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1977 Chevy K20: Engine Suffers from Hesitation/Power Loss When In Drive

92K views 157 replies 14 participants last post by  cobalt327 
#1 ·
Hi All,


I have a 1977 Chevy truck with a stock crate 350 engine and a 3-speed auto transmission. It seems to be suffering from power loss when in Drive. I drove the truck yesterday to move for the street sweeper and it gave no trouble.


This morning, the truck started up just fine, but when put into Drive, it had a serious loss in power. At first I thought it hadn't warmed up right and gave it more gas but it was more of the same. So I pulled over, shifted into Park, and gave it some gas. The engine revved smoothly with no issues.


So I shifted back into Drive and started driving and still no power. For reference, it was getting to 25 mph in over 10 seconds and there was no chance at going over 35 mph. It also was making a bhup-bhup-bhup noise. I tried shifting manually but that was of no use either.


I haven't had a chance to pop the hood and look at anything, but could it possibly be that the vacuum line to the transmission has come loose?


Thanks in advance, :thumbup:
 
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#27 ·
about the modulator's piece of hose, it's a good idea replacing it for a new one even though I don't believe that's is your problem, but let me tell you that I have seen modulators that fail, they get the internal diaphragm riped and let the engine suck ATF, that makes them smoke and run terrible. easy check, disconect the lline at the carb end and stick a piece of white paper, a napkin or something, it should come out clean, no traces of red ATF.
 
#28 · (Edited)
Hey Chet,
T-bucket23 said:
Try this, when the truck is cold like in the am after sitting all night.
Open the hood and take off the air cleaner top.

Push the gas pedal to the floor and release then check the choke plate, it should be shut tight.
I tried that this morning and below is a quick 14 second video of it. The choke plate closed the first time I floored the accelerator pedal. I did it a total of three times.






T-bucket23 said:
Start the truck with the air filter top off and look at the choke plate, it should pop open 1/4" or so, If not the pull off is not working.

Let it run for about 5 minutes and look at the choke again once the temp gauge gets up to about 1/4 this may take longer if you have no thermostat. The choke should be fully open. If not then it is binding or junked up.

If you tap the gas at this point the fast idle cam should drop out.
I was able to run it for about five minutes this morning, but not long enough the to get the temperature up there. Outside temperature was approximately 45 degrees F this morning when the video below was shot.



In Case You Can't See the Video:

- Truck is started with no issues. Choke pull off operates immediately.

- Truck is allowed to idle/warm up until 2:25 mark, at which point the engine is revved to about 2,000 rpm, and can be heard bogging (a hissing sound can be heard). The fast idle cam is seen dropping. Fuel flow can be seen in the glass-cased fuel filter right before the carb as remaining steady.

- The engine is revved again about three more time up until 3:00 minute mark. The engine revs slightly higher, but the hissing and bogging can still be heard.

- Engine is revved again at the 3:35 mark, slightly past the 3,000 rpm mark. Hesitation and hissing still evident, but less so than before.

- Engine revved at the 4:25 mark to about 4,000 rpm. No hesitation or hissing heard.

- Transmission is slowly shift through every gear starting at 4:55 mark. Shifted back into Park at 5:05 mark.

- Engine revved again at 5:10 and 5:17 marks to 4,000 rpm. No hesitation or hissing is heard.




I did take the truck for a spin twice and it was running crappy again, despite me pulling over and revving it. I would have liked to have gone for a longer spin but, it was morning rush hour and I really didn't wana deal with all the middle fingers while barely pushing 30 mph.




I'll try to get another test run in before going to work, hopefully long enough to get the temperature up.




-----




@ Augusto: Thank you for the heads up on testing the modulator. I will do that when I also end up replacing the rubber hose ends on the vacuum line.
 
#29 ·
been thinking of your problem, did you know that q-jets have this infamous welch plugs under the fuel bowl that always leak? they are under the main circuit fuel wells, two adjacent plugs that are some sort of pinned/riveted/hammered down or someting, they need to be seal covered with epoxy, when they leak your mixture becomes very rich, and is likely that when the carb gets hot the gaps grow bigger and the leak increases upsetting your mixture, they'll dump lots of fuel directly above the throttle plates.

one sure way to know you have this problem is when you let the car sit for two or three days, it takes long to start because the fuel bowl has drained empty.

some carb rebuild kits have this piece of dense foam that is inserted between the main body and the throttle plates body gasket, where the big hole in the center is, to help sealing this leaks but I have found it does nothing, only epoxy cures this problem.
 
