Too Hot of CAM?

The PIG Smith

I am planning soon to install a Summit 8601 Cam and lifters in the 360 in my '81 J20 tow rig. Here are the specs of the SUM-8601 cam I have: Cam Style: Hydraulic flat tappet Basic Operating RPM Range: 2,000-5,000 RPM Intake Duration at 050 inch Lift: 224 Exhaust Duration at 050 inch Lift: 234 Duration at 050 inch Lift: 224 int./234 exh. Advertised Intake Duration: 282 Advertised Exhaust Duration: 292 Advertised Duration: 282 int./292 exh. Intake Valve Lift with Factory Rocker Arm Ratio: 0.496 in. Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.521 in. Valve Lift with Factory Rocker Arm Ratio: 0.496 int./0.521 exh. lift Lobe Separation (degrees): 114 Intake Valve Lash: 0.000 in. Exhaust Valve Lash: 0.000 in. I got this cam as a bargain. I wanted a cam that was little less radical, but I was assured that if I recurve my dizzy for an initial 14 degrees, I should be fine. I currently have a Edelbrock Performer 2131 intake, with the EGR blocked off and a Edelbrock Performer carb that needs rebuilt or replaced. I have a single 2.5" exhaust that dumps right in front of the rear axle via a Flowmaster Series 40 muffler. My 360 retains its stock Motorcrap ignition. I have the parts for a TFI, but I desire a GM HEI. My J20 is a dedicated tow rig that will see mostly the highway. Before I start tearing my 360 apart, any comments or concerns about using this 8601 cam in my J20?

82Waggy

Assuming you have stock heads with that exhaust system, you probably won't be happy with that cam - too much duration and unecessary lift for a tow motor. Too much intake dilution for good torque at lower to mid rpms with that exhaust. For towing and/or a wide torque range, look for something with about 30 degrees of overlap, at least 112lsa, and less than 260 adv duration . Not much need to exceed .450 lift with stock heads.

The PIG Smith

82Waggy wrote
Assuming you have stock heads with that exhaust system, you probably won't be happy with that cam

Well, as I mentioned, this cam, lifters and timing chain set, NIB was a excellent deal.
I was hoping I could make it work for my rig.
Short of throwing this cam in the trash and buying a 8600, what could I do to make this work?
Would a port and polish the stock heads with headers?
Both were things I considered of doing.

Other than a Summit 8600 or a ComCam's 260H, what cam would you suggest?
Cam selection has been a royal pain. ](*,)

zero cool

A friend of mine has the Summit 8601/Edelbrock 2131/600 CFM carb in his Wagoneer. He's running stock exhaust. The engine runs great from idle all the way to redline. I have the 8601 in the 360 I'm swapping into my Cherokee. I also put it in the 401 that's going into my CJ. I've just gotten the 401 to run a little with GM TBI only to find out that the freeze plugs leak. It was way out of tune so I don't know how well it runs with that 8601 yet. I'll know more over the next couple of weeks. I'll be firing up that 360 in the Cherokee over this weekend or next and it's using a full GM TBI from a 350 so it should run a lot better than the mix/match job I did with 350/454 parts on the 401. At least as far as initial tune goes.

jeepsr4ever

That camshaft is horrible for low end grunt. Speaking from first hand experience your alot better off with a 8600

82Waggy

Are you running stock compression ratio and stock heads? If so, neither of the Summit cams would be your best choice. You need something that will help build cylinder pressure (earlier intake closing point helps build cylinder pressure=generally short duration). With the valve size to displacement ratio of the 360 (similar to an SBC) you do not need a lot of duration to get the job done. You are also talking about a relatively heavy vehicle pulling a load - long duration/valve overlap is bad for this and will likely fall flat on its' face. All the timing in the world won't help it do anything but ping. Not saying it won't run, but seems everybody overcams their Jeeps as though they have a big block chevy (small valve to displacement ratio).

82Waggy

Check out Crower's 246HDP at www.crower.com

This, or something similar, is what I would put in a stock 360 with headers. Should help snatch your trailer, and snap your neck.

Goose

what is that I hear?? Too much cam in Jeeps.. Sacrilage! blasphemy!.. but it's true..

