tkheld

1967 Cutlass Supreme 330 with automatic trans. I have replaced the coil, distributor rotor and cap, spark plugs, points and condenser, spark plug wires, all vacuum hoses, and rebuilt the carburetor.

On start up, when engine is cool, it idles just fine. After @ 40 minutes of driving (engine hot), engine randomly misses and stumbles at idle in gear. No problems in park, only in gear.

Looking for some trouble shooting advice.

Thanks,
Tim

cjsdad

What kind of spark plugs did you use? I once had a SBC that ran rough when I bought it. First tune up was the same as yours, cap, points, condenser, rotor, plugs, wires, air cleaner. Second tune up included carb, intake manifold, HEI distributor, and new wires again. Third tune up included heads and camshaft. It still ran rough. I was literally sitting on my living room floor mumbling to myself when my loving wife asked me if I had replaced the plugs. That was in the first tune up I said. She suggested I do it again, they're cheap right! I had used standard AC Delco plugs first so after all of the upgrades I installed AC Rapid Fire plugs and it ran great, smokin' great! Ever since that I use the very best spark plugs I can for each engine I work on.

M-14

Try adjusting the idle mixture screws a little.
Make sure the distributor shaft isn't sloppy.

pmathews

Maybe it's your idle rpm? When it's cold, it will run at a higher rpm on the fast idle cam. Once it has heated up, it will use the normal idle setting. When it's warm, mine idles at 700 in neutral, 600 in gear (auto trans). During fast idle (when it's cold), it runs about 900 rpm (in gear) for about a minute.

If that doesn't help, X2 on the idle mixture screws.

droldsmorland

Ill assume your running a QJet carb???
Agreed with the plug change...but first how do the current plugs read? Please read them and post your findings.
What is the point gap(or dwell setting in degrees)? Did you buy a high quality set of points? They could be bouncing. Check to insure the wire leading from the points through the dist base isnt rubbing on a bare spot from a breach in the insulation causing random grounding. Also rotate the breaker plate to see if the vac advance is pinching said wire as well. Ohm the wire while moving it around. They are known to break internally from 40+ years of heat and movement from the vac can.

Whats your timing set at? Did you inspect the centrifugal weights and springs?

If the ignition systems up to snuff and all settings are correct then Id lean towards a fuel related problem. Your hi(er) RPM stumble would/could indicate fuel starvation(or point ground out) but fuel starvation is not generally random. Check the pump to carb PSI. Check/change the fuel filter. Whens the last time you had the tank down to inspect the sock and crud load in the tank? How are the soft lines in the fuel line. Could be sucking air due to a pin hole? Look for wet spots on the lines.
Other problems could be heat soak related but lets get this simple stuff checked before moving to the more complex stuff.

tkheld

2BBL carb - rebuilt by Sparky. Points, cap, rotor, coil, plugs, wires all new. New fuel pump and line from pump to carb. Tune-up in accordance with specs in chassis service manual. Points are "Standard Blue Streak" - is there a better brand? All these components have less than 300 miles on them.

Engine runs fine when cold at idle in gear and park. When hot, runs fine at idle in park and while driving. Only randomly stumbles when hot and in gear at idle.

Did not inspect the weights and springs but I am not sure what to check - please explain what I should be looking for.

So things to inspect this weekend are:
Re-verify tune-up settings - point dwell setting, timing, spark plugs - condition and gap, etc
Wire leading from points through dist base for random grounding
Soft fuel lines for wet or soft spots
New fuel pump psi
Fuel tank sender sock

Thanks for the troubleshooting advice. Will post my findings.

droldsmorland

The centrifugal weights should move freely. They are located under the rotor. They need a dab of grease under them...just a very small dab. Take the mechanism apart and clean and grease as needed. If the weights are stuck open or the springs are shot it could run rough at idle not at high RPM as that's when they are supposed to be open.
Could have a bad plug breaking down under heat. Other items can break down when hot verses not such as a coil, condenser etc. Dont rule out a bad plug wire. New items out of the box can be bad. Especially with today's chineasium crap.
Blue Streak should make a Corvette spec point set. This point set has a stronger spring which helps reduce point bounce at higher RPMs. I doubt your 2bbl 330 suffers from high RPM bounce but with the crap points produced today the vette spec points may be equal to what a regular set was back in 67. The stronger spring will wear the bump block down quicker which requires you to check point gap more frequently and have to reapply grease on the cam more frequently. Hows the condition of the distributor cam?

