Help with 401 build?

[4x401cj5]

I`m rebuilding another 401 for my `72 cj5 and could use some advice. I`m trying to wring as much HP from this "Budget" build as possible, and I will be running "Premium", pump gas. I drive this thing everyday to work, and beat the crap out of it on weekends. My cj is running Dana `60s front and rear with 35 spline axles, 4.56 gears and 37" tires. Transmission and transfer case are a 6.42 T-18 mated to a Scout Dana 300 with 4:1 gears and 32 spline front/rear output shafts. Front and rear drive shafts are 1 ton 1350 series. The drivetrain is up to whatever we can come up with here.

This is what I currently HAVE, AND INTEND to use so far;

A `76 stock bore 401 thats ALREADY preped for assembly. The block has been tanked, checked for cracks, honed, and new freeze plugs installed. The crank has been cross drilled and turned 10/10. I did the valley bypass oil mod, and re-drilled the cam bearings with a smaller hole.

The pistons and rods are stock, and I ALREADY have new cast rings.
Should I polish the beams and at least weight match the assembly?

I plan on re-using some parts I have on the current 401 in my cj.

I will be running STOCK exhaust manifolds (I can`t stand headers), that dump into dual 2 1/4" pipes running through Flowmasters that exit at the rear bumper.
My ignition system consists of an MSD Pro-Billet dist. and 6-AL box.
I have a Performer intake with a Quadrajet that will also be re-used.
Yes, I have tried other carbs from Edelbrock and Holley. The Quadrajet beats them hands down off-raod, so I`ll be sticking with it.

For heads I have a choice between a set of 6291 or 090`s.

Whatever I use will get a three angle valve job and some exhaust porting. The heads will also get a set of Scorpion roller rockers.

Which heads should I use, and what kind of compression can I expect?

What would be a good choice for a cam?

I DO NOT give 2 $hits about gas milage, the outfit I work for buys my gas. I want some decent performace on, and off-road.
Any advice is appreciated.

What say ye?

[fifesjeep]

This is what I would do... 670 truck avenger, eddy performer intake, internal oiling mod (if you plan on running up the rpms)... 9.5 cr pistons, comp cams 270h cam and lifter set, one piece pushrods, 1.6:1 roller rockers, 1 5/8 inframe headers dual exhaust. stock distributor with msd cap-adapt, e-coil and an msd ignition or a pro-comp ignition module, bulltear sells them for $160-ish. Parts listed above aren't cheap but, it's a nice little combo for a crisp throttle response and with your set-up you'll have nice low end grunt and mid to high rpm break neck fun.
You can find a lot of good used parts for cheap...

[4x401cj5]

Post above has been edited for clarity.

[fifesjeep]

I would look into the 270h... That 401 will toss that jeep up and over things with ease. The 270h is a nice streetable cam...

As for your connecting rods... If you are worried or think something might be wrong with them, Have the garage check them out and then go from there... if there isn't anything wrong with them and you're not spinning the engine up or running a lot of HP I wouldn't even worry about them... (That's just me).

These Engines like to breathe, so in my opinion... the 2 into 1 at 2 1/4" sounds a little restrictive... 2 1/2" Sounds a little better (for my likes).

The quadrajet is a decent carb... But, I would take a Holley truck avenger over it any day of the week... (that's me though).

The 291 heads are the 52cc heads and they will bump the CR a little... maybe 9.5:1??? Somebody will chime in to correct me if I am wrong. These heads are good for the CR but, apparently they don't flow as well as the later heads... Somewhere online there is an article about valve jobs and how the AMC heads seem to like 30* on the Intake and 45* on the exhaust??? maybe it's the other way around...

[msalaba]

I have the last bridged rocker heads. iirc I had them shaved 0.045" (~52cc chamber) which puts me at a tad under 9.0:1 CR on a bone stock 360.

I'm sure a 401 would had much more appreciation for the larger valves.

Sounds like a nice build. I'm jealous (my 360 too!)

[Dusty]

imho there are better cams than the 270h, .479 lift with a 224 dur @.050. Engle makes a cam with the same 224 duration @ .050 but that has .538 in lift. I've run both the 270h sounds good just like the engle sounds at idle but the the engle cam provided better numbers on the dyno, i dont think either was an excellent fit for a lugging or offroad motor, but they do jsut fine. I think a little smaller on the .050 duration numbers yeilds better idling characteristics.


my opinion is look at lunati and engle for cams or just get the good ole summit 8600 for a fail safe always works cam.


for a budget build id run stock compression pistons with the 291 heads that would get you close to 9:1 then id get a good cam in the 214-220 duration @ .050 department with a performer intake. re-use the timing cover and do the bulltear mid plate and small hole cam bearings. balance the rotating assembly while you are at it. I think performance wise the lunati cam i am running matched to a performer intake is a good compromise and strong offroad performing setup.

here are some dyno numbers and cam comparisons etc:
290 hp and 380 ft/lbs at the rear wheels: http://www.bulltear.com/forums/viewtopic.php?t=10100


i am running the lunati .484/.507 213/220 @.050 112 lobe seperation with manifold and a performer intake and 670 gm TBI. i can idle all day at 525 rpm, it'll idle down to 200-350 rpm and hold it, come back up nice and smooth and then the bugger will still run hard right up to the 5000-5500 ball park. i went a little over built using forged bulltear pistons, arp bolts and arp main studs and ported out my heads and ported out manifolds then dual 2.5 inch exhaust i think my setup is as good as i wanted it to be. i wanted a motor that would rotate the tires, lug like a bastard over the rocks and still pull hard. if i had a carb on there things wouild be a little snappier on the top end but tbi is what i wanted this go around for rock solid idling and altitude changes sea level to the rubicon is a stretch for a carb without constantly re-adjusting.


engle makes cams that really take advantage of the large lifters in these motors

If you run a carb the rochester and the holley TA are both good carbs. my TA took awhile to get dialed, i preffer the small primaries in the Rochester Qjet offroad it had a little better manners