#30 · (Edited)
Hey Augusto,

The carb was rebuilt about a year ago. The previous rebuilder had used some sort of silicone-ish material to cover the wells. I used some five-minute epoxy. You can see pictures of it here on on post #21 on page 2.


The truck is usually started only once a week, and I always pump the pedal three times and then floor it when starting. I'm pretty sure I've had to do the same even when starting it the following day. I'll test it out over the next couple of days to see what happens.


I know I am not checking things and coming back with results very quickly, and it is a time issue. The tentative plan now is to do what I listed in post #25. Got a 4 day weekend coming up so I'm hoping to go through all this in a day.


EDIT: If need be, I can remove the air horn and check the wells. Most likely a last resort deal.
 
#31 ·
the epoxy job looks good, but let me tell you I have seen 'em fail after some time, right now my own C30 is having this problem, they leak a lot, and after 2 days I have to prime the carb to start it up, gives me no driveability problems though, just the inconvenience of removing the air cleaner to fill up the fuel bowl before cranking.
 
#32 ·
Augusto said:
the epoxy job looks good, but let me tell you I have seen 'em fail after some time, right now my own C30 is having this problem, they leak a lot, and after 2 days I have to prime the carb to start it up, gives me no driveability problems though, just the inconvenience of removing the air cleaner to fill up the fuel bowl before cranking.
I'll go ahead an inspect it if that turns out to be the problem or, knowing my luck, one of the problems. I may just have to try using plugs. :sweat:
 
#33 ·
As planned in post #25, I went ahead and cleaned out the fuel filter today. There was quite a bit of crap, very similar to the stuff found when the truck began having problems from contaminated fuel over a year ago. See post #19 on page 2 and #38 on page 3 for reference images.

I washed everything out with water, dried it all up using shop towel and reassembled the filter.








-----




Next item on the list was to check the fuel pressure. I went to Harbor Freight and swapped out my fuel pump test kit for a new one since mine was missing the t-connector.

I installed the t-connector in place of the fuel filter and hooked up the gauge to it.








I then performed the fuel pressure test three times. You can see the video of all three tests below.


The first time, fuel starting shooting out where the t-connector was because I had not clamped it down tightly enough. The gauge was showing 7 psi. I did rev the engine and it was hesitating. I loosened up the fuel hose to relieve pressure and reset the gauge to "0".


The second time there were no issues. I let the truck run for several minutes and revved it a few times and there was no hesitation. The gauge showed 7 psi. I again loosened up the fuel hose to relieve pressure and reset the gauge to "0".


I then did it a third time. Again, it showed 7 psi.


I did not get to do a volume test today because I did not have someone available to help me out so one could keep an eye on the fuel and the engine.




 

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#34 ·
A note on the video in the previous post:

- At the very beginning, the gauge is already at around 5 psi, most likely due to the priming of the accelerator pump. It was at zero when recording was begun but the parts during which the truck was not running were cut out to save time.

- The fuel pressure is seen dropping slightly as the engine is heard revving at the 3:38, 3:52 and 4:12 marks.



If I remember correctly, the fuel pressure should be 5 psi. Is that right? If so, how should I lower it from 7 psi?
 
#35 ·
From what I read, it would like you have a timing problem.

Get the truck warmed up and running and set the timing BY EAR.

Rev the engine up some, maybe 3000 rpm and move the dist more and less advance. The engine should speed up and slow down some.

Set it to where the engine is running the fastest, then back just a little bit.

tighten everything up and drive the truck and see if it helps. If it does, you have a problem with your timing!
 
#36 ·
Hey BigRoy,
BigRoy1978 said:
From what I read, it would like you have a timing problem.

Get the truck warmed up and running and set the timing BY EAR.

Rev the engine up some, maybe 3000 rpm and move the dist more and less advance. The engine should speed up and slow down some.

Set it to where the engine is running the fastest, then back just a little bit.

tighten everything up and drive the truck and see if it helps. If it does, you have a problem with your timing!
Several suggestions have been made as to what the real issue(s) are, and I am trying to go through them one by one. Timing may very well be an issue since it was set by ear a few months back, and not by using a timing light. When it was set by ear, it was running perfectly. Just a couple of weeks ago it decided to start having these weird hesitation problems.


