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12-01-2021, 11:15 PM | #1 |
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What do you recommend
So I am at wrk contemplating what to do.
I daily drive an 85 K20 350 600cfm Holley carb rusty long tube headers and exhaust held with bailing wire Th400 that's starting to slip. Gears are 4:10 tires are 265/75/16 My daily commute is 53 miles each way, all highway miles I know I have to replace the trans since lately I need to give it a bit more gas in the mornings just to get it to engage gears Reverse or Drive. I have an L31 sbc with roughly 15k miles on it, that I will eventually replace my stock 350 that will get Max EFI kit from summit. If not the L31 engine what SBC would you do. not really keen on doing the whole LS swap since that's roughly 3-5g for a high mileage engine. Ant insight would be appreciated Memo
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Memo S. Retired US Marine Family Man Last edited by memo43; 12-02-2021 at 11:10 PM. |
12-01-2021, 11:20 PM | #2 |
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Re: Whats do you recommend
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12-12-2021, 10:00 PM | #3 | |
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Re: Whats do you recommend
Quote:
I built it to have fun and drive like I'm 18 again, if I want to drive like an old man I drive the Corolla. |
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12-01-2021, 11:20 PM | #4 |
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Re: Whats do you recommend
I put an L31 in my 72 Blazer and I'm really happy with it.
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12-01-2021, 11:25 PM | #5 |
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Re: Whats do you recommend
Warrens69GMC I have no interest in ever driving a newer car, although heated seats are nice. Please don't think I'm being rude, I'm trying to get close to 15mpg, similar to newer 1500/2500 trucks
My last one a 2015 GMC 1500 (bought new) spent more time at the dealership than my garage. Besides I love driving my old square body Truckster I've read your post on your build, that what got me to pull the trigger on the engine.
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Memo S. Retired US Marine Family Man Last edited by memo43; 12-02-2021 at 02:44 AM. |
12-02-2021, 10:18 AM | #6 |
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Re: Whats do you recommend
With all due respect....you will never get 15mpg with a 4.10 gear unless you go to an OD transmission..... or change to a taller gear..
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12-02-2021, 01:03 PM | #7 |
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Re: Whats do you recommend
Get a OF trans, and stay with AT tires.
I personally would go 4L80e, but next choice would be a 4L60e. Myself I prefer the electronic controls over the TH700r4 mechanical TV cable. Yes I would use a L31 as power steering is easier to keep with it, but a 5.7 LT1 is not a bad option either. Bolts right in, but accessories are a touch annoying. Compared to early styles for ease of modification. Get a wide band O2, and a vacuum guage in the cab. This way you can maximize tuning, and thus mpg. As for the max efi. I would look at Holleys terminator or equivalent for trans control too |
12-02-2021, 10:20 PM | #8 | |
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Re: Whats do you recommend
Quote:
A what trans "OF"? As for tires I'm running Dick Cepek tires, their AT versions was not aware that either holley terminator could also control trans signal, might look into that. Every one I called has a ridiculous wait time for a rebuild trans, avg 5-9 weeks
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Memo S. Retired US Marine Family Man |
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12-14-2021, 04:57 PM | #9 |
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Re: Whats do you recommend
I'm guessing "OF" was a typo and he meant "OD" (over drive).
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12-15-2021, 03:14 PM | #10 |
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Re: Whats do you recommend
It could mean overflow - I once had a trans that constantly puked trans fluid...
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12-02-2021, 10:17 PM | #11 |
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Re: Whats do you recommend
Agreed, I eventually want to go to 3:73 gears, but that wont happen until I get a full float axle, that way I can do rear disc swap as well
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Memo S. Retired US Marine Family Man |
12-03-2021, 06:17 PM | #12 |
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Re: Whats do you recommend
F all this 4L talk, get a nicely built 200-4R since your swapping trans anyways. Better gear spread.
L31 is your best best for ease of install and price. I had a L31 in my 79 c10, all stock besides the RPM intake manifold, edelbrock 600cfm, and some ram horn manifolds. I'd get 15mpg with 3.07 gears.