Lets do this before I send you on a goose chase dropping the gas tank and such...back up a minute. Did this car exhibit these problems prior to changing the parts mention above?
If not then one of the new parts is likely faulty...ie coil. If you have the old coil and condenser try installing them one at a time and see if the problem goes away. Do you have an Ohm meter?

Inspect the items in my prior post then well go from there.

tkheld

So let me start at the beginning. I bought the car in 2000. It ran well but started rough when cold (I assumed choke problems.) I was on active duty in the Navy and had young kids and no free time. I drove it on warm sunny days when I was at home and not deployed. It barely saw 500 miles per year but it ran fine for 2-3 hrs on a weekend. The stumbling started last Summer and by Fall, I had had enough. One of my sons was showing a strong interest in working on the car and we got working on the first tune up since I bought the car. So last September, we replaced the coil, points, rotor, cap, wires, and plugs. It was running better but the carb started leaking and the car went into winter storage.

I was too busy with work over the winter, so I sent the carb to Sparky for a rebuild. I had to troubleshoot his rebuild and replace the needle and seat and finally got the car running again in June. Now it runs much better but still has the random stumble when hot in gear. I replaced the fuel pump and line to the carb when I re-installed the carb.

So now I need to figure out what is causing the stumble. I had the radiator checked and I know I need a new or re-cored radiator. But I figure I also have a grounding issue somewhere in the ignition system that shows up when the engine is hot.

I will go ahead and re-check all the tune up settings also.

Along the way, I paid a shop to replace the exhaust system, all the suspension components, body mounts, and front disc conversion (all in the name of keeping it safe.)

Thanks again for the input. Let me know if this info sparks any other trouble shooting ideas.

oldcutlass

Let us know what your tune is set to now and what settings you use when its done? Also remember you have a variable vane torque converter, make sure its operating correctly. Make sure your mechanical and vacuum advance is working and not hanging up. On my car, I found that the vacuum canister was sticking from lack of use and messing with my overall timing.

tkheld

Spent the weekend re-checking all the tune up settings. Everything was per the service manual. I noticed a small puddle of fluid at the front of the intake - coolant. Then I noticed the troubleshooting section of the service manual (at the end of the tune up on section.) There is a list causes for "idle - stumble or hesitation". After listing all the tune up issues, it lists "leaking head gasket".

Is there a way to check for a leaking head gasket?

Thanks,
Tim

cjsdad

Simplest check for a leaking head gasket is to check the radiator. If it is losing coolant, or you see bubbles in the coolant while running, Houston you have a problem. There are other ways to check and you can have a leaking gasket that doesn't affect the cooling system. Some of the other guys will have input for those problems.

That is the exact reason my Cutlass has been sitting still all year. Bad head gasket!

droldsmorland

I doubt its a head gasket. Are you losing coolant? Do you smell it in the tail pipes? Id still be leaning toward one of the items you've replaced or rebuilt. Whats the fuel pump pressure read at idle? Look at and read the spark plugs. Did you try installing the old ignition parts to see if the prob goes away? IE Coil condenser etc. Did you look hard at the negative wire leading to the points? Id still be inclined to look at the simple stuff before leaning towards engine tear down due to a miss. My bets still with fuel or ign systems. Did you try installing another set of plugs? But first read the set currently installed and report back.

pmathews

Where is the intake water leak?

Mine seeps at the water neck on top of the manifold, but it's not enough to worry with at the moment. If it's leaking more, then resealing the neck and bolts with RTV will fix it, but I'm not sure if that's what you're seeing. Pictures will help

tkheld

I thought I had found the problem when I pulled the distributor cap and found the wire to the coil had been rubbing on the weights and had bare copper showing but I replaced that wire and re-routed it but that did not solve the problem.