Got to do some work on the truck today. Continuing with the list in post #25, I installed a new thermostat. The bolts for the thermostat housing looked like crap. And I just cleaned 'em back in June of last year. (see post #130 here. Anywhoo, in went the Fail-Safe 195 degree thermostat. The bolts got cleaned up using carb cleaner and a wire brush. The flush was not finish today.







I then fired up the truck and found that the recently cleaned glass filter was leaking fuel. Once everything got fitted ans tightened down, I gave it another start and allowed the truck to warm up for a few minutes before going for a spin. The truck was still not wanting to run smoothly so I just let it run in Drive on its own at about 20 mph up and down a small street. I kept an eye on the temperature the entire time.

Now, this truck has two temperature gauges: one on the dash and the other below the dash, about right in the middle so both driver and passenger can see it. In the past, I have noticed that the temperature on the goes up a lot more slowly than the reading on the gauge below the dash. But they have always come to the same temperature. Not today. Today, the temperature reading on the gauge below the dash was much higher than the gauge on the dash. I have not taken the time to trace which gauge connects where, but I am guessing one is giving the coolant temperature and the other is giving the engine temperature. Sound about right?






After the first spin in the truck, I pulled over and revved the engine again, all the way up to 4,000 rpm at times. I noticed that the truck routinely hesitated for a split second at the 2,500 rpm mark. I took the truck for a second spin to see if the transmission would shift smoothly this time, but no luck.


I then brought out the timing light, but before I hooked it up, I decided to check the vacuum for the vacuum advance canister. I have no idea what I was looking for, but I have to say that there was no vacuum pull on the carburetor where I had originally hooked up the line from the distributor. I immediately hooked the line up to another opening which was previously capped off and there was suction there. I unfortunately can't remember what the vacuum reading was. The engine rpm immediately jumped up from 750 rpm to 1,000 rpm on the tach.





I took the truck for yet another spin, but there was no difference in the hesitation and shifting.


I the hooked up the timing light and, try as hard as I might, could not see the indentation on the balancer as the light was flashing. I figured that it the color was just too dark so I tried using some pink nail polish (yes, I borrowed it. Leave me alone. Whatever :rolleyes: ), but that didn't do any good. I even sprayed some gold spray paint over the mark but still nothing showed up under the light. So I tried to see if perhaps the video camera or even the boroscope might pick something up, but no luck. And it proved quite challenging to operate two devices at once right over the spinning fan.







Maybe I am just losing my sight. Or is the timing off by so much it doesn't even land on the tab marks? Or is the engine speed to fast for it to be visible, in which case I should retard the timing a bit?

Next on the list: replace the rubber hose ends on the vacuum line to the transmission modulator. Test the modulator.
 

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#37 ·
If you can't see the mark its either....

Your piece that goes on the plug wire for the timing light is on the wrong wire

or

Your timing is WAAAAAAYYYYYYYY off.

Its not from the engine spinning too fast, I set the timing on my roundy round engine when its at 7 grand...and you see it plenty easy.

another thing to check...

The vaccum connection on the back of the carb that goes to the brake booster. If it is connected tight, and the hose doesnt look cracked...disconnect the hose and plug the vaccum outlet on the carb.

I have seen one or two times where the vaccum booster was sooo worn out that it caused a massive vaccum leak.
 
#38 ·
I think you need to get the timing set before you go any further. Have you tried turning the dizzy while running the light to see if the mark will come around? Did you have the light hooked up to the right wire? I have hooked it up to the wrong wire before. How old is the light? You shouldn't have any problems seeing the mark even at 5000 rpms the mark should look like it standing still.
 
#39 · (Edited)
Hey crussell and BigRoy,

I did not have a chance to turn the distributor while using the timing light because I ran out of time for today. And yes, the wire was the #1 plug wire, with the arrow correctly pointed towards the plug.

The timing light itself is brand spanking new: Equus 5568 Pro-Timing Light with Tool Case

I'm not sure if I mentioned it on this thread, but the distributor did fall off once a few months back, about 2 feet off the ground. Any chance that might've damaged something?


 

Attachments

#40 · (Edited)
I was watching the video made yesterday, and noticed that the fast idle cam never dropped.






However, when the movie was made when observing the choke pull off and the fast idle cam, the cam dropped after about two and a half minutes.






I thought the video below had some interesting info. I didn't keep an eye on the fast idle cam today, but will definitely watch it next time when I starting adjusting the timing.






