How would you build a 401 for a Jeep?

[FrankNB]

If you found a 401, complete but disassembled. What would you do if you were not in a rush? How would you build it, what machining would you do to it? Basically, I'm looking for a step by step to create a good powerful Jeep engine.

[tufcj]

Check the cylinder taper. If it's within spec, hone and re-ring using stock pistons. If you bore and replace pistons, keep it at 9:1 or below (stock is 8.25:1). Have it balanced. Have the rods magnafluxed and re-sized. Spend your money on a good valve job and port/polish work. Check clearances on the oil pump and replace the front cover if necessary. High quality roller timing set. Cam with lift in the .500 range, LSA in the 110-112 range. The cam should make good torque in the low RPM ranges. Aluminum manifold like a performer or R4B and a carb no bigger than a 750.

If you have lots of money to spend, you could bump the compression up a bit and use aluminum heads, and add fuel injection, either TBI or Edelbrock's TPI.

Bob
tufcj

[FrankNB]

Thanks. Alright, in saying all that. I can reuse all the performance part from the 360 right. Mainly msd ignition, distribution and Howell TBI. The nickel plated cover and oil pump. The aluminium intake. What am I forgetting?

What eludes us also is the heads. We read that the stock heads are fine with port and valve work. So why pay for expensive aluminium heads? What justifies the 3000$? Excuse my ignorance..

[tufcj]

I think MC has shown here that the iron heads, with a proper port/polish and valve job, will flow as well as a set of out of the box Edelbrock heads. At low RPMs you run 4-wheeling, big flow numbers don't do much anyway. So, unless you need the weight savings, put your money into your iron heads.

All the other parts from the 360 are compatible. You may need a new chip burned for the Howell system to compensate for the additional cubes and airflow. They'll do that for about $100. If it really breathes, you may want to adapt the Howell to use a Holley 4BBL TBI. Howell can do that too.

Bob
tufcj

[Dusty]

before you spend any more money with howell consider doing your own chips. I was really unhappy after 2 years of mailing chips back recording data and spending gobs of money on shipping and poor performance with my howell system, which for a 401 specific system howel uses the 85 lbs/hr injectors on the holley 670 cfm tb which is bigger than the gm 350 tb that they typically use on 360s (which is 500 cfm). Anyways the point is consider the craig moates system, and have him do the soldering for you its $25 for him to solder up your computer.
start here:
http://www.binderplanet.com/forums/showthread.php?t=47254

It made a world of difference for me i go for a drive, i record data on my lap top. i come home i run the dos based smoothing program which takes the data you recorded and the original .bin file and raises or lowers the numbers from the .bin file to reflect what the recorded data said was off. it spits out a new bin file that you can then veiw in a program like tuner cats (which i really like for its simplicity) where you can smooth out the fuel map if there are any peaks or valleys and you can correct areas that the smoothing program did not catch or adjust. burn a new chip all in less than 2 minutes and go for another drive if you want.

My build was:
I am running a 401 .030 over
a set of 9:1 forged bulltear pistons
lunati 64501
Advertised Duration (Int/Exh): 256/262
Duration @ .050 (Int/Exh): 213/220
Gross Valve Lift (Int/Exh): .484/.507
LSA/ICL: 112/108

Performer intake
HEI dist
mild ported 502 heads
roller rockers
8 qt oil pan
arp bolts and studs
ported out cast iron manifolds
dual 2.5" exhaust.


If i didnt already have it i probably would have run an Engle cam. similar cam timing events and Engle goes alot more agressive on the lift #'s for similar durations. The cam is a little small for the motor on the top end a little but it is a very torqie motor. Very strong runner with the fuel injection i have been able to dial down and maintain an idle of 250-300 rpm not perfectly smooth but it will do it. I keep my idle at 500-525 and it is very smooth.

I went a little crazy and used all ARP bolts in this motor with studs ont he bottom end, it wasnt necessary but why leave anything to chance. I would not run the edelbrock heads i think they are great but for what i did with my motor the cast iron heads were plenty. maybe i could picked up another 20 hp and 20 ft/lbs but for the $$$ it wasnt worth it

i suspect a lower total hp number due to a fuel injection issue above 4500 rpm i suffer a minor fuel supplly starvation. injectors are too small or fuel pump can't keep up. i knew i was right at the limits of things on the fuel system. I could up fuel pressure in the TB and get more fuel from the 85 lb/hr injectors since they are rated at 15 psi an up ticking of the fuel pressure would increase the flow of the injectors but i am happy with the spray pattern and low rpm performance too big of injectors and too much fuel can begin to slosh around. Point is the 670 TBI is pretty good fit on this motor.

On a chassis dyno rear wheel numbers it put down the 292 hp @ 4900 rpm 389 ft/lbs @ 3500 rpm it had a similar 351 ft/lbs at 2000 rpm and carried numbers at and above 354 ft/lbs all the way to 4000 rpm. red line is 5500 rpm and it spins hard on the street to 4500-5000.

