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SEÑOR JERRY'S MUSEUM OF WONDER

Pre-production prototypes have their own museum page devoted exclusively to them. Click here to visit it. Otherwise, enjoy the museum entries below.

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NAIL / NAIL SPILL VALVE

This is an example of what I call the "Nail / Nail" spill valve design for a '63 - '65 FI unit. It has a much smaller throat area and seal face than a stock Nail / Thumbtack spill valve. I believe the Nail / Nail design was created by GM or Bill Thomas during the mid-sixties to work with the weak venturi vacuum signal from a dual air meter set-up. Spill valves like this were never installed by Rochester in any assembly line FI units. Dual air meter FI units were constructed for racing only. They provided a slight performance benefit in a very high engine rpm range. They probably hurt the engine's performance at low rpm.

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BRASS FAST IDLE CAM SCREW

I think GM used brass as the material for many of the fast idle cam mounting screws. However, almost all were cad plated before installation. This particular bare brass screw was found on an otherwise stock '62 7360 unit. I don't believe it was ever cad plated. To me it's way cuter than a baby squirrel.

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ALL GEAR PUMPS AREN'T THE SAME

Rochester machined several different vertical cavity configurations in the gear pump center sections. These different configurations may have been necessary to custom tailor the output pressure curve of each pump. This photo shows two different cavity configurations that were commonly used. Yes, it does matter how the upper and lower chambers are offset with respect to each other.

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PUMP WARRANTY SEALS

Rochester installed these soft leads seals in the hex head recesses of the lower pump screws. I assume the letters were the initials a Rochester inspector. I've seen several different combinations of letters, but the most common pair I've encountered is "JB". If you took your FI unit into a dealership for free repairs during the warranty and these lead seals were missing, you had some 'splaining to do.

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FAILING PILL VALVE

This anti-siphon pill valve has its little aluminum ball jammed into its vent hole. That means this pill valve can't work as designed. The little ball is supposed to fall to the bottom of the pill valve when the gear pump output pressure below it drops to zero. The open vent hole then allows air into the fuel passage to prevent gas from siphoning out the fuel bowl into the engine. If you keep on driving without replacing a pill valve in this condition, the little ball will eventually blow completely out of the vent hole. The engine will immediately die and won't restart. I know.

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ALL DRIVE CABLES AREN'T THE SAME

Rochester used three different length drive cables between '57 and '65. Each drive cable length had an outer housing with a corresponding length. It's easy to get them mixed up. The cable in the photo is the shortest design. It dates from the late fifties. However, this housing is made for the longest design length. The longest length cable was used from '63 through '65. If this particular combo was installed in an FI unit as an assembly, the cable end could break off or slip out of the pump shaft. Notice that the inside of this housing is wearing on the cable too. The cable / housing combination shown is, at best, a nice wall ornament.

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A TOUCH OF COLOR

The signal line nuts on '57 - '61 units were made of bare brass. So was the tee on top of the main diaphragm. Sometime during the '62 7360 series production run, Rochester started cad plating these nuts. I don't know why.

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BLACKENED STEEL BUTTERFLY

During the '62 7360 series production run, Rochester made some throttle butterfly plates out of blackened steel instead of using bare brass. I don't know why.

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WEIRD PUMP STAMP

I found this small "6" stamping on an early '58 gear pump. My guess is that this small character was briefly used just as Rochester switched from the '57 "001" pump housing casting number to the '58 - '65 "006" casting.

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MID VS. LATE VERTICAL BUTTERFLY SHAFT LEVERS

The cast steel lever on the right was used on most units from late 1957 through 1959. The stamped steel lever began appearing during the '59 model year and was used through the 1962 7360 series units.

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ORIGINAL COLOR OF DIE CASTINGS

These two photos show the original bright silver color of the zinc-rich alloy material used for most of the die-cast FI parts. This color has a slight rainbow sheen to it that is quite beautiful. Unfortunately, this surface color doesn't survive in the open atmosphere of the engine compartment for very long. After 40 - 50 years of exposure, there's usually not much of it left, even on the protected inside surfaces of the castings.

