Gra onto ea centre point manifold.

[Ando81 2,949]

Hi all, this is probably a simple question but I've been considering a 4 litre conversion in my xf ute and it's on gas. Was wondering if I could adapt a gas research throttle body to an ea centre point inlet manifold. A mate of mine has a 500 holley on a centre point manifold on an ea motor in his speedway car and it's got plenty of power but I do a few kilometers in my ute so need gas for the fuel economy. I thought I could run modified xf dizzy and coil on an au motor. Am happy to hear your input positive or negative. Thanks lads.

[PRO250 1,506]

I looked at it a while back on a ea it will work with little work

another way is a 4barrel manifold 425 impco and a super mega drag cam in your engine there good on fuel and will make the same power

[Ando81 2,949]

That would save me a lot of work Dave, and probably be similar gain in power! Cheers mate

[gerg 10,871]

Gas needs more cam and manifold to make the same power as petrol so Impco 425/aussiespeed would be perfect. I've heard they're good for 180 RWkW but that would be the absolute max. A Ford 6 making that much would be off its tits, which I assume yours won't be. High performance V8s can use two of them.

 

A GRA will be harder to tune and the CFI manifold will run out of puff over 4000. Would have nice torque though.

 

Impcos, being a CD - type carby (like an SU) are a bolt-on proposition that should need no adjustment. The engine sucks x amount of air so it provides y amount of fuel. Beautifully simple!

[Ando81 2,949]

Thanks gerg, that makes it sound much simpler now. Great work

[Jonathan Mark Davidson 169]

why not the gra onto the log or bbm type manifolds i have one hear that bolts strtaight up

[Ando81 2,949]

Yeah, never thought of that mate, the log manifold would make it all sit even lower under the bonnet.

[Ando81 2,949]

So have you got a log manifold or gra throttle body?

[Jonathan Mark Davidson 169]

yes i have both but not currantly together especaly with the super long country miles i like to do where gas aint avalible

and yes i'm willing to sell my gra

[Stevemack 122]

GRA are way better than anything else on the market IMO, had one for 14 years, you need to get it tuned properly (metering rod machined) about once every 4 years, but otherwise you never have to put a spanner on them!  Instant power, impcos i have found can get flat spots and need regular adjsutments to keep them at their optimum.  Go GRA mate, you won't look back.

[Ando81 2,949]

yes i have both but not currantly together especaly with the super long country miles i like to do where gas aint avalible

and yes i'm willing to sell my gra

 

I'm still undecided as to which way to go about it mate but what sort of price are you asking for the gra setup?

[dizzy616 183]

log manifold ring mixer and a + type system with a omvl r90e convertor. if its allready got that type system installed cant go wrong. id only work with dinosaur impco stuff and b2's on cars with that type of system all ready installed.
r90e is a nice convertor their nice and tunable. also have dual outlets if you want to run twin throttle body. one thing i kind of pondered. twin throttle body with 2 ring mixers. unless you can use gra throttle body with omvl.
seriously now one of my prefered and favored convertors.
went well off the line with ea cam.
put this other crow cam thats suitable for gas in. but sware ea cam gave it more initial oomph. but i never have had enough time or money to put it to the test.

[Stevemack 122]

I used GRA with B2, bomber setup on a stock 351.

[Jonathan Mark Davidson 169]

I'm still undecided as to which way to go about it mate but what sort of price are you asking for the gra setup?

dont have a qule it owes me $150 plus postage

[Ando81 2,949]

Got any pics mate? So is it ready to use like it is?

[Jonathan Mark Davidson 169]

i'll grab some in the next day or 2 and yer ready to roll even has a e series tps on it

[Ando81 2,949]

No worries mate, am interested for sure.

[Jonathan Mark Davidson 169]

sorry dont have internet acsess every day only when at work i'll pm you as itwill be easyer to mms you pictures

[blackxt 699]

Gra on a centerpoint will work with the correct adapters. Heaps of setups done like that before. I'm running a impco 225 on a mulitpoint manifold ATM but its very restrictive , I'm in the process of having a motor built that makes around 200rwk on petrol , its just street drivable , but I'll be running a Aussie speed 4 barrel and gas research . Looking forward to seeing how it goes.

[Ando81 2,949]

Just bumping this thread again as I scored a cheap efi crossflow the other day. I'm thinking of putting a better cam into it and open to suggestions to better towing performance. My current carb fed crossy goes reasonably well on petrol but just does nothing on gas. Am wondering if it is just the standard camshaft that restricts the gas power or could it be the r90e converter and gas ring mixer on top of the weber carby. I had my local mechanic tune it to suit the gas but it's really sluggish. It's doing average 16litres to 100km so I don't think there is any restriction getting gas into the motor. I don't know a lot about the impco mixers, are they for straight gas setups?

[gerg 10,871]

Yeah straight gas as in non-carby. You can have an impco on EFI that goes inline in the snorkel like on my old EA, but wouldn't be feasible on a carby set-up.

 

Dual gas on carby is just the worst possible combo you can have. Reason being, once the gas is mixed into the air, it takes up a larger volume thus more cfm required for the same power. So instead of your Weber normally flowing say 300 cfm of air on petrol, it now has gas/air mixture squeezing through it so it could be more like 250 of air and 50 of gas.

 

Impco 425 on a progressive holley base is the go I reckon.

 

If you must use the Efi manifold, inline impco will work but GRA throttle body would be a neater job.

 

Say your goal for a gas motor is 150 HP at the wheels, build the motor to make 180 on petrol.

 

16l/100km is ok, my straight gas Corty got 15 all the time.

[gerg 10,871]

Cam selection: pick the one you'd use for running on petrol and choose the next one up for gas. Reason: It has the effect of taming bigger cams and ports due to abovementioned extra volume taken up.

[Ando81 2,949]

That's all great help mate, thanks for that. I'm leaning more to straight gas with say a 4 barrel impco setup. Don't really want to run efi induction. I know stuff all about gas so bear with me here, if I bought a gas research setup off a 302v8 could I put it onto a 4 barrel crossflow manifold?

[gerg 10,871]

Any carby or mixer is just a fuel metering device. It doesn't care what it's bolted to, so a V8 setup would be fine, if a bit toey off idle if you don't have some sort of progressive linkage that starts slow and opens more quickly as you go. GRA mixers are like a bike carby, x amount of throttle opening gives Y amount of fuel, depending on the needle and jet you use. It doesn't self-compensate like a diaphragm mixer does, which senses flow, not simple throttle opening. They can potentially make more power than an Impco, but might need to be tuned by someone who knows whatthey're doing for best performance.

[Ando81 2,949]

Awesome mate, I could prob get it to run but would definitely get it tuned properly to be safe.