Exhaust choices...

[mungus]

Planning my 390's exhaust. The cars not ready but I need mufflers for my engine test stand so I'll buy those now. So my questions are about peoples experiences with tube size, cross pipes and brands.

No surprise 3" = more power, (Nice "Engine Masters" YouTube dyno runs below, compares Magnaflow 2.5 and 3" mufflers). However I'm not building a strip car, so 3" is probably too loud. For a cruiser I'm thinking 2.5" is better suited. Bigger than stock and a size offered in kits by performance brands like Magnaflow and Flowmaster, so I assume its big enough to work well. Any opinions on 2.5"?

https://www.youtube.com/watch?v=_PVXvHkr-Vs&t=1s

Next is pipe design. X pipes and H pipes both help power over separate pipes, but this dyno comparison shows they are almost identical in terms of numbers. The H tends to favour low end TQ at the expense of peak HP, the X seems to be the opposite. But practically unnoticeable differences really. The tone seems to change though. X pipe higher & smoother, H pipe deeper.

https://www.dailymotion.com/video/x5s8nr8 Anyone have either type and care to comment?

Lastly are there decent OZ market mufflers that compare to the likes of Magnaflows? I like their 2.5" X pipe system (PN - 15816), but thats about $1,400 AUD landed. By comparison a reputable exhaust shop in VIC (Sharp exhausts), who've done quite a few classic Mustangs & Falcons, estimated $800 for a Mandrel bent system along the same specs as the Magnaflow system. Thats a big difference, for a logo few will see. Searching the web I've found a few Magnaflow look-a-like mufflers for reasonable $. (The MF spec is - 4 x 9 x 14" & 2.5" curved straight through core, offset IN to centre OUT). Magnaflow seems good but very pricey... I'm not wanting cheap junk mufflers but some of these offerings on eBay look OK, and appear to be the same design as the Magnaflows, but less than 1/2 the price. Anyone tried them?

https://www.ebay.com.au/itm/2-1-2-SPORT ... 2947515952
https://www.ebay.com.au/itm/2-5-Megapow ... 1380760816

Anyway looking forward to comments... Thanks.

[hybrid]

I'm running twin 2.5" (mandrel) on my supercharged 347. It did 310kw/540tq at the wheels turning off at around 5500. We're expecting 340kw or so next time we can rev it out.
I personally don't think the small gain for 3" is worth it due to the extra noise, but the late great boofhead used to disagree often with me on that
He did love extracting every horsepower though.

IMO twin 3" is overkill for a mild engine.
Mine is an x-pipe system.

Here is mine on the dyno for comparison (you can hear the gearbox slip at the end which is why we couldn't keep going):


This is it idling while still in the build process:

[mungus]

Thanks. Its what I'm thinking too. I've had street "legal" race cars on the road before, and the noise gets old very quickly.

A couple of HP at higher RPM won't be noticed much by me, so I'll go for the 2.5" system.

I like the sound of the X pipe classic Mustangs I've heard on YouTube and the X sections are cheap ($65 inc post on eBay). However I have seen a few reviews saying / showing that H pipes give better low end TQ and provide that nice throaty muscle car sound, vs. X pipes being higher pitched and improving top end. So I guess I'll have to think on that a bit more. I did notice that Sharp Exhausts seem to fit X pipes on most of the Mustang / Falcon systems in their Facebook gallery.

Can I ask did you go Magnaflow or local?

[hybrid]

Mine is local custom made, but I can't remember the brand of the mufflers sorry.
I do know they are center/offset packed mufflers - not the chamber type.

I'm not sure I would call my exhaust note high pitched, but I never had a H pipe to compare sound wise.

[hybrid]

Mine is local custom made, but I can't remember the brand of the mufflers sorry.
I do know they are center/offset packed mufflers - not the chamber type.

I'm not sure I would call my exhaust note high pitched, but I never had a H pipe to compare sound wise.
I will say that performance wise what you're reading/hearing about the H pipe is not what was reflected by engine masters. The X was a bit better, but it was no more than a couple of horsepower so it really comes down to sound since you'd never notice that difference. Having said that, their pulls don't really start until 3000 rpm generally.
They did say that the X seemed considerably quieter, but that may have been because of the smoother note.

[mungus]

Your mufflers are probably the same spec as a few classic Mustang performance dual systems I've seen in my web searches recently. Typically 4 x 9 x 14", 2.5" pipes, and offset IN and centre OUT. Curved straight through types, (not chambered) with stainless & fibre packing. its is the same muffler spec that MagnaFlow supply with their kit.

