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512 cid C series on Dakota chassis- build thread


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Personally I think it is overkill...you are not running injectors where a low fuel cell and slosh my result in a misfire....the float and reservoir in your carb will prevent this.   I do not know what tank you using...have not followed this thread close....but multi corner taps to a reservoir them feed the pump from there would be more than sufficient even though I think this is still overkill for a street vehicle...9 out 10 not even necessary for track where any carb is used.

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So with the holley sniper kit it is an EFI throttle body setup so I definitely don’t want to uncover my fuel sender pickup when the fuel is low and sloshes. It will stutter and stall for sure and I want to avoid that problem.

 

The sniper meters fuel based on generic tables generated by initial input parameters (# of cyls, CID, cam type, target idle speed) and then self learns and adjusts as you drive based on a wideband O2 sensor. Kind of like an early 90s factory tbi but universal. You can set target AFRs for different situations too- whatever your motor likes or needs. 

 

I ordered the ‘master kit’ which comes with an inline fuel pump, pre & post filters, efi hose, clamps, etc. I also got a 0-100 psi gauge to put in the engine bay to make sure the input pressure doesn’t dip and cause otherwise hard to diagnose problems. 

 

The throttle body has an internal fuel pressure regulator at 58 psi and needs a 3/8” return line that runs at 0-3 psi. The return line is easy- I have a capped off return bung in my tank already that will dump circulated fuel back into the main reserve of fuel in the bottom of the tank so it doesn’t spray out and aerate the whole supply. I definitly want the flow of fuel to run back to the main tank. Running a small amount of your fuel in a circle is a no-no. It would heat it up much more than returning it to the main tank. 

 

The plan is to also later let the sniper run the ignition timing with a locked out distributor- you send the magnetic or hall effect distributor signal to the ecu in the throttle body and one wire out to trigger the capacitive discharge ignition (msd box). You lock out the distributor at 15° and the ecu will retard and advance it- kinda like a lean burn setup. You can set cruise timing, WOT, and initial with the handheld or dash mounted touch screen or hook up a laptop for more detailed control of the curve. It can also switch a relay for my electric fan and it has an internal relay with +12v out for the high pressure fuel pump. 

 

So I already have a brand new perfectly good tank that fills nicely, holds a decent amount of gas, and fed my thirsty 950 carb just fine but the pickup is on the right side and maybe 1/4 forward of the rear of the tank. It’ll probably never have a problem if I stay above a half tank but I suspect my 512 will be thirsty. I don’t want to mess with my tank because it works and I don’t weld aluminumim but I can weld vessels in steel so a custom made surge tank would be basically free.

 

The problem with it is even though it will be small- like less than a gallon- I need it to fill with fuel as high as possible. So it needs a vent at the top, gravity feed to the EFI pump at the bottom, and an input probably at the bottom too. 

 

My conundrum is where to send the surge tank vent. If I send it to a tee in the sniper return line will it interfere with the return or create problems with the recirculation? 

 

And if I decide to use the stock mechanical pump to fill my surge tank it means a little more plumbing but less electronic stuff. Plus the diaphram pump is better in suction than electric pumps that can only push gas and the mech pump won’t burn out either...

 

Sorry for writing a novel but there it is. I just want it to work without hiccups and put in a little extra effort while the chassis is bare and I’m not rolling around in the dirt.

 

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Edited by Radarsonwheels
Added fuel cell pic
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Ha! It just  came to me- how to get a second vent into the bottom of the tank! I can make a metal fitting sleeved into the filler neck that turns down inside the end of the filler and extends down into the bottom. That way I don’t have to tee the surge vent into the throttle body return line. 

 

I’m gonna need another roll of 3/8” steel hard line and a big box of peco clamps but I am confident I can do a clean installation.

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It’s raining today- no chassis work. 

I started patching the floorboards in the garage though. The trans is still on the bench but it’s all buttoned up with the torque converter installed so I’m not so worried about kicking up dust anymore.

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Thanks NYer!

 

I screwed the patched but banana’d boards down flat to the supports with self tappers and shrunk the waves with ox/a, hammer, and compressed air until they were acceptably flat with no oil canning on the step areas, then flipped them over and applied a heavy coat of XO-rust gloss exterior enamel to the bottoms. Should be a while before they start rusting again!

