shimniok
I have a pretty good challenge that I think most people seem to have no answer for... Maybe you can help? This is long.
I have an FSJ (86 GW). It weighs 5500#. It has a 3 speed auto with low stall converter. It has tall gears (33" tires, 3.73:1) and a 4" lift. I take it four wheeling. It has a 3" exhaust with Magnaflow muffler.
The 360 in it now was rebuilt about 10k miles ago. It has a Comp Cams 260H, AFB, Edelbrock dual-plane Performer, and 8.5:1. It STRUGGLES to get me up the rocky mountain passes west of Denver. The only way to get up most passes without my foot to the floor is to run 2nd at 55-60. I want more power. Do NOT tell me I haven't tuned it right after 2 years of trail and error-- and improvements-- unless you plan to drop by this Saturday and fix it for me. :D
I run 2000-2800 rpm in the 40-75 mph range. About 2600 @ 65. I have virtually no power in this rpm range as evidenced by lots of throttle to get up even slight hills and slowdown on big hills at altitude. The auto trans never lets the motor see more than 4000rpm by the way so the Chevy answer of building all the power from 3500-5500rpm isn't going to work. :D
I now have a 401 in the garage waiting to be built. Your challenge is-- can you build a motor that will solve my power woes -- without changing anything else about the vehicle? You are allowed to change exhaust. :) How would you build it?
What I really want to know is what kind of torque curve would you shoot for??? What power band would you select? Would you rather have more hp at 4000 or more torque at 2000? Or a balance?
Does any of this make sense? Am I insane? Wrong? Stupid? :D
Many thanks!!
Michael
jeepsr4ever
Welcome aboard Mike!!
First I would use a aluminum intake or possibly MPEFI (if in the budget) just cam/pistons/intake/carb alone would do the trick on a 401. I woudl warm it up a little with 9.6-1 speed pro's. Its a real basic build to get ample power for your rig out of a 401. Fuzz or tufcj will probly come around and go into more detial. Let meknow if I can help in any way
-MC
tufcj
Mountains suck.... The best way I've found to get up to the tunnel is "turbo diesel". My EFI 360 CJ struggles up too. I'm running 37" tires and 4.27 gears. I'm going to 4.88s as soon as I can get the jeep in the garage.
You really need more gear with 33" tires and that kind of weight. I'd say at least 4.11s, and maybe 4.56s. (I'll give you a great deal on my 4.27s if both of your axles are Dana 44s). The only way to keep up speed in the mountains is to have the engine spinning near the top of it's power band. You also have a problem with a carbed vehicle. Even if it's jetted properly for the 5000 ft. elevation of Denver, you need to go DOWN a jet size for every 2000 ft of elevation gain. At the tunnel, 11,000+ elevation, you're rich by at least 3 jet sizes, your engine just can't get enough oxygen to burn the fuel it's being fed. Without enough air, the timing needs to bump up too. Things you can't control automatically without a computer.
Where are you from. I'm in Aurora, CO.
Bob
tufcj
shimniok
Thanks for the responses so far! The advice is VERY valuable.
The reason I didn't want to change anything but motor is I just spent $1800 on rebuilt, locked and regeared axles. Now I'm married and spending $ is... limited. :)
I wanted to keep hwy rpms to stock level. A mistake? Maybe. But get this...
A friend has an 87 GW, 33" tires, 4" lift, roof rack, very similar to me, but runs 3.31 gears and a 401 with 10:1 CR and mild/stock cam plus a Quadrajet which he just got dialed in a few weeks ago. He is now running 3/4 throttle in 3rd up that first big hill on 285 to keep up with traffic running 60-65. He runs most passes in 3rd. I've personally seen this truck PULL AWAY RAPIDLY from me on hills where I am foot to the floor to hold 55-60 in 3rd with only modest accel in 2nd. On Monarch Pass I was in 2nd where I could accelerate ok but he STILL pulled away quickly (I think he was in 2nd too). I've also seen him accelerate from 65 to 100 on nearly flat ground where I could barely make it to 80 in the same timeframe. Frankly it is jaw-dropping to see.
So, that is what is possible. Btw, Spitfire built his motor.
I've been playing with Desktop Dyno a lot (just ordered the 2000 vers). I modeled my motor and his as best I could. What I've found is my Comp Cams 260H is a horrible choice with stock CR and exhaust, weak on torque in just the rpm band I most use. He has like 100 lbs-ft on me with his combo.
In a 401 with 9.5:1 CR, small tube headers, the Edelbrock Performer cam puts out 430+ lbs-ft in 2000-3500 range, and with 320 hp @ 4000 (best of 260-ish cams). Factory Pontiac grind specs I found on the web puts out 440+ lbs-ft from 2000-3000 (447 @ 2500, 'only' 435 @ 3500 and 408 @ 4000) with slightly less hp @ 4000 (311 vs. 320). No other cam comes close to these two in torque. The next best are down 10-20 lbs-ft 2000-3000.
