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 Post subject: Re: Exo Hot Rod
PostPosted: February 25, 2020, 5:26 pm 
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Location: Omaha, Nebraska
TRX wrote:
Fuel pressure 6 to 8 PSI?

Floats actually floating? Yes, tested both when I was rebuilding the carb./

No dried-up gaskets between the metering blocks and main body? Everything immaculate, cleaned during the same full rebuild

Jets present in metering blocks? Yes, I checked again today. (hoping to find a stupid simple problem)

Jet orifices consistent with markings on outside? (not reamed out) Brand new jets from Holley

Fuel only coming out of accelerator shooters when pump is worked? Yes, and the little check valves are underneath.

Needle valves actually stopping fuel flow when closed? (invert bowl, blow on a hose connected to the fuel inlet to check)
Pretty sure, but I'll test again.

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 Post subject: Re: Exo Hot Rod
PostPosted: February 25, 2020, 6:08 pm 
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So I went over all of the carburetor happenings again today, pulled it apart again to check for simple or obvious problems, verifying that all is to Holley's specifications, and found myself looking again first at my tuning book then at various forum pages found by searching every version of the problem that came to mind.

I understand a few things now better than I did before, or maybe I just needed to be reminded of things I've forgotten, and I have a new guess as to the problem (it's a little complicated, or at least it has multiple parts/stages):


Setup problems:

1) The idle air bleeds are a little too big for my application, so steady-state off idle is a little on the lean side.

2) The power Holley specified power valve (6.5) is too low of a number for my application (idle vacuum 20+), so the primary main circuit has a significant lean spot.

3) The carburetor had the choke removed at some point in its past, so it's a little hard to start when chilly.

4) These factors combine to make the engine very difficult to get up to temperature, since the idle is set a bit lean for cold start, but opening the blades more gets into even leaner territory causing the car to stall.

What I did, and how it ran:

1) I'd give the carb a couple full pedal jabs to squirt fuel into the manifold for starting

2) I'd start it up, and it wouldn't want to stay running because of the problems above, so it would die.

3) A few more pump shots, and start it again, but again it wouldn't like to stay running. (Exhaust looked and smelled crazy rich while I was doing this.)

4) This process would repeat 4-5 times before I could get the throttle opened enough with the car running that it would run well (and it would run pretty well).

5) When the engine was up to temperature (thermostat opened), it would finally idle just fine (not as smoothly as I would like), and sounded great with the throttle open into the primary circuit, but it still stumbled a bit off idle. Not a crisp or smooth transition opening or closing the throttle.

What happened:

1) I fouled the plugs by dumping pump shot after pump shot trying to keep it running when cold.

2) The fouled plugs made it harder to keep running when it was cold, exacerbating the problem.


The solution(s):

1) New plugs -done

2) 10.5 power valve -tomorrow, maybe

3) Adjustable idle air bleeds - not until I test the new power valve


I have no idea if any of this is correct, but it's what I'm going to try next.

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 Post subject: Re: Exo Hot Rod
PostPosted: February 26, 2020, 9:10 am 
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Joined: September 22, 2005, 8:12 am
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Location: 4AGE in S.E. Michigan
3) Adjustable idle air bleeds - not until I test the new power valve.

I had the same issue, with a modified engine. I put tap over the air bleed holes. Then used a needle to open up the air bleed, until I had a smooth idle. I then filled the air bleed port with a little epoxy, and then used a pin drill the same size as the hole in the tap to open up the ports. note; go slow on opening the hole in the tap, start at about half of the stock dia. davew


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 Post subject: Re: Exo Hot Rod
PostPosted: February 26, 2020, 11:15 am 
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I've been down the Rocky carburator road before and don't miss it. Just wait until you drive up into the mountains and have issues with the altitude throwing off the mixture. Thank you for reminding me why I went with EFI!

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 Post subject: Re: Exo Hot Rod
PostPosted: February 26, 2020, 8:17 pm 
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Location: Seattle area
Just replacing the plugs? Anything wrong other than fouled? Had a rich running 4AGE Toyota. Discovered that a propane torch would clean them up just fine. Check the gap and you're good to go.

I built my Locost at Creative Auto Solutions in Council bluffs. Moved to Seattle in 2011. Sorry I missed you.

Cheers,

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 Post subject: Re: Exo Hot Rod
PostPosted: February 26, 2020, 9:23 pm 
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Location: Omaha, Nebraska
I replaced the plugs instead of cleaning them because they were the old GM spec gap of .060" (new is .040"), more prone to idling problems, and they were pretty thoroughly fouled. It was only about $18 to replace the set.

