Alternative Fuels

The stock heads are quite limited but should still run you up near 4500 rpm with half decent numbers. I'd just keep working it and set it up best you can for now. I'm a long ways of, Okanagan valley B.C. Too bad, I have somewhere around 30 spare 425 impcos in various conditions. Yeah, all the numbe...

Thanks for your time/thoughts Storm. I'll keep working away at it. Hopefully one of those guys will stop by as well.

The aftermarket springs/adjustable vacuum pot/timing tape need to be on my shopping list! No 425's around down here. Have only ever seen one listed on the local 'Ebay' deal. I feel like it's not tooo far off, but it certainly isn't right yet... Storm, I should have said, I have the 50-70 so that's n...

Converting Lambda back to AFRs for LPG will give you 1 Lambda = 15.5 AFR, 0.89 Lambda = 13.8:1 AFR, 0.85 Lambda = 13.2:1 AFR. Going by these numbers your WOT could be left alone or slightly richened up but your cruise after 2200rpm is way to rich. I'd also Richen your idle back to 15.5. Now I have ...

As of half an hour ago this is where I'm at. 9 initial/20 centrifugal/11 vacuum = 40 degrees total advance. Idle rpm 600 9 degrees - vacuum disconnected, in Drive 1000rpm 9 1500rpm 17.5 2000rpm 22 2500rpm 29 (all in) AFR Idle 16 Moderate acceleration 13 Cruise to 2200rpm 15.5 Cruise after 2200rpm 13...

Thanks for all the information guys. I've reduced initial to around 9 degrees, installed the 'black' advance stop bush, and that has dropped the initial/centrifugal from 36 degrees to around 28 degrees. Tomorrow I will make up some vacuum advance stops and drop that from 16 down to 12-14 degrees. I ...

I'm starting to get the feeling you's think I should change my timing!? :mrgreen: Storm, I'm all ears. Not harsh at all. The graphs below show the curve I currently have, and the advance stop options. I may have to make/buy an adjustable vacuum unit too.... I can't find an OEM initial setting yet. B...

Hey Storm. I am obviously going to have to make some changes. In my defence. I set the timing after reading alot of stuff, and alot of stuff by Lars Grimsrud. I've put nearly 12000 kms on the truck in the last 13 months. Completely trouble free. Fires up cold after a couple of pumps on the Quadrajet...

So the 400 in the truck is probabley stock, has the second worse heads Chevy ever made on it, and unknown miles. It does have even compression, steady vacuum, full MSD ignition/leads, and starts great petrol/LPG. I've got the timing set up more for LPG. All the advance in before 2500rpm. I am runnin...

Man I know how to drag out a simple job huh!... Nearly eleven months mucking with this. I apologise for not updating sooner. I never did win with adjusting the springs on the air flap. I went back and forth (tighter/looser) twice but couldn't get any improvement. Obviously, in some situations it wor...

I've recently got my 72GMC K2500 with a 400 small block running on LPG. I'm going to run dual fuel with a 300A setup. All Impco components rebuilt. I have an Innovate wideband O2 setup installed. On first start up we got it running/idling well showing 12 on the O2 gauge. Over the next couple of runs...

there is a depression caused by that mixer that does interfere with the Quadrajets secondary air flaps. Tweaking the spring load did the job for me. Still going back and forth on this....Spring is now nearly back to where I started with no change. Just to clarify that I am interpreting this correct...

Ok, so we're going with secondary airvalve spring adjustments first. And my first attempt to unwind it was a complete fail! If this is the answer, it's going to be a small adjustment.... I backed it off and ruined starting, still had overly rich acceleration, and richened up my cruise. Ran out of da...

Yeah my initial reaction was 'stupid filter', but then I took it off and had exactly the same results with just the mixer on.

Over view of filter/converter, and mixer in place. 20160705_202218 (640x480).jpg 300a manually opened 20160705_202500 (640x480).jpg 7042208 Quadrajet 20160705_202811 (480x640).jpg Adapter front view 20160705_202942 (480x640).jpg Rear view 20160705_202705 (480x640).jpg Anything leaping out at you C3H...