I've had this hesitation for years. Here's the stats: '66 283, new Holley 4160 (600 or 650 cfm), new Summit $99 HEI ignition. The Holley now has .035 squirters, the rest is stock. A previous thread about this asked for the following information:
WITH VAC ADVANCE UNHOOKED/PLUGGED Base timing = 6 deg, Total Timing @ 3k rpm = 25 deg, Total Timing @ 4k = 25 deg, Idle rpm = 880 (I cannot reduce further w/curb idle screw), Vacuum @ idle = 20".
WITH VAC ADVANCE CONNECTED: Base timing = 6 deg, Total timing @ 3k = 52 deg, idle = 880rpm, vacuum = 20"
WITH VAC ADV CONNECTED AND ADJUST AIR MIXTURE SCREWS Base timing = 4 deg, Idle rpm = 760, vacuum = 18" THEN raised curb idle to 880 rpm, base timing = 8 deg and total timing @ 3k = 50deg.

Does this info help in determining my problem? Thanks in advance.

Tom:
You say that you've had the hesitation for years, and that the carb is new. Is the hesitation exactly the same before and after the carb swap? Is the carb *brand* new, or new to you? What made you change the squirters while leaving the rest of the carb calibration alone?
Also, where in the process was the dist. changed and was the hesitation the same before and after?
Sorry if it sounds like I'm just asking a lot of questions, but you've changed a lot of variables, and it's helpful to know how the car reacted to each and the sequence of decision-making.
Tom

I've had this hesitation for years. Here's the stats: '66 283, new Holley 4160 (600 or 650 cfm), new Summit $99 HEI ignition. The Holley now has .035 squirters, the rest is stock. A previous thread about this asked for the following information:
WITH VAC ADVANCE UNHOOKED/PLUGGED Base timing = 6 deg, Total Timing @ 3k rpm = 25 deg, Total Timing @ 4k = 25 deg, Idle rpm = 880 (I cannot reduce further w/curb idle screw), Vacuum @ idle = 20".
WITH VAC ADVANCE CONNECTED: Base timing = 6 deg, Total timing @ 3k = 52 deg, idle = 880rpm, vacuum = 20"
WITH VAC ADV CONNECTED AND ADJUST AIR MIXTURE SCREWS Base timing = 4 deg, Idle rpm = 760, vacuum = 18" THEN raised curb idle to 880 rpm, base timing = 8 deg and total timing @ 3k = 50deg.

Does this info help in determining my problem? Thanks in advance.


http://www.camaros.net/forums/showthread.php?p=1004627&highlight=101#post1004627

Read the link to a post by John Hinckley 2 or 3 times, then go give that thing some advance. I have a 66 283,,,,it digs 40°. It likes a 450 Holley or a 650, it hates the 600 I bought for it. Mine is a spoiled brat though:).

What heads does yours have ,,,, the old small chamber Power Pack heads? The 283 gets it's CR hurt BAD by increases in chamber cc, and that will make a boggy engine in a hurry. Not very many small chambered aftermarket heads available either, the TFS 3030300003 is about the best, and the 305 heads with small chambers is a good oem choice.

I have that Summit distributor on one of my engines, it's a good unit.

Your accelerator pump should squirt any time you move the accelerator. If it doesn't you need to adjust it so it does. That's the upside down bolt with the spring and nylock nut deal. ...... Give it some advance, give it some fuel, it will go. If it doesn't have the CR compromised.

Don't sweat the .015 acc pump clearance some claim to be all important, it is BS. As long as at WOT you can still manually push the diaphragm upwards, you are OK. Main thing is, touch it and it squirts instantly:thumbsup:.

Tom,
the hesitation has always been the same. I got a brand new carb direct from Holley. I changed the squirters to a larger size after researching on this great site, they didn't cost a lot and they were bigger!!!! (doesn't big = fast)? I then changed from original points dist to the HEI. Still had the hesitation.
After these new parts were installed about a year ago, I experimented by changing the timing and then revving the motor. I was able to get better throttle responce but did not check where my timing was. The car then ran rich and I tried to fix by adjusting the carb. I opened the xfr slot in secondaries and adjusted the 2 mixture screws. At one point it was backfiring. I could not get rid of rich condition. I can't dedicate a block of time to fix/diagnose, only an hour or 2 per week so I decided I'd rather get rid of rich condition and do more research on the hesitation. This is where I'm now at. whew...

