Thread: My 1984 K10 - LM7 swap!!

Okay, I know this is Grand Prix Forums, but I figured some of you guys might enjoy seeing something that isn't a w-body. So, here's the story of my 1984 K10...

My grandpa bought this truck brand new from a dealership in Grand Rapids, MI. Being a GM employee at the time, he would have nothing else. It was his daily driver for many years. Pulled a camping trailer to the campground every summer, and after retirement, it's what he and my grandma drove to Florida for the winter. That's the reason it has over 457,000 miles on it. He pulled the original 305 somewhere around the ten year mark and replaced with a 350 that he built. Best guess is, the current motor has over 350,000 miles on it. Still holds 40 psi of oil while cruising. Plenty of miles left in it.

Time passed by, and eventually grandpa was no longer able to drive. Rather than sell it, he chose to pass it on to my uncle Bob. From what I understand, he only used it occasionally. Mostly to pull a boat to the water. Eventually Bob upgraded to a larger boat that just stayed in the water. This left him with very little use for the truck. I guess just letting it set didn't sit well with him. So he offered it to me, on one condition; I could never sell it. It had to stay in the family. Considering I've got two rambunctious little boys, it shouldn't be hard to find someone willing to take it.

Of course I was all over that deal! Only one problem... I live in Tucson and the truck was in Grand Rapids. For you guys without Google, that's almost 1900 miles away. Shipping that far is crazy expensive, and I couldn't really take a week off of work to fly out, then drive it back. Plans stalled.... Until....

My father in law, (the guy with the mint silver mist GP that I built a trans for) told me he bought a utility trailer in Michigan, but didn't have any way to get it home. Light bulb! Long story short, he drove his Cadillac to Michigan, sold it, then drove my truck and his trailer back to Tucson. The plan was perfect. The execution was less that perfect though.

About 3/4 of the way here, he started to have trouble. Total loss of power after about 1-1/2 hours of driving. Not entirely sure what the problem was, but he stopped at a garage and they put on a new cap, rotor, coil, ICM and PCV valve. It was better, but still not perfect. Keep in mind, it was over 100° for most of the drive, and the altitude changed almost 7000ft between Grand Rapids and Santé Fe. I'd be surprised if there wasn't any issues. Anyhow, he limped it the rest of the way, and it now rests in Tucson. I plan to get it all dialed in.

Here she sits in my parents green front yard, prior to the 1900 mile drive


And fresh off the highway


I did manage to get it washed yesterday. There was more than a little brake dust on them old rally wheels


Next step is doing something about this mess


I got the first layer of grime off with about a half gallon of Super Clean. It's a little better now, but we still have a long way to go.

It was at least clean enough for me to climb in there and check the timing and idle A/F ratio. Timing was good a 6°. A/F was way off (I think). Right (passenger) side was out 1 turn, and left side (drivers) was out 2-1/2. I set them both at 1-1/2 turns and took it for a quick spin. Ran good. At least as good as it did before, and now it's not pig rich. I'm probably lean right now, but I can play with it more after I pass emissions. That change plus the cat I'm going to clamp in should get me through.

So that's where it's at right now.

Here's my plan with it in order of priority.
Most important, get it past emissions. Kind of important to get it registered.
Headers and true duals. The single 2-1/4" pipe isn't doing it for me. I need that V8 rumble.
Maybe, a set of junkyard vortec heads, intake, and Edelbrock carb. Considering the cost of a pair of heads, I may just grab an entire vortec 5.7 and re-gasket it. We will see.
Way down the road, I see an LS swap. I really like the idea of computer controlled reliability and consistency. Who knows, maybe there will be something better by then.

Stay tuned for regular updates and progress pics. Special thanks to my uncle Bob for turning a simple truck into a family treasure!

Yes very nice! She cleans up nice!

Great story and good luck with the truck! Don't make it too fast cause one of your kids will be drivng it one day!

