E85Forum.com

quickd100 · Joined: 01 Oct 2005 Posts: 14

I've got a 11.2-1 440 in my truck that I've converted to E85. I richened the jets by 35%, opened up the Idle feed channel restrictions .004, installed a 50cc front acel pump kit with big pump cam. Running 6.5 hi-flow power valves, 12" of vacuum at idle, #46 squirters, and have opened up the PVCR's . I have no slack in the pump linkage, the timing is 38 degrees at 650rpm.
I've got a bog when I instantly nail the throttle wide open. If I quickly roll into the throttle it's fine. It idles, runs down the road, has exellent throttle response.
Anyone have any experience converting a 850 over? Any suggestions? Thanks Dave

specialgreen · Posted: Sat Oct 01, 2005 10:10 pm Post subject:

No experience with Holley; but when I did my Mikunis, I read
http://www.hardtail.com/techtips/alcoholconversion.html
for some general theory. That page talks about methanol conversion, so don't use the exact drill bit numbers.

quickd100 · Joined: 01 Oct 2005 Posts: 14

Thanks Special green I checked the link out. Methanol runs at a LOT richer mix than E85. The mods they made for methanol aren't even close to what's needed for ethanol. My carb is dialed in except for the bog. Dave
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1.595-60ft., 7.621-1/8, 12.19@105.88-1/4

specialgreen · Posted: Sun Oct 02, 2005 10:18 am Post subject:

On my simple carbs, there are a couple of things that can cause bog on instant WOT. If you can smoothly roll to WOT and get good response, but get a bog if you whack WOT, then the most common problem is that the slides are coming up too fast (Mikuni vacuum-operated slides, which pull the jet needle up in the needle jet, feeding the main jet). Partially plugging one of the two holes in the bottom of the slide makes it rise a little slower when you whack the throttle.

You can also bog on WOT if there is a momentary lean as the carb transitions to main metering. On my carbs, there is a needle which can be shimmed to make the transition a little richer. I think this is similar to the "shooter" on a Holley. You can increase the size of the shooter until you get a puff of black smoke, then back off one. If running bigger than 0.039, Holley sells a special hollow screw.

But if it were the shooter, then I think you'd still have some bog, even when rolling the throttle (not just whacking it).

I've only worked on motorcycle carbs (and old Volvo SA carbs), so you can probably get better advice at your local strip.

quickd100 · Joined: 01 Oct 2005 Posts: 14

I've always run the hollow screws for the squirters, I went up to a #55 squirter and still had the bog. The methanol boys only use a #45. when I get some free time I'll have to play some more with it. Right now I'm working 7 days a week and leave home in the dark and get home in the dark so as you can see I don't have much time to screw with it. Dave
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1.595-60ft., 7.621-1/8, 12.19@105.88-1/4

hotrod · Joined: 19 Apr 2005 Posts: 872 Location: Colorado

I know you have already looked at the accelerator pump squirter size and removed excess slack from the linkage.

I was wondering if you have also looked at different accelerator pump cams and the angles of the linkage to change the timing of the squirt on acceleration.

I'm thinking you may be delivering the accelerator pump squirt too slow or late in the the stroke.

On my hemi. (on gasoline) to get good rapid throttle motion response, I used to mess with the shape and length of my accelerator pump links and cams so that the first few degrees of linkage movement delivered a large fraction of the pump stroke then it tapered off as the linkage went to WOT.

I tweaked things so the accelerator pump arm was near right angles to the line of motion of the link so you got the maximum motion of the acclerator pump for the least motion in the link.

I would also tinker with the cam shape and the cam follower shape so the first part of the stroke would move across a steeply rising ramp on the cam then move to a more gradual lift for the rest of the motion.

This gave a pump shot that would look like the following if graphed

|.........*........................................................................
|.....*...........*................................................................
|........................*...........................................................
|...............................*....................................................
|..*.................................*...............................................
|............................................*.......................................
|.....................................................*.............................
|*............................................................................*.....

I'm thinking your symptoms might indicate you have a pump delivery that looks like below.

|.......................................*......*..................................
|.............................*.....................*..............................
|........................*................................*.......................
|.....................*.........................................*.................
|................*...................................................*.............
|.........*...............................................................*.........
|*............................................................................*.....

Hope that is understandable.

Larry

quickd100 · Joined: 01 Oct 2005 Posts: 14

Larry; I'm using the largest pump cam available, I think I've got it installed so I get maximum pump shot imediately. I'll have to get back to it after I'm done with harvest. Dave
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1.595-60ft., 7.621-1/8, 12.19@105.88-1/4