Now, if I foul these new plugs while I'm trying to sort out the carb issues I'll be cleaning.

I didn't get the power valve changed over this morning before work, I spent my garage time reinstalling the alternator with the newly-painted bracket because my wife bumped her head on it where it was hanging to cure in the basement, but I may have time this evening.

The big, beginning of the 'car' season swap meet in Lincoln is on March 8th, and I'll probably drive over and look for locost bits. Hopefully I'll have time to run the car with this carb over the weekend so I'll know if I'm looking for any carb parts as it's a really good place to look for cheap stuff of that type.

I'll probably end up with fuel injection on this motor someday, but for now the carburetor is intriguing with the subtly interrelated circuits and incomplete/conflicting information from every source. Studying a dark obsolete art.

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 Post subject: Re: Exo Hot Rod
PostPosted: March 9, 2020, 1:10 pm 
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I ran the engine yesterday, and it was much better. I can't be sure why, because several things had been changed: wire in the idle air bleeds (secured this time), 10.5 power valve (which is the one I should have been using in the first place, but I'm not sure it came into play at all yesterday since I never saw vacuum dip under 15", this engine idles at 23"), and new plugs.

I did not yet pull the plugs to look for mixture.

One thing I learned yesterday was that I previously had the throttle blades too far shut, being paranoid about having them too far open and trying to get the idle as low as I want it. Yesterday I began with having them open to the typical .030" reveal, and the off idle transition worked pretty well, but then I closed them a little more to get the idle down lower (which it did) and it wanted to hesitate off idle. Turned the idle screw in 1/8-1/4, the idle speed rose and it came off idle much better.

So, I think the transition slot needs to be slightly uncovered at idle so that the engine vacuum is continually pulling at the transition slot. This way the fuel is 'ready' when the throttle blades begin to open from the idle position (this is my theory). No one much talks about having the throttle blades shut too far at idle.

I'd like to get the idle speed a little lower. It's not high, but to me it sounds like it's not as low as this engine would sit comfortably when warm. The secondary butterflies are adjusted to spec, and I'd be nervous to close them any more, lest they bind, but I might experiment with that a little to see what it does at idle.

Went to the big swap meet in Lincoln yesterday and picked up a cheap 650DP missing some parts. I may have reason to use some of the parts it does have, and the price was right. If not, I'll price out what it would cost to get some of those parts, rebuild it, try it on the engine to see what it does, and maybe sell it. Or maybe I'll steal the parts from the 700 on there now. The 650 does have a choke.

I also found a great new bench vise to replace my broken, cheap, little old HF one. I'll post pictures. I love it.

-Graveyard

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 Post subject: Re: Exo Hot Rod
PostPosted: March 22, 2020, 8:59 pm 
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Location: Omaha, Nebraska
I was working on brake pedals, but decided that I'd like to tackle the steering first, since the exact location of the shaft will effect where I can put the pedals.

I'm doing it with 3/4 hollow DOM, steering heim, firewall flange sleeve, and a Sweet Mfg. 17mm DD-3/4 round u-joint.

I could actually make it work with only one u-joint, right at the rack, but I'm wondering if I shouldn't have two. Does anyone know about this, or have an experienced opinion?

I know that less angle is better, in general, but do two u-joints cancel each other out if they're 90 degrees clocked relative to one another and operating at the same angle? Also, does the presence of two joints between the last support of the column and the rack eliminate the possibility of misalignment? I've been searching for good answers to these questions, but haven't found anything yet.

-Graveyard

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 Post subject: Re: Exo Hot Rod
PostPosted: March 23, 2020, 6:45 am 
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Assuming the single joint is operating at an angle greater than zero, it would be the equivalent of having a rack ratio that increased and decreased with each rotation.

Having two joints allows the steering wheel and the rack pinion to turn at the same rate for a consistent rack ratio while the intermediate shaft changes velocity as it goes round, the same as a driveshaft.

Unlike a driveshaft, the intermediate shaft rotation is so slow that the speed changes do not cause a vibration problem no matter how great the joint angle.

I’ve seen where some steering joint mfgs have recommended out of phase but I believe that is based on very outdated info.

I’d forgotten about your carb issues. I used to run carbs as big as 850 but only on big blocks. I prefer 600-650 vac secondary for smallblocks for best driveability with or without a lot of overlap.

