I have been working on the old girl for a while and got the floor, done new carpet, headliner etc. Did a lot to the engine and she purrs at idle. Took her for a test drive and omg is this thing a dog. Barely got up to 55. From 1/2 to full throttle makes no difference. 225 slant 6 Im not expecting a rocket ship but freeway speeds would be nice lol. It took parts from 3 carbs to make one so maybe that is the issue. I set the timing, adjusted the valves, has new plugs, new coil and pertronix ignition. Where should I start? Doesnt smoke compression wasnt to bad. Hmmm
Where is my power?
- Thread starter frige
- Start date
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Are you sure the exhaust system is clear? I had a bad CAT on a v8 van once and I could drive it on the interstate at any speed but it took forever to get up to speed?
MDchanic
Connoisseur d'Junque
Is your throttle opening all the way?
I had a '67 with a 170 once (same car, really), and while it'd take a little while to get there, it'd cruise at 80 on the interstate without a problem
- Eric
I had a '67 with a 170 once (same car, really), and while it'd take a little while to get there, it'd cruise at 80 on the interstate without a problem
- Eric
I had a good engine I pulled out of a car and put in another. It didn't have as much power. I thought it was because it was a heavier car. Turns out the muffler had come apart inside and was restricting the exhaust, it ran good again with new mufflers.
throttle
kickdown linkage
clogged exhaust ....heat riser stuck
hook up a vac gage if vac drops at haft throttle exhaust is blocked
or valve timing chain skipped a tooth
that thing should do 90ish
kickdown linkage
clogged exhaust ....heat riser stuck
hook up a vac gage if vac drops at haft throttle exhaust is blocked
or valve timing chain skipped a tooth
that thing should do 90ish
And after all the above, actually check if the timing is advancing. I've had engines with not only a stuck mechanical advance, but either a ruptured vacuum advance can, or bad / incorrect hose connections.
Get a looser converter to get the engine into its torque range. You will not believe the acceleration improvement with just a converter change. All 340's came from the factory with 3000 stall converters.
While holding your brakes tight in "drive position" put the accelerator pedal to the floor and see what RPM your engine goes to while holding the car back. If its less then 3000 it will be a pooch.
Many always overlook the converter and it is the major performance gain. That would be the first thing to check.
While holding your brakes tight in "drive position" put the accelerator pedal to the floor and see what RPM your engine goes to while holding the car back. If its less then 3000 it will be a pooch.
Many always overlook the converter and it is the major performance gain. That would be the first thing to check.
Like said, check the heat riser to be sure it is not stuck and open> Been there before decades ago.
Compression??
Compression??
You did clean the tank and check that the fuel pick up sender is not clogged? Blew air thru the metal fuel line that runs from back at tank top front?
You are getting full throttle with carb linkage?
Otherwise, maybe a known good carb>?
You are getting full throttle with carb linkage?
Otherwise, maybe a known good carb>?
slantsixdan
=..=
Check for a slack timing chain as described here. Also, verify that your timing mark is accurate; the outer ring of the crank pulley can slip relative to the inner hub, throwing the timing mark off so when you set the ignition timing it's not where it looks like it is.
Beyond that: Tune-up parts and technique suggestions in this post. Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download.
Beyond that: if this car has an automatic transmission, there could be problems with it (maybe short-shifting and dumping you into 3rd way too early?) or with you your torque converter.
Beyond that: Tune-up parts and technique suggestions in this post. Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download.
Beyond that: if this car has an automatic transmission, there could be problems with it (maybe short-shifting and dumping you into 3rd way too early?) or with you your torque converter.
The mechanical advance in these distributors is bad about gumming up and rusting up.
slantsixdan
=..=
Oh, hey, also check to make sure your throttle is opening all the way. Have a helper floor the accelerator while you're underhood watching. If any part of the linkage (including/especially the trans kickdown linkage, on an automatic car) hits anything in the middle of its travel, then the throttle can be blocked from opening all the way. That'll put a serious crimp in performance; meanwhile, inside the car, it feels like the acclerator's all the way down.
slantsixdan
=..=
(in case not obvious: make this check with the engine off)
If you timed it to factory specs, bump it to about 8° BTDC as a start. You might look into having the distributor curve reworked.
If you haven't done it yet, do a valve adjustment.
And SSD knows what he's talking about.
****
This has no bearing on you, but my 64 225 Valiant has no trouble at all keeping up with traffic. I go to Carlisle every year on the PA turnpike and have no problem passing cars on the hilly sections in high gear. (4 speed) Also, it'll do a Roadkill style one tire burnout w/o power braking if I want it to but that's kid stuff.
If you haven't done it yet, do a valve adjustment.
And SSD knows what he's talking about.
****
This has no bearing on you, but my 64 225 Valiant has no trouble at all keeping up with traffic. I go to Carlisle every year on the PA turnpike and have no problem passing cars on the hilly sections in high gear. (4 speed) Also, it'll do a Roadkill style one tire burnout w/o power braking if I want it to but that's kid stuff.
I worked on it this weekend. I checked the timing and it was right on spec and the advance is working properly. One thing I noticed is man the opening to the air cleaner is tiny. 1/8 inch clearance around the inside. I am used to much larger openings.
