Camshaft Recommendations?

[Niedhogg]

I'm trying to get a little more power out of my AMC 304 , and could use some suggestions..

I have a '79 AMC 304 that was a totally stock smog engine when I started. I have removed all the emissions, and have added headers, an Edelbrock Performer intake, and a 470cfm Holley truck avenger, and converted the ignition to HEI... It just seems like it should have better accelaration, it's really sluggish, and it is using copius amounts of gasoline. I know there are other factors, I am unsure of the gearing and I have 35" tires. I am planning to check the float levels on the carb today as I think the rear bowl may be running over, because the last time I had the carb off the back two barrels were really wet at the base gasket. The carb is new from Holley and has the factory settings. Could that be causing my sluggishness?

I was also going to upgrade the cam during the build, but I had a time restriction that I just didn't feel like I could finish the project if I'd tackeled that too, so, what would you guys suggest for a cam size for my motor, I'm not really worried about the gas cosumption, but for all the gas it's using I'd like to at least have the power to show for it..

 

[Manhattan]

How do you use the Jeep? If it's all street, then a cam might be the way to go. But - and it's a big but - if you drive the Jeep off road much (ever) I'd stick with a stock or very mild cam. As you know, on the trail, you spend 90% of your time under 1,200 rpm - and a lot of it under 900 rpm. A "big" cam, while fun on the street, will really suck on the trail. Crawling with a lopey motor is a bitch.

It sounds like the top side of the motor is dead on - right size carb', the ignition, etc. Those carb's are usually set pretty much perfectly out of the box too.

You've got headers... what's the rest of the exhaust system - duals? 2.5"? 1 or 2 mufflers? Cats? Wondering if you've lost too much back pressure?

Do the math on the axle and report back - if you've got 3.31 gears and 35s... your answer might be right there.

 

[Niedhogg]

How do you use the Jeep? If it's all street, then a cam might be the way to go. But - and it's a big but - if you drive the Jeep off road much (ever) I'd stick with a stock or very mild cam. As you know, on the trail, you spend 90% of your time under 1,200 rpm - and a lot of it under 900 rpm. A "big" cam, while fun on the street, will really suck on the trail. Crawling with a lopey motor is a bitch.

It sounds like the top side of the motor is dead on - right size carb', the ignition, etc. Those carb's are usually set pretty much perfectly out of the box too.

You've got headers... what's the rest of the exhaust system - duals? 2.5"? 1 or 2 mufflers? Cats? Wondering if you've lost too much back pressure?

Do the math on the axle and report back - if you've got 3.31 gears and 35s... your answer might be right there.

Ok, so I have dual 2-1/2" through mufflers all the way out the back, and right now, I'm just driving it. But, I AM going to wheel it, AND I'm planning on towing a small trailer with camping gear, or my Harley, depending on the weekend. And all I'm thinking about, cam wise, is just like the first notch, rv type cam. I'll try to check the gearing this weekend, but like I said, it barely gets out of it's own way now which I figure is because of the gearing, so I can't imagine trying to tow a trailer, or even trying to get through some deep mud. The cams I've been looking at are just basic, off-idle type torque cams. Plus, right now I'm running an automatic.

 

[Old Dog]

I have a comp cams 4x4 cam in mine (1000-5200 rpm) and like it.
I have a 350 chevy with an auto.

I'm betting you need a gear change.

 

[Niedhogg]

I have a comp cams 4x4 cam in mine (1000-5200 rpm) and like it.
I have a 350 chevy with an auto.

I'm betting you need a gear change.

I'll be working on the gear change later this summer with any luck, along with axle upgrades. I figured the cam change would be a much cheaper route to some more power right now, and then the gear change would just accentuate the power gain, right?? I might have enough to work over the heads a bit, would that be worth my time and money? What can be done with the factory heads? I can't imagine it would hurt anything..

 

[jeepboy45]

I'd go with a cam with a bit longer than normal duration. The main problem with a AMC 304 is the heads.... the valves are SMALL....

As was mentioned, you dont want a ton of cam lope, but you need to get it to breathe

.