Seems the Pontiac grind puts peak torque @ my cruise rpm, most torque in the power band, and peaks hp @ 4000 suggesting good off-idle torque. I doubt 9 hp matters since it'll be 30 more than I have now. I think it's the best choice I've got. That's what I am leaning towards.
But this is all cloud pushing based on a lot of assumptions, book learning, and junk. What are your thoughts?
Also, EFI is planned too.
Michael
cobra5laddict
your cherokee is not a red white and blue 2 door with 33's is it? i see that truck here local running around. i am in arvada and went to school in gunnison... i know that 285 drive all to well not to mention monarch. i had a 79 cj5 with a new stock 304 and a 3spd t-150 with 31's the gears were 3.54. throughout most of the large hills and monarch i had my foot burried into the floor board. i could never muster 50 mph in 3rd. 2nd sounded like i was winding it too tight. although i had a 2 bbl.. on the 360 i am building (different jeep) i am going to run tbi.. i bet that will make a bit of difference.
fuzz401
might want to go to 9:1 or 9.5:1 cr and might want to look at the comp 268 cam
shimniok
Mine's a white GW with woodgrain, 33's, roof rack. I live in Centennial.
http://www.cfsja.org/rigs/michaels/tc/index.html
Thanks for additional replies!
What D.D. sez is higher CR (9 or 9.5) and small tube headers is the only way to make good power at low r's with stockish cam.
Pontiac specs looks best to me so far; ideal match to my rpm...
I am going to call a couple cam shops and engine builders for advice too.
Desktop Dyno 2000 is on the way to help too.
Michael
jeepsr4ever
That really looks like a jeep I saw in FSJ magazine
cobra5laddict
SHIMINOK,
what are you going to do with the 360 in your rig if you go to 401? i might be interested if you would like to sell.
[email]Byron@waringoffice.com[/email] :lo1l:
Goose
I am originally from Central City Co (moved here 5 years ago) and I have 5800# J-10 with a 360 I ran around up there all the time, While I wont say I had "ample" power at the tunnel I could easily have run 80 or better climbing either side.. I would suspect there is something out of whack in your set up, unless that cam is really hurting you. My 360 was essientially stock with a Edelbrock torker and 1406 carb with a mallory hyfire ignition box and headers. Bob is right in that at the tunnel it's gonna be a dog to a certain extent but it should still run pretty fair unless it's tired. So I guess this is a long way to say.. If I were doing it I would build the bottom end essentially stock, Maybe bump the C/R If you can swing the dough. But the money I would spend would be on the cam/headers and Fuel injection, With the best ignition system you can afford. I have always believed the ignition system is one of the best places to improve performance, since most other mods are aimed at getting more fuel/air into the engine..It seems the greatest gains would be made by making sure you can burn all you do get in there.
(Jeez I'm getting to be a wordy bugger)
shimniok
On the 360, planning to get a cheap FSJ without motor and swap in and sell the whole shebang to try and recoup cost.
I think the cam is hurting me. I am usu foot planted to hold 50-55 up to the tunnel. Motor is new. I've played with mix/timing for some time and improved power, but not lots. Ignition is already about as hot as it gets.
May install O2 sensor and tune carb more. Headers too. And may even try another cam. Hate to build a 401 without knowing what went wrong with the 360.
Higher CR is a must have as far as I can discern.
On the 80mph J-truck, what gearing, tire size, and cam? Thx.
Michael
shimniok
PS: Rig's barely visible on p15, Feb 03. Don't think there are other pics of it in its present state? My old 85 made cover in 01. Hoping to make Spring with an article about the St. Elmo area so rig may show up there. We'll see... :mrgreen:
Michael
Goose
Well on the J-10 the tire size was 33's the gears are 3:73 (I'm pretty sure)
and the cam was the edelbrock performer cam.. There is kind of a mismatch on the cam and intake as the intake is a torker (2500-7000) and the cam is off idle to 5500 if I remember right. but I think I would look into your setup something has to be out of line to be as doggy that.
I would really wonder about the cam. It seems if youre making power above say 2500 this is about where youre holding the grade, Kicked down climbing like that if it's holding 50-55 and if it shifts it doesn't have the torque to mantain it without kicking down and bringing the RPM back up into the power band,
Mine (since it is a 4 speed) would continue to pull in 4th if you let it until it got ahead of the cooling system at low rpm and start to get hot, then down into third and cooled right down. that stretch from georgetown to silverplume is the toughest pull on the hill.
