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Discussion Starter · #1 · (Edited)
My 265 has been driving me nuts this summer. I remember it working quite OK before last winter (if my memory serves me right) Now it seems I can't get it running right no matter what I do. I've read all kinds of threads but found no solution.
The issue is that it jerks (maybe misses?) at low throttle / cruising speed so much that it isn't fun to drive. I've gotten it a bit better but it's still present. And the funny thing is that this problem is quite inconsistent; on a 20 minute drive it varies from a slight problem to intolerable.

What I've found out and done so far:
  • the car starts fine, idles OK and revs OK
  • timing is set as the manual says
  • I ditched the Ignitor kit I had and went back to using points
  • dwell is also set and correct
  • carb (4GC) has been in parts multiple times and should be adjusted as should, just changed primary side nozzle unit because I accidentally broke the old one
  • I've set the idle mixture screws with a vacuum gauge installed in the base of the carb, gauge needle is steady at about 20Hg
  • distributor replaced with a new one
  • new spark plug wires
  • timing chain was replaced when I rebuilt the engine, not a lot of miles on it
  • it popped a lot in the exhaust on engine braking previously but I got rid of it by richening the mixture - still letting off the throttle while cruising causes sound on exhaust that sounds like there's a lot of vacuum (backpressure?) on the exhaust (I'm having hard time describing it)
  • I think the problem might be more present when the engine warms up (maybe?)
  • it misses and "hickups" on mid throttle on park too so the car doesn't have to be moving
  • if I push the throttle "just a hair" from idle while driving it produces a weird sound in the exhaust - hard to describe but it might be like something's blocking the exhaust at the end of it (and there's absolutely no power at this point) - if I push the throttle some more it comes out of this state and accelerates normally
  • sometimes letting of the throttle and coming to idle leaves the rpm a bit higher than should - a quick flick of the pedal makes the rpm come down - I've ignored this but it's weird because all mechanisms seem to move fine when I have the carb on my desk.

I'm totally out of ideas at this point 😵 I've been going back and forth if it's a ignition issue or a carb issue. I've thought of fuel pump going bad but then the problem would show on accelerating. I've thought of valve issues too but I think those would show up on the vacuum gauge (?). Valves were adjusted last summer.
Gas is high octane and I use lead substitute at every fill up. Oh, and the exhaust system is all stock up to about firewall. From there on it's straight with one straight through muffler. I've put the warm-up flap on passenger side so that it doesn't ever close. I've thought of the choke flap too but it shouldn't move while driving (?).
If anyone can make any sense out of this it will be very much appreciated and appraised ✌
 

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Discussion Starter · #4 ·
You know what... After writing this down last night, I woke up in the night and thought "Crap...what if the heat riser has moved". I haven't thought about it after I put it "permanently" open way back..... I had to do a quick check before heading to work and looking at the lever it looked like it would be halfway shut - yikes 😬. I tried to move it but it was pretty much stuck. I'll have to do a better inspection tonight. If it truly has been this way for a while I hope it hasn't caused major damage 🤞
 

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You know what... After writing this down last night, I woke up in the night and thought "Crap...what if the heat riser has moved". I haven't thought about it after I put it "permanently" open way back..... I had to do a quick check before heading to work and looking at the lever it looked like it would be halfway shut - yikes 😬. I tried to move it but it was pretty much stuck. I'll have to do a better inspection tonight. If it truly has been this way for a while I hope it hasn't caused major damage 🤞
Now you get to spend all day at work thinking about fixing it.
 

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Just a total shot in the dark but if you haven't already I'd swap the ignition coil for either a new or known good coil.I just went through this on my buddies 55 after building a new engine for the car which has a Petronic flame thrower distributor with the original coil which ohm correctly the car would act up feeling like a loss of power I replaced the coil & no issues since.Again only a guess from reading what you have already done.Also have you checked your fuel pressure with a gauge?
 

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Discussion Starter · #7 ·
Just a total shot in the dark but if you haven't already I'd swap the ignition coil for either a new or known good coil.I just went through this on my buddies 55 after building a new engine for the car which has a Petronic flame thrower distributor with the original coil which ohm correctly the car would act up feeling like a loss of power I replaced the coil & no issues since.Again only a guess from reading what you have already done.Also have you checked your fuel pressure with a gauge?
Thanks for the tip! The coil is new though. I forgot to mention it.
Don't know about fuel pressure because sadly I don't have a gauge for that.
 

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Thanks for the tip! The coil is new though. I forgot to mention it.
Don't know about fuel pressure because sadly I don't have a gauge for that.