The PIG Smith

82Waggy wrote
Check out Crower's 246HDP at www.crower.com

This, or something similar, is what I would put in a stock 360 with headers. Should help snatch your trailer, and snap your neck.

Thanx for advice.
I am happy that I've asked before turning wrenches.

The PIG Smith

Would my Summit Lifters work with a Crower Cam? I am sure they would, but just confirming the obvious. Also, what are your comments about having Crower grind a roller cam to the specs of their Hydraulic 246HDP. Yes, I know my Summit hydraulic lifters would not work and I would need to get roller lifters. Would I need to machine my block for such a setup? I know nothing about a roller valve train. I was thinking a roller cam and roller tipped 1:6 rockers while may not increase HP by that much may increase the efficiency. Doesn't a more efficient engine run cooler, use less fuel, last longer?

82Waggy

Roller cams don't really provide much advantage until you start getting into much larger duration and lift profiles. Up to about 270 duration, a flat tappet can still accelerate a valve of the seat faster. With todays oils, not much of a friction reduction advantage with rollers either. Spend your money on roller rockers. Here's another cam to consider for your application: Engle 35018H. Your lifters would work with any hydraulic flat tappet cam.

The PIG Smith

zero cool wrote
A friend of mine has the Summit 8601/Edelbrock 2131/600 CFM carb in his Wagoneer. He's running stock exhaust. The engine runs great from idle all the way to redline.

I am sure that your friends 360 with the Summit 8601 cam does run fine.

What I had suspected when I bought my 8601, that it was too hot for a Tow Rig.
I was then reassured the recurving of my distributor would compensate for the more radical profile.
I learned here than my initial gut feelings were correct, that this cam is not well suited for a tow rig.

My 7600# rated J20 will be used to tow a tandem axle trailer across country to haul home those projects that are cherry and/or free/cheap.
I need a cam in my J20 that will pull a heavy trailer up a mountain pass while passing the ricers over in the slow lane with the big rigs! HAHAHAHAHA
(I am being silly, I need a diesel tow rig to work this hard)
A Summit 8601 cam will not perform in this type of service.

Goose

naahh, you don't need a diesel, that 360 built with moderation in mind will do the job just fine.. I have a J-10 with a 360 T-176 4 spd and 3:73 rears on 33" tires the 360 is basically a stock bottom end with the torker manifold edelbrock carb headers and the cam is an old schneider grind that I will try to find the specs on.. this truck empty will get 18-19 mpg at 65 mph on the highway and will climb I-70 all the way from Denver to the Eisenhower tunnel at 65 in top gear..and If you dont mind listening to it howl along at 5500 rpm it will drag the CJ-5 and my "stuff" up there in third all day long. If you have never seen I-70 west out of Denver.. it goes from 5000' to 10,000 at the tunnel in something like 21 miles..with 8% grades in places.. ok now that I have bragged on it it will blow up..

Dusty

have run the 8601 which is the profile you listed in a couple of stock compression 401's and had no problems towing actually towed really well, woke the motor up more so than most of the so called rv and towing cams out there. i also ran a 270H comp cam in my 360 powered rig with a 670 and that towed really well too, and in a 9.2:1 360 with a performer and the PAW version of that cam i had it in a 74 waggy with t-18 and liked it plently of snort in the 1500-5500rpm range, a little soft off from 1000-2000 but i was never in the 4 barrels at those rpms anyways so the gearing in the truck took care of the soft starts, soft start was just a slight tap of throttle as i was letting clutch out vs some of the other options where i could just let the clutch out and didnt really have to worry about keeping throttle up. I liked being able to down shift on a grade and pull 4000 rpm+ and still having power with a load and then being able to shift back into direct and keep chugging down the highway. most of my rigs have always cruised the highway with a trailer at 2500-3000 rpm at 65-70 mph+ and since that is my cruising rpm i have always liked the rpm buffer of still having 2k ov er that and still having power 1000 rpm under that. That said i cannot help you with a rockers and bridges motor, all of my 360's, 390's and 401's that i have built if they are rockers and bridges i havent gone over 480 lift but with the stud motors all of my amcs that i have towed with and built have loved bigger cams for towing ect. 401's and 360s alike always get undercammd. also dont forget that nis a 114 lope sep cam its alot more behaved than you might think.

