what makes it run differnet when cold?

[66StangGuy]

after work (dark and cold outside) my car seems to have more torque and just run a lot better overall. is this because its getting cold air in the intake and the air is more dense or is it because of the choke running the motor a little richer meaning i should get bigger jets? what do you think most likely is the cause. if i disconnect the choke so it stays on my car runs like crap. so maybe its too rich once it warms up. not sure. what do you think it is? if i could get it to run like that all the time then i would be happy.

anyone ever tried the holley adjust a jet kit? was looking at that
should i get something like that or should i just get a jet kit and play with different sizes to see what works best.

[thunderbolt]

As long as the engine is warm, the choke should not be engaged, but it would be an easy thing to check. When it is colder and the engine is running good, pull the aircleaner and observe the choke position. It should be wide open as long as the engine is warm. Check to see what position it is in during hot times of the day too because your choke may not be fully disengaged.

My money is on the cooler denser air. I know mine runs best on cool days with moderate humidity.

[66StangGuy]

ok ill check to when its cold and warm and see its posistions.
as far as power goes though i know whats you mean about colder days making it run better but usually after work its about 60 F outside and it just runs like a beast. i pickup more power then you would expect from just being cold outside. i think i may just need to get a jet kit. i have the holley 4160 4bbl vac sec. what do you think i should get for jets? also should i get the adjust a jet kit because i plan on doing heads and cam in about 2 months or less.

anyone made a good intake system with stock hood and not cutting the car up? cold air is a plus.

[rbohm]

the more oxygen you can pack into the cylinders, the more power you will make. that is how nitrous works, it gives up the oxegen molecule so it can help burn the gasoline more efficiently. when you lower the air temp, you get a denser air mass, thus more oxegen, thus more power as you noted. it has been found that for every 10 degree drop in air temp, you gain 1% hp. and use the choke only when the engine is cold.

[thunderbolt]

Sorry, I don't have any advice on jets for Holley's. But if you are getting heads and a cam I would definately get a jet kit unless you are changing carbs. No carb, with rare exceptions and expecially Holley's, will run as well out of the box as it will with tuning. Some carbs are better than others in that respect but tuning will help any carb. I would get the kit. The $20 or so I spent on my carter kit was well worthwhile.

[rbohm]

depending on the cam and heads you plan on using, i would bolt the holley on out of the box and see what it does and tune from there. holley's were designed to be used with modified engine's, that is why they run rich on stock or nearly stock engines. after you add a cam good heads and headers you need more fuel to get the right mixture for the engine to run right. which is why holley's are jetted about 5% rich from the factory.

[66StangGuy]

thanks rbonm that cleared up a few quesions and also backup what i thought. the choke is auto so i know thats not an issue. and i dont think its because the air is cold. i seriously feels like a good 10 or 15 hp gain from that. it just runs so much smoother and better overall. im thinking maybe the intake manifold is cold heping to keep the air dense.

that got me thinking why not run water passeges though just the intake itself to a small radiator like a tranny radiator to help keep it cool. and using an electric water pump. dont think i would hurt.


anyway thanks for the replys guys. guess ill just keep messin with it till i figure it out.

[rbohm]

that idea has been tried many times with no results other than the car becomes a bit heavier(not a good thing when you are in a weight restricted race class) and no power gains at best. if you are at the dragstrip, what you want to do between runs is ice down the intake as that will help through the first 300-400 ft. after that the intake has warmed up to the temp it would normaly run at, but likely you have gained a bit on your opponent who didnot ice the intake, and that may be enough to put you in the win column.

[mustangman65_79]

Originally posted by rbohm
the more oxygen you can pack into the cylinders, the more power you will make. that is how nitrous works, it gives up the oxegen molecule so it can help burn the gasoline more efficiently. when you lower the air temp, you get a denser air mass, thus more oxegen, thus more power as you noted. it has been found that for every 10 degree drop in air temp, you gain 1% hp. and use the choke only when the engine is cold.

Also, I think carb cars respond better then fuel injected partly because fuel injected uses exuast heat for the intake manifold, till it's warm.

[rbohm]

the only reason efi cars dont seem to be affected is they are tightly controlled by the computer, but the same thing still applies ulitmately.

[66StangGuy]

has anyone tried the adjust-A-jet kit?
its the kit that bolts to the holley and has valves that act like every jet size in one. so i can adjust it from the outside whenever i want. its about 100.00 do you think its worth it or should i just buy a few bigger and smaller jets and try them out. i prefer to not take my carb off the manifold but if i gotta then i gotta.