49.9ci VS. 56.1ci

[lilwhirlwind]

Okay...

First

I have a 13 ft. Critchfield with a 56 ci ported to sst60 specs. Im turning 7400 with a 23 pitch clever. Sound about right?

Second
I am about to build another 3 cylinder OMC.. only thing is I don't know which to build. I have 3 49ci motors. and 1 fresh 56ci block. Most everyone I talk to screams 56 is the way to go!! ... on the other hand I just talked to another group of guys from Canada that run only the 49's. Then just today a group of guys from Alabama running the 49's. Their reason is the 56's have heavier pistons and break rods often. (yet to happen to me) but I hear the 56's have more bottom end. Having never compared the 2 to see.

With the 49's I have more room for error because I have 3 to play with.. idk.. Just looking for some input.

Third lol

Which ever motor you guys prefer.. Give me a tip or 2 on building her


You guys are always very helpful. Thanks in advance !!!!!

[LittleCharger]

Okay...

First

I have a 13 ft. Critchfield with a 56 ci ported to sst60 specs. Im turning 7400 with a 23 pitch clever. Sound about right?

Second
I am about to build another 3 cylinder OMC.. only thing is I don't know which to build. I have 3 49ci motors. and 1 fresh 56ci block. Most everyone I talk to screams 56 is the way to go!! ... on the other hand I just talked to another group of guys from Canada that run only the 49's. Then just today a group of guys from Alabama running the 49's. Their reason is the 56's have heavier pistons and break rods often. (yet to happen to me) but I hear the 56's have more bottom end. Having never compared the 2 to see.

With the 49's I have more room for error because I have 3 to play with.. idk.. Just looking for some input.

Third lol

Which ever motor you guys prefer.. Give me a tip or 2 on building her


You guys are always very helpful. Thanks in advance !!!!!

Rpm sounds ok maybe a little high....are you hooking up...what kinda speed you getting?

I'd build another 56er...that's all we race up here and the 49er is eligible for the class and the last racer converted to a 56er and lit the course up.

What guys in Canada are only running the 49er. Like I said all the OMC racers up here are running 56ers.

I've never heard about issues with the rods on the 56er and never seen one with that issue.

[lilwhirlwind]

Rpm sounds ok maybe a little high....are you hooking up...what kinda speed you getting?

I'd build another 56er...that's all we race up here and the 49er is eligible for the class and the last racer converted to a 56er and lit the course up.

What guys in Canada are only running the 49er. Like I said all the OMC racers up here are running 56ers.

I've never heard about issues with the rods on the 56er and never seen one with that issue.

73-74gps

[Steves Jem]

Lilwhirlwind
Between the late 1970's to the mid 90's I use to race a Mono of my own design in Australia with the stock 49ci Hustler/Stinger. 49 ci FT19S, 56ci SST 60 and 56 ci finger ported with the 31M front and Dual Throat 1 in carbys. The stock 49 ci would turn 6,500 rpm with a 23 in cleaver with a speed of 72-74 mph. The FT 19s would turn 7,500 with the same prop for a speed of 78-80 mph. When I updated to the stock 56 ci SST 60 would turn 7,300 rpm with a speed of 77-78 mph. The modified 56 ci with the 31M front would turn 8,400 rpm with a speed of 90-92 mph. I experimented with 1 3/8 duel throat carbys for the modified 56 ci but had to modify the butterfly's as engine would idle at 7,000 rpm. I never got the jetting right with these carbys as engine was prone to flooding as twice the amount of fuel was used. Although the engine had heaps of grunt and would acceleration out of the hole straight to over 7,000 rpm, the engine ran lean and destroyed a piston. I never had any problem with the rods on a 56 ci only the head as when shaved too much the head would start to crack and warp. I found out the maximum to shave was 0.040 off the standard SST 60 head giving the combustion depth of 0.400. You had to also change the tel tale to come out of the thermostat cover as per the service bulletin otherwise engine would lock up over 7,500 rpm. Depending on what work you intend to do would then determine which block to use. If you only consider minimal changes then I would be going for the 56 ci oval ported block.

Stephen Medaris

First

I have a 13 ft. Critchfield with a 56 ci ported to sst60 specs. Im turning 7400 with a 23 pitch clever. Sound about right?

Second
I am about to build another 3 cylinder OMC.. only thing is I don't know which to build. I have 3 49ci motors. and 1 fresh 56ci block. Most everyone I talk to screams 56 is the way to go!! ... on the other hand I just talked to another group of guys from Canada that run only the 49's. Then just today a group of guys from Alabama running the 49's. Their reason is the 56's have heavier pistons and break rods often. (yet to happen to me) but I hear the 56's have more bottom end. Having never compared the 2 to see.

With the 49's I have more room for error because I have 3 to play with.. idk.. Just looking for some input.

Third lol

Which ever motor you guys prefer.. Give me a tip or 2 on building her


You guys are always very helpful. Thanks in advance !!!!![/QUOTE]

[LittleCharger]

Some great input Stephen! Thanks

[Powerabout]

I guess working from the top its 31M ( custom block) Mod 50 ( based on a 49er) then the rest.
The fact that you have huge behind the liner ports and access to all the exhaust system made the MOD 50 49 case a better engine as its highly modded ( that includes rods longer then the 56er )
Then there is vee bottom and tunnel boats and usually what is best on a tunnel is not best on a vee bottom, then you have kilo's and drags, lots of choice for an engine build.

[Fast Fred]

would be interested in any service bulletin info you have on the FT-19s, would also be a buyer for a ft-19s parts book...

[Fast Fred]

hears some 1 and 3/16 Mod 50 carbs,

[lilwhirlwind]

[QUOTE=Steves Jem;142785]Lilwhirlwind
Between the late 1970's to the mid 90's I use to race a Mono of my own design in Australia with the stock 49ci Hustler/Stinger. 49 ci FT19S, 56ci SST 60 and 56 ci finger ported with the 31M front and Dual Throat 1 in carbys. The stock 49 ci would turn 6,500 rpm with a 23 in cleaver with a speed of 72-74 mph. The FT 19s would turn 7,500 with the same prop for a speed of 78-80 mph. When I updated to the stock 56 ci SST 60 would turn 7,300 rpm with a speed of 77-78 mph. The modified 56 ci with the 31M front would turn 8,400 rpm with a speed of 90-92 mph. I experimented with 1 3/8 duel throat carbys for the modified 56 ci but had to modify the butterfly's as engine would idle at 7,000 rpm. I never got the jetting right with these carbys as engine was prone to flooding as twice the amount of fuel was used. Although the engine had heaps of grunt and would acceleration out of the hole straight to over 7,000 rpm, the engine ran lean and destroyed a piston. I never had any problem with the rods on a 56 ci only the head as when shaved too much the head would start to crack and warp. I found out the maximum to shave was 0.040 off the standard SST 60 head giving the combustion depth of 0.400. You had to also change the tel tale to come out of the thermostat cover as per the service bulletin otherwise engine would lock up over 7,500 rpm. Depending on what work you intend to do would then determine which block to use. If you only consider minimal changes then I would be going for the 56 ci oval ported block.

Stephen Medaris



Thanks a lot for the feedback man. That has helped me decide on the 56. tho I still would like to build a 49 in the near future. That 56 block needs to be build first.

This is why I love this forum. You guys really know your stuff and are always willing to lend knowledge. Very much appreciated

[Steves Jem]

Fast Fred
I have a FT parts manual that I could scan and forward to you. Just send me your E-Mail address and once scanned will forward to that address.

Stephen Medaris