77 Nitro

[birchy]

 A couple of questions.

- Have 440 Xenoah motors with blue tag (phase 3) and red get (phase 4) on them.   What are the differences?

- I want to run my tunnel protectors all the way to the front of the tunnel and then, in addition, affix a piece on the vertical part of the bulkhead?   Is there any reason why I shouldn't do this?   I understand the necessity of mitering around stovebolts and also ensuring no corner of the vinyl is exposed to snagging.

[mrrupp1]

The blue tag motors are 340 and the red tag motors are 440. As far as the tunnel protectors go, I run my right up to the bulkhead. I'm about 3 inches from the steel. My bulkheads are steel so cleats aren't going hurt it. If you need clearance there your going have to use smaller drivers or roll the chain case. This is just my opinion of course. Clint.

[birchy]

Thanks midnite. my blue tag has a 440 head on it and the right side of the blue tag is so messy I can't read it so a little confusing. After installing the 440 engine I took a rip down my road and twisted the gear right off the aluminium drive shaft. I have a round steel driveshaft that I can install but I want to know if I can get a steel hex shaft with the drivers already on it and in correct position for my 77 nitro. My concern is the round shaft and those press pins.

[mrrupp1]

I have run a lot of liquid Rupps and really haven't had any problems using Rupps stock set up. I have used aluminum and steel drive shafts and never had a problem with either. You want to make sure you use a double wrap roll pin and make sure they sick out on both side of the driver. Far as putting a hex drive shaft in one I'm sure you can do it, but I don't know which model would work. Clint

[birchy]

Thanks Clint. I put approx 100 studs on my track which certainly increased the torque. I will try the round steel shaft. If anyone knows of steel hex drive shaft and drivers that I can modify to fit a 77 nitro let me know.

[mrrupp1]

I have 96 picks in my 76 liquid oval sled with just 2 drivers and it's a Rupp track. Been racing it for 3 years and haven't any problems yet. What I like to do is update to a late model track and run 4 drivers. Works really good. Hope this helps. Clint

[birchy]

Good news. what model track and where can I get the 4 driver shaft set up? I understand that I will most likely need to modify the suspension to align with this new track but hopefully I can continue to use the Rupp suspension. If not then what make/model suspension should I use with this new track?

[mrrupp1]

Birchy, it is pretty easy putting an updated track in a liquid Rupp. Any 121X15X2.52 3/4 lug will work. First thing is you need to move the upper swing arm Idlers in so they run in the middle of the inner drive lugs. Some guys use the 75 Rupp F/A swing arm because it just has one Idler in the middle either one will work. The only other thing you need to do is move the front drivers in to run on the inner lugs. To make it a 4 driver you just add them to the outer part of the drive shaft. You will have to cut the outer lugs off and just use the inner ones. You just have to get two more Rupp drivers. I hope this helps. Clint

[mutt]

If you wait a little while I'm about 90% there on what alternate drive shaft that will fit and still have the speedo work.Then can use a modern driver. Have to confrim it better. And by while mean mid summer. On the stock Nitro swing arm its just as easy and better if you dont want to weld and not into correct nut and bolt restos. Is cut the axels off and drill a hole on both where there were. Then run a bolt through with spacers and can put the wheels anywhere you want for the new track. On a Nitro one cant run one in the center shock mount is there unless you get a very small wheel. The F/A probly has the mount at a different angle.

From what I surmise an Early Polairs 79-81 in a rubber track is a good choice 4-6 inches of travel. Things to look for something thats all contained, all the springs are attached to the suspension. Anything fits but if you go too big the sled looks goofy jacked to much. If I could learn how to post a pic I would show you my fankenstein suspension when i got it its a good laugh

[birchy]

Great info guys....thanks. Mutt.... I can wait until mid summer for that alternate drive shaft info. Please keep me posted. I would rather get a new one that I could add cogs to because I can't get the press pins to move on my current drives....they are seized in there. A few more questions.
- I have several nitros but my current project is a 77 440. compression PSI is around 105 per cylinder. The manual claims 13/1 and with atmospheric pressure here at around 14.5 that means PSI at around 185 ish.... does this make sense?
- Also manual calls for 20 to 1 gas mix. I am using 94 octane with synthetic oil and about 30 to 1 but still appears "oily" meaning black residue around exhaust ports. What mix should I be running? I am asking because someone told me that oil, over past 40 yrs, has greatly improved so old ratios no longer apply.

ps. Clint. I ran my tunnel protectors at 1 1/8 inch deep up to bulkhead and then down both angles of bulkhead steel so completely covered and it is working like a charm....super smooth ride and no chatter. I had to create a custom flathead bolt for the jackshaft support because the stove head one was hitting a stud. Added a second bolt beside it as well (toward the wall)...also custom flathead and voila....silence.

