Exhaust tone

[Scotty]

On a properly tuned, idling Alpine, should the exhaust note have a rhythm to it or should it just have a flat tone?

 

[sunalp]

Tone should be even. Not sure I'd call it flat.

 

[bernd_st]

Whether rythmic or flat it's music to my ears as long as it doesn't sound tappety ;-)

 

[ernestovumbles]

Here is mine.. just recorded on my phone.

Sunbeam Alpine exhaust by Ernesto Vumbles, on Flickr

 

[RootesRooter]

Idle rpm's might be a little high, but sounds smooth and sweet.

 

[Acollin]

i had the same question as rootsrooter— what is the idle rpm?

 

[ernestovumbles]

it's normally a bit high.. probably about 1100 rpm..

This also may have been shot with the choke still on while warming up.. dont remember.

 

[puff4]

At the risk of wandering off thread, I will note that the stock mild steel exhaust sounds considerably different from the newer stainless steel systems. The former are more mellow and “classic” sounding, whereas the latter are much more tinny and brassy. I have stainless, and although I like never having to think about it leaking or needing replacement, I miss the sound of the stock system.

 

[husky drvr]

This also may have been shot with the choke still on while warming up.. dont remember.

That was my first thought, still on fast idle with the choke on.

 

[husky drvr]

On a property tuned, idling Alpine, should the exhaust note have a rhythm to it or should it just have a flat tone?

Scotty,

XXXX>>>>strong firing pulses

OOOO>>> weak firing pulses

\\\\ >>> dead miss pulses


If you're asking if an idling Alpine should ideally sound like >> XXXXXXXXXXXXXXXXXXXXX...

Then yes, but the closer to OE stock induction, exhaust, ignition, and lower idle speed, then the "weaknesses" of the OE design will make it sound more like >>> XXXXXOXXOXXXXXXOXXX>>> sort of an occasional, random miss. This is called "hunting" (idle speed is NOT changing) and is not considered a problem.

On the other hand, if your exhaust sounds ... XXX\XXX\XXX\... or >>> XX\\XX\\XX\\ or similar... that's an issue needing investigation.

Hope this helps,

 

[Jay Laifman]

I have had both the later SV cast exhaust manifold on and the earlier style headers. Note that the earlier headers are tri-Y and equal lengths for the first segments. But the cast SV manifold had different lengths for the first segments. 1+4 longer with 2+3 shorter. Presumably they are tuned to match the pulses. But I have NO IDEA if Rootes actually would have spent the time and money on tuning them.

I will say that they do sound different to me. I think the earlier version does sound a little smoother and the cast one a little more burble. My seat dyno suggests the earlier version flows higher. However, I thought I was getting a slight exhaust leak on mine. And I drove the car for decades with the cast version, so its sound is more in line with my memories of my youth! Ha.

So I put the cast one back on. I think Dan was going to make a new trip-Y so I was thinking I might go back to that when he does it.

I should add that I have the Holbay head, which had exhaust ports that are larger than a stock head. My earlier tri-Y headers were larger than stock pipes, and matched the Holbay head. The cast SV manifold is smaller. So I got in there with a Dremel and opened it up through the bend to eliminate the lip that the exhaust out the head would hit.

 

[alpine_64]

. My seat dyno suggests the earlier version flows higher. However, I thought I was getting a slight exhaust leak on mine. And I drove the car for decades with the cast version, so its sound is more in line with my memories of my youth!

Jay.. I suspect butt dyno was influenced by sound... That said.. you implied the later cast manifold was louder?

The first version of the cast manifold was introduced in the S3GT .. it was to create a quieter engine lower exhaust sound. At this point the ST still had tri Y headers.

On SIV/V all cars used a cast manifold and I believe a slightly different design to the S3GT ...but a parts book check would be needed.

There has been test done that show the later cast manifold actually produced slightly better power across the broader rev range than the early headers.

Also of note... The stock Harrington LM and rootes comp accessories had different 4/2/1 headers than series I-3 Alpines

Iirc the headers sunbeam specialties used to sell were based on the HLM headers

 

[Alpine 1789]

I have a complete S3GT engine and the cast headers look just like the SIV/V ones, except there are only two manifold bolts.

 

[husky drvr]

except there are only two manifold bolts.

Jim,

... and ONE exhaust outlet for ONE down pipe.

The s3GT engine was de-tuned somewhat to make for a bit more pleasant "touring" car.

Your picture seems to show a possible carb "heat shield." Any possibility of a couple of better pics since the heat shield topic came up in a recent thread?

Thanks in advance,

 

[Jay Laifman]

Jay.. I suspect butt dyno was influenced by sound... That said.. you implied the later cast manifold was louder?

The first version of the cast manifold was introduced in the S3GT .. it was to create a quieter engine lower exhaust sound. At this point the ST still had tri Y headers.

On SIV/V all cars used a cast manifold and I believe a slightly different design to the S3GT ...but a parts book check would be needed.

There has been test done that show the later cast manifold actually produced slightly better power across the broader rev range than the early headers.

Also of note... The stock Harrington LM and rootes comp accessories had different 4/2/1 headers than series I-3 Alpines

Iirc the headers sunbeam specialties used to sell were based on the HLM headers

Actually, no I do not think the later cast manifold was louder. I think it has a bit of a burble that the pipes do not. The difference I'd say I note in power is at the higher rpms. I feel like over 4,500 and up, the headers just kept flying up rpm with no end in sight. The cast manifold seems a tad off that. But again, no real proof.

I have a set of the SS stainless headers. I never installed them. They didn't quite seem to be the quality that the headers I have are. I'm still not 100% sure what they are. I found them laying in a derelict Alpine I got at one point. They were a larger ID pipe that matched the Holbay head. The stock Alpine headers were smaller ID and did not match the Holbay port size.

 

[alpine_64]

I have a complete S3GT engine and the cast headers look just like the SIV/V ones, except there are only two manifold bolts.

View attachment 34047

Yes. That's the GT manifold on the S3 .. single outlet and single downpipe..

The later universal cast manifold with the twin outlet and twin downpipes:

 

[Alpine 1789]

Your picture seems to show a possible carb "heat shield." Any possibility of a couple of better pics since the heat shield topic came up in a recent thread?

It is pretty inaccessible at the moment, but I think you are just looking at the bottom of the intake manifold. I may have a better photo somewhere and will post it if I can.

Yes. That's the GT manifold on the S3 .. single outlet and single downpipe.

I didn't even notice the single pipe. I am not sure what I am going to do with the engine. One option, and the reason I rescued it many years ago, is to build a hot engine for my S3, keeping the original engine in case a subsequent owner wants to return it to numbers matching condition. The other option is to sell it, but no hurry on either.