mild 360 build opinions

[82Waggy]

82 Sorry I have been so brief on my replies...its been a hectic day. I guess knowing the vehicle that 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

I know I have had way too much free time on my hands lately - I hate winter.

It would seem that, in general, the results you post seem to coincide with what I just posted regarding valve size to displacement, but it is because of the wide variation in practical results that you and others whom I respect seem to have experienced that I have been trying to determine where the disparity is. Perhaps it has just been the various differences in combinations that have drastically effected the cams' expected performance - just a change from a single to a dual plane manifold on the same cam can really twist the expected results.

And I wholly appreciate the fact that many run of the mill grinds have no place in an AMC.

Regarding that Summit 8600, I wonder if it is really ground as specified. This is the one cam that, based upon users comments, seems to defy what I would have expected from it, which was to be a torque loser in a low compression motor at low rpm ranges.

Then there is donwags and crazy's 401 dyno sheets which are the only hard documented results I have had to use as a baseline for AMC cam comparisons, other than my past experience with other engine makes, both cams of which seem to perform in the rpm range you would expect of them. donwags XE256 certainly does not seem to be falling flat on its' face at 3400rpm, rather, the dyno sheet shows it to be strong out to 4800rpm and beyond.

So, I don't know what to say. For my own AMC projects I expect I'll have to try more than one cam before I am satisfied, and will base the first choice on the best evidence I have to support my theories. Seat of the pants from then on out once I have a baselin in my own build. I'll certainly post my results.

Anybody interested in following my 401 build? I am about ready to start and could post pictures. I'm even writing a manual of my build as I go.

[82Waggy]

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.

It has enough power to smoke a 37" Bogger on pavement.

If you don't mind responding, what axle gears are you running, and do you have 3spd, 4spd, or auto tranny?

[82Waggy]

Just for the hell of it I thought I would throw this out there for you all to consider.

These are the .050 duration specs for the three following cams.

Crwr276HDP, Comp XE256, Summit272 (8600)
Int = 212, 212, 214

Not much difference there eh, yet the .006 duration figures are way different.

[204wagoneer]

wow my little engine build started quite the thread, Thanks for all the good info.

I can see that 300 hp appears to be very attainable.

200 hp= good
300 hp= good-er

so long as I do not build the reliability out of the motor.

I think I will do the zero deck block and .045 head gaskets. Then only mill the head to make them good and flat.

What comp. ratio are the HD pistons sold here?? would I still be at 8.25 ish to 1?

I will be doing an free flow exhaust of some time since my rig is old enuf to get away from emissions.

well, keep the info coming, this is awesome for me as a new guy to AMC rebuilds.

Thanks again

[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.

It has enough power to smoke a 37" Bogger on pavement.

If you don't mind responding, what axle gears are you running, and do you have 3spd, 4spd, or auto tranny?

Do not mind at all, I love chatting about my Jeep!

Axle are D44 front, 9" rear mini spooled with 4.88's.
Auto Tranny TF727 (3 speed auto).
D300 t-case.

[82Waggy]

wow my little engine build started quite the thread, Thanks for all the good info.

I can see that 300 hp appears to be very attainable.

200 hp= good
300 hp= good-er

so long as I do not build the reliability out of the motor.

I think I will do the zero deck block and .045 head gaskets. Then only mill the head to make them good and flat.

What comp. ratio are the HD pistons sold here?? would I still be at 8.25 ish to 1?

I will be doing an free flow exhaust of some time since my rig is old enuf to get away from emissions.

well, keep the info coming, this is awesome for me as a new guy to AMC rebuilds.

Thanks again

Well, now we are getting somewhere.

Since new pistons are in order and you plan on opening up your exhaust, I would recommend bumping compression to 9:1, .045 quench, and would be more comfortable with a longer duration cam recommendation, BUT NOT TOO MUCH LONGER!!!!

[82Waggy]

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.

It has enough power to smoke a 37" Bogger on pavement.

If you don't mind responding, what axle gears are you running, and do you have 3spd, 4spd, or auto tranny?

Do not mind at all, I love chatting about my Jeep!

Axle are D44 front, 9" rear mini spooled with 4.88's.
Auto Tranny TF727 (3 speed auto).
D300 t-case.

Tall gears on those tires yielding higher rpm range with that cam makes sense. Your turning nearly 3000rpm in third at 60mph in a vehicle that is lighter than the subject Wagoneer of this thread turning 2.73 or 3.31 stock gears.

Big difference.

[204wagoneer]

ok, so going to 9.0 comp pistons is good, do I buy them or do I mill the heads to get 9.0?

[82Waggy]

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

Do you know what he .050 duration is for the stock cams?

The XE256 and Edelbrock performer cams both have an LSA of 110. Narrow LSA's tend to make the torque curve peakier, increase overlap, and decrease low end torque.

Longer LSA's tend to extend the torque curve out the rpm range and build better low end vacuum and torque. It is my "feeling" that an LSA of 112 or better is more suited to AMC engines. Perhaps it is the shorter LSA of 110 that is the reason for mixed results with the performer and XE256.

The LSA for a stock 401 cam is 116, for a stock 360 cam LSA is 113.

Here are the general effects of LSA on cam performance:

LSA Effects, Narrow, Wide
Intake Open, Earlier, Later
Intake Close, Earlier, Later
Exhaust Open, Later, Earlier
Exhaust Close, Later, Earlier
Overlap, More, Less
Cylinder Pressure, Gain, Lose
Idle Quality, Worse, Better
Idle Vacuum, Less, More
Torque Curve, Peakier, Flatter
Peak Torque, More, Less
High RPM, Drops Off ,Hangs On

The effects of longer LSA is why I generally recommend what may seem like relatively shorter duration cams - in order to close the intake valve sooner to help build/retain cylinder pressure and the longer LSA to extend the torque curve.

[82Waggy]

ok, so going to 9.0 comp pistons is good, do I buy them or do I mill the heads to get 9.0?

Check with Bulltear on a piston recommendation. Short of going with a custom forged piston, I think there are only two or three choices for off the shelf pistons that are all cast with the trough head design and I am not sure about compression ratios acheived with these.

Nothing wrong with cast pistons in general for your application.

One of the problems I see with a 360 is the rather large piston to deck clearance (.012 stock) and less than optimum stock piston head style that makes it difficult to acheive good quench.