Super Six install on 1974 Dart

MOPAR4Me said:

Great thread, really glad to hear you got the carb issu solved. Did all the pinging also go away?

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Yes, I should have mentioned that. The ping is gone even with timing more advanced. Side note: along the way I recurved my distributor: I replaced the springs with the springs from the Super Six donor car's distributor. There's much less mechanical advance now, so I can run plenty of initial timing without ping.

Great thread, first time Im seeing it. Rich, what product did you use to coat your exhaust manifold? It looks great, does it hold up to the heat? Do you notice a huge difference between the Super Six setup vs the original 1bbl? just curious. Love the super-clean engine bay =)

I used Slip Plate spray on the exhaust manifold, something like $13 online. I also used it on a lot of the brackets, bolts, and things that the factory painted black: steering pump, fan pulley, kickdown linkage, etc. It contains graphite but it's different from the graphite lube spray sold by WD or PB. It's more like a paint. After you spray it on, you can wipe off the excess and it leaves a pretty clean surface. I would definitely use it again. [EDIT: I forgot to say that it's been over a year and a few thousand miles, and the Slip Plate still looks brand new.]

The 2bbl definitely gives the car more pep. That said, I'm not convinced my 1bbl Holley 1945 was working as well as it should have; for all I know a good 1bbl would have been about the same as the 2bbl. Also, I think I need to open up my exhaust a bit if I really want to get the max benefit from the 2bbl. Super Six cars came with 2 1/4" exhaust and I still have my stock 2" pipe.

opening the exhaust pipe wont help a bit, UNLESS you also open the outlet of the manifold/ to at least match your pipe size....
I ground out 2, /6 exhaust manifolds that came to me, (both with Super 6 intakes bolted to them) with a die grinder and various burrs.... both exhaust manifold outlets were well under 2-1/4", when I started.... the 2nd one I did, though the whole outlet hole in the manifold was within the confines of the ID hole of the flange gasket, I didn't have to grind the whole circle, probably ~3/4 of it, to get the entire outlet, out to 2-1/4 Diameter///
but the original 1-7/8" outlet hole "touched the side" of the 2-1/4" hole, in the flange gasket... 180* from where the outlet hole "touched" the flange gasket hole's edge, I had to grind ~5/16" of casting away to get that portion to also match up with the edge of the flange gasket hole, and tapered down each direction to where the manifold hole "touched" the gasket hole.... I bolted a flange gasket to the flange, and painted the ID to know where, and how much, to grind. That is the manifold that is going onto my /6. The 1st one I did// which is on my son's truck// wasn't entirely concentric with the flange gasket position to start with either, but it was much closer to being so, than mine. On my son's, to get to the 2-1/4 we wanted, I did have to make filings "all the way around" the manifold outlet flange hole.
hope this post makes sense, as I was pecking it out I had to stop a time or 2 and think... "wait a minute".....

The SuperSix engines didn't use a 2 1/4" exhaust system. The exhaust manifold outlets were roughly 1 7/8" in size, the same as all the others. The outlets also have a roughly 5* tilt to the rear. This may have more to do with exhaust routing to catalytic converters then any performance benefits.

The best bang for the buck, is installing a 2 1/2" exhaust system. This will wake the engine up, as it allows it to breath.

kesteb said:

The best bang for the buck, is installing a 2 1/2" exhaust system. This will wake the engine up, as it allows it to breath.

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But again as I said above
Exhaust bigger than the manifold outlet is pretty much a waste. Whether 2-1/4, 2-1/2, or even a measly 2 inch..... If your manifold is a 1-7/8"bottle neck, pipe larger than that bottleneck, offers very little benefit.
In order for 2-1/4, 2-1/2" exhaust after the manifold outlet to be of any kind of help the manifold outlet MUST be opened up as well!

When we were racing my wife's '73 Duster. The 2 biggest performance improvements were.

1) A TransGo shift kit.
2) installing a 2 1/2" exhaust pipe.

Those 2 modifications alone, lead to dropping almost a second off her track time. I know, because I kept detailed records of our runs. The shift kit allowed us to keep the transmission in gear longer, thus allowing the engine to rev up. The exhaust let the engine breath.

kesteb said:

The SuperSix engines didn't use a 2 1/4" exhaust system. The exhaust manifold outlets were roughly 1 7/8" in size, the same as all the others.

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I was going by this article: Super Six
And also this post: exhaust size - Slant Six Forum

I agree that the manifold outlet is the same size as the outlet on my 1974 manifold. I assume the designers thought it was worth using a larger pipe even though they didn't enlarge the manifold outlet.

kesteb said:

The SuperSix engines didn't use a 2 1/4" exhaust system. The exhaust manifold outlets were roughly 1 7/8" in size, the same as all the others. The outlets also have a roughly 5* tilt to the rear. This may have more to do with exhaust routing to catalytic converters then any performance benefits.

The best bang for the buck, is installing a 2 1/2" exhaust system. This will wake the engine up, as it allows it to breath.

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That's not entirely true. The big exhaust did come on "some" but not all. I don't know what rhyme or reason was used to determine it, OR if it was even on purpose, but I have seen at least two stock, unmodified slant 6 exhaust manifolds with large outlets in the 2.25" range. I know there were more, because I've seen others post about it here.

Engines that had catalytic converters may have a 2 1/4" head pipe to the converter. The rest of the exhaust system is the standard 1 7/8". The exhaust manifolds are all the same with the 1 7/8" outlet.

Here is a comparison of manifolds: Welcome to kesteb.us