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 Post subject: Re: Exo Hot Rod
PostPosted: March 23, 2020, 10:17 am 
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General guidelines for driveshafts do not fully apply to steering. As MV8 said, you are not turning the steering wheel at 4,000RPM. They are not bad guidelines to design with if you can do so with minimal issues. Remember that even if you follow those, the guidelines work for parallel input and output shafts. This will most likely won't be the case for steering shafts. Bottom line is 1 or 2 or more u-joints can be used IMO without serious issue. IMO, the human brain is very adept at immediately and continuously calculating the desired steering wheel angle for any desired turn and correcting. Even so, if using 2 joints it is good to clock them appropriately.

like MV8 has said, I have read that sometimes the desired clocking of u-joints in steering assemblies is not 90 degrees. I don't know the reasons. Perhaps it is due to the different shaft angles being connected? Not sure. I will say that the lower the shaft angles, the lower the issue is.

For a reality check on my observations, I would suggest referring to tilt steering in a regular car. (I included tilt steer in my locost) There is a u-joint in the steering column that changes angle as you tilt up or down. I have never had an issue with odd steering behavior related to tilt angle.

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Visit my ongoing MGB Rustoration log: over HERE

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 Post subject: Re: Exo Hot Rod
PostPosted: March 27, 2020, 5:52 am 
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Here in NZ the certifiers like to see finely splined joints on the UJ's so that any notchiness in feel can be "phased out", given that not many installations have parallel input/output.


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 Post subject: Re: Exo Hot Rod
PostPosted: April 12, 2020, 7:29 pm 
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Location: Omaha, Nebraska
Just a few related side projects/interests from the past month I thought I'd share:

One of my boys broke his trike, so I told him I'd turn it into a 'monster trike.' Some HF wheels left over from an old version of a welding cart and some light-weight steel rod worked just fine. He loves it. Faster, smoother, quieter. Took a few hours. Still needs paint.

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I also went to one of the big swap meets at the beginning of March, and picked up a Holley 650 DP body with mechanical choke. My 700 is working pretty well now, but it was cheap enough. I'd have taken a picture, but it just looks like a Holley. It acme with both bowls, but both are junk. The base plate might be a little smoother than the one on my 700. I'll decide that if I ever swap it out. But that's not the big thing from the swap meet: I've also been looking for a good used vise. Something vintage and heavy duty, but not too expensive. My old little HF vise has been all but destroyed by some of the heavy work I do. Here's what I found at the swap meet for $40 (the old HF is next to it for reference):

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The new vise is a revelation. Smooth, easy, and dramatically more powerful. It just holds stuff. Seems like a simple thing, but maybe the best $40 I've spent on a tool.

Next update will be actual car stuff. I promise.

-Graveyard

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 Post subject: Re: Exo Hot Rod
PostPosted: April 12, 2020, 8:15 pm 
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So, one of the other things I've done in the last few weeks is build a custom reverse-mount hanging pedal assembly. Looks (or looked) like this:

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It's a little heavy, but not absurdly so. Much stiffer than aftermarket assemblies, with bronze bushings, and with closer tolerances. Over-engineered, certainly, but cool-looking and quality-built.

After all that, however, I re-decided that I do want floor mount. Space is very tight down there, but the hanging version comes with its own compromises. So now I'm planning a custom floor-mount assembly. Hopefully I can reuse the master cylinder mount portion of what I already built. I already cut it apart.

In my mind, these pedal difficulties exemplify the difficulty in building a one-off car; everything is a guess that needs to be changeable or adjustable if at all possible. It can't be built, tested, developed, and then rebuilt time and time again. Fortunately, the drivetrain and suspension were thoroughly developed (though not for this application), and cage-based chassis building has been tested in various racing series for decades, so I'm not guessing about everything.

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 Post subject: Re: Exo Hot Rod
PostPosted: April 12, 2020, 8:19 pm 
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Quote:
Here's what I found at the swap meet for $40 (the old HF is next to it for reference):

Attachment:
IMG_0517.jpg


Attachment:
IMG_0518.jpg


The new vise is a revelation. Smooth, easy, and dramatically more powerful. It just holds stuff. Seems like a simple thing, but maybe the best $40 I've spent on a tool.

Next update will be actual car stuff. I promise.

-Graveyard


If I'm not mistaken, the Ridge Tool Co. of Elyria is now known as RIDGID.

Nice find, especially at that price. Not much beats a solid old US-made vise.


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 Post subject: Re: Exo Hot Rod
PostPosted: April 13, 2020, 8:17 am 
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Love the vice. That pedal brkt is a work of art. I prefer reverse hanging.

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