Nitro pro stock dragster build thread, boring text as usual :)

My next up and coming project is going to be a scratch built 11.5" wheelbase pro stock nitro dragster some info so far as this unfolds...

looking to make use of my big waste of money carbon fiber pile from working at the rmp hoping to make a full chassis, rear axle pod and front suspension arms minus caster blocks and hubs.

got a free associated .15 tc3 stocker engine with 1.5 degree reduced timing 5 axis cnc milled courtesy of ryan at rb mods in cali boost port opened up a little with some dremel action and an extra .5mm head shim going to run cold turbo plugs os worlds spec heat button and 55% nitro byrons drag fuel

the engine came from a friend and was (broken in) heat cycled by me for 55 minutes at 220f almost no top pinch with massive mid rpm torque too much for a standard touring car but perfect for a lightweight drag platform

will be running a mugen seiki 1/8th scale clutch 26mm flywheel with 4 shoe pins running 2 shoes at 1.1mm springs with aluminum shoes for grabbing action with 1.3mm springs and teflon shoes for rolling grab to minimize wheel spin and maximize launch


looking for pipes and headers hoping to gain some nice back pressure wave on the return cycle to maintain a consistent burn throughout the throttle range.

currently bench testing 35% nitro 5% powemaster vp fuel castor oil running stock carb with no insert os #8 plug and stock header and pipe.

From full throttle to off throttle responds with massive backfire and not enough back pressure under near stall loads with 10x7 master airscrew propeller

need to enlarge boost port some more and add a small carb stack to hopefully stabilize the atomized fuel going in, seems as if the higher nitro content is blowing the fire out on the return stroke hoping to repair this with higher nitro content per crank timing, worst case scenario i may have to cut a knife edge into the connecting rod to minimize internal fuel washing.

once i can get the engine running about 19k rpm with a 10x7 prop with 55% nitro with minimal backfire and no idle up input on cold starts ill order some drag tires and start cutting carbon fiber for the chassis front arms and rear axle pod looking to get about 5000rpm on the wheel with a 2"-3" tire depending on the surface im running on

this is more a fun project to see how far i can push an associated engine before i blow the rod out of the side of the block

also this is not a top speed rig this is built specifically to get to 60+ mph in less than 60 feet is my goal

robot folks please offer your wisdom i appreciate all input good or bad

Unfortunately, I only understood about half of what you said. I'm not a nitro person.

I would go straight to testing the 55% nitro fuel and the heat button glow plugs to achieve more accurate results, though.

Camden W wrote:

Unfortunately, I only understood about half of what you said. I'm not a nitro person.

I would go straight to testing the 55% nitro fuel and the heat button glow plugs to achieve more accurate results, though.

lol sorry about that, your right i do need to test and tune with the final setup to gain a more accurate prospective on what needs to be done.

the fuel is expensive stuff 17 dollars a quart and im going to use at least 2 testing and os turbo plugs are 20 plus dollars for the super cold burn versions

Here's some text then photos to show some of my recent but slow progress on my dragster project

Currently:

Using a re-built hpi super nitro rs4 chassis for engine testing also it was free

Length is currently 8 mm longer wheelbase than my much heavier home-made chassis in progress so setting proper toe in and camber should provide good angles to apply then fine tune when I put together the home made rig.

Still need to figure out how to get rid of the worthless hpi 20 degree caster blocks to keep the front end from feeling like its driving on ice.

Learning how to modify model nitro engines to temporally withstand the internal forces running 55+% nitro methane, from my own experience I have discovered the brass or bronze bushing on the crank side of the connecting rod is what commonly fails running higher than recommended nitro content as have seen many different companies have engines that wear heavily on that bushing or in the case of the traxxas 3.3 engine the rod itself splits when the bushings seize, lol

Several people I drag race with have silly fast cars and swear by adding 1cc of lucas gun oil to every 100cc of fuel and lucas claims it was engineered for guns operating at high temps so it may help.


my buddy ralph had the radar gun out and helped me jot a bunch of data over 7, 75cc tanks today before the rains took over.

testing specs:

with vp 20% fuel 9% oil:

got a 5 run average of 34 miles per hour on foam 35 shore tires with os rp7 plug , consistently rolled a burnout through first gear ruining take off speed and made braking very sketchy

got a 5 run average of 41 miles per hour on pre heated stock super nitro rs4 26mm rubber belted same rp7 plug really smooth braking and no rolling burnouts in first gear all hook.

Then i ran on byrons 50% nitro without lucas oil blew 2 os rp7 plugs just trying to get it to idle somewhat smooth but forgot the rp7 plug was not meant for high nitro content and also forgot the much needed head shims leading to two glow plug’s destruction

With fresh Swapped rp8 plugs and the added recommended head shims but still no lucas oil temps were 13f colder than with the 20% fuel just bench idling, odd right?

well got 5 runs in on same foam tires clocked a 51mph speed it seemed to roll a burnout and hook up even harder in second gear once it was moving

swapped out tires over to hpi super nitro rs4 tires heated them up to a toasty 140f and averaged 56 mph with one odd run of 58 mph witch could have been related to today's weather.

alright enough boring text here some progress photos

overall chassis view with long restrictor manifold


transmission detail 32 pitch gears lots of 5x11 bearings and a great view of the massive two speed assembly.




and rear view




and here's a few sneak pics of the full home made chassis in its current state


engine mount completed looking remove the output gear for a higher top speed and a lower center of gravity but its moving along

still in the cardboard mock up stage for most of the unfinished chassis parts and the decision to use swaybars with independent arms or a solid axle system.