I set the points @ 30 deg using a dwell meter. Set the timing at 7.5 deg and checked all the plugs at .030. I also replaced the vacuum hose from the carb to the distributor.

I just drained the radiator and did not see any oil there nor have I smelled any coolant in the exhaust.

I occasionally see dampness or a small puddle on the intake by #1 and #2.

I have not measured the fuel pump pressure but this was happening with both the old fuel pump and the new one. I checked the rubber fuel hose from the tank to the hard line and it is in good shape.

Keep in mind - the stumble was happening before I replaced all these components.

tkheld

Pics of Sparkplugs 1, 3, 5, 7

tkheld

Pics of Sparkplugs 2, 4, 6, 8

tkheld

Pics of Engine and Intake at #1 and #2

billmerbach

I'm subscribing our car is doing the same thing now and we are stumped

oldcutlass

Spark plugs look good, I'd set the gap on the plugs at .035. Have you adjusted your a/f mixture screws on the carb? I'd do it fully warmed up. On the intake bolts, you might consider trying to tighten them to see if they are loose, but not too much.

Oldsmaniac

I assume it stumbles when you try and accelerate from a stop? Even though the carb was rebuilt something could have been missed. It is important that all passages are blown out with compressed air. It could be the accelerator pump in the carb. If you dont get a shot of fuel when the throttle plates are opened you get a hesitation or sometimes it will stall the engine. Just a thought....

droldsmorland

It looks like your running lean as hell, but there isn't many miles on the plugs. I don't see anything else that looks out of place. Coolant or fuel can pool on the intake depending on which systems leaking. Coolant generally comes from the TStat housing or bolts. RTV cures that. Fuel from a leaking carb. Hopefully your new rebuild isnt leaking.
How many miles on this engine?
I know you said it stumbled before any part replacement but we need some baseline numbers to go by when trying to trouble shoot on the web. Especially from an existing problem.

Here is what we need from you:

1. Vacuum reading at idle, hot, 6-700 rpm with the vac advance hooked up on a direct intake vac source not a ported nipple on the carb. Hook the gauge to the same source.
2. Fuel pressure reading at idle, at speed and while cranking. Hook the fuel PSI gauge up inline with a T. So you need to fab a temp (safe) fuel line and run the gauge up to the windshield and observe it at speed when the stumble occurs. Do you have a vented or non-vented fuel tank in this car?
3. Compression check on all 8 cyc. Do you know how to do this correctly? Get a good compression gauge and a remote start switch (you'll thank me later).

Get a decent PSI/VAC gauge, compression gauge and a remote start switch. Stay out of harborjunk!

Still not sure what you have going on. Could be fuel, ignition or mechanical such as timing chain, burnt valve broken valve spring etc...

Get the above readings and we will have a clearer picture of whats goin on.

gs72

X2 on vacuum readings, fuel pressure and compression. Another thing to check (that a lot of people miss) is for a vacuum leak on the under side of the intake manifold. To do this take the PVC valve and crankcase breather lines off of the valve covers. Plug both holes on valve covers with your thumbs and make sure the crankcase is building pressure and not drawing a vacuum. If vacuum is present the intake gaskets are leaking on the underside of the manifold. Just a thought.

tkheld

Odometer reads 135K. I bought the car in 2000 @ 123K. There is an annotation on the Protect-o-plate saying the engine was rebuilt at 93,000 miles.

The only time the engine stumbles is at idle, in gear, engine hot.

Runs fine in park and while driving so I am not sure checking fuel psi while driving is necessary.

Gas tank has the nipples on the drivers side aft with the hoses that just tuck up above the tank - I assume that means vented?

Fluid is definitely coolant not gas.

I will need to acquire some tools to check everything else.

Thanks,
Tim

tkheld

Reviving this thread. I got tired of chasing the stumble and just lived with it for the past 3 years. I also got sidetracked with my son's 70 Cutlass (Mitchy) so I haven't done anything to my '67 but drive it.

Since I have checked everything else I can think of and everything everyone else has recommended, my suspicion is that my intake gasket is leaking just enough to disrupt combustion in one of the cylinders.