Here's an example of a fuel pressure gauge, from a quick web search. You may be able to find one within your budget, .Heres a link for this one from e bay (59$). SNAP ON TOOLS Vacuum / Fuel Pump Pressure Small 3" and Large 4.5" Gauges + extra | eBay
Also- I second replacing your condenser , its a cheap way to eliminate that from your list of things to check, I had this problem in an old motorcycle ( eating condensers) .
Gauge Measuring instrument Font Metal Fashion accessory
 

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Discussion Starter · #9 ·
Thanks. I'd have to fiddle with the fuel lines a bit. I have a stock style hard line from pump to the filter. Can't really fit anything in between :)
 

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Have you pulled the plugs for a visual? You stated you richened the carb to get rid of the pop on decel in the exhaust. My question is why you're running premium in I am assuming a stock 265. That car should run well on 87 octane. Adding lead substitute tends to be with my experience a guess on proper mixture. What plugs are you running and what gap? As far as exhaust you state stock to the firewall but what size are you running the rest of the way? Anything more than 2" on single exhaust, especially with a straight through muffler is not enough back pressure and decreases performance and will definitely sound funny on deceleration and pop and gurgle like crazy. Did you regap the plugs after going back to points as they should have been gapped wider with the previous igniter. Check compression when you examine the plugs.
 

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From you initial post, and these bullet points:

  • carb (4GC) has been in parts multiple times and should be adjusted as should, just changed primary side nozzle unit because I accidentally broke the old one
  • it popped a lot in the exhaust on engine braking previously but I got rid of it by richening the mixture - still letting off the throttle while cruising causes sound on exhaust that sounds like there's a lot of vacuum (backpressure?) on the exhaust (I'm having hard time describing it)
  • I think the problem might be more present when the engine warms up (maybe?)
  • it misses and "hickups" on mid throttle on park too so the car doesn't have to be moving
  • if I push the throttle "just a hair" from idle while driving it produces a weird sound in the exhaust - hard to describe but it might be like something's blocking the exhaust at the end of it (and there's absolutely no power at this point) - if I push the throttle some more it comes out of this state and accelerates normally
  • sometimes letting of the throttle and coming to idle leaves the rpm a bit higher than should - a quick flick of the pedal makes the rpm come down - I've ignored this but it's weird because all mechanisms seem to move fine when I have the carb on my desk.
It certainly sounds like a Carburetor Issue.
How confident are you that the carb is in perfect condition? Are you an experienced rebuilder?
I'd highly suspect that the carb needs professional rebuilding.

Is the Choke system working the way it should?

On a different subject - you said you ditched the Pertronix System and went back to a points system. Do you still run the Pertronix High Performance Coil? Try swapping for a stock coil.

Also - why are you using Premium Fuel in a 265? Is it High Compression? If not, 87 or 89 Octane should be fine.
 

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Alot of good ideas in this thread. I thought of one more ,,maybe very obvious. I have been burned by “new” parts several times that were bad (the new part did not work even after several replacements). Or I assumed new was good and wrongly moved on to other items. So If possible for the problematic intermittent problems, I suggest temporarily using fuel system parts or ignition parts from a “good running similar engine” to identify the problem, then buy the new part that hopefully works.
 

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Discussion Starter · #14 ·
Checked the heat riser last night. It wasn't the issue. Also went through my stuff and found a new condenser and a new coil. Will try them on tonight.
Answering the questions above:
  • The exhaust is the stock 2" size
  • I didn't use hi-performance coil with the Ignitor kit because manual said the stock will be fine
  • I haven't re-gapped the plugs - good point! Will do that too (also going to get a spare set of new ones just in case)
  • Our european octane ratings are a bit different than in the US. Our 98 octane (called it "premium" previously) compares to about 93 octane on your rating and our 95 octane compares to about 90 octane on your rating. Our 98 octane contains max. 5% of ethanol and 95 octane contains max.10% ethanol. Out of curiosity I tried running with the 95 octane but it made the problems worse.
  • The choke system is hooked up but I can't tell for sure if it's truly working or not. I've always seen the flap being open though (haven't used the car in cold weather).
  • I'm not a carb specialist by any means. Just been trying to follow manuals and pro-tips from this forum. There are not much carb rebuilders around here so this has been easier so far.
 

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Discussion Starter · #16 ·
Are you running through the resistor to your coil? By pass the resistor if Yes.
Yes I am. It's a stock resistor setup. Why bypass it?

EDIT: Got a new underhood wiring set from AAW couple of weeks ago and the set includes those wires too. Haven't installed it yet.
 

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  • I think the problem might be more present when the engine warms up (maybe?)
  • it misses and "hickups" on mid throttle on park too so the car doesn't have to be moving
  • if I push the throttle "just a hair" from idle while driving it produces a weird sound in the exhaust - hard to describe but it might be like something's blocking the exhaust at the end of it (and there's absolutely no power at this point) - if I push the throttle some more it comes out of this state and accelerates normally
  • sometimes letting of the throttle and coming to idle leaves the rpm a bit higher than should - a quick flick of the pedal makes the rpm come down - I've ignored this but it's weird because all mechanisms seem to move fine when I have the carb on my desk.
I doubt if it is the ignition if things change with throttle movement (but stranger things have happened)

If it sometimes idles too fast, that tells me that the fast idle/choke adjustment is off or it is sticking. Possibly leaving the choke part way on even after it's warmed up. Try to simulate the fast idle while parked then remove the air filter and take a peek at the choke.
 
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