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Exhaust question 66 Cotonet 361

mtbase

mtbase

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I have a 66 Coronet with a 361, it's the original engine. The engine was totally rebuilt and remains a true 361, as far as displacement goes.

Changes that I made along the way:
I put in a more aggressive cam
Installed a 4bbl Edelbrock 1406 on a original Mopar, year correct manifold
Dual exhaust ( 361" came with a 2bbl and single exhaust)
I had to insulate the carb from the manifold, as the carb was getting too hot sitting on the cast iron manifold, with the "crossover channel"

The car runs well, that is to say that it starts, accelerates and can get out of it's own way. I had expected more out of it, however. Some one else looked at it and said that the exhaust dia. was restricting it. I guess it does look kind of small...1-3/4" dia I believe, but that was the stock size ...and now it's "dual".

Does anyone have an opinion on the exhaust...I'm actually considering replacing ...an exhaust system with not even 2,000mi on it.
 
I think the pipes would be 2", but the tailpipes may be smaller I think they would be 1-7/8"
The mufflers would likely be the biggest restriction.
Is it tuned properly? Timing and carb fuel/air mixture will make a difference in power.
The Edelbrocks tend to be kind of lean out of the box.
Some options without changing all your exhaust pipe, a few ideas:
1. Tune it
2. Maybe mufflers - you could even go to 2-1/4 or 2-1/2" mufflers with reducers and leave the pipes.
- If you put the mufflers on with band clamps you can remove them later and upsize the pipes.
3. An H-pipe with your existing mufflers, essentially doubles your exhaust size with an equilization pipe.
A 361 can run well like any Mopar but they were made for longevity and low maintenance not really high performance.
 
Reading you description again.
Maybe consider an aluminum dual plane intake like a Weiand or Edelbrock performer instead of the original cast iron manifold.
When you install it order a valley pan that blocks the heat crossover passage.
This will make a difference.
 
On a stock 361 you dont need large pipes, especially with duals.
Too large and you lose low end torque.
I like the x-over.
 
Did this to a stock 360 CI 4 bbl Chrysler. Cast manifolds, TTI 2 1/2'' to the back bumper.
Used their DynoMax mufflers. Not saying to buy it from them(but I would) just for reference.
I would say the draw back may be the 361 2 bbl cam. Though what you have done has to be a improvement.
IMG_2116.jpg
 
OOPs ! How did I miss that..:(
 
I had a 65 383 2 bbl SF and installed OEM duals with OEM 4 bbl intake and 585cfm Holey. It was a totally different car.
With the OPs ar, the cam may not be installed correctly or the gearing may be too high for the combination to work at low rpm.
 
Is it getting wide open throttle?
How many miles on it?
Are the rings seated?
Is the timing advanced enough?
What compression ratio?
were the pistons replaced?
Does it still have closed chamber heads?
What rear end gears and tire diameter?

You throw on some 28” tall tires with 2.9 gears and it’s a dog. 361 is a small engine.

Also if you put on open chamber heads with the stock or rebuilder cast pistons now you have low compression ratio.
 
I think the 361 exhaust manifolds are very restrictive, since they were designed for single exhaust with cross over pipe. You could upgrade to 383 4-barrel dual exhaust manifolds or Magnum manifolds. Of course either of these options would entail new pipes. I think 361's had 9.0 compression, which is good for today's premium fuel. I run 2 1/4" head pipes and 2" tail pipes, but I have a 440 in my '64. Factory rated 361 4 barrel at 305 hp. In '62 Dodges. Now, the V-6 in my Durango has about the same.
 
The log manifolds should the the same as my originals on my 66 383 charger.
It sure didn't seem exhaust restricted to me I think your gains there would be slight.
 
Wow, there are suggestions all over the place, so I will pile on
1. I think tuning the engine for timing & fuel mixture is what I would do first.
2. I think your exhaust is just fine like it is.
3. An aluminum intake would be my 2nd change
4. GEARS, GEARS, GEARS if you want to be quick off the line....but no higher than 3.55's if you want to drive it on the highway.
 
my question would be what type cam?
that engine has closed chambered heads. Too much fuel is as bad as not enough. The 361 manifolds are the same as the 383 in 66, which are the same as the four barrel engine that year.
a dual plane with the factory four barrel cam would normally make the 361 run really well. Then 3:23 gears, not 2:76 or 2:94. I have three 66 Dodge coronets, one 361,one 383, one with a 68 340 engine as well.
 
I would not expect much from a stock '66 383 4 barrel...much less from a 361. If it doesn't have 9:1 or better CR a bigger cam might have been a step backward. Knowing the tune up, cam and converter specs would help.
 
The 383 in 66 was good with torque, not hi RPM horsepower. 325HP. I believe at 4800. the 63 66 383 state police engines with two barrel carbs were 10:0 compression and tall gears. they actually did very well, and could cruise at a high speedfor extended periods, and were very reliable.
in fact that was the only time I ever saw an HP stamp on a two barrel 383 engine.(1963)
 
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if I were running a 361, I would get a cam that specs the same as the police 383 from 63-66, and add an actual mopar four barrel, not an edelbrock. they are jetted too lean. run the same exhaust as the cop cars, and choose a rearend that fits your needs.in 1966 the 361 was rated at 265 HP, the Polara 383 was rated at only 270. then rated 325 with the stepped up cam and four barrel, they used the same exhaust manifolds for both engines those years.
 
I went down a similar path with the 361 in my ‘64 Sport Fury. Duals, 4 bbl, factory intake, slightly larger cam, had factory 3.23 axle. Was always underwhelming. It had appropriate acceleration for what it was, 8 sec from 0-60 but never too exciting. In the end the cam was slightly retarded but fixing it didn’t help a boatload.

Ultimately I wanted more but still stockish so I bored a 413 to 419, call it a 426. Much more to my taste. Gets to 60 in 6, does about what a good stock 440 magnum car did when new.

In hindsight the 361 was a decent enough engine but kinda small. Advantages are all the head, flow, valves of a larger engine servicing a 361. Spins ok. Can yield a decent driver that doesn’t suck.
 
Thank you all.
I'm hardly a Pro at this, so I had a local "auto machine shop" handle the details...they have built drag cars for years. They did all the machine work and the owner actually allowed me to assemble the short block, staying late at his shop making sure that it was assembled it correctly, as I wanted to say that "I" built the engine. This is the factory engine , but it came through with 383 heads...someone told me that the 4 speed versions came through that way. The machine shop owner did try to get me to bore it to a 383 spec, but there were thousands of them made....only 373 were Coronet 500 with a 361 and factory 4 speed. I was trying hard to keep it really close to original.
Perhaps I got what I wished for.
With the original 2bbl, I needed to go to 2nd gear to get up a hill on my street...With the Edelbrock, I don't need to down-shift. In my efforts to stay "factory-ish", I hunted down a "66" 383 intake, perhaps that was a mistake...I watched the paint cook off above the crossover.

I'm not disappointed, but I'm not going to impress anyone with performance....It looks good though.

Intake and mufflers, would seem to be the next step.... to fixing something that's not really broke.

Thank you all again
 
IF IT AIN'T BROKE,DON'T FIX IT !!! Sorry I had to say it .. :lol:
 
If you are changing exhaust, I recommend buying some 68-69 383 HP manifolds, and then new exhaust. Accurate exhaust produces high quality factory systems, I have bought three sets from them myself.
this is a c body version, but it gives you a good Idea what to look for.

1967 440HP manifolds 1 July 2016 013.JPG
 
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