Slant 6 power issues

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SpriceyStuff

SpriceyStuff

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Hey guys. I’m coming to you again to ask for your wisdom on slant six tuning. I’m having power issues. Before, the car would push itself at idle when I put it in gear. Now i have to give her quite a bit of gas to get her to move, but too much throttle at once and she chokes. And when I am cruising down the road, it doesn’t sound like it runs super great. It kinda stutters just a tad. If I adjust the timing at all in either direction it gets worse, so I know it’s not that. I’ve messed with the idle screw. It runs fine at idle, but why doesn’t it make any power anymore? Could it be purely due to the gas as my dad suggests? There’s a little bit of old gas in the tank mixed into all the new gas I put in. Is that the problem?
 
this happen over time or suddenly? Something changed out?

I'm assuming this is in an old car with no cat converters etc?
You could take of the fuel line inlet to the fuel pump, run a line into a gas can of clean gas and that will answer the gas question for you.

You might have a vacuum leak. you have brake booster?
 
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crj1968 said:
this happen over time or suddenly? Something changed out?

I'm assuming this is in an old car with no cat converters etc?
You could take of the fuel line inlet to the fuel pump, run a line into a gas can of clean gas and that will answer the gas question for you.

You might have a vacuum leak. you have brake booster?
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No I don’t have power brakes. I probably have plenty of vacuum ports to plug on the carb tho. It’s a 74 but I’ve disconnected all the EGR stuff. It happened after I replaced the oil pump gasket. Had to pull the distributor to get to it without pulling the motor out. I’ve got it back in time though. If I adjust timing either direction it runs worse
 
Could have two [ or more problems ].
Runs fine at idle but no longer creeps in gear? Maybe brakes are binding.
How long has it been since the carb was serviced/rebuilt?
 
Bewy said:
Could have two [ or more problems ].
Runs fine at idle but no longer creeps in gear? Maybe brakes are binding.
How long has it been since the carb was serviced/rebuilt?
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Too long. Gaskets leak. My mom bought the car when I was 3 and a half or so and as far as I know, that carburetor has never been serviced
 
SpriceyStuff said:
No I don’t have power brakes. I probably have plenty of vacuum ports to plug on the carb tho. It’s a 74 but I’ve disconnected all the EGR stuff. It happened after I replaced the oil pump gasket. Had to pull the distributor to get to it without pulling the motor out. I’ve got it back in time though. If I adjust timing either direction it runs worse
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Unlikely you have the timing correct. Do you have a timing light? Doesn't sound like it. I'd highly recommend getting one.
 
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The distributor also has two adjustments on it one on the bottom on the housing and another on the block. You miht have put it back in one tooth off also.
 
Yeah I had to play with that 2nd adjustment on the distributor housing, trying to dial in "static" timing on a fresh 225 so it fires up as easy as possible when I get the radiator back from the radiator shop. Still have to get the torque converter bolted up, the super 6 carb linkage, alternator on, and a few other things
 
SpriceyStuff said:
If I adjust the timing at all in either direction it gets worse, so I know it’s not that. I’ve messed with the idle screw. It runs fine at idle, but why doesn’t it make any power anymore?
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I believe you may have multiple problems; related to retarded idle-timing. But it could just as easily have been overly-advanced before. So then, you gotta start with properly setting the timings.
 
It sounds like you got the distributor back in a tooth off. Remove #1 plug. Disable the ignition. Have someone bump the engine until you can feel compression push your finger out of the #1 hole. Look at the balancer and find the hash mark on the balancer. Now, turn the engine by hand clockwise and bring the hash mark up until it aligns with zero on the timing mark. Finally, remove the distributor cap and see WHERE the rotor is pointing. It should be at about the 5 o'clock position, pointing toward #1. If not, remove the distributor and install it correctly. In case you get the wires off, firing order is 1, 5, 3, 6, 2, 4 going clockwise, starting with #1 in about the 5 o'clock position.
 
Yes I have a timing light and I used it. And like I said before, if I adjust the timing at all from where it is, in either direction, it stops running good, so I don’t see how it’s “unlikely” that I have the timing wrong. And I’ve tried pointing the rotor at cyl 1 when the engine was at TDC but it still didn’t want to run until I advanced it.
 
Everything was fine until you pulled and re-installed the distributor. No other changes, wiring etc?
 
crj1968 said:
Everything was fine until you pulled and re-installed the distributor. No other changes, wiring etc?
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Well to a degree. That’s the odd thing. It did this same thing when I first drove it home. When I went to move it a little bit a couple days later was when it started going on it’s own power. I hadn’t done anything to it, I just needed to move it so I had some room to work on it and clean up oil spills. That’s why I’m wondering if it could be just the gas or if it’s a carb issue. I know my car needs a rebuild but I would think once you open the throttle up it should go pretty good. Even with a bad accelerator pump it should go good as long as you open it up slowly
 
barbee6043 said:
Lots of slack in timing chain??
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I don’t know. I haven’t gone into this motor at all. It’s a 77, that’s all I know about it. Bought it and the transmission off some crackhead in Spokane for $300. He told me it was out of his 72 Swinger but I knew looking at it that it was at least 2 years newer than that. It’s whatever. I wanted a late model one anyways for performance purposes. I’m planning a total overhaul on it but it’s gonna cost me nigh on 5 grand so it’ll take a while to get there
 
SpriceyStuff said:
Yes I have a timing light and I used it. And like I said before, if I adjust the timing at all from where it is, in either direction, it stops running good, so I don’t see how it’s “unlikely” that I have the timing wrong. And I’ve tried pointing the rotor at cyl 1 when the engine was at TDC but it still didn’t want to run until I advanced it.
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Timing adjustment when the distributor is in correctly has a HUGE range of distributor movement where the engine will run "pretty dang good". I would estimate in degrees of distributor rotation "around" 30 degrees of movement and the engine will continue to run. At least idle decently. Your description describes a classic case of having the distributor one tooth off. You've had the advantage of a cumulative experience well of over 150 years combined. Several people have advised you to double check. It costs nothing. It's very easy to do and yet you refuse and fight at every turn.