It has a pcv valve piped off of the base of the carburetor to the rear of the valve cover. Also there was a breather cap installed on the oil fill tube on front of the valve cover. It was causing a large vacuum leak. I put my palm over it and it pulled a good vacuum against my hand so I plugged the tube off. I ran the valves already and they were close although a bit tight. I ordered a new muffler and it should come in today.
It has a pcv valve piped off of the base of the carburetor to the rear of the valve cover. Also there was a breather cap installed on the oil fill tube on front of the valve cover. It was causing a large vacuum leak. I put my palm over it and it pulled a good vacuum against my hand so I plugged the tube off. I ran the valves already and they were close although a bit tight. I ordered a new muffler and it should come in today.
TT5.9mag
Two atmospheres are better than one
Plugging off the valve cover was a bad idea. Put a correct working PCV system back on it. Saying the “timing was in spec” isn’t good enough. What’s the timing at? At idle? And advanced at what rpm?
MDchanic
Connoisseur d'Junque
That's a normal air cleaner. Do the math regarding a 1/8" linear opening as long as that circumference and see what you come up with.
The PCV is designed to suck air through the crankcase.
You plugged the hole, so now it won't.
A bad PCV will give you idle and off-idle problems, but is unlikely to cause this, as it just adds a bit more air once you're running. The official test is to shake the PCV, and if it rattles, it's fine.
I wouldn't trust that. Mine rattled and it messed up the idle, even after I cleaned it, so I replaced it.
This is where we go down the PCV replacement rabbit hole. There seems to be validity to the argument that anything other than original factory replacements, or maybe contemporary aftermarket replacements (from the early '60s) won't work right.
Replacement with a later MoPar (and only MoPar) appears to be the only reasonable accessible solution.
I say this speaking from limited personal experience, and credible recommendations I've read, and not as someone who has seen hundreds of these.
You need to buy a MoPar 05175351AA PCV and a Dorman 42064 PCV Grommet, and use the grommet in place of the nut to hold the newer valve and retaining spring in your older PCV cap.
See here.
– Eric
The PCV is designed to suck air through the crankcase.
You plugged the hole, so now it won't.
A bad PCV will give you idle and off-idle problems, but is unlikely to cause this, as it just adds a bit more air once you're running. The official test is to shake the PCV, and if it rattles, it's fine.
I wouldn't trust that. Mine rattled and it messed up the idle, even after I cleaned it, so I replaced it.
This is where we go down the PCV replacement rabbit hole. There seems to be validity to the argument that anything other than original factory replacements, or maybe contemporary aftermarket replacements (from the early '60s) won't work right.
Replacement with a later MoPar (and only MoPar) appears to be the only reasonable accessible solution.
I say this speaking from limited personal experience, and credible recommendations I've read, and not as someone who has seen hundreds of these.
You need to buy a MoPar 05175351AA PCV and a Dorman 42064 PCV Grommet, and use the grommet in place of the nut to hold the newer valve and retaining spring in your older PCV cap.
See here.
– Eric
Ok I understand about the pcv. Coming from a racing background we like to pull a vacuum on the crankcase as it give the engine more power. My small block has a huge vacuum pump and pulls 18 inches of vacuum. But we are talking about a full race engine. One thing for sure the engine must be healthy if the pcv will pull a vacuum. The muffler came in today so I will see if that is the issue.
slantsixdan
=..=
In the first place, that gap is larger than 1/8". In the second place, see the math worked out here (that was with the larger 1969 air cleaner, but you can plug in the numbers for your '63-'67 air cleaner and come up with different numbers showing the same result: there is plenty of area for plenty of air to enter). In the third place, even if you don't believe in math, millions of Slant-6 engines ran and run perfectly peppy-well with that air cleaner. This is not even slightly causing any of your problem.
That's correct.
That was correct until you stopped it up. That wasn't a large vacuum leak, that was your crankcase ventilation working the way it's supposed to, to keep the engine clean inside and out. Put it back the way it was, before you pull a vacuum in your crankcase and make large and messy problems for yourself.
Honestly, dude, you have been given, in this thread, a good list of candidate causes for your problem (some of which cost $0.00 to look into). Making up new imaginary problems that don't actually exist isn't going to get you where you want to go. When you run into a question like "Huh, why is the breather cap set up this way?", or "Wow, why is this air cleaner so different to the ones I'm used to?", it's more productive to ask people who can give you the right answer than to just decide a blind, wild guess is the same thing as the truth.
As soon as you can, get the three books listed in this thread.
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I am listening and going through the issues. One at a time. I really do appriciate the help as few mechanics understand these old engines anymore. I got the new muffler in and will try to get it installed today. The throttle goes wide open I had a friend check. The timing was 7 degrees at idle with the vacuum hose removed and 32 degrees at full advance. I will replace the breather and go for a ride.
Mopar didn't put a 3k stall converter behind any 340 engine. 2500 at best as they rolled off the showroom
Carry on
For the OP tune it for what the engine wants, not what the "book" says if you want it to perform its best.
Carry on
For the OP tune it for what the engine wants, not what the "book" says if you want it to perform its best.
TT5.9mag
Two atmospheres are better than one
Ok we’re getting somewhere. What idle speed? And what rpm does it fully advance? Sounds like ignition timing can be marked off the list as a “probable” cause at this point.
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