LocostUSA.com

If you get me the list # for that carb I can look it up in the book at the race shop.

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Honey anyone?

Really like the styling of your build - thanks for posting the updated photos. Hope you get the first "under its own power" drive in soon, looks so tantalisingly close - but that last 20% of the project...

Oh my, the carb...

It's a 700 cfm double pumper, list 4778-1, which I bought at a swap meet for $10, then spent $90 rebuilding. And now, well, it doesn't work very well off idle.

After a very thorough cleaning I put in all new gaskets, new needles and seats, new jets to Holley specs, new squirter check valves (old ones were missing), new power valve (only one required for this carb, and, unfortunately, a new fuel bowl because the old one had stripped needle and seat threads.

The jetting in the carb was very lean compared to the Holley specs, so I found myself wondering if the absence of check valves under the squirters caused fuel to be somehow sucked through, enriching in unexpected ways, and causing the hapless carb tuner to chase the problem with ever smaller jets. I don't know if that could actually happen, but as I was restoring everything to original Holley specs, I thought it wouldn't matter anyway.

And the carb works fine now, except for off idle. It basically dies. I know that off-idle problems are often a result of having too much of the transition circuit exposed, but I've checked and re-checked that and it's not the problem.

I have found myself wondering if fuel is somehow getting fed in some unexpected and unmetered way, because of how little the idle screws (2 corner) are opened to get the highest possible vacuum (3/4 of a turn), but then also wondering if the idle air bleeds are contributing to the problem and leaning it out way too much in transition, though that would seem to require the idle screws to be further out than normal. It's all very confusing, and I suspect what I'm seeing has something to do with why the carb was on a shelf for decades and then sold at a swap meet for $10.

I do know that the plugs are somewhat fouled (if somewhat fouled is actually a thing), and should be cleaned to ensure ignition problems aren't part of the issue here, but something tells me there's more going on, and I wish I had more experience tuning Holley carbs so that I could at least guess better.

I do intend to put some pieces of wire in the idle air bleeds the next time I start it (hopefully this week), to see if that helps. We'll just see.

Honestly, though, if I'm going to keep running a carb it might not be a bad idea to go for a new Proform main body (which has other benefits), or find another craig's list or swap meet carb to interchange.

Then there are my fuel injection considerations; maybe I'm going to end up with fuel injection at some point anyway and it would be most economical to refrain from any more spending on carburetor parts. I do like it that an injection manifold would get the top of the engine below the 'hood line,' but it would also require me to move the alternator down to the AC spot, and it would cost a bit more from where I now stand.

So, for now, I'm going to see if there's a way to make this carb work without spending another penny. Next up is the wire test.

_________________
Aedifico ergo sum.

I think larger bleeds will make it leaner.

Which mixture screws does it have? Blunt or fine point? The blunt screws don't run more than 1-1.25 turns...?

How far are the secondaries set open from fully closed?
Partially open allows a smaller primary blade angle at idle and affects how transfers kick in.
Some may have holes drilled in the plate to allow the plate to be closed more at idle.

If the plug insulators are black they are fouled, I use a propane torch to clean dirty plugs. Best to replace if still misfires.
You should not be blackening plugs at this point.
Power valve leak or a plugged passage is the only way I can think it would be grossly rich at idle. (besides high float level)
Un-controlled choke plate? restrictive air filter? Un regulated fuel pressure?

_________________
Honey anyone?

I doubt they have been drilled. The idle bleeds are normally much larger than main bleeds. Since it will adjust to 3/4 turn, the transition slots must be close enough. I don't think the idle circuit is your problem.

I would make sure there is minimal gap at idle to the spring bolts to ensure the pumps can fill completely for a longer shot, check for the correct nozzles in the right place and check if they have been drilled.

If it immediately bogs, nozzles backward or too small, different cam position, Too much gap at spring bolt.
If it pulls well initially then stumbles, longer shot with the cam position and/or nozzles too big, no gap at spring bolt.

