How to make my '79 Commander sound like a '73??

I have spent several hours searching around here and PN and can't get to the bottom of my dilemna.

I just purchase a '79 SN with the 351 Commander. At least that is what the Manifolds say. The boat runs strong - same top speed as my '99 Response LX with the Monsoon!

My first question is - Why doesn't my '79 sound anywhere near as cool as my friends '73 SN with the 351 Windsor? I believe his has had some motor work done before he purchased it, but neither of us have good info on what was done. I can't remember what manifolds are on it, so I'm still waiting for a picture from him. But it looks and sounds almost exactly like the youtube link below.

Without exact motor info, can anyone tell me what I would need to do to my '79 to make it sound like this -

https://www.youtube.com/watch?v=yqprxbDz_FM

Right now mine has the round black manifolds that say Commander on them.

On a separate note, I am looking at doing GT40p heads, maybe hitek manifolds to get a little more hp since we are running at high elevation... Haven't determined if it has electronic ignition on it yet. Seems to be plenty of info on these mods, just need to continue my research.

I have owned and worked on a '98 SNOB and a '99 Malibu Response LX, but this is my first carb motor. We run at 8,200 ft of elevation, and I have a lot to learn about carb tuning, but the boat is running really strong right now so I'm a little hesitant to mess with it. A better exhaust note and a few more mph would be nice for barefooting though.

Any info would be appreciated! I'm posting on PN as well.

1) Mufflers
2)Exhaust Manifolds play 20% factor

Most if not all 73’s came without mufflers.
Most if not all 79’s came with mufflers.

Commanders have a log style manifold. They do lose some tone. Your friends 73 May have a riser style manifold which is deeper sounding. My dad and I have nearly identical 75’s, his has an original and starting to get tired 351 with risers. Mine has a potent 351 with very similar manifolds as your Commander. My dads sounds definitely meaner and deeper despite stock and high hours.

Also, anyone run the Hitek's without mufflers? Any idea how those sound?

(Lack of) mufflers, larger exhaust outlets, more metal in the exhaust path (as opposed to hose), compression ratio, cam, exhaust manifold material are all contributors to volume and tone. Aluminum and SS manifolds are louder than cast iron, in my experience. I have not noticed the same difference between logs and center riser... some of the loudest boats I’ve heard have logs.

73’s did not have mufflers (stringers/exh pockets are too narrow), but they were standard by around ‘75 or ‘76 in the SN- check the brochures. Yes, below the floor. HiTek’s + no mufflers are very loud for the aforementioned reasons.

TRBenj wrote: Mufflers. Don’t bother with PN.

Aaron,
I agree!!

Orlando76 wrote: 1) Mufflers 2)Exhaust Manifolds play 20% factor Most if not all 73’s came without mufflers. Most if not all 79’s came with mufflers. Commanders have a log style manifold. They do lose some tone. Your friends 73 May have a riser style manifold which is deeper sounding. My dad and I have nearly identical 75’s, his has an original and starting to get tired 351 with risers. Mine has a potent 351 with very similar manifolds as your Commander. My dads sounds definitely meaner and deeper despite stock and high hours.

I don't think so ... tone is certainly subjective so maybe deeper but certainly IMHO not meaner - I have found the aluminum logs to be some of the snappiest sounding manifolds and the pyramids to generally mute the tone - that's my experience on the same engine and just swapping manifolds...

The old mustang video in my signature was a set of commander style logs ... that boat had some fresh gt40ps so a little bit higher than stock compression and good sealing valves which makes for a bit more clean bark but in my experience no cast iron pyramids sound like that.

This video Chrysler Idle is a High compression Chrysler at idle with cast iron log manifolds and copper pipes (no mufflers) and it subjectively sounds just about right

Mufflers got to go either way for a boat to sound mean... after that that less corrugated hose and tight bends in the hose the better- replacing straight runs with copper or stainless pipe has been considered by some to be sonically enhancing.   Engines with more aggressive cam profiles and higher compression effect sound, but so does the amount of water running through the exhaust system

If you take off your mufflers, insert stainless pipes in their place, add gt40p heads, a performer or performer rpm intake (wont change the exhaust note but still do it), maybe some 1:7 to 1 rockers it will pick up significant amounts of power and sound pretty good with those commanders. Don't sell or scrap the mufflers until you live with it a while though ...

