Rupp or Chaparral

[sledaholic]

I have 2 engines out of '76 Nitro's. One has a G44BWA, A is stamped and the engine has a nameplate that clarifies it as a Chapparal made by Xenoah formerly Fugi motors and the sled appears to have a different grafic than a normal '76 along with different '77 ish upgrades, the other is a G44BWR engine, casted into the cylinder that says Xenoah. At a glance, the G44BWa has a section of the cast sleeve that overlaps the intake entry. The G44BWR doesn't have this extra rib. Any explanations are appreciated. These sleds were picked up for parts and the sled in question is in the center with black graffix. Thanks! Jeff

[sledaholic]

Sorry I was unable to post a picture.

[Dave]

If you would like to place a nice picture, use the free site listed below to up load your pictures and copy them to here this may help you get better results. But there allot of guys here that probably don't need a picture its just in their DNA.




www.photobucket.com/

[magnumforce]

Hi Jeff, well the Wa is definatley a Chap engine from an SSX? the BWR is a '76 "Rupp" engine, the '77 Nitro was a BW without any extra letters. I don't have any Chap cyls. right now to compare that sleeve overlap is in the lower H.P. motors. It isn't uncommon to see them earlier L/C's installed in the Rupps, When I get a chance I'll try and get a good pic of a '76 BWR and '77 BW Rupp cylinder. If you have a pic on your hard drive there should be enough room left so you can click the Browse button below the subject line and upload it Thanks.

[magnumforce]

Speedway73 can tell you the differance, Roger!! where are you lol..

[magnumforce]

:)Well this bugs me, so I went and took a few pics of the '77 Rupp top end...












1977 piston...


1976 BWR 340

1976 BWR 440 piston

[sledaholic]

Thanks for all your help. I am currently building a '77 Nitro 440 and would like to race this sled in vintage classes in N.H.. Any ideas on what cylinders are the better year. I'm told the '77 bottom end with the '76 cylinders is the best route. I am an engine builder by trade and can see these cylinders would greatly benefit from some porting and possibly changing the port timing with a different base gasket. Any ideas? Thanks! Jeff

[magnumforce]

Hi Jeff I hope these pics helped, your right the '76 top-end on a '77 bottom is a powerful combo with the extra pto brng. on the '77. I'll try and get you a pic of a '76 you can see the differance and being an engine builder you'll understand but I know the '77 cyls make lots of power too ;D here's some pics of a '76 340, basically the same as the 440 the extra sleeve material in the intake port for one thing isn't on the '76's . I suppose they beefed them up for '77-'78 and of course the head is differant from 76-7 you can click on the thumbnails, sorry for the poor quality pics
1976 G34BWR

[440magnum]

I always wondered why the extra crank bearing in 77. Anyone have problems with the 76?

[magnumforce]

I never had any bearing failure or crank issues on any '76, I wonder why they added the extra one. I'm positive Joe V. told me a few years ago when he helped write the HP bulletins they recommended doing that but I'm not 100% sure.

[sledaholic]

Thanks Magnumforce, the pictures are a great help. I was talking with Brian Boucher last night about stuffing the crankcase. I know a friend of my father owned a new '76 Magnum and achieved this. Not being a 2 stroke guru, I will need to research this a little bit. Also curious about performance reeds for these sleds. Thanks! Jeff

[Speedway73]

admin said:

Speedway73 can tell you the differance, Roger!! where are you lol..

YO!! Be careful when searching out BW cylinders. The '77 RUPP cylinders will have G44BW on them....just as Cory has shown.

BUT.....Chaparral 440 L/C cylinders will have G44BW on them also.

The difference you ask??

The Chap cylinders have much SMALLER intake and exhaust ports. The cylinders look identicle when you have 1 of each in each hand. The reed cages,intake boot,water crossover tube and exhaust flanges will all interchange.

I *THINK* the CHAP transfers are smaller too but not sure. I've sold all my Rupp stuff a few years back so I'm going by memory.

[sledaholic]

I have 6 '76 Nitro 440's and 2 '77 440's. Of the 2 engines i've dismantled, 1 is a G44BWa and the other is a G44BWR which both came out of '76 Nitro's. What I'm curious about is the extra rib in the intake port entry that Magnumforce has in the pictures above. What I have noticed already is a definite piston skirt issue with these sleds. Out of the 2 I've dismantled, both have either cracked the skirt in this area or shown extreme wear which appears to be caused by piston rock toward the intake opening. The Chaparral cylinder appears to have attempted to address this issue by incorporating an extra rib to steady the piston through this crossover. I would like to upgrade and attempt to fix some of these apparent issues. I would like to have the skirts of the pistons coated along with the dome, but I have concerns about scuffing on the intake side. Sorry if these are repeated questions that have been observed and answered in the past. As you know, the '76 class is very competetive to say the least. The given is that everyone cheats and nobody tears down these sleds. They will go as far as a compression test around here. Thanks guys. This is a great website! Jeff

[magnumforce]

Thanks Speedway73 and sledaholic your welcome I hope this info was useful in some way. Some day when I ( or any one else) have all the cylinders cleaned I want to trace the ports onto paper and make a port map, scan them and upload them, this should have been done long ago. That's another mod recommended is stuffing the case and balance holes in the crank with cork . Boyessen has 2 stage fiberglass performance reeds for these this sounds like a fun project your doing Jeff, keep us posted take care!