May want a higher number pv also since that engine probably has more vac at idle than the typical sbc with overlap. Might help if you’ve done all you can with the delayed stumble scenario above. 1.5 inch below low idle vac. The lower the number, the longer the delay after wot before the power system "switches" on.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

So today I proved myself to be a monumental idiot, and all that remains is to find out how much it will cost me in time and money.

It's was a beautiful February morning in Omaha (40 degrees!), and I decided to push the the car out to the drive way to experiment with the air bleeds, wanting to at least get closer to a diagnosis of the carb problem. My three-year-old even came out to help.





I took off the air cleaner to get a good picture of the primary side air bleeds: they look kind of big, right?



So, I bent a paper clip into a flat-bottomed U shape and put the ends in the primary air bleeds, which would enrich the mixture both at idle and also in the transition slot (which is where I thought the problem was).



Putting it in (where it was pretty secure with each leg sticking down pretty far into the air bleeds), I decided that one could never drive with it like that because of the possibility of it getting somehow dislodged and sucked down the carb.

SO... I started the car and it immediately ran much better. It didn't have anything like the same stumble off idle, and I could rev it somewhat cleanly even when it was cold. YES! Solved!

So I messed with it a bit; turned the idle needles in a bit more to as it was clearly now a bit rich at idle, and messed with the cam for the primary pump shot. Mostly I was trying to decide if the problem was really fixed, or if there were other issues.

I had it running decently, and decided to see how it ran if I quickly got the secondaries open. I had to do it quickly, as I didn't want to be bouncing it off the rev limiter and it revs up pretty quickly with no load. I noticed a spot where it almost wanted to die right as the secondaries started to open, so I was messing with that just a little when it unexpectedly backfired. It startled me, and baffled me for a moment because I couldn't figure out why. Then I noticed that it wasn't running well, and I even thought I heard it knocking a little as I shut the throttle blades.

Then it occurred to me that I'd probably blown out the power valve, which has no protection in this older carb. So, I shut off the engine and changed the power valve (I had an extra with a gasket, left over from when I rebuilt the carb), kept the 6.5, though I saw that I also have a 10.5.

I put the carb back together, filled the fuel bowl, and tried to start the car again. But it just really didn't want to start. Several squirts later I finally had it running, but not well. Then I saw it: the paper clip was gone.

I turned off the car and looked everywhere for the paperclip. It was not on the driveway, not on the engine, not jammed in the carb, not hanging off an ignition wire. So, I decided that there were two important possibilities: it was either blown off somewhere (garage roof?), or in the engine.

Deciding that it would be unlikely for it to have go in, I went inside and found another paper clip and put it where the first had been, and started the engine. It now started easily and ran fine, except that there was again some intermittent roughness and what sounded like occasional knocking. So I shut off the engine.

Now, I'm fairly certain that the paper clip did somehow end up inside the engine, and that it has either caused damage leading to the problems I was hearing, or it it is currently causing the problems just by being in there.

I could conceive of it bouncing in a cylinder getting hot and causing detonation, or hanging up on a valve occasionally keeping it from shutting, or countless other horrible things.

So, it seems I probably need to go into the engine now to find out. One thing I wonder though: why did the engine backfire? Is it possible that the paper clip some how found its way down to a valve as I was preoccupied and kept it from shutting, and that is what caused the backfire? To me, that seems unlikely because it was in there fairly well and it's not like things were really shaking or bucking around; it was all pretty smooth actually, but why else would it backfire?

So now you all know, my shame is public, and I can move on to finding a solution to this ridiculous problem.

Glad it's not my daily driver.

_________________
Aedifico ergo sum.

Seems pretty obvious to me what happened... Your 3 year old dropped it down the carb .. sucks, but that's just the kind of thing 3 year olds do; drop paperclips down carburetors... they're notoriously bad mechanics

So now that it's been firmly established that this is most definitely your kid's fault, it's up to you to of course deal with the aftermath.... ...kids

If it is in the motor(?), could you snake a camera into each cylinder to check through the plug hole? I've never tried this, but maybe someone here has some experience... at very least it will let you know which head to go after...

I feel for you... I can't begin to tell you how many things on my builds my daughters have gone out in the middle of the night and messed with.. it's the damdest thing..