The PIG Smith

Goose, I whole hearty agree!
Not wanting turn this into a FSJ bragging post, but I would also like to share about how great of a J20 that I own.

Last fall, I towed an empty tandem axle full till bed trailer to from Fort Wayne, to 50 miles north of Pittsburgh, PA.
This trailer empty weighs close to 3000#

I then loaded up a 1980 Chevy Hefty Half Diesel pickup hauled it to 25 miles SW of Charleston, WV.
My brother's project was somewhat stripped down, but still weighed ₃₀₀₀#.
I am guessing the towed weight to be between 5500 and 6500#
With the trailer and all that weight, the ride height of my J20 did not change, the rear end did not squat.
I love the stiff rear leaf springs

The entire trip was right down I-79.
Much of I-79 is up and down hills, some long and steep.

Between Pittsburgh and Washington, PA, I was climbing a long steep hill and was gaining speed.
I had my brother lean over and be a witness, as I was over the 65mph limit.
I backed out to maintain the speed limit, as I wanted to take it nice and easy.

My J20 performed excellent!
I managed to get 10mpg towing up and down all those hills.

One thing I was happy about, was I did not have an OD tranny.
My TF727 is awesome for towing!
On lots of hills, my 360 lugged down some, but the 727 never shifted from third and I was always able to maintain the speed limit.
I love the combo of my J20's 360 V8, TF727, NP219 transfercase, Dana60 and Dana44HD with its 3:73 gears.

The next morning, I was took some crappy pics with my cell phone.

The reason for my current cam change project is I have an intake lifter on the one cylinder that has a bad tick.
I dunno if the lifter is bad or the cam lobe is going flat.
I feel that a new cam, lifters and a timing chain set will continue to make my J20 the awesome tow that it is
and generate more great stories and experiences!

82Waggy

I guess a few points need to be made. Duration alone simply shifts the point along the RPM range at which peak torque is produced (approximately 500RPM higher for each ten degree increase in duration) - assuming all other aspects of the engine remain the same. Having said that, a cam with high duration and resulting late intake closing point can, and usually does, result in a drop in cylinder pressure and therefore usually a loss in power across the board. This is why you see cam recommendations suggest an increase in compression with longer duration cams - in order to maintain or increase cylinder pressure. The other side effect of long duration is a general narrowing of the torque curve which usually results in a loss of bottom end power - this can be countered somewhat by increasing the LSA. Most people choose cams based upon duration and lift. What they should base a cam decision on is overlap and LSA. LSA should be chosen relative to valve size to displacement ratio and whether peak torque or wide torque curve is desired. Overlap should be chosen on loading application, single or dual plane manifold use, and exhaust restriction characteristics. Intake valve closing point should be based upon its effect on dynamic compression ratio. Lift should be chosen based upon the flow characteristics of your heads. Duration then falls into place as a function of overlap and valve timing requirments. For your stock compression and heads to be used for towing, keep overlap in the 30 -35degree range. Look for an LSA of 112. Keep duration short to help build cylinder pressure. Fast ramp rate is always good. No need to get crazy on lift. OR you could do what everyone else does and be content running neck and neck with them :-|

82Waggy

Goose wrote
I have a J-10 with a 360 T-176 4 spd and 3:73 rears on 33" tires the 360 is basically a stock bottom end with the torker manifold edelbrock carb headers and the cam is an old schneider grind that I will try to find the specs on..

:shock:

Hey Goose, you should try a dual plane intake manifold and see what happens.

Just a suggestion :roll:

JERSEYJOE

What about a Crane 278 H for the same application?

82Waggy

JERSEYJOE wrote
What about a Crane 278 H for the same application?

You would need to increase compression quite a bit to gain back the low speed torque this cam would lose in a stock motor. Peak torque would likely be low relative to what a shorter duration cam could produce in a stock engine, and not reach peak torque until fairly high up the rpm range even with higher compression.

KJMac

The 246hdp is a stock spec cam (replacement) so I would do the 260 or 270hdp cam. 260 comp is good as well. The crane 278 would suck. The crane pm H-290 or 266 would work good! Don't look at the advertised duration, look at the .050 duration.