 

My sniper throttle body kit came in the mail yesterday. I’m still waiting for some weld on hosebarb bungs to come in the mail before I start fabricating the surge tank and brackets to hang the electric fuel pumps. 

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I’m considering doing the board tops and bumpers with the gloss black oil paint. 

edit: I painted the board brackets and the tops of the boards too. That way I can screw them down tomorrow and not have to take them off to paint the rest of the frame. I’m a little nervous about the self tapping screw’s holding power but they’re stainless and all their threaded holes in the brackets are slathered in oil paint so corrosion won’t be an issue and even if they’re tucked in I should be able to get a 5/16” wrench on em from the side

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Edited by Radarsonwheels
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I ordered a nut-sert tool and a pile of 1/4-20 rivnuts to do a better job attaching the running boards. The self tapping screws are cheesy and I don’t trust them to hold up long term but they sure are perfect for locating and making perfect pilot holes! 

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I got the driver’s side header off and dinged it for a little steering shaft clearance. The scratch/rub on it made getting the dent in the riight spot pretty easy. I ordered new percy’s collector gaskets. Everything has to be sealed up perfect for the o2 sensor that the sniper uses in closed loop self learning mode. The sniper comes with a clamp on O2 sensor bung which is pretty fancy but I had to order 3” clamps and relax the radius on the plate to fit it on my downpipe. I did pick a spot and drill the hole for it though. So easy with no cab in the way.

 

The sparkplugs are a snap to change with no fenders or exhaust plus I wanted a fresh set for the efi swap. I am really happy with the read on the old ones- it was burning really clean with no detonation and it looks like my rings are seating nicely too. 

 

l cut and drilled a 3/16” plate to shim up the passenger side motor mount for a hair of clearance between the header and the upper control arm pivot without major driveline angle change. Boy was it hard to get that sucker back in there! Now the motor mounts are both torqued tight on the main bolts and block ears too. I trimmed back the flange on the UCA pivot a little more too with the die grinder while I was at the clearance game.

 

While I had the die grinder out I slotted the central mounting holes for the rad support and front fenders by 1/4”or so. When it was last together the passenger side front fender was 1/8’ or 3/16’ farther from the tire than the driver’s side and I was out of adjustment on that mount. Maybe I’ll weld in washers once it’s perfect but it was really close and the bumper is centered well too so the struts can be centered in their little archways to get it on point.

 

I also cut a couple 3/8 coarse bolts down to little nubs to use holley’s recommended power hookup on the side +&- terminals of the battery while the rest of the car runs off the top terminals and got ring terminals and 12g wire to extend the harness to the rear mount battery. 

 

Apparently my passenger downpipe is not aluminized tubing and is already getting some nice surface rust. I’ll have to scotchbrite it and get some hi-temp paint so it’ll last a couple years.

 

So mostly I took stuff apart today but at least I’m moving down the list getting closer to firing it back up badder than ever.

 

 

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Wow amazon to the rescue my rivnuts and gun came at like 9:00 this morning! I’m about to go open my shop at noon but I had time to go replace the self tappers with the rivnuts. The screws left perfectly aligned pilot holes and the nuts slipped snug into 9mm holes. Glad I had metric bits around from some com-bloc projects. 

 

I had black oxide 1/4”-20 x 1” allens and stainless washers laying around so that’s what I used. They don’t seem to be eyesores I might keep em or I might do screws or bolts. Screws would be impossible to re-torque in the future and bolts would need paint... probably call it done and not get in the weeds when it works great as is. 

 

Plus I can see myself using the rivnut tool all over the place where there once were cheesy self tappers- it was a good investment.

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6 hours ago, Radarsonwheels said:

Wow amazon to the rescue my rivnuts and gun came at like 9:00 this morning! I’m about to go open my shop at noon but I had time to go replace the self tappers with the rivnuts. The screws left perfectly aligned pilot holes and the nuts slipped snug into 9mm holes. Glad I had metric bits around from some com-bloc projects. 

