360 to 401

[Dirtfarmer]

Probably been asked many times before but havent had much luck searching,
I have a tired 360 in my 1986 J10 with Torqueflite auto. Want to replace it with a 401 that either I will find and rebuild or possibly buy a rebuilt longblock if I could find one. 1. is there a specific year to look for as far as ease of attachment to the tranny. Also if I buy a longblock 401 will the 360 stuff like oilpan, valve covers, front cover etc. all swap.

[jaber]

Any year 401, they are all the same, and yes, all the external parts swap.
If its from the 70's, make sure the bushing is pulled out of the rear of the crank shaft. the nose of the TF converter is bigger in diameter than the 400's.

[AwesomeJ10]

You will also need a 401 flexplate from a '74 AMC Matador (that had a 401 and 727 tranny). Otherwise if you use the 360 flexplate, it will be out-of-balance.

[will e]

Depending on the year blocks you have, some of the accessory bolts on the front of the engine are larger on the 401. Check all of them before assembly as the 360 bolts can feel like they are threading in but are actually too small. Not all are different.

Also, pay attention to the damper. Some 401 had a 3 bolt damper. Your 360 probably has a 4 bolt. Your crank pully won't work with a 3 bolt damper.

[Dirtfarmer]

Depending on the year blocks you have, some of the accessory bolts on the front of the engine are larger on the 401. Check all of them before assembly as the 360 bolts can feel like they are threading in but are actually too small. Not all are different.

Also, pay attention to the damper. Some 401 had a 3 bolt damper. Your 360 probably has a 4 bolt. Your crank pully won't work with a 3 bolt damper.

Can I swap the 360 dampner onto a 401 or is it used for balance

[will e]

You will get three answers:
Yes
No
and I don't know.

I am "I don't know". I read so much about it and there is a bunch of misinformation. Some swear you can, others claim it won't work. So I don't know. Sorry.

[fulsizjeep]

The dampner is a balancer specific to the engine size so you would need a 401 4 bolt dampner to make the 360 pulley fit. It is very likely some of the exhaust manifold bolts on the 360 are smaller than on the 401. When I swapped the 76 401 into my 88 GW, I had to ream the 360 exhaust manifold bolt holes a little to get the larger bolts to fit. I put headers on it after the log manifold blew out a few years later.

This is also a good reference for your question.
http://cfsja.org/tech/drivetrain/401/401.html

[Dirtfarmer]

The dampner is a balancer specific to the engine size so you would need a 401 4 bolt dampner to make the 360 pulley fit. It is very likely some of the exhaust manifold bolts on the 360 are smaller than on the 401. When I swapped the 76 401 into my 88 GW, I had to ream the 360 exhaust manifold bolt holes a little to get the larger bolts to fit. I put headers on it after the log manifold blew out a few years later.

This is also a good reference for your question.
http://cfsja.org/tech/drivetrain/401/401.html

thanks