If the distributor turns out to be a problem, I am considering this one from Skip White Performance. The price is very low and the warranty is excellent. Hopefully, so is the performance.
 
#41 ·
I wasn't able to see the video (problem on my end), does the choke ever completely open?

The timing mark won't be visible if the vacuum advance is hooked up to a manifold vacuum source,

If it was disconnected and plugged, the timing tab/damper line may be off; there were three Gen I tabs/dampers that may be confusing the issue.

DETERMINING TDC will allow you to be sure the timing tab and damper are correctly indicating TDC.

MAKE A TIMING TAPE to see what the total timing is, w/o needing to use a dial back timing light. You can also buy a timing tape, get one that matches the diameter of your damper.

The image shows the correct orientation of the timing tape:


Because the distributor is running the engine, I doubt the drop did any real harm. I would expect a no-start condition if the module or pick up coil had been damaged by it falling. Sometimes modules will run fine cold but give problems when they're hot. The pick up coil can exhibit erratic behavior if the wire inside the insulation is broken from the movement of the advance plate on the distributor.

If you need it:

REBUILD HEI-

HERE'S an exploded view of an HEI distributor.
THIS is a description of an HEI rebuild. HERE is another HEI info/rebuild page.
 
#42 · (Edited)
Hey cobalt,
cobalt327 said:
I wasn't able to see the video (problem on my end), does the choke ever completely open?
When the truck is first started, the choke pull off starts working immediately, and the choke plate opens up to the 3/4 of the way before coming back up to about half way open a few moments later. However, I can't seem to tell if the choke it self is working (divorced choke). Perhaps if any of the other members can tell, they can chime in.




cobalt327 said:
The timing mark won't be visible if the vacuum advance is hooked up to a manifold vacuum source,

If it was disconnected and plugged, the timing tab/damper line may be off; there were three Gen I tabs/dampers that may be confusing the issue.
The vacuum advance is hooked up on the carburetor. I'm not sure if that could still be manifold vacuum though. I did not disconnect or plug the advance while trying to get an initial timing reading. I will check up on the tab and damper to make sure everything is good there. The timing tape looks like an interesting project to make.




cobalt327 said:
DETERMINING TDC will allow you to be sure the timing tab and damper are correctly indicating TDC.

MAKE A TIMING TAPE to see what the total timing is, w/o needing to use a dial back timing light. You can also buy a timing tape, get one that matches the diameter of your damper.

The image shows the correct orientation of the timing tape:
I did remove and reinstall the distributor several times last year and "found" the TDC by using the timing tab. It was last set at 9 degrees BTDC on the damper (see pages 10 through 13 for reference on that). If need be, I can do so again after making sure the timing tab and damper are ok.




cobalt327 said:
Because the distributor is running the engine, I doubt the drop did any real harm. I would expect a no-start condition if the module or pick up coil had been damaged by it falling. Sometimes modules will run fine cold but give problems when they're hot. The pick up coil can exhibit erratic behavior if the wire inside the insulation is broken from the movement of the advance plate on the distributor.
Yes, there have been no issues with starting. The coil itself was recently replaced a couple of weeks ago. And module "passed" the test at Autozone a few times. If the temperature can be an issue for the module, I think I ran the truck long enough to get it warmed up enough and would have noticed if there were any issues. But I suppose it could be random if the module acts up or not?




cobalt327 said:
If you need it:

REBUILD HEI-

HERE'S an exploded view of an HEI distributor.
THIS is a description of an HEI rebuild. HERE is another HEI info/rebuild page.
Thanks! If it comes down to it, I can take it apart and check everything out. Now I have a better of idea how of the insides work.



Thanks for the continued help! :thumbup:
 
#43 ·
First let me say I agree that you need to get the timing correct. Second I will say I dont think it is your issue. In past posts you have said that you took it for a ride and sometimes it is fine.
Everything you have posted points to fuel, choke or carburation issues.
In one post you said the choke goes to half way closed then went back to 3/4. This is not right.

I would recommend as your next test you disconnect the choke and wire it open, warm it up and take it for a spin.

Note if the engine is cold it will be hard to start with the choke wide open and you may need to baby the accelerator for a few minutes to keep it running.
If it still runs poorly you have eliminated one thing, the choke. Then move on from there.
 
