Rod length

[Jack ODonnell]

Looking for the c/c rod length for the AA45 marine engine.

 

[Brian Sorgente]

39mm (same as the mac 45).

Brian

 

[Steven Bryant]

Same as the VAC 45 aswell

 

[David Murany]

The CMB VAC rod is longer. The CMB HR rod is the same if you can get a hold of one.

 

[Brian Sorgente]

The vac 45 rod is the same length center to center as the mac and AA45. I know this because i have one in my mac. The bottom end of the rod is beefier though in comparison to the original mac rods.

Brian

 

[David Murany]

We put a VAC rod in one of our AA motors and the piston hit the button. With a MAC rod the engine was fine.

 

[Steven Bryant]

I was always told that the VAC and MAC rod were the same I might be wrong but I'm sure I'm not.

 

[Jack ODonnell]

Thanks guys !! J.

 

[David Murany]

39mm (same as the mac 45).

Brian

Brian,

Are these center to center dimensions? I just got home and measured one of ours and got 37.5 MM. I didn't remove the VAC rod to check that one. Would like to figure this out to get ours running again.

Thanks

Dave

 

[Andy Brown]

MAC rod is the same as the AA and VAC @ 39mm. All previous generation CMB 45 rods are shorter.

 

[David Murany]

Ok guys just tore down another AA and the rod is 37.5 MM. I then measured the VAC rod I have and it is in fact 39 MM. So if you want to run a steel rod in an AA you need a MAC crank a CMB HR rod. The VAC rod causes the piston to sub port the exhaust.

 

[Andy Brown]

Ok guys just tore down another AA and the rod is 37.5 MM. I then measured the VAC rod I have and it is in fact 39 MM. So if you want to run a steel rod in an AA you need a MAC crank a CMB HR rod. The VAC rod causes the piston to sub port the exhaust.

I stand corrected on the AA rod length. Thanks David!

 

[Steven Bryant]

David, Double Ace racing products sells a crank for use with the MAC rods, which means the VAC rods will also fit, you might want to have a look at that as it may help you with your engine.

 

[David Murany]

David, Double Ace racing products sells a crank for use with the MAC rods, which means the VAC rods will also fit, you might want to have a look at that as it may help you with your engine.

Yes they sell a crank to use for a steel rod which is a MAC crank. The VAC rod will not work in an AA engine though. It causes the piston skirt to go past the exhaust port on the bottom by about 1 MM. I just had the motor apart and checked it all yesterday. The HR rod is the one that needs to be used.

 

[Steven Bryant]

Ok that's not good for me As I bought one of these cranks a while back to use with a MAC/VAC Rod. I best have a look into it and maybe look at getting a HR rod if that's what it needs.

 

[Andy Brown]

The AA/Rossi Crankcase is shorter than the MAC/VAC crankcases.

A 1.5mm sleeve shim along with case port matching would be required to fit the longer rod in the AA.

 

[Steven Bryant]

Thanks Andy

 

[Brian Sorgente]

Wow I'm glad this came up. I was also planning to put a steel rod in my AA. Thanks for catching this David!

Brian

 

[David Murany]

Ok so we have another development with the steel rod in the AA engine. Just recieved a HR rod and it is too short at 36MM. So it looks like Andys idea of a liner shim with the VAC rod may be the best way to go. Although the case might have to be port matched due to the liner sitting higher. Will post any additional info that I find.

Dave

 

[Andy Brown]

Ok so we have another development with the steel rod in the AA engine. Just recieved a HR rod and it is too short at 36MM. So it looks like Andys idea of a liner shim with the VAC rod may be the best way to go. Although the case might have to be port matched due to the liner sitting higher. Will post any additional info that I find.

Dave

Even when considering the extra work of cutting case ports to match the sleeve ports, the longer rod will be the more practical thing to do. The short rod could work, but the shoulder on the sleeve would need to be cut an extreme amount to correct the timing.