There are some OK looking stainless ones like that, (below) for less than $100 each inc postage, on eBay OZ, and they look basically the same as the Magnaflow ones, whose lowest retail I could find in OZ was $230 each... I'll probably check with Sharp's before I buy anything, just in case they have something to add, but I'm thinking that's probably what I'll buy.

Thanks for the info. Your motor sounds good.

[cage]

Didn’t Boof do a write up on this? He had some very strong opinions on this subject the legend.

Mungus, I have a 347 NA making 480hp, full of parts all worked out with Boofhead. I ended up going with modified pacemaker headers, 2 1/2” stainless with Flowmaster Super 44 mufflers in centre section. I did not put a cross pipe in but I wish I did. The Super 44 aren’t the loudest that Flowmaster do but it is pretty loud. Definitely don’t need 3” in my opinion.

[mungus]

Looks nice. Seems black is a common choice these days. Not long ago everyone wanted the shiny stainless or aluminum look.

I've got Boof's (RIP) article on exhaust drone, but it doesn't really relate much to pipe sizes and muffler choices for a 390/428.

Being a 390 I went with FPA headers, as they seem to fit in engine bay reliably and have a good reputation. I opted for the charcoal ceramic coating, to knock the heat back a bit and avoid repainting. I reckon they look OK, but I did have to fettle the lower corner of the block to get some clearance.



After having a chat to my muffler shop (Sharps in Sunbury - pretty reputable outfit), I've ordered a pair of 2.5" stainless Magnaflow clone oval mufflers from ECS exhausts in NSW. Sharps said the same as I felt all along. That 3" straight through systems are too loud for anything more than short drives. Sharps do their own X pipe (looks like a Magnaflow), so I may go with one of those too. All the info I've found is that X and H pipes do add a little power, but there's not much between them. It seems the main difference is mostly sound tone.

Anyway the choice is made, the mufflers are on their way...

[Pinto-Pete]

The last time l had my 429 running in anything it ran twin 2.5 inch centre offset lukey mufflers and a H pipe nice deep sound and not intrusive..

[Ausjacko]

We used the hooker Super Comp headers on the 390 AND installed them attached to the motor and trans. Admittedly Justang (now there is a blast from the past) had double jointed wrists to aid installation.

We used a 3" pipe to join to the muffler at which point it drops smaller. We might have a sneaky cut-out system to take advantage of the 3" but that is only pose value really.

As can be seen below, we use a H pipe for the tone as you 'noted' -get it. The co-fabricator could only use sign language- he has increased his vocab now thankfully to include a thumbs up.

[mungus]

Thanks Jacko. Yes I've seen a couple of guys in the states used Hooker headers and they managed to get them in, albeit only just and with a couple of paint rubs. I chose the FPA headers as they were recommended as being the best fitting by a few big block Mustang guys in the states. I'm planning on doing a dry fit of all my basic running gear and driveline before painting, so I guess I'll see then!

I'm still wondering about the X pipe vs. H pipe. I must admit the H pipe looks better to me, as the pipes run nicely parallel all the way down and don’t obscure the prop shaft. Maybe X pipes are trendier now? As it seems the dyno shows nothing significant between them. X pipes are no longer expensive here with eBay Magnaflow clones being $65 inc post on eBay. But then I'd make an H pipe on my own for $5...

Step down wise I've ordered a couple of 3-2.5" adapters from the same place I got my mufflers. So I'll just MIG those to the collector ball joint pipes and voila. More than 1 way to skin a cat I guess.

[hybrid]

Something to keep in mind as well mungus, which was also mentioned in the engine masters video. You need a lot more space for the x-pipe because the pipes change angles twice. This also affects the cost of the exhaust because you need to buy more bends to get the pipe into and out of the X, not just the X itself.
One of the benefits of the H pipe is super simple install. It should be easy to find a spot to put in the crossover pipe. I prefer the X personally because of the sound, but there is no denying the easier installation of the H.

[Ausjacko]

Sorry, I have heard from the Co-fabricator. He tells me it was a spelling mistake on his part and it should have been a thumbs up not the naughty finger...

[ozbilt]

X pipes have been around in racing forever. Especially NASCAR.

The trick is to get it where you need it. You want it to help the sweet spot in the torque range.

We ran differing spots for the X depending on the track we were running. Easy for us as it was a space frame car and the exhaust was assembled with ring clamps (aircraft stuff).

If the exhaust is done correctly (see gbx78 Scarlet thread) you can pull the box with out touching the exhaust system.

I would run an X pipes in a heartbeat.

[mungus]

Thanks Kerry, food for thought.

I do like ring / V clamps, just adds a few $ and takes some more work having to TIG them on, and "proper" precision fitting compared to standard exhaust clamps over swaged joints. But we'll see how I feel when the time comes.