TheAMCForum.com Homepage
Forum Home Forum Home > The Garage > AMC V8 Engine Repair and Modifications
  New Posts New Posts RSS Feed - Can i stroke my 290?
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Click for TheAMCForum Rules / Click for PDF version of Forum Rules
Your donations help keep this valuable resource free and growing. Thank you.

Can i stroke my 290?

 Post Reply Post Reply Page  123 7>
Author
Message
Skwishy View Drop Down
AMC Apprentice
AMC Apprentice
Avatar

Joined: Feb/01/2018
Location: Wisconsin
Status: Offline
Points: 208
Post Options Post Options   Thanks (0) Thanks(0)   Quote Skwishy Quote  Post ReplyReply Direct Link To This Post Topic: Can i stroke my 290?
    Posted: Apr/02/2020 at 9:59pm
Hello everyone, long time lurker here.
I have been working on my 1968 amc ambassador. It has a 290 v8 woth 4bbl carb. Already have done some cool performance mods, mild cam, springs, bultear oil pump and timing cover, ported heads, and headers. Im trying to see what else i can do. From what i understand the eldebrock cylinder heads wont work and neither will 1970 and up heads might need modification. So now im left with the crankshaft and its components.
So my thought is can i use the 360/401 connecting rods with my crankshaft? Or perhaps someone makes pistons with smaller dimensions. I have also read the Hot rod article on this and they didnt really cover the possibility of changing connecting rods. But i do understand that the crankshafts are different between 290-343 and 360-401. With that in minds has anyone here successfully used a larger crank in their engine and was there noticable power gains? And finally should i just ditch the 290 block and try and locate a 360/401 engine somewhere, though people around here really dont let go of their engines and usually the charge a fortune for one. My ultimate goal with this car is for it to be a cool hot rod that i can take out and have decent power on the street. 
Back to Top
Skwishy View Drop Down
AMC Apprentice
AMC Apprentice
Avatar

Joined: Feb/01/2018
Location: Wisconsin
Status: Offline
Points: 208
Post Options Post Options   Thanks (0) Thanks(0)   Quote Skwishy Quote  Post ReplyReply Direct Link To This Post Posted: Apr/02/2020 at 10:51pm
I shoukd also mention its bored .40 over
Back to Top
PHAT69AMX View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jul/07/2007
Location: West Virginia
Status: Offline
Points: 5903
Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Apr/02/2020 at 10:54pm
Quick simple answer is yes, use a 304/360 3.44" Stroke Crank instead of the 3.28" Stroke 290 / 343 Crank

Edited by PHAT69AMX - Apr/02/2020 at 10:56pm
Back to Top
6t8amxetc View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Mar/11/2008
Location: Washington State
Status: Offline
Points: 630
Post Options Post Options   Thanks (0) Thanks(0)   Quote 6t8amxetc Quote  Post ReplyReply Direct Link To This Post Posted: Apr/02/2020 at 11:21pm
I really don't know much about this 290 but I do know they have it figured out!
Back to Top
WesternRed View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Aug/03/2010
Location: Australia
Status: Offline
Points: 5787
Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Apr/03/2020 at 2:26am
If you use the 304/360 crank, you will get 304 cubes plus a couple more depending on overbore. 390 or 401 crank would work but you would need custom pistons at the very least and not gain a whole lot more displacement (somewhere around 320 cubes). 

The easy answer is to use one of the larger engines, 343/390 and 360/401 up to 71 would be a direct bolt in. For later 360/401 you need to take into consideration the crank flange change for the torqueflite transmissions.

I'd just enjoy the 290 for what it is rather than try to go crazy performance wise because as they say, you can't beat cubic inches and that means you really need to dump the 290 for something bigger.

I've finally given up drinking for good...........now I only drink for evil.
Back to Top
PROSTOCKTOM View Drop Down
Supporter of TheAMCForum
Supporter of TheAMCForum
Avatar

Joined: Jun/20/2010
Location: Indiana
Status: Offline
Points: 2424
Post Options Post Options   Thanks (0) Thanks(0)   Quote PROSTOCKTOM Quote  Post ReplyReply Direct Link To This Post Posted: Apr/03/2020 at 3:13am
Originally posted by Skwishy Skwishy wrote:

So my thought is can i use the 360/401 connecting rods with my crankshaft? 
360 and 401 rods are completely different in sizes from each other. Your not going to be using a 401 rod on your crankshaft because it has a larger housing bore than the 290. On top of that it is also longer than a 360 rod. 

Obviously since you've already done some upgrades your not afraid to makes some more changes, so I'll offer this advice. First and foremost do you have a budget in mind? As you already know buying parts and having machine work adds up quickly. Second what are your honest performance goals? Sure you can play around and get that 290 to run better with 20-30 extra cubes, but at what cost and compromise compared to using larger engine.

So I'll say this based on what information you have provided. You would be hands down better off buying a 360 engine and playing with it. Not to say a 390 or 401 would not be even better if you can find or afford one, but the absolute best bang for the buck is using a 360 for any AMC project. 

At the end of the day your the one that has to decide what you want and more importantly what your willing to pay for. 

Good luck with your journey,

Tom
Molnar Technologies Full Service Dealer - Crankshafts & Connecting Rods

1969 AMC Rambler Rouge Race Car
1974 AMC Hornet Hatchback, Wally Booth Outlaw Nostalgic Pro Stock Race Car Project
Back to Top
Trader View Drop Down
AMC Addicted
AMC Addicted


Joined: May/15/2018
Location: Ontario
Status: Offline
Points: 6746
Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Apr/03/2020 at 7:04am
Ok, addicted to the number thing and have not built this so double check the math!
K455X125 pistons 4.125", CH 1.055, 22 CC dish
3.44 stroke,
6.385 rods,
0.042" gasket,
52 cc head, 
piston will be 0.015" below the deck,
quench at 0.057
SCR 9.67:1
368 CI
Taking Smokey's rule of throwing in the longest rod that can fit.
As stated, never done it and don't know if it would fit - do the math!
Back to Top
Heavy 488 View Drop Down
AMC Addicted
AMC Addicted


Joined: Apr/27/2019
Location: In the
Status: Offline
Points: 3529
Post Options Post Options   Thanks (1) Thanks(1)   Quote Heavy 488 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/03/2020 at 8:12am
In the privacy of your own home behind closed doors, stroke away. LOL
Back to Top
Boris Badanov View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Dec/14/2013
Location: NH USA
Status: Offline
Points: 4209
Post Options Post Options   Thanks (0) Thanks(0)   Quote Boris Badanov Quote  Post ReplyReply Direct Link To This Post Posted: Apr/03/2020 at 8:24am
A 401 crank with custom rods and some relief work at the bottom of the cylinders should work.

But why?
Gremlin Dreams
Back to Top
Trader View Drop Down
AMC Addicted
AMC Addicted


Joined: May/15/2018
Location: Ontario
Status: Offline
Points: 6746
Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Apr/03/2020 at 8:50am
Forged pistons and rods in a 290 to 360 will cost approximately the same. 
A 390 or 401 is going to cost significantly more to build.
For street use, why not?
And as far as stroking, I'll use the big or little head as per perspective:) 
Back to Top
 Post Reply Post Reply Page  123 7>
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.03
Copyright ©2001-2019 Web Wiz Ltd.

This page was generated in 0.188 seconds.
All content of this site Copyright © 2018 TheAMCForum unless otherwise noted, all rights reserved.
PROBLEMS LOGGING IN or REGISTERING:
If you have problems logging in or registering, then please contact a Moderator or