Learn me V8 camshafts (AMC content)

I cashed in some marital equity and bought an old Jeep. It's a third vehicle and mostly going to be used to cruise around town and occasionally camping in the hills. Not a dedicated trail rig. More like an inexpensive mid-life crisis project. Convertible, V8, problems galore. It's a 1973 Commando with a factory 304 V8 and 3-speed.

I've never really worked on a motor. I figure this is as basic as they come so I might as well get my hands dirty. It's currently configured with a Motorcraft 2100/2150 2-bbl carb on the factory 2bbl intake. I'm proposing to find an Edelbrock Performer intake, an adapter, and bolt a Quadrajet. I understand the Qjets are polarizing, but it sounds like they can work pretty well if you're willing to put in the time to learn them. That's my plan.

So my theoretical (and specific) question is about the camshaft. I want to open up the V8 as much as possible without losing drivability or trail manners. But I also don't want to spend the time and money swapping in a cam shaft to have it drive the same. Any suggestions on camshaft sizing? I'm reading that I should stick with duration under 280, lift under .5 and shoot for LSA between 110-112. The cam I was eyeing meets most of those, but has more duration:

http://www.summitracing.com/parts/sum-8600

I've read that this cam works well in the 360 and 401 V8s, but I'm worried it will overwhelm my little 304. I've also posted a similar thread at Bulltear.

Is this too much cam? Does the manual transmission help to offset the issues of too much cam? Is the Qjet a poor choice? Any other V8 advice?

To be perfectly honest, stick with a 2-barrel carb and an RV cam.

It's in a truck, make it a truck motor.

That mean keeping charge velocity high at low rpm for better cylinder filling.

Think small valves and intake ports.

For the price of the parts you're contemplating you could probably find a stock 360/401 and not have to go into it at all. Not common but they're out there.

What are you trying to do with the motor?

That should be the first question. Most of the Jeep motors I've had never saw north of 4500 RPM. That is a huge cam for a 304 and will probably actually hurt performance for that motor. Mellings makes a good RV style cam that is not that expensive.

Keep in mind, when you install that into an older motor you need to install new lifters and should probably replace the timing chain and valve springs as well.

The thing that killed most of the performance for the 304 motor was compression. Typically they were 8.0 to 1 or less. Without building up the compression, adding a bunch of fuel and a big cam is a mistake.

The problem with finding a 360 is that it may be in worse shape than the 304. The 401, unless the seller doesn't know what he's got, is probably going for more money these days since they're the biggest AMC available.

I kind of like this cam, based on a glance at the specs. It isn't much more money when you consider it comes with new lifters, which you'll need anyway;

http://www.summitracing.com/parts/hrs-cl312481-11/overview/make/american-motors

I'd want to find a manifold that doesn't require a spread bore to square bore adapter as I'm not sure what that would do to fuel mixture. A QJet in theory should be tune-able to that size of engine as they came on 3.8 V6's from GM as well as 318's from Dodge. I kind of like the idea of getting a bunch of GM 350 truck parts and getting a TBI setup going. In theory you could reuse the factory intake manifold but it may require an adapter. That would also require some custom tuning. Another option could be a 650 Holley, such as their vacuum secondary carbs.

Lot of options. Curious what other people chime in with.

you need to match compression with the cam... too much compression premium fuel required, too little compression no power, feels like a dog.

Re-reading I see you're thinking of an Edelbrock intake and Q-jet. Why not hit the easy button and buy a performer package?* You'll get cam/intake/carb as a matched set with specs showing what it should do on a stock engine.

*assuming one is available and/or they still sell that way. It's been a long time since I shopped for old V8 stuff.

Keep in mind that an AMC uses a giant timing cover that also houses the oil pump, so an "in-car" camshaft change is a very big job. Your oil pan will also leak, because it is supposed to go on after the timing cover. It is a flat-tappet motor, so you will have to buy new lifters and use proper high ZDDP break-in oil. Also, the 304 has small bores (3.75") and valve sizes (1.787"), so you are never really going to "wake it up" without some other serious work. The best thing you can do is put a set of quality headers on it that use good flanges to match the dog-leg ports, and go with a better intake/carb combo. A regular Edelbrock Performer (not the RPM or Air-Gap) with a 600cfm AFB or similar carburetor will be your most economical bet. Upgrade the ignition and enjoy the torque!

bmw88rider wrote: What are you trying to do with the motor?

