Magnum 27 Sedan "Barn Find" in Canada
08-13-2015, 07:56 PM
#21
Registered
Thread Starter
Join Date: Aug 2006
Location: Kingston Ont. Canada
Posts: 76
Likes: 0
Received 0 Likes
on
0 Posts
I've been chasing a problem with the Starboard engine in this boat. It wouldn't pull beyond 3900rpm and would begin to bog. Pulled it and checked lifters, valve lift, leak down test, carb, fuel pump pressure, new hei ignition all to no avail. Finally tonight I decided to switch exhaust manifolds from the other engine to this one and it revs to the moon now! I have isolated it to the mixer on the starboard manifold. It has a little rattle in it when I shake it. Does anyone know what is inside these and how to open them up? I believe they are made of copper and then anodized or chromed ? Can they be heated at the joints and separated?
08-14-2015, 08:22 AM
#22
Gold Member
Gold Member
[ATTACH=CONFIG]542827[/ATTACH][ATTACH=CONFIG]542828[/ATTACH]By the way, did the ad happen to mention rebuilt motors? These things have a pretty nasty idle for 300 hp smallblocks. I have had a couple of them in the past and these ones have way more lope. They also seem to require a ton of juice to crank them over against the compression. My cheap gauge shows 150 psi equal on all 16 but it reads quite low compared to my snap on (which is out on loan right now). My point is these things seem pretty healthy for original 1973 vintage. He also is running 26 pitch props which seem a lot to pull for a pair of 300s. Needless to say Im pretty excited to splash this boat and see if I can break 60+ with her!
08-14-2015, 11:03 AM
#23
Registered
Thread Starter
Join Date: Aug 2006
Location: Kingston Ont. Canada
Posts: 76
Likes: 0
Received 0 Likes
on
0 Posts
I didn't degree or check the cam duration however I did check the lobe lift on the problematic starboard engine. All 16 measured .298 showing the cam has a single pattern .447 lift profile. The pistons are .060 over cast aluminum Speed Pro 345np. Cylinders look like the rebuild is only a few hours old and the leak down and compression #s confirm this. Oil pressure is 40 at idle and climbs to 70 at 4000 rpm.
A wiped cam lobe was my first thought after verifying all fuel related issues and ignition issues. I swapped all parts back and forth with the great running Port engine and had no changes. I swapped fuel pumps and completely isolated the fuel system and ran from a 5 gallon can.
After all this I was about to do a complete tear down and decided to try swapping exhaust manifolds before ripping it down. Instantly the problem switched from the Starboard over to the port engine! I then narrowed it down to which manifold was the offender and then determined that it is the mixer part. I removed it and when I shake it, it actually has a rattle inside. Something is causing a blockage within ! I am pretty good with engines but not welding/brazing so could use some help as to how to remove the solder from the top lid of this mixer for inspection...
A wiped cam lobe was my first thought after verifying all fuel related issues and ignition issues. I swapped all parts back and forth with the great running Port engine and had no changes. I swapped fuel pumps and completely isolated the fuel system and ran from a 5 gallon can.
After all this I was about to do a complete tear down and decided to try swapping exhaust manifolds before ripping it down. Instantly the problem switched from the Starboard over to the port engine! I then narrowed it down to which manifold was the offender and then determined that it is the mixer part. I removed it and when I shake it, it actually has a rattle inside. Something is causing a blockage within ! I am pretty good with engines but not welding/brazing so could use some help as to how to remove the solder from the top lid of this mixer for inspection...
08-14-2015, 01:20 PM
#24
Gold Member
Gold Member
I didn't degree or check the cam duration however I did check the lobe lift on the problematic starboard engine. All 16 measured .298 showing the cam has a single pattern .447 lift profile. The pistons are .060 over cast aluminum Speed Pro 345np. Cylinders look like the rebuild is only a few hours old and the leak down and compression #s confirm this. Oil pressure is 40 at idle and climbs to 70 at 4000 rpm.
A wiped cam lobe was my first thought after verifying all fuel related issues and ignition issues. I swapped all parts back and forth with the great running Port engine and had no changes. I swapped fuel pumps and completely isolated the fuel system and ran from a 5 gallon can.
After all this I was about to do a complete tear down and decided to try swapping exhaust manifolds before ripping it down. Instantly the problem switched from the Starboard over to the port engine! I then narrowed it down to which manifold was the offender and then determined that it is the mixer part. I removed it and when I shake it, it actually has a rattle inside. Something is causing a blockage within ! I am pretty good with engines but not welding/brazing so could use some help as to how to remove the solder from the top lid of this mixer for inspection...
A wiped cam lobe was my first thought after verifying all fuel related issues and ignition issues. I swapped all parts back and forth with the great running Port engine and had no changes. I swapped fuel pumps and completely isolated the fuel system and ran from a 5 gallon can.
After all this I was about to do a complete tear down and decided to try swapping exhaust manifolds before ripping it down. Instantly the problem switched from the Starboard over to the port engine! I then narrowed it down to which manifold was the offender and then determined that it is the mixer part. I removed it and when I shake it, it actually has a rattle inside. Something is causing a blockage within ! I am pretty good with engines but not welding/brazing so could use some help as to how to remove the solder from the top lid of this mixer for inspection...
08-14-2015, 03:35 PM
#26
Registered
Thread Starter
Join Date: Aug 2006
Location: Kingston Ont. Canada
Posts: 76
Likes: 0
Received 0 Likes
on
0 Posts
That's the culprit right there! I have spent many hours trying to figure out why this engine wont take full throttle and finally isolated it to some type of intermittent restriction within that riser.
The close-up is the joint that I would like to separate and inspect the interior for the issue. I think I will try and heat it with a map gas torch and carefully pry it along the edge until it releases. Would love to be back on the water this weekend!
By the way, Thanks H20 for all your help and fascinating old photos ! The classic Magnum bug has bit me and I now understand why all you guys are here!
The close-up is the joint that I would like to separate and inspect the interior for the issue. I think I will try and heat it with a map gas torch and carefully pry it along the edge until it releases. Would love to be back on the water this weekend!
By the way, Thanks H20 for all your help and fascinating old photos ! The classic Magnum bug has bit me and I now understand why all you guys are here!
08-14-2015, 04:36 PM
#27
Registered
Even the dog looks disappointed. I think you are going to need a good sanitary welder. Find a local brew-pub and ask the owner who does their stainless welding.
08-16-2015, 01:12 PM
#29
Registered
Thread Starter
Join Date: Aug 2006
Location: Kingston Ont. Canada
Posts: 76
Likes: 0
Received 0 Likes
on
0 Posts
