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Old 05-02-2006, 01:04 PM
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305, good, bad,?

I just got a '71 Chevy PU with a swaped in 305. This is the 1st 305 I have had, are they any good? I'm not looking to make a tone of power with this, just enough to have fun with and not get 6MPG or worse What are the big diferances -vs- the 350? (I have a 350 I could put in if I want)
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Old 05-02-2006, 01:06 PM
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What do you want to do with the truck?
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Old 05-02-2006, 01:11 PM
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It's just gona be my work truck/DD. Nothing to crazy, eventualy I'd like to be making around 275HP. I'm more interested in good TQ and decent milage. It's got a 3spd manual in it right now.
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Old 05-02-2006, 01:28 PM
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Car Craft Magazine article on a build on a 305 and some links to other sites at the bottom of the page.

http://www.goingfaster.com/spo/modthel03.html
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Old 05-02-2006, 02:47 PM
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http://www.hotrodders.com/forum/engi...ead.php?t=7879
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Old 05-03-2006, 03:14 AM
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Thanks guys! Thats a lot of good info. there. I think it will work just fine for what I want to do with the truck.
1 question thoe, can I just put the fule pump off of my 350 on it and be OK? Or do I need to go with a hi-po unit?
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Old 05-03-2006, 03:31 AM
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Yep, the fuel pump will work fine, but new ones are $17. They're kinda like thermostats. They're so cheap that there is no reason to use an old one.

The 305 is a fine engine for daily driver use. They can be made to perform, but since 350s are so cheap its hard to ignore the bigger cubes for the same price as it would cost to modify a 305.

In stock form they are fine. Where they tend to show their colors is when you try to get lots of power out of them. Many people assume that since a 305 is 87% the size of a 350 that it has 87% the performance potential. Since the 305 gets its cubes using a very small bore, that is not necessarily the case. The valves have to be smaller to fit the bores and it limits breathing rather dramatically.

A low-power 305 is a great motor. It gives good mileage and satisfactory motivation. If you plan on getting more power from it in the future consider that buying a REBUILT 350 may be cheaper than modifying your 305 to perform at the same level.
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Old 05-03-2006, 04:50 AM
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think TORQUE, not hp, that's what pushes you back in the seat!

last 305 I had was in a conversion van, added a 4 hole 1" carb spacer from a yard, changed the dist curve to come in sooner, added a "H" pipe and dual glasspacks, all adds alot to low end torque (more and all in at lower rpms)

less than $200?, 3600lbs?, would burn the big donut hides, plenty of zip, 18 mpg with 3 speed auto

everything else was factory stock...nobody would believe it was a "stock"

Last edited by red65mustang; 05-03-2006 at 04:58 AM.
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Old 05-03-2006, 08:34 AM
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For a work truck the 305 will be fine. Just keep it stock or use an RV cam and you'll be pretty happy with it. You need all the help you can get with mileage these days!

K
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Old 05-03-2006, 10:57 AM
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OK, with all this great info. I'm thinking:
A set of tri Y's, H pipe, and Flowmasters
HEI conversion, new fule pump, and a 650 or 600 Holley
An RV type bump stick, re-curve the dizzy, 1" 4 hole carb spacer
And enjoy driveing somthing that gets better than 10mpg

That sound about right?
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Old 05-03-2006, 03:33 PM
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geargrinder,
carb choice is to big, about 500-550cfm is plenty,
whole key to torque is higher velocity higher Hg A/F mix from idle to 4,000rpm

?RV cam?....if it has a split pattern and a little more lift on the exhaust side than intake side....yes that profile builds torque

don't add the tri-Y's with out the cam and carb, "all has to work together"
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Old 05-03-2006, 05:10 PM
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Quote:
Originally Posted by Geargrinder65
OK, with all this great info. I'm thinking:
A set of tri Y's, H pipe, and Flowmasters
HEI conversion, new fule pump, and a 650 or 600 Holley
An RV type bump stick, re-curve the dizzy, 1" 4 hole carb spacer
And enjoy driveing somthing that gets better than 10mpg

That sound about right?
Sounds pretty good.

A regular Performer intake and a spread bore single feed Holley 650 (hly-0-8055c, summit racing, 315.00) should do the job. The spread bore (small primary's) does the trick to help throttle response and mpg. Plus the vacuum secondaries can be tune to open as much as your engine will need. The 650 will give you room to grow if you ever decide to get a 350. Avoid carter and edelbrock carbs.

Headers will make more power on just about any small block chevy combo. Maybe not more peak power but certainly more torque at lower rpms which will increase mpg. However, headers will make noise. An H-pipe will help lower the noise inside the cab. Avoid flow master mufflers due to poor flow and very loud sound. I prefer the Hooker areochambers (not hooker maxflows). 2.25" pipe will be enough for a mild 350 or smaller engine.

A little cam will also help out. If you use headers, used a cam with equal intake and exhaust duration. Or maybe a cam with a maximum of 6 more exhaust degrees. If you plan on using stock exhaust manifolds then use a cam with 10 more exhaust degrees as compared to the intake.

A compcam 248H or 252H will be a good choice since it can be used with stock valve train components. Make sure to use diesel engine oil in your engine to prevent cam wear. Regular car engine oil is now missing some important additives that prevent wear of flat tappet cams. Diesel engine oil still has it. A lot of new cams are going flat due to this problem.

My c10 70 chevy would get 15 or 16mpg on the highway and 11mpg around town with a 350, headers, 260H cam, performer intake, 650 carb. Now it gets 14 mpg highway, 9 city with a 454. A 305 might get 12 or 13 city and 16 or 17 highway depending on gear ratio. Lets hope you have a 3.08 gear and not a 3.73.
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Old 05-03-2006, 10:02 PM
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im still tuning my .040 305 but here are the specs:

601 heads milled to a 55cc chamber
Mr Gasket thin head gaskets
Lunati Bracket MasterII Cam 00016lk
Power Plus dual plane intake manifold
stock rebuilt Q-Jet
Dynomax Headers
Jegs header back exhaust

2.29 gears in a 1979 Malibu

MPG: City, 13.5. Highway, 23

Dale
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Old 05-03-2006, 11:26 PM
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think 383 !! Lots of torque!!
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Old 05-04-2006, 01:44 AM
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305,good,bad,?

I've never had much luck getting mileage with Holley carbs. (of course I don't get much mileage with ANYTHING...) I'm currently running a Q-jet I had built for my truck.

barthmonster,how 'bout 383 with a blower-lots MORE torque!!!

DHMag,my truck gets about the same mileage in town as on the highway,about 12-looks like I need to find a taller axle ratio,huh?
355,9:1,Q-jet,Isky mid range cam,HEI,duals,SM420 4 speed/4.10 rear,31" tall tires
Speed
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