mild 360 build opinions

[82Waggy]

That is an extremely small camshaft in a AMC 360. From experience the 220-225 duration works extremely well in a AMC V8 above 343CI for low end grunt.

Well, most of the cam manufacturers rate cams with that much duration in the 1500 and up RPM range, with peak numbers near 4000 rpm, and generally recommend an increase in compression ratio to around 9.5:1. With stock compression and gears, I would expect low end to be pretty anemic with something like that.

The Summit 8600 cam has a very late intake closing point (65ABDC) and 53 degrees of overlap, neither of which are good for bottom end torque.

For comparison, don't forget donwags 401 with 9:1CR running a Comp XE256, 212/216 @.050 and only 54ABDC intake closing point with 42degrees overlap - made over 400ftlbs from 2-4400rpm with peak torque of 428 at 3400 and 348hp at 4800 on the dyno.

401's have a higher intake valve size to displacement ratio but more dwell time than a 360, so neither need a lot of overlap to make good power.

Remember that all duration does is shift the point at which peak torque is produced around 500 rpm per each ten degrees of duration - the downside is that too much overlap and a late intake closing point makes bottom end power evaporate.

Anyway, not saying the 8600 won't run in a 360 and may even be better than stock, but I doubt it is the best you can do - especially not without a bump in compression and some taller gears to let the engine rev up quickly.

First piece of advice before choosing a cam should be to analyze seriously what RPM range you are really operating in. Do you really rev over 4000 rpm consistantly or are you typically cruising in the 2000-2500rpm range? Are you willing to increase gear ratio to raise engine speed? Are you willing to accept the decrease in fuel milage that comes with higher rpm operation? Will you change pistons to raise CR? Do you have a free flowing exhaust system? Bet most Jeep operators would do better with lower duration cams.

[jeepsr4ever]

You have to take in the head flow and port volume into account as well. This changes the recommendations from a chevy cam to a AMC. I do agree with you on many points however when your done building your engine you will build more power with the camshaft I recommended over the others. Also take into account the lock up torque converter and the stall that is being used.

[Goose]

ya know guys.. What we really need to do (I say we as in mouse in my pocket) is put a mild engine on the dyno.. much as what we dscribe here and just try the different cams out there and see what the numbers are..

My experience has been Small block chevy and Big block mopar.. and in thos instances the cam mfrs are usually pretty close.. now the AMC which appears to have ports bigger than a 440 mopar..or 454 chev for that matter and will probably outflow them both, has me cornfused ..For instance the edelbrock performer cam that works so well in SBC applications only works well in the 304..why would that be?

[82Waggy]

You have to take in the head flow and port volume into account as well. This changes the recommendations from a chevy cam to a AMC. I do agree with you on many points however when your done building your engine you will build more power with the camshaft I recommended over the others. Also take into account the lock up torque converter and the stall that is being used.

Since the person starting this thread specified "mild 360" at about 200hp with nice torque for use in a Wagoneer, a relatively heavy vehicle, I see no point in discussing high rpm power or high stall torque converters.

If you want to compare an AMC to a Chevy, consider valve size to displacement ratio. A Big Block Chevy can benefit from more duration and overlap due to the relatively small valve size compared to the displacement they have to feed. An AMC 360 has a valve size to displacement ratio very similar to a Chevy small block - cam grinds similar to what works for an SBC will have the same basic results in an AMC 360, though a more aggressive lobe ramp can be taken advantage of in an AMC due to the larger diameter lifters.

I do not dispute that the cam you are recommending is "capable" of making more total power, but only if you are going to increase compression ratio, increase gear ratio and/or stall speed, use headers and a free flowing exhaust, and run premium gas. IF this is what the builder wants to do, OK.

My understanding was he was looking for low end torque in a basically stock rebuild and specifically stated he was "not real interested in big hp" - which suggests to me an rpm range from off idle-4000. With that in mind, a shorter duration cam on a 112 LSA will build better cylinder pressure and make more torque.

[82Waggy]

ya know guys.. What we really need to do (I say we as in mouse in my pocket) is put a mild engine on the dyno.. much as what we dscribe here and just try the different cams out there and see what the numbers are..