I was hoping I could bump it up to 200-250 hp with decent road manners for about $500.

A 360 swap probably gets me to the same place for similar money. 401s tend to go for a lot more than $500.

With the current gearing and tires it feels like it has an abundance of off-idle torque. I'd be willing to trade some of that for a little more top end. I also hoped that the manual transmission would afford me some leeway with a slightly bigger cam.

Sounds like the compression ratio will be a limiting factor. I hadn't considered that. That's why I'm here asking. Thanks for the suggestions.

In reply to Junkyard_Dog:

http://www.jegs.com/i/Edelbrock/350/2131PK/10002/-1

600 or 650cfm carb (I guess you can pick?), split pattern cam that favors the exhaust side and not a lot of lift but more duration than the Howard's stick I found. Need someone smart on cams & AMC's to get a read on this maybe.

The thing about the Qjet is they have tiny primaries. If your foots not buried and the secondaries are not open you'll have better throttle response and likely better fuel economy than with a 2bbl, but, when you need them, those big secondaries open and you'll get all the power that you'd be giving up with a 2bbl.

The hard part is keeping out of secondaries, it's a very addicting thing

Note: I am a Qjet fanboy, I haven't found a Holley, Edelbrock or Carter that I like near as much as a Qjet.

Having only had the luxury to drive one v8 jeep, be happy you dont have the 4.2, that sucker with the 3 speed sucks. But I suggest you do a full tuneup with as suggested a 4bbl intake with matching carb. Dont monkey with the square to spread bore adapter get a carb that fits your intake. I enjoy the edelbrock carbs, I slapped an avs thunder series on an old 327 vette and without tuning ran damn near perfect, best its run in years. But do the intake and carb, full tuneup maybe pertronix ignition bits in the distributor to ditch points and maybe headers of you need a couple more hp. After hearing how much harder an in car cam swap is compared to other v8s id personally put some aluminum aftermarket heads on first. Trust me when I say you dont want high rpm power in that jeep, expecially if you have the 3 speed. Stock cam or rv cam is what it needs

Nick_Comstock wrote: Note: I am a Qjet fanboy, I haven't found a Holley, Edelbrock or Carter that I like near as much as a Qjet.

I like them too, but tuning, especially with a mix-n-match combo can be a PITA. The nice thing about a Performer setup is that a few engineers much smarter than me got paid good money to come up with something that works right out of the box.

To put it in GRM speak it's like getting an FM turbo kit for a Miata or building it yourself. Evey last person I've known who built it themselves spent 1.5 times the cost of the FM kit and it still doesn't run right. It might make slightly more power, but it's a bear to live with. I've never seen an FM kit installed correctly that gives any real problems.

In reply to Junkyard_Dog:

Ya' know, it's been so long since I've messed with a Q-jet that I would certainly need to take a refresher course. I rebuilt my first one at 15 and several more over the years. I had a couple very experienced guy's to learn from though, they are a good carb when set properly.

If you're dead set on a 4 barrel get a vacuum secondary madel. Mechanical secondary and double pumper carbs get all the glory, but when it comes to drive ability, you can't beat a vac secondary. At least in a carb.

A cousin of mine built this wild 350 for his 73 Nova, put a 750 double pumper on it and don't get me wrong. It would go like stink up top, but it was a bucking, cussing, unpleasant mule at anything other than full boogie. I snagged a 750 vac secondary holly and rebuilt it for him. After it was set up, it was a completely different animal around town. (Same cousin that thinks I'm nuts for playing with 4cylinders in a "girls" car as well. At least till I took him for a ride in the challenge car last time he was in town. )

In reply to Spinout007:

I agree with this, 9 times out of 10 always go with vac secondaries. First 4bbl carb I rebuilt was a 750 holley double pumper I slapped on a mildly built 400 pontiac, it would boil the tires in top gear but if you werent all the way in the throttle it ran like ass. Sounded gnarly at idle though haha

I would think getting 200HP+ (that is, make it peppy) out of a 150hp smog motor can be accomplished mostly with exhaust work and tuning. If it has a pellet bed cat on it, that alone is probably sucking 20+ hp. I'd make sure it's exhaling well and do a general desmog, play with the timing (can probably go for a couple more degrees), set up a cold air intake if it's sucking engine bay air. If it's points switch to something electronic (and feed it with a new 12 gauge wire). See what you've got at that point.

