Timing on my first truck

bluethunder

Junior Member
Location
texas
I recently got my first truck! A 1986 Chevrolet K20 4x4 with a 350 engine. I was wondering if someone knows, or can tell me where to find what degree to set my timing. Any help would be greatly appreciated.
 

75

PlowSite.com Addict
Welcome to the forum, and congrats on your "new" truck! (I bought my first truck IN '86, mind you it was a '75 so it wasn't new by any means............................ Still have it though!)

Best investment you can make right now is a good service manual(s) for your truck, Haynes & Chiltons come to mind, look for manuals covering 1973 - 1987 Chev/GMC full size pickups.

Without MY manual handy I'm guessing here, but I think 6 to 8 degrees BTDC on the timing is fairly close for your 350.
 

Chuck Smith

2000 Club Member
Location
NJ
Rob is about right. Anywhere from 4 - 8. Look at the emissions decal under the hood. You might still be able to read the timing info on it.

~Chuck
 
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bluethunder

Junior Member
Location
texas
thanks

I'll try it out and see what it runs at best. Thanks for the replys.
I know where to come to now if I need some help!
 
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bluethunder

Junior Member
Location
texas
oh yeah about the emissions decal, the emissions decal on 3/4 ton trucks like mine are on the air cleaner. When I bought the truck it had an aftermarket air cleaner on it.

Thanks again
 

75

PlowSite.com Addict
Don't forget to get those manuals - they're a b-i-g help when looking for that sort of info.

What's the overall engine condition like? Definitely check out your timing, but also consider a compression or leak-down test on the engine so you have an idea of general engine health.

Fuel filter(s) are another thing that gets overlooked a lot when something doesn't seem to be running quite right (voice of experience here............... :rolleyes: ) so don't forget them either.

Keep us posted on what you find!
 
Hey Chuck:

My '86 C20 crew cab has the two decals on the air cleaner. Unfortunately, they are quite tattered and I can't read the decal's part numbers anymore.

Does anyone know a resource available where I can find out which part numbers I need? About 80% of the decals is still readable, so I think I'd be able to match it up if I could see some pictures of complete decals.

My local Chevrolet dealers were of little help this time.

Thanks,

DJS
 
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bluethunder

Junior Member
Location
texas
:)

The engine in my truck runs great. It starts quick. Power leaves a little to be desired. Of course it was only rated at 160 hp from the factory. Me and my dad did a compression test and it tested out good. It has an Edelbrock Performer Carburator and intake. I also put MSD plug wires on it. Me and my dad are either going to drop a crate engine or rebuild the 350 for some more hp. Also I'm going to save up and get a gear set for the TH400 in my truck to lower first and second gear for better low end power. Also change out the 4.10's and exchange them with 4.56 When I do that I'm junking the gov lock and puttin either a Auburn Posi or Detroit Locker even though I'm going to have to buy another carrior. The front axle is going to be locked up with a spool. I figure it won't wear out and its very hard to break. That's my plans for it right now. You can go

www.geocities.com/omy4hi

to see it.
 

75

PlowSite.com Addict
Looks sharp!

Just thinking out loud here, if your engine seems to be in good health leave it alone for now, and make the changes in gearing you're talking about. That should make a noticeable difference - at my work, we have a nice old '65 Chevy 5-ton (boss likes his old trucks - so do I! :D ) with a 292 six-banger. Truck has a max GVW of 21,000 pounds, that six will move it. Gearing makes a difference!

Seeing as you mention 4.56's and locking the front end, I'm going to assume that your truck is going to be more of an off-road rig and not spend much time on the pavement? 'Cause with that gearing and locker(s) I don't think it be nearly as happy on the road as off.

What about just keeping the 4.10's you have now?

If you do decide to swap ratios, you might be better off changing the whole axle(s) complete. And if you're going to go THAT far look for a Dana 60 for the front - that will mean using a K30/35 for a donor truck.

Just some ideas to throw into the ring.


BTW, whereabouts in Texas are you at? I have relatives (Grandmother, aunt & cousins) in the Ft Worth area.
 
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bluethunder

Junior Member
Location
texas
GAS Guzzler?

