Something funny...[Nitro Funny Car build thread]

domtheone

Kind of knew the 2 seater thing would be costly but, i clicked on the link anyway thinking it it was anywhere close to £200 ish, i'd be 100% up for that.

£400 though for a sub 10 second ride  Aye Karumba.

I'll think in it for a year or so

Chevyonfuel

The block in question is a new(ish) billet aluminium block by TFX. The fundamental architecture is that of a 426 block. In terms of actual improvements in design, physically there's not a lot of differences bar some extra ribs in the lifter valley, cross bolted main caps and use of materials that just didn't exist back then (aerospace grade fasteners and the like). Some OEM parts may fit, but a lot of the provision for ancillary parts are removed as they just aren't needed (alternator as an example).

The 426 itself was a winner due to its cylinder head design i.e. hemispherical rather than the typical wedge or heart shape. The ability to burn much more fuel was the primary reason it was adopted for running methanol and nitromethane - it's pretty much a case of 'burn more fuel, make more power'. In the same way, it was the daddy in the other racing disciplines such as NASCAR, and the Chevy motors had no response. Oddly enough, the Chevy blocks were immensely strong, and in aftermarket form, have more cross bolted main caps than a Hemi block does. Chevy and Ford motors just cant breathe that well, so they lost out in the end to the Hemi, which just works perfectly for fuel racing.

In the same way that the 354/392 Hemi became a 417 Donovan (the first race bred aluminium block), the same happened with the 426 when Keith Black started to produce aluminium race blocks. Aside from the lack of water jackets, the race blocks such as this one had critical fixings moved for ease of maintenance between runs, since we'd tear it down to a bare block for inspection purposes and have it ready to fire up within an hour and a half - so whilst you cant really move cylinder head studs, other studs such as manifold ones are located in a way that only 6 are required and the blower / manifold assembly can be off the car within a few seconds.

At present, the billet block I'm using would be classed as state of the art in so much as it's used by NHRA teams in big show fuel racing - there hasn't been anything anything revolutionary in recent years, it's just evolved over time (small things like moving of oil galleries in the lower area of the block to make weld repairs easier when it gets windowed (which they do, often) were realised back in the early 90's. More recently there's been a move towards bigger diameter cams, meaning raised cam tunnels to clear the crank, resulting in various options in terms of block deck height.

Here's the result when it comes to between rounds maintenance - considering F1 teams are praised for changing an engine in a couple of hours...

Chevyonfuel

Quick update:

The short block is finished and largely buttoned up for the time being.
                                                                                                                                                 

There’s a couple of bolt-on bits to add, namely the bottom pulley, idler pulley assembly, oil pump & removable filter assembly.

                                                                                                                                                 
Dry sump oil pump & filter

The filter unscrews for ease of maintenance. Due to nitromethane being such a wonderful fuel, it eats parts, so you’ll often find fine shrapnel in the oil pan after each run, even if it hasn’t lunched a rod or piston. This combined with the reaction between the fuel and oil, mean oil changes after each run are required. The fuel that bypasses the rings, mixes with the oil and essentially turns it into the automotive equivalent of cauliflower cheese. Using an oil stabiliser can help, but it’s a false economy to try and run the same oil again, so it gets a change for every run.

The dry sump pan has seen some life, but will go again and the weld job makes it perfectly usable. As nice as it is to have brand spanking new bits, the ugly looking parts still work; eventually a full beans spare motor will be built, but it’s less financially depressing to hurt pre-loved bits whilst ironing out the bugs and getting a safe, workable tune-up dialled in.

                                                                                                                                                 

That’s about it for the year. In January the pricey bits will become the focus, namely the cylinder heads, rocker assembly, supercharger and fuel system components. I'm quite far behind my own timetable for the build as a whole, but we carry on regardless...

Chevyonfuel

A quick update following Christmas and New Year. It's been a quiet period for myself, real life got in the way of fun stuff, but here's where the build is at the moment.

Just before Christmas, the idler assembly and bottom pulley were mated to the block. That completed the short block, meaning it was time to move on to the top end, where things get a bit fancy.

                                                                                                                                                 
These are early BAE (Brad Anderson Enterprises) billet heads. They're a good choice for this application due to the smaller intake ports and valves. Whilst the current iteration of the heads often come up in classifieds a bit cheaper, they're not the best solution for a small fuel pump, small supercharger combination. I'd previously looked at running updated versions produced by Alan Johnson Performance Engineering, but these Brad's were too good a deal to pass up. The valvetrain; rocker stands, shafts and rocker arms have the advantage of being manufactured by BAE also, so fitment and geometry stands a chance of not being...wonky .

