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| Thinking about installing a smaller cam in Eileen https://slantsix.org/forum/viewtopic.php?t=33273 |
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| Author: | Bren67Cuda904 [ Sun Jan 11, 2009 6:22 pm ] |
| Post subject: | Thinking about installing a smaller cam in Eileen |
The main reason is to cut down on the idle and low RPM raw gas smell and help fuel mileage a bit. I've tuned the carb and the engine just doesn't like to idle unless its running 12:1. I've also read that high overlap cams will produce this problem. The car is mostly a grocery getter and transportation for haul en my son around as it the only car I have that I can put a car seat in. It spends very little time at the track. My feeling is that this motor might be quicker with a less duration cam anyway due to the extra long stroke that Eileen has. The head could have had a better port job too. I had pinging problems early on running a 10.4:1 CR but since we reduce the ratio to 9.25, the pinging is gone. Another thing I have done is restrict the exhaust quite a bit. I changed out the tail pipe and installed a 16"x5" muffler next to the tank. That makes for Clifford 6-2 headers, 2"-3"-Y to 3" dump to a 2-1/2" MagnaFlow to 2" tail pipe and the generic 16"x5" muffler and a resonator tip. The car was simple to loud with out the extra muffler. The sound is good now but it has killed the performance quite a bit. For reference the car with the dump open with street tires it would burn the tires part way into 2nd gear. Dump closed and NO 2nd muffler, burn 20' and with second muffler added there is no chance of turning a tire. Not real fun, but the headaches are gone. All this leads to this. I have also heard that large duration cams are louder and harder to quiet down. I am hoping that a cam can be chosen that will let me remove the second muffler and not be to loud, not loose a lot of time at the track and get rid of alot of the raw gas smell at light cruise and idle. See the sig line for most of the current engine details. Anyone have a cam that they can suggest that might provide the results I looking for? Also I'd really hate to change out the converter. Cam is a .518/.518 240@50 110 |
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| Author: | terrylittlejohn [ Sun Jan 11, 2009 6:27 pm ] |
| Post subject: | |
what do you have the cam center set at now?mybe just setting it at 102/ 104 might be worth a try. |
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| Author: | Bren67Cuda904 [ Sun Jan 11, 2009 6:50 pm ] |
| Post subject: | |
I am 2* advanced now. Just for clearification, are you suggesting retarding the cam to 8-6*? |
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| Author: | Joshie225 [ Sun Jan 11, 2009 7:50 pm ] |
| Post subject: | |
A cam with a 110° LDA is often ground 4° advanced so that the intake centerline is 106° ATDC. Terry is suggesting advancing the cam so that the intake centerline is 102-104° ATDC. |
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| Author: | Dart270 [ Sun Jan 11, 2009 8:13 pm ] |
| Post subject: | |
I would go to 102 deg. Most of the fast guys have ended up at 100-104 deg and so have I after playing around (100 will be best for the Dart). 106 is definitely too far retarded. You could go to a 230 @ 0.050" cam and be quite happy, but a cam timing change might be in order first. I don't exactly see where you're at now. Did you degree it? Lou |
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| Author: | 68barracuda [ Sun Jan 11, 2009 11:46 pm ] |
| Post subject: | |
What CR are you running? |
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| Author: | Bren67Cuda904 [ Mon Jan 12, 2009 6:28 am ] |
| Post subject: | |
http://www.renaissanceracing.com/images/CamCard2A.JPG I am 2* advanced from this card which puts me @ 16* |
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| Author: | Charrlie_S [ Mon Jan 12, 2009 8:33 am ] |
| Post subject: | |
Quote: http://www.renaissanceracing.com/images/CamCard2A.JPG
I make that to be 106 by the card, so that would be 104 actual.