Personally I have found that opening up the exhaust ports on the log manifolds with a die grinder makes the boat a bit louder as well... I doubt it does anything positive to the performance that justifies the effort but it'll sound faster.

I have seen no evidence that hi-tek manifolds contribute significantly to the performance of one of these boats in a significant way at hp levels under 350 or so - a little weight removal sure and maybe 50 to 100 rpm - but the intake and gt40p conversion is way better bang for the buck.

Found the 20% in the funk that builds up underneath the couch.

Thanks TRBenj and JoeinNY. Based on your info I'm sold on doing the following this winter:

1) Replace muffler with 3" copper or stainless. Are either readily available used/cheap, or am I likely buying new tube cut to length?
2) GT40p heads. Can I buy these from any of the aftermarket retailers for Mustangs, or do I need to find something marinized?
3) Performer Intake
4) Cam - I've never had a head off before, so certainly haven't messed with a Cam, rockers etc. Can someone give me a specific list of things I need if I take this on?
5) No EI. Distributor with advanced timing. Is this something I can order off the shelf with the timing I want, or do I have to tune it?

Right now, at 8,200 feet the boat runs solid 40.0mph at 4,500 RPM, so I think it is propped pretty well at the moment.   When I finally got my Response LX with a 325hp Monsoon dialed in for 8,200 ft it could barely break 40mph at peak RPM (about 5,000). So, either this Commander has already been built up a bit, or I am very excited about the potential.

Thanks all, any more insight is appreciated.

Off Trail wrote:    Replace muffler with 3" copper or stainless. Are either readily available used/cheap, or am I likely buying new tube cut to length? .

Aaron,
There are plenty of on line stores to shop for metals but one thing to consider is stainless VS: copper. The typical copper (plumbing) you find may be sized by the I.D. so 3" will have an O.D. of 3.125" and that makes it harder to get the exhaust hose on. Stainless tube will be sized by the O.D. and then the wall thickness.. So, a 3" tube (.065" wall is plenty) will fit nicely on the exhaust hose. Some will say 400 series (muffler grade) is adequate for corrosion protection but I recommend using 304.

Check Craigslist for heads, AFR heads were on many Mustang Engines and are out there on Craigslist at reasonable cost. New I think they are $1,500-$2,000.
There are some other reputable companies making these aftermarket Aluminum heads, I only mention AFR because they have a great reputation.
If you find a set of the P heads they do run really well and are usually much cheaper.

*542

I am not worried about the hours, it looks like a nice clean package that would be a shame to tear into. If it's an OJ prop that's not a cnc prop then there is likely a mile an hour or 2 to be had with an acme. With the increased elevation that acme is likely A542 You might pick up a couple of rpm but I'm thinking you could get to 42 miles per hour. Either way the first biggest bang per buck is usually a modern prop the second is the gt40p heads.   If you did the heads you still would want the prop imho, so with an engine that clean i would make sure the prop alone wasnt enough before I took it out.... but its your boat and your money. I would suspect a gt40p swap well done and propped might get you to 46 at 5000 rpm at your elevation.    Have you considered moving downhill?

I figure you already know that you're at about 75% of what the engine has for power at sea level.

If you want some good noticeable extra speed, jack up the power like Joe mentioned with GT40P heads, and add to that a better intake along with a new cam and/or 1.7 rockers

I think I have 2 paths to choose, and it is going to be tough to decide:

1) Get it in the garage before the snow flies, and spend my spare time this winter getting the GT40p's and performer intake installed. Put it all back together before the lake thaws out, and cross my fingers that I did it right and have a boat for the summer that will pull me at 42 mph footing.

2) Get the mufflers out and put it to bed for the winter.   Play with prop'ing in the spring but likely have to deal with 38mph barefoot speeds for the summer.   Decide if this is really my barefoot boat and if it is really worth tearing the motor apart next winter....

A smart man probably chooses #2. But...a '79 that can do a better job pulling me footing than my 'modern' Malibu did....sure is tempting.   Then again, I'm not throwing long-line toe-holds....or any toe-holds.   So maybe just suck it up and enjoy my 38mph boat that looks and sounds better than anything else on the lake.

Decisions.....decisions.....