Towing with a 305 V8?

[75gmck25]

If you plan to change gears, check the specs carefully to make sure what will work with your current axle. Some axles have two different carrier assemblies, usually one for low gears (maybe 3.73, 4.10, 4.56) and one for higher gearing (2.73, 3.07, etc.).

 

[SirRobyn0]

@SirRobyn0 Thank you for joining the thread!
What is your opinion on swapping the rear gears? If you had a truck with 2.73 would you go for 3.73 or 4.10?
My trailer is a single axle with electric brakes, but I understand your concern about it being a 1/2 ton. My dad won't pull with less than a 3/4.

Your welcome. I would have been here sooner, but was out of town. What does your trailer weigh? And what do you think your heaviest average load will be?

So I've got 3.41 gears and they are not enough for towing. Keep in mind my tires are likely larger than the ones on your truck do to mine being a 3/4 ton. And tire size makes a difference in RPM. I want to swap to 4.10's, and I've thought about going to 4.56's. But in a C10 3.73's might be good middle ground. What transmission do you have?

@SirRobyn0 So you would advise that I keep the ESC and EGR? I had been planning on deleting them, but from what I gather that might be setting up for trouble.

Do not dump the EGR valve, the EGR lowers combustion chamber temps by introducing exhaust gas which because it's already been though the combustion chamber it can't be burned again. By lowering the combustion chamber temps it reduces pinging. If you want to try running the truck with out the ESC, by or make one of these. https://www.ebay.com/itm/3337927733...vNKdI4dYY0lZRaxuLjTFftSUGIyXY9ThoCB9gQAvD_BwE Then you can bypass the ESC and drive it around and see if you like how it behaves without tearing it all out, potentially having to reinstall it all. But my advice is if the ESC functional and the truck runs good, leave well enough alone.

What about If I were to replace my Qjet with a Holley? All of them say no EGR? Would that pose the same problem with timing?
I haven't even looked at my timing yet (still need to buy a light), but I intend to whether on the Qjet or Holley.

Doesn't matter on a 305. A non-EGR carburetor is just going to come with slightly richer main jets than a EGR carburetor would have. But a stock 80's high compression 305 cannot live without an EGR regardless of carburetor. Also GM picked the Q-jet for their engines because they are a really great carburetor albeit trickier to rebuild.

Just watched a few YouTubes on replacing Ring and Pinion gears. Looks a little more complex than I was thinking. In your Guys opinion, Is this something I should be capable of doing? or is this something requiring a lot of expertise?

How much time do you have? I've never done one myself, but it doesn't look hard to me, it just looks like it would take all day.....

This is the truth. It’s all user and engine condition dependent. I have followed your saga with ESC and tried to put mine back to stock and just found that it ran far worse with the esc restored. I run MOST everything stock except ESC, including my timing at stock set point (4 BTDC iirc) and the truck runs great for me FOR HOW I USE IT. EDIT: I DO NOT HAVE THE AIR PUMP SO I LIED ABOUT EVERYTHING STOCK... That means that it’s almost never under load because I just putter around mostly. When I do load anything into it I usually note some pinging right before downshift.

Mine is a 2.73 with 700R4. That means it already hunts around for the right gear plenty if I leave it in OD.

One note of caution to the OP: when I got my truck, the prior owner had completely hacked up the vacuum tubes because of “clutter” and “emissions.” What he had also done was leave a few vacuum leaks and disconnected some vital non emissions functions. Most important was the 700r4 vacuum kick down. He wondered why the truck surged and wouldn’t kick down (“that’s all broken”) Not everything operated by the vacuum lines is “emissions crap.”

Be logical in modding the engine. The 305 is a very different animal from any other SBC and definitely not comparable to a BBC when it comes to how much support the engine needs to run right.

@Trucksareforwork gives good advise.

 

[Velder]

@SirRobyn0, My trailer weighs 2,000lbs empty and I am estimating that it will be about 5k loaded. I put a 6k axle on it, but I think it unlikely that I will ever load it that heavy. It is my welding rig, so it will have a pretty much always be fully loaded.
My wheels are 15in.
Thank you for the explanation on the EGR and ESC that really clears things up. I am going to leave both of them alone and try rebuilding my Qjet again, see if I can make it work.
I can definitely devote a few days to swaping the gears, just wanted to be sure that I wasn't being arrogant thinking I could do it.
At this point I will Probably try to find a heavier duty truck for my main driver, and set my square body up as a backup.

 

[Ricko1966]

Didn't the early 305s from the '70s not have ESC in the first place? Was there really enough substantial differences to make an '80s 305 ESC dependent?

The early 305s had different heads and way less compression. The early ones run great with a performer, a holley,headers,and a small cam. I know this is going to sound crazy, but I have wondered about this. A few months ago I was looking for an 8.5 10 bolt for a 71/72 A body,lots of people said they didn't exist others said 71/72 was a crap shot you may get a 8.2 or an 8.5 you had to pull the cover to verify. Well I found an 8.5 I have often wondered if some of the later 305s were built using up the early 305 stock. That would be one explanation as to why so.e run great without esc and others run terrible. I have no proof of this,just a thought. For some reason it seems to me the ones that have problems are the one piece seal 305s.

 

[Bextreme04]

That is the before rebuild picture, here is the After.