As others have mentioned, a 4 barrel won't gain much on a 5 liter truck engine. The vacuum secondary qjet does work well when oversized though, and with tuning, may squeeze out a little more efficiency.

Upgrade to a four barrel and see how you like it. Two barrels are just there because they were adequate and cheaper to produce, not because they did anything better than a 4 barrel would've/

A four barrel will give you better economy (your primaries will be smaller and do not need to be metered to feed the entire RPM range on their own) and better power when you need it (truck engine or not, I'll bet you it can pull through more CFM than that carb is letting it)

An older carb will work great. I've had both a Carter AFV off an early 70s New Yorker (spring-loaded door instead of weighted door) and a Quadrajet (rebuilt off-the-shelf from a friend, Caddy-spec) on my engine and both are leaps and bounds better than the old Carter BBD the car came with. I never got better than 14mpg on my old 2 barrel, usually 10 or 12. With my AFV I could get 15-16 flat highway and with the Quadrajet I've gotten an honest 18 mpg highway. I had to mess with the AFV a lot, but I've only had to take the top of the Qjet off once, and that was to knock out the plug for the adjustable part throttle screw. I've only had to adjust the choke for the weather otherwise in my last year-plus and 2000-some miles I've put on the thing.

I got my Qjet for free and it was rebuilt by a Caddy guy at some point (carb was a spare and ended up being undersized for his car) but quadrajetparts.com is a great part and tech resource if you find a decent rebuildable one. I run mine on a regular spread-bore Performer manifold with a thick Moroso phenolic spacer.

twolittlebroncos wrote: I'm proposing to find an Edelbrock Performer intake, an adapter, and bolt a Quadrajet. I understand the Qjets are polarizing, but it sounds like they can work pretty well if you're willing to put in the time to learn them. That's my plan.

The Qjet is by far the most accurately metering carb available. It is complex, but its reliable and has far more compensation for fuel curves based on vacuum feedback and throttle position. Holleys and Edelbrocks (Carters) tend to take three "stabs" at fuel; an idle screw, primary jets/rods, and secondary jets/rods. The air/fuel ratios tend to be all over the place. Qjets were able to pass EPA mandates as late as 1989, they were used on everything from 3.8 V6s up to the Cadillac 500. They rock.

Regarding adapting it... its a no-no. You must put a Qjet on a spreadbore intake. Period. Adapters exist, but they are nightmares. The primaries hit the adapter and lose all velocity, and the secondaries hit the adapter like a choke. At best, you will be removing all the benefits of using a Qjet in the first place. Worst case, you'll have serious drivability issues.

90% of street V8s are over carbed. On a small displacement truck motor, there is really zero need for a 4-barrel. It adds complexity, tuning, and fuel consumption that you don't need. Even a pretty hot 304 would probably only benefit slightly from a 4-barrel. The thing that people tend to forget is that an intake restriction only affects things at or near the redline. I personally would much rather give up 2hp at redline (where a jeep will rarely be) than to worry about all the work and tuning of swapping intakes and carbs.

http://www.summitracing.com/parts/sum-8600 I've read that this cam works well in the 360 and 401 V8s, but I'm worried it will overwhelm my little 304. I've also posted a similar thread at Bulltear.

In my opinion, its not too much cam for the jeep, but its way too much for the motor in its current stock state. It will be a mismatch for the compression and head flow. The 304 in there was designed with 3800-rpms in mind for peak RPM. Its likely the 8.1:1 compression as well with dished pistons. They were made as a tractor engine. This cam will be bleeding cylinder pressure at low RPMs where you should be taking advantage the intake velocity for torque. Then when the cam starts to shine, the intake ports will be wheezing hard and won't keep up with the cam's demands. If you go with this cam, you will be a zillion times happier if you do a head swap/head work. That cam needs 9:1 or more.

Is this too much cam? Does the manual transmission help to offset the issues of too much cam? Is the Qjet a poor choice? Any other V8 advice?

In the range of cams you're choosing, the transmission type won't affect or offset cam choice. Manuals are a tough choice if you have a lumpy-idle cam since its hard to negotiate slow speeds with the surging. Automatics of course have the tune-ability of stall speed. But the difference between manual/auto is not nearly as important as ratio.

