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Old 07-08-2010, 08:33 PM
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Which cam should I choose?

Hey guys,
I'm looking to find a cam that will help to provide good gas mileage around 55 to 60 miles per hour. During these hard economical times I like to see low rpms and a fuller tank!

These are my options for my 305 engine:

368"/398 lift 1000-3000
242/252 Duration

389/420 lift 1000-3000
22/262 Duration

420/442 lift 1500-4000
262/272 Duration

10.5 to 11.5 to 1 compression ratio.

With the cam and small cubic inch engine I have domed pistons to help create a higher compression. I know that gear ratio plays a huge factor in this as well but I have not tackled that. Currently my concentration is all on the engine.
Thanks everyone,
MuscleCarGaL
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Old 07-08-2010, 09:09 PM
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With that kind of compression and small cam, your savings will be eaten up by race fuel.
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Old 07-08-2010, 09:13 PM
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Quote:
Originally Posted by MuscleCarGaL
Hey guys,
I'm looking to find a cam that will help to provide good gas mileage around 55 to 60 miles per hour. During these hard economical times I like to see low rpms and a fuller tank!

These are my options for my 305 engine:

368"/398 lift 1000-3000
242/252 Duration

389/420 lift 1000-3000
22/262 Duration

420/442 lift 1500-4000
262/272 Duration
ok let me get this straight. You want a cam to improve gas milege. I think you best option is the leave the 305 as it is. Only thing id do to it is pop some headers on along with a good exhaust and keep rolling. What type of vehicle is it in.
10.5 to 11.5 to 1 compression ratio.

Thanks everyone,
MuscleCarGaL

With the cam and small cubic inch engine I have domed pistons to help create a higher compression. I know that gear ratio plays a huge factor in this as well but I have not tackled that. Currently my concentration is all on the engine.
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Old 07-08-2010, 09:25 PM
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Cam change is not the best answer. Don't think you'll see much change as you will find yourself putting your foot in it to make up for lost power.

305's usually have very, very restrictive exhausts. If you don't have headers on it already, put some on. Should help a lot.

Overdrive transmission. Doesn't sound like your making huge HP and TQ, should be able to swap a boneyard 700R4 in and have it live no problem.

Rear end gear change.

Run sythetic everything.
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Old 07-08-2010, 09:27 PM
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I was planning on running E85 (which is much much cheaper) in it than regular unleaded gasoline. This is a street vehicle as i'm not wanting to drag the car.
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Old 07-08-2010, 09:34 PM
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Uhhhhh, you better do some research on E85. You will actually use more E85 than gasoline as it has less BTU's of energy per gallon vs. gasoline. You have to run bigger jets with E85. Look in any owners manual of any new car that will run on E85. It tells you to expect 20-25% less mileage on E85. You will spend around 23% more to burn E85 than gasoline.
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Old 07-08-2010, 09:36 PM
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Quote:
Originally Posted by cool rockin daddy
Uhhhhh, you better do some research on E85. You will actually use more E85 than gasoline as it has less BTU's of energy per gallon vs. gasoline. You have to run bigger jets with E85. Look in any owners manual of any new car that will run on E85. It tells you to expect 20-25% less mileage on E85. You will spend around 23% more to burn E85 than gasoline.

I was thinking that the compression ratio would help to improve mpg.
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Old 07-08-2010, 09:55 PM
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http://www.edmunds.com/advice/altern...3/article.html

Compression ratio is not all that big of deal to make horsepower. One full point of compression increase I think nets about 6% more horsepower. Somebody will post the correct figure, I am sure.

Plan the engine to be as efficient as possible and then work on the rest of the drivetrain as mentioned.
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Old 07-08-2010, 10:19 PM
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http://en.wikipedia.org/wiki/Octane_rating

On an alcohol blend it equals 87 octane for an E10 blend. 11:1 compression ratio is suppose to run at a 87 octane level.
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Old 07-08-2010, 10:28 PM
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To solve all of your problems. Buy and install a 350.What your gonna spend to do whatever it is your trying to do you'll have a great base motor to start with other than a 305. Not knocking the 305 cause I currently have one in my 86 C-10 that runs pretty good with just headers carb intake true dual and 700r4. I thinks thats all you need
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Old 07-08-2010, 10:35 PM
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Quote:
Originally Posted by American Muscle
To solve all of your problems. Buy and install a 350.What your gonna spend to do whatever it is your trying to do you'll have a great base motor to start with other than a 305. Not knocking the 305 cause I currently have one in my 86 C-10 that runs pretty good with just headers carb intake true dual and 700r4. I thinks thats all you need

The 305 has a longer stroke than the 350. I've pulled out the books between the two when i had the option to take a 350 instead of the smaller cubic inches. There are many different benefits in having a 305 if you are not planning on street racing nor driving 90 down the interstate with it.
1. no speeding tickets as it will run efficiently around 60, 70 miles per hour.
2. With the longer stroke it will use less fuel.
3. Although the 305 has less cubic inch the horse power created can equal or exceed that of a 350 easily.