As Tim mentioned, you need to first get the timing set as good as possible, and then turn your attention to the carb. If your time is limited, get out your timing light, goose it up 2 degrees at a time, and take it around the block. Rule of thumb is advance it until you hear it knock under acceleration/load, then back off slightly (1 or 2 deg) and you have found the max advance your setup tolerates. You can now make your carb adjustments with more confidence.
Bigger does not always equal faster and here's an example...I just bought a Holley for mine this winter. I haven't even gotten it on the motor yet. I have a 355 with 10:1 comp, etc. and decided against a 750 cfm after a lot of great feedback from folks here on Team Chevelle. A few people here said it would we too much carb for the motor and my "seat of the pants" meter would feel stronger, snappier throttle response from a smaller unit, so I went with a Street Avenger 670. I bought the necessary tuning parts (vacuum springs, jets), but didn't buy a larger squirter as I was told this is the last thing I would need to change (if I needed to at all) in tuning my setup. If you have the stock squirters I'd recommend changing them back. You would then be able to take a fresh look at things with your timing adjusted better and a "stock" carb calibration. Then take it for a ride and let us know what you've got! :thumbsup:

Advance the timing...what cam is in there? Might as well list all the engine info
How do you set your idle mixture? I've found this to be THE LARGEST contributor to sloppy take-off and street manners. I see you have a vacuum gauge, good for you!!!

.035 squirter is HUGE

I'm betting if you adv your timing and put a .025 or .028 squirter in there, you will be fine.

Previous owner said it was all stock. I don't know what cam is in it.
I set the mixture screws by lightly screwing in til they seat, then out 1.5 turns. I get good vacuum there as well as when I screw in a .5 turn each side. They currently are 1.5 turns out.
I'll install smaller squirter and advance the timing this weekend (if the shop gets done with my radiator...).

I wanna say that you are at 9.25 to 1 CR'd?? And it should be a -929 cam!

I've never played w/ a Holley on a 283, but the old little-bitty WCFB Power Pack intake system is a dandy on one! I figure, no more than a Duntov solid lifter cam and a set of headers and you are about 260 or so hp! Up from the 2-barrel, 195hp and 220hp PP/283 engines...

All this said, if you wanna work w/ the little short-stroke jewel, you can really rpm some big power outta her up top!

Hope you find her bog....

pdq67

PS., timing, He, He!! I used to time her by feel and ear up until she kicked back on the starter and then backed her off a schosh fine and this was w/ setting my points w/ a worn thin sliver dime!

Tom,
Just some basic questions. Did you change the wire for the distrubtor from a resistance wire to full 12 volts on the HEI? There should or still is a wire that is white and purple dashes. Need full 12 volts for HEI. Have you tried accelerator pump cams?

I'm getting a full 12Vdc from the fuse block. I have also tried 3 different cams and did not notice any change.
I got my radiator back and will try the smaller squirter and adv timing this weekend.
thanks

I still have the hesitation and could not even make it a little better.
I installed a .025 squirter, put the timing at 12 deg w/vac advance plugged, air mixture screws out 1.5 turns, vacuum at 20", and an idle of 1050rpm. The curb idle screw is all the way out and has no affect in lowering idle rpm. These settings also made the car run rich. Also, when I connected vac adv timing went to 47 deg.
I then put initial timing to 5 deg and screwed both air mix screws in .5 turns. This took care of the rich smell. Still had hesitation.
From there I tried random distributor settings to get best throttle responce. No luck.
I'm currently at 8 deg, 800 rpm, 19" vac and no rich smell. Timing jumps to 40 deg w/vac adv connected.
Also, the linkage is not holding butterflys open at idle.
2 questions:
Why is the curb idle screw ineffective?
What would you suggest I try next?
thanks again.
tm

Could the intake manifold (too big/too small) cause my problem? The one that's on the car is not original.

If you the vacuum advance removed. You should set your timing at 15 degrees and at 38 to 40 degrees at 2500rpm. That how I set up my 307cid. It ran great.

I find at around 12-15 deg that the car runs rich and I still don't have good initial throttle response.

I would check the PV. It may be damage. It's a common problem.
I used 750cfm vacuum sec. with 780 secondary metering block,
and an edelbrock torker manifold.
It never ran rich.