If I remember right I was turning about 2700 at 70 mph
The one caution I have to add in here is Fuel mileage from Denver to silverthorne was about 4 mpg. 16-17 under normal conditions
shimniok
Thx. Sounds like our gearing is identical. I get 8-10 mpg depending on number of hills, hwy vs city etc.
Here's graphs of D.D. tq/hp for Edel Perf, CC260H and Pontiac 9779066.
But sure, maybe it isn't tuned right, still. Would a degree of timing or being 1 stage lean or rich completely throw performance out the window?
...what is a sure fire way to set timing perfectly?
...what is a sure fire approach for dialing in carb?
...anything else I can do?
...how do I verify my 7 year hi flow old cat.conv. is not plugged?
...what else could rob lots of power?
Apologies if this is OT.
Michael
Goose
Well as for dialing in the timing, I use the "ping method"..Unscientific and If you don't pay attention and let it detonate a long time your going to break something but it goes like this. Set your timing about 5 -7 degrees advance from stock for altitude then go try it.. Keep advancing it till you start to ping at mid Low rpm full throttle acceleration. then back it off a little. as for the carb I dont have a good way, I usually judge by performance and driveability, you would have to be fairly rich to dump performance to the level you are seeing. If you were a little lean it would run better the higher you go. But you might save yourself some grief and pull that cat and put a "Test pipe" in it and see . even a partially plugged converter will degrade performance a lot. or you could find a station that has a old tail pipe sniffer exhaust analyzer (like they used to use for em tests before envirotest.)
Don't lose hope if that 360 is fresh it should drag that wag around in style.
What Carb are you running?
shimniok
thanx for the tips.
Running an old AFB. REALLY sick of the choke on it, can't get it dialed in. It does pull off fully, just too quickly (no heat riser). Maybe time for the EFI after all... (GM TBI) ... or a Qjet...
Will check out the exhaust issue, who knows...
Michael
shimniok
In case anyone's curious, I swapped on a Qjet, did some quick calibration, passed emissions, and improved performance (below 50mph). It drives like it has EFI at least below 50 and gas mileage went up quite a bit. It still is lacking on the highway. I haven't checked for the plugged cat yet.
Michael
MrFurious
Don't put a whole lot of faith in the DeskTop Dyno software, as it isn't very accurate in terms of real world numbers. When I worked down at Jeg's in the Tech Support Center, we actually plugged several crate engines into the software and none of them were even close on the HP and torque figures we got off the engine dyno. Typically, DD would show 50-75 more horsepower than was actually pulled off the dyno.
However, the power curves were usually pretty close in regards to peek power at such and such rpm, so using it to build an engine up for power in a specific range is possible. Just don't rely on the power numbers it gives you unless you want to be disappointed.
shimniok
Thanks for the info, that is good to know.
I noticed DD2k is significantly more optimistic than the original DOS-based version was (which claimed 95% accuracy and was closer to the original creator's vision I suspect).
I will keep that in mind and use it (and talk to some engine builders) to figure out what the best -curve- is for the setup I'm running. That's really the biggest question I've had all along, anyway.
Michael
shimniok
Thought I'd post again. I haven't done squat with the 401 yet. I am probably a jet size or two rich on the Qjet. I do have an EFI setup in the garage but that is a lot of wires to add and I'd hate to break down on the trail. That's why I never put it in. One of the guys on the CFSJA list runs an MPFI Edelbrock on his 360 and reports 90+ at the tunnel, but he also runs real low gears and stock tires and lift (so he must be spinning 4000 at hwy speeds?)
All the desktop dyno stuff I've played with says I can get 20hp and 70+ ft-lbs across the ENTIRE 2000-4000 range with a 401 and either an edelbrock performer or a custom grind like the Pontiac *066 (the latter is for big heavy Pontiacs with autos, the former is for small motors so puts the power lower in the bigger motor I guess). I haven't looked at all the possible cam grinds or called anyone yet. Have done a few searches here for cam advice.
I finally put together some money for the 401 so we'll see what work needs done to it and go from there. I'm also contemplating simply putting in a new bumpstick in the 360 along with headers. I hate seeing a $2800 motor go to waste or blowing a lot of money on the 401; I'm banking on it not needing any major machine work. Aside from lack of power the 360 runs fine.
If I do the 401 I am taking the advice here to heart: 9.0:1 or 9.5:1 CR pistons (or do I need to deck the block to improve squench?) headers if I can possibly afford it, and will keep the Edelbrock intake and Qjet carb, then do some kind of cam grind with 114* LCA and duration to support peak torque around 2800-3000, peak hp around 4000-4200.
Also to doublecheck I plan to take it to a muffler shop to see if the catalytic converter is bad after 8 yrs. (How else would I diagnose this?)
Michael