#44 · (Edited)
Hey Chet,
T-bucket23 said:
First let me say I agree that you need to get the timing correct. Second I will say I dont think it is your issue. In past posts you have said that you took it for a ride and sometimes it is fine.
Everything you have posted points to fuel, choke or carburation issues.
In one post you said the choke goes to half way closed then went back to 3/4. This is not right.

I would recommend as your next test you disconnect the choke and wire it open, warm it up and take it for a spin.

Note if the engine is cold it will be hard to start with the choke wide open and you may need to baby the accelerator for a few minutes to keep it running.
If it still runs poorly you have eliminated one thing, the choke. Then move on from there.
I will try this the next time I fire it up.


----------


I did make a video of the truck starting and warming up for nine minutes today.



In Case You Can't See the Video:
- Engine starts on the third try.

- Truck is allowed to warm up on its own for the first 8 minutes.

- Choke-pull off closes and the choke plate open up at the 00:15 mark.

- Camera is panned towards the firewall at the 3:45 mark. Light smoke can be seen coming out from the rear exhaust manifold area. Oil seems to be back there. Might explain the fouled plugs on the passenger side?

- Idle cam falls at 8:00 mark when the accelerator pedal is pressed for the first time.

- Coolant starts leaking out of the upper radiator hose at the 8:04 mark. One of the bolts for the water neck wasn't tightened down all the way. Tightened up afterwards.




I then took the truck for a spin on a couple of nearby streets. The video is made from inside the truck and hopefully you can hear the engine hissing and hesitating when gas is given. The video is chopped up to shorten the time.


In Case You Can't See the Video:

- Truck ran under its own power at approximately 20 mph, except when gas given at : 00:14, 00:16, 00:20, 1:23, 1:26, 1:54, and 1:56. Hissing can be heard.

- Truck was parked and revved a three times from 2:20 to 2:43. Engine revved fine, except for the unnoticeable hesitation at 2,500 rpm.

- Truck allowed to run under its own power again. Gas given at 2:51 and 2:59. Hissing heard.

- Truck parked again. Revved at 3:09 mark. Engine revved with the hesitation at 2,500 rpm mark.
 
#45 ·
Choke is taking to long to open. Do you still have a heat riser valve in the exhaust and is it free. The choke should be fully open in about 3 minutes or so and should never close up while running. It appears in the video yours actually looked like it closed a little a few times during the warm up cycle
 
#46 ·
T-bucket23 said:
Choke is taking to long to open. Do you still have a heat riser valve in the exhaust and is it free. The choke should be fully open in about 3 minutes or so and should never close up while running. It appears in the video yours actually looked like it closed a little a few times during the warm up cycle
The truck doesn't have a heat riser valve. And yes, the choke plate does seem like it moves back towards the closed position a few times. Should I try a new choke?
 
#47 ·
q-jet choke's are crap, just get a piece of wire and fix it wide open or remove the butterfly, try this first.

about timing, set your timing at 8 deg BTDC with the vaccum lines disconected and pluged at the carb, this will give you a good starting point, once done start the engine and check if the timing mark advances when you rev up the engine, should go to something like 20 degrees BTDC.

after this connect the hose to a ported vaccum source, the one with no vaccum at idle, this will give you a good average performance and no issues.

drive it and if still gives you problems replace the carb.
 
#48 ·
1977 K20: engine suffers from Hesitation/Power loss when in drive.

[I have a 1977 Chevy truck with a stock crate 350 engine and a 3-speed auto transmission. It seems to be suffering from power loss when in Drive. I drove the truck yesterday to move for the street sweeper and it gave no trouble.


This morning, the truck started up just fine, but when put into Drive, it had a serious loss in power. At first I thought it hadn't warmed up right and gave it more gas but it was more of the same. So I pulled over, shifted into Park, and gave it some gas. The engine revved smoothly with no issues.


So I shifted back into Drive and started driving and still no power. For reference, it was getting to 25 mph in over 10 seconds and there was no chance at going over 35 mph. It also was making a bhup-bhup-bhup noise. I tried shifting manually but that was of no use either.


I haven't had a chance to pop the hood and look at anything, but could it possibly be that the vacuum line to the transmission has come loose?


Thanks in advance, :thumbup:[/QUOTE]
 
#49 ·
fasteddy_1947 said:
[I have a 1977 Chevy truck with a stock crate 350 engine and a 3-speed auto transmission. It seems to be suffering from power loss when in Drive. I drove the truck yesterday to move for the street sweeper and it gave no trouble.