--ccrunner

_________________
Dean

1972 Honda N600 Restomod "ccrunner's N600 VFR800 repower"

1963 Volvo P1800 Restomod
http://locostusa.com/forums/viewtopic.php?f=36&t=16309

1959 Berkeley SE492 Restomod...
viewtopic.php?f=36&t=19397

"ccrunner's 1960 MGA coupe Restomod" found on MGExp.com

I've seen that big of a difference in stock bleed size. Find out what they are supposed to be and you will know but whatever works.

Easy to retrofit a check valve for pv protection.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

Buy the cheap Harbor Freight borescope and look through the sparkplug holes, and down into each intake manifold runner. It likely made it part way past the valve then got smashed flat, hence the poor running. I'd avoid running it because eventually (if not already,) the intact bit downstream of the valve will break off and fall into the cylinder. At best it's intact and can be peeled off the intake valve seat, no harm done. At worst, it made it into the cylinder and has scored the walls...

It happens to us all. I made a crappy intake and a screw came lose and went in. That was not a good day.

_________________
Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
Both available from https://www.lulu.com/

Well, I decided that I just needed get in there and find the stupid paper clip. So that's what I did today.















First I took off the carb and intake hoping to see something without taking off a head, but nothing.

So I drained the coolant (which was the worst part of this whole job. I need to remember to have an easy way to drain the coolant from the back side of the thermostat when I design my final plumbing solution.), then took off the passenger side head. But, I guessed wrong, of course; it was in the rearmost cylinder on the driver side, all bent and blackened.

The whole thing only took a couple of hours, working almost entirely by myself. My 12-year-old did help for a few minutes, but he doesn't get things done very quickly.

I should have pulled the spark plugs before I did anything else, or, more importantly before I decided which head to pull; the strap on the plug from the paper-clip infested cylinder was dinged a bit and I think I would have started on that side if I had seen that. Oh well, it doesn't cost much more in time or money to do both sides.

I didn't break off any bolts, and so far the only damage is the plastic part of the coolant pressure sensor on the front of the driver side head. I'll have to see if I think I can glue it. If not, it's a $20 part.

Tomorrow I have to clean up stuff and order parts. We're supposed to have another day in the 50s, so it'll be a nice afternoon to work on that stuff. Lots of soot and such on the pistons and valves (cylinder walls look very good, still crosshatched, haven't noticed any scoring) and the plugs are definitely fouled, plus the graphite head gasket left a mess on block and heads. It'll probably be a good hour or two just cleaning that stuff. Then I need to see if I can make a decent thread chaser from the old head bolts. The ARP one is $50, and that's pretty steep.

I still need to look at the heads and see if they have the dreaded 'notch' that means I have to use graphite gaskets again, or if I can just do the newer MLS ones.

I meant to take a picture of the paper clip, but I forgot and tossed it in the trash, and don't feel like digging through garbage just for a posterity photo.

It was nice to find out that the heads do come off without too much trouble in the car. Various tubes are often in the way, but they're not that wide, so it's usually simple to get the wrench on one side or the other. There is one head bolt that has to ride in and out of the car with the head, it can't be installed or removed with the head in place. Not too bad.

_________________
Aedifico ergo sum.

Just for peace of mind I would force open the intake valve on this cylinder to check the condition of the valve face and valve seat.
Most likely nothing but it's nice to see for sure.

_________________
Perry

'If man built it, man can fix it'
"No one ever told me I couldn't do it."
"If you can't build it safe, don't build it."

Perry's Locost Super Che7enette Build
Perry's TBird Based 5.0L Super 7 L.S.O
Perry's S10 Super 7 The 3rd
Perry's 4th Build The Topolino 500 (Little Mouse) Altered
Perry's 5th Build the Super Slant 6 Super 7
Perry's Final Build the 1929 Mercedes Gazelle

Nice here again this weekend, so I started putting the engine back together.

New parts ordered from Summit:

2 head gaskets (Fel-Pro 9284pt). I went with composite, or graphite or whatever they call them. That's what was in there before, and it's my understanding that they're more forgiving than the MLS ones that I also could have used. I'm not planning on boost or anything, so they should work just fine.

