First time dist tune up and carb questions

[LAC_STS]

As per my earlier thread I decided to do a tune up on my Prestolite points style dist.

I am trying to fix some issues on a new engine I have. It has 22 hours on it right now. It will run good then it will start backfiring and bogging at anything over 2K RPM.

I have had a problem even when it is running good where it will bog when the secondaries open.

Here is what I got today.


This is my first time dealing with a carb or points IGN so bear with me please. You guys have been a life saver in all this.

I read the how to on points in the FAQ and I read up in other places too.

I bought a tune up kit (points, condenser, rotor, and cap) for my dist. I also bought a digital timing light that tells you the RPMs too and it has an "advance" feature which I have no idea what it is.

Per manual for my engine. Timing at idle (650RPM) 8 BTDC, Point gap .0018
Dwell, 27-31

Before I took the points out of the old dist I checked the timing. It was right at 8 BTDC. I also checked the gap on the old points when the points were opened and I couldn't even get the .0018 feeler in there. The looked nearly closed.

I replaced all of the tune up stuff in the dist. After some trial and error I got the points right on to 29 with the dwell meter which is half of the 27-31 it says in the manual.

After I did that I hooked up the timing light and the timing had moved to 15 BTDC.

It was getting dark then so I packed up and will fininsh tom.

Questions about this:

Where is the mechanical advance? How do I check it and fix or replace it?
Does what I have described above sound right? Timing went from 8 to 15 degrees? If it is right then my old points and dwell must have been way off right?
Pic of my dist. I already took the condenser out.

Now about the carb. I have been having problems with the bogging when the secondaries open.

I just pumped all the gas out of the tank and inspected the tank and filled it back up about 1/2 full with fresh gas and some Stabil. also installed a new fuel/water sep filter.

I took the boat out today for about 30 mins to check it out after replacing the gas. I took the flame arrestor off while my girl drove and I manually operated the secondaries from the carb.

The secondaries DO open all the way and the air butterflies DO open also.

BUT... When I had the thing wide open with the secondary butterflies open all the way, the primary jets (both the big ones on top and the very small ones under the air butterflies) had a TON of fuel coming out of them.

On the secondaries though the very small jets that are under the air butterflies were spraying a bunch but the big butterflies on top were squirting next to nothing. I mean really nothing. Barely anything just 1 percent of what the primary ones were.

Is this normal? If not what could be wrong? Could this be the cause of my bogging at WOT and what do I do to fix it? Adjustment?

Also look at this video I took today. I am not sure if this choke was this way before but I think it was not. If I remember right the bar on the side would close the choke plate if you moved it. Now it just moves up and down and doesn't cause the choke plate to move.

Look wrong or broke to you guys? If this choke is broke or not working what kind of problems could this cause?

http://www.youtube.com/watch?v=8_SMqUV9V48


Thanks again everyone. I really really appreciate it!!!

 

[Alpheus]

Re: First time dist tune up and carb questions

You need to rebuild the carb or at least check your float adjustment. My carb was doing the exact same thing, as far as shooting tons of fuel. Turns out the floats where way out of adjustment.

As for the choke. Its just held open with a spring. It wont cause your engine to bog unless its stuck closed. You could take it off if you wanted to...

You can get a rebuild kit for an edelbrock at your local auto parts store...

 

[LAC_STS]

Re: First time dist tune up and carb questions

Not saying it doesn't need rebuilt cause I don't know but it's brand new. Only has 22 hours on it and it's bogged since I got it.


When I say tons of fuel I mean what you would expect from WOT. While the secondaries big jets on top of the air butterfly don't barely shoot anything, just the little jets under the butterflies on the secondaries do.

I assume this is not how a carbs secondaries are supposed to work right?

Is there an adjustment that would make the secondaries bigger jets shoot more fuel? Or is that to do with the floats?



