Welcome to Just Commodores, a site specifically designed for all people who share the same passion as yourself.

New Posts Contact us

Just Commodores Forum Community

It takes just a moment to join our fantastic community

Register

340 headers VF2

dessy

Member
Joined
Nov 26, 2016
Messages
40
Reaction score
32
Points
18
Location
Canberra
Members Ride
2017 VFII SSV Redline Sedan & 2014 VW Golf R
Cheers LS1SS
 

monstar

Naturally as-pirated
Joined
Feb 1, 2016
Messages
2,476
Reaction score
1,697
Points
113
Age
56
Location
depths of Hays Inlet
Website
facebook.com
Members Ride
Peugeot 207 GTi
Contact Andrew at Extracted Performance,these are the fotos he sent me re cat enquiry,they look good,evidently you can get 3inch or 2 1/2 dia pipe.Im looking at these but trying some thing out first,I have cut the pipes off my std cats and getting pipes made up and see how it goes,shal take fotos if it works well.
‘Bullet cats’ by themselves are $125-$150 each x2 so yeah around $550 the pair ready-made is OK.
558FAF46-F5F9-4518-92F4-306840CFF701.jpeg
Dimensionally if you have the 340 set with 2 1/2” outlet at the merge then may as well stick to a 6100+ top end tuning target for max HP. 3” downpipe is just too big for this engine.
Otherwise the 2.25” outlet of R8 is better TQ/HP balance for everyday, matched with 2” downpipe gets you more torque 95% of the driving time.
The main thing is space restriction longitudinally to the stock catback flange location of course. Ideally you want the length of downpipe 9” measured along the centreline before entry to cat. The HM (left), HSV (right) are easy cos bolt-on ready-made but downpipe is way short:
171051CD-DFA4-4905-A645-18C264CF6BEF.jpeg 746CBCBF-15C2-4374-A4A6-060FC3411B83.jpeg
So grafting the required mandrel bend moves HSV cat all the way rear, then just flange your cat’s butt :eek:
As you’re taking a hacksaw to it could do same with Holden VF cats (below), doesn’t matter.
3B5315F2-04F8-41A6-BDFE-29C5F51E4915.jpeg
Can hardly see down there, stainless won’t stay shiny at cat temps, silly to waste money on shiny branded stuff that is technically incorrect.
Deng Xiaoping famously said that it doesn't matter if a cat is black or white so long as it catches mice, here doesn’t matter which (bullet) cat as long as it has a 200+ cpi steel substrate.
Short fat barrel cat is better than long skinny for fit and theory, possibly not emissions.
Here is what I did with proper length mandrel downpipe:
C4257363-81EA-4652-8D08-14EAE8964413.jpeg 409688B5-CA76-4A02-9F4D-51090A6C443F.jpeg
CB9BEFAE-D1A2-4DE9-B2B7-344CAB7A9E7E.jpeg24035745-75DC-47E5-A789-D8428B78832D.jpeg
 

LS1SS

Active Member
Joined
Jun 25, 2017
Messages
228
Reaction score
164
Points
43
Age
70
Location
Milperra
Members Ride
VF Redline.1970 Dodge R/T Challenger 440 six pack.
That is a very good layman’s terms about cats Monstar,I’m experimenting with std VFll cats I took off my log manifold,I cut both pipes off the cats,I’m going to weld cat directly to plate weld another plate to my 2 1/2 R8 mid to get rid of cone flange then on inlet as you stated 2inch mandrel from cat to HSV headers and see if it all fits nice,just doing it as an easy cost exercise for blokes that want 400s and remain inside smog laws,as I go I shall take fotos.You can’t get HM cats off the shelf any more as they are now insolvent.
 

VF_CalaisV

New Member
Joined
Aug 11, 2017
Messages
22
Reaction score
16
Points
3
Age
46
Location
Melbourne
Members Ride
VF CalaisV L77
Mine is a 6.2,I didn’t know cats stink if you just change just the cats only,then why do long tubes with cats don’t stink? The path I was heading for was to cut both necks off the VFll std cats widen the mouths a tad weld a flange directly to the cat one end then get a nice 2.1/2 mandrel bend to the other end to HSV headers,hows that sound? I have the back sensors neutered already,once I get it figured out it’s off for a tune,if it doesn’t work it’s Hurricane 4-1s.
That's exactly what I am considering doing..
I'm just waiting to find out which cats actually flow best, either the VE-VF S1 or the VF ii. By looks you would think the earlier ones since they are larger... But the VFii cats don't seem to have lost power and the smaller size helps get nicer bend sections in before the standard CAT back location.
Actually it looks like the VFii V8 CATs might even be the same as the LFX V6 CATs?? Does anyone know?
 
Last edited:

Nico36

Member
Joined
May 13, 2012
Messages
65
Reaction score
17
Points
8
Location
Australia
Members Ride
VF2 SSV Redline
Well if anyone was interested in the update my redline ended up making 385kw with VCM OTR, 340 headers and 2.5" centre section and tune so pretty happy with that. Sounds great with bimodal fuse gone.
 

lmoengnr

Donating Member
Joined
Jan 15, 2012
Messages
6,889
Reaction score
44,495
Points
113
Location
Sunbury Vic.
Members Ride
MY12.5 Maloo R8, MY12 Redline ute, Magnum 224
Well if anyone was interested in the update my redline ended up making 385kw with VCM OTR, 340 headers and 2.5" centre section and tune so pretty happy with that. Sounds great with bimodal fuse gone.

You have an extreme example of LS3's!
 

Nico36

Member
Joined
May 13, 2012
Messages
65
Reaction score
17
Points
8
Location
Australia
Members Ride
VF2 SSV Redline
You have an extreme example of LS3's!
I wish it was louder, but I think I am in the happy medium where it is a great note, decently loud with no drone whatsoever. I think if I start looking at other options to make it louder it will be less productive. Or maybe now a cam....... ;)
 
Last edited:

426Cuda

SUBLIME!
Joined
Dec 15, 2013
Messages
4,181
Reaction score
3,015
Points
113
Location
Wagga Wagga
Members Ride
VF Redline Sedan - A6 Spitfire MSE...
Well if anyone was interested in the update my redline ended up making 385kw with VCM OTR, 340 headers and 2.5" centre section and tune so pretty happy with that. Sounds great with bimodal fuse gone.
Great result. Without the WP price too!
 

MY17DIR

Active Member
Joined
Dec 19, 2016
Messages
269
Reaction score
177
Points
43
Age
44
Location
Gods Country, NSW
Members Ride
MY17 LE Director....
Well if anyone was interested in the update my redline ended up making 385kw with VCM OTR, 340 headers and 2.5" centre section and tune so pretty happy with that. Sounds great with bimodal fuse gone.

Awesome! Did you use the HSV cats aswell or go with 200 cell hiflow replacement? Apparently some good gains to be had in replacing the HSV cats too.
 

.05

Active Member
Joined
Feb 20, 2018
Messages
109
Reaction score
91
Points
28
Age
69
Location
vic
Members Ride
vl v8 commodore
most of the hsv headers i see with cats are sold advertised with no size of exit flange pipe size, 340kw are 2 1/2inch what size are the other hsv header pipes 2 1/4 inch ?
is there any difference between 325kw hsv headers to 340kw hsv headers power wise
everyone seems to only talk of the larger 340 ones
for street traffic light drags would i notice much difference between the two
or is it just you can pick them up for the the same price, might as well get the 340kw ones
 
Top