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Old 08-16-2002, 04:40 PM   #1
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Default Using 5 port piston sleeve on MT12/XT12 (long con rod variants) ok?

Hi All ,

The Nova MT12/XT12 is a long con rod design as we all know. And the new 5 port sleeves are used on RS12/RB X12 designs.

Questions are.

1. Is it possible to fit a long con rod on a 5 port piston and sleeve set? has anyone tried this?

2. Are there performance gains from putting a 5 port nova sleeve in a JPMT12? Will it be reliable?

JP parts are very hard to come by locally. Just toying with ideas. I have seen enough discussions in Motorman's forum to think that this may be possible. Please help. Thanks.
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Old 08-16-2002, 05:29 PM   #2
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Well, first off I would think that running a long conrod with a sleeve timed for a short conrod would make the engine not run very well. As for 5-port sleeves in 3-port cases, I don't know for a fact whether this would or wouldn't work. I've been told that the cases for 5-port engines are different to accomodate the additional ports. I guess only someone who's opened up all these engines would be able to tell you. Anyway, good luck in your findings
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Old 08-16-2002, 07:27 PM   #3
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Quote:
Originally posted by rod_b
Well, first off I would think that running a long conrod with a sleeve timed for a short conrod would make the engine not run very well. As for 5-port sleeves in 3-port cases, I don't know for a fact whether this would or wouldn't work. I've been told that the cases for 5-port engines are different to accomodate the additional ports. I guess only someone who's opened up all these engines would be able to tell you. Anyway, good luck in your findings
You raised very good points...but you're right....only someone who's very familiar with the internal workings of engines would be able to answer this matter of factly.

I guess a lot of people with older 3 port engines can stand to gain from knowing this.

If it works, we wouldn't have to buy a new engine to be more competitive...

thanks rod_b!!!
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Old 08-16-2002, 07:31 PM   #4
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I seriously dont see a sleve designed for a short rod working in a long rod engine... the ports would be in all the wrong places..
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Old 08-16-2002, 09:12 PM   #5
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It works ok...I have an RB 5 port in an MT case, obviously you have to change the conrods. I measured up all the heights of the ports and they do match. The piston also bottoms out at the same point. As for performance? I can't really compare because I like the higher torque of the 3 ports so this is the only 5 port I have. Low end torque is down but mid-high end is pretty good, which is what I expect from a 5 port anyway.
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Old 08-16-2002, 10:13 PM   #6
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Well, I stand corrected.
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Old 08-18-2002, 10:46 AM   #7
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Anyone tried converting a 3 port turbo to a 5 port turbo? I understand that for the RB X12 the diferences are only in the sleeve and crankshaft.
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Old 08-18-2002, 04:46 PM   #8
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The new novarossi 5 port block has an air splitter in the transfer ports cast into the case. I am not sure whether the 3 port has this. Apart from that the sleeve is identical in its dimensions. The 5 port crank is different and illegal as well.
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Old 08-18-2002, 08:15 PM   #9
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Yes everything swaps, just use the right rod with the right case and its all good. In a long rod case the liner sits on top of the case in a short rod case it sits almost flush when its installed. Piston and liners are common with 2 exception. I will give you the important one for RE engines. You must use the piston and liner assy with the skirted or cut out area on the bottom of the piston on a short rod engine or it will hit the crank at the bottom of the stroke. You can use a short rod style piston and liner on any long rod nova RE engine. Rods are common as are cranks. Crank timing at the crank is the same between them all. All cranks and bearings interchange. All novarossi cranks are legal as are JP style cranks. All meet Ifmar and ROAR rulesets
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Old 08-18-2002, 09:29 PM   #10
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Quote:
Originally posted by Motorman
Yes everything swaps, just use the right rod with the right case and its all good. In a long rod case the liner sits on top of the case in a short rod case it sits almost flush when its installed. Piston and liners are common with 2 exception. I will give you the important one for RE engines. You must use the piston and liner assy with the skirted or cut out area on the bottom of the piston on a short rod engine or it will hit the crank at the bottom of the stroke. You can use a short rod style piston and liner on any long rod nova RE engine. Rods are common as are cranks. Crank timing at the crank is the same between them all. All cranks and bearings interchange. All novarossi cranks are legal as are JP style cranks. All meet Ifmar and ROAR rulesets
Dennis, by saying Nova / Novarossi, can I take it that you also include NovaMega variants? Does RB also include in this category?

Are NovaMega engines short rod or long rod type? What about RB ones? Thanks
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Old 08-19-2002, 01:23 AM   #11
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Quote:
Originally posted by Motorman
Yes everything swaps, just use the right rod with the right case and its all good. In a long rod case the liner sits on top of the case in a short rod case it sits almost flush when its installed. Piston and liners are common with 2 exception. I will give you the important one for RE engines. You must use the piston and liner assy with the skirted or cut out area on the bottom of the piston on a short rod engine or it will hit the crank at the bottom of the stroke. You can use a short rod style piston and liner on any long rod nova RE engine. Rods are common as are cranks. Crank timing at the crank is the same between them all. All cranks and bearings interchange. All novarossi cranks are legal as are JP style cranks. All meet Ifmar and ROAR rulesets
Wow! A lot of people are very helpful here...but I didn't expect Dennis himself to answer my question...I actually wanted to post this directly to you...but after reading the Motorman forum I was a bit shy to do so.

