351V6 Engine Question???

[AndrewJoey]

I'm new to working on engines, so I'm sorry in advance if I'm asking stupid questions. My engine seems to backfire ( a little) through the carb when I get the rpms going, like upshifting into 4th or going uphill. It loses power and I have to get it back into 2nd. I rebuilt the carb and it seems to do the same thing.

Once it's warmed up it runs better for sure, but I know I've got an issue somewhere. Is it maybe a distributor issue? Should the idle be fast or slow, I'm wondering if the carb needs an adjustment. At least it runs
Posted via Mobile Device

[cortcomp]

I wonder if you're running a bit lean? Just a thought. One of those gremlins that's tough to chase down for sure. Check with a timing light what your initial timing is, and total timing (maybe distributor adding too much?) and maybe use a spark tester to be sure you're getting good spark?

[66Submarine]

Is it just at high engine speeds, or under load?

To start off, clean or replace the points and set the dwell to spec, then check/set the timing. (Disconnect vacuum advance when you do, also make sure it's working while you're at it.) Make sure the plugs are gapped correctly. Something like .030-.035"; new plugs will be something like .055" for later HEI a lot of times, and with that big of a gap with points the engine will run poorly, or barely run at all. A bad condenser will cause ignition problems ranging from poor starting to not running at all, might try a new one, too. (Always should keep a spare condenser in the truck anyway, IMO) Check the rotor and cap and clean them up or replace them. Coils seem to last forever, so that would be at the end of my list, but could also obviously cause problems.

I like to let the engine warm up to operating temp, lean the idle out until it misses/runs poorly, then richen it up until it runs smoothly again. Another way I have used is to set for peak RPM, then leaning it out for a little RPM drop. The objective for me being to be just rich of running poorly. That's the way I set things up, going for economy.

I don't use a choke, so I set hot idle to about 700RPM. That way, by the time I get to the first stop the engine will be warm enough to idle by itself. Spec idle speed for manual trans should be 450-550RPM or something like that.

Hope this ramble helps

[AndrewJoey]

Originally Posted by cortcomp

I wonder if you're running a bit lean? Just a thought. One of those gremlins that's tough to chase down for sure. Check with a timing light what your initial timing is, and total timing (maybe distributor adding too much?) and maybe use a spark tester to be sure you're getting good spark?

Ok here's a pic of the timing. It's hard to see, but if you zoom in a bit you can see a little oval mark that's just off center maybe a mm or 2 at most. Remember I'm learning as I go so you may have to dumb it down for me. Is it safe to drive when it's popping a little. Only happens when I rev it up too much.

Posted via Mobile Device

[AndrewJoey]

Originally Posted by 66Submarine

Is it just at high engine speeds, or under load?

To start off, clean or replace the points and set the dwell to spec, then check/set the timing. (Disconnect vacuum advance when you do, also make sure it's working while you're at it.) Make sure the plugs are gapped correctly. Something like .030-.035"; new plugs will be something like .055" for later HEI a lot of times, and with that big of a gap with points the engine will run poorly, or barely run at all. A bad condenser will cause ignition problems ranging from poor starting to not running at all, might try a new one, too. (Always should keep a spare condenser in the truck anyway, IMO) Check the rotor and cap and clean them up or replace them. Coils seem to last forever, so that would be at the end of my list, but could also obviously cause problems.

I like to let the engine warm up to operating temp, lean the idle out until it misses/runs poorly, then richen it up until it runs smoothly again. Another way I have used is to set for peak RPM, then leaning it out for a little RPM drop. The objective for me being to be just rich of running poorly. That's the way I set things up, going for economy.

I don't use a choke, so I set hot idle to about 700RPM. That way, by the time I get to the first stop the engine will be warm enough to idle by itself. Spec idle speed for manual trans should be 450-550RPM or something like that.

Hope this ramble helps

Higher engine speeds only.
Totally helps thankyou! I may need to get help from a friend to figure out some of what you said, but I have a place to start now.
Posted via Mobile Device