Making a Dummy Thermostatic Actuator - Alfa Romeo Bulletin Board & Forums
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post #1 of 103 (permalink) Old 08-02-2004, 12:57 AM Thread Starter
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Making a Dummy Thermostatic Actuator

If you have a SPICA car and want to tune it youself, a dummy T/A is an important tool. According to Alfa tech, the ONLY way to correctly set the pump gap is with a dummy T/A set to the correct length for your "T" model pump. I know some people use the actual TA to set the pump gap, but that is incorrect and difficult. Even if the T/A is extending the spec amount, pushing it in and taking it out to adjust the internal screw puts wear on the relatively fragile pipe.

In addition, if you're T/A leaks and no longer extends to the required length, your dummy T/A can be installed until you can get a serviceable replacement. Of course, you'd need to leave the top part of the T/A in the intake manifold coolant passage (or make a simple blanking plate).

If using a T/A as a temporary replacement, the engine may be slightly harder to start when cold (due to the lack of enrichment), but hot starting won't be affected (where enrichment isn't needed). If really in a bind and it's cold, you can always unclip the front of the SPICA air box and spray some ether Starting Fluid to get an initial start, then warm the engine before driving off.

At any rate, making a dummy T/A out of stock hardware is very easy.

Take a 1/4" x 3" long bolt (carriage bolts are nice 'cause they have a smooth top), two nuts, and a 3/4" OD washer. Assemble as shown and you have a dummy T/A. In setting the length, measure from the bottom of the washer to the tip of the bolt. Set at 27mm for pumps T237/1 thru T261 (1969-1976 [CA]) and 29mm for pumps T260/1 thru T265 (1976 [49 state] - 1981).

If you're willing to do a little more grinding or filing, then you can make it "slip-in" as described in the photos below. This mod will keep you from having to remove the screws each time to access the adjustment screw.

Of course, you can just push down fully on the dummy TA and not use the screws, then take a pump gap measurement and repeat as necessary. However, I'd recommend that you use the screws on the final check just to make sure the dummy is seated completely.

Here's a few pix. The last picture is of a factory tool. Note the hollow center to allow a screwdriver to be inserted and the pump gap adjusted without having to remove the TA. A makeshift dummy TA will have to be withdrawn each time to adjust the internal screw. However, with the rounded top of a carriage bolt, you can just press it down and hold it while taking a pump gap measurement.
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John Stewart
74 Spider
91 164S

Last edited by Roadtrip; 08-03-2004 at 09:08 AM.
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post #2 of 103 (permalink) Old 08-02-2004, 05:34 AM
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Killed my T/A

Roadtrip, you are scary. I just came in from the gargage where I was trying to adjust my spanking new Ingram rebuilt FI pump. I was trying to get the proper .019 clearance on the back side, r&r-ing my TA when I noticed a red fluid. Probably torqued something, lost the stuff inside the TA, as the probe no longer extends. So now I'll order a new one in the morning, meanwhile, I'll build one like yours. Thanks. PS: Anybody working on your TA, everything they say about them is true, very fragile. BE VERY CAREFUL WORKING WITH YOURS!
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post #3 of 103 (permalink) Old 08-02-2004, 09:48 AM Thread Starter
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PMM -
Given enough flexing or an inadvertent kink, they will fatigue and break. I'm curious . . . did you have the center support fastened while you were R&R'ing the lower part of the actuator? The center support should be the last thing secured when installing a TA.

Also, the center support should ALWAYS be used in a permanent installation. If not, there will be considerable flexing in the tube. The injection pump and T/A are subjected to severe high frequency vibration. Every fastener in the injection system is important . . . fuel pipe tie-downs, pump mounting bolts, etc. Make sure they're ALL there and nice and snug.

BTW, be careful when removing the top part of the TA. Those studs holding it in the water jacket are pretty small and subject to corrosion. Soak 'em in PB Blaster before you attempt to remove the nuts.

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post #4 of 103 (permalink) Old 08-02-2004, 11:20 AM
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John,
Did you ever consider using a hollow tube instead of a bolt for the dummy TA? I've been meaning to try this for a while now but it's not high on my list of priorities at the moment. A local hardware store carries small tubing in brass, aluminum, and stainless. I don't know if it's heavy enough to be able to be threaded, but I mean to find out one of these days. Or maybe the threaded tubing that's used in household lamps comes in a smaller size? It would be so nice to be able to stick a screwdriver down there.

[FONT="Century Gothic"][B]Bob Farace[/B]
[COLOR="DarkGreen"]1971 Alfa Romeo 1750 Spider Veloce[/COLOR]
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post #5 of 103 (permalink) Old 08-02-2004, 11:32 AM Thread Starter
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Yea, Bob, I tried it with some of the threaded tubing that table lamps have, but it was too big and my wife got the beak at me taking apart the lamps for Alfa parts. The diameter has to be just right to touch just the screw head and not the shelf around it. Given that this is such an infrequent adjustment, it only takes a few more seconds to do it with the 75 cent ACE Hardware special.

BTW, nice picture that Papajam posted. Wish I could have been there. Did you take in the tech session with Wes Ingram? If you did, how about posting a synopsis of the session for everyone?

