Bone stock 85 305 upgrade

[blakeasaurus]

Hello members:

New member here. I purchased a bone stock 85 2WD long bed this past spring. 2 tone brown. 43k miles on a bone stock 305 (VIN Code H LE9). Stock 4 speed auto with a shift kit the previous owner had installed.

She's pretty loaded: Power locks, power windows, A/C, cruise, cassette, Silverado trim. The 2 tone brown (technically, "Saddle Tan over Indian bronze") seems invisible to the cops. I call it "grandpa brown 2 tone."

I was specifically looking for a unmolested survivor. The paint could use a polish, but it looks pretty darn good for 40 year old single stage.

It still has the AIR pump, EGR, everything. With 43k original miles, the 305 runs fine, but leaves something to be desired in the "fun" department (and the valve seals, along with every other rubber seal on this 40 year old engine, are shot).

I am looking to upgrade to a Gen 1 350. I live in northern Michigan. This is my daily driver in the summer and fall.

Here are my goals:

Retain Quadrajet and Q-jet manifold (I love the sound of the Q-jet's secondaries opening). And 99% of the time, I'm not into the secondaries anyway. I will address the Q-jets weaknesses of fuel bowl leaks and throttle shaft vacuum leaks with epoxy and bronze bushings.

Retain original air cleaner. I have the giant 5.5" tall air cleaner with what appears to be a pretty darn good factory cold air setup.

Get 300 hp at the flywheel with exhaust manifolds (I don't like burnt spark plug boots / exhaust leaks).

I have some aluminum "Camel hump" heads. These have no exhaust crossover so EGR will be deleted on new engine. Looking for a stock looking and stock sounding Gen 1 small block. These have 2.02 / 1.60 valves, so the 305s bore size is out. Hence the 350.

Goal is 20 mpg on the highway at 70 mph on 87 octane. She currently gets around 15 at 70 mph.

Rear axle ratio is 3.73:1. With my tires, it turns about 2,200 RPM at 70 mph in OD. I am willing to go to a 3:55 or something even taller (3:23) - even at the expense of torque. This extremely mild 350 with 3:23s will still be leaps and bounds past the stock 305 with 3:73s in that department.

Basically, I'm looking for a bone stock looking Gen 1 small block with a more modern power to cubic inch curve. I also want a very smooth idle (and good mpg), so I'm not going crazy in the cam department. Looking for 18" plus of manifold vacuum at idle.

Usage will be many 80 mile round trips to to Menards. We are building a new house this spring. Wanted a little more grunt for passing on the 2 lanes, It's pretty scary with the 305. She takes her time from 50-70 mph.

Asking about if I should go with a Vortec or Gen 1 style 350 block. I like the Vortec for the 1 piece rear main seal but is there anything else to know using a Vortec block with Gen 1 style heads? Are there modern 2 piece rear main seals that are just as reliable as the Vortec style 1 piece? Hunting for either a Vortec or Gen 1 350 shortblock will open up more options for me.

Advice appreciated

Thanks

 

[goldpack]

so what you got is a 40 year old, 2wd survivor,...that may get 14mpg on a good day.

18-20mpg on straight uninterrupted highway (no idling / poking along in town)
and 285~300hp.
= a 5.3 gmc engine truck from 1999-2006 era.

for time / energy/ sanity of while building a house on your brain, such would be 1999-2006 with the truck attached to it.
(if to swap, I would suggest a running / wreck / rust bucket of a 1999-2006, so you can get all the major / minor / forgotten parts at your finger tips)

but that is just my initial assessment. (plenty of people here with better ideas / builds , ...welcome aboard though).

 

[Turbo4whl]

^^^ What @goldpack said! 1999-2006, after those engines GM had deactivating cylinders. Early ones had issues. Don't see you getting the MPG you are looking for with anything else unless you go much newer.

 

[goldpack]

^^^ What @goldpack said! 1999-2006, after those engines GM had deactivating cylinders. Early ones had issues. Don't see you getting the MPG you are looking for with anything else unless you go much newer.

I got a 2002 with 190,000 5.3 flex 4EAT 3.73
and gets that gas 16-19mpg,...never had anything wrong with it. (bought with 165,000 on it 10 years ago).

one of my friends has a 2005 5.3 flex with 300,000 miles on it. (engine still great and untouched,...4EAT 4L60 been replaced but he has towed often).

