Engine: Get more out of the 170

[km420]

I have a 61 Lark VI with the 170 and 3sp auto. I apologize if this has been answered before, but I can't find an answer anywhere.

When driving down the road, I have no issues going 55, but anything above that and it doesn't want to cooperate very easily. I'm aware that may be the best I can do, but I'm wondering if there's anything I can do to get just a little more out of it. I would ideally like to be able to cruise at 65-70 if I were to take it on the interstate.

Will a rebuild be necessary? What are my options to *slightly* improve performance? As far as I know the engine, transmission and everything else is all stock. Any advice is greatly appreciated and I'll try to answer back with any more information I can supply. I've had this Lark for nearly 2 years and still don't know much about it.


Thanks in advance!

[BRUCESTUDE]

You may need to install a different rear end, one with a taller gear ratio. Check the differential and look for a tag with a number such a 4:10 or 3:55. My '60 Lark has the economy rear end ratio of 3:07 so it'll do 70 easy, but it also has a V8.

[tsenecal]

You should start with figuring out the gear ratio that the car has in it. If it is geared too low, you will never have much for top speed, although 55 is pretty slow for even a low gear ratio. The next thing that I would check, are normal tune up items like plugs, wires, points, cap, rotor, and how clean the carburetor might be. Last thing would be valve adjustment. If they are running a bit tight, it will affect performance. Others with more experience with the 6 cylinder will likely add to my response. Good Luck with it!

[StudeNewby]

Some have replaced the 170's crankshaft with that from the earlier flathead 185, thus creating an OHV 185. But it sounds like that might be more than you're looking to do.

[Dwain G.]

Are you saying the car just will not go any faster than 55? Or is it that you don't what to make the engine rev any higher? My '63 Standard with 6/AT will do 70 just fine. The RPMs are up around 3,000 at that speed though.

[Ross]

Have very many miles on many 170s and even with the stock 3.73 axle you should be able to maintain 65+ easily even up pretty steep hills. They don't mind the revs at all. Just freshened up the 170 in my 63 convertible and found zero crank wear at 95,000 miles. Put it back together with new rings and drove it 4500 miles from MD to Utah and back last fall at 65-70. Just want to raise your expectations a bit for a stock engine. I like them. A lot. In contemporary roadtests they were faster than most base model competition and they are very "light on their feet".

Adjust your valves to .027 hot and running which is a ten minute job on that car. Drop 60-70 bucks on points, condensor, rotor, cap, plugs and wires. Make sure the vac advance is good and the centrifugal works. Have someone press the gas pedal to the floor while you make sure the carb is opening all the way. Make sure your exhaust isn't crushed/ restricted. Heat riser is in the down position when its hot? Bring it back to a standard condition before you start thinking about modifications.

[TWChamp]

My 50 Champion with overdrive will do more than 55, but that's the speed I drive. I wish it had a 4.11 rear end instead of the 4.56 ratio. The engine sounds plenty busy at 55. The strange thing is my 50 Commanders and Land Cruiser are all about the same ratio with overdrive, and don't sound near so busy at 55 or 60.

What size tires are on your Lark? As mentioned, I'd check the rear end ratio, and go for one in the lower 3's.

[52-fan]

My 50 Champion with overdrive will do more than 55, but that's the speed I drive. I wish it had a 4.11 rear end instead of the 4.56 ratio. The engine sounds plenty busy at 55. The strange thing is my 50 Commanders and Land Cruiser are all about the same ratio with overdrive, and don't sound near so busy at 55 or 60.

What size tires are on your Lark? As mentioned, I'd check the rear end ratio, and go for one in the lower 3's.

Strange that the Champion should have problems. My previous 52 Champion with a 4:56 and overdrive would cruise 70 all day very well. Have you put a tach on it to confirm the revs?
Sometimes the roar of the fan makes the engine seem to be protesting. I drove my 71 Cuda without the fan once and was amazed at how much quieter it was.