Thanks

 

[libellav15]

Re: First time dist tune up and carb questions

Lac - why ask advice if you are certain you already know the advice is wrong

the fact that the carb is 22 hours old points to the fact that the float needs adjusting if anything, sounds like the needle isn't seating and its flooding up - which it clearly is if the venturis are sucking that much fuel through,


simply pop the carb off and make sure the needle seats correctly and check the float height. only about an hours work, and worth it to eliminate if nothing else.

and re the choke mechanism - its probably because the engine is warm and the choke is off that the lever you are worried about seems so slack - that releases the choke plate to fully closed (via the auto choke spring) when you return to a previously run engine for a cold start.

 

[libellav15]

Re: First time dist tune up and carb questions

Lac - why ask advice if you are certain you already know the advice is wrong

the fact that the carb is 22 hours old points to the fact that the float needs adjusting if anything, sounds like the needle isn't seating and its flooding up - which it clearly is if the venturis are sucking that much fuel through,


simply pop the carb off and make sure the needle seats correctly and check the float height. only about an hours work, and worth it to eliminate if nothing else.

and re the choke mechanism - its probably because the engine is warm and the choke is off that the lever you are worried about seems so slack - that releases the choke plate to fully closed (via the auto choke spring) when you return to a previously run engine for a cold start.

 

[Lou C]

Re: First time dist tune up and carb questions

As far as your dist settings, dwell affects timing so if you change dwell you will change the timing, that's why you set dwell first then the timing. You did set the points with the rubbing block on one of the high points of the dist cam right? You are also supposed to put some cam grease on the dist cam (you can use trailer wheel bearing grease but not too much). Also you can put a drop or two of oil in the dist shaft (there is a foam pad in there) to oil the advance mechanism. For the mechanical advance you need to use an advance timing light. You need to know the total advance spec and at what RPM this is measured. I gave you these #s back in the other post. You will have to run the engine at around 3000 rpm so that's too fast for running on muffs so you should put it in the water. You warm the engine up, attach your tach and timing light. take your timing light and set the total advance # on the dial. Run the engine at the specified RPM....Then point the timing light at the timing marks pull the trigger and it should read zero or TDC.

The carb it sounds like they did not set it up right...I mean if your points were not even opening they did not get the engine set up right for you. The carb does not look like a Quadrajet (that would have been OE if it came with a 4 bbl)...Time to learn about carbs too...I have rebuilt a few carbs in my day but a Rochester Q-Jet is complex enough that I let my mechanic do it for me...just had it done this year...same issue the carb was flooding out and filliing up the throttle bores with gas..

As far as the choke they are supposed to close (theromstatic spring) when the engine is cold, when it starts they should open just a fraction to give the engine enough air to keep running and then as the engine warms up the choke should open up all the way, they are operated by either the heat of the engine (thermo spring on the intake manifold) or an electric heating element...

See there was some advantage to growing up in the 60s and 70s when all our cars had points, condensers, and carbs...if you had a GM high performance car you had a Q-Jet, Fords had the Autolites and Mopars had Carters (thermoquad)...then that mysterious thing called electronic ignition came along (Chrysler) in 72 or so and followed by the Delco HEI in 74-75 and the Ford system. To do the points in our small block Chevys you had to climb on top of the engine to get at em! Cadillacs and Buicks were easy the dist was on the front of the engine. GM had this great distributor, with a little metal window you slid open, you put an allen wrench in there and you could change the dwell (meter hooked up engine running) with the engne running real easy. Ford and ChryCo you still had to do the old way. Ah well that's today's ancient history lesson!

 

[LAC_STS]

Re: First time dist tune up and carb questions

Lac - why ask advice if you are certain you already know the advice is wrong

Come on. thats whay I said

Not saying it doesn't need rebuilt cause I don't know but it's brand new. Only has 22 hours on it and it's bogged since I got it.

I was saying that the carb is new so is there some kind of adjustment we can shoot for before calling it time for a rebuild.


The carb is an Edelbrock 1409. I dont think thats its putting too much fuel through. I was just saying that the jets on the primaries and the little jets under the air butterflies on the secondaries are shooting the proper amount of fuel (at WOT its a bunch) but the big jets on top of the secondaries dont shoot anything.

So I need to find out why the big jets on the secondaries are not shooting any fuel at WOT.

