View Full Version : fine tuning my lark

04-27-2005, 03:35 PM
Now that I've fixed the brake problem, it's time to turn my attention to two other issues that my Lark has had since I bought it, maybe related, maybe not: 1) it runs a little hot - typically about halfway between half and three quaters towards hot on the gage, this in cool weather and not particularly hard use; 2) the milage seems a little low, my best tank so far has been 16.7 mpg in mixed driving. It's a 259 2brl auto with 3.31. The carb leaks a little and could probably stand to be rebuilt or at least adjusted some. Performance seems OK since the timing was advanced, no stumbles or flat spots. Am I wrong in thinking I should be able to get 20mpg in moderate driving? I've considered going whole hog and maching the manifold for a new 4brl or even fitting 3.07 gears and modifying the trans for 1st gear starts.

Any thought and/or suggestions welcomed. Definitely need to address the overheating if I'm going to Spokane this Aug!

04-27-2005, 05:32 PM
are you sure it's really overheating? It might just have a slightly hotter thermostat in it than stock; the stock standard thermo was a 170F unit which is NLA, your FLAPS probably only has 160 and 180. 170 seems to be just about midway on the gauge.

That said, if you haven't done it yet, it's probably not a bad idea to pull the rearmost freeze plugs and dig around in there with a wire and knock loose all the rust, casting sand, etc. that is likely in the block, then follow up with a good cooling system flush (and pull the drain plugs at the rear of the block to let it drain thoroughly) you will likely be surprised by all the crap that has built up in there over the years. Don't forget to turn the heater control on when you are flushing so you flush out the heater core as well.

good luck,


55 Commander Starlight
62 Daytona hardtop

04-27-2005, 07:30 PM
I'm with Nate to a degree here - 168 or 169, to be exact[xx(] (Sorry, just a little heated humor there![}:)]
First thing to be suspect of is that old gage. Find a candy thermometer and see what IT says when stuck into the radiator neck while the gage is showing hot.
As Nate says, these V8s (and 6s too) have the least movement of coolant around the rearmost cylinders. This means that rusty crud and any other foreign particles in the cooling system are gonna settle around and aft of the rear cylinders over time. Such can actualy build up, deep enough to where the temp sender gets a reading that doesn't jive with what the thermostat sees![:0] Since no good coolant flow can circulate behind the back cylinder, you develop a hot spot - right where the gage sensor mounts.:( This is ONE WAY the gage can seem to be bad when it's not! It's just seeing a different temp than the thermometer is because the sensor's in fairly stagnant coolant.
Pulling the freeze plugs is a real pain in the backside with the engine in the car. EVEN with a fancy installation tool for them, the new plugs would cause the pope to use blue language:( The copper expansion type plugs can be a savior here.
ALSO - as imprortant (moreso to me) as the freeze plugs is the threaded block drain plugs at the rearmost, lower corners of the block. RIGHT behind those is the deepest, dead-water crud spot of the whole engine. Fact is, you may well remove them only to have NOTHING gush out[}:)]- until you probe up into them with a screwdriver or some such thing to dig thru the crud there!
Figure on getting new plugs (they're common old pipe thread plugs), in brass to replace the ones you remove. Sometimes they're so eroded that there's really not much left to screw back in!
Anyway, freez plugs, drain plugs, or both - dig and flush - dig and flush, until the water flows fairly clean. Then you're good to go for another 3 or 4 decades!:D

Miscreant at large.