Mixing parts with GRA..

Propane, Butane, LPG, GPL, C3H8, C4H10
gottago
Posts: 163
Joined: Thu May 24, 2012 7:39 pm
Location: British Columbia Canada

Re: Mixing parts with GRA..

Postby gottago » Wed Jul 27, 2016 12:09 pm

Nothing is stock or normal on this engine.. I've run other intakes and fuel systems on it without these issues.
Idles higher anytime afr approaches 15+.. Re-gasketted, checked all hoses and connections for leaks, timing and curve are basically the same. Machined the blank jet but not far off what was in the kit. Internal mixer leaks? Throttle blades are really large for a one barrel and I cannot drop the idle any lower off the idle stops without them sticking. Seems to be a fair bit of clearance around them for air to leak by. It was a used system. I can drop the idle rpm if I run quite rich and drop a bit of timing. No vacuum advance hooked up. Seems to be my only options at the moment. Run a rich afr or change part of the system. Don't really want to run it rich if I can help it.

I do agree that GRAs are a pain to tune but once you know how to tune them it's really not all that complicated.


Yes , I have a pretty good idea now what does what and I can get afr into a normal band. It isn't all that complex once you get the basic theory down and if these were new and did respond accordingly wouldn't be so bad. I stuck with trying to tune them longer than I usually would have due they run so nice on this at higher rpms. So yes, I'm probably knocking them a bit due I got used parts that aren't working as they should. Pretty well impossible for a long distance diagnosis on this I suspect.


gottago
Posts: 163
Joined: Thu May 24, 2012 7:39 pm
Location: British Columbia Canada

Re: Mixing parts with GRA..

Postby gottago » Wed May 17, 2017 2:11 pm

[img]
100_3927a.jpg
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Thought I'd share a few last comments on my gra setup. They are a learning experience and have their peculiarities but they do perform quite well once you work your way through all that. In the end I replaced all the inline progressive hose and idle jets with adjustable air valves. That made things much faster to tune and easier to coordinate. Discovered a small air leak in the primary mixer which cured the high idle problem. Eventually exhausted tuning options and concluded I am running too much ci, too much cam, and too high cfm requirements for the range these gra mixers wants to operate in. Best suited 5 - 5.7 litre max engine imo.

So, I am switching to dual ohg for this season. Thankfully this intake provides options to convert it from the sidedraft style into a mini tunnel ram.
100_3927a.jpg

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storm
Posts: 482
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: Mixing parts with GRA..

Postby storm » Wed May 17, 2017 7:17 pm

The 1st pic isn't showing
gottago wrote:In the end I replaced all the inline progressive hose and idle jets with adjustable air valves. That made things much faster to tune and easier to coordinate.
I'm very interested in this, can you provide more information/pics to how how this is setup.
gottago wrote:Eventually exhausted tuning options and concluded I am running too much ci, too much cam, and too high cfm requirements for the range these gra mixers wants to operate in. Best suited 5 - 5.7 litre max engine imo.
The largest they supply is a 510 cfm TB which is ideally suited to a 350/400 ci engine. Dual TBs can flow up to 1020 cfm but the tuning is more difficult and 1 should always be a secondary TB and connected to be at full throttle at the same time the primary is at full throttle. I have seen them successfully run 502 and 540 ci engines in dual TB setup.

The 2nd picture shows a different regulator than I thought you were running.
Fuel flow requirements calculations viewtopic.php?f=5&t=1638

gottago
Posts: 163
Joined: Thu May 24, 2012 7:39 pm
Location: British Columbia Canada

Re: Mixing parts with GRA..

Postby gottago » Thu May 18, 2017 11:58 am

Where the inline jets would normally go, I installed adjustable air valves. The first ones I got were not real suitable for fine tuning. The last ones were near perfect. Each click of the knob adjuster equalled about .5 on the afr gauge. The internals were of a good quality Teflon and brass. I believe they may even last quite some time. You may be able to zoom in on them in this picture.

Not too many GRA parts or replacement units around my part of the world. I believe I've only got a 420 and a 440. They were a bit misrepresented when sold to me. I can get nice idle nice cruise or lots of power, unfortunately not all on the same tune.

The reg is the big old century converter. Looks smaller in the picture for some reason. Fair bit larger than an x1 or model E.

Will be interesting to see how dual ohg mixers will perform in comparison. Same engine same everything.
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100_3928.jpg
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storm
Posts: 482
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: Mixing parts with GRA..

Postby storm » Fri May 19, 2017 12:01 am

I think when I get a bit of time I might have a go at that valve setup. You don't happen to have manufacturer and part numbers do you? I may be able to cross reference and get something similar to the ones you said are good.
Fuel flow requirements calculations viewtopic.php?f=5&t=1638

gottago
Posts: 163
Joined: Thu May 24, 2012 7:39 pm
Location: British Columbia Canada

Re: Mixing parts with GRA..

Postby gottago » Fri May 19, 2017 12:21 am

I threw out the packaging but I'll have a look see on the valve next couple days.

gottago
Posts: 163
Joined: Thu May 24, 2012 7:39 pm
Location: British Columbia Canada

Re: Mixing parts with GRA..

Postby gottago » Tue May 23, 2017 12:40 pm

Sorry, no name embossed on the valve. I got them quite some time back at an industrial parts supplier. They were advertised as being used for precise control over small air tools / air paint equipment / etc. Came in various sizes this being the smallest one. Had threaded fittings which I just adapted to hose fittings. Price was approximately 25.00 ea US.

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storm
Posts: 482
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: Mixing parts with GRA..

Postby storm » Tue May 23, 2017 3:46 pm

OK thanks for trying.
Fuel flow requirements calculations viewtopic.php?f=5&t=1638


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