 

[Niedhogg]

I'd go with a cam with a bit longer than normal duration. The main problem with a AMC 304 is the heads.... the valves are SMALL....

As was mentioned, you dont want a ton of cam lope, but you need to get it to breathe

.

Kind of what I thought, I'm sure someone makes bigger valves for them. I used to have a '74 AMX in high school, pretty sure there was some hp stuff available then...

 

[CJ]

Kind of what I thought, I'm sure someone makes bigger valves for them. I used to have a '74 AMX in high school, pretty sure there was some hp stuff available then...

You cannot put larger valves in a AMC 304 head without notching the cylinder walls or the valves will hit. Also, since the valves are shrouded, negligible HP gains are realized.

 

[jeepboy45]

You cannot put larger valves in a AMC 304 head without notching the cylinder walls or the valves will hit. Also, since the valves are shrouded, negligible HP gains are realized.

x2 .. thats what I was gonna say.. but CJ is quicker (AND he has the advantage of owning the site and probably SLOWED down my post so he'd seem smarter!!!) LOL .............Just kidding CJ.... (great, I'm gonna get reprimanded for this....haha)

 

[CJim7]

Yeah...there's a lot involved in going with larger valves...the headwork alone is worth the price of a couple new engines.
And for that, you could pick up some AMC aluminum performance heads.

Have you tried playing around with your timing?

 

[jasonmark1993]

If you're looking for more power Id get a bigger carb for starters I don't have any experience with a AMC 304 , but unless the runners and valves are super small, Id go with a 600.

I don't know though, Holley makes those for a reason.

 

[Niedhogg]

If you're looking for more power Id get a bigger carb for starters I don't have any experience with a AMC 304 , but unless the runners and valves are super small, Id go with a 600.

I don't know though, Holley makes those for a reason.

Well in all my researching that went into my carb choice, I found that the AMC 304 simply just cannot use that type of cfm in most cases, especially in the rpm range most people use their Jeeps..

And it's too bad about the heads, not being able to upgrade the valves and all. No big deal, for now just a mild cam upgrade would have to be the cat's meow for these motors, probably wakes them up quite a bit.

My AMX was no slouch, back in the day, it was quick but not real fast. Think it topped out at around 110, and I'm pretty sure it was a 2bbl.

 

[jasonmark1993]

I think someone mentioned checking the timing; always a good place to start.

That can definitely make it feel sluggish; generally an overly rich or lean condition will cause bucking.

Aside from getting a wideband, you can pull a plug or two to see how its running. They should be a light golden color. Anything one way or the other suggests a lean or rich condition or some oil burning.

Good plan on checking the gearing, although power is power. At some point, you will be in higher rpms in a given gear and it should feel like it has good power.

 

[Niedhogg]

I think someone mentioned checking the timing; always a good place to start.

That can definitely make it feel sluggish; generally an overly rich or lean condition will cause bucking.

Aside from getting a wideband, you can pull a plug or two to see how its running. They should be a light golden color. Anything one way or the other suggests a lean or rich condition or some oil burning.

Good plan on checking the gearing, although power is power. At some point, you will be in higher rpms in a given gear and it should feel like it has good power.

Timing is something I was wondering about, I've checked it several times and I have it set at 12 btc, but I do wonder if the advance on my new distributer is working correctly, or even if my new carb is drawing any vacuum for the advance. If I unplug the vacuum from the distributer, I get no change in idle. Seems like every distributer I've ever worked on has had an idle change when the vacuum is taken away from the distributer. I know when I chose this distributer, which is an economical (Pro-Tech, I believe is the brand) version of the HEI style distributors, people were saying it may give me too much advance, but I don't think it is, how can I tell if it's working? Watch it with a timing light to see if it change with accelaration? or does it need to be under load to advance the timing?

