🔧 BUILD 1984 El Camino 4.8 Swap

codemanrose

Member
Oct 26, 2020
28
169
Side project for the Father-in-law. 1984 Elco with 41K original miles on it. Has a 305 and th250C trans in it. He wanted to do a swap on the "tired" 305 (made 155 hp from the factory) so asked if I would be willing to do a swap. Grabbed a 243K 99' 4.8 up for $200 loaded into the truck. I have torn apart several JY LS motors and this is by far the cleanest one I have ever seen. I pulled the valve covers off and said NOPE. Toss them back on. Had new plugs, wires, oil was new, it was crazy. Slapped a china fbody oil pan with china pickup and dipstick tube/stick and cut the stock truck tray to fit. Menard oil on sale is the juice that went in. SBC/LS mount adapters and 1/8" plates I welded bolts to so the engine sat where the Fbody oil pan would not hit crossmember but still allow the stock driveshaft to be used and keep the transmission in about the stock spot.

I said we could do it for $800. We are $1300 in and it's practically done. I have stuff to sell off the old car so we can still make the $1K swap a thing. I had a later 5.3 cam laying around so that was swapped in too and we are using a P59 and DBW setup. Injectors I pulled out of the yard and are flex injectors that are 33lb at 50psi. So 35lbs at 4 bar setup. I cut a stock silverado pedal down and welded the elco pedal on and it looks and feels like stock. Car fires right up and we are ready to rip. We replaced the stock leaking radiator with an ebay all aluminum 3 row unit and Chrysler Sebring fans (I use them on S10 radiators too) and the system has been bled and working great. Connected the stock truck PS pump to the rack and it also is working as should (time and heat will tell if it lasts lol). Last thing to do make some mid pipes to vband to the LS3 manifold that Reaper sent me with o2 bungs and then this thing is ready to rip 1 tire fires for days.

I pulled the tank out and removed the entire sending unit. Did not want to spend $400 on a baffled tank and $350 on an EFI assembly so got a Holley Hydramat and the tried and proven Japan Kemos 340 pump. I connected it to the supply line inside and cut a hole in the tank for the return. 6an to 3/8" bulkhead barb fitting and the return line going intank to the passenger rear corner. This is only the beginning. The plan is to eventually do all new gauges, built 4l80e by me to handle 600 hp and maybe we can do boost down the road or a nice dry shot along with decap 100# injectors. Again, car has 41K original mile. He does plan to paint the car, but honestly I would leave it and add an 8.8 in the back on 285's and make it a nice street/strip car. More to come!
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Mr_Roboto

Doing the jobs nobody wants to
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Feb 4, 2012
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I think you'll have a bit for boost, I'm sure it'll get old after a while but compared to the 305 he'll be blown away by the power that's there. Nice Elky, always liked these. I was going to ask if there's any chance a Caprice Wagon tank would fit as well.

I'm guessing looking on line that the tank doesn't have the baffle like the GN tank does?
 

codemanrose

Member
Oct 26, 2020
28
169
I think you'll have a bit for boost, I'm sure it'll get old after a while but compared to the 305 he'll be blown away by the power that's there. Nice Elky, always liked these. I was going to ask if there's any chance a Caprice Wagon tank would fit as well.

I'm guessing looking on line that the tank doesn't have the baffle like the GN tank does?
I looked into baffled tanks and EFI pump assemblies, but the baffled tanks that fit the elco (they are specific) are out of stock almost everywhere and the ones that are not are selling for $400 or more and the only assemblies for the 22 gallon tank are ones you modify for the 17 gallon ones. So I said screw it and just modified the stock pump assembly with a pump and Holley Hydramat. I had half gallon of fuel in the tank on the floor and it would still pick it up. Just will make sure to keep over 1/4 tank of fuel in it. Drilled a hole for return and put a hose inside that goes to the corner of the tank on return fitting.

I have put 100 miles on it and the only issue is a slight PS pump leak when it's cold outside and a squeak that starts when up to operating temp and then goes away after about 10-15 minutes after. Sounds to be by torque converter so I will address it soon.

I have yet to hook up the VSS so the PCM is still on the idle fuel/timing table and wants to die at stops unless I brake torque it just ever so slightly. I made a little circuit that should take the hall effect signal out from the stock speedo that goes to the elco old computer inside the car and converts it to a VR signal the Gen 3 LS PCM can read. I was able to do some math and figure out, hopefully, the tune for 2000 ppm which is what I believe the output wire from the back of the speed is on these cars. So I guess we will see if this little circuit that contains a 0.1uF compositor and 1M resistor will work.

I'm going to be up late tonight still doing garage renovations, but I want to get it into the garage to fix those three things tonight so I can put it in storage for the winter which is about 60 miles away. I Think the plan next year is to drop that th250c and put in a 4l80e for the highway gears and maybe throw in a shorter rear gear to maybe something like a 3.23-3:55.
 
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Squeaky192

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Oct 4, 2022
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The only thing I dislike about the 80, especially with a decent converter, is how it unlocks at 0% TPS, so when you're at a cruising speed and on and off the gas it's a constant cycle of locking and unlocking.

I think there is a way to segment swap the tune to make it function more like a 4L60 utilizing the brake switch, but I never looked much into it.
 

daturbosix

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The only thing I dislike about the 80, especially with a decent converter, is how it unlocks at 0% TPS, so when you're at a cruising speed and on and off the gas it's a constant cycle of locking and unlocking.

I think there is a way to segment swap the tune to make it function more like a 4L60 utilizing the brake switch, but I never looked much into it.
What youre complaining about is all tune related.
 

codemanrose

Member
Oct 26, 2020
28
169
I guess I never realized that. With ETC it never gets to 0% TPS like DBC so I'm guessing it's a non issue here? Same reason it always shows 89-91% at WOT. P59 DBW always has been like this.

Well a squeal ended up popping up and I spent over a week trying to diagnose it. Sounded like metal on metal once up to operating temp. Once is started after about 10-15 minutes it would stop. And once it made noise it would go away under load, and come back instantly under decel/no load. Noise was coming from right at the back of the block so first thought it was torque converter or transmission. Come to find out it was pulling too much vacuum in crankcase and it was making a air squeal on the back of the rear main. Pulled oil cap and a surge of air rushed in and noise went away instantly. Changed up the PCV and all good!

There was a leak on the return line of the PS pump so I addressed that. Will drive it to see if it truly fixed. if so another check off the test list.

Now, onto the VSS and cruise. I made a little circuit that takes the Hall Effect signal from the stock elco speedo gauge that runs to the stock PCM, which is 2000 ppm, and transferring it to a VR signal the Gen 3 PCM can understand. I have a tune file I already adjusted for it and I just need to hook it up and test. If it sees it then it will get on driving timing and fuel tables and also the TAC module that control cruise I can also connect to the stock elco switch and control cruise just like stock.
If the circuit works (it's suuuuper simple) I want to print out like 50-100 of them and make little adapter boxes and just have them for anyone for like a case of cheap beer price lol. Just plug and play setup.

Here is the latest update along with the squeal and the fix I did. I'm hoping to so 1 wheel peels soon.



 
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