Could the intake manifold (too big/too small) cause my problem? The one that's on the car is not original.

What are the specifics on the manifold that's on the car? I scanned back through this thread and didn't see that you have listed it. Sure hoping it's a dual plane and not single.

Louis, are these parts on a 283?
I'll let you know what the manifold specs are...

Have you done a compression test? Could the timing chain/gears be worn if they are original? Ever do a cylinder balance test?

No, It was on a 307 bored to 317 with 64CC 202 heads. It similar to a 283. Same bore, just 1/4" stroke difference
The intake was single plain manifold.:D

I did a compression test but don't remember the average reading. However, the readings were all within 10% of each other.
Regarding timing chain, I had 7-8 degrees of slop. (turned the motor clockwise, checked mark on timing gauge, turned motor counter clock wise until distributor moved).
What's a cylinder balance test?

You should replace timing chain. That is too loose.

Cylinder balance test is a way to make sure all your cylinders are putting out power. Old way was to use a portable tach or even by ear. With the engine idling smooth, use insulated pliers to pull spark plug boot off one cylinder and note the rpm drop, put back on and move to the next. If you pull a plug wire and the engine doesn't change speed or sound you know that cylinder wasn't working. Could be simple like a bad plug. If you do a compression test first, that should rule out worn rings, valve not sealing , etc. so the balance test will just tell you that all 8 plugs are firing. Sometimes it is a fast way to discover where a miss is coming from, in your case it would just confirm all 8 are firing and working.

I have a picture of my Edelbrock manifold but on the bottom of the page it says I cannot add attachments. There is no visible part # or model # on the manifold.
How can I tell if it's a dual or single plane manifold?

I have a picture of my Edelbrock manifold but on the bottom of the page it says I cannot add attachments. There is no visible part # or model # on the manifold.
How can I tell if it's a dual or single plane manifold?

Strange that it wouldn't say anything but Edelbrock on it. I don't know of a way to determine without lifting the carb off the manifold. If you did that, and looked into the square opening below the carb, you would either see a baffle dividing the opening in half (dual plane), or a single, wide open square hole (single plane).

I did a compression test but don't remember the average reading. However, the readings were all within 10% of each other.
Regarding timing chain, I had 7-8 degrees of slop. (turned the motor clockwise, checked mark on timing gauge, turned motor counter clock wise until distributor moved).
What's a cylinder balance test?

tm66,

Replace that chain before it breaks, or it jumps a tooth. Seven or eight degrees is WAY too much.

Don't know what cam you are running, but that motor wants at least 12 degrees of initial advance as measured with a good timing chain. If it runs too rich afterward, that's a separate problem.

Don't recall seeing if you got your idle speed and mixture set right, but that has to be squared away as well, as well as your fuel level (float). As far as your idle speed screw not doing anything, are you sure that the fast idle mechanism is not sticking?

Mike

Replace that chain before it breaks, or it jumps a tooth. Seven or eight degrees is WAY too much.

Don't know what cam you are running, but that motor wants at least 12 degrees of initial advance as measured with a good timing chain. If it runs too rich afterward, that's a separate problem.

Don't recall seeing if you got your idle speed and mixture set right, but that has to be squared away as well, as well as your fuel level (float). As far as your idle speed screw not doing anything, are you sure that the fast idle mechanism is not sticking?


MIke,
I'm 99% sure the cam is stock.
The transfer slot on the secondaries is squared (I think that's what you're talking about).
I don't think the fast idle mechanism is sticking. When I 1st start it up, choke closes and it runs at high idle (1400 rpm?) and knocks down fine when it warms up. The only time that the idle screw is ineffective is when I advance the timing over about 12 deg. With timing at 5-6 deg, idle goes way down and I have to adjust (screw in) the curb idle screw to bring up the rpms.
I'll be lifting the carb to verify single/dual plane.
Keep up the suggestions and thanks to all...

I have an Edelbrock Performer intake. Is this the right one for me?

I have an Edelbrock Performer intake. Is this the right one for me?

That's a great choice. No problem there.

Yes, an old 2101 Performer is fine.

As are the newer ones and the Weiand 8004 by me! And I would buy the 8004 and have.