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OLD GASOLINE SLUDGE / RESIDUE

This tar-like goo is residue from gasoline that was allowed to sit in a fuel bowl for a decade. This stuff smelled nasty, and it had a surprisingly bitter taste as well.

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TWO-PIECE VACUUM FITTING

This is a '58 - '65 plenum fitting for attaching the hose to the distributor vacuum advance canister. Notice that the body of this fitting is made of brass and the hose nipple is made of steel. Usually both pieces were cad plated by Rochester. I've seen very few of these fittings on '64 - '65 7380 units with a bare brass main body like this one.

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BLACKENED LOCK WASHERS

Blackened lock washers have been found under air meter attaching nuts on some very original '63 7375 series FI units. Such washers were used on most '63 air meters according to a few experts in the FI community. I've only seen two sets of blackened lock washers on original air meters myself, so I just don't know how common they were on the Rochester assembly line during 1963.

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POWER BRAKE HOSE FITTING

This plenum fitting design was used to attach the hose for power brakes on some original 1963 and 1964 FI units I've inspected. This hose fitting was usually cad plated by Rochester, but this particular example was originally installed bare.

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AIR CLEANER ADAPTER GASKET MARKING

The original air cleaner adapter gaskets I've found on '57 - '62 FI units have all had a single ink stamp reading "CO". I imagine that is an identification mark for the company which made those gaskets.

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SHOULDERED NUTS

The original nut on the left is a typical '57 - '65 air meter attaching nut. The nut design on the right was used for all the plenum-to-baseplate (adapter manifold) nuts. The nut shoulders faced the part.

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WIDE RUBBER SEAL FOR TUBING

The seal in this photo is an original Rochester wide design that was used for the spider feed tubing connection at the fuel meter. I've never found an aftermarket source that could provide me with such wide o-rings for this small diameter tube.

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GEAR PUMP INSPECTION STAMP

The white paint stamp on this gear pump housing reads INSP. BY 016. I have seen this same stamping on one other gear pump. Both of these pumps came to me installed in 1963 7017375 series units. These units probably came off the assembly line with wobble pumps rather than gear pumps. My current guess is that Rochester stamped new service gear pumps in this way for a brief period back in the mid-sixties. I don't know why they would stamp service pumps and not assembly line pumps though.

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RESTAMPED AIR METER

Rochester Products didn't let anything go to waste.  If a part was initially stamped in error or was being recycled in a different FI series, they just whacked a new i.d. number on top of the old one.  Here we have a "251" air meter that was actually used in a 7017200 FI unit application.  As you can see, the casting flange was overstamped "201" to reflect the new application

 

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WHAT'S A 7010380 FI UNIT?

It's a just a data plate stamping mistake. Data plate stamping errors are rare, but they did happen. Like I said, Rochester didn't throw anything away that was serviceable.

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HOMEMADE NOZZLE BLOCK SOCKET?

I never sausage an ugly thing. Well, maybe this one time. Creating a nozzle socket like this one was a colossal waste of time. As soon as you tightened down the nozzle retaining plate, the brass would separate at the various cuts creating a vacuum leak.

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DISTRIBUTOR CASTING FLAW / OIL LEAK

The body casting of this distributor is flawed around the perimeter of the data plate mount. For some reason, one portion of the data plate seat is too low for the gasket to seal. This casting was the proverbial oil gusher until that low spot was filled with silicone sealer.

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COPPER-PLATED SPILL VALVE SPLASH SHIELD

Most splash shields were cad or zinc plated. This beauty somehow came through Rochester dressed in copper. It's the only one I've ever seen.

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AIR METER I.D. STAMPING ON TOP

Each 4900 series air meter usually had the "901" i.d. number stamped into the flange surface facing the firewall. I think the Rochester worker got confused when stamping this 901 application though. It ended up on the top flange surface. "What the heck, it's still a good part; send it on down the line."

