Andy’s 1995 CCLB 7.4L TBI to Vortec Swap

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andy396

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So I’ve been a member for a while now and have been working towards this swap for a long time. As I sit here mid project, filled with a bit of frustration, I’m thinking it might be therapeutic to do my own write-up. I’ll add to it as time allows. Comments welcome. If you choose to continue reading, please keep the following in mind. My primary purpose for owning a truck is to use it as a truck to get work done. It’s not a commuter vehicle for me. I want it to do what I ask of it, when I ask it to do it. This includes hauling rocks, dirt, mulch, car parts, large items, a trailer carrying a car/truck/four wheelers/lumber/logs and whatever else one can fit in it. And most importantly to my wife, our ‘97 23’ Chaparral Bow Rider boat. While I’d love it to look all shiny and pretty looking while doing so, family priorities often limit such wants. Hence spending $40-50k on a new truck is tough to justify as well. I’ve been messing with cars my whole life so owning a used truck as a secondary vehicle seems to make more sense to me.

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Ever since I was a kid, riding to school everyday I passed a Chevrolet dealership. I still remember my first time seeing my first GMT400 in 1988 and how much I drooled over that truck. I watched every year from 1988 until I graduated in 1995. I remember thinking that they just kept getting better and better looking and by 1995 I was loving the new grill and interior. My first GMT400 was a 1988 C2500 RCLB 7,200GVW that was a highway department truck that I repainted black/silver.

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Fast forward to 2012. A house, a wife, and two kids later. Perusing through Craigslist one night I see two CCLB K3500’s for sale in my area. I say to my wife, “what do you think if we get a bigger truck that can haul the whole family?” To my surprise she says sure! I looked at both of them. The first one was a maroon on maroon 5.7 Vortec. I couldn’t make a deal with him, plus the bed was showing quite a bit of rust at the cross supports. So I go look at the second one. It’s a 7.4L TBI that this guy bought the previous year in SC without an engine. The PO pulled it to put in his boat so the story went. So this guy got a direct swap engine from a junk yard and installed it. He couldn’t tell me how many miles were on the engine except that it was more than the 144k that was currently on the truck. He decided to sell it because he wasn’t happy with how it towed his 10,000lb travel trailer plus 1000lbs of tools when he travelled from job site to job site. For a guy who has lived in the rust belt his whole life, this truck was amazing. Not a single spec of the crusty rust that invades our trucks here. Yes it was dinged up and the paint pretty faded but it was solid as a rock! It ran okay, but definitely needed some TLC. I was also digging the blue on blue and it was loaded with all the creature comforts. So we made a deal and she was mine. After giving it all the TLC it needed like brakes, rotors, bearing seals, wheel cylinders, hydro booster, reinstall the cat, new front seats, grill, tow hooks, steering gearbox, A-arm bushings, pitman and idler arms she went to work as our weekend warrior truck.

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Come to find out, that engine should have stayed in the junk yard! It wasn’t long before I was adding a quart of oil every tankful of gas! But it got the job done taking everyone to and from the hardware store on the weekends or the boat to and from the ramp not too far from the house. I only put about 3k miles a year on it. It wasn’t long though before I started planning for a drivetrain rebuild not know how long this engine was going to hold out. I really wanted a L29 Vortec but the TBI did what I needed it to do. I happened to come across a 2000 RCLB K3500 with the L29 7.4L Vortec for sale for parts on CL. Complete with only 114k miles on it, but could no longer pass inspection because the frame was so rusted. So here I think I found my solution. Refurb or rebuild the ‘00 drivetrain and just have everything ready to swap over. I took a bit of a chance on it since it wouldn’t run for more than a second or two due to a security code. Once I got it home, I did a security relearn procedure on it and it fired right up. Drove it around the block without any power steering or brakes and a leaky exhaust long enough to tell that it had no major issues and seemed to run and shift well. I eventually got around to stripping it down and selling any part of value that I wasn’t going to need for the swap.

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98chevy2500SS

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Nice story on the truck! How badly rusted was the frame?
 

andy396

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Do you mean on the parts truck? It was used a farm truck up in NY where it then made its way down to PA as a plow truck. The front was the worst. They already welded braces to hold the front cross member in.

