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66 Coronet 361 Exhaust opinion


FBBO Gold Member
FBBO Gold Member
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9:29 PM
Mar 27, 2015
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Huntington, Ma
My 66 Coronet 500 has been completed for 4 years now.
Originally born with a 2bbl and single exhaust, I changed out the cam with something for a 4bbl and added dual exhaust.

The car runs well...that is to say that it starts up nice and has enough power to get up my hill...with the Edelbrock 1406 on it, not soo much with 2bbl Carter.
I'm certain that I f'd-up a bit with the manifold....choosing a period correct '66' 383 cast iron. Not the best choice, but could have been worse...maybe.

My focus is on the exhaust. I bought an original replacement setup, with my restoration, and now I'm thinking that 1-3/4" dia is just too restrictive.

Not trying to build a "race car", just want a little more "pedal".

Advise appreciated
Your exhaust is fine for that motor. I’d add headers before larger pipes if that’s what you’re thinking. An aftermarket aluminum dual plane intake would make sense.
That intake can support at least 375 HP. I think you need 2.25-2.50 exhaust with an h or x pipe in between and some high flowing mufflers. Some HP[Road Runner] exhaust manifolds would also be great without the hassles that headers always bring. 3.55 gears and a mild stall converter in combination with the better exhaust would be perfect.Finally,a good electronic ignition with a quick advance curve and total advance set at 36 degrees will make the most of it. Good luck.
Correction: I see now you are running the more restrictive 66 intake. I was talking about the 68-71 intakes which are pretty good.
2.25-2.50 exhaust
Always a good idea. You cured the stuffy nose with the change to a 4bbl. Now you need to get the expelled gasses out. It's nice to know what you plan to do with the car. Driver ? racer ? stop light bandit ? Glad to see you included not trying to build a race car just a fun driver.The more we know the better we can advise. Thank you for that !
That helps all of us when this type of question arises. 66 Coronet 500 is a fine looking ride .
I don't think the exhaust is your hold up.
The stock 66 cast iron 4-barrell intake will make good power up to 5,000 RPM.
I agree with a quicker advance curve and get a strip kit for the Edelbrock. They can be pretty lean out of the box.
What else was done to the engine?
It was a complete rebuild?
How was the cam degreed in?
What cam was it? If it's not too large then the stock converter is probably fine. But remember your transmission likely has a 19 spline input shaft if it's a 66.

Yes performance mufflers and an aluminum intake would likely add a little more performance.
The original log type manifolds aren't great at high rpm but in mid-range there's likely little difference.
2 inch would be nice, so would 68-70 383 magnum manifolds (exhaust and intake). If you have the 1 3/4 with mufflers you probably can't sell them so I guess there would be no harm in mounting them, they'll still be an improvement over single exhaust. We have to think like it's a very mild 360 not a 383.
I just reread and yes everything is mounted. As above a quicker advance curve in the distributor is worth a try and maybe add an 02 sensor as there is likely something to be gained in the carb tuneup.
A big block struggling for power doesn't sound like a magic bullet intake or exhaust tweak is gonna fix it.

That relatively light car should have plenty of power to spare with any big block.
66/67 does just fine with a 318.
Even the 2.94 gear that's most common in a 66 8 3/4 is just fine.

Is the motor just tired in general or not dialed in?
Compression test?
Cam degreed?
Do you still have:
stock 361-2bbl pistons?
closed chamber heads?
steel shim head gaskets?

A 361 is a bottleneck in itself. It's only going to do so much. Be glad with the improvements you have.

What is you intake part number. 2205968? Or 2806301?
Hi all;

And thanks for the input.
I can see that I didn't provide enough info.
I bought this car in pieces, as the previous owner was ready to put a 440 in it, and suddenly passed away. I never heard the engine run before the tear down.

It's a factory 4 speed car. The engine is completely rebuilt...can't be more than 1,000-1,200 miles on it.
I tried to make it like how it came off the assy line: It is still a 361ci, although the rebuilder ( an old-timer with serious racing roots) tried to get me to bore it out to 383.
My goal was to make it run with the factory 2bbl (just try to find one of these), but the cam was ordered with the 4bbl evolution in mind.

I know that I was the first to break the bolts loose, as the paint was still on the bolts. There were couple odd things with this engine:
Forged crank (typically casted with a 361, so I'm told) and 383 heads. I'm told that the oil pan was for a 383 as well (402, I think).
Running with a stock distributer and points.

I'm mechanical, but not a mechanic...when I put the engine in, I should have had the exhaust manifolds on it. It was a bugger getting those on afterward, so I'd like to avoid changing to headers.
The manifold is 2205968
I believe them to be stock 361 pistons

The car runs good. I seem to remember a 66 Charger, that I had, that was a bad-***
But everything seemed better then
Forged crank is correct. Early lopo intake manifold (still way better than a 2 bbl). Compression ratio probably about 8.5-1 actual depending on which 383 heads you have. Anyway I think it could be relatively "peppy" with what you have if the timing and carb tuning are optimized.
At what rpm are you looking for more pep? Off idle, mid range, or higher rpm wide open throttle?

They all had a forged steel crank.
The 402 pan is for a big block b-body,

Do you know the head casting number?
Do you know what head gasket he used?
Do you have a part number and brand of the pistons?
These thinke make a huge difference. You could have 8:1 compression ratio, that could foil any attempts here.

That intake is terrible, it is flat with no rise. How did you bolt an edelbrock carb to it, does it have the narrow pattern or do you have a spacer?

Get a helper and make sure the 4bbls are opening all the way. One pressing the pedal and the other looking at the carb. Don't open it by hand, that's not what you do when driving.
I have a stack of receipts on the engine rebuild here somewhere...certainly the pistons are in there
I didn't write down the casting numbers, I spent time on the body, getting the correct color, the correct upholstery.

The Edelbrock has a dual bolting pattern and bolts right on. What's your manifold recommendation?
I'm ready to do this year's mod ( I won't a major one)
I'd use an edelbrock performer, or a 2806301 68/69 intake.

But the other questions unanswered leave holes in the story, remember an engine is all about the combination working together.
I agree, check to see if the carb is going wide open. I have an edelbrock on my 66 383 with that same intake. They came with a small bore carter afb and if you just bolt a newer carb on there, the butterflies will hit and stop it from going wide open. I have a small spacer on mine, like 3/8” thick. It doesn’t take much to make it work. I think if you get your timing and carb dialed in it should be pretty good unless you have 7:1 comp ratio.
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