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#1
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Camshaft selection for an LA.
I run a program called Engine Analyzer 3.0; and it's a pretty accurate program as far as giving power figures for various engine buildups.
Using this program, building a mild 318; here's the specs of it by the way: Stock Performer RPM heads #60779 Stock Performer intake 750cfm carb w/ vac seconds. 1-3/4" headers with decent dual 2.5" exhaust Now, for camshaft selection; the general consensus online is to go with something like 268-272 duration and .470-480 lift for my needs. In this program, a cam like that produces fairly nice results, around 290hp and 280tq. But if I use a Summit cam(#SUM-K6900) with 204/214 and .420/.442 with 112deg of lobe separation, I gain 25hp and 35ft-lbs while smoothening out my curves and having much better averages. Is there something I'm missing here, or is this program full of b.s., or am I just dumb? Any help would be very much appreciated. Thanks in advance. |
#2
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engine programs
Hi Angelis;
This question has so many unknown variables to be answered simply. These programs are based upon years of work and engineering data and are usually fairly close. The more data you have to put into them the better. I have no experience with E/A 3.0. I have desktop dyno myself ( a early version ) fairly simple stuff actually, but was fairly close to peak numbers, with that said. The RPM's at which these numbers occur would be helpful. The other thing were the cams specs all advertised or .050" lift numbers. The smaller cam could have larger numbers down low in RPM band, then taper off as rpm increased. Plus the 318 needs to spin harder to make hp and torque numbers as the cam lift and duration increase. That's why RPM figures would be helpful. |
#3
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Thats basically the same cam that was used in the earlyu 340s and they made good power. my 72 Duster with 340 has a 220 split duration cam and it idles smooth and kicks but through out the RPM range. The 292 duration in the 360 engine with eddy heads, RPM intake and Holley 750 is a dog out of the hole and turns on at about 2000 RPM. Its the combination not the individual numbers that makes a car perform.
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#4
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Here's the numbers for each.
First, the 318 with the online recommendations: And then the 318 with the Summit cam. |
#5
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Yeah, don't pick your cam specs solely from the program or just output #'s.
Overall use of the car, transmission type,and a BUNCH of other points will help to pick the right one. A rule of thumb taught to me was "Don't over-cam a street car." Assuming the car is a fun driver, not a pure strip ride. |
#6
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Sorry for the multiple posts, but
The T-curve looks suspicious in the 2nd diagram.
At 2000 rpm it shows ~240 lbs of torque with the engine cranking out ~80 hp? |
#7
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You've spent quite a bit of money so far. Why not spring for the custom ground racer brown Cam.
He's a Cam engineer, and a Mopar guy, so he will undoubtedly get you the best cam for what you're doing. Skip the guess work. Phone him up(Jim @ Racer Brown) Ask him how good the simulation is. |
#8
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ps.
There's lots of in fo here, but what are you planning on running for a torque converter? Big part to play, in whether an engine is over cammed or not. |
#9
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I haven't spent any money so far. I just bought the car for $100. '89 Fifth Ave.
I'm just looking around for possible combinations and what sort of results I could get with each. I dunno if I should stick with the 318 and give it a little more pep, build a nice 360 for it or even go up to an B/RB engine. Choices are pretty much endless. I don't want to spend more than $10k(US) total on the car, because in reality; it's really not worth it. I'd like some get up 'n go, enough to hang with a buddy's mild rocket 350 '72 Cutlass at least. But I really have no need for an 11 second street machine. |
#10
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I can answer this question and create a few more in the answer.
A wider centerline (Summit cam) will produce as seen, longer broader torque lines. The wider centerline can, but not allways , produce more max HP (Not in stone) later in the rpm band. The wider centerline also helps build more cylinder pressure. (Reduced overlap, less compresion needed) Now reverse it for the narrower centerline of the replacment 340 purple cam you inputed. The problem in the use of these cams on the computer is that the actual rise of the cam banks, ramp start and finish and where the peak lift is for each lobe is, is an unknown. The Summit cam is ground by Crane. (I twisted there arms to tell me.) There duration at .050 is weak incomparison to the purple cam. If you can afford to do a 360, do it. The extra torque and power will be very nice over a 318. It is basicly a bolt in deal. Theres no replacement for displacement! Skip the performer and go to the RPM with the RPM heads. 750 cfm and 1 3/4 headers. 9.5-1 - 10.0-1 with a cam to match the RPM cruise @ 60 w/ gears you want. |
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