I've got the backfire through the carb situation taken care of it seems. I believe it was a carburetor gasket with a vacuum leak. I installed a new gasket today and I was able to rev up the engine with no more backfiring. It starts fairly easily seems to have reasonable power but I just drove it around the driveway no more than 20mph since it's not tagged yet. Sitting there idling after it warms up for about 5 mins you can feel a slight miss every once and awhile. I've got everything adjusted and tuned. It's got new plugs, wires, cap, rotor, coil, air filter. The distributor/points/condenser, carburetor, fuel filter are all a year or a little more older. I don't know if it's a choke problem, dirty fuel filter, or ignition problem. I don't even know if it is a misfire but it seems like it's got a little very slight shake on idle. But it's almost a 50 year old engine, no telling if it's ever been rebuilt, and how long it was sitting up before I revived it a couple years ago. Is there any kind of top end cleaner that I can safely add to help free up deposits on the valves? I didn't want to dump any seafoam down the carb. Where do you find a new choke thermostat for this 1bbl holley? I think a lot of issues I'm having with it warming up is with the choke thermostat.
What will cause slight miss idling on a 65 170?
- Thread starter wh23g3g
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805moparkid
Slant and AFX Guy
i would guess carb, i have the same thing going with my swinger
get the engine up to temp, then rev the engine to about 3000 rpm and pour a small amounts of water down the carb. its gonna stumble and then clean out, pour some more. I usually do this with about a half a glass of water, any carbon build up will be shocked by the temp change from the water (engine hot carbon build up and tap water) caused the carbon to break off just about everything. Afterwords go run the car hard to clean it all out.
get the engine up to temp, then rev the engine to about 3000 rpm and pour a small amounts of water down the carb. its gonna stumble and then clean out, pour some more. I usually do this with about a half a glass of water, any carbon build up will be shocked by the temp change from the water (engine hot carbon build up and tap water) caused the carbon to break off just about everything. Afterwords go run the car hard to clean it all out.
nm9stheham
Well-Known Member
Take the choke spring assembly out of the choke well on the intake. Make sure it is clean. You will see a small nut on the sit and a disc with markings L and R (lean and rich). You can loosen the nut and move the disc towards R to make the choek come on harder or to L to have less choke.
A slight miss once on a while is not something to be overly concerned with, IMO, especially with old points and such. It could be a tiny vaccum leak, a valve sticking a bit, loose valve guides (this is actually pretty likely with high mileage and age), or one erratic spark once in a while. Get it tagged and drive it to see if gets any worse.
A slight miss once on a while is not something to be overly concerned with, IMO, especially with old points and such. It could be a tiny vaccum leak, a valve sticking a bit, loose valve guides (this is actually pretty likely with high mileage and age), or one erratic spark once in a while. Get it tagged and drive it to see if gets any worse.
KickDown
Just a Brit in Germany
Get the engine up to operating temperature, shut off & check your valve lash. By your discription I would say they are all a little tight.
Ok that's one thing I haven't touched on, is adjusting the valves. I have no idea of the true mileage of this engine or how long it had been in the car. It's not the original for sure it's not even the right size. It should be a 225 and someone swapped it with a 1966 170 probably not realizing the difference until after they put it in and drove it! So I might be a little slow in understanding how to mark the crank damper in order to do the valve adjustment. The only valve adjustment I've ever done was on a 1976 Datsun B210 with success. But how do I go about marking the damper into 3 120 degree marks? What if I'm off a little, that would throw all the adjustments out? Do I get number 1 on TDC compression, mark it and then from that point use a protractor to go 120 degrees? You know I can estimate 90 degrees and 180 and even 145, but 120? That's what my instructions are telling me to do. Luckily it's easy to get to because there's no power steering or a/c and no fan shroud.
KickDown
Just a Brit in Germany
No need to go that complicated. This has always worked for me.
OK so the piston pairs on your /6 are 1+6, 2+5, & 3+4. Crank the engine by hand until the valves on #1 cylinder are overlapping. (i.e. exh. Valve just closing & Inlet valve just opening) Adjust the valve lash on both valves of cyl #6. Crank the engine once again by hand until the valves on #5 cyl are overlapping & adjust the lash on both valves of cyl#2. Crank again by hand until the valves on cyl. # 3 are overlapping & adjust the lash on both valves of cyl. # 4. Follow this sequence in the firing order (153624) & you wont end up hand cranking the engine a thousand times. Take your time and set the lash accurately.
Like I said it has always worked for me & the way I was taught many years ago. ( Just after ww1 if I remember correctly):thumblef:
OK so the piston pairs on your /6 are 1+6, 2+5, & 3+4. Crank the engine by hand until the valves on #1 cylinder are overlapping. (i.e. exh. Valve just closing & Inlet valve just opening) Adjust the valve lash on both valves of cyl #6. Crank the engine once again by hand until the valves on #5 cyl are overlapping & adjust the lash on both valves of cyl#2. Crank again by hand until the valves on cyl. # 3 are overlapping & adjust the lash on both valves of cyl. # 4. Follow this sequence in the firing order (153624) & you wont end up hand cranking the engine a thousand times. Take your time and set the lash accurately.
Like I said it has always worked for me & the way I was taught many years ago. ( Just after ww1 if I remember correctly):thumblef:
RustyPlymouth
Well-Known Member
or you could just do it with the motor up to temp and running. thats what i always do. that way you dont have to worry about getting it on the right stroke. also you see instant results.
KickDown
Just a Brit in Germany
Yeah. I've heard of guys setting the lash with the engine running. Cleaning up the engine bay from all the sprayed oil is a PITA, and it beats the crap out of a good set of feeler gauges. I like to use mine more than once.
nm9stheham
Well-Known Member
Adjusting the valves running does not splash oil out at idle on a slant 6, and does not beat up feeler gages. And unless someone adjsuted the valves worng, they are not likely to be tight; they will wear towards loose.
You don't need to be exactly on the 120 degree marks to do it that way, just close. It's worthwhile to do this with an unknown engine; mine must never have had been adjusted when I got it!
You don't need to be exactly on the 120 degree marks to do it that way, just close. It's worthwhile to do this with an unknown engine; mine must never have had been adjusted when I got it!
moe7404
moe7404
my dad had a saying. "check the cheapest and easiest things first." and / or "check the last thing worked on."
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