Picking a good cam for emissions and towing in a 401 build.

[derf]

I've begun the parts accumulation for my 401 build. It's a good 1978 block from a full size Jeep. It has less than .010 wear top to bottom in every cylinder. Minor surface rust in #8 cylinder. If it doesn't clean up, I'll resleeve it. Otherwise it's in good shape. Crank is good. Heads are in good shape but will get rebuilt with maybe a minor cleanup on the runners.

The engine is going in my 86 J10 in place of the 360. I have a Holley Avenger TBI setup (550-400) on an Edelbrock Performer intake on the 360 now and that will go on the 401. Basically stock exhaust setup. It has the TBI's O2 sensor just before the new cat.

The 360 is bolted via an adapter to a 700R4. I already have the 401 specific flex plate from Novak that will let the 401 slip right in place. I'm running 4.56 gears in the J20 axles and 315/75R16 (35") tires. I run roughly 2,200 RPMs on the freeway at 70.

My goals for the engine, in order of priority:

1. It has to pass emissions. This is not negotiable. The fuel injection helps over the carburetor but I can't run a cam that makes me blow my emissions test at the tailpipe. (and yes, I know running a 401 in place of a 360 is technically not right but what are the chances the inspector will actually look under the engine mount to know the difference?)

2. The fuel injection system needs 11" of vacuum at idle or more to run right without a lot of tuning.

3. I want to make good torque for towing and hauling. I don't want to lose my low end torque for the sake of top end horsepower.

The cams I've been looking at so far have durations @ .050 in the 20x-22x range with valve lifts in the high .4xx range. Does anyone have much real world experience running a 401 in an emissions county with an aftermarket cam and can they shed some light on my choices? I've heard from people who run 360's and that's all well and good but a 401 has a fair bit more displacement with the same heads and valves so I'm thinking a slightly bigger cam will be a better choice.

Thanks everyone in advance for all your help.

p.s. Gratuitous pictures of the truck here: http://www.grimmjeeper.com/TruckNorris/

[tufcj]

Is the wear .010 or .001? If .010 then it's time for a bore anyway. I think the taper limit is .003", it's usually widest in the center of the bore. I ran the Edelbrock performer package (cam, lifters, intake) in my 360 rock crawler with Howell EFI. It passed emissions easily and had lots of torque. It didn't rev really high, ran out of steam at about 4500 rpm, but I would recommend it. The Summit 8600 cam might be a good choice also.

Bob
tufcj

[derf]

Is the wear .010 or .001? If .010 then it's time for a bore anyway. I think the taper limit is .003", it's usually widest in the center of the bore.

It's under .010 but over the taper limit. A well used block that has not been rebuilt and is a good candidate for an overbore. I guess I forgot to say that I was most likely going to bore it and get new pistons. I'm looking at bumping compression ratio just a touch, with a goal of no more than 9.0:1. I want to run on regular gas.

I ran the Edelbrock performer package (cam, lifters, intake) in my 360 rock crawler with Howell EFI. It passed emissions easily and had lots of torque. It didn't rev really high, ran out of steam at about 4500 rpm, but I would recommend it. The Summit 8600 cam might be a good choice also.

Bob
tufcj

Thanks for that info.

I'd rather have a cam that lets me get into the 5,000-5,500 range before it's choking out. If you're dropping off with the 360 at 4500, I bet the 401 would drop off even sooner. Though that Howell is a 2bbl TBI, right? Maybe that's the limiting factor?

The Summit cam is on the list.

I've been looking a the Howards 310021-14. It's 223/223 with .480/.480 lift and 114 LSA. I've been told (by people on the internet so I'm not sure if it's true or not) that a single pattern cam will improve low end torque while maybe shaving a bit off the top end.

The Howards 3124801-11 is a bit less aggressive but still single pattern. It's 215/215 with .475/.475 lift and 111 LSA.

They also make a cam that's very close to the Edelbrock Performer. It's off by a degree on both duration numbers and LSA while the lifts are off by less than .010. It's quite a bit cheaper than the Edelbrock so I may give that a try if I want a cam in that range.

I've also looked at the Comp Cams XE256H which is 212/218 with .477/.484 lift and 110 LSA. It's a dual pattern that's only slightly more aggressive than the Edelbrock.

The Comp XE262H10 is 218/224 with .493/.500 lift and a 110 LSA. That's the same duration as the Summit 8600 with a hair more lift and 2 degrees less LSA. I remember 10 years ago hearing about Summit cams having low quality but I wonder if that was when they were switching to less zinc in the oil.

My biggest question is how these various grinds will affect emissions. I may just have to try one of the more aggressive ones and take it to be checked. If it's a problem, I can always swap in a different cam and give it another try.

[tufcj]

I don't think it was the EFI. I was running a big block throttle body that flowed about 590 CFM. It actually ran better with the 2 BBL TBI than it did with a 650 CFM Holley. I like split duration/split lift profiles, although I don't know how they do for emissions since both my AMX and Rogue (both 390s) are emissions exempt. I'm a big fan of Crower cams, they have a pretty good selection for AMC.

Bob
tufcj

[derf]

I don't think it was the EFI. I was running a big block throttle body that flowed about 590 CFM. It actually ran better with the 2 BBL TBI than it did with a 650 CFM Holley.

Sounds reasonable. The 700 CFM throttle body in the system I have should be just fine for my build then. :)

I like split duration/split lift profiles, although I don't know how they do for emissions since both my AMX and Rogue (both 390s) are emissions exempt. I'm a big fan of Crower cams, they have a pretty good selection for AMC.

Bob
tufcj

They do seem to have a good variety. All in line with all the other choices. I almost wonder if I should just put them all on a piece of paper and throw a dart at it to pick on... There's just too many choices.

[tufcj]

Might be the best way...... I think if you keep lift in the .480-.500 range, advertised duration around 280, and a LSA of 110-114, the cam will do what you want. (lower LSA gives a more lopey idle, higher LSA will give you a smoother idle and more vacuum). AMCs like to breathe, the 360/401 valves are the same size as the legendary Chevy "fuelie" heads. You have to watch lifts over .500 for valve retainer to guide clearance. Have the heads machined for positive valve seals if you have a valve job done.

Bob
tufcj

[derf]

Thanks for all of that.

And since I have you on the line and you're near me, do you have a good recommendation for a shop in the Denver area to do the work?

[tufcj]

I've always done my own engine assembly. I come from a family that raced stock cars. I've used Colorado Custom Cylinder Heads for all my machine work on the last 3 engines I've built. They do great work, but aren't the fastest. I'll PM you some additional info.

Bob
tufcj