The single most important part of the transmission/axle you need to consider is the final drive ratios. Upping the cam obviously raises the torque peak RPM, so deeper gearing will add more mechanical advantage for the reduced low-rpm torque. With a 3-speed you don't have much choice. That transmission likely has extremely wide ratio splits to get a low enough first and a 1:1 third. Think of choosing a cam with the widest possible torque curve to compensate for that. I wouldn't worry about a transmission swap to match ratios to the engine output. You're working within a small range of torque peaks. Where you really need to worry about matching ratios is in the higher-torque-peak engines and racing. If you want to swap trannys for an extra gear, a granny gear, or OD, feel free to choose one that fits and don't worry too much about ratios. If you were building a 10:1 engine with a 234/244 cam, then it would be important.

If you're not into head work/swap, think of a cam in the sub-210 duration. Something like a 198/208-112 lsa would bump up the midrange torque without killing low end and give you some more top end. Any more than that and I would strongly suggest heads and headers to get compression up and increase flow to match. Otherwise, you'll just have a dog. Keep in mind, the cam that came from the factory is probably about 180/185 duration. Its tiny. You can't deviate far from that without a comprehensive set of engine upgrades.

But... I must say.... Learn Qjets. Fabulous carb, works wonderfully, and most American engines can be had with a spreadbore intake. I just put a Qjet on a buddy's Ford 460, and I know a guy with one on a Dodge 440. Once you dig into a few, they are super easy. I'm getting to the point now where I'm doing custom mods to Qjets with pretty good success.

304s are kind of low on potential. They are like 305 chevys, throwing money at them is kind of silly. If you want to put $500 into performance parts, put it into a 360 swap. It will have plenty of power to propel the jeep in stock form, and if you want to add more power the 360 will be the better performer.

As far as what you have now, if you want to learn carbs the motorcraft 2100 is fantastic. It is simple as a lawn mower carb. You can rebuild one in 15 minutes. Plus they are awesome offroad because they dont mind angles at all. I had one on my 258. I drove the front of the jeep up a rock ledge until it was standing on its rear bumper, I took my foot off the gas, and that thing sat there and idled perfect.

So I say run what you brung, and do the swap this winter.

A thought occurred, turbo? ~5psi out of some little turbo (or pair thereof) that will almost always be spooled. You've got the right compression ratio for it. You could probably keep it under $500 using used/junkyard parts, blow through the carb already on it, probably no intercooler. Pretty much just the turbo, plumbing and a FPR, wideband, maybe some sort of rigged up knock sensor, a little tuning. I would think at 200-250 HP it would be pretty reliable assuming proper tuning unless nobody has told me that AMC V8s are comically weak. Might even handle 87 octane.

YUP TURBO it, just right comp. ratio, a mild cam works great with a turbo(short duration keeps the boost up,) wide overlap lets the boost out the exhaust!

of course tuning will take some time, but for a stock engineits doable.

Keep the current drivetrain stock with just someone updates for reliability ( like eliminating points) and gather up parts and knowledge for a future upgrade.

Learn what you like and don't like about the current set up first. Plus you don't want to go too far on the current motor until you get some time on it to find any existing problems.

Then when your ready, make the big changes.

Like...Not to go to far off topic (or into blue sky project space), but what about a 4.0 I-6? Reasonable stock power, good reliability, and fuel injected.

ronbros9 wrote: YUP TURBO it, just right comp. ratio, a mild cam works great with a turbo(short duration keeps the boost up,) wide overlap lets the boost out the exhaust!

Short duration keeps the boost up? That's the last thing you want, and no, more overlap does not "let the boost out the exhaust".

That cam, BTW is an excellent choice.

jstand wrote: Keep the current drivetrain stock with just someone updates for reliability ( like eliminating points) and gather up parts and knowledge for a future upgrade.

This will be my plan. Electronic ignition (which could swap to a 360 or 401) and leave it alone. Thanks for all the advice. Good info in this thread. Here are some of my takeaways:

1. Don't need more CFM with this motor
2. Cam install is more involved than I thought
3. A displacement upgrade (360 or 401) is likely the least cost/hp
4. Quadrajet on a square bore intake is a no-no