Very scary and dangerous experience with Holley 2100 2bbl on 292 Y block !!!!

djfordmanjack · 2020-09-20 13:15

Guys, this is a heads up warning for those who still use an oem or similar 2100 Holley 2bbl carb on their Y blocks.
Today my throttle got stuck wide open twice before I actually knew what was going on. Luckily this happened upon cold start
and not on the road or in gear. I hope that I did not kill my old Y block as I have never hear that chunk of iron scream that badly...wow...scared to death.
Here is what happened. Please everybody check your accelerator pump 'pushrod' linkage screw and fast idle cam.

there is an adjustable hex screw with spring and shoulder nut below the throttle arm and accelerator pump lever. usually this works as a throw limiting system so when the pump reaches its full stop and the throttle gets opened a little more, the spring will make up for that.
On my carb the screw completely backed out of the shouldered nut, letting it slip to the side and the nut and spring got wedged between the pump lever and throttle arm, so that the throttle and arm got jammed on the plastic fast idle cam.

you would think that it is impossible to happen, but it did twice before I knew where it actually bound... even though I checked everything the first time. I did not see that loose hex screw because the whole assembly was still in place, but would wedge it self and throttle in wide open at random situation.

I did safety lock it with blue Loctite now and car still runs well again. I thought it must have thrown a rod immediately upon startup.

Everybody please check their fast idle cams and acc pump levers and linkage, NOW !

Be safe !

terry_208 · 2020-09-20 14:04

I'm glad everything, including people, is ok. Good find and notification!

lalessi1 · 2020-09-20 16:46

I looked at two Holley 4 bbl carbs I have and I think the bolt and nut on the spring on your carb are perhaps upside down? Notice the self locking nut required... this carb has never been apart with since new.

Ecode70D · 2020-09-20 19:35

Günter
That's very scary! Something like that can really ruin a person's day. Apparently you were able to get it under control quickly. In the old days when the Y blocks were plentiful, things like that happened especially when guys were hooking up multiple carburetors to them. Fast forward to 40 -50 years later with more miles on them, we can't afford to let those horrible things happen. How does the engine sound now?
Knowing you , I'm sure that you have it somehow rigged so that it is not going to happen again.
Lynn's new one does seem to be set up different.
Jay

djfordmanjack · 2020-09-21 02:36

Lynn, I believe the spring/screw is assembled correctly on my carb, since the slotted and relieved hex head of the screw would 'hook' or bind on the pump lever, and also couldn't be reached from below. I see what you mean on modern carbs and I know they are self locking nuts. Obviously they learned from exactly what happend to me and luckily improved on that.

Jay, my engine is ok, as far as I can see. I took it for a 20 miles drive yesterday and no strange noise or problems. That was horrible to listen to it scream and racing at those rpms, because I never do that. I absolutely dislike revving old driver quality engines.
The first time it happened it took me at least 5 seconds to shut off the engine because I was so stunned by what happened and was trying to figure out whats wrong, trying to pull the gas pedal back up or whatnot. I finally shut it off with the ignition switch which I should have done immediately anyways.

The throttle got stuck in a way where you could even hardly pull it back with hood open, air cleaner off, and time at hand. I had to wiggle the arm and screw a lot to get it off the fast idle cam. As I said this is a horrible situation and I would like to prevent this from happening to others, where engines or cars might get severly damaged or even harm could be done to passengers or observers.
Everybody take care please !

djfordmanjack · 2020-09-21 02:52

Lynn, I just checked back with the 57 shop manual, and the spring/screw/nut assembly is mounted correctly as it is supposed to be, screw on top, shouldered nut on the bottom. obviously they later changed the design for obvious reason !
Jay, I now used blue Loctite thread lock paste to keep this together.

Jeff Norwell · 2020-09-21 07:24

Wow.. that is scary G!
Glad you were not in full open traffic or on the hi-way!!!...

lalessi1 · 2020-09-21 07:48

After I posted that comment I looked at older carbs as well and your is correctly installed. It didn't look right to me at first hence my suggestion. You might be able to change the hardware to the newer configuration maybe that would be a better solution? The throttle sticking anytime is not good, thanks for the heads up!

djfordmanjack · 2020-09-21 12:55

great idea Lynn. If I change that I'd want a slightly crowned head on the hex bolt ( file while spinning in a drill) and would use a self locking nut AND another locking nut to be safe.

Ecode70D · 2020-09-21 20:19

Günter
I don't have any more of those carburetors in my collection that I can study. That's just as well though because I don't need one. I do remember them though.
Jay

SkylinerRon · 2020-10-04 22:04

Your arm is not riding on the cam correctly, needs to be bent a little. Carb has probably been apart a few times, that fuel line nipple is much later.

Ron.

djfordmanjack · 2020-10-05 14:39

That is correct Ron, thank you for your input. The carb is a replacement ( I found out about it, when I had the problem with the fuel bowl idle vent. which is needed on oem 57 application, but this carb was simply plugged and the engine stalled. after removing the little plug , it operated normally).
yes. You might want to know that I already did bend that arm since first posting this topic. It rides on the acc pump cam ( I previously stated it was the fast idle cam, which is incorrect!).
I found, that on random occasions the arm would nearly slip off ( or maybe it even did) the cam. it now rides full width and I have not had any trouble since. Thanx for your concern! It is good to have confirmation of those issues.

djfordmanjack · 2020-10-05 14:46

Jay, that's because your spare Holley 2bbl carb is now in my parts stash over here....hahaha

thx a lot!

Quote from: Ecode70D on 2020-09-21 20:19
I don't have any more of those carburetors in my collection that I can study.

SkylinerRon · 2020-10-05 20:39

I bet the epa doesn't like bowl vents, good that the car is in Europe....LOL

Ron.

Ecode70D · 2020-10-05 22:42

Quote from: djfordmanjack on 2020-10-05 14:46
Jay, that's because your spare Holley 2bbl carb is now in my parts stash over here....hahaha thx a lot!

AHA-----So that's where it is!

News:

Very scary and dangerous experience with Holley 2100 2bbl on 292 Y block !!!!