I was thinking about putting an RV cam in my 390 as it is mainly used for low rpm uses such as pulling large trailers and doing farm work.
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Steve, take a quick look up at my 390/410 cam choice thread. Basically looking for the same kinda deal in the motor I'm building. For hauling, you want the low end torque, and a nice flat torque curve. Think I'm pretty well settled on getting the Crane 343901. It has a pretty flat torque curve from 2-3500rpm and produces a little more low end torque than the others I was looking at.
I think Ratsmoker or Karl could run you some desktop dyno numbers if you had a cam or two you were thinking of. They'll need some information for that. Intake type, carb, head info (if they're cj-style, have they been ported and polished), things along these lines.
I took the opportunity to run the Crane cams 343901 against my Isky 256/262 cam in Desktop Dyno. Here are the results.
Crane Cams 343901
While I cannot attach the graph from these, The Isky had the flatter torque curve, But on the downside it was 10 HP shy at 5000. But then again when do you tow at 5000rpm.
When I was looking for a cam for my 390 tow vehicle I spent a long time comparing before I bought the Isky. I was looking for a cam that would deliver max torque about 500rpm higher than my cruising speed.
I'm thinking of retuning my 390 for more of a torque machine. Do you guys think I can make the Edel 750 Carb work well with such a cam? I assume that my RPM intake is still a good choice, no? What about the factory heads and the free flowing exhaust. Are these good for building a torque monster?
Any ideas appreciated. I may want a monster boat when the wife finishes Law School :-) And I'll need my 69 F250 to pull it.
Yes, the same came that would excel in a stock 390 would be good in a 360 too. As far as the other question about turning your 390 into more of a torque machine, yes, the RPM intake is still a great choice. Personally, I think the 750 would still work with that cam, provided that you jet down. Granted, it is a bit large for your stock heads but smaller jets will offset that. Your factory heads and headers are good for torque, these FEs were never shy about pulling stumps. I don't know your budget, but I'd be tempted to do some work on your heads and drop in the CJ valves. The Eboks are nice but the stockers can be made pretty hot too with a little massaging. Just out of curiousity, what cam do you have in there now that you want to swap out? Last question, what pistons are you running?
[updated:LAST EDITED ON 17-Jun-02 AT 06:12 PM (EST)]I'm running the crower Power Beats cam, I don't think it's a torque maker by any stretch of the imagination. I figured it to work well with the 750 carb, and the Edel heads that I originally purchased, but returned in frustraion due to heli-coils coming loose. I thought big-heads, big carb and big cams would produce high RPM HP and sacrifice low end grunt. Mine seems short of low end power at this point, but I may have some tuning to do. I originally thought that with a 390, C6 and 4.10 gears I could tune for high RPM HP and still have enough low end to be a truck.
So you think that some head work is still in order to produce good torque?
FORD 332 352 360 390 406 410 427 428 V8 1963-up
HYDRAULIC CAMSHAFTSPower Beast/Performance Level 3 - Delivers impressive mid-range and top end power. Healthy sound. Economical price. RPM Power Range: 1200 to 3800/Redline: 5200 plus
CID GROUP :390/428
Grind Lobe Center :292H/112D
Advertised Duration (Intake): 292, (Exhaust) : 302
Duration @ 0.50 in. (Intake) : 214, (Exhaust) :224
Gross Lift(1.76/1.76) (Intake): .521", (Exhaust): .547"
Hmmmm, that cam doesn't look like it should really hurt your low end too much. I'm not sure you would see a big difference in plopping in another bumpstick, as that Beast already looks like a good compromise to me. Well, massaging your heads is always a good thing but I think for simple low end oomph you might want to spend your money elsewhere. Do you know what your compression is at? Some of the stock pistons were set up for pretty low compression, particularly the truck ones. Something to look into...if you do have low compression pistons than swapping them out for a set to bring you up to @ 9:5:1 would give you a heck of allot more thrust throughout the rpm band. I think the first thing I would do if I were you were to put a smaller carb on there. I know the 750 could be made to work on your engine but its really not optimal, especially for the lower end. You might be surprised at the differnce just going down a size in carb can make. Your intake and ignition are right, so I think I would look at the carb first first. Lastly, what tire size are you running with the 4:11s? Anything larger that 35's with those gears would cost you low end.
I dunno. That looks like an awfully big cam to me. 292 and 302 degrees advertised duration? The 112 LSA isn't too bad, but combined with the long duration it results in a fair amount of overlap and would be expected to bleed off cylinder pressure. Lower cylinder pressure, of course, means less torque. That's why short duration cams generate better torque and low end than long duration cams.
If you are running flattop pistons, and have a static CR of 9.5:1 of higher, that cam MIGHT work. Still, I think it is better suited to a 10.5:1 or higher CR. If you aren't having any detonation issues on pump gas with that cam, I'd recommend switching to a shorter duration cam to increase cylinder pressures and torque.
I also agree with the recommendation to go with a smaller carb, but I'd switch the cam first and see how it works.
Well, I can't argue that the cam is a little on the large size for what he's wanting, I'm just not sure dropping in a 34901 Crane would improve things all that much. I mean, if time and money isn't an issue it would help, but I'm still wondering what pistons he's running with. If they are the stock low compression, I still think that would be the first thing to swap out. Of course, now that I'm reading back this post, if your going to crack into your engine to drop in new cans it would be silly not to pop in a smaller cam while the block was opened up. I simply don't think just going from that Crower Beast to the '901 will give him the improvements he wants in and off itself.
A cam with small durations @.050 and large durations advertised mean one thing and that is slow opening speed. If your valve is opening slow that means cylinder pressure is bleeding off and air isn't coming in as fast as it could for the first .050 of the rotaion. In other words why have the valve open if it can't breath. The cam is a bad design in my opinion. I do think the 901 would definitely improve low end torque. I hope you can understand what I am saying becasue reading over this it isn't worded as good as it could be.
Referring to Ratsmokers post he is talking about lobe velocity. Basically the faster the opening the better the cylinder will fill. The faster opening valve will also place more stress on your valve train componets. Unless of course you are using a roller cam.
Use this calculation to figure the velocity of the valve opening speed. "Duration@.000 lift - Duration@.050 lift=Lobe Velocity"
You can use this to compare cams that are close in specs and see what one would give you better performance.
Hmmmm, I didn't really take that into consideration. Its funny, but cam choice should be a simple thing but its seems one part black magic and one part science. In any case, as I respect the wisdom of the other guys who chimed in maybe just switching over to the 901 will make more of a difference than I thought. They still don't seem THAT different to me but then, I realize how critical cam choice is. I'd never heard guys who had run the crower beast series complain about torque before, but then, I'm always learning...
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