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Engine is the 350 rocket 4 barrel, with automatic transmission. I was told by one mechanic that it is not the original engine; but is a 1970 model.
It sounds OK (at least to my ears) at idle. However, at acceleration, it bogs down and acts like it is going to die. So far, I've taken it to two mechanics. Both told me that the carburetor was the culprit. After about $500, it now runs worse than ever. I'm also getting under 10 mpg (driving it VERY easy). Obviously, I don't know much about engines; but the carb must be pumping a lot of gas through. Since I have owned it, it has never sounded like the typical Rochester Quadrajets that I remember.
Ideally, I would like to get a recommendation for a good Oldsmobile mechanic in my area (Western North Carolina) to diagnose / fix. Actually, I would like a good mechanic to go over it with a fine tooth comb. The car only registers 70,000 miles; but who knows about the engine. I honestly have no idea how to start troubleshooting / diagnosing something like this.
Second, I was told that swapping in a new transmission would greatly improve MPG. Is there any truth to this? If so, that may be the next thing I do.
I appreciate any and all suggestions. I would like to be able to count on this as a daily driver before this fall.
Engine is the 350 rocket 4 barrel, with automatic transmission. I was told by one mechanic that it is not the original engine; but is a 1970 model.
It sounds OK (at least to my ears) at idle. However, at acceleration, it bogs down and acts like it is going to die. So far, I've taken it to two mechanics. Both told me that the carburetor was the culprit. After about $500, it now runs worse than ever. I'm also getting under 10 mpg (driving it VERY easy). Obviously, I don't know much about engines; but the carb must be pumping a lot of gas through. Since I have owned it, it has never sounded like the typical Rochester Quadrajets that I remember.
Ideally, I would like to get a recommendation for a good Oldsmobile mechanic in my area (Western North Carolina) to diagnose / fix. Actually, I would like a good mechanic to go over it with a fine tooth comb. The car only registers 70,000 miles; but who knows about the engine. I honestly have no idea how to start troubleshooting / diagnosing something like this.
Second, I was told that swapping in a new transmission would greatly improve MPG. Is there any truth to this? If so, that may be the next thing I do.
I appreciate any and all suggestions. I would like to be able to count on this as a daily driver before this fall.
Thanks,
Kirk
Welcome.
While an overdrive trans will help, you need to get your engine running right before making mods like that. You have a fundamental problem - likely tuning or mis-matched carb - that needs to be corrected first. Either find a mechanic who has a clue or educate yourself. Clearly the person working on the car up to now doesn't know what they are doing. Good luck.
I have always wrestled with the fact that I can buy a whole lot of gas for the price of an overdrive transmission swap ($2500 or more).
How much will the MPG increase with an OD trans, and how many miles will you have to drive to break even on that $2500+ investment?
For me the numbers didn't support the cost of the transmission swap.
I would think the only time it would be worth a change to overdrive is if one has steep axles and highway drives it often. Along with better mileage you make the engine wear and tear less.
But until you know the engine is in tune it would be worthless.
How much will the MPG increase with an OD trans, and how many miles will you have to drive to break even on that $2500+ investment?
For me the numbers didn't support the cost of the transmission swap.
Its impossible for me to say because I have other factors that are affecting my MPG. The last time I drove on the highway, I was averaging about 8 MPG. I don't know if this is just wishful thinking, but with a good tune (or whatever it takes) and an OD trans, is 15 MPG just wishful thinking???
Assuming 3.00 per gallon, the cost of a mile at 15 MPG is .20 as opposed to my current .375 (3.00/8) for a savings of .175/mile. If the swap was 2500, the break even point is 14,286 miles; or roughly 1.5 years (maybe 2). If the tune alone gets me over 10, then I agree that it isn't worth it.
Of course, there are other factors. It is a pain to stop so often for gas. Its also hard to justify driving this car when I have a Vette that gets 20+ on the highway. I also have a Silverado 2500HD that gets about 13-14 MPG. The problem is that I would much rather be driving my Cutlass.
Are there any car clubs, other car enthusiast, etc... that you can inquire with for a reference locally? Is your 8mpg 100% hwy or more of a mix of hwy and local. These cars going from stop light to stop light don't do well at all and with your state of tune its probably more pronounced. Also if most of your driving is local, then an O'drive trans won't help you.
Your carb needs to be sent to a Qjet specialist like Everyday Performance. Ethanol fuel lowers gas mileage as well. The 2004R, preferred or 700R4 overdrive transmissions both have a steeper first gear which helps off the line acceleration and have a .67 and .70 overdrive gear along with a lock up torque converter both drop the rpm by nearly 1000 rpm at highway speed.