This morning, the truck started up just fine, but when put into Drive, it had a serious loss in power. At first I thought it hadn't warmed up right and gave it more gas but it was more of the same. So I pulled over, shifted into Park, and gave it some gas. The engine revved smoothly with no issues.


So I shifted back into Drive and started driving and still no power. For reference, it was getting to 25 mph in over 10 seconds and there was no chance at going over 35 mph. It also was making a bhup-bhup-bhup noise. I tried shifting manually but that was of no use either.


I haven't had a chance to pop the hood and look at anything, but could it possibly be that the vacuum line to the transmission has come loose?


Thanks in advance, :thumbup:
[/QUOTE]

If it was the vacuum to the trans either the engine would...

1. Idle fast...cause of a vacuum leak

or

2. the trans wouldn't shift until you had the engine up around 3500-4000 rpm


power loss like that, where it will go to one rpm and doesnt want to get anymore is an ignition/timing problem.
 
#50 ·
lt1silverhawk said:
The truck doesn't have a heat riser valve. And yes, the choke plate does seem like it moves back towards the closed position a few times. Should I try a new choke?
Disconnect the choke and see how it runs. Without a heat riser that style choke will not work well. The heat riser forces some of the exhaust back through the manifold to warm it up. Using the wrong intake gaskets can also cause issues.
 
#51 · (Edited)
Hey BigRoy,
BigRoy1978 said:
If it was the vacuum to the trans either the engine would...

1. Idle fast...cause of a vacuum leak

or

2. the trans wouldn't shift until you had the engine up around 3500-4000 rpm


power loss like that, where it will go to one rpm and doesnt want to get anymore is an ignition/timing problem.
Well it does take some time and/or revving before the transmission shifts. What's strange is that there have been times (during the past few weeks since the truck began exhibiting this problem) where I've spent time letting the truck idle for quite some time while revving it up to 4000 rpm here and there. I would then take it for a spin and everything would work fine. But other times, like in the most recent videos, it doesn't want to run well no matter what I do.


The first time the truck began running fine after first displaying these problems, it was after I checked and cleaned all the plugs, tested out the ICM, and installed a new ignition coil. See post# 9 of this thread for more details.


After that, two days later, the truck exhibited the same symptoms, but they went away after revving the engine to 4,000 rpm a few times. The same thing again happened the following day. See post #15 and #17 of this thread for details.


After that, the truck has not run well in Drive no matter what. Now the added mystery is why there is the ever so slight hesitation at the 2,500 rpm mark when revving the engine in Park and Neutral.




Hey Chet,
T-bucket23 said:
Disconnect the choke and see how it runs. Without a heat riser that style choke will not work well. The heat riser forces some of the exhaust back through the manifold to warm it up.
I do not want to sound as if I am disagreeing, but I am wondering if that would have been a problem before too. Because the truck has been running just fine in the past, save the dirty fuel / carburetor rebuild issue last year.


T-bucket23 said:
Using the wrong intake gaskets can also cause issues.
Ah those intake gaskets. Did 'em twice last year. You can see which ones on page 9. Since both you and sbchevfreak have brought up the manifold gasket issue, maybe its time to do it a third time. The timing can be tackled from the beginning too, like I should have done.
sbchevfreak said:
Is it just me, or do the "even" plugs look to be badly oil fouled? If so, I would be looking at intake gasket sealing on that side....
I can disconnect the choke and fire it up next time, and also open up the choke plate by tying it down.



EDIT:

Hey Augusto,
Augusto said:
q-jet choke's are crap, just get a piece of wire and fix it wide open or remove the butterfly, try this first.
I will be trying this, along with disconnecting the choke on the next try.


Augusto said:
about timing, set your timing at 8 deg BTDC with the vaccum lines disconected and pluged at the carb, this will give you a good starting point, once done start the engine and check if the timing mark advances when you rev up the engine, should go to something like 20 degrees BTDC.
I've seen various numbers on the what the timing should be set at, ranging between 12 BTDC to 6 BTDC. I read somewhere that 10 BTDC was a safe number to start with. I'll start with 8 next time. It seems like the manifold may be getting yanked again.


Augusto said:
after this connect the hose to a ported vaccum source, the one with no vaccum at idle, this will give you a good average performance and no issues.
Ok, so the one where the vacuum advance was previously connected to.


Augusto said:
drive it and if still gives you problems replace the carb.
I've got another core I can rebuild, though I hope it doesn't come down to that.
 
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