Thanks so much for the input everyone! Thanks Dennis!

Last edited by Hammer0412; 08-19-2002 at 01:33 AM.
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Old 08-19-2002, 04:05 AM   #12
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No problem.

Nova megas have been short and long rodded, RB's have always been short rods. Mugens are long rods, but are going short rod. Side ports are generally long rods. Yes they fall into novarossi variants.

There have been misconceptions with regards to cranks and these have even been listed in print all over the web that there are long and short STROKE varieties of nova 12 engines. This is simply NOT TRUE. The stroke on them is all the same just the rods are short and long.

The Base timings have not changed at the CRANK windows either, at least not at the crank itself. HOWEVER the short rod engines have about 8 degrees more intake duration that is induced by the shorter rod, this is caused by increased crank angle change over a shorter travel path of the piston in relation to the boost and transfer path openings on the liner. This gives the engine more top end. This is why you will see crank timing changes advertised at times on some sites. THIS is actually true even though the base crank has not changed. This is also why Race engines I have built in the past for people do not have interchangable cranks. My long rod cranks wont swap into a short rod case and run properly because the crank timing will be screwed up. My short rod cranks will swap into the long rod case though and run fine.
However in the case of stock ones they are a direct plug in and go.
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Last edited by Motorman; 08-19-2002 at 04:07 AM.
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Old 08-19-2002, 05:34 AM   #13
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Quote:
Originally posted by Motorman
No problem.

Nova megas have been short and long rodded, RB's have always been short rods. Mugens are long rods, but are going short rod. Side ports are generally long rods. Yes they fall into novarossi variants.

There have been misconceptions with regards to cranks and these have even been listed in print all over the web that there are long and short STROKE varieties of nova 12 engines. This is simply NOT TRUE. The stroke on them is all the same just the rods are short and long.

The Base timings have not changed at the CRANK windows either, at least not at the crank itself. HOWEVER the short rod engines have about 8 degrees more intake duration that is induced by the shorter rod, this is caused by increased crank angle change over a shorter travel path of the piston in relation to the boost and transfer path openings on the liner. This gives the engine more top end. This is why you will see crank timing changes advertised at times on some sites. THIS is actually true even though the base crank has not changed. This is also why Race engines I have built in the past for people do not have interchangable cranks. My long rod cranks wont swap into a short rod case and run properly because the crank timing will be screwed up. My short rod cranks will swap into the long rod case though and run fine.
However in the case of stock ones they are a direct plug in and go.
Just wondering people...why did they have to shift from long rod designs to short? Is it because of the bigger demand in the States and Europe for high RPM engines due to the larger track sizes?

First they spent years with the long rod design starting off with the side exhaust novas and all its variants...

Then they actually spend money to change their production process to accomodate a different con rod design by making it shorter...

Now they have a new Novarossi MR12 (Mugen engine) which is actually seen as a compromise between the two designs...as a sort of best of both worlds thing...

What gives?
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Old 08-20-2002, 08:38 PM   #14
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Quote:
Originally posted by Motorman
No problem.

Nova megas have been short and long rodded, RB's have always been short rods. Mugens are long rods, but are going short rod. Side ports are generally long rods. Yes they fall into novarossi variants.

There have been misconceptions with regards to cranks and these have even been listed in print all over the web that there are long and short STROKE varieties of nova 12 engines. This is simply NOT TRUE. The stroke on them is all the same just the rods are short and long.

The Base timings have not changed at the CRANK windows either, at least not at the crank itself. HOWEVER the short rod engines have about 8 degrees more intake duration that is induced by the shorter rod, this is caused by increased crank angle change over a shorter travel path of the piston in relation to the boost and transfer path openings on the liner. This gives the engine more top end. This is why you will see crank timing changes advertised at times on some sites. THIS is actually true even though the base crank has not changed. This is also why Race engines I have built in the past for people do not have interchangable cranks. My long rod cranks wont swap into a short rod case and run properly because the crank timing will be screwed up. My short rod cranks will swap into the long rod case though and run fine.
However in the case of stock ones they are a direct plug in and go.
Thanks for this valuable info, Dennis It is always interesting to be able to learn new things about the subject that interest you, especially myself coming from a mechanical engineering background.

Anyway, you mentioned about how to differentiate short roded and long roded engines by the piston liners flushed or not flushed fully. How do you mean that it is not flushed fully? My Mega 12RET's liner is slightly not fully flushed to the crank case. Is this a long rod varient? What models of the Megas that are short rodded?

Second question, the 5 port version of the Mega is already out. Have you heard anything about it yet? (MS tuned and non MS tuned). Some feedbacks mentioned that they are going to be better than the Novarossi S5 because they have a different carb. The MS version also has a different crank.

Thirdly, after a days running, should the top of the piston be black in colour or should it be sparkling clean with no deposits on it? I'm using Byron's 25% with Novarossi plug no. 7. Total shims is 0.6 mm (0.3 + 0.3 = 0.6 mm). Ambient temperature is 90 to 100 F with a high humidy of over 90%. Altitude is sea level.

Sorry for being long winded with many questions. Thanks again
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