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post #6 of 103 (permalink) Old 08-02-2004, 12:00 PM
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Quote:
Originally Posted by Roadtrip
BTW, nice picture that Papajam posted. Wish I could have been there. Did you take in the tech session with Wes Ingram? If you did, how about posting a synopsis of the session for everyone?
I would like to have gone to the tech session but wasn't able to because I entered the road rally and they coincided. I nearly bailed on the rally and ran back to the hotel for the tech session because I was without a navigator (I had one lined up, but my mixup caused us not to hook up before rally time), but I figured I had paid my entry fee and had nothing to lose by trying to run the rally solo (and with no watch and a speedometer that I'm only guessing is reading about ten percent fast). As it turns out, I only missed one turn, quickly discovered my error, and came in 15th out of 75, being 5:59 off the pace (which I attribute partly to pure dumb luck, but I'm still kind of proud of that result). It was a lot of fun.

Hopefully someone else that made it to the tech session can post the synopsis.

[FONT="Century Gothic"][B]Bob Farace[/B]
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post #7 of 103 (permalink) Old 08-17-2004, 06:11 AM
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The TA on my 1972 w/ T155 pump extends to 29mm at 175F. The nominal spec is 27mm.
It retracts to 25.8mm cold.
My question is: Should I make my dummy actuator 29mm? or 27mm?
Is there any need to do anything crazy like shim the TA out 2mm?
I'm going w/ a 29mm dummy actuator for now.
Steve

Last edited by santoli3; 08-17-2004 at 06:14 AM.
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post #8 of 103 (permalink) Old 08-17-2004, 07:25 AM Thread Starter
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All the replacement actuators are 29 or 31 mm extensions now. That's ok, just put a 2mm shim (a nice washer with 2 filed edges to clear the screw holes work fine). You're cold start performance may suffer a little because it won't be enriched quite as much as with the old 27mm TA, but not to the point you'll probably notice much.

When setting the pump gap, ALWAYS use the extension spec for the pump you have, NOT the T/A. So, in your case use 27mm when setting the pump gap. Setting the pump gap has really little to do with the TA. The purpose is to center the 3D cam to the "zero" position. As long as the TA extends to 27mm by 175F, the pump doesn't care. If it extends a little earlier than 175F, the engine will just run a wee bit lean for a short while until it's up to temp. The big problem is if it doesn't extend to 27mm. Then the pump pushes a constantly rich mixture . . . . not good.

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post #9 of 103 (permalink) Old 08-17-2004, 08:15 AM
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O.K. back to 27 it is!
Thanks;
Steve
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post #10 of 103 (permalink) Old 08-17-2004, 09:41 AM
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O.K. As I'm doing this, I'm trying to understand what the diference is between setting it using a 29mm dummy actuator, or setting it with a 27mm DA and shimming the TA out 2mm.
Is there something that the bottom of the screw engages?
Are there any good drawings of the pump internals available?
I'd love to know what's going on inside the thing. As a mechanical engineer I hate black boxes.
Steve
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post #11 of 103 (permalink) Old 08-17-2004, 11:20 AM
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Quote:
Originally Posted by Roadtrip
When setting the pump gap, ALWAYS use the extension spec for the pump you have, NOT the T/A.
So by the same token, I assume this also means that if I have a 1974 Spica pump in my 1971 Spider, I should set the gap using 1974 rather than 1971 specs (which are probably the same anyway (I'm not at home to check))?

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post #12 of 103 (permalink) Old 08-17-2004, 01:18 PM
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Quote:
Originally Posted by Farace
So by the same token, I assume this also means that if I have a 1974 Spica pump in my 1971 Spider, I should set the gap using 1974 rather than 1971 specs (which are probably the same anyway (I'm not at home to check))?
I think John covered that above. It goes by pump series number.
I just wish there were good schematics of the SPICA pump. I can follow instructions, no problem. If John says do it this way, I'll do it this way. If Wes says do it that way, I'll do it that way. But I woulld so like to understand why. When I adjust a needle valve on a carb, I now exactly what I'm doing and why. No faith required. Same thing when I work on my Audi (Bosch CIS). But where can I get that level of knowledge about SPICA
While I'm on the subject, where can I get a spanner for the mixture adjustment?
Steve
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post #13 of 103 (permalink) Old 08-17-2004, 01:43 PM
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Steve, do you have Wes Ingram's manual? That shows some of the internals. The official Alfa manual (available through the AROC tech library to members) is good for the linkages. John's been posting some great cut-aways of a pump he sacrificed for the effort, although I suspect many of those images got lost in the Great Server Debacle. Pat Braden's books offer some more of the internals.

The tool for the FCS locknut shows up occasionally on eBay for more than I can afford to pay for it without my wife killing me. I use a large screwdriver and a hammer. I'd like the proper tool eventually; I suspect it can be made in a similar manner to how some have made a differential ring nut socket, by grinding away parts of a regular socket to leave the tangs to fit the slots (it would have to be rather deep for the FCS, though; maybe heavy pipe would be strong enough?).

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post #14 of 103 (permalink) Old 08-17-2004, 04:11 PM
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I do have Wes' and Pat's books. Both invaluable. But neither gives a complete diagram or explanation of the internal workings of the pump. Admittedly this is purely an academic pursuit as the available info is completely adequate for system maintenance.
I donít have the AROC book. Do you mean this one? http://www.aroc-usa.org/cgi-local/So...305+1102620522 ?
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post #15 of 103 (permalink) Old 08-17-2004, 08:43 PM
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No, I don't have that one yet, but I'd bet it's worth having. AROC offers to members photocopies (well-done photocopies, I might add) of the official Alfa Spica manuals for specific model years. Since at the time the manuals were written Alfa was still being hush about the internal workings of the pump, there's really no info in that regard, but it's good for an overall idea of what the system is doing and for how the linkages are adjusted (especially if you have the official tools!). I forgot about that other AROC manual; I'll have to get a copy.

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