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HOURGLASS DEFORMATION OF SPIDER FEED TUBING

This is what happens to the end of nozzle feed tubing when you use multiple o-rings instead of just one. It might not happen with two o-rings, but it will definitely happen with three. This slight narrowing of the fuel passage does make a difference. It causes abby-normal backpressure to the fuel flow at that point. In a '63 - '65 unit, this can cause too much flow to be redirected to the spider that should have gone to the spill valve. That causes an uncorrectably rich idle mixture if the hourglass deformation is at the spill valve cover end of the feed loop.

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'63 - '65 IDLE AIR TUBING LENGTH VS. '58 - '62 TUBING

This photo illustrates the difference in length between these designs. That's a '63 - '65 driver's side tube on the left. The 1/4" longer tube on the right is for a '58 - '62 unit.

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DRIVE CABLE WRAPPED THE WRONG WAY

The distributor end of this NOS pump drive cable came unraveled shortly after being put in use. Notice that the outer wire layer is wrapped in the wrong direction. This allowed the torque applied by the distributor cross-shaft to "unwind" the wire rather than wrap it tighter.

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UNDERSIZED REPRODUCTION NEEDLE VALVE

There is a big difference between genuine FI needle valves and the commonly available reproductions. The original GM needles have blunt metal tips. The reproduction needles have soft, pointed tips. The seat openings in the original valves are much larger, too. This does make a difference in flow, but don't worry about running low on fuel in your bowl unless you buzz your engine to 6,500 rpm through three gears in a row. Don't ask how I know this.

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UPSIDE-DOWN NOZZLE STAMPINGS

Such stampings are not very rare. They're much more common than over-stamps.

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OEM GASKET MANUFACTURER'S STAMP

It's unusual these days to encounter any original GM paper gasket still in use after 40 years. This '63 - '65 base gasket was either installed on the engine assembly line in Flint or sold over-the-counter during the sixties. By the mid-seventies, the service paper gaskets did not bear the manufacturer's "CO" ink stamp.

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WORLD'S UGLIEST IDLE AIR TUBING

I know some folks like to save a little money by making parts at home, but give me a dadgum break! This hideous example of a Do-It-Ur-Selfer's work was found beneath a '57 4520 unit. Yowzah! It may have saved the owner a few dollars, but it sure cost him his dignity!

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OVERSTAMPED NOZZLES

Once again we see that Rochester didn't throw anything away. Not even something as cheap as a brass nozzle body that had been stamped incorrectly. Here we see a series of overstamped upper nozzle bodies. Not very pretty, but they are still quite functional.

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COLORFUL GEAR PUMP CASTINGS

I've seen at least three different colors of '57 - '65 gear pump body castings. I think they were all created by a chemical coloring process. The example below shows the bronze or brown color that is commonly seen on many late '64, '65, and service gear pumps. It differs slightly from the burgundy or purple-black color seen on some early '57 pumps. Just about all of the '58 - early '64 pumps were black.

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COPPER-PLATED DISTRIBUTOR OIL FEED TUBING

I don't know when this plating practice began or when it stopped. However, most of the original copper-plated oil feed tubing examples I've seen have been with '63 FI distributors.

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MANUFACTURER'S MARK ON IDLE AIR RUBBER ELBOW

I'm not sure if this is a GM part. It may be an aftermarket substitute, but it's the only idle air rubber elbow I've seen with a marking of any kind.

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ORIGINAL ROCHESTER PARTS BAG

During the fifties, Rochester furnished their FI parts to GM counters with their own orange and black labels. That practice ended by the mid-sixties. By then every FI service part came in a package with a GM or Delco Carburetor label.

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ROCHESTER INSPECTION INK STAMPINGS

Rochester had a serious problem with porosity in their sand-cast parts. So, for those castings expected to be liquid or vacuum tight, they inspected each one after machining to make certain there were no exposed porosity problems. After passing inspection, these parts received one (or more) ink stampings to show that they were acceptable for assembly line use. The letter "C" was often used. The photo below shows the only "IMP" stamping I've encountered to date. I don't know what those letters might mean.

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COLORFUL SERVICE PARTS

Many die-cast FI parts sold over-the-counter during the seventies had a yellow dichromate wash applied. While very pretty or at least interesting when new, this color quickly turns brown after exposure to engine compartment fumes and heat. This yellow wash was not used on assembly line FI parts. I usually have it removed before installing such service parts. However, I have made exceptions for customers who were pimps or French. If they were both, I just chrome plated all their parts.

