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which straight gas system should i use? 


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 Post subject: Re: which straight gas system should i use?
Posted: Thu Mar 04, 2010 12:24 am 
Getting Side Ways
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misk_one wrote:
seeing as you have the XF (assuming its cross flow? nto sure when they changed lol) i'd fit a 4 barrel manifold with holley 4 barrel baseplate and the imcp 425 ontop.
should be able to do it easily with the budget you have set.
the 425 can support a fair bit of power if its setup correctly.

Xf's were all cross flow engines. It depends on if pepeguts has a EFI setup or carby setup on the engine. You could adapt the 425 to the EFI intake with a little work, but more work than the way you propose with the holley baseplate & 4bbl manifold.





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 Post subject: Re: which straight gas system should i use?
Posted: Thu Mar 04, 2010 7:31 am 
Parts Gopher

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Guys,i forgot to mention the xf has a AU Engine running ef electrics / ecu.I notice there is a bit of conflict about GRA system`s!
 Post subject: Re: which straight gas system should i use?
Posted: Thu Mar 04, 2010 7:51 am 
Getting Side Ways

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Interesting - This has been my feeling as well. Theyve talked it up a lot - I remember the original display at Summernats for it.

Ive had 2 GRA Systems - One on an I6 EB, and the other was a twin System on a 351C (Fresh) in an XD. Really didnt like either of them.

The Progression from Idle to Drive was awful, and they are *extremely* sensitive to altitude variation. Makes tuning the twin systems hard (Try altitude difference from Melbourne to Canberra) - the Crossover into the second carb was the largest flat spot Ive ever known.

To be honest, the most drivable systems Ive ever had were Impco. yeah the economy can be average, but in my XD with a 4.1 I used to pull 500-600km/tank on highway (Impco 225), and had one of the torque'est engines at the time (Headwork done by Superflow...) Ive driven cars with 425's, and while most are a little rich at Idle, they just drive.

Ive had OMVL gear, Vialle and other gear and really havent every been imressed.

I love the injection systems, and my next project will be injected. Probably the Impco Version as I hear its good for Boosted apps as well.


[quote="luke111"]I have a Impco 425 on my EF 4L straight gas.
Originally had a impco 225 mixer, but after some basic manometer testing it was proven to be too restrictive. Changing to 425 also improved 0-100 times by 1.5seconds and litres per 100 improved by 2L/100!
Had to make up the pipework & adapters myself, used a B2 converter.
Bought parts on eBay, got the 425 & airhorn adapter new on eBay from the usa.
Since this pic was taken I have changed the plastic intake pipe going into the airbox lid, it was found to be too restrictive as well. I have changed it to a 3" pipe with a bellmouth in the top of the lid.
Total restriction now is 6" of H20 at the top of the mixer.

You'll never have maximum power using simple converters. You need to have a pressure drop (restriction) through the mixer to help draw the gas out of the converter.
Only way for max power is vapour injection system.

Stay away from GRA. Its crap. GRA is as primitive as it gets. Economy is the worse than Impco.
I worked for GRA for a little while a couple of years back and left in disgust - both at the equipment and the company.
They aren't worthy of your money.
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