Syncing carbs

[bhull3]

First - I apologize if there is a thread on this subject, but I didn't see any.
I was in the process of syncing the carbs on my '65 Monza, using the steps outlined in the shop manual and Bob Helt's Corvair Basics. I came across a proceedure I didn't understand. There were instructions near the end of the proceedure to "pull the accelerator rod towards you (Powerglide pull to detent)." What does "pull to detent" mean?

[UNSAFE]

)." What does "pull to detent" mean

A detent is basically a notch that you should be able to feel as you pull the throttle.

This video may help . The carb adj starts towards the end of part 1 and continues in part 2.



http://www.youtube.com/watch?v=6jtm6s5_ ... re=related

[UNSAFE]

.

[bhull3]

Of course "tinkering and fixing" leads to more "tinkering and fixing".

I got the carbs synced per the shop manual. I also used a UniSyn to double-check. It will idle in N, but shakes a bit in D and has a rhthymic "gasping". I figure I'm close, but so as I don't mess with anything that doesn't need messing with, is it idle mixture, idle adjustment or accelerator linkage that might be the cause? I set all the screws 1 1/2 turns from their respective set points. I did notice that there was more vacuum on the right-hand carb than the left (when I covered the top of the LH with the Unisyn, I had to almost close the UniSyn up before the ball made it to the center). When I transfered the UniSyn to the RH carb, it almost shut the engine down using the setting I got from the LH carb.

The car ran fine before I had to remove parts to get to the head from a previous issue. I sprayed carb cleaner around the LH carb to try to find a leak, but no change. I did also notice the hose to the balance tube on LH slid on and off easily. I will replace it.

The car also now tends to shift sometimes with an audible "klunk" and it didn't do that before either. The LH carb looks like the original while the RH looks like a replacement or rebuilt (it was also the one that lost a throttle screw into the combustion chamber). Given time (which I don't have too much of), I could eventually figure it out, but I would like to enjoy the car before I pull out what hair I have left.

Bruce

[UNSAFE]

I set all the screws 1 1/2 turns from their respective set points. I did notice that there was more vacuum on the right-hand carb than the left (when I covered the top of the LH with the Unisyn, I had to almost close the UniSyn up before the ball made it to the center). When I transferred the UniSyn to the RH carb, it almost shut the engine down using the setting I got from the LH carb.

I'll try to answer part of your problems -

First off , 1.5 turns out with the screws does not accomplish anything . it is merely a starting point to get the engine started. The mixture screws must be fine tuned for each carb. Briefly you want to turn the mixture screws in (one side at a time) until the rpms drop slightly and then very slowly turn the screws out until the highest rpm is reached . Go no farther out after that , then turn the screws in about 1/8 turn. This should give you the beast idle mixture.
You should set the idle speed first with the unisync. NOTE : once you turn the adjuster on the gage to get the ball about in the middle of it's range you do NOT adjust it again. You must leave it where you started . Repeat Repeat !!!!

You adjust the carb idle speed screws to make the ball match on both sides . Not the gage. You may have to repeat one step after you do the other.

The rough shifting may be vacuum related due to the carbs not being balanced or a loose vacuum hose.

In the video the only difference is that they are using a vacuum gauge instead of the unisync. I'd watch it again now that you've done it once . The pertinent part of the carb adjustment is posted in printed form in another fairly recent thread.

[flat6_musik]

It will idle in N, but shakes a bit in D and has a rhthymic "gasping". I did notice that there was more vacuum on the right-hand carb than the left (when I covered the top of the LH with the Unisyn, I had to almost close the UniSyn up before the ball made it to the center). When I transfered the UniSyn to the RH carb, it almost shut the engine down using the setting I got from the LH carb.

The car also now tends to shift sometimes with an audible "klunk" and it didn't do that before either.

Hmmmm....a rhythmic gasping sort of sounds like an engine misfire to me. I would guess that either you need to turn the idle speed screw up on the LH carb or......it's time to check the compression on that bank. The fact that you say that carb doesn't have much suction has me wondering.

[bhull3]

Thanks for the responses guys.

I did keep the Unisyn at the same setting when I moved between carbs. I will start my trouble shooting with the simplier first - replacing the most loose vac hose. I take it I need to get a tachometer to do this job right, huh? Or are slight slight deviations from the manual settings ok to be performed "by ear"? (idle screw/idle mixture adjustments).

Also, when you use a Unisyn, don't you have to have at least one carb at /near the correct setting?

What gets me is that the car ran smooth before I "opened it up", so I know the nirvana state is in there somewhere.