2 sets of early LS head bolts (also from Fel-Pro)

A new water temp sender, Delco, because I broke off the plastic bit from the old one when removing the head bolt under it.

And a set of NGK TR5 spark plugs. The old ones are badly fouled, and the gaps look very big (no I haven't measured, somehow couldn't locate my tool).

Total cost for all the parts was about $120. Free shipping on orders over $100 from Summit. I looked also at Rock Auto, and they had better prices, but shipping almost made up the price difference and they're very slow to ship stuff. It would have taken a week to get the parts. From Summit it was 48 hours from hitting the buy button to parts at my door. They're always that fast, in my experience. Often the invoice will say 2-5 days shipping and I'll have the stuff the next day.

Things went back together fairly smoothly, and it only took a few hours even though I was taking my time.

It was my first time installing TTY head bolts, and I have to say it's kind of weird but I prefer it. I swear I could feel them give, or 'yield' as I did the first 90 degree crank.

I didn't have a torque angle gauge (if that's what it's called), so after torquing all of the bolts to the required 22 lbs ft, I sharpied vertical lines on the heads then turned each first sideways, in sequence, then another 90 degrees back to vertical. Maybe not as accurate as an actual gauge, but I was finding different angle numbers from different sources so I'm not sure what greater precision would have meant here. I know that GM often changes, or 'updates' such things.

One of the head gaskets has to be installed upside down to keep the 'front' marking at the front, thereby matching the coolant passages correctly, but that was pretty obvious.

I found conflicting info about re installing the rocker arms, mostly differing methods of making sure the lifters under the particular rockers are sitting on the cam's base circle when finding the correct torque number. But there's also the thread locker debate for these bolts; there is definitely some under the heads of the bolts from the factory, but none on the the threads. The manual apparently does not suggest that one use thread locker when reinstalling rockers, so I did not.

I compared the old spark plugs to the new



The difference in gap is clear, even in this poor picture (as is the fouling of the old one). I wish I knew why the plugs are fouled, and why the gaps are so big. I'll try to find my tool and measure this afternoon.

I also took some pictures of my pedal assembly. The brake and clutch are Afco, and the throttle is obviously mine. I matched the pivots, thinking it would be a more intuitive feel, but I really have no idea. I did use bronze bushings for the throttle pivot (over engineered, I'm sure), but don't yet have sorted how it will attach a cable. I'll need to have it in place to start working that out.





I'm hoping to get everything else back together this afternoon, as soon as I'm done babysitting. I don't know why I call it babysitting, since they're my own kids. Time-worn fathering terminology I inherited, doubtless.

_________________
Aedifico ergo sum.

Regarding the fouled plugs, you really need an air/fuel gauge. I get it that you can get close by how it runs, but how far off it is and in which direction may not be obvious. The plugs are fouled by it either running really rich, or it's burning oil, though I'd expect a lot of blue smoke if it were the latter.

_________________
Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
Both available from https://www.lulu.com/

I agree that I need a gauge, but I suspect there's a bigger problem with this carb. I'm 100% certain the engine burns little or no oil, which means it has been running very, very rich. That was not a surprise, mind you, when I pulled the plugs; I could already tell from listening and watching the exhaust.

It just isn't acting like a Holley should, and I can't figure out why.

I would absolutely expect it to meter fuel a bit rich with the factory jetting, Holleys usually do, but it shouldn't be crazy fat like this.

So, I could get a wide-band sensor (which I do plan on buying at some point, if I decided to stick with a carburetor), but I have a suspicion it won't tell me anything I don't already know about this carb, and that would blow my budget for getting a different carb.

I guess that's my sticking point: what to spend money on right now.

_________________
Aedifico ergo sum.

Fuel pressure 6 to 8 PSI?

Floats actually floating?

No dried-up gaskets between the metering blocks and main body?

Jets present in metering blocks?

Jet orifices consistent with markings on outside? (not reamed out)

Fuel only coming out of accelerator shooters when pump is worked?

Needle valves actually stopping fuel flow when closed? (invert bowl, blow on a hose connected to the fuel inlet to check)