SOMETHING is WRONG. Unless you double check everything, one step at a time, you may not find it and get frustrated and just give up. I've helped here enough. Have fun.
 
RustyRatRod said:
Timing adjustment when the distributor is in correctly has a HUGE range of distributor movement where the engine will run "pretty dang good".
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Yeah you can run Ok in weird situations- I bought a new distributor once and dropped it in and was actually running better but something was still weird. Eventually noticed the reluctor in the distributor was for a V8 and this was on a slant !
 
5 grand to rebuild a slant 6? That's with who doing the job? And with them doing the pull and install, or you? I did my own, had to farm out the machine work, I'd have to go back and do some figuring, but I know I'm not into mine for over about $1500-1700 with about 1/2 of that to the machine shop. And that counts much of the duplicate and triplicate parts I ended up with, along the way.

Look on eBay. There's been a place in Texas ("MABBCO") I believe? Selling complete long blocks no core needed for $1700 ish and short blocks around $1200-ish completely remanufactured ready to go. No core needed. At $5g's, you'd be money ahead to start there at that price. Unless you are building something exotic.
 
volaredon said:
5 grand to rebuild a slant 6? That's with who doing the job? And with them doing the pull and install, or you? I did my own, had to farm out the machine work, I'd have to go back and do some figuring, but I know I'm not into mine for over about $1500-1700 with about 1/2 of that to the machine shop. And that counts much of the duplicate and triplicate parts I ended up with, along the way.

Look on eBay. There's been a place in Texas ("MABBCO") I believe? Selling complete long blocks no core needed for $1700 ish and short blocks around $1200-ish completely remanufactured ready to go. No core needed. At $5g's, you'd be money ahead to start there at that price. Unless you are building something exotic.
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I’m building a performance engine. Triple side drafts that don’t fit stock exhaust so I’d have to buy a set of headers for it that will fit, that’s nearly $800 cause they’re from Australia, along with the inlet manifold for the carbs. Aluminum rockers and rocker shaft is like $1,400. New flat top pistons. I’m gonna see if I can put an older model closed chamber head on it to raise compression. Might get an aluminum valve cover, but with how expensive those are for the slant, i may decide against it. Not sure yet. I also am going to go through and replace every gasket and seal on the whole thing and paint it all up nice since I eventually want it to be a show car
 
volaredon said:
5 grand to rebuild a slant 6? That's with who doing the job? And with them doing the pull and install, or you? I did my own, had to farm out the machine work, I'd have to go back and do some figuring, but I know I'm not into mine for over about $1500-1700 with about 1/2 of that to the machine shop. And that counts much of the duplicate and triplicate parts I ended up with, along the way.

Look on eBay. There's been a place in Texas ("MABBCO") I believe? Selling complete long blocks no core needed for $1700 ish and short blocks around $1200-ish completely remanufactured ready to go. No core needed. At $5g's, you'd be money ahead to start there at that price. Unless you are building something exotic.
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You may consider it exotic. I don’t really know where that line is. It’s just a performance engine to me but I guess it’s far enough away from stock to be considered “exotic.” This is the build I’m going for right here. You can find it on YouTube. If you look up “performance slant six” it’s like the first thing that comes up. Wild Slant Six by Glenn Everitt - Master of Machines
 
If a slant six won't run at TDC, then something is wrong. You probably aren't really at TDC when you think you are. Find the actual TDC instead of just lining up the harmonic balancer and you'll probably find out that you're off by quite a bit.
 
SpriceyStuff said:
Had to pull the distributor to get to it without pulling the motor out. I’ve got it back in time though. If I adjust timing either direction it runs worse
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As already mentioned, if it was running ok before you removed, then reinstalled the distributor, it sounds like you need to verify the position.
 
ESP47 said:
If a slant six won't run at TDC, then something is wrong. You probably aren't really at TDC when you think you are. Find the actual TDC instead of just lining up the harmonic balancer and you'll probably find out that you're off by quite a bit.
Click to expand...
I know what TDC is. Intake and exhaust are were both closed on cyl 1 when I put the distributor in. It tried to idle for a few seconds and died. I advanced it literally as little as it pull let me. And now it is where it is. It runs. It idles and revs fine in Park but in gear it’s just, meh. It runs fine, but it just feels gutless. It may also be worth noting that it seems to do better in reverse than in drive
 
Spricey,
You will loooooove the Webers. Throttle response that can only be dreamed of.....
Couple of tips.

- from Redline in Hollywood, get some Viton needles & seats. Ws normally come with steel n/seats & are not as reliable for street use.
- Ws are veeeeeeeeery sensitive to fuel pressure, 4 psi max. Use the Carter 4070 elec fuel pump, probably also get from RD.
- some W intakes do not allow for PCV or vac for a brake booster.
- contrary to popular belief, Ws are very reliable when set up as above.
 
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