You must be registered for see images attach

I bought a Hi-Grade brand kit, and followed the directions (what little there were). I think there might be a defect in the casting, that it doesn't fully compress the gasket. But yes I bought a rebuild Kit

The air horn is bent from overtightening the 1/2" bolts that hold the carb down. It is a common problem. When you overtighten those big bolts it pulls the outer ends down and consequently pushes the air horn up in the middle and causes those leaks. It is likely also leaking internally(both fuel into the primaries and air into the internal circuits). You should bend it back mostly flat(as close as possible) when doing a rebuild and then take special care to not overtighten the bolts when bolting it back onto the engine.

Rebuild kits should be bought for the specific part number of the unit from a reputable quadrajet expert like Cliff https://cliffshighperformance.com/ or quadrajetparts.com. They will include a sheet in the rebuild kit that contains all of the specific settings and adjustments for your specific carb number and application. This includes float level, accelerator pump hole and height measurements, choke settings, etc...

 

[Turbo4whl]

Didn't the early 305s from the '70s not have ESC in the first place? Was there really enough substantial differences to make an '80s 305 ESC dependent?

Lower compression in the early 305s. Early 305s were 8.5:1. Later ones were 9.5:1. Believe that made the difference.

Geoff has the answer about the need for the ESC. All this driven by cafe numbers.

As some of you know I boosted my 1982 305. Here is some info on the many 305s:

https://www.vehiclehistory.com/articles/chevrolets-305-engine

 

[Ricko1966]

Just spit balling here, not arguing...

My '84 C10 had the original ESC 305 when I got the truck. I drove it everyday and recorded the mileage on every tank. After a while, I started having a bunch of troubles with the quadrajet, so I put on a 650 Holley that I had on hand. At that time, I also removed all the vacuum hoses and temp switches... got it down to a vacuum advance and a PCV hose. After a while longer, the pickup coil in the dizzy started to crap the bed, so in went a standard HEI. Pretty sure it was a Street Fire unit, but I don't remember now. I may have just stuck in a random HEI unit.

But anyway, the truck always ran great, didn't ping and the mileage was always the same. With a mix of city and highway, my average was 14.5 mpg. Best tanks were on long drives at 55 mph (no OD, 2.56:1 gear) which 18.5mpg could be achieved. The carb/dizzy situation didn't seem to make a difference.

Look at what I found today,this deal with why do some trucks do fine without esc and others don't is really bothering me.Someplaces list a 305 c10 engine kit 81-84 but nothing 85 up, then I found this that shows a different kit 85,86 and another 87 up. Possibly just a different gasket set but I'd think if that was the only change everyone would list 85 up kits IDK things that make you go hmmm.

 

[Ricko1966]

xc_hide_links_from_guests_guests_error_hide_media

 

[SquareRoot]

Six pages on the towing capacity of the lowly 305. Impressive. That's like Prime Time for Rosie o Donnell.

 

[CheemsK1500]

Look at what I found today,this deal with why do some trucks do fine without esc and others don't is really bothering me.Someplaces list a 305 c10 engine kit 81-84 but nothing 85 up, then I found this that shows a different kit 85,86 and another 87 up. Possibly just a different gasket set but I'd think if that was the only change everyone would list 85 up kits IDK things that make you go hmmm.

I think SirRobyn0 had a decent theory about wear and manufacturing variations. Whether an ESC delete helps or hurts an engine likely depends on the particular engine in question. I'm looking hard at the modern MSD systems because of the programming aspect. The '80s/'90s ESC is built for a factory fresh stock 305, so a worn or modified 305 could cause conflict. A programmable ESC system could allow someone to tailor the system to their particular engine's needs, rather than be stuck at a fixed factory setting.

 

[CheemsK1500]

Six pages on the towing capacity of the lowly 305. Impressive. That's like Prime Time for Rosie o Donnell.

To be fair, much of this thread is just us discussing advantages and disadvantages of ESC systems. Most of us here trust a 305 to tow as much as we'd trust any other 40 year old small block.

 

[SquareRoot]

To be fair, much of this thread is just us discussing advantages and disadvantages of ESC systems. Most of us here trust a 305 to tow as much as we'd trust any other 40 year old small block.

Advantages?

 

[SquareRoot]

"Give me a lever long enough and a fulcrum on which to place it, and I shall move the world". Not mine.

 

[Ricko1966]

I think SirRobyn0 had a decent theory about wear and manufacturing variations. Whether an ESC delete helps or hurts an engine likely depends on the particular engine in question. I'm looking hard at the modern MSD systems because of the programming aspect. The '80s/'90s ESC is built for a factory fresh stock 305, so a worn or modified 305 could cause conflict. A programmable ESC system could allow someone to tailor the system to their particular engine's needs, rather than be stuck at a fixed factory setting.

The problem with the msd is it doesn't have provisions for knock retard,just advance curves,you can really tailor the curve,but to the best of my knowledge you have to adapt,the gm esc to the msd to have spark knock retard,or use a spark knock retard from J&S safegaurd or use msd and proflow,with a spark knock module. Msd does make a knock sensor kit but it just lights a light so you know you have knock. I think I could make that work on a GM hei,as a home brew knock sensor ignition. That kit, trigger a relay instead of a light,the relay grounds the 5th pin on a d1941 ignition module but it would still be gm hei. Haltech and megasquirt support knock sensor also,but none of those options are really practical.

 

[Turbo4whl]

"Give me a lever long enough and a fulcrum on which to place it, and I shall move the world". Not mine.

-Archimedes. This is a quote even older than me.