I am 2* advanced from this card which puts me @ 16* |
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| Author: | Dart270 [ Mon Jan 12, 2009 11:29 am ] |
| Post subject: | |
OK, you may not pick up much, then. Still, might be worth a try at 100 deg. Lou |
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| Author: | 440_Magnum [ Mon Jan 12, 2009 12:17 pm ] |
| Post subject: | |
If I recall correctly, this is a mechanical cam motor. If it were a hydro motor, you could use the other "cheat" to calm down a radical cam: variable-duration lifters (eg. Rhodes). In fact if I remember right, your combo is almost a textbook case of where Rhodes lifters would work well: compression low enough to tolerate short duration, but still has lots of high-end breathing available. As others have suggested, you might try advancing the cam a few more degrees, but with such a big cam I'm afraid all that will do is open the exhaust valve too soon and dump a lot of power down the tailpipe without really helping the idle that much. General rule: the "bigger" the cam, the narrower the range over which you can tune it by degreeing. |
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| Author: | Doc [ Mon Jan 12, 2009 1:40 pm ] |
| Post subject: | |
One other "cheat" is to loosen the valve lash as much as possible... find the point where it runs-out of lash ramp. Where is the lash clearance currently set? DD |
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| Author: | Dart270 [ Mon Jan 12, 2009 2:41 pm ] |
| Post subject: | |
That's a good point, Doc. In fact, if Bren is using the stated lash, it may not be enough for smooth running. Sometimes, you need to play with lash some to find best operation point. 240 @ 0.050" is not that big for a 225, especially with 110 LSA, although 9.25:1 is a bit low for that cam. How did you like Howard's cams for service and was this a regrind? Lou |
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| Author: | Bren67Cuda904 [ Mon Jan 12, 2009 4:48 pm ] |
| Post subject: | |
I have no complaints about the idle quality in terms of smoothness. In fact its very smooth in my opinion. Its the raw gas smell thats got to go. I can whip into my driveway and turn the key off almost before I am stopped get out and the smell of gas makes you wonder what the cars behind or people on the sidewalk are thinking about you and your smelly car. Valve lash WAS set at .016 for both and the valves where very quiet. I've noticed that they NOW are not as quiet as they where, which leads me to think that they are in the .020-.022 range, but have not pulled the cover to check. I am running 87 octane at 25* total and no pinging at all. I have a switch that lets me add 4* more with a flip and there is still no pinging with 87 octane. Many may remember that I was having pinging problem very early on and pull out some compression. This let me run 93 octane but not 87. Its only when I installed the Clifford headers and removed the Dutra front and cut rear manifolds that the pinging went away. One other note: Cranking PSI before compression was removed and set 6*(20) advanced was 235psi and 220 psi at 1*(15) advanced. Lower CR and now have to this day 200psi at 2*(16) advance. The cranking pressure didn't change between manifolds or headers. I suspect that I could have left the CR alone at 10.4, and installed the headers then and ran 93 octane without pinging problems. A boost in fuel mileage would be nice. I remembered getting 19 MPG some time ago but I must have been mistaken. I've rechecked it and I am getting 10 MPG city and 13.5 MPG HYW. Wide band on the open road running about 75-80 (with OD 3000rpm) is reading around 15.6 with a hint of a lean surge. One jet up (fatter) in the primary covers the lean surge and wide band reads around 14.6 ish I blows my mind how I can be getting 13 MPG and running 15.6 on the wide band. |
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| Author: | bigslant6fan [ Mon Jan 12, 2009 5:39 pm ] |
| Post subject: | small cam? |
It sounds like the cheap muffler has to go.If you lost that much performance,it must be VERY restrictive,costing you fuel economy as well.I,d suggest a Walker super turbo,I think it,s a good compromise between performance and noise |
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| Author: | 440_Magnum [ Tue Jan 13, 2009 11:10 am ] |
| Post subject: | |
Quote: I have no complaints about the idle quality in terms of smoothness. In fact its very smooth in my opinion. Its the raw gas smell thats got to go. I can whip into my driveway and turn the key off almost before I am stopped get out and the smell of gas makes you wonder what the cars behind or people on the sidewalk are thinking about you and your smelly car.
RAW gas smell? That's not likely to be the cam. That could be fuel vapor from the gas tank itself, or fuel vapor escaping from the carb. These older cars had very minimal fuel vapor control systems, and if you've got a leak in the system somewhere that would make it far worse. Modern fuel (especially "winter blend" crap with a high vapor pressure) makes it worse. Routing the exhaust pipe too close to the gas tank, resulting in the fuel being a few degrees warmer than it has to be, will make it worse. Heat soak causing the fuel in the float bowl to boil after shutdown will make it worse.Part of it is just the price you pay for a cool old car, but being anal about keeping your fuel cool will cut it WAY back. Quote: I blows my mind how I can be getting 13 MPG and running 15.6 on the wide band.
That is pretty spectacularly bad- I get about the same in my 440-powered C-body. Could you be losing fuel somewhere? Leaky fuel line, leaky filler-neck seal so that you're losing a bit out of the tank by "slosh"? That could explain the smell AND the low mileage.
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