Sent from my SPH-L720 using Tapatalk

Thanks guys. I'm starting to get into the swing of this thing. I dumped a can of SeaFoam in it this afternoon, then drove it up to the parts store for some oil and a filter. I'm sure the entire neighborhood was thrilled with my cloud. I'm not sure how my father in law drove this thing for that long. It rides like an absolute brick. 4x4 trucks have come a long way, as far as ride quality is concerned. I love it, but it's not for everyone.

I won't have any time to mess with it tomorrow, but I have a list of things to do on Friday. Going to change the oil, and put the new plus and wires in. The catalytic converter should be here by then, so I will try to get that clamped in also. Then, time permitting, I'll drive it into town to get the emissions re-tested. If it passes, I can get my Arizona plate!

Hoping that doesn't take too long. Have to get back in time to go to the gun shop with my brother in law. They're having a big sale, and I'm looking for a new carry gun. Friday should be a good day.

Forgot to mention, I got a chance to clean out the cab a little. Looks like my grandpa was a huge fan of Hank Williams. At least 3 of his CD's, and one of Dolly Parton, Loretta Lynn Tammy Wynette.

Must have been a pool shark too. Found 2 boxes of cue chalk and some pictures of him and his retirement buddies playing. Who knew?!

I used to have an '85 K5!! That thing was awesome. Because of the 700r4, it had a moderately tall gear out back. You could do one wheel burnouts all day long! Talk about wanting to roll over. That high center of gravity and short wheel base.... How I didn't wreck that thing, I'll never know!

I'm not convinced the performance of an LT1 justifies the premium price tag. The engine swap is just a pipe dream for now. That's going to be a long time from now. I guess, unless the current motor pops...

The emissions test isn't all bad. It's kind of important here in the southwest climate I guess. Something about the intense sun. (?) Plus, without the test, I wouldn't have known how far out the current carb tune was. The real problem will be if I can't tune it well enough to pass. I think the standards for an '84 pickup are pretty loose. I could smell the unburned fuel while idling, and still passed that part of the test.

I think when I do have the dual exhaust put on, I will have dual cats put in also. But instead of having them welded in, I will use band clamps. Having them removable will help me dial in my idle A/F ratio. At least, that's my story. Wink.

We'll see what the future holds as far as a new engine is concerned. Good deals are had for those who aren't in a hurry.

I got called into work, so I didn't have as much time as planned, but I did get a couple important things done.

Oil change. It was ready too. Not a jack stand in sight. It's tall enough to roll right under. However, I did need a step stool to check the level. Take the good with the bad, I guess.



My Jegs order came today.



Slipped right in, mostly. This should make the sniffer happy.


I have to imagine this is the first time this truck has had a cat in at least two decades. What a difference too. According to my nose, it's much cleaner. I feel a lot better about passing now.

She's a little harder to hide then a Grand Prix.


After I cut the section of straight pipe out for the cat, I noticed a lot of debris in the upstream section. I deemed it necessary to fire it up to blow the crud out. I enjoyed that.

Welp, she failed again... But barely this time

Loaded CO was 1.60%, standard is 1.20%. It came down a long way from the 2.42% that it was before I put the cat on.

Going to try a new air filter, vac line delete, and possibly a couple gallons of E85. I have read reports of a mix of E85 substantially dropping CO levels.

If that doesn't work, I guess I'm going to have to put different jets and metering rods in, or something like that. I need to do more research on how to lean my cruise a/f ratio.

I'd beat the **** outta the truck before going there too, get the sucker as hot as you can. Break the cat in a little.

And did you do new spark plugs??

Originally Posted by Fivefingerdeathpunch

And did you do new spark plugs??

Not yet. I pulled a couple and they looked decent so I just rolled with them. Looks like I'm going to have to pull out all the stops next time. I figured the cat would be enough to get me through. Guess not.

It's a 20 minute drive to the testing facility. I thought that would get it plenty hot. Is there a "break in" period for a new cat? I think I jumped the gun on getting the re-test. Adjusting the idle a/f and slapping the cat on helped, but I could have done more.