Since i was going to build this engine up I realized if i did it right it would be fuel efficient have enough power for me anyway.

MuscleCarGaL
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Old 07-08-2010, 10:58 PM
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Quote:
Originally Posted by MuscleCarGaL
The 305 has a longer stroke than the 350. I've pulled out the books between the two when i had the option to take a 350 instead of the smaller cubic inches. There are many different benefits in having a 305 if you are not planning on street racing nor driving 90 down the interstate with it.
1. no speeding tickets as it will run efficiently around 60, 70 miles per hour.
2. With the longer stroke it will use less fuel.
3. Although the 305 has less cubic inch the horse power created can equal or exceed that of a 350 easily.

Since i was going to build this engine up I realized if i did it right it would be fuel efficient have enough power for me anyway.

MuscleCarGaL
Your thread topic is"which cam should I use" What are your intentions for camming a 305 when you can get the same performance from a stock 350. Im very confused but will let you figure things out
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Old 07-09-2010, 12:05 AM
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"11:1 compression ratio is suppose to run at a 87 octane level."

when Detroit built 11:1 engines, all companies were selling 104 octane hi-test, most people can get the engine to knock on 87 octane.

"The 305 has a longer stroke than the 350."

no they are both 3.48"

"With the longer stroke it will use less fuel."

actually it's the bore/stroke ratio that makes for the mpg.

"Although the 305 has less cubic inch the horse power created can equal or exceed that of a 350 easily."

build for build the 350 will ALWAYS make more HP, the 305 will ALWAYS get better mileage and cleaner emission numbers.

you didn't say which 305, flat tappet or roller cam? 2bbl, 4bbl, TBI, TPI?
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Old 07-09-2010, 02:15 AM
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Everyone is very helpful here, sometimes to a fault, but we all mean well! Yes, a 350 would be a better overall choice, yes a 350 would be cheaper overall than all this other stuff you have to do to a 305 to get the HP,etc., but she doesn't have a 350, she has a 305. Here's my two cents....
If you WANT a new cam, go with something just a bit larger than stock, with a low RPM range. Realize that when it says 1K-3K RPM, its just a RANGE. It is NOT going to be 1K for you. The stars and moon will never align perfectly for you in the 'real' world like they did for the engineers that tested that cam. IMHO, the cam is not going to make too much of a difference.
Put a set of shorty headers on the engine and let it BrEAThe.
Put a better set of heads on it.
Is is carb, EFI, TPI...?
As for the E85, stay as FAR AWAY from it as you can. Real gas is only a few cents more per gallon. Those few cents will cost you in repairs in the long run. Ethanol is a cleansing agent... once it finishes "cleaning" the gunk out of the bottom of your fuel tank, guess where it all goes? It WILL eventually EAT AWAY every seal, o ring, etc, just about anything it comes in to contact with (including metal). Not very much savings huh? Stay far, FAR away.
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Old 07-09-2010, 03:18 AM
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Quote:
Originally Posted by MuscleCarGaL
The 305 has a longer stroke than the 350. I've pulled out the books between the two when i had the option to take a 350 instead of the smaller cubic inches. There are many different benefits in having a 305 if you are not planning on street racing nor driving 90 down the interstate with it. *SNIP* 2. With the longer stroke it will use less fuel.
I don't know what books you've been pulling- but they are pulling your leg if they say there's any difference in the stroke between the 305 and the 350- the strokes are identical at 3.48".

Quote:
3. Although the 305 has less cubic inch the horse power created can equal or exceed that of a 350 easily.
Wrong, sorry. Bore diameter is the limiting factor to power production in this case. The small 305 bore will NEVER flow as well as a 350 bore- the valves become shrouded at even a diminutive 1.94" intake size, whereas a 350 can have an intake valve well over 2".

Quote:
Since i was going to build this engine up I realized if i did it right it would be fuel efficient have enough power for me anyway.
Properly built, a 305 can out MPG a 350, the difference in CID sees to that.

If you stay mild on the cam lift and duration and keep the induction velocities high and the vacuum high, you will get all the engine has to offer.
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