[mrrupp1]

birchy, I mix all my sleds 40 to 1. My race sleds I use 110 leaded and my trail sleds 91 unleaded without enthanol. The race sled is a 76 Nitro liquid cool and my trail sleds are a mix of 76 and 77 Nitro liquids. I have give or take 20 some 76 and 77 Rupp liquids, and 1 76 Magnum. Thats just my Rupp liquid cools, I have about 60 some Rupp sled in all different years and models. Sorry about rambling so much. I just love talking about Rupps. Compression on a good used motor here in Colorado is between 115 to 125. A fresh motor is around 145 to 155. Lower altitude state seem to have a little higher, because there is more air to compress. Glad to here you got your tunnel protectors in. Talk to you soon . Clint

[birchy]

Wow.... quite a collection. I will try 40 to 1 gas mix. At 105 psi it might be time I refresh that motor. I have a kit and a bunch of pistons including some new ones if needed. Truly appreciate your knowledge and info Clint.

[mrrupp1]

Hope some of the info is helpful. The Rupp liquids are my favorite sleds and I love making them run hard. Please keep me posted on your progress with your stuff. Clint

[mutt]

Same here I run all my premix sleds at 40:1 8300-9000 rpm Klotz is my choice. Factory Snocrossers mix a 35:1. I can see a little piston scuff on the clutch side piston through the exhaust port dosnt look into the rings though. I'm 145-147 lbs at 600 ft. might be at 150 if everything was perfect. Rule of thumb you lose 3% for every 1000 ft rise in elevation

[birchy]

 I added a pic of my sled.  Question.   Are you guys using HP3018 length belts?

[mutt]

Man that is nice are you dropped in the front also. Is your hood original gel

[birchy]

Thanks. Yes.... dropped the front a little...due to sorting through springs and finding some with less strength and added a wedge in the suspension keep track flat. Hood is original gel. What are you using for a belt Mutt?

[mutt]

I'm jealous all my sleds are survivors this Rupp is the first one that needs paint. Like a lot of things on my sled things dont add up. Side panels are mint hood is sun burnt purple. Wish I could fine a nice original hood with good color. I'm the wrong guy to ask on the belts. I bought mine as a runner that turned out dosnt run. Went out for a base line run after changing fuel lines and carb change ect. With 8-10-12 inch suspension what ever it is and no shock a bog of coarse came on the pipe. Suspension torqued over to one side and squatted skis up 45 degrees plus, a bad rachet or track rub couldnt tell let off the gas. Though it was going to twist flip it. Scariest 75 ft run of my life limped back to the garage 200 ft run total.

So complete with time bomb clutch has a brand new 1093 max belt. No real run time on it. The sleds scattered all over town now with the shafts in the machine shop and some stuff at the sand blaster. Took me a while to round up some stock suspension pieces wasnt trying that hard. Going to go 108 and reverse cam will be different belt when it get closer to running

[birchy]

LOL... I can relate. Even after putting them together again I have the hardest time trying to align my skis. At speed they tend to dart left/right...scares the crap out of me. Still tweaking that bit. I haven't yet taken a machine rebuild to the point of being a show piece. Basically wire brush or sand blast and then rust paint on the parts and then reassemble using SS bolts/washers/nuts and put them back together and run them. I have not yet participated in vintage drag racing but hope to next year. I installed a freshened and ported 1981 Eltigre 6000 motor into one of my 1976 Alouette Brutes and it is frightening.... still working on the wiring though because AC decided to do some type of reverse closed ground thing that year. I think this will be the machine that gets a newer model track....cause I don't have many originals left in a condition that can handle studs and that kind of torque.

[kerry]

birchy,I read thru your post and your last post about aligning the skis is so true.One of the most obvious things i've run across is the slop in the front spindles/skis on my 74's and 77.The steering arms having those small splines wear and the nut/bolt can never be tightened enough it seems.The spindle hole eggs out where the sleeve is and then rubs the joint of the ski shackle causing another sloppy joint.Spring slides on the skis get worn and can cause extra flexing in the skis too at the front spring point.My suggestion is find the tightest nicest mix for each side and it will help.Would have been nice if Rupp had used a slightly beefier spindle so that the casting could be resleeved with a larger one without sacrificing strength of the spindle.Would be great if someone could forge a bunch of these.I find from riding trails that rupp skis tend to bite a little hard,create drag and grab every thing that wants to pull you off your track.Especially the old wire wheeled and painted ones thast we all seem to be stuck with.This year I ended up putting ski skins on my 74 and it made a significant difference on the trails to the point that I could run at times on a decent trail one handed with littler effort.VERY NICE!Anyway the skins I used are for the standard Polaris steel ski 9002-B (black).There is a little work neccessary to get them to fit well but happy with the overall end result.