512 cid C series on Dakota chassis- build thread

[Radarsonwheels]

Howdy flathead folks!

 

I’ve checked in here & there but haven’t posted in ages. My slapshifter swap is still going gangbusters but my exhaust has been an ever increasing source of headaches. Well not literally, but given a longer drive probably would be due to exhaust leaks.

 

Still haven’t installed my new heater core- honestly it was too hellish of a summer here in PA to drive the truck a lot or work on it in the heat.

 

I originally built my exhaust starting with 1 5/8” chinese stainless block huggers. They had decent welds, 3” collectors, and a really nice thick flat flange on the head side. And they were like $120 or some outrageous cheap price on amazon. My budget was on its last legs at that point, which is also why I used rediculously oversized and loud 3.5” in/out flowmaster 40 mufflers I scored off Craigslist.
 

The other side of the coin- the bad parts- were that the #7 tube needed a huge dent to clear my rear passenger side upper control arm pivot, the collector bolts were almost impossible to reach and kept self loosening, and after about a thousand miles both sides started to blow holes in the welds where the ‘star’ fills the interior of the 4 pipes as they collect. 
 

I installed ‘stage 8’ brand locking collector bolts which solved the self-loosening problem but then they were almost impossible to access for further tightening and the percy’s brand ‘dead soft aluminum’ collector gaskets began to slowly smoosh thin and leak from vibration. 
 

Also the pinhole leaks on the star welds got worse and worse leading to bad sounds, stinky exhaust in the engine bay and cabin, and false lean o2 readings messing with the EFI.

 

So I bought a set of hedman block huggers. They collect farther down and present a much thinner profile while increasing my tube size from 1 5/8” which is suitable for a warm street 318, to 1 3/4” which is more right for a hot smallblock or street 440. I’m hoping to feel a touch uncorked at WOT but I’m sure the 512” will like it better all over. 
 

Just removing the passenger side header was a huge chore- it’s trapped/stuck between the block & frame. Today I finished pulling it though, and the hedman just dropped in as easy as pie!!

 

Fingers crossed the driver’s side fits as easily. I still have to check plug access but it’d be hard for it to be worse. I needed special $$ plugs for the 4 corners and fiberglass boots on every plug to fit the last exhaust. 
 

I also ordered a set of 3” borla xs pro or whatever their $100 muffler is, along with a 3” mandril bend kit to make new downpipes and complete exhaust. I’m planning to cut off the 2.5” 3 bolt collector flanges from the hedmans and add 3” tube with a set of Vibrant brand V-band gasketless collector flanges. As long as I don’t warp them in welding they should offer one bolt collector tightening and no leaks!! 
 

So I still have to buy a couple new O2 sensor bungs, and fabricate everything all up, but I have high hopes that I’ll be cruising in style this fall with no stink, mellower but still rowdy sound, and maybe even enough more ponies upstairs to feel on the butt dyno. 
 

I hope everyone is doing well and looking forward to more smiles per gallon after this dumpster fire of a summer!

 

*here’s a pic- you can see where I beat the dog-poo out of the SS header to clear the UCA pivot and the mocked up hedman clears by a mile

[Radarsonwheels]

Today was a good day!

 

I finally got to drive the truck after a month or so down replacing the old leaky inaccessible 1 5/8” headers with larger 1 3/4” better fitting hedman shortys. 
 

The truck was noticably faster. I’m sure long tube 1 7/8” headers would be worth another decent bump in power but there’s just no room in there. 
 

I cut the headers triangle collector flanges into circles and welded in 3” extensions, ending in male/female V-band connectors down where they’re accessable under the car. From there the exhaust got tig welded up with 3” mandril bent stainless, into the borla pro xs mufflers. 
 

The mild steel headers with stainless extensions got sent out to Jet-Hot in NC for polished ceramic coating inside & out. 
 

I re-used the 4 old hanger locations with new rubber and steel hangers to keep the weight off the collectors. 

[Merle Coggins]

Sweet!

[RNR1957NYer]

Glad to see you and the truck are alive and kicking, Radar!

[Radarsonwheels]

Beautiful Morning! Maybe I should get around to installing a heater again ? 

[QEC]

Something tells that 512" in not compatible with snow covered streets...?

[RNR1957NYer]

Thanks for posting, Radar -  the other day I was wondering if you still had the truck!