Pawk

There seems to be not a lot of support for shorty style headers on most forums but given I'm not willing to wear any additional clearance woes on an already lowered car, why wouldn't these be better than a stock exhaust manifold? They're 1 3/4" primaries into 3" collector.
I would fit them up to high flow cat's and then thru the standard dual 2 1/2 " system.
This is my 1st mod to a currently stock LS1 manual Aussie Monaro ( your GTO), only other mod's planned are CNC ported 243 heads, mild cam ( up to 220 duration, .580 lift & 114-115 LSA ) CAI OTR & a tune to take advantage of 98 octane fuel.
I'm not after an attention seeker or strip terror, just a good solid daily driver.
Thanks.

bww3588

iTrader: (49)

For the cost and hassle of install, they are not worth hardly any gains over stock manifolds. Look into mid length headers if they make them for the GTO. About the same price and will provide more gains without giving up ground clearance.

99Bluz28

iTrader: (35)

The gains aren't as good as LT headers, but there still gains. I'd just run a wider split on the exhaust duration.

redtan

iTrader: (5)

Given that they're 1 3/4ths (over 1 5/8ths for GTO JBA shorties) you should be able to gain some good power with those and midpipes.

I would say somewhere around 15-20rwhp or so.

elephantrider

iTrader: (2)

my gto is lowered and have no ground clearance issues with kooks long tubes...

bww3588

iTrader: (49)

You're forgetting how well the later exhaust manifolds flow...I'd think you'd be lucky to see 5-15 over stock exhaust manifolds. Anything else would be attributed to higher flowing cats or lack thereof/better mid pipes, not the shortys over manifolds.

redtan

iTrader: (5)

True, but he's looking at this as an overall setup instead of getting LT headers.

While the actual header won't gain that much, the overall setup will be a good power improvement while not having to deal with the ground clearance issues of LTs.

stevieturbo

Some of the Aussie cars have shorty tubular manifolds from the factory, cant remember which specific models they are though. They are about 1 5/8" diameter
Or maybe check out some of the latest HSV stuff ?

Not actually sure what RHD mid length manifolds are available ?

ls1.com.au would probably yield more options

Pawk

I believe these are what was factory fitted to the VY2 HSV's. They reverted to the factory cast manifolds after that model -2003?
I'm not really that worried that I'd be giving up that much power Vs long tubes, providing there's some benefit over stock but if that only comes at the top end of the rev range then that's an issue . My aim is to have kind of a factory hipo version of the monaro, something like an "LS6 plus",not a drag racer.
Given that I'm starting with a stock 350HP LS1 and only other mod's planned are CNC ported 243 heads, mild cam ( up to 220 duration, .580 lift & 114-115 LSA ) CAI OTR & a tune to take advantage of 98 octane fuel are the shorty headers going to be detrimental compared to the stock manifolds?
Assuming I go with the shorties, any suggestions on actual cam specs and compression ratio would be welcome.

99Bluz28

iTrader: (35)

As far as cams take a look at the EPS TT1 (214/220 115lsa, lift .600"/.564"), *VHP #243 ( 214/ 222 115lsa, lift .585"/.585"), Crane #1449071 (216/222 116lsa, lift .585"/.585").

*Crane grinds the VHP cams.

Pawk

Thanks, will look into those.

Pawk

Any chance you have some under car photos you could post?

stevieturbo

Dont forget, Kooks probably do not make a RHD set of manifolds.

A friend has DiFillipo on his Monaro, and wouldnt say they are too low.

Pawk

What's too low is a subjective thing. I''ve seen guys with 2" of clearance that don't think they're too low & also heard of guys ditching their Difilipo headers coz they hang too low and scrape on every bump. My car has a little less than 4" clearance at the right side front pipe , local law says 4" minimum at lowest point. I'll be seeing a local exhaust guy that reckons shortys are a waste of time and he can fit up the long tubes & cats with no less clearance. I doubt that's possible but we'll see.