Repairing 305 vs. new Goodwrench 350

[Slonaker]

Originally Posted by 87 STEPPER

^
It only makes sense that a small engine with less power in a heavy vehicle will use more fuel to get it going down the road than a larger eng will.

It doesn't have to work as hard as the smaller one therefor it will use less fuel.

Huh? So a big block should get better mileage than a smallblock, right?

Slonaker

[Mickey_D]

Originally Posted by 87 STEPPER

^
It only makes sense that a small engine with less power in a heavy vehicle will use more fuel to get it going down the road than a larger eng will.

It doesn't have to work as hard as the smaller one therefor it will use less fuel.

Um, sorry.

How can two identical vehicles except for engine displacement make the smaller engine get worse fuel economy? Unless there is something fundamentally wrong with the smaller engine (like there is in the 305). That would be like saying a 1.8L Ford Escort GT would get better fuel mileage than a 1.4L Ford Esgort GL. Ain't gonna' happen. Sorry.

[piecesparts]

Originally Posted by Mickey_D

Um, sorry.

How can two identical vehicles except for engine displacement make the smaller engine get worse fuel economy? Unless there is something fundamentally wrong with the smaller engine (like there is in the 305). That would be like saying a 1.8L Ford Escort GT would get better fuel mileage than a 1.4L Ford Esgort GL. Ain't gonna' happen. Sorry.

How can two people with the same cars get lost in the city? Same basic question... The smaller motor is just not exactly the same as the bigger one. Cubic inches, cam specs, the guy that assembled it, bearing clearances, machine work, dirt in the intake, oil quality, YOU NAME IT.

[Mickey_D]

Actually I was talking about the EPA registered mileage for the type of vehicle.

On average, most of the time, the same model vehicle with a small engine will get better mileage than one with a larger engine. But when it comes to the GM 305 vs the 350, the reverse is generally true. At least in my experience. I realise others will have different experiences.

[MylilBowTie]

I agree some with 87 STEPPER about the fuel consumption issue. A 350 is better able to handle the same load that a 305 might have trouble with. The harder an engine has to work its going to consume more fuel then it would otherwise. Being that the 350 has more torque is doesn't have to strain the engine near as much. Its somewhat a moot point but still a valid point.

One other point that the 305 is getting 8-10 mpg is its worn out so it will use more fuel. Plus with towing loads it is putting more strain on the engine. Not saying the 305 cant handle it just that there are reason for fuel mileage.

I have a 92 305 that is tbi and get 18-19 mpg city driving and it has decent power. So you can get decent mileage from a 305 but there are alot of things to factor in as a whole.

I myself would get a 350 if I had the means to do so. Otherwise I guess you take a gamble with fixing the cylinder heads and seeing how it holds up. I take it the engine over headed and thats the cause of the cracked cylinder heads?

[Srubydo1986]

I might be wrong here about the big block small block engine fuel econmy but

A small block might have a harder time at take of but the big block weighs more. But for the take of it might be easier for a bigblock the energy to keep that engine going down the road is less in a small block compaired to a big block.

All im saying is everyone thinks about take off but what about after its going and momentum is on its side. It makes sents then cause no one drives stop go for a hole tank of fuel.

[piecesparts]

Originally Posted by Mickey_D

Actually I was talking about the EPA registered mileage for the type of vehicle.

On average, most of the time, the same model vehicle with a small engine will get better mileage than one with a larger engine. But when it comes to the GM 305 vs the 350, the reverse is generally true. At least in my experience. I realise others will have different experiences.

EPA---SMEEPA, I disagree in a lot of cases. Take for example the FORD (Cough cough, can't believe I said that) Mustang. I say this because I saw it happen. They sold a lot of them with either the six banger or the v-8. In a large amount of the cases the sixes got better mileage than the eight (IF YOU DROVE IT LIKE A GRANDMA). The v-8 carrying the same weight of car is working 40 percent less, than the six to get the same performance. The 8 cylinders do take more air and fuel, due to size, but the effort is less to get the car up to speed. The same applies to some of the finer creations that GM, Dodge, and Ford created for trucks in the late 70s and through the 80s. The gearing and the motors have to be just right.

[Johnny05]

I've got an '83 with an original 305 and manage between 14-16 mpg. That's better than my '72 was with the GM crate 350 which at best would get 12 mpg. My '83 has 53k original miles and runs TOO quiet and smooth.. at least that's what I tell my wife so she won't ask about the dual exhaust I have coming....

Given a choice if the 305 is in otherwise good shape I'd say change the heads and save some $$ in the process.