 

I had black oxide 1/4”-20 x 1” allens and stainless washers laying around so that’s what I used. They don’t seem to be eyesores I might keep em or I might do screws or bolts. Screws would be impossible to re-torque in the future and bolts would need paint... probably call it done and not get in the weeds when it works great as is. 

 

Plus I can see myself using the rivnut tool all over the place where there once were cheesy self tappers- it was a good investment.

 

 

Will you post the link or part # of what you ordered?

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Great to hear the nut rivit tool worked out. I have been trying to justify buying one for a couple of years now. Since I cut the firewall in my truck, I want to make a removable panel to access the distributor. The rivit nuts would really simplify that process. 

 

The running boards came out great. One thing leads to another and, before you know it, you have a shiny new truck.

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Thanks Jomani! I made a custom tool to reach the hold down bolt on my ramcharger’s smallblock distributor. The standard L shaped 1/2” distributor wrench that goes on a ratchet worked fine on my A body smallblock hotrods but for some reason on the rc it is super tight around the firewall and vac advance can. Just an idea maybe it’ll help with yours. 

 

I have been busy collecting parts for my efi fuel system. I have the carter 4-6 psi lift pump, some good fuel hose to replace the short 1/2” sections that come off the fuel cell -8 fittings (apparently I used breather or heater hose what was I thinking?!). I used brass male-male reducers to 3/8” after that. 

 

If it is nice enough next week I’m planning to lay out my routing, fabricate the surge tank, and make brackets to hold the pumps filters and lines just below the tank.

 

I had been nervous that the efi throttle body would have fitment issues with the firewall. It has three different spots to choose from for the fuel inlet but the return line is on the rear passenger side and faces rearward. I could theoretically install it backwards and have the cable linkages wrap to the front or weld a pocket in the firewall for clearance but either way sucks. I can’t mock it up for clearance because the cab is not installed. I thought it had a good chance of fitting since my carb’s fuel bowl tucks under the firewall/cowl and the sniper is more fat width wise and obviously doesn’t have fuel bowls but the uncertainty was nagging me. Technology to the rescue! Here’s a photo mock up from my pics and google image on my ipad. It looks like it’s gonna work!

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Happy easter y’all! Got my 3” clamps in the mail and set up the wideband bung for the efi. Also finally got around to mounting in and wiring up a tag light. Should look cool at night and give one less excuse to get pulled over. 

 

I also finally painted my transmission crossmember late last night. Once that’s dry I can mate the trans back to the engine block. All my exhaust gaskets are here so that can all get put back together soon too. 

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More preparation for the efi today, and hopefully the exhaust and trans will get buttoned back up. The holley 950 throttle bracket looks like the throttle, return spring, and kickdown parts will swap right over. 

 

The 1977ish iron water pump has two sensor bungs for some reason. The factory plug in the inboard one needed a little persuasion from the ox/a torch to start unscrewing. It had only been plugging that hole for 42 years haha! The holley sniper sensor screwed right in by hand but at a slight angle which is disconcerting. It’s definitely not crossthreaded though- I took it out and back in and checked. I put some teflon paste on it for sealing insurance. I thought for sure I’d need to get creative or buy brass adapters so checking that item off is nice. 

 

I love having my burning rig on wheels now I use it all the time! I modified a $20 craigslist hand truck with brackets and straps so my sparker has a hanger and my hose coils and hangs neatly. I am lazy though and use the cutting tip for everything. Some day I’m going to hit the cut handle and vaporize something important. 

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Welp 15% chance of rain turned out to be 100% here today but not before I got the transmission bolted back up to the motor. 

 

Thank goodness I remembered to hit the flexplate and converter with a shot of pink spraypaint- one out of the four bolts is offset and guessing involves spinning the motor over and over with a breaker bar. I have the pink corner of the flexplate down and the torque converter fully seated and held in with a box wrench bolted to the inspection cover hole on the bottom. All the ports are capped so rain isn’t a problem. I just have to take that wrench off and spin the pink side down and I can bolt it up. I’m waiting to do the starter till after the exhaust so I have more room to maneuver. The 727 isn’t particularly heavy but it’s heavy enough to make it a little struggle.

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