A few general questions.

[CG]

I bought my 71K20 from my neighbor, the original owner. He has since moved away so I cant ask him this stuff.

He ordered it special with all the extra heavy duty springs and helper springs etc etc. It has a locker rear end with some pretty low gearing. And 350 with a 4spd. This truck was used on his ranch when he lived in Colorado. He also used it to pull a fifth wheel horse trailer and a camping style trailer.

I love this truck, its fun to drive. And I think it will haul most anything. Ive loaded this baby up with some pretty heavy stuff and it doesn't squat at all. But it sure is a slug when it has much of a load if I hit any kind of a grade. The engine was rebuilt not that long ago. Im curious, is this just the way they are? How could he have used it to pull fifth wheels with it being such a dog on grades? With the rear gears it really winds out If I shift down to third.

I really havent made any plans for this thing other than to change some cosmetic type stuff to make it more my style. I like the fact that its old and has a bunch of quirks...but who knows maybe someday...

[89 crew]

One thing to remember is the speed limit was 55 till a few years ago. most trucks I have seen will run 45 in second. Is that enough difference to cover your problem?

[CG]

If Im going up a grade on a side type road (not freeway) it really drags down. I cant imagine going over the pass in this thing...LOL i just noticed you are in Kansas...you dont have Mt passes. Maybe I should move there. =)

If I dropped this thing down to second and tried to go 45 it would peg the tac.

Im thinking if I want it to be more street civilized Im going to have to do some serious upgrades.

[jrdv]

My 72 k20 is the same way. It has about 20,000 mi on a stock rebuild and 373 gears. It just doesn't have the power for a heavy load and hiway speeds. We have been spoiled by diesels!!
No power is the reason I bought a 383 to put in it--hopefully in the next couple of months. I think a 5 speed would make a huge difference when towing.

john

[CG]

Originally Posted by jrdv

My 72 k20 is the same way. It has about 20,000 mi on a stock rebuild and 373 gears. It just doesn't have the power for a heavy load and hiway speeds. We have been spoiled by diesels!!
No power is the reason I bought a 383 to put in it--hopefully in the next couple of months. I think a 5 speed would make a huge difference when towing.

john

This thing has 4 something gears. I dont see how he could have used it to pull a camping fifth wheel without being passed by kids on skateboards.

[1969K10]

Makes me wonder if your vacuum advance or something isn't doing its job. I've got 3.73 rear on 33" tall tires. Pulling another full size '68PU back from Boston, I had to down shift into 3rd for a small handful of the long/steep grades. My temp would rise too much. I since found out that my timing belt had a mind of its own, and my timing was all over the place...

[OLDCHEV4X4]

Yea. Check to see that the vacuum advance is working.

[CG]

So if it drives around every where else (levelish ground) but bogs down on hills it could be vacuum advance problem. Ill look into that.

[Blazer1970]

Originally Posted by 89 crew

One thing to remember is the speed limit was 55 till a few years ago. most trucks I have seen will run 45 in second. Is that enough difference to cover your problem?

They changed the speed limit to 55 during the mid '70s (Carter administration IIRC). Before that, highway speed limits were 65 - 70 mph just like they are today.

[70rs/ss]

It will bog under a load if the timing is off, the vacume advance could be it, on a side note there is a pretty wide ratio between 3 and 4. If you are going to drive it a nice NV4500 will cover you everywhere, down low and up high. I think a stockish 350 was like 190hp or something? He probably did it, but it was nice and slow. A 383 would wake it up, or you could go through the 350 and do a cam, heads (vortec) intake, carb, HEI!! and the 350 will be as good as it will get. Now that I say HEI, does it have points? If so I'd put an HEI first and see how that helps it, cause the bumps on a point distrubutor wear down over time and higher rpms can cause the points to float (not necessarily pop but run like a dog?) I new one can be had from skip white for like $50, worth a shot.

[CG]

It has an HEI. It doesnt miss or stumble or anything like that. Its just a dog going up the hills.

Im not ready to really put anything into this right now, too many other things going on. I do have an extra big block and a 4x4 auto trans set up (350) laying around.

Thanks for the info guys. Now that I have a garage to work on my stuff instead of the dirty cold barn maybe I will get to more things on my rides instead of just dreaming about em.

[Billla]

Could be a number of different things - I'd treat it as a standard tune-up opportunity...

Mark, I'm around this weekend if you want to do some troubleshooting

[Critter]

Originally Posted by CG

I do have an extra big block and a 4x4 auto trans set up (350) laying around.

A big block is always a good remedy for not having enough power! That's my vote. Seriously, timing or low compression could be causing your lack of torque. Once you have checked the regular tune up stuff I would suggest running a compression check on all cyclinders. Its easy to do and tells you alot about your engine.

[CG]

Originally Posted by Billla

Could be a number of different things - I'd treat it as a standard tune-up opportunity...

Mark, I'm around this weekend if you want to do some troubleshooting

Thanks Bill. Weekends full though. Trying to finish up the plumbing on the kitchen remodel. And Im supposed to be getting my garage wired up on Sunday. I do need to pick your brain though about 350 I have stashed away when I get a few extra minutes.

[Billla]

You could always drop it off

Open any time for the 350 discussion.

[LONGHAIR]

I since found out that my timing belt had a mind of its own, and my timing was all over the place...

????

[Billla]

Originally Posted by LONGHAIR

????

Slack in the timing chain can cause significant variation in timing, as can too much free play in the distributor shaft.

[LONGHAIR]

I guess the significance was "belt"?

[Dean]

There must be something wrong. My 71 has the original 350, 4.56 gears, locker back, posi front with 35" tires. My 72 has a ZZ4 350, 4.11 gears, locker back and 35" tires. They both pull excellant even up hills. The stock 350 has more low end torque than the ZZ4 but when you keep the RPMs up it does better than the other.

[Billla]

Originally Posted by LONGHAIR

I guess the significance was "belt"?

Whups, right you are sir - I totally translated that in my head to "chain".

[dinotruck68]

not tryin to hijack the thread but my 68 k10 kinda has that problem to, its got a 305 v8 and an sm465 trans and 33's i dont know the gearing tho?
but 2nd an 3rd gear pull hard and can force u into the seat but as soon as i put it in 4th the truck (excuse my language) has no balls at all, in fact it goes about 5 mph slower than 3rd
i dont get it??

[LONGHAIR]

but 2nd an 3rd gear pull hard and can force u into the seat but as soon as i put it in 4th the truck (excuse my language) has no balls at all, in fact it goes about 5 mph slower than 3rd
i dont get it??

People usually compain about the drop from 2nd to 3rd because it is over a 2-1 drop.
1st = 6.55
2nd= 3.58
3rd= 1.57
4th= 1.00

I would say that your problem is a combination of a "slow shifting" truck transmission and a "low torque/small displacement" engine.

[dinotruck68]

its not from 2nd to 3rd its from 3rd to 4th where i hav the problem