Send a pic of this "Quadrajet". I am starting to wonder about the secondary air valve spring not having enough tension. When you push the secondary air valve oipen..........the top one on top, does its nap back or close very slowly ? You can check this with your finger with the air cleaner removed, and the engine not running. Let us know what you find.
Kirk, you need to start at the beginning, first a compression test to determine the health of the engine. Next a vacuum check at various engine speeds. Next timing at various engine speeds. Carburetors require a strong vacuum signal to perform correctly. Without a sound healthy engine even the best carb won't perform. Youtube is very helpful explaining these tests. A few pictures of your engine compartment with the air cleaner off may help us spot something that doesn't look right. There are some very sharp people on this site. Good luck, keep us posted.
Another '69 Cutlass S convertible in my neck of the woods! Cool . I live just south of Asheville and drive my '69 up to Black Mountain all the time (at least until the mud slide closed Rt 9).
My '69 was a mismatched mess when I got her but she's come a long way. I assume your mechanic concluded the engine is from a '70 based on the 4bbl intake & carb. The '69 has a divorced choke while the '70-'72 have the choke integrated into the carb. What Qjet do you have? 7042250? Jetaway or TH350? What gears? For me running ethanol free gas 12MPG on the highway is about as good as it gets. Aggressive driving on the mountain roads is closer to 8.5MPG. For reference mine was a factory 9:1 2bbl that I converted to a 4bbl (basically 70+ 4bbl specs), TH350 and 3.42 posi.
If you want to shoot me a PM we can exchange phone #s and can chat further.
If the swap was 2500, the break even point is 14,286 miles; or roughly 1.5 years (maybe 2). If the tune alone gets me over 10, then I agree that it isn't worth it.
That's not too bad. For me the breakeven point is around 12.5 years.
Like has been said many times, you need to get the engine running the best it can before you jump into the trans swap.
OK, I took some pictures of the engine and carb for more information: Engine with Air Cleaner removed Carb Carb number looks like 7040250 Head Number looks like a 6
As suggested, I pushed down on the back butterfly -- it opened with little resistance and then closed.
I found a shop in Asheville that works on older cars. I'm going to call them tomorrow and see if they will diagnose and fix the problems. I will ask them specifically for pressure tests for all cylinders, vacuum test, etc. If I ask for a full tuneup as well, is it worthwhile to change the points to an electronic system like Pertronix?
65Delta -- I can't believe you are so close! When you wrote that message, I was actually in Hendersonville (taking the back roads until 9 reopens).
A big thanks to everyone who has chimed in. I am desperate to get my car running in top shape!
You don't have points, there is a later model HEI distributor installed. They have to make sure its wired right, it needs full voltage (in other words the resistance wire hopefully was removed). They need to inspect the cap and rotor for wear and corrosion, replace if necessary. Replace spark plug wires, probably spark plugs, replace fuel and air filter. For adjustments, Idle A/F mixture and timing (for an HEI, not points). In addition to the vacuum, compression, and a leak down tests, have them make sure there is not a lot of play in the timing chain.
All this is going to be expensive to have someone else do it, be prepared.
Well, we are all guessing here, as it always is when not on site at the car.. But have you checked timing? That would be real easy. I know that my Olds runs like crap if set to 12 btdc as is the spec. Mine likes about 20 btdc. Try it. But then make sure it doesnt spark knock, etc.
Kirk78h: That's so cool. You were practically on my doorstep! How long did the car sit before you got her/started driving her? There's a lot of rust on the wrench flats for the plugs. Also be wary of the timing marks. The outer hub of the balancer can spin as the rubber ages and the timing marks are out of position. If the balancer looks suspicious set the timing with a vacuum gauge (lock timing in at max vacuum generated) and see how she runs. Based on the MC it looks like she still has front drum brakes as well.
Kirk, thanks for the pics. I hope you have good luck with your mechanic. The carb you have has mismatched parts, not a big deal but the top does not go with the main casting. Search 69 convertibles with your engine/trans combo and get pictures of how your engine should look. The proper throttle cable brackets and other details will help with reliability. A service and chassis manual will help a lot. Pertronix wouldn't be my first choice for distributor, I'm old school recurved points distributor with Accell components anyday.
July 27th, 2018, 01:20 PM
. I live just south of Asheville and drive my '69 up to Black Mountain all the time (at least until the mud slide closed Rt 9). 