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Supercharged111

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114k? Not sure I'd bother rebuilding. My 3500 came with 130k miles and it runs like new. POs kept the oil changed too thankfully so it's clean inside and out, hardly burns any oil if you can believe that. I would advise you swap the cam and roll in new bearings, other than that just send it if it looks clean. Oh, do intake gaskets too. Those are a when not if scenario. The cams like to eat themselves and there's room for improvement over stock. Putting eyes on the bearings gives you an idea of the life it's lived. It may be easier to swap in that newer dash so everything plugs in, I've never Vortec swapped a TBI truck before.
 

andy396

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I started with the transmission. Yes, I know 114k isn’t bad but it had a gooseneck and did a fair amount of pulling on its life so I figured it couldn’t hurt to freshen it up a bit. Plus, I hadn’t been inside an automatic transmission since I was 15. Opened it all up and it looked surprisingly good.

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andy396

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I got the rebuild kit from http://www.jakesperformance.com/rebuild-kits/ just for the reason that it seemed a better chance of getting quality parts and some technical support should I need it. I was also thinking I liked his idea to machine the forward hub and put a torrington needle thrust bearing in there. Once I got the parts I opted not to got with the modified forward hub because I wasn't crazy about the stress concentration that was created from the machine process. He swears to have success with it, but there was vertually no wear on the original thrust bearing after 114k miles plus this thing is barely going to turn over 4,500 rpms so I figured I'd take my chances with the GM design as is. I did open up the shift solenoid orifices a little bit, just not as much as he recommended. I went with an 0.078" orifice on the 2nd feed, 0.093" on the 3rd feed and 0.0625 on the 4th feed. The main improvement I made was modification to increase the hydraulic pressure force on the 3rd gear clutch, called the dual feed mod.

Pic below of the forward hub after machining to allow for torrington bearing.

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andy396

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So at this point I've been driving on that old tired engine for about 5 years. A lot longer than I had planned, but as long as I kept feeding it oil, it kept running and I just kept kicking that can down the road working on other projects. Sometime around late 2016 early 2017 I noticed antifreeze leaking out the front head gasket. This was just after I had pulled my engine in my Chevelle to start rebuilding it. I told my wife, looks like the Chevelle is going to have to get put to the back burner and I put the L29 up on the engine stand instead. It was nasty! The rust was falling off in huge chunks from the heads. I buttoned up every orifice and did the unthinkable. Yep, I sandblasted it. o_O

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I think this plan would have worked except the exhaust manifold was so rusted that the swell from the rust had pushed the manifold away from the head and cracked it. I didn't see this until it was too late. So now I didn't have a choice, I had to disassemble the whole thing and wash everything down at the least. Say what you will, I did what I did and there was nothing I could do but keep moving forward.

:badidea:
 

andy396

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Since I discovered the leak it was getting driven extremely little, only if necessary. Now at June 2017, driving home from my parents one evening I notice it making a weird sound whenever I accelerate above about 3,000rpms. Still seems to be running the same though. Make it home and park in the driveway and try to replicate the sound one more time reving it up again and it makes a louder knocking followed by shaking the entire truck. I immediately shut it down, but not before the number 1 or 2 rod cap lay in the driveway.

She said, "I can't wait any longer".

She's done.



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andy396

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When I got the L29 engine apart and mic'd the cylinders they were at the limit of wear. Since I have a connection for getting machine work done, I couldn't see not boring it out and putting new pistons and bearings in it. I would have been very annoyed with myself if I put all this work into it and still had a truck that burned oil. One snafu along the way came when putting the pistons back in. The low tension rings on these engines are really tricky for me to get in for whatever reason. I had the same trouble on the 5.7 Mercruiser in my boat. The oil rings kept getting caught and folded between the piston and cylinder (not good!). I should have known better going into this rebuild, but I was still using the same style ring compressor. This time, again unknowingly had caught an oil ring between the piston and cylinder but this time when I rotated the block is gouged the cylinder! After getting it re-machined and re balanced I purchased a better ring compressor from Summit Racing. What I should have done in the first place.

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andy396

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So bear in mind, house, wife, two kids, full time job, family, life. We're not moving at lightening speed here! Early 2018 the L29 is all put back together and looking pretty.

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