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LRP fuel questions (Re post from nitro off road section)

LRP fuel questions (Re post from nitro off road section)

Old 03-14-2015, 08:59 PM
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Default LRP fuel questions (Re post from nitro off road section)

Sorry about re posting, but I failed to notice there is a nitro engine section here. Noob error So, I attempted to break in my new LRP Z.28R Spec 3 today with bad results. It was warm enough outside, about 60 degrees so I though it would be a good day for it. After reading the manual again, I noted that 25% nitro content fuel is recommended. I called around, and not one of the 4 LHS around me carries any 25% fuel. I decided to try some 20% fuel, and order some 25% to try later after the engine is broken in. I bought 1 qt of VP Racing Basher Blend 20% fuel and set out to break her in.

After 10 minutes or so of yanking, I finally got the engine to fire up. I let it idle for a bit with the glow driver on it, then took it off and attempted to drive a bit. The engine loaded up and instantly died. I noticed there was a huge spot of fuel under the pipe stinger where it had idled, so thinking it was set too rich from the factory I re set my needles to factory setting as stated in the manual and tried again. This time it fired right away, but after idling a bit it refused to warm up at all and was still spitting a lot of fuel. I then leaned the high end about 1/4 turn and the low end about 1/4 turn. Again the truck loaded up and died while spitting unburned fuel everywhere. I leaned the low end again and started it, still acting way too rich and still not warming up. I tried to start it again, and the pull start broke. Well, there goes my day of running. Not even 1/4 tank into the break in and I'm ordering a damn pull start already

All said and done I had leaned the high end about 1/2 turn and the low end about 3/4 turn from factory settings, and the engine would not get warmer than 130 degrees and would spit fuel everywhere. It behaved as if it was way, way too rich. Too rich even for break in. I've never experienced this with an engine before. The only thing I can think of is that the fuel I was running is not a good match for this engine. It has a high oil content at 14%, which I though would be ok, but I'm thinking this engine would like a more standard fuel blend such as Byrons Gen2 or O'Donnell speed blend. I know I can run the nitro content higher, but I though I would try the 20% and work up to the 25%, and eventually try the 30% that the LHS stocks.

My question is what is the best fuel for LRP big blocks? Do they run optimally on a higher nitro and get into their optimal temperature range quicker? I have never ran a big block of any brand, so I'm not sure on how they handle nitro content as compared to a small block. Is it normal for a big block to take longer than a minute or two to warm up enough to power the truck? Should I layer the head with several layers of tin foil and put a sock on it too? I have broken in many small block engines up to .18's and never had issues getting them to run warm enough for break in in cooler weather. In fact, the only truck that ran well today was my buddies Nitro Rusty, which ran a nice couple of break in tanks at about 220 to 240 degrees on Byron 20% after I got it going for him on the factory needle settings, and it was running with nothing wrapped around the head at all. Also, assuming I'm running 25% nitro, what plug is recommended? I've always ran O.S. #8 and McCoy #8 in all my engines pretty much year round. What's everyone running in their big blocks, especially any LRP big blocks?

Edit: I forgot to post this before, but the engine was pre heated with a hair dryer to about 110 degrees or so before starting which was as hot as the hair dryer would get it. I had a layer of tin foil on the head as well, but I'm guessing an old sock would work better. The glow plug was also loosened before starting, except once which is why I broke the pull start. Keep in mind that I know how to break in an engine procedure wise, I just can't get this thing warm enough to even start to break it in and am lost as to why that is.

Last edited by Maxximize; 03-14-2015 at 11:12 PM.
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Old 03-15-2015, 02:55 AM
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Default Break in

You dont need to be leaning the main needle yet. I would use a hotter plug just for break in. You need to keep leaning the low speed until you can get it to run.That engine is fast and if it were me I would run 25 % and 11 % oil. Byrons is good fuel if you can get that.
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Old 03-15-2015, 04:37 AM
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I disagree with not touching the main needle. If you leave that to rich you will just end up burying the LSN and still have issues when you try to accelerate.

From the sounds of it you was getting close to having her running but maintaining heat became your concern. Did you wrap the cooling head at all? 60 degrees is still a bit nippy and to run a fair amount of fluid through it and maintain heat you will need to wrap the head.

Pull starts are a pain but if you must have one make certain you are heating the engine well and keeping it warm while starting, and very short strokes. No more than 12 inches.
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Old 03-15-2015, 08:11 PM
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Yea I've got the Byron's 25% on the way. After break in I'll look into moving up to 30% because the LHS stocks that. I think they carry Byrons and Odonell between the 4 near me so I should be good there. For now I'm setting the carb back to factory settings again, and I'll work from there. It was close to running but that fuel seemed to want to keep it too cool with all that oil in it. I did have the head covered in some tin foil, but I don't think that is enough so next time I'll use an old sock and maybe some tin foil as well.

I looked at the pull start before tossing it, and what happened was the knot in the end of the string in the handle pulled through and got sucked into the pull start. When I get the new one I'll put a triple knot in it before trying to use it, hopefully that makes it less likely to pull out of the handle again.
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Old 03-16-2015, 05:58 PM
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Default Tuning

Originally Posted by JoePit View Post
I disagree with not touching the main needle. If you leave that to rich you will just end up burying the LSN and still have issues when you try to accelerate.

From the sounds of it you was getting close to having her running but maintaining heat became your concern. Did you wrap the cooling head at all? 60 degrees is still a bit nippy and to run a fair amount of fluid through it and maintain heat you will need to wrap the head.

Pull starts are a pain but if you must have one make certain you are heating the engine well and keeping it warm while starting, and very short strokes
\. No more than 12 inches.
Lean bottom first until it will run then tune the top.

Last edited by latemodel13; 03-16-2015 at 06:03 PM. Reason: Bad post
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Old 03-21-2015, 02:09 AM
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thaks for the tip there, I'll try leaning the low end out if it won't run on the factory settings again with the new fuel.
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Old 03-21-2015, 06:46 AM
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Many engines won't fire on the factory settings. Just lean in small increments and keep the temp 200+ At 1/4 throttle runs when breaking it in. Also don't be afraid to bump the idle up to get it to run. When it's new it's going to idle high anyway.
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