As far as your dist settings, dwell affects timing so if you change dwell you will change the timing, that's why you set dwell first then the timing. You did set the points with the rubbing block on one of the high points of the dist cam right? You are also supposed to put some cam grease on the dist cam (you can use trailer wheel bearing grease but not too much). Also you can put a drop or two of oil in the dist shaft (there is a foam pad in there) to oil the advance mechanism.

Thanks, Yes I knew the dwell would effect timing but I didnt know it would be that much. I did see the old points were nearly closed when they were supposed to be open.

Yes I was checking the gap when the cam was on a high spot. (ie when the cam pushes the points open). And yes I did put some cam grease on it.


So the mechanical advance is under the plate that the points and condenser sit on?


I will look for your other post and then see what the advance is when I go to the boat later.

Thanks so much everyone

 

[a70eliminator]

Re: First time dist tune up and carb questions

Remove the screws holding the braker plate and take it off and you'll see the advance springs and reluctor arm, grab the end of the shaft and advance by hand with a twisting motion and you'll see the workings, there sure could be something amiss with the advance springs, my expereience has been that dwell doesn't effect the timing that much.

 

[libellav15]

Re: First time dist tune up and carb questions

my expereience has been that dwell doesn't effect the timing that much.

they say .001" gap difference equals 1 degree - so if your points are well open (minimal dwell) or hardly opening (huge dwell) the timing difference will certainly be noticeable when gap and subsequent dwell is corrected

 

[LAC_STS]

Re: UPDATE First time dist tune up and carb questions UPDATE

Re: UPDATE First time dist tune up and carb questions UPDATE

OK so I got the points in and gapped and dwell set correctly. (Wasn't so hard after all). Thanks everyone!!!

I set the timing per the manual.

I sprayed carb cleaner in the carb and tried to get all the little places in there I could.

I took it out for a spin and it does start WAY faster and it does run better. I also got an extra 300 or so RPM at WOT!!! But being as the problem with backfiring and not wanting to reach RPM that I was having was intermittent I don't know if the problem is gone yet.

A few days ago I took the boat out, ran great for about 4 hours then just like a switch it started backfiring and running like crap.

Even though I have checked and replaced the fuel filter three times in the past month or so when I got back I checked it and it was full of water.

So I emptied ALL of the fuel from the tank (30 gallons) and by way of the fuel sender hole I cleaned the tank out, checked all of the fittings, checked the vent, and filled it back up with fuel and marine Stabil.

After the doing the fuel but BEFORE I did the dist I did run it for about 30 mins and I did hear it backfire once or twice.

It seems that if I run it then idle then run then idle it sometimes starts the backfiring and running like crap.


The boat has always even when its running good bogged when the secondaries open. I looked in the carb while someone else was driving and I opereated the secondary butterflies. I notcied that the jets on top of the secondary air butterflies were not shooting much if any fuel.

I talked to Edelbrock and they said to check if the air vent opens all the way. they said that if it doesn't open completely vertical that there will not be enough vacuum to make fuel come out of the secondary jets.

I checked this and they do open but only about 80% of the way. I opened them the rest of the way buy hand and more fuel did start coming out of the top jets. It still wasn't as much as the primary big jets shoot but it was more.

Edelbrock said that if it is a problem with the secondary air butterflies not opening when the throttle is at WOT that I can take them off and drill a very small hole in the weight and then re check it. If needed I could drill another one until they open right.

If that is NOT the problem then they said it is possible that the float level is not set right.

Either way I am going to check the fuel pressure again. I'm gonna check the pressure right where the fuel enters the carb. Then I'm gonna check the other pressure/vacuum.


I will also re tune the carb as described in the "How to tune up your engine with points IGN" FAQ.

So far I have everything done except tuning the carb.

After that if my problem still comes back I am at a loss. I have a brand new engine and have checked compression, tuned the dist, checked the plugs, checked the coil, will be tuning the carb, emptied all the fuel and replace with new, checked all fuel fittings, replaced hose going from tank to fuel water sep filter, new fuel water sep filter, cleaned carb with carb cleaner (while on engine).


I dont know what to check if after I clean the carb and pressure test the fuel system it still comes back.