My experience has been Small block chevy and Big block mopar.. and in thos instances the cam mfrs are usually pretty close.. now the AMC which appears to have ports bigger than a 440 mopar..or 454 chev for that matter and will probably outflow them both, has me cornfused ..For instance the edelbrock performer cam that works so well in SBC applications only works well in the 304..why would that be?

Love to see that myself Goose.

Another point to be made however is that because AMC heads flow pretty well, extended overlap is not necessary.

But I think everybody knows that long cams need higher compression ratios, right? So I don't understand why I see so many recommend long cams for stock compression engines. And why does the donwag 401 dyno sheet, and others, not seem to prove these points?

[jeepsr4ever]

I wasnt talking about high revs I am talking about making the power at a low rpm without having a cam fall flat on its face at 3000rpm. If you have a small lift and small duration with the large valve sizes AMC head have your velocity and the amount of fuel/air and combustion efficiency can go down. The 304 works well with smaller cams because it has smaller valves. When you take all the parts of what makeup the power in a AMC 343 or larger you will then understand why cams with less than 220 duration or .480 lift dont work as well as cams in that range. Donwag has a good example and did a good job of building his grunt motor however I believe that he could have made more power with a different camshaft. You very close to being accurate 82Wag but without taking into account the head characteristics a cam suggestion may not be as accurate as you have led it to be.

I need a set of 304 heads BTW anyone got a set they will send up here?

[82Waggy]

I wasnt talking about high revs I am talking about making the power at a low rpm without having a cam fall flat on its face at 3000rpm. If you have a small lift and small duration with the large valve sizes AMC head have your velocity and the amount of fuel/air and combustion efficiency can go down. The 304 works well with smaller cams because it has smaller valves. When you take all the parts of what makeup the power in a AMC 343 or larger you will then understand why cams with less than 220 duration or .480 lift dont work as well as cams in that range. Donwag has a good example and did a good job of building his grunt motor however I believe that he could have made more power with a different camshaft. You very close to being accurate 82Wag but without taking into account the head characteristics a cam suggestion may not be as accurate as you have led it to be.

I need a set of 304 heads BTW anyone got a set they will send up here?

I just can't reconcile your points MC. High velocity and large wide open valves at low rpm do not go together. ALL flow data suggests that dogleg heads with 2.025 intake valves start to lose velocity at about .480 or so lift, and there is very little significant difference in flow/velocity between .450 and .480 lift. If a 304 in fact has a relatively smaller valve size to displacement ratio or lower flowing heads than a 360 then it would stand to reason that it would show a benefit of using a cam with more overlap than a 360 (RELATIVELY SPEAKING), assuming exhaust system backpressure did not hinder cylinder scavenging. If you are not running the rpm to take advantage of the port and valve size at max attainable lift, velocity can go down - you can get velocity back up in this circumstance by not opening the valve as far - cubic feet ingested can remain constant. High volume at low velocity, or low volume at high velocity can both equal the same CFM. High valve lift is not always, therefore, the best deal for low rpm engines.

A simple cam fact is that duration in and of itself only shifts the rpm at which peak torque is produced - raise this point and you make more horsepower, but at some sacrifice to low rpm torque due to the relatively later intake closing point. It is possible to regain some of the low rpm torque loss by raising compression ratio, but, as I have tried to convey, doing so means addressing higher octane fuel use, higher gear ratios, free flowing exhaust, etc. The question is at what point do you draw the line.

Use too much overlap with a restrictive (stock style) exhaust system and you start diluting the intake charge at low rpm - once again, bottom end power suffers.

Sure donwag could probably increase his peak numbers with more duration and higher rpm, assuming the intake closing point did not fall behind where it is now. IMO he could also increase peak torque within his current rpm range, widen his torque curve, and even increase peak hp numbers, and do all of that at a lower rpm than where his peak numbers fall now -simply by going to a cam with a 112LSA and slightly less duration.


Look, I am not trying to be a contrarian here. If there is something special about an AMC engine in these regards that I have overlooked, please enlighten me.