[86swb]

Wow, now I am more confussed than ever. I still rather have the 350 than the 305 and that folks is just me.MO

[85C1500]

Unbelievable response to my question! Thanks to everyone for all the input and valuble info. I decided to take my chances and I ordered the replacement heads for $360. I should be installing them in the next few days. I would rather have the new 350 and I can afford to go either way, but I just didn't feel like spending that much $ on this pickup at this time. If I can get a couple more years service out of this engine I will be satisfied. If it doesn't work out I guess I will be buying a new engine.
My brother has a used 350 sitting in his garage I can probably get for almost nothing. I might be able to get that 350 and rebuild the lower end. So the 305 heads I'm buying won't work on a 350 or 383 block?

[MylilBowTie]

They will bolt up but it isn't to ideal. The cc size it pretty small (58cc) so that means it will give a 350 -383 a higher compression ratio. The other side is port volume is on the pretty low side for a 350 and for sure with the 383. The valve size is also smaller than normal 350 heads. You would be better off getting a set of vortec heads or an aftermarket set of world product S/R Torquer / Sportman II. Better cylinder heads than those are going to start about 1200 and higher like AFR, Canfield, Brodix, stuff like that. Depends on the money you want to spend and want you want it to do.

How did your heads crack on the 305? That would be important to fix so that it doesn't happen again.

[84slopwaggin]

They will work, but this combination is not pump gas friendly. The small cc heads will bump the compression ratio up quite a bit. This could lead to detonation. I "think" they also have smaller valves and ports. This would only sufficate a 350/383. Hopefully your new heads give you the service your looking for.

[85C1500]

The delivery time on the 305 heads just got longer so I cancelled the order. l will probably buy the 350 goodwrench engine which the local Chevy dealer has in stock. Not sure why the original 305 heads were cracked, although I have heard that is a problem with 305 heads. The intake manifold also had a crack between the 2ndary ports, so maybe the engine was overheated at some point. The more I think of replacing the 305 with a new 350, the more I like it.

Is there anything that needs to be inspected on the TH350 while the engine is out? The trans worked OK but would upshift early from 2nd to 3rd when accelerating slowly. Upshifted fine under rapid acceleration. The engine vacuum was a little low (17-18) which I thought may be causing the early upshift. The vacuum will be higher with the new engine. I just changed the vac modulator, but have not tested it yet. Also changed the trans fluid and filter.

[piecesparts]

Th elow vacuum would have made the modulator work lazily. So that upshift would not be caused by that. If nothing else the shift would be late and hard.

[FLEET72]

Here are some other choices, remanufacured engines:
http://www.chevy350engines.com/looku...lay_engine.cfm


Year Model Cyls Engine Size Part No. Cost + Core
1985 Truck 2wd 1/2-Ton 8 305 DC05 $ 1198 + 0
1985 Truck 2wd 1/2-Ton 8 350 DC11 $ 1210 + 250
1985 Truck 2wd 1/2-Ton 8 350 DC12 $ 1277 + 285
1985 Truck 2wd 1/2-Ton 8 350 HD01 $ 2050 + 285
1985 Truck 2wd 1/2-Ton 8 454 DC44 $ 1899 + 660

[MylilBowTie]

Probably would be a good idea to replace the front seal on the transmission. Might want to take off the governor cover and look at the governor gear. Its plastic and can wear in the center of it. It also has a weight assembly look to see if its sticking. Sometimes it gets gummed up with varnish.

Have you ever pulled an engine before or feel able? It is sometimes easier to pull the engine with the transmission. Just need to take out the three torque convertor bolts. Then after the engine and transmission are out the bellhousing bolts. I would sit the transmission on something a little above the ground to help get the new engine bolted back up to it. You can pick up the engine with the hoist then bolt the transmission on. Make sure the torque convertor is in all the way. If not it can crack the bell housing area on the transmission or ruin the convertor. One other thing of importance if you take the engine/trans out together would be a transmission tailshaft plug.

[84slopwaggin]

There you go good choice. One thing to think of. If you got a weak tranny already a fresh power plant will only bring its end sooner. I'd worry about that when it happens, though. If your doing the swap yourself for the first time do lots of research before taking the plung.

[grinch4om]

I had a great running 305 in my truck, 13.5 MPG in town, decided I wanted to slap curbs, tossed a crate 454, 92 replacement motor for a suburban, headers, duals, wiend 650 soreadbore, gets 13.5 in town, 16-17 on highway....same as the 305...my experience in the past is that when a good running small engine in a heavy vehicle gets crap mileage, upping the inches helps mileage when driven sanely. It is a trade off sometimes. I hear all these corelations and they are comparing apples and oranges. Stock for stock this seems to work. There are other ways to get mileage out of that stock small engine,i.e. intake,exhaust,ignition, but ultimately, what do you want the truck to do.

[85C1500]

I bought the Goodwrench 350 and am putting the accessories on it now. I removed the 305 engine/trans together. When I removed the fwd seal in the trans the bearing behind it was begining to fail and flaking off babbit so I took the trans to our local trans shop. Thanks for all the advice, glad I bought the new engine.