                                                                                                                                                 
The intake manifold is a magnesium item produced by Keith Black Racing Engines. The distribution block and hoses handle the port nozzle fuel requirements. At idle the engine will only take fuel from the injector hat, which equates to around 1.5-2 gallons per minute flow, at around 100psi. The port nozzles come into play under throttle, where fuel pressure rises to just over 300psi, and then the twin nozzles per cylinder play their role (24 nozzles total). There are many ways of distributing fuel in terms of the % that goes through the blower, and that which gets injected via the port nozzles. It gets quite secretive beyond the number of jets as we all have different cubic capacities, cam profiles and compression ratios.

Lastly, the valve covers - these were a nice find as magnesium single plug covers are becoming quite rare. The slotted hole in each is for burn down breathers that help evacuate excess oil, especially in the event of a malfunction. They simply pipe into the top rails of the chassis, and into a puke tank at the rear of the car.

The next things to sort will be the valve train, and then it's onto the blower and fuel injection bits to finish off the motor

RBZ5416

When are you hoping to be race ready?

How do you go about testing before then? I'm assuming you can't rock up to a RWYB with a Fuel motor & burnouts in the local cul-de-sac are probably out of the question! Although saying that, I remember Roz Prior bringing her TF to my local Ford dealer, as part of her Motorcraft sponsorship. Tried a burnout on the dealer's forecourt & it didn't end well. Can't imagine what health & safety would make of that now...

Chevyonfuel

I'd hoped to be ready for the start of 2016, but funds and some other issues mean it's looking more like the end of next year now, I'll keep pecking away at it though - it's more a money than time thing, as a chassis build will only take 8-10 weeks with all the ancillary bits available.

Most of the bigger events have a weekend test & tune event prior. There's the odd mid season test event also. You could appear at a RWYB as long as you gave the track enough notice so they can get their safety guys to bring their full firesuit (they don't have to worry about Saxo's and Fiesta ST's getting BBQ'd, generally ). However, it's unlikely they'd prep the track for just one fuel car. A RWYB would be sledded and prepped for street cars, but it wouldn't be glued - it's too expensive for the limited number of race cars that have only paid their £20 for the day, and for the lesser powered cars, the glue often causes issues like broken diffs and half shafts...

bobflunkit

Loving this thread. Motor looks like a piece of art. I'd be keeping it in my living room, just to stare at.

Chevyonfuel

April update…

The cylinder heads will shortly be returning from the machine shop – the heads previously saw duty fitted to a cast Keith Black block with ½” head studs. The more modern TFX blocks use 9/16” studs so some work was needed to open up the stud bores (only by a knats). The valvetrain assembly is run of the mill race spec Hemi stuff – shaft mounted rocker stands, shafts and heavy duty rocker arms. Spring pressures are circa 350lbs static and just over 1000lbs at peak (not at high as some weapons grade methanol burning engines but sufficient in this application).

Onto the supercharger – it’s nothing exotic, just a standard race spec billet rotor 6/71 roots unit with teflon and nylatron striping on the rotor tips.

                                                                                                                                                 

Due to the inlet being a predefined size, the fuel distribution in the traditional layout isn't optimal (4 injectors each side of the injector hat, feeding into the top of the blower). The 3 holes towards the rear of the blower case provide the option to inject some fuel to the rear end of the blower casing (in this case, a pair of jets, one each side of the casing). Due to the nature of roots blowers making a lot of heat and becoming quite inefficient at higher overdrive, the fuel that can get to the back of the blower, helps cool the intake charge and keep temperature down.

As we're limited to a specific supercharger size, rotor type and overdrive (18.99% max OD), the only option available to make a difference is to make boost at as low an overdrive as you can. Less heat production equates to cooler intake charge and more power. Simply upping the overdrive only works to a point. The holy grail of modern nostalgia blowers (slight irony in terms there) is a billet case, billet rotor'd design with some CFD developed innards. These however sit at around the $6-7.5k mark versus my little blue BDS at $3k. They make serious amounts of boost (33psi at the hit of the throttle), but mean some clever tinkering is required in the fuel system to make air fuel ratios workable. For the time being, this should do the trick.

                                                                                                                                                 

As per most race grade blowers, this one features a delta bottom opening, discharging to the front of the case. In recent years, to assist in equalizing the manifold pressure to all cylinders, setback manifolds which physically locate the blower further back on the manifold, have been common (the trade-off being needing to use a longer snout between the blower and top pulley).

More photos and waffle in a few weeks when the heads should be installed and work starts on piecing together the fuel system.

Chevyonfuel

Quick update, a mock-up for the motor as is - the blower might still change, and the barrel valve for the injector needs swapping out for a k-valve, but it's getting there slowly.

                                                                                                                                                 

The list of to do bits for the engine reduces every few months, most of the big hardware's nearly done, next up will be the fuel system and ignition system.

rousetafarian

I am not sure what the hell I'm looking at but I like it, I like it a lot!