[jeepsr4ever]

82 Sorry I have been so brief on my replies...its been a hectic day. I am not a cam expert and will not claim to be. The factory cams are as follows

304/360 Intake duration 263.5
401 intake duration 296.32
304/360 Intake duration 263.5
401 intake duration 303.55

Valve overlap
304/360 41.5
401 68.32

Cam lift
304/360 .266
401 .286

Here is my experience with the 256xe. Every single one I have used or sold minus one (Donwag) have had low power at idle and dumped off at 3200rpm. They have been a huge dissapointment. The 256Xe specs are as follows

Duration 256/268
Lift .477/.484

We have had bad experiences building power with this cam over stock and we believe it is due to the low lift and duration. On the flipside we had great experience on a 304 with a Edelbrock performer camshaft, mixed results with a 360 and poor results with a 401. Here are the numbers for the Edelbrock.

Duration 278/ 288
Lift .448/ .472

The summit camshaft (K8600) had given the greatest amount of power from idle to 4000rpm in a 360 and 401 and from 2000-4500rpm in a 304. Here is the Summit numbers

Duration 272/ 282
Lift .472/ .496

The Sumit cam seemed to give the best power out of the 3 for the low end. Personally I have built just over 100 AMC V8s and experienced about 25 of them in my vehicles. These opinions I posted are based on a .030 bore with nothing special about compression other than a small hike from oversizing the cylinder from boring. I understand LSA's effects and lift/duration numbers but in my experience the rules tweak with a AMC V8 I dont think they change all that much but a Chevy grind camshaft certainly doesnt make as much power as a grind tailored to a AMC V8. Some of the smaller cam houses like Lazer have some specs posted.

Lazer cam specs, although some will disagree that these make power in their range





Lazer has specs that closer represent what your recommending than what I am posting. I guess knowing the vehicle tha the postee is trying to cam really made my decision. Like I said I am not going to pretend to be a camshaft expert but I have alot of experience with these low end camshafts and some of these buggers dont even have a place in a AMC engine

[mycj7]

I put the Comp Cams 268h in my 360 on a recent rebuild (was gonna be either that cam or the 256XE cam). Loads of low end, strong until 5,000 rpm. I built this one for my CJ that will rarely hit rpm's that high, and am so far impressed. Best guess is 325 hp and 400 ft lbs, without doing anything crazy during the rebuild. It has enough power to smoke a 37" Bogger on pavement.

The idle has a bit of lope to it, but barely noticable. I run the Holley Pro- Jection 2D throttle body fuel injection and it has a very snappy throttle response.

This was my first engine rebuild and I did a lot researching/reading on line (tons of great info on this sight and the AMC forums) also talked to some friends that rebuilt their 360's to see what worked for them.

I had the block bored .030, new pistons, block/heads shot peened, magnafluxed, crank ground 10/10, mild port/polishing on the heads, 3 angle valve job, new valve guides, both heads planed, went with the entire Comp Cams k-kit (cam, lifters, valve seals, retainers, double roller timing chain, valve springs), Edelbrock Air gap intake. Did the lifter valley oil line mod, new oil pump gears (had a decent cover :)). Nothing fancy, mainly just stuff you are gonna do while you are in there.

I know you are only looking for 200 hp, but it is so easy to get 300 out of these motor without spending any extra money.

Hope some of this helps and doesn't make the decisions more difficult.

[82Waggy]

For instance the edelbrock performer cam that works so well in SBC applications only works well in the 304..why would that be?

Because both engines have about the same intake valve size to displacement ratio.

SBC 350 with 2.02 valve, 350cid/8cyl/2.02 = 21.65
AMC 304 with 1.787 valve, 304/8cyl/1.787 = 21.26

For comparison:

Ford 351C4V/8/2.190 = 20.03
AMC 360/8/2.025 = 22.22
AMC 401/8/2.025 = 24.75
BBC 502/8/2.4 = 26.15

Lower resulting number means a bigger valve to displacement.

As you can see from the above comparisons, a 502 cid BBC is way undervalved, even with a 2.4" intake valve, and therefore can benefit from a lot more intake/exhaust valve overlap - the result of a tighter LSA and/or more duration.

A 360 does not need the duration of the 401 to get the job done, nor does a 304 need that of 360, assuming you are trying to achieve peak torque values at about the same rpm.