Since i have to remove the intake, I decided to do the 2 bbl to 4 bbl swap. I have an original 4 bbl intake off another '67 330. I had a Quadrajet rebuilt by a local guy (Bob Stone - he does carbs for Thornton). It's time for disassembly.

Pics of the new carb and intake attached

tkheld

The best paint I could find was not an exact match for the color currently on the engine (what's left of the paint anyway.) So I decided to remove the valve covers, clean and paint and reinstall with new gaskets.

Interestingly, they were once blue, painted orange (as was the rest of the engine) and then painted the current gold. Gotta love 50 year old cars and their mysterious past.

tkheld

The Quadrajet is from a '72 but the rebuilder knew it was going on a '67 330 and rebuilt it to work with my engine. I have noticed one potential problem with the clearance between the fuel inlet and the water neck. The fuel line will need to bend pretty tight right out of the inlet. Has anyone ever used a 90 degree banjo inlet? Any other recommendations are welcome.

https://quadrajetparts.com/banjo-inl...d66c25c3bb956c

tkheld

Pic of clearance issue

oldcutlass

I've used similar fittings with Edelbrock carbs.

joe_padavano

Your carb inlet to t-stat housing clearance is no different than on any 1968-up Olds V8 with Qjet. Literally millions of cars were built with a metal fuel line that fits in there.

oldcutlass

I edited my post above, was going off my old carb that had the side entry fuel line.

tkheld

Thanks Joe. Would any fuel line for a 4 bbl have a bend that sharp or can you recommend a specific application?

By the way, my son Mitch and I enjoyed meeting you at Carlisle this Spring - that window crank worked great - perfect match.

-Tim

olds 307 and 403

I bought the hard line from Supercars Unlimited, it fit nicely. Mine was the 73 to 76 fuel line, mine being a later 800 cfm carb.
http://www.supercarsunlimited.com/68...ine-d1441.aspx

joe_padavano

Any Olds 350 application will have that same bend at the carb end. The differences are at the fuel pump end. Unfortunately, the front-entry Qjet was never used on the 330, so I don't know what the configuration of your pump outlet is vs. a 350.

Glad that worked for you. It's always nice to meet CO members in person.

tkheld

So the '67 CSM states that the distributor needs to be removed for the 400 and 425 in order to remove the intake. But when I look at my 330, there does not appear to be enough clearance to remove the intake without removing the distributor. Has anyone else been able to swap intakes on a 330 without removing the distributor?

joe_padavano

Yes, you can remove the intake from an SBO without pulling the distributor. There is just enough room to tilt the intake up to clear the oil fill tube. The taller deck height of the BBO puts the intake that much closer to the underside of the distributor, which is why it won't work on those. Note that this applies to the stock point-style distributor. The larger HEI may not provide enough clearance.

olds 307 and 403

Is it tighter in the 67 and older A body? There is plenty of room with the SBO in the G body and later A body with HEI.

cjsdad

When I installed the Q-Jet on my '67 330 I didn't realize there was a problem with fuel line clearance. I don't know what the piece of steel line was from or for. It was just a piece of scrap I picked up somewhere but it fit so I used it. You can also see the fuel pump connection in this pic so it may help Joe tell you if the ready-made lines will fit.



Any small tubing bender should be able to make a custom fuel line that will fit. I have both of the two below and they have both made bends similar to the one in the picture above.

cjsdad

This picture shows that the intake can be removed without taking the HEI distributor out but it is infinitely easier if you do remove it. BTW, I did make the bend in the tube coming out of the rear of the carb with one of the benders above. Can't remember which now.

IMG_20150624_192839569_HDR_zpseb7vklt1.jpg

joe_padavano

No, I just didn't have any firsthand info on an SBO with HEI (hey, most of my cars are BBOs )

olds 307 and 403

I hate retiming motors for no reason, if I wanted to do that, I would own a chebby. It is not that bad but I would use an engine hoist with an iron intake, another reason to use an aluminum intake. No way I would lift a BBO iron intake by hand. Be very generous if you are using RTV where the end seals would go, build it tall more than wide.