Maximum engine setback of 2% question

[Adam R]

Hello,

Starting the process of dreaming about building a F/DT class truck for Bonneville.  In the rulebook it says you can have a maximum engine setback of 2% of the wheelbase.

My engine plans entail running an in-line 6 cylinder diesel in a mini-truck which normally come with 4 cylinder engines.  In this scenario, the rear portion of the engine is going to be sitting back farther than a stock 4 cylinder and likely by more than 3 or so inches.  Am I overthinking this or how do I calculate how far I can cut into the firewall to make the engine fit behind the stock radiator location. 

Thank you,

Adam

[jdincau]

See the definition of setback on page 58 of the 2020 book. It is measured to the front sparkplug hole.

[Stan Back]

I don't see a problem with having stepfront rather than stepback.  The rule was written (I suppose) to keep from getting the  pickups into an "altered configuration" with added engine setback.  But if you want to not cut back into the cab and have it farther forward than stock, I'd guess that would be okay ? if you made sure of the rules regarding radiators and such.

Before I went that way, I'd sure run it by an actual SCTA official such as Jim Dunn, listed in the back of the rule book.

[Stainless1]

Well the rule really has nothing to do with the firewall... it is about engine placement.  Since you don't have sparkplugs it is the measurement from front spindle traverse centerline to the first cylinder centerline. So if you had a 100 inch wheelbase truck your 1st cylinder center could be back 2 inches from the spindle centerline.
But my opinion is worth the same as all internet babble.... and as much as it pains me to write... take Stan's advice and contact the truck chair for the final answer...

[Stan Back]

. . . and remember, putting more weight on the front ain't like darts ? you might need more out back to keep those tires from spinning.

[Adam R]

O.K.  That helps.  I was afraid that the longer engine would run afoul of this rule.  In measuring out various mini-truck engine compartments, I'm going to need to cut into the firewall a couple of inches to get proper clearance.

Thank you again,

Adam

[wobblywalrus]

Do they make a V-6 diesel?  That might fit without all of the chassis mods.

[jacksoni]

I'm with Stainless, I know nothing. But, to calculate the setback you need to know the "setback" per the rule, (4.AA) of the stock engine. Which may be in front of, on or behind the spindle line. A setback of a different engine  would be with respect to that position.  I think the setback rule came from the circumstance in Altered or CC, where a stock (read V8 mostly) engine is being moved back and how much is being regulated.

This issue came up on my car, in impound, last meet. Was asked if the block plate to which bellhousing mounted, was moved back. My engine was a long 5 cylinder in place of a 4. it was moved forward as much as I could (need the radiator-/GC rules) to avoid cutting the firewall. I think the #1 pllug is forward of the stock location. But they didn't ask that, asked where the back of the motor was. Inspectors.......... 

[Stan Back]

Very interesting.  I'm not surprised.  Inspectors have been known to read things into the rules that are not there ? just like some of us.

I've even had "certifiers" add words to a rule and quote it to a committee head who agreed.  It cost us a record.  No one said it was supposed to be fair.

[rancheroman]

Hey Jack.....this has nothing to do with engine set back....but....what engine are you running now....Paul...

[Stainless1]

Paul, Jack will answer I'm sure, but he is running the coolest out of the box thought engine I've seen in a door car.... 5 cylinder 2 stroke... He has an engine cover made of expansion chamber pipes.... it is wild... but to think of it... so is Jack.... so... just one of those normal car engines you never see in anything...   

[Adam R]

While a V-6 would certainly be shorter, the in-line 6 I plan to use has the most aftermarket support available and overall, packaging is much easier with an in-line engine.  I've been playing with smaller diesels for a number of years and have had pretty good luck wringing decent HP numbers out of them.  My current toy is a '93 Landcruiser running a 3.9L Isuzu with a set of compounds I created backed by a 4L80E.  Currently running 32 lbs of boost as a daily driver, but the smaller turbo is still doing over 50% of the work so there is more power available, but really not necessary for the intended purpose of this vehicle.   Pic should be attached below, but this is NOT the engine I'd use for any LSR effort.  It's too "industrial" for high speed activities, but works great off-road.  I'm currently able to push 22lbs of boost at 1600 rpm and EGT's are hovering around 1200 at WOT.  This pic was taken just before I buttoned everything up and cleaned up some of the loose wiring.  The intercooler pipes were also missing a few clamps at this time as well.

Back on the setback question, I felt better after reading the rulebook.  I'll finish reading the 2020 rulebook from cover to cover over the next few weeks.

Adam

[jacksoni]

So for the past year when the new engine was under development and installation I was pretty quiet about what I was doing. Had to find out if it really worked. Had no actual dyno (did dyno a 2 cylinder mule with my cylinders, carbs, pipes etc) nor actual run the car down a track (had planned to go to ECTA meet in April but that cancelled, and turns out wasn't ready anyway (found out in June at the 2 cyl dyno session that the pipes made in Canada were incorrect and I had to cut them and rework a bunch of stuff to now make the new configuration fit). So speed week was the first outing. Handling problem from coolant tank position, a spin associated with that and then at the end managed to keep it straight for the below noted 194. In addition to the engine and anticipation of better speeds, limited space for big tires and rear gears I had installed a QC. After Speed week I sent the guy who modified the sub frame for that to fit some notes about my times and some photos. We had talked a lot about what I was doing and thought no LSR experience (Drifters and such) were very interested. They put it up on their Facebook page and within a day had about a 1000 hits. To keep this  more or less short I didn't back up the above time, found the reason why when I got home, fixed the coolant tank handling problem and went back for World Finals. With many ambitions which for several reasons didn't happen but did get the G/FAlt record. While there many people stopped by and said" Oh, I saw this on Facebook, the internet or somewhere" Videos now out there too. Anyway, couple photos attached. It is a 5 cyl, 2 stroke based on Arctic Cat snowmobile cylinders. Head and crankcase are billet CNC machined.

[jacksoni]

Engine in place, carbs.

[rancheroman]

All I can say is WOW....good stuff Jack...keep up the good work...Paul..