Before the next test I want to:
1.) Put the new plugs in
2.) Put the new wires on
3.) Put a new air filter in
4.) Delete all the unnecessary vacuum lines. (I'm thinking just one for the distributor vac advance, and one for the brake booster. All others are useless emissions garbage.)
5.) Maybe put in the new pickup coil (I really don't fee like pulling the distributor)

I'm sooooo close.......

Remember the APT adjustment I mentioned? Bingo. Your carb got wires? Have you moved the accelerator pump to a short stroke?

Heres a tip if its not a feedback carb... The EPS step-up spring assorment for tuning ($8.25 at Summit) may be your answer. They fit in Q-Jets but you only use one rather than two. How much vacuum does it make at idle? You could try modifying your primary metering rod hanger spring but then you're committed. So experiment with those instead, it worked for me in tuning part throttle (I went to the heavy pink spring because lean at cruise and no sniff testing). You could definitely fudge it that way. Didn't you say you're running 6 degrees initial too? Use a dial back timing light to determine the curve. Set total at 36-38 with all advance in by 2,500 or so (vac adv plugged) and let the initial fall where it may. Use good gas and a light foot on the way to the sniffer and don't be leery of advance until initial is at like 12 or you hear knock.

Just friendly advice, I can elaborate or shut the hell up whichever applies lol

Remember the APT adjustment I mentioned?

Nope. LOL Sorry, it's all new to me.

Your carb got wires?

Just the one for the electric choke.

Have you moved the accelerator pump to a short stroke?

I haven't looked super close, but I don't remember seeing an adjustment for the accelerator pump arm.

Heres a tip if its not a feedback carb...

Feedback carb?

The EPS step-up spring assorment for tuning ($8.25 at Summit) may be your answer. They fit in Q-Jets but you only use one rather than two.

Everything I've read so far keeps pointing to metering rods and jets. Wouldn't that lean me out at cruise? (They test for 2 minutes at between 31 and 35 mph)

How much vacuum does it make at idle

I didn't commit that number to memory, but I want to say, at or just under 15.

You could try modifying your primary metering rod hanger spring but then you're committed.

Is that what everyone else was referring to when they were talking about metering rods and jets?

Didn't you say you're running 6 degrees initial too? Use a dial back timing light to determine the curve. Set total at 36-38 with all advance in by 2,500 or so (vac adv plugged) and let the initial fall where it may. Use good gas and a light foot on the way to the sniffer and don't be leery of advance until initial is at like 12 or you hear knock.

Yes. 6° with the vac advance line DISCONNECTED from the carb. With it hooked up, the mark on the balancer was way off the timing tab. Is that right?

Just friendly advice, I can elaborate or shut the hell up whichever applies lol

Keep it coming. Please.


Also, I'm wondering if some of my problem is due to altitude? This truck came from Grand Rapids (600ft above sea level) to Tucson (2600ft above sea level). Wouldn't a 2000 ft raise in elevation require some substantial recalibration? (Rods and jets)

I'll offer up what I can, man. the most efficient tune is close to the strongest too, so its worth chasin. Here goes:

Adjustable Part Throttle is a deep subject and it sounds like a non-feedback carb anyway. Whew! Post close-ups of carb plz.

She gets fuel four ways- past the idle mixture screws, through the primary jets, from the accelerator pump discharge, and through the secondary jets.

Lets stop in the road, OK? blub blub blub blub....

The idle screws you know of. FYI GM FSMs normally recommend starting at five turns out. Throttle blades MUST be SHUT at idle and no vacuum leaks can be present during tuning.

Take off. Bwaalalalaaaa

The pump's "shot" delivers immediate fuel when the throttle opens, before fuel is pulled through the primary jets.

waaaAaaaaa

You're moving and shifting now, not stompin it just accelerating with traffic. Idle screws still flowing, pump shot gone but now fuel comes also from primary jets. The metering rods don't care how deep your foot is in it, they just know that normal vacuum at idle keeps them seated in the jets because thats exactly how strong the spring below the hanger is. Q-Jets use a common hanger for primary rods, the EPS carbs use one for each in matched pairs.