75 I live in the Fort Bend area. My truck will be seeing a lot of mud. The spool in the front axle will not play a role in road driving because I have manual hubs in the front. But the locker might. But I'll be only driving to school. My dad took the truck to his shop today. He drove about 24 miles total. The guage read a little over 3/4 of a tank before he left and when he got back it was under a 1/4 of a tank. I really don't trust the guage but you never know?I hope the guage is wrong. I plan on dumping the 10 bolt in th front for a Dana 60. I just ordered cab corners for my truck. The ones on my truck are rusted out. Then my uncle is going to repaint it. I'm waiten to see how the trucks rides right now. We had 35/15 Swampers on it. They were bald so we put some 36inch/12.5 Goodyear Wrangler mlitary tires on it. They were off a hummer. My dad says it rides a lot smoother. Well I better go to sleep I have to start school again tomorrow.
 

75

PlowSite.com Addict
OK, I found ya - Dad went to med school in Galveston l-o-n-g time ago. Granddaddy worked for LTV aircraft in Ft Worth, also l-o-n-g time ago!

1/2 a tank of juice to go 24 miles sounds like a LOT of fuel, but I never assume the gauge is accurate either. Best thing to do is fill up, mark the mileage, next time you fill up check the mileage & do the math comparing the miles driven to the gallons used. And there's a good chance you'll come out under the 10 mpg figure even if everything is well - I figure my dually is lucky to get 10 mpg and it's a 2wd!

Check to see if your choke is sticking partially on, the rich mixture caused by that can do a number on fuel mileage. So can dragging brakes (I'm thinking the parking brake especially)

If you plan on putting a Dana 60 up front anyway, as I said in the earlier post try for a complete donor truck if at all possible. That way you can swap the axles as complete units and you know the gear ratio is the same front & rear.

Couldn't tell 100% from the pic, is your truck a "light" (semi-floating rear axle) or "heavy" (full-floater rear axle, identifiable by the big hub that sticks out about 3" beyond the rim) 3/4 ton?
 
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bluethunder

Junior Member
Location
texas
semi floating

It's a 3/4 ton. It has the 14 bolt c clip rear end. Its not a full floater. It has the 9.5" ring gear. Today me and my dad adjusted the floats and put an off road kit in the carb. I'll see how much of a diffrence it makes. I think a donor truck will be a good idea for the axles. Well I bet ter get some sleep. Later
 

Chuck Smith

2000 Club Member
Location
NJ
I can tell you this. My 77 Chevy has a 400 small block, Holley 600cfm carb, with vacuum secondaries, and an Edelbrock Performer intake, headers, accel distributor, 268 cam, and more. It has a TH 350 trans, 14 bolt full floater rear, with 4.11's in it. I get about 9 - 12 MPG city, especially with hills. Oh, and the truck has 36" tires on it.
The best mileage I ever got was on a highway trip. All flat ground. I got 17 MPG on that trip. I have never even come close to it since.

My 80 GMC has a bone stock 350, with a tiny 2 barrel carb. It has a TH 350 trans, and the 14 bolt full floater rear axle, with 4.11's in it. It has somewhat worn down 33" Cooper tires on it. Highway and city with hills, that truck too gets 9 - 12 MPG.

I've talked to many people with Blazers, Suburbans, k/10's, and 20, both GMC and Chevy. Guess what? Everyone complains about the mileage. Keep in mind, this is including years (81 - 87) with the TH 700 O.D. trans in them too, and all different gear ratios. Computer equipped vehicles, and non computer vehicles. The mileage is anywhere from 9 - 14 MPG. There's really just not much you can do, except keep a light foot.

That was one of the nice things about the 4 barrel Rochester. You could lock out the secondaries on the carb. When I bought my 77 used, the guy had the secondaries locked on the carb, to save on gas, and to hold back on power when employees were driving the truck.

One other thing comes to mind. In 1986, GM used the TH 700R4 in 1/2 and 3/4 ton trucks. Also, the NP 208 transfer case (with the aluminum housing). Someone swapped in that TH400 trans. What transfer case is it mated to now?


~Chuck
 

plowking35

2000 Club Member
Location
SE CT
Chuck there were some 86 trucks with the TH400 and 208 case in 3/4 ton P/U. My guess is that was only in the 8600 gvw trucks tho. My 86 that I am building had that combo till I swapped in the TH400 with 205 case.
Dino
 
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bluethunder

Junior Member
Location
texas
I love my truck

Chuck my truck came with the TH400 and NP 208 from the factory.Well I'll try to keep a light foot. TRY lol All I know is I love my truck.
 
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