The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1973 - 1987 Chevrolet & GMC Squarebody Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 01-12-2018, 03:20 PM   #1
sick472
Registered User
 
sick472's Avatar
 
Join Date: Jul 2015
Location: Sedalia Mo.
Posts: 1,131
'76 350 into an '85 3/4 ton 4x4

I have my old '76 2wd that has a GM 350 crate motor with 70K miles on it and my '85 3/4 ton 4x4 is burning a lot of oil (like a quart every 1000 miles. maybe more). The '76 is almost see-through due to rust. Both are automatics and AC trucks. Neither have any real power to speak of. The '85 has an edelbrock intake and Holley carb with unknown heads and is a 350 ci as well.

My questions...what should I be aware of if I chose to swap the motor from the '76 into the '85? Would it be straight forward or will I have to make mods?

I'd love for this to be a one weekend chore should I pull the trigger.

Thanks in advance!
__________________
He who is without oil shall throw the first rod. Compressions 8.7:1

1972 C10
1976 C10 (parts truck)
1985 K20
sick472 is offline   Reply With Quote
Old 01-12-2018, 03:25 PM   #2
natedogg
Registered User
 
Join Date: Dec 2013
Location: West, TN
Posts: 312
Re: '76 350 into an '85 3/4 ton 4x4

This will be a easy swap. All the pulleys and brackets from your 85 will swap over to the 350 out of the 76. You and a buddy should be able to do this in a weekend.
natedogg is offline   Reply With Quote
Old 01-12-2018, 07:40 PM   #3
MikeB
Senior Member
 
MikeB's Avatar
 
Join Date: Jul 2000
Location: North Texas
Posts: 3,597
Re: '76 350 into an '85 3/4 ton 4x4

Should be a piece of cake, especially if you're going to use the intake and carb off the 85's current engine. But there's always some little issues to iron out. Seems like 85 engines had passenger side dipstick, whereas 74 had drivers side. But that shouldn't be any big deal. I would transfer any parts like intake manifold, oil & temp senders, and kick-down cable bracket while both engines are out. And that's also the time to make sure the 74's starter will bolt to the 84's electrical connectors.
__________________
Mike
1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, recent AAW wiring harness, 5-lug conversion, 1985 spindles and brakes.
1982 C10 SWB -- sold
1981 C10 Silverado LWB -- sold, but wish I still had it!
1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming.
Retired as a factory automation products salesman.
Worked part-time over the years for an engine builder and a classic car repair shop.
Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then!
MikeB is offline   Reply With Quote
Old 01-16-2018, 09:38 AM   #4
sick472
Registered User
 
sick472's Avatar
 
Join Date: Jul 2015
Location: Sedalia Mo.
Posts: 1,131
Re: '76 350 into an '85 3/4 ton 4x4

Thanks for the encouragement folks!

I guess it's time to just wait for the old 85 engine to expire or use so much oil that I can't take it anymore. I think it is constantly leaking by the valve seals as I never see any oil smoke or leaks big enough to compare to the oil loss. The spark plugs need to be freshened-up/changed every year or so (5000 miles) because of oil fouling. Compression is from 170 to 200 psi and the pcv valve has been changed. There is no coolant loss either. Anyhow, this may be something for a different thread. Thanks again!
__________________
He who is without oil shall throw the first rod. Compressions 8.7:1

1972 C10
1976 C10 (parts truck)
1985 K20
sick472 is offline   Reply With Quote
Old 01-16-2018, 01:44 PM   #5
Junqueboi
Registered User
 
Junqueboi's Avatar
 
Join Date: Oct 2008
Location: Leasburg, NC
Posts: 55
Re: '76 350 into an '85 3/4 ton 4x4

If the dipstick is on a different side, you may have to swap out exhaust manifolds...which means your exhaust pipes will no longer fit -> trip (tow?) to muffler $hop. I think a lot of the crate engines had dipstick provisions on both sides though. You'll just have to check I guess.
__________________
Jel
Junqueboi is offline   Reply With Quote
Old 06-29-2021, 08:09 AM   #6
sick472
Registered User
 
sick472's Avatar
 
Join Date: Jul 2015
Location: Sedalia Mo.
Posts: 1,131
Re: '76 350 into an '85 3/4 ton 4x4

Well, it's time to do the swap. I have the 76 engine on the stand and hope to use the original cast intake with the original Quadra Jet carb (will rebuild). I plan to replace the water pump and fuel pump, but have not closely compared the two truck's pumps....

Should I buy the replacement pumps for the 85?

The 76 did not have a return line on the fuel pump and I think the 85 does. I am assuming that both the 85 style pumps will bolt up to the 76 motor.
__________________
He who is without oil shall throw the first rod. Compressions 8.7:1

1972 C10
1976 C10 (parts truck)
1985 K20
sick472 is offline   Reply With Quote
Old 06-29-2021, 10:18 AM   #7
84 400
Sb 400 club
 
84 400's Avatar
 
Join Date: Nov 2005
Location: NH / MA
Posts: 2,746
Re: '76 350 into an '85 3/4 ton 4x4

You want the fuel pump for the frame truck your going into. Also be aware in 1986 SBC used a 1 piece rear main seal and different flex plate. Always something to look out for when swapping engines. Guessing one truck is a th350 and the other is a 700r4? i know your going into an 85 and not an 86 but who knows what has been changed.

This is a great time to replace the rear main seal and oil pan gasket. I like the one peice felpro oil pan gaskets. Its a great time to knock in new freeze plugs and give it a nice coat of paint. Do you need too? Maybe not but after having to do a rear main seal in a rig a week after a swap i will always do them on the stand before.
__________________
1984 chevy c10, built 400sb,.(SOLD)
77 K10 Project / daily driver "The Grinch" http://67-72chevytrucks.com/vboard/s...d.php?t=318363
1956 Willys Wagon (327 chevy) Project (Now Buick 225)
1980 Corvette L-48 4 speed
1992 Mustang GT built 5.0 5 speed

1985 C10 LWB Sold
1982 K10 SWB plow truck Parted out
1986 D30 M1028 fire brush truck Parted out
84 400 is offline   Reply With Quote
Old 07-14-2021, 11:08 AM   #8
sick472
Registered User
 
sick472's Avatar
 
Join Date: Jul 2015
Location: Sedalia Mo.
Posts: 1,131
Re: '76 350 into an '85 3/4 ton 4x4

Thanks for everyone's help...it turns out the 76 motor had some issues (one scarred crank bearing and one booger'd piston). I found this while breaking it down to change the rear main seal. Good 84 400 suggested that, otherwise I'd never seen the crank bearing. So...time for rebuild. I am sure I will still be mixing and matching parts as the 76 block should be a good base to build from with the 85 block as a back-up.
__________________
He who is without oil shall throw the first rod. Compressions 8.7:1

1972 C10
1976 C10 (parts truck)
1985 K20
sick472 is offline   Reply With Quote
Reply

Bookmarks


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 09:55 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com