Thread: 1937 Plymouth 5 Window Coupe

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I have been watching this thread, and I have a question. I am not trying to start an argument with you, techinspector1, as you have considerably more experience than I have. But I don't quite understand your recommended cruise rpm for a cam with 230 degrees @ .050 duration. Perhaps you can explain that to me because I have achieved different result. My 383 has a 230 cam [CompCams 280 Magnum], AFR 190 heads [68cc chambers], flat top forged pistons w. 5cc relief, 6 inch connecting rods, and a zero-decked block with a .039 head gasket. That equates to 10.6:1 static compression, 8.44 dynamic compression. I know that is somewhat on the edge of what pump gas will accommodate. I had it run on an engine dyno to set timing and dial in the carburetor, and its best pull was 450 hp @ 5200 rpm/468 ft. lbs. of torque @ 4300 rpm. It made the most power with 32 degrees total. It runs fine on 92 octane pump gas, it will cruise all day in overdrive [700R4] at 2100-2200 rpm without ever dropping down a gear to climb a moderate hill. But if you get much too below 1800 rpm, it is going to want a lower gear. Is this because the engine makes so much torque and the vehicle is so light? This is in a '32 Ford coupe weighing around 2600 lbs.

Originally Posted by rumrumm

I have been watching this thread, and I have a question. I am not trying to start an argument with you, techinspector1, as you have considerably more experience than I have. But I don't quite understand your recommended cruise rpm for a cam with 230 degrees @ .050 duration. Perhaps you can explain that to me because I have achieved different result. My 383 has a 230 cam [CompCams 280 Magnum], AFR 190 heads [68cc chambers], flat top forged pistons w. 5cc relief, 6 inch connecting rods, and a zero-decked block with a .039 head gasket. That equates to 10.6:1 static compression, 8.44 dynamic compression. I know that is somewhat on the edge of what pump gas will accommodate. I had it run on an engine dyno to set timing and dial in the carburetor, and its best pull was 450 hp @ 5200 rpm/468 ft. lbs. of torque @ 4300 rpm. It made the most power with 32 degrees total. It runs fine on 92 octane pump gas, it will cruise all day in overdrive [700R4] at 2100-2200 rpm without ever dropping down a gear to climb a moderate hill. But if you get much too below 1800 rpm, it is going to want a lower gear. Is this because the engine makes so much torque and the vehicle is so light? This is in a '32 Ford coupe weighing around 2600 lbs.

As I have stated before, I lean on the manufacturers for actual information about what will work and what will not work. None of what I say comes out of my mind without verification. In the case of posting the cruise rpm for a 230 intake cam, I would refer to the Crane HR-230/352-2S1-8 IG, 108 LSA in the Crane catalog, where that cam is listed as needing 3000-3800 cruise rpm or the Crane HR-230/359-2S-12.90 IG, 112 LSA in the Crane catalog, where that cam is listed as needing 3600-4400 cruise rpm. I have no doubt that the cam you have in your motor should be operated at approximately the same cruise rpm. The fact that you are cruising it at 2100-2200 just means that you are out of the cams operational range and that you would get much better fuel mileage and throttle response with a cam that is designed to cruise at 2100-2200 rpm's.

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Originally Posted by techinspector1

As I have stated before, I lean on the manufacturers for actual information about what will work and what will not work. None of what I say comes out of my mind without verification. In the case of posting the cruise rpm for a 230 intake cam, I would refer to the Crane HR-230/352-2S1-8 IG, 108 LSA in the Crane catalog, where that cam is listed as needing 3000-3800 cruise rpm or the Crane HR-230/359-2S-12.90 IG, 112 LSA in the Crane catalog, where that cam is listed as needing 3600-4400 cruise rpm. I have no doubt that the cam you have in your motor should be operated at approximately the same cruise rpm. The fact that you are cruising it at 2100-2200 just means that you are out of the cams operational range and that you would get much better fuel mileage and throttle response with a cam that is designed to cruise at 2100-2200 rpm's.

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That makes more sense to me now when you put it that way. Basically the cam that is in my engine will work, it will just not be as efficient or responsive if the transmission is in overdrive. I have also done some homework after reading through the comments on this thread and I am 95% that I am going with the 3500 stall and 4:56 gears for my built. That will give me a cruise RPM of 3406 in drive (not overdrive) at 60 MPH (which I probably won't do that much since most of my cruising will in town at lower speeds) . I just need to verify the size of tire I can fit under my car. I believe it is going to be 27" but I need to set the body back on the frame to verify. I have also been checking out the different stall converters available. Does anyone have an recommendations on Manufacturers (or ones to definitely stay away from). This will be my first tranny with an aftermarket stall and I don't really have any knowledge of them (all of my other builds have always been a manual transmission). Thanks.

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