slight hesitation



I finished the adaptor and have everything bolted up. I have adapted an Autolite 1100 to a '78 head w/the 1.75" intake. It idles and runs great, and I can't tell a difference from the Holley 1946 I was running except in very hard acceleration. By that, I mean literally stomping it to the floor. Now, I realize that I won't be driving it that way (at least not much, anyway :LOL: ), but I want to know what's causing this. This hesitation is only for a split second, then the motor revs up as usual. Is this a normal thing for the 1100? I have been through 2 or 3 carbs. a few years back, and they did the same thing.

I adjusted the idle mixture, and it helped a little.

A mechanic told me that the hesitation was causing by the adaptation, and that the small carb. on the large intake would work good. But, I don't agree. It seems like that would make no difference since the 1100 was originally used on these engine w/the small intake. With the correct adaptor, it would be just like running it on an older head w/ 1.5" intake.

What do ya'll think could cause this?
Why put an autolite on a late model head? They're junk.

Put an RBS on and it will probably run alot better.
One of the reasons is because I want it to look stock. My mechanic screwed me over by putting the later head on. Sure, I know the benefits of the later head, but I really didn't want it. This engine wasn't and will not be built for increased performance.

Another added benefit (to me, at least) of putting the Autolite back on it is the reference material available in the shop manual. I was running a Holley 1946 from a Fairmont. I bought 2 manuals, and neither one had any specifics on how to tune it, what hooks where, etc. Nobody seems to know much about that carb, either. It's just not worth it. I want something that I am familiar with and can work on easily.

That's why.
Try advancing the timing a couple of degrees. If this helps, check for pinging, and adjust the vacuum modulator to reduce the advance. A little timing and a good set of plugs with the Pertronix unit eliminated my hesitation. ;)
That's sort of what I was thinking about the timing, but wasn't completely sure.

You mentioned adjusting the vacuum modulator to reduce the advance. What do you mean?

I already have the Pertronix unit. I plan to buy one of their Flame Thrower coils. I'll check the plugs. I know they haven't been changed in 3 years.
Falcon64":3ktyww4j said:
except in very hard acceleration. By that, I mean literally stomping it to the floor. Now, I realize that I won't be driving it that way (at least not much, anyway :LOL: ), but I want to know what's causing this. This hesitation is only for a split second, then the motor revs up as usual. Is this a normal thing for the 1100?

Well then, yes. I've used 3 or 4 Autolites before I upgraded my engine and they all had that problem. Evidently Pony Carbs rebuilt carbs don't have these sorts of problems as certain flaws are fixed.

Send the carb into them if you want the stock look and can pony up a little cash.

but you say you're not worried about performance though so don't worry about it.
The 1946 carb is normally set slightly rich in the lower midrange because of the EGR feed from the exhaust manifold. If run on a non-EGR setup, the lower-midrange (1200 RPM - 1600 RPM) will be slightly rich. At low altitudes, near sea level, etc., this can improve performance if timing is advanced about 4 degrees (10 deg. static). Make sure the vacuum advance line is connected to the throttle port vacuum and not manifiold vacuum.

If you're using the Autolite carb, try to locate one of the hot-water heating plates from the older sixes with the 1.5" bore. This will improve the venturi action in the carb as the charge leaves the bottom and enters the intake log. Right now, your small carb is entering a large vacuum plenum and the sudden volume change causes momentary icing with sudden throttle changes - even on 60-degree days. Don't hook up the hot water to the plate unless you want the extra MPG or live in a cold climate (it reduces performance, but improves driveability, like removing flat spots as you are now experiencing). If you do hook it up, run it thru the heater core so that turning on the heater warms the carb, too, and truning it off on warmer days doesn't.

Good luck! And, if you have a hot-water plate for a Fairmont with the 1.75" bore for the 1946 Holley, I sure could use one...!

Mark P.
that's just the way the stock carbs were. I had a stock 1bbl and that's EXACTLY what it did because I floored it just to feel the response and it bogged for a second or two and then picked up, but then I put on a Carter YF 1bbl. carb and I notice a BIG difference!!!! you should update your carb and I don't think you'll have any problems like that anymore! :D
Howdy falcon 64:

Personally, I prefer the 1100 too. Many of the complaints aimed at the 1100s are really attributable to the Load-a-Matic, vacuum advance only distributor and the Spark Control Valve in the carb.

Most likely your problem is related to the accelerator pump and the shot of raw gas needed for that quick acceleration. The problem is inherant to the Autolite 1100s because; 1. the pump volume is on the too small side to begin with, 2. the pump action is late, and 3. the pump plunger is the 1st thing to wear out after a rebuild (this is especially true on carbs with a standard trans). The only one of these variables that you have any control over is to rebuild the carb with a new accelerator pump plunger as needed.

The other variable is internal restriction channels that are not easily accessable.

You can mask the problem somewhat by increasing initial advance (already mentioned), and by richening the idle circuit by turning out the low speed air screw an extra turn or so.

Are you aware of the large carb bore Autolite 1101s used on the '63- '67 car and truck 223 I6s, and on '69 250s. They look the same for stock appearance, but have no tap for the Spark Control Valve. They do have a richer idle circuitry and jetting. They also are flow rated at 215 CFM as opposed to 185 CFM for the 1100.

You didn't say which distributor you're using. That could add to the hesitation too. If you're using a Load-a-Matic distributor and the vacuum is not hooked to an 1100 with a Spark Control Valve, you may not be getting all the advance Henry intended you to have.

Ideally, you should up grade to a '68 -72 point type distributor. You will gain centrifugal advance and still maintain stock appearances. Your Petronix should swap right over, too. You will need the 1101 already mentioned or a '68 or '69 1100, to eliminate the SCV and have a ported vacuum advance source fro this carb.

And I hope you compensated for the difference in chamber volume and head gasket thickness difference in swapping for the '78 head. If you didn't you lost a bunch of compression and that will add to the off idle hesitation too.

What are you doing to improve the exhaust on this sleeper?

Adios, David
Well, this was originally an old post (Nov. 25, 2002), and 66 pony brought it back up by posting a reply.

I have since solved the problem by swapping back to the 1946 with good results (finally got the choke adjusted right on it). I'll be upgrading to the '68-73 dual advance dist. with a Pertonix II and installing a metal head gasket whenever I see if my brakes will continue to work properly.

Exhaust will stay stock. I want it to have a quiet, "stock sound". Plus, I'll be adding a/c soon, and I don't want to have to modify any brackets and so on for that to work. (The money that I would've spent on a custom exhaust will now go towards the GV overdrive!!)
The 1101 that the 223 6 cylinder used did had a spark control valve as opposed to the model used on the '69 250s, which did not. I wish there was a way to combine the best of both carbs. into one: the '69 type (w/no s.c.v.) and manual choke (which was used on the 223).