As you can see the above are rearwheel numbers
assuming 10-12% parasitic drivetrain loss it should be in that 320-330 hp 430-440 ft/lbs range. the shop that put it on the rollers called it out as 331 hp and 443 ft/lbs.

It definately feels like a 330 hp motor if i didnt have the rear wheel numbers i would have sworn it to be a 350 hp competitor btu the torque covers my butt


Some cams to look at:

Comp Cams
Magnum grind
270H
.479/.479 270/270 adv 224/224 dur @ .050 110/106
Extreme energy
.477/.484 256/268 adv 212/218 dur @ .050 110/106
.493/.500 262/270 adv 218/224 dur @ .050 110/106

Lunati
.484/.507 256/262 adv 213/220 dur @ .050 112/108
.507/.527 262/268 adv 220/226 dur @ .050 112/108

Engle
.489/.489 254/254 adv 209/209 dur @ .050 112
.501/.501 260/260 adv 214/214 dur @ .050 112
.538/.538 272/272 adv 224/224 dur @ .050 110


I'll tell you what in a CJ turning 35's on dana 44's with alloy shafts a T18 and a 4:1 D300 this is a very snappy motor and i think i am near the limits of what those poor axles can take. I was hoping for idlability not max power on this motor. and i built it with that in mind and i am VERY happy with the performance. I am not going to say this is the combo for you but i will tell you with everything dialed int eh way it is this motor and this rig are now alot of fun on and off road. and it sounds like a thumper too. There was plenty more i could have probably squeezed out of this motor but i wanted a reliable low rpm high torque motor and i think i found my combo that works for me.

Look at Donwags build if you want to see a well done grunt motor with edelbrock heads i think his numbers were similar to mine but he had the 256ex and had edelbrock heads which have better port velocities. his motor maybe could have taken advantage of the heads and thier potential with a slightly larger cam with similar duration numbers but higher lift numbers and pulled some more power out of there. the 256 performed well for him but i think it was on the small end of the choice spectrum. not saying mine is much bigger. but doing this build required that i use what i had in an effort to keep costs down. my numbers werent as high as his but i am nipping at his heals with a pretty stout runner.

[FrankNB]

You running hedders or the stock exhaust manifolds? Oops, just re-read. Ported out manifolds. thanks for the post.

[FrankNB]

And as far as balancing the engine, what is that actually? matching the weights of the internal components?

[tufcj]

They balance the entire rotating assembly. They match the weight of all the rod/piston/ring/bearing assemblies (usually down to a gram or two). Once they know that weight, they put a matching "dummy" weight on the rod journals, and spin the crank/flywheel/harmonic. They add or remove weight from the counterweights until it will all spin smoothly.

Definitely worth the money spent, if only for the longevity of the motor.

Bob
tufcj

[FrankNB]

Well, picked up the motor yesterday. It was all apart. It's yellow? Anyway, quick visual inspection. The motor is bored .040 at least that's what the pistons say. The cylinder bores seemed ok. The pistons are no good though, they are badly worn.

Will drop off the block and head at the shop to get the verdict. I'm not too happy about the .040 bore, but I read that it's not that uncommon.

Crossing my fingers.

[Dusty]

You running hedders or the stock exhaust manifolds? Oops, just re-read. Ported out manifolds. thanks for the post.

some doug thorleys or other header would have worked to get more power but i was tired of gasket leaks etc. manifolds are high tight and fit

hone it and have MC make you up a set of .040 forged pistons. a little loose in the cylinders wont kill you.

[FrankNB]

Casting on the heads is 3220502-2.

So they're '74 58cc dog-leg bridged rockers. Cool. We're getting somewhere.

[FrankNB]

Questions, like my 3 year old I like asking questions:

What's the scoop with the 502 heads?
What is it really and why?
And are they available?
Are they expensive to ship?

[tufcj]

Nothing special about the 502 heads. Ports and valve size are the same as any other 74-up bridged rocker 360-401 head. Iron heads weigh about 55 LBS each, so shipping can be expensive.

IMO the 090 or 993 heads are the most desirable. those are the late 71-73 heads with Chevy style rockers and studs. Very easy to add roller rockers, better port design than the 291s, although they are lower compression than the 291s.

Bob
tufcj

[FrankNB]

:razz:

Here we thought that someone was putting Chev 502 heads on a AMC. Then I look at the castings on my heads; 3220502-2 and it all makes sense now. All this because my bud found this post from MC on the IFSJA site where he mentions 502 heads. We were confused.

http://www.ifsja.org/forums/vb/showthread.php?t=101739

[FrankNB]

Well, come to find out the block has to be bored to .060 and line bored. Something bad happened to this poor puppy.

[crazydog]

I did a .030 over 401 with 10 to 1 compression, Edelbrock heads, Edelbrock RPM Airgap, Edelbrock 750 carb, Hooker headers, Lunati 64502 cam. I have a nice flat torque curve and I cannot wait till I get this thing installed to see what it feels like. Some more info and data is here:

http://www.ifsja.org/forums/vb/showthread.php?t=121315