STANDARD SINGLE exhaust size?? Trivial question.

**Innuendo** · 09-06-2015, 01:50 PM

My research shows 2" for 308 in a single system.

Genuine Holden Accessories also only lists chrome extensions for these three sizes.

1 5/8" ID
1 3/4" ID
2" ID

The answer for Agro is you were both wrong. Sorry mate!

**HK1837** · 09-06-2015, 02:26 PM

I just checked it up and also looked at my Premier which has its original exhaust except the muffler. The pipes are 2" and the muffler is the same for 6cyl and V8 which is 1.75". It does appear to be a bit more complicated in HQ though as there is 1.75" chrome tips listed for 253 and 308 (although this may be for twin 1.75" tailpipes on 253) and the 350 engine fits in amongst it all too.

**Innuendo** · 09-06-2015, 06:03 PM

HQ and HJ dual systems (Holden V8) were pea-shooters and never 2" from factory.

**HK1837** · 09-06-2015, 06:51 PM

I'll double check when close to info but I think at least the dual system engine pipes were 2", and stepped down at the mufflers. The original cars I've looked at looked to be the same size pipes onto the manifolds as my Prem.

**Valencia** · 09-06-2015, 07:13 PM

Originally Posted by HK1837

This awful exhaust is the main reason why there is around 20hp (maybe even more) difference between a HJ 5.0L with a single exhaust and the same car with a dual exhaust.

Originally Posted by Innuendo

HQ and HJ dual systems (Holden V8) were pea-shooters and never 2" from factory.

Neither did V8 SLR 5000 Toranas

**wbute** · 09-06-2015, 07:15 PM

My blue wb had the poxy single on it. Factory 4.2. No way it was 2 inch anywhere on the system I don't think.

**HK1837** · 09-06-2015, 07:23 PM

Originally Posted by Valencia

Neither did V8 SLR 5000 Toranas

AFAIK LX 5.0L and SS 5.0L did. It gave them a significant performance gain over the LH versions that had the step down mufflers. These cars were the quickest LH-LX Torana (until ADR27A killed them!).

**HK1837** · 09-06-2015, 07:31 PM

Originally Posted by wbute

My blue wb had the poxy single on it. Factory 4.2. No way it was 2 inch anywhere on the system I don't think.

I think you'll find the engine pipes were 2" - I don't think that changed right up to WB. Here are the Prem's pipes. These are original, I took them off to remove the TH400 to fix the rear welch plugs. Tailshaft on these is 71mm diameter for a reference.

backin3.JPG
backin2.jpg

**wbute** · 09-06-2015, 07:33 PM

Could have been. Was 20 years ago they went in the tip.

**HK1837** · 09-06-2015, 07:52 PM

The only Torana I've found so far with any original specs is the L34. It had 2" engine pipes and 1.62" tailpipes. I think this was the same as normal L31 SL/R as well as exhaust past the headers was free under Group C.

I also just looked up the HQ Service manual volume 4. It states as I thought all along:

Engine pipes - L6 1.875" OD, V8 2" OD. Tube thickness 0.06".
Tailpipes:

L6 1.625" OD. V8 engines (except GTS350 or N10 dual exhaust (253 and 308)) 1.75".
GTS350 or N10 dual exhaust on 253 or 308 - 2".

As far as i'm aware HJ-HZ was identical (except no 350).

Note this is passenger vehicles. The HQ commercial vehicles supplement issued in late 1971 shows the exhaust differences (mounting) but makes no mention of any size in pipe changes (it would if they were different).