sschefer
11-18-2009, 01:03 PM
I've recieved a couple of PM's regarding a common problem with these engines so I thought I'd share.
The problem that I'm talking about is that nasty ping at 3500-4000 RPM that occurs after about 10 minutes of running at speed.
This is caused by blown exhaust divert plate gaskets. Three things could cause it.
1. Most commonly the wrong gasket was used durning a rebuild. The gaskets are diverter plate part number specific and there were two different plates used.
2. The excess gasket material used to keep the gaskets form (look like 3/16" wide bridges) when it's cut was not removed during installation and it blew out and tore the gasket. I you see it floatin in the water you know you screwed up.. Ask me how I know:p
3. Too much WOT timing caused high exhaust temp and cooked the gasket.
If you're buying one of these engines and you find it has perma gap plugs like the NGK BU8H or something then it probably has the problem. These plugs will mask it but #4 cylinder will still wash out.
It's an easy problem to fix, only takes an hour. These engines rarely get hot so make sure you're running a 143 thermostat that won't go wide open on you and the gaskets will last longer.
I just made this gasket replacement part of my annual service procedure for the engine. It ranks right up there with the impeller change.
The problem that I'm talking about is that nasty ping at 3500-4000 RPM that occurs after about 10 minutes of running at speed.
This is caused by blown exhaust divert plate gaskets. Three things could cause it.
1. Most commonly the wrong gasket was used durning a rebuild. The gaskets are diverter plate part number specific and there were two different plates used.
2. The excess gasket material used to keep the gaskets form (look like 3/16" wide bridges) when it's cut was not removed during installation and it blew out and tore the gasket. I you see it floatin in the water you know you screwed up.. Ask me how I know:p
3. Too much WOT timing caused high exhaust temp and cooked the gasket.
If you're buying one of these engines and you find it has perma gap plugs like the NGK BU8H or something then it probably has the problem. These plugs will mask it but #4 cylinder will still wash out.
It's an easy problem to fix, only takes an hour. These engines rarely get hot so make sure you're running a 143 thermostat that won't go wide open on you and the gaskets will last longer.
I just made this gasket replacement part of my annual service procedure for the engine. It ranks right up there with the impeller change.