So when you increase load (drop vacuum) the spring (working against engine vacuum via a piston attached to the rod hanger) can move the rods up to flow more fuel. At the same time, your vacuum advance is backing off it's effect on timing. Vacuum advance should be connected to a "ported" source (one above the throttle blades) for this reason. Some guys hook it to full time advance to crutch a cam thats too big, for more advance at idle. But it fluctuates like that, so you no want any at idle.

Here comes a Prius in the rearview, better step on it now...

bWAAAAH! Floor it.

Now you've told the trans (if TH350, via cable. If TH400, via switch and solenoid) to go down a gear and the mechanical throttle linkage has opened the big back venturis all of a sudden. This lets air pull on the secondary air valves. When the suction tilts them, a cam where they pivot lifts the common secondary metering rod hanger in sync with the incoming air so she doesn't bog and seamlessly achieves full song. Getting gas from 3 places, everybody but the accelerator pump is wide open. It gave you some right when you moved the throttle though.

If you (super carefully, the screw is tiny) remove the secondary metering rod hanger and find that the two rods do not hang evenly, you're dumping gas by holding one up. Straighten them out. Thats often bent upon installation, it can be tough to drop the rods back in right.

OK. 15 on the vac gauge is kinda low. Does it have much blowby (crankcase smoke)? More initial timing may help vac but if 15 is all she makes that indicates wear or a leak or a spicy cam. Q-jets like to leak vacuum between the throttle plate and bowl section. New I bet she made 20 or more. You can lose a lot to lagging valve timing (worn timing chain).

Don't trust the balancer or the timing mark. The soft part of the balancer erodes and can shift, and SBC timing marks are all over the place. Confirm your setup by establishing true TDC, you can make your own marks if need be.

I'll know nothing of elevation's effects, I'm a flatlander for life lol.

Anyhow, and we can talk more about the distributor (more close-ups), imagine how a weaker or possibly shorter primary metering rod spring will keep the rods in the jets longer and provide a leaner mixture in the "cruise mode". Light throttle, high gear, low RPM. Thats where they test and thats where the vacuum advance is in full effect and the idle passages plus primary rods are metering the gas. APT is a hidden adjustment, a factory application-specific tweak to do the same thing as changing "step-up" springs as Eddy calls them. There ya go, study and test then report. Been awhile since I cracked open a Q-Jet but I can if I need to!

I'd fart around with timing first, see if that vacuum reading comes up with more initial. That would keep the rods in the jets longer if it did. Hell I could set it by ear or with a tach or vacuum gauge. Might not pass though, ha. A timing light with dial is best for fine tuning.

when id fail the old sniffer back in the day id turn them mix screws in a full turn or more. then back up to second chance inspection. and pass.

If he has one secondary metering rod off the jet, that'll kill it too. Lots of em can be found running that way or with bent primary needles / hanger. His had those idle mixture screws skewed so theres no telling what else is up.

Its not so much about metering less fuel, but burning all that the carb is metering. When everything is right, less throttle input is required and thats efficiency.

Brandon, if you haven't scored a carb kit you might want to before tearing into the QJ. When you do get in there, confirm that the float is OK, meaning has no gas in it if brass and no lingering wet spots as it dries, if plastic. A sinking float can mess with mixture and is not included in a rebuild kit.

ive seen a good hand full of sunk floats. most would pump gas up the vent tube in the middle of the carb tho.

@idrivejunk... Thank you for that long elaboration. When I have time, I'm going to go through what you wrote bit by bit. There's a lot of info there. I'll take pictures and post with any questions I have along the way. Keep an eye out for me!

@Scottydoggs... If I'm understanding correctly, the mixture screws on the front of the carb only control the idle a/f ratio. That part of the test I passed. I failed the rolling/loaded test. That's part of the secondary metering system. I think?

Edit:

I also think the fact that the ambient temp was over 100° and they had misters going hurt me. Cooler temps and dryer air are desirable, right?