[bhull3]

When I go to adjust the mixture screws, I barely notice any difference in rpms when I adjust the mix screw on the left carb. There is a noticable difference in the right carb adjustment. I actually got them balanced and synced and drove the car around for a while. BUT then I decided a little more tweaking might be necessary, so I turned the mixture screws a little more and now it's unbalanced again (idles fine in N, but shakes in D). Tried putting the screws back where I thought they were, but not working. The idle speed screws seem to be set fine; just need to get the mix right. I didn't realize the adjustment was that sensitive. Lesson learned: when I get it right again, I will leave it alone.

[Corvair.crazy]

Well I would suggest a tool. For tune-ups I would say it is required.

On Amazon for 28 bones

Dwell tach.jpg (15.66 KiB) Viewed 4140 times

Also a vacuum gauge. Back in shop class I was taught to adjust the idle mixture to obtain the highest vacuum at idle. Vacuum at idle should be around 20"

So there you go, my

[bhull3]

Watching video part 2; referring to connecting the vacuum gauge - isn't the vacuum advance for the distributor connected to the RH spark port tube? Do I connect the vacuum gauge tube to the port where the choke diaphragm is connected?

[66vairguy]

See your other post viewtopic.php?f=225&t=10563" onclick="window.open(this.href);return false;

I think your question about pulling the throttle lever to the "detent" per Bob Helts book is about the WOT (wide open throttle) position. It's not unusual for the throttle linkage adjustments between the gas pedal and engine to be off so when you depress the throttle pedal to the carpet the carburetors do not open all the way. If you are by yourself then pulling the throttle rod at the engine to make sure it opens the carburetors throttle plates all the way is one check. After all these years and worn linkage bushings it's better to have someone sit in the car and press the throttle pedal to the floor while you check that the throttle plates are open all the way (with the engine off or course). If adjustments don't work it's time to check the bushings at the rear throttle pivot arm under the car or at the transmission pivot.

[GriffinGuru]

Are you still getting the rhythmic gasping? I had this type situation when I first started to adjust my carbs after getting my car. When I first got it, it idled really high- like 1500rpm possibly (I have no tach). I rebuilt the carbs and then went through the process of synching them with the help of the videos provided by Brad on thei forum and my shop manual.

When I got the idle down to where it was supposed to be, I noticed what I described as a "Whuff, whuff, whuff" sound in time with the engine. This was only on one side and also affecting the carb on that side by messing with the manifold vacuum and making that carb spit gas and do funny things.

In my case, I did some bleed tests, and I had removed all the valve rockers. On installing them all back in for the compression test, my "whuff" sounds were gone and the engine was running smooth after I put if back together (in a feeling of defeat at the time since I thought I had major internal problems). My case happened to be some overly adjusted valves that must have been staying open a little bit and losing compression. I also happened to find a dud plug in that process that wasn't firign on that same cylinder bank.

You said you had to get to the head to fix something. Could your valve rockers be over tight like mine were?

[66vairguy]

Good trouble shooting Giffin! Incorrectly adjusted valves are not uncommon. You didn't mention if you also did a "HOT" (engine running valve adjustment). I find that a static adjustment (necessary when assembling an engine) is usually close, but the hot run adjustment is more accurate.

[GriffinGuru]

Hi '66 and all,

No I did not do a hot running adjustment. I did some searching on the previous forum posts and I saw that a lot of people were saying the cold adjustment usually gave them just as good results as the running hot adjustment. I did it cold because I also do not have any sort of cut valve covers to contain the oil mess that would be involved with the running adjustment. I turned the rockers until the pushrods were starting to tighten/lash, and then went 1/3 turn past. There was a lot of opinion on the forum that the factory specs of a full turn after lash was too much, so that's why I only went 1/3 turn. I did also rotate the engine around and re-checked my adjustments again, and on most I found they needed further adjustment a second time; probably due to the lifters bleeding or releasing some oil pressure after they were set originally.

I have ordered new rockers since the ones I mentioned were shot and were only put back in for temporary use and a compression test. I have a all new set with the grooved rocker balls from Clark's, but I am waiting on another used push rod, since I didn't notice a damaged one when I ordered my rockers. Once that push rod comes in I will install the new ones the same way as the original ones: cold adjustment at #1 TDC, followed by at #2 TDC, with 1/3 turn and then re-check everything after rotating around again to #1 and then to #2TDC, and 1/3 turn again.

This should take care of my motor internals for a while so we shall see how it holds up long term, but if the cold adjustment alone eventually proves to be inadequate I also am putting on rubber valve cover gaskets so I should be able to remove those again with less hassle.

[azdave]

I came across a proceedure I didn't understand. There were instructions near the end of the proceedure to "pull the accelerator rod towards you (Powerglide pull to detent)." What does "pull to detent" mean?

Detent?

If you have an auto tranny there is a point when pressing the throttle (so the lever at the transmission rotates) where you meet resistance and then it travels a little more. That is the "detent" being mentioned. It's only on automatics and it's the point where the tranny knows you have heavy throttle applied and are probably looking for a downshift to first gear if other conditions are met.