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401 swap update. HP estimates break in Q's too.

5K views 84 replies 9 participants last post by  jeepdj5 
#1 ·
Finally Had some good weather. Got the 401 painted up and assembled.

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I got it mated yesterday before I called it quits before sundown.

Feel free to chime in. I have a lot invested here

From what I understand on a new engine you prime the pump with old dizzy.
Use oil with zinc.
Just to be safe add octane boost to the tank of regular unleaded because it's 9.5:1 ratio.
Run 20 minutes between 2,000-3,500 RPM
Drain oil and replace filter.
Drive up some steep grades. In the few thousand miles to set rings (TRUE?)

When can I go do a dyno pull?

Or do you think I met my goal of 400HP 450ft/lbs?

MSD coil, dizzy, and wires
Edelbrock Performer intake
670cfm Holley TA ( do I need more carb?
.30 over
9.5:1 plugs
5-angle valve job porting too
Crower stage 2/3 cam
INT/EXH - Dur @ .050" Lift: 212°/220° RR: 1.6/1.6 Gross Lift: .464"/.488" LSA: 112° RPM: 1500 to 4500 Redline: 5000

I've been asking around a few other threads and the only answer I got was 350HP

What else could I do to have a street able 400HP?
 
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#53 ·
CSP said:
Don't drive it without adjusting the throttle modulator for the transmission first. You'll burn up the trans quickly. Google can get you to a webpage on how to adjust it. I know I've seen one on www.ifsja.org .
I already got it dialed in. Shifts great and holds gears like I like it.
 
#55 ·
Saul32 said:
Good stuff. Did you get the leak fixed yet?
Hope so. I took my sweet time on the valley pan and didn't force anything this time. Cleaned it all up really well and used high temp rtv strategically. I'm letting it sit two days before I put the coolant back in and run it. Hopefully it helps it seal up well.

Now I just have to get the oil leak figured out. It's not horrible, but its dripping enough to be annoying. It seems to be coming from the oil pump. I am worried I might have screwed it up trying to prime my pump without petroleum jelly in there. I just spun a drill on high with the old dizzy for about a minute before it started pumping.
 
#56 ·
revelc said:
Hope so. I took my sweet time on the valley pan and didn't force anything this time. Cleaned it all up really well and used high temp rtv strategically. I'm letting it sit two days before I put the coolant back in and run it. Hopefully it helps it seal up well.

Now I just have to get the oil leak figured out. It's not horrible, but its dripping enough to be annoying. It seems to be coming from the oil pump. I am worried I might have screwed it up trying to prime my pump without petroleum jelly in there. I just spun a drill on high with the old dizzy for about a minute before it started pumping.
Return the pump and get a new one?

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#57 ·
jeepdj5 said:
Return the pump and get a new one?

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It's an AMC motor. The pump is a part of the timing cover...
 
#59 ·
jeepdj5 said:
I know that!! I thought it was replaced during the build? Probably still a warranty??? Pretty goofy system if you ask me, my chief has the 258 so I have nothing to worry about :D

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The gears were replaced. The pump is original. I am not sure if its leaking from the idler shaft, the gasket, or somewhere that I can't see without taking my alternator off.

All you have to worry about is keeping up on the interstate lol.
 
#61 ·
Eric1080 said:
mine leaked until i put in a midplate for the pump when i noticed a bad gasket. i added this midplate and my oil pressure went up a fair amount: http://www.bjsoffroad.com/prod-605.htm
Thanks for the tip. I still have a gasket laying around from the rebuild kit. My pressure seems fine for now so I don't think the mid plate isn't necessary. The two gaskets make me nervous.

I am still running it open headers to tool around. No coolant leaks and I am please to say this thing stays cool. I know 401's that have been bored over have heat issues but with my 160* thermostat she stays under the green marker even at idle. I took it for a little spin after I let the intake sit for a few days and found some light trails. I found a steep hill with loose dirt. I tried to drive up in 2 hi and it wouldn't do it. So I dropped it in 4-lo and it idled right up.

These 401's are torque monsters.
 
#63 ·

Here's a clip of the break in with open manifolds.
 
#65 ·
jeepdj5 said:
Cool!! Your fuel filter return line hose barb should be at 12:00

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Thanks man. I will make sure I get that taken care of before I drive back to Texas.

I am slightly nervous about driving such a fresh build 800 miles so early into the break in. Any tips are appreciated.
 
#67 ·
Rev, where are u in Texas im in Austin, id love to see how that 401 feels!! :)
 
#68 ·
super98lsc said:
Rev, where are u in Texas im in Austin, id love to see how that 401 feels!! :)
I'm from Ben Wheeler, which is between Tyler and Canton. About 45 minutes east of Dallas.

I'll be in your neck of the woods for our honeymoon this summer. We're going to be in the hill country for a few weeks in July then we are thinking about driving down to Corpus. And yes. I convinced her to let me drive us in the Jeep down there. Maybe we can meet up while we're down there.
 
#70 ·
jeepdj5 said:
Then take it to Wisconsin so I can take a ride :D

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Yeah, just let me take out a loan for that lol.
You can probably build your own 401 for what I'd spend in gas going up there.
 
#71 ·
revelc said:
Yeah, just let me take out a loan for that lol.
You can probably build your own 401 for what I'd spend in gas going up there.
I know it sucks!!! You probably don't get to snowmobile, well they get 7mpg if you lucky maybe 8-9 mpg, they have 12 gallon tanks and with today's gas prices :( good thing my Cherokee chief has a 258 that gets 20 mpg :D

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#73 ·
$1.75????? How long ago was that?
Its $4.79 a block from my house. I farrrrkin HATE living here now..
I'm moving at the end of the month tho. Gas station 5min from my new place is 50 cents cheaper. Might not seem like much but that will def add up t some extra wheelin hours
 
#74 ·
I miss gas prices that didn't.... I'll stop myself before a political rant.


I am sure $.50 adds up big. Especially with Jeep MPG's
 
#76 ·
jeepdj5 said:
About 8 years ago, it was like $2 before Obama got in

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I remember being in Cali at my AF tech school after Obama was elected and a few months later they were around $6. Something for premium

I had a suburban with a 12" lift, 35"s, and a hot 350 with aluminum Edel heads, and a ton of mods. It drank gas so bad i got it for $3,500 in mint condition.
1/3 of my pay went into my tank and into Al Gores "statistics" lol.

Good times.
 
#77 ·
revelc said:
I remember being in Cali at my AF tech school after Obama was elected and a few months later they were around $6. Something for premium

I had a suburban with a 12" lift, 35"s, and a hot 350 with aluminum Edel heads, and a ton of mods. It drank gas so bad i got it for $3,500 in mint condition.
1/3 of my pay went into my tank and into Al Gores "statistics" lol.

Good times.
WoW do u have a picture of it?! Sounds like a cool rig

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