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Old 03-13-2019, 09:56 PM   #1
Chris_oz
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Towing with and modifying my C20 ???

Hi all,

I am at a cross-roads with my truck. I am not sure whether to modify it to make it what I thought I wanted, or drive it as it is, with upgrades / improvements as I go along.
The more I drive it as is, the more I like it.

My initial plan was to set it up for towing our caravan, which is a 206 full size van that weighs just on 4500lb. I currently tow it with a 2yr old Ford crew cab Ranger.
I want the Chevy to tow it so I may be able to sell the Ford, and save me some money.

Mine is a 1970 C20 longhorn, 255hp 350, 4 speed (SM465), stock Eaton HD52 rear end with 4.56:1 ratio.
Manual steer, power drums, HD front and rear springs, front and rear sway bars, A/C.

Truck is all stock other than electronic ignition, it has 72K on the speedo and runs like a new one, she blows a little smoke on start up when cold, but cleans up when warm.
It really does run well, perfect starting, hot and cold, returns 14.5-15mpg on country roads / highway if I keep it at 60mph.

I had planned on doing the following.

Edelbrock or Patriot 64cc alloy heads.
Comp XE268H cam and suitable lifters.
Edelbrock 2601 Performer Airgap Q-jet manifold. ( I have this new in box at home)
2.5 ramhorns.
2.5 twin with H pipe system
Carb and ignition as required.
Built 4L80E or 4L85E set up for towing with a 2000-2200 rpm lock-up stall

Out here in Australia the above will cost just on $7,000 + transmission controller + bottom end freshen up.

Unfortunately my job is changing, which means a large drop in take home pay (the other benefits I hope will make up for it).
This leaves me in a spot where my spare play money will dry up to a trickle soon, so I will not have the cash to do all that I wanted to do at once, maybe not at all.

I dont have a tow hitch yet, I need to build one as no-one sells one out here and I cant find one for sale out here.
I am going to fit my electric brake controller (legal requirement out here for trailers over 1500lb weight)
The vans brakes are strong, they will pull the van and current car up if required. It has 4 wheel electric drums (all new)
The trucks brakes are ALL NEW, whole system, its working fine other than a rear wheel that is locking up on me, I didnt do the work and need to check it out.

I do have a new set of discs with 2.5 drop spindles, master, booster, prop valve if required, but I would rather keep it stock height, as it is high in the rear already.

Now to my questions.

Do I need to modify it to tow with?
I think I already know the answer to my questions, just looking for knowledgeable opinions and options

I know in the past plenty of people towed with these trucks, but just how practical are they as an occasional tow vehicle?
Any thoughts or feedback welcome, sorry for the long post.

Cheers
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Old 03-14-2019, 12:23 AM   #2
Steeveedee
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Re: Towing with and modifying my C20 ???

As far as pulling is concerned, you are good. A 4.56 axle isn't going to give you any real speed, as you know, but it'll get you up some pretty steep hills. Braking, you're good with stock if the trailer's brakes work OK. The front discs are a great improvement for rainy weather. As far as the hitch, I have a load-equalizing hitch that transfers some of the weight forward. This actually raises the rear of the truck a bit, but helps the handling quite a bit. I eventually want to put on a rear stabilizer, because the new tires (Firestone Transforce) have more oversteer than the old Michelin tires that were on the truck before, even with the rear tires 10 PSI higher pressure. And that's without the travel trailer (I guess that's what you call a caravan, there?). My FiL had a '63 Chevy truck before he had this one and towed a 4000 pound trailer with a 283 CI engine, and 3OTT. It had serious limitations in the Rocky Mountains, which is why he bought what is now his daughter's and my truck with the setup you see in my signature.

I think that you'll be fine with it as-is. I'd be carefully with the speed parts potentially making it less of a tow vehicle. I haven't researched the parts you are using, though.
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Old 03-14-2019, 12:45 AM   #3
kwmech
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Re: Towing with and modifying my C20 ???

If you stick with a larger single exhaust--say the 2.5'' into a single 3'' you will be happier than the H pipe. Second, you will like the 4L80 as a great improvement, although you will lose some of the slowing down of the manual, but you gain the overdrive with the 4.56 gearing you have. Get a heavy duty --stock--convertor, you don't need a stall convertor in the truck with 4.56 gears. If the drums are all done correctly and adjusted you will have plenty of braking. I am still using the 4wheel drums on my 68 and never had a stopping issue when fully loaded with a pallet of cement block (3200#s) plus dragging a trailer occasionally.
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Old 03-14-2019, 06:27 AM   #4
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Re: Towing with and modifying my C20 ???

I suggest that you put a good transmission cooler on it when you switch to an auto.
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Old 03-14-2019, 08:17 AM   #5
Mike C
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Re: Towing with and modifying my C20 ???

I agree with the exhaust comments above and it will tow good the way its setup.

The first thing I would do (and did on my 70 GMC C2500) is convert to disc brakes and add a receiver hitch. Sell or trade the drop spindles for stock height. If you had coils in the back Id say drop it and add 4 lowering rear spring and load assist air bags. On my leaf spring truck I kept stock height front and an 1 lowering shackle in the rear to cut the rake in half. Mine was a 402/TH400 and I had always planned to swap in an SM465....

I am not a fan of the Comp extreme energy cams and think that I would want a cam that had no more than 218 degrees intake duration at .050 which would be the regular 268 cam, and for towing I think the 260 is better which is 212 @ .050 if memory serves.

Exhaust, intake, and ignition mods will all make it better.
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Old 03-14-2019, 10:44 AM   #6
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Re: Towing with and modifying my C20 ???

Quote:
Originally Posted by Mike C View Post
I agree with the exhaust comments above and it will tow good the way it’s setup.

If you had coils in the back I’d say drop it and add 4” lowering rear spring and load assist air bags.
All Longhorns were 2.5'' wide leafs---unless I misinterpreted your comment
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Old 03-14-2019, 01:35 PM   #7
Chris_oz
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Re: Towing with and modifying my C20 ???

Hi all,

Thanks for the replies.

I have made a start on the tow hitch, I hope to have it on in next 2 weeks, along with the trailer wiring and electric brake controller so I can do a few test runs and see how it goes.

If i am happy with how it tows performance wise, I will sell the drop spindles and buy some stock height ones, lower the rear a couple of inches to level it out and drive it.

If not, I will keep my Ford and slowly modify this with a 2-5 drop, disc brakes and 485LE, then mod the engine as I can afford to or go with the original plan of a blue print 383 with roller cam. Just need some funds.

Thanks
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Old 03-15-2019, 01:17 AM   #8
PepperTreeGarage
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Re: Towing with and modifying my C20 ???

1972 C20 Custom Camper. It will be tow and haul ready when finished. 383, 4l80e trans, Dana 60 with posi and 3.73 gears. Air bag assist rear leaf spring suspension. Just saying these trucks have a lot of potential. This C20 carried an 11' Cab Over Camper from 1972-2011 and pulled a small fishing boat. They're built to work.
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Old 03-15-2019, 08:14 AM   #9
Mike C
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Re: Towing with and modifying my C20 ???

Quote:
Originally Posted by kwmech View Post
All Longhorns were 2.5'' wide leafs---unless I misinterpreted your comment
You did. Or I should say I wasnt very clear on my statement. I meant if he had a regular C20 with coils then use the drop spindles and a drop spring but with the Longhorn, stock spindles with discs and maybe a 1 drop shackle in the rear.
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