 

[jeepboy45]

Timing is something I was wondering about, I've checked it several times and I have it set at 12 btc, but I do wonder if the advance on my new distributer is working correctly, or even if my new carb is drawing any vacuum for the advance. If I unplug the vacuum from the distributer, I get no change in idle. Seems like every distributer I've ever worked on has had an idle change when the vacuum is taken away from the distributer. I know when I chose this distributer, which is an economical (Pro-Tech, I believe is the brand) version of the HEI style distributors, people were saying it may give me too much advance, but I don't think it is, how can I tell if it's working? Watch it with a timing light to see if it change with accelaration? or does it need to be under load to advance the timing?

You arent going to have vacuum at idle on that line coming from the carb that goes to the distributor....

You could try sucking on the end of the hose you removed from the carb. If the distributor is actually advancing, the idle should change. You will also notice that when that line is removed from the carb, there isnt any real sucking sound from vacuum. But if you idle it up, it should start to suck more.

 

[Niedhogg]

You arent going to have vacuum at idle on that line coming from the carb that goes to the distributor....

You could try sucking on the end of the hose you removed from the carb. If the distributor is actually advancing, the idle should change. You will also notice that when that line is removed from the carb, there isnt any real sucking sound from vacuum. But if you idle it up, it should start to suck more.

Ok, so the vacuum seems to be working fine on both the carb and the distributor. We'll be able to check the gearing tomorrow..

 

[jasonmark1993]

I cant remember if you said you had a tach on this jeep.

Unless you have really tall gears and are flooring it at idle, you're gearing isnt the problem. Lets say you have 3.73s with your 35s, I bet you can hit 35 in 1st gear MAX. You should feel like it pulls pretty hard once you get moving.

My AMC 304 pulled hard up to about 2500; kept reving nicely but was clearly choked by the two barrel. It basically flatlined at 2500.

Im not sure what the AMC 304 like for total timing, but Im guessing you should see somewhere around 30 degress.

 

[Niedhogg]

I cant remember if you said you had a tach on this jeep.

Unless you have really tall gears and are flooring it at idle, you're gearing isnt the problem. Lets say you have 3.73s with your 35s, I bet you can hit 35 in 1st gear MAX. You should feel like it pulls pretty hard once you get moving.

My AMC 304 pulled hard up to about 2500; kept reving nicely but was clearly choked by the two barrel. It basically flatlined at 2500.

Im not sure what the AMC 304 like for total timing, but Im guessing you should see somewhere around 30 degress.

I need to get back on this issue, sorry, I've been to busy to tinker with it and I'm still having a rich issue with this carb..

If I floor it, it does seem to have some power and shifts through the gears well, and has a pretty firm shift which I like, but you can't drive this thing anywhere without smelling like a gas station when you get there..

Like tonight, for instance, we hopped in it to run to town after our bike ride today, had a pretty strong head wind of, oh I'd say 20-25 mph, and it could hardly get to speed, unless I floored it, but I had to use a heavy foot to maintain speed. Got out of the store, fired it up, had a little backfire sneeze, and black smoke pours from the exhaust when I rev it, and I've seen this before.. on the way home with the tail wind all seems good, like a normal day.. and a very rich exhaust even still..

Do you suppose I need smaller jets, and maybe a lighter vacuum secondary spring? I'm pulling a couple plugs again tomorrow to check color, but last time I looked they barely had any color, couldn't say if it was running rich or lean, they were really clean with just a bit of light tan on one side, which I figured was pretty good, but the way it chokes us on eye burning exhaust fumes you'd think they'd be black..

Maybe a couple more degrees of timing with this hot distributor?

 

[mtnwhlr]

I think you need gears. you are running a 35'' tire so unless you have at least 4.10s you are bogging down that motor. It's like you are pulling around a anchor. All the tuning in the world is not going to fix this.

 

[jeepboy45]

I think you need gears. you are running a 35'' tire so unless you have at least 4.10s you are bogging down that motor. It's like you are pulling around a anchor. All the tuning in the world is not going to fix this.

I agree that he might need to re-gear.... That could explain the sluggishness..

However, even if the engine is working overtime to get the jeep to speed, (because of gearing) it shouldnt be running as rich as it is... There is still something else going on with carb, or timing.

I think you need to get the engine dialed in nicely before you start thinking about re-gearing.

My .02

brian