I got 2x 5.3 2008 cylinder deactivation turd engines,...if anyone wants cores that suck the money out of your wallet,...and make you loose head hair.

 

[fast 99]

Do some calculations based on cost per gallon and expected millage improvement. Think you will find the numbers don't work out. Even something as simple as a new carb may take 20,000 miles to break even. I used to do these calculations for our fleet when selecting motor size/fuel on new vehicles. If doing for other reasons such as increased power thats another thing. For me if this truck is nice, unmolested and runs decent would just leave it alone, may be change rear gearing. It's the old story don't fix something that isn't broke.

 

[Ricko1966]

Get a good used vortec block put a cam in it use your heads the vortec exhaust manifolds pick a cam that makes power in the 1500 to 5000 range. It will have good horsepower ,good mpg,bolt right in with out significant mods. Use all the money you save not buying all the nickle and dime stuff you are going to need for the LS swap.For your house or other things the truck needs. Only reason I said vortec was 1 piece rear seal and factory roller, you can get certain year B and D bodies with 1 piece seal and roller cam also. At the power level and MPGs you are wanting you probably should probably use the Vortec heads,or swap yours for some fast burns.

 

[Catbox]

Find a L-31 Vortec engine.
The short block will be a roller and that is what you want.

This is where we find them, both the blue and white Suburban were complete in the morning when we showed up.
Both engines came home with us that day.

You must be registered for see images attach

It sounds like you have some heads to use, but those may not have the needed accessory holes you might need.
But yes, you can strap whatever heads you want to them for the Gen 1 engine.
These aluminum heads are inexpensive and have been well researched on the interwebs and Youbstubes to make decent power.

You must be registered for see images attach

You can buy aluminum intakes that still have the Quadrajet mounting pad.
They are plentiful as I have a couple of them here.
One is a factory GM piece, I also have a an Edelbrock unit from the swapmeet.
Paint one to look stock, nobody will know it is there same with the alum heads.

I found this GM one in the junkyard for $40.
You can see that is has a square-bore adapter bolted on it.
I don't know how much better than a stock iron intake this one is, but even if they are the same there is the weight savings.

You must be registered for see images attach

You must be registered for see images attach

With the Vortec block you will need to run an electric fuel pump as the block is not machined to run a mechanical pump.
There are any number of ways to achieve this.
You can swap to the '87 tanks with in tank pumps or you can simply add a pump near the stock tanks.

With a fairly small cam you should be able to make 300 hp easily.
You are not the first one to build that particular engine combo, so find a recipe on the interweb and look into it.
Follow the build plan and you should get similar results.

 

[blakeasaurus]

Thanks all:

I'm really not interested in an LS swap. Way too much effort. As suggested, I would just buy a truck with an LS already in it if going that route. I am specially wanting to avoid all the wiring and computers and custom front end accessories and hoses and stuff that go along with such. All front end accessories work now, so I plan on keeping them.

The truck runs decent, but I do need to occasionally pass on 2 lanes, and the 305 makes this a bit too exiting sometimes (especially up hills). I live in the boonies, so there are a lot of 2 lanes

To clarify, the mpg is secondary to the additional scoot. Even if I get the exact same 15 mpg, I'd be happy with more passing power. But the goal is 20. I think 18-20 mpg is doable with a mild carbureted 350 and tall gears (if necessary).

I've got a 4WD 2011 Nissan Frontier V6 that only manages 20mpg on the best days - but it weighs about 500 lbs more than the Squarebody. This is my winter rig.

I already have the heads I got for a song, so just need a short block. Vortec blocks seems the way to go with 1 piece rear main and factory roller cam provisions.

May not even start this project until next winter since the house (and garage - with lift - yes - finally a lift) will take priority. I am content to not pass on 2 lanes until then.


Thanks again

 

[DoubleDingo]

Thanks all:

I'm really not interested in an LS swap. Way too much effort. As suggested, I would just buy a truck with an LS already in it if going that route. I am specially wanting to avoid all the wiring and computers and custom front end accessories and hoses and stuff that go along with such. All front end accessories work now, so I plan on keeping them.

