it.
Only updates from last year to this year were 10.5-1 pistons and the roller cam.
10-14-2011, 05:15 PM
#19
Registered
iTrader: (3)
Seems like a lot of compression for a iron headed marine engine.
Where is total timing at? Did they replace valvesprings along with the new cam? Rollers are gonna need more spring psi than a flat tappet.
When you say misfire is going on at 4800, how would you explain the miss? I wonder if he is floating the valves...
Where is total timing at? Did they replace valvesprings along with the new cam? Rollers are gonna need more spring psi than a flat tappet.
When you say misfire is going on at 4800, how would you explain the miss? I wonder if he is floating the valves...
10-14-2011, 05:28 PM
#20
Join Date: Jan 2010
Location: Gurnee IL
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Seems like a lot of compression for a iron headed marine engine.
Where is total timing at? Did they replace valvesprings along with the new cam? Rollers are gonna need more spring psi than a flat tappet.
When you say misfire is going on at 4800, how would you explain the miss? I wonder if he is floating the valves...
Where is total timing at? Did they replace valvesprings along with the new cam? Rollers are gonna need more spring psi than a flat tappet.
When you say misfire is going on at 4800, how would you explain the miss? I wonder if he is floating the valves...