[PackardV8]

When driving down the road, I have no issues going 55, but anything above that and it doesn't want to cooperate very easily. .. . . I've had this Lark for nearly 2 years and still don't know much about it.

Nor do we at this point. As others have alluded to, this lack of detail is akin to being in a dark room, looking for a black cat, which may not be there. The OHV6 has a following here and you'll get expert advice, but they need something with which to work.

1. Will the car actually hold 70, but just sounds strained to your ears? FWIW, today's better-insulated cars with double-overdrive transmissions and electric fans have re-educated our ears to never hear traditional engine noises. A low-geared Stude with the Swiss-cheese firewall and no insulation, by comparison, sounds like a threshing machine.
2. Or does it actually begin to stumble and misfire above 55 MPH?
3. What is the rear gear ratio? It's on a tag on the rear axle cover. After fifty-seven years, it might have been changed from the OEM ratio; or it could have been special ordered by a postman on the Wolf Creek Pass route.
4. What tires are on the car?
5. How many miles does the odometer show. (Never believe that to be a fact; but at least it's an indicator.)
6. Have the brakes been checked for drag?
7. Has the car received a thorough lubrication per the Shop Manual, including wheel bearings, engine oil and filter and transmission oil and filter?
8. Has the engine received a complete tuneup, including new air filter, ignition points, condensor, rotor, cap, wires and plugs?

jack vines

[thunderations]

When I had my 63 Daytona with the 170 and automatic, it ran 70 just fine. Would never set a land speed record or win a 1/4 mile race, but that was not it's purpose.
Wanting a little more performance, I started checking on improvements and the easiest change would be to a better carburetor. The one I was looking at was a Ford progressive 2 barrel that was used on Mustang V6 engines in the 80's. It's like half of a 4 barrel carb, running on 1 barrel and as needed the 2nd barrel opens up.
I never made the modification and sold the car. I would have liked to see what improvement that would have made.
Many years ago, playing with 40 horse VW engines, just adding a 2 barrel carburetor and improved exhaust would bump the HP up to 50-60.

[km420]

Are you saying the car just will not go any faster than 55? Or is it that you don't what to make the engine rev any higher? My '63 Standard with 6/AT will do 70 just fine. The RPMs are up around 3,000 at that speed though.

I've had it just over 60, maybe touching 65, but I've not been able to touch 70. I figure a tune-up would be a good place to start, and that will be my first course of action in the next week or so.

I've checked for a tag with a gear ratio and haven't been able to find one, it's been awhile though, so I'll check again.

odometer reads around 45k.


taller gears and a new carb are definitely things I'm looking into. I hadn't done much as I was looking at doing an SBC swap and have recently decided to just leave it as stock as possible.

[StudeRich]

If you follow Ross's advice in Post #6, I am sure the gremlins will come out, seriously!

A poorly tuned engine with a ignition point gap almost closed will act like that, plus other "weaknesses" in other electrical components or their adjustment: Ign. Timing, Dist. Dwell, Valve adjustment, Carb. Linkage etc.

Good luck with your analysis.

[km420]

Thanks everyone!

[64Avanti]

Well something is wrong. You should be able to hit at least 90 mph without any problem. Follow the tune-up advice given and pay attention to the distributor advance etc. Check your compression to verify that you don't have any valve or ring problems.

Report back and you will continue to get good advice from many of the people on this forum.

[Skybolt]

I put a 63 OHV 6 in my 59 Lark and it would do at least 100 mph, did it a couple of times, that was on the way to work so I backed off as the Highway Patrol dont like that sort of thing. I did have a completely upgraded ignition, no points, 8.8 wires, CDI, matching coil. Plus a 4bbl carb and a new exhaust with a Magnaflow muffler. Of course with all I did the suspension was upgraded too so it would be useful power.

I did however have an overdrive and 4.10 rear. The gearing was excellent.

https://www.youtube.com/watch?v=WsvL5Al61ic

https://www.youtube.com/watch?v=e8CPsJJtWKw

As mentioned before if all is as factory and no faults you should be able to get about 90mph. The original Flathead would do about 80mph.

Len