The truck runs decent, but I do need to occasionally pass on 2 lanes, and the 305 makes this a bit too exiting sometimes (especially up hills). I live in the boonies, so there are a lot of 2 lanes

To clarify, the mpg is secondary to the additional scoot. Even if I get the exact same 15 mpg, I'd be happy with more passing power. But the goal is 20. I think 18-20 mpg is doable with a mild carbureted 350 and tall gears (if necessary).

I've got a 4WD 2011 Nissan Frontier V6 that only manages 20mpg on the best days - but it weighs about 500 lbs more than the Squarebody. This is my winter rig.

I already have the heads I got for a song, so just need a short block. Vortec blocks seems the way to go with 1 piece rear main and factory roller cam provisions.

May not even start this project until next winter since the house (and garage - with lift - yes - finally a lift) will take priority. I am content to not pass on 2 lanes until then.


Thanks again

I read your first post, and then the LS posts after by others and thought I misread something. Nope.

The truck turning 2,200 at 70 is really good. Others stated Vortec. That will get you additional ponies and the right cam you'll be pleased with the outcome. Just know, if you up the power, rebuild the transmission too, have heard horror stories of people not doing so and needing to rebuild it or find a replacement because it grenaded behind the extra power going through it.

Forget about 20 mpgs, not happening. Maybe 15 and only if you keep your foot out of it. I had a 65 C20 with stock 350, sm420 and 3.54 gears and it got 14-16 cruising 65, 2,200-ish rpms. 70 was 2,600. It was great on flats, but steep grades and the secondaries were open, which means major fuel consumption.

If it were me, I'd leave it alone like you're thinking, and build a decent 350, vortec or not, rebuild the transmission, leave the axle ratio alone, and run it.

We have a member on here that has a c20 with a 305 and 700r4 and I believe it has 3.42 gears, and he hauls heavy stuff all over the the mountains in Washington.

 

[Turbo4whl]

I got 2x 5.3 2008 cylinder deactivation turd engines,...if anyone wants cores that suck the money out of your wallet,...and make you loose head hair.

Here is the ad for you:
BOAT ANCHORS, FREE YOU HAUL me:

 

[xm20k]

20MPG at almost double the HP is not going to happen with a gen 1 small block, not carbureted at least. Most stock 350s in the squares get 13-15 give or take 1 or 2 at 160HP, at 300 you might just get double digits depending on how you drive.

Also, a 40+ year old stock Th350 is going to need a rebuild before tossing 300 plus Infront of it, a shift kit is only going to make any issues pop up faster as it hammers thru shifts with even more power/torque being applied.

The temp engine that was in mine while I built the 388 stroker was probably 350HP and the stock TH350 lasted maybe a month before it told me to go F myself and started slipping and howling luckily at that point My Powerglide was done and ready to go in.

 

[bucket]

When my '84 C10 still had the stock 305 in it, it was my daily driver and I kept a constant log of mpg. I averaged 14 mpg on a day to day basis, with mix of city, interstate and rural driving. On longer trips at 55-60 mph, I would get a solid 18 mpg. And that was with a th350 and 2.56 gearing.

I could very easily see a mild and efficiently built 350 acheiving similar mpg with the much better gearing combo of a 700r4 and a less doggy axle ratio.

 

[Ricko1966]

O.P. has a 700r4 buy an 1988 or later core to build and have waiting. By 88 they have most of the updates,better pump etc. If you can get a 90 up even better.

 

[goldpack]

just for wondering,... I wonder how hard it would be to put a LT1 350 into a 1986 pickup
(like out of a 1996, caddy/buick/olds/pontiac last of the RWD,...such could give them 25mpg on the sticker,...vs. the regular 350s of the period).

 

[bucket]

just for wondering,... I wonder how hard it would be to put a LT1 350 into a 1986 pickup
(like out of a 1996, caddy/buick/olds/pontiac last of the RWD,...such could give them 25mpg on the sticker,...vs. the regular 350s of the period).

Not hard as it literally bolts right in. It was a common hot rod swap in the mid to late 90's. I'd assume that there are still swap harnesses available. The best swap info will likely be best found in old magazines since LS swaps started to seriously gain in popularity about the same time that the internet also gained in popularity. But on the other hand, the internet is full of everything, so maybe I'm wrong about that.

Keep in mind that 25 mpg in a Buick doesn't mean 25 mpg in an old Chevy truck. A bathtub is more aerodynamic than a brick.