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DATED MAIN DIAPHRAGM

Most GM main diaphragms are ink-stamped with their production date. Only a few of the GM diaphragms I've seen were ink-stamped like this one with the part number as well.

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PROTOTYPE '62 DIFFUSER CONE

This Frankenstein diffuser cone was constructed by Rochester to test the '62 venturi/choke design. I don't know how it slipped out their door and ended up on a '61 7320 unit, but I doubt it involved the St. Louis Corvette assembly line.

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ORIGINAL PLENUM COLOR?

A while back I had the pleasure of repairing a 4360 FI "school unit". It had never been run on an engine or even bolted down on an adapter manifold. The photo below compares the aluminum color I found below its plenum data plate with that of a sand-cast main diaphragm cover recently refinished by Fred Hudson.

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AN AIR METER "OF COLOR"

This entry was submitted by a Californy FI repairman, Jim Lockwood.

"Here are the only three pictures I have of the NOS 4360 air meter I mentioned (which I think might have been yours at one time, Jerry). From the pictures and from memory, the dichromate parts are the fast idle cam and screw, throttle shaft end plate, cold enrichment "6" thingy and the lever underneath it, and the idle air screw spring. The aluminum casting is dark, but from your discovery on the school unit, this must be an aging phenomenon."

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CLINICALLY DEAD '62 FUEL BOWL

This photo was submitted by Nathan Vorderstrasse. Please understand that he's not responsible for the "repair" work shown. I especially like the corner screw hole made entirely of epoxy. Damn, there are some cheap Corvette owners out there!

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NOW THAT'S A GEAR PUMP!

This monster probably put out 50% more volume than a stock production AC gear pump at every speed. Since some of the parts appear to be from the pre-'57 FI development period, maybe it was created as a prototype for an injected Cadillac engine. Perhaps it's sized for a Methanol powered engine. Or, just possibly, it's an engineering drawing error that actually got produced before it was caught.

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FI DISTRIBUTOR PAINT MASKING

This is a side view of an original FI distributor upper housing. You can see that Delco masking kept the black exterior paint off all parts beneath the cap.

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BRASS COLD ENRICHMENT PISTON

I can't imagine how this part came to be... unless it's some kind of elaborate joke played on me by another FI repairman. I'm talking about the brass sliding "piston" in this 4520 cold enrichment housing. For one thing, the flange has too small a diameter to contact the lever beneath the bi-metallic coil cup. However, that may be the reason the part was made in the first place. It would have prevented the unnecessary pull-off function normally provided by that piston.

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ODD BEVELING IN GEAR PUMPS

I initially thought all gear pump center sections were the same. Rather, I thought they should be the same. They were not. I found these weird bevels cut in gear pumps that worked just fine on the dyno. But how can different shaped chambers all perform the same? Maybe they don't, and I just can't tell the difference yet!

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HIDDEN INTERNAL MARKINGS

I found these original markings inside a '57 spill valve cover. The "C" inspection stamp meant the aluminum casting had passed a porosity check. The colorful ink marks on the black o-ring were probably a code to indicate size.

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EARLY VS. LATE '57 SPILL VALVE PISTONS

Early '57 4360 FI spill valves used pistons like the one on the left. The later design on the right was quickly adopted during 4360 production and was also used throughout the 4520 and 4800 FI production runs. I don't know why this change was made.

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MAJOR FLAW IN '57 FUEL BOWL CASTING

Talmadge Ward of Auburndale, Florida sent me this gem. The photos show before and after views of a '57 sand-cast fuel bowl repair. Somehow this bowl made it all the way through production and left the Chevrolet assembly line on an injected passenger car. Notice that there's no way for gasoline in the axle link area to drain down into the pump chamber. This affected fuel meter operation in a big way for 43 years until Talmadge discovered the flaw. After he created the opening that should have been cast in the bowl initially, the FI unit ran fine for the first time in its long life!

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