57/early 58 vs late 58 to 65 FI drive cable length

[Mike M.]

anyone care to speculate as to why chevy/rochester lengthened the distributor to high pressure pump in mid 58? the 57-early 58 FI cable housing is about 5 3/4" in O.L. while the mid 58 thru 65 drive cable housing measures about 6 1/8" O.L. i've used the short housing in midyear FI's and the long housing in our 57's. for all intents and purposes they are interchangeable. but why did GM lengthen the later housings? i might add the the internal cable themselves are also of the short and long varieties. mike

[Don H.]

Re: 57/early 58 vs late 58 to 65 FI drive cable length

Mike, Great question! I have also used both lengths in both styles with no problems. Possibly it is related to the length of the cable housing?? Hopefully someone has an answer, sorry I do not. Don H.

[David G.]

Re: 57/early 58 vs late 58 to 65 FI drive cable length

Mike I just measured the cable that I removed from an early 57.
It measured 5 7/8" and was a very snug fit.
Dave

[G B.]

Re: 57/early 58 vs late 58 to 65 FI drive cable length

The '57 - '62 FI units originally used the short cable and housing design. The '63 - '65 units used the long cable and housing set-up.

The length change was made because the distributor base orientation was rotated slightly clockwise in the 810 adapter manifold. That placed the distributor threaded coupler a little further away from the end of the pump housing. I believe this was done to make it easier to install and remove the cable housing with a wobble pump in place. After the wobble pump was replaced with the previous gear pump design, Rochester never returned the distributor base orientation to its older position.

[Richard M.]

Re: 57/early 58 vs late 58 to 65 FI drive cable length

I often wondered why being a rookie at the FI stuff.

Could it have something to do with differences in the distributor drive mechanisms or variations in the Fuel Meter & Fuel Pump distances?

Are all distributor mechanical specs and distances from vertical shaft center to drive snouts identical?

Are all Fuel Meters and fuel pumps on all FI Units in the identical position with respect to the distributors?

I guess it would take some effort to figure all of this out.

Rich

(oops, I was typing when Gerry replied)

[Mike M.]

Re: 57/early 58 vs late 58 to 65 FI drive cable length

thanks gerry. u da man. mike

[Mike M.]

Re: 57/early 58 vs late 58 to 65 FI drive cable length

gerry: never having had a early 63 with wobble pump, is the woogle pump a little longer than the regular, run of the mill, high pressure pump? mike

[Jim L.]

Re: 57/early 58 vs late 58 to 65 FI drive cable length

Are all Fuel Meters and fuel pumps on all FI Units in the identical position with respect to the distributors?

Rich,

C2 fuel meters are mounted such that their rear angles outboard slightly relative to the plenum. C1 fuel meters are mounted parallel to the plenum.

Although there are differences in the fuel meter castings between C1 and C2 FI units, the pumps are all in the same location.

Jim

[G B.]

Re: 57/early 58 vs late 58 to 65 FI drive cable length

Yes. Both the open end of the pump snout and the cable end of the pump shaft are about 1/8" further from the pump/bowl gasket surface. Also, about 50% of the wobble pump main body sits outside the fuel bowl. This makes it impossible to remove a wobble pump with the right rear nozzle block in place.

The only advantage offered by the wobble pump design is theoretically faster starts over a gear pump. Even with tight tolerances, a gear pump has some "slip" or pressure loss around the gears. At engine cranking speed, ~200 rpm, this could be significant but actually isn't. The piston/check valve design of a wobble pump makes pressure regardless of how slow it spins.

[John D.]

Re: 57/early 58 vs late 58 to 65 FI drive cable length

Read some very good replies here to Doc's question. Especially Jerry's.
You didn't ask but here's something to boggle your mind on drive cables. I am going to give you info on the Pontiac fuel injection and also the Corvette/Chevy.
RP made four drive cables.
#1585264 Overall length 4-15/16" 57-58 Pontiac FI. Just restored ones of those critters and was amazed how short the cable& housing were.
#1585719 Overall length 6-21/64" 57 to 62 Corvette
#6409370 Overall length 6-15/32" Early '63 wobble pump ( have never seen a NOS one of these cables)
#6409698 Overall length 6-27/32" 63 to 65.

If you want to make it easy on yourself remove the info on the Pontiac and the Wobble pump.
Dangers of using a wobble pump folks.
Wobble pump has 5 ceramic type discs(pills). Chevy lost a lot of engines with those pumps as the discs broke. The pieces got into the spider and anti-siphon valve and then the engine went next due to hydraulic lockup. Frank Sciabica told me the above long ago and sent me a service bulletin.
63 shop manual Pg 6M-50 Wobble pump. See Fig 113. Notice the disc right below the piston. That's the part that can break. It looks like an curved aspirin. John D.

More info:
57-62 Cable assy with casing #1585804
63 -65 Cable assy with casing 6409648

Credit for most of the above info goes to Michael Hanson. He posted this info in a better fashion than I did on July 31st, 2008

I use the long drive cable and housings on all Mid '58 to '65.
If you have a short housing one does not need to use the short cable. The long cable works perfect. Especially the one like FI Art has where the stop of the cable has been moved to provide more catch in the distributor.

[Richard M.]

Re: 57/early 58 vs late 58 to 65 FI drive cable length

Jim, Gerry, John. Thanks for the very informative details.

I've never seen the internals of the wobble design pump, I've only rebuilt the gear type. What does the wobble type look like inside? I'm away from my manuals....far away.

Rich