AND replace the plastic timing chain sprocket set!

pdq67

MIke,
I'm 99% sure the cam is stock.
The transfer slot on the secondaries is squared (I think that's what you're talking about).
I don't think the fast idle mechanism is sticking. When I 1st start it up, choke closes and it runs at high idle (1400 rpm?) and knocks down fine when it warms up. The only time that the idle screw is ineffective is when I advance the timing over about 12 deg. With timing at 5-6 deg, idle goes way down and I have to adjust (screw in) the curb idle screw to bring up the rpms.
I'll be lifting the carb to verify single/dual plane.
Keep up the suggestions and thanks to all...

Transfer slot on the secondaries? Don't you mean primaries? Those are the ones you use during idle.

If the idle speed screw has no effect, then either you have a vacuum leak, or the idle passageways are bigger than your engine needs. Since it's only a 600 cfm unit, my suspicion is that you have a vacuum leak.

Mike

Would I have a steady (not bouncing around) 17" readings w/vac gauge at idle if I had a vacuum leak? It's worth checking out again.
The transfer slot that requires proper adjustment on my Holley is on the secondaries. I previously opened and closed this to try to improve off the line throttles responce before I posted my problem here. I put it back to specifications (square) before posting so this could be ruled out as a potential problem.
Again, I only have a problem "off the line". I can't spin em.... The car runs fine otherwise.

What do you recommend next to fix my hesitation/stumble/bog ? :confused:

Would I have a steady (not bouncing around) 17" readings w/vac gauge at idle if I had a vacuum leak? It's worth checking out again.
The transfer slot that requires proper adjustment on my Holley is on the secondaries. I previously opened and closed this to try to improve off the line throttles responce before I posted my problem here. I put it back to specifications (square) before posting so this could be ruled out as a potential problem.
Again, I only have a problem "off the line". I can't spin em.... The car runs fine otherwise.

tm66,

Okay. What's your idle speed? If your idle speed is 700 or so, with a 17" h.g. and the idle speed screws aren't doing anything, then you probably don't have a vacuum leak. If it's around 1000 rpm with the idle speed screw backed all the way out, and you have that vacuum reading, then you may very well have a vacuum leak.

In other words, if you don't have a vacuum leak you should be able to bring your idle speed down to 650 - 700 rpms or so. Can you do so?

Mike

If the butterfly's aren't sitting square in the throttle bores it could have an effect on your curb idle adjustment. Hold the carb up to a strong light and look at them when they are closed to see if they are centered. You can center them by backing off the screws a bit and tapping the the butterflys on the closing side, or snapping them closed by the throttle shaft, then re-tighten the screws. Don't back off those retaining screws too much as they are distorted to keep them from backing out all the way and having your engine swallow them, but you should be able to back them off enough to get the valves to move, and don't overtighten them 'cause they will break.

Update. I installed a new Edelbrock performer intake cuz I found vac leak around old one and it looked bad! I removed heads also. Old time mechanic came by and said all looked good and it looked likt the motor was rebuilt/honed withing 15k miles ago. Put it back together w/new plugs. Resquared the secondary idle slot. Initial timing @ 18 and vac around 18". HOwever the idle was at 1200 rpm. The curb idle screw was out and I removed the rod from the accel pedal to make sure that wasn't holding main butterflys open. I had to close the secondary idle slot (turned that pia screw ccw). Idle now around 750.
Still have hesitation.
I tried the .035 and the .025 squirter and the pink and the orange plastic cam and notice no difference.
I couldn't telll if it's getting too much or too little gas when I rev it so I removed the plastic cam (eliminated the accel pump). This did the same thing (hesitated) but for a little longer time.
2 questions. Why is my idle so high when the secondary idle transfer slot is set so it looks like a square? and how can I test to see if it needs more gas from the accelerator pump?
thanks in advance

If I remember right, the old early E-brock 2101 is not marked as such on top, but only on the bottom? I have one so need to go out and look at it??????

I'm sorry, is it an old 4160, "1850" type 600cfm vacuum secondary carb??

A schosh big on a "stock" 283 when the old WCFB 4-barrel on the Power Pack 283's was only like 385 cfm or so?? It's been years so please bear w/ me. Hop her up and an 1850 Holley is mighty fine by me!

Personally, I'd install a decent Q-Jet off an early 305 and then see if your bog/stumble goes away. Bet it will..........

Good luck.

pdq67

I'm going to try to test out another carb. I don't know too many people who have old cars so this may take some time. Maybe someone will take my Holley as a trade in.