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-78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle. -98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes. -02 Suburban 4x4: leveled front -CBR600F4i, CBR600RR, CBR1000RR, and standup skis DISCLAIMER: I cant spell for the life of me. |
12-03-2021, 06:35 PM | #13 |
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Re: Whats do you recommend
IMHO....
Grab a reco 350, preferably a Vortec style. Have the TH400 built correctly, 4L80e are great transmissions but the a 4L80e would run you more than the new engine and built TH400 combined. Grab a new set of long tube headers and have an exhaust shop do the pipes and mufflers....why? Do you really want to lay on the cold ground and try and build an exhaust system? IMHO, you dont need to get into the swap out and go electronic scenario... Seems most of your problem is a tired trans and old exhaust.
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12-03-2021, 11:39 PM | #14 |
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Re: Whats do you recommend
Keep the 4:10 gears and get a Gearvendors overdrive for the 208 transfer case.
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1972 GMC Jimmy 4x4 LS Swap 1985 Chevy K20 1994 GMC Yukon 2021 GMC 2500HD Duramax AT4 My "It's a Jimmy Thing" Build http://67-72chevytrucks.com/vboard/s...d.php?t=583528 Budget Build 1985 K20 http://67-72chevytrucks.com/vboard/s...d.php?t=801565 |
12-04-2021, 10:16 PM | #15 |
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Re: Whats do you recommend
I use to get 14 mpg in my Jimmy on road trips. The secret with no overdrive is a manual trans. I'd keep the motor, swap in a manual trans and try a 255 85 16 tire. That should get you close.
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12-07-2021, 04:31 PM | #16 |
driving is in my blood
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Location: Mesa AZ
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Re: Whats do you recommend
Weird, my 78 got 10mpg with the SM465. I swapped in an M20 and still, 10mpg
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-78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle. -98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes. -02 Suburban 4x4: leveled front -CBR600F4i, CBR600RR, CBR1000RR, and standup skis DISCLAIMER: I cant spell for the life of me. |
12-05-2021, 11:07 AM | #17 |
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Re: Whats do you recommend
I'm with Warren. Buy a Corolla. I used to work with a guy who had a long commute and he drove some little GM product like a Geo or something. I'm not sure if I remember the name correctly.
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12-09-2021, 02:36 PM | #18 | |
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Re: Whats do you recommend
Quote:
Ours got 38mpg at 65mph (1.8) My brothers got 41mpg at 65mph (1.6) |
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12-09-2021, 03:22 PM | #19 |
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Re: Whats do you recommend
My daily bomb around town is a Subaru Wagon--28mpg. Gas prices in Calif is killing me at almost 5.00 per
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12-05-2021, 04:45 PM | #20 |
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Re: Whats do you recommend
Get a 2nd older vehicle and build it optimized for highway mileage. Then you can rebuild your K20 as an honest off road 4wd.
A quick search found this around here: https://oklahomacity.craigslist.org/...406247938.html Might be similar in your area. |
12-08-2021, 09:25 PM | #21 |
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Re: Whats do you recommend
Thanks all for the response's
I will be doing the basic reman trans swap for now. I never would have imagined that there would be a nation wide shortages on th400's. Something like a 4 week wait time. The worse is maybe by March, first toilet paper and now transmissions. I guess while I drop my trans I will address the exhaust issue, and prep the L31 for going in. This turned out to a might as well project. Maybe I will do the blazer tank an get rid of the dual saddle tanks, sending unit on the driver side tank is bad. Good time as any to prep for going fuel injected I guess
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12-09-2021, 01:11 PM | #22 | |
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Re: Whats do you recommend
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12-09-2021, 08:38 PM | #23 | |
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Re: Whats do you recommend
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I have sworn upon the altar of God, eternal hostility against every form of tyranny over the mind of man. - Thomas Jefferson |
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12-09-2021, 08:42 PM | #24 | |
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Re: Whats do you recommend
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he is going the l29 route. I called dibs on his engine already. I will look into the cam you mentioned, what kind of rockers are you running with that cam.
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Memo S. Retired US Marine Family Man |
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12-09-2021, 08:50 PM | #25 | |
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Re: Whats do you recommend
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