Thread: 1937 Plymouth 5 Window Coupe

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Originally Posted by mprevo

If I were to decide to swap the cam out. Would either one of these be a better match for me?

Howards Cams Hydraulic Roller Camshafts 180265-10 - Free Shipping on Orders Over $99 at Summit Racing

or

Howards Cams Hydraulic Roller Camshafts 180245-10 - Free Shipping on Orders Over $99 at Summit Racing

Both of these cams are recommended by the people I bought my parts from?

Nowhere in any of this thread have you told us what the exact static compression ratio of the motor is and you cannot intelligently choose a cam for a motor until you know that. That's why I asked you in post #14 what the block deck height was and you never answered. You need to know either the block deck height or how far the piston is down in the bore with the piston at top dead center (piston deck height). I went back and read where you have used a 0.030" gasket. Can you give me the part number and manufacturer of the gaskets?

Here's the thing: Your stack is 9.015". If the block deck height is 9.015" (zero deck, then the static compression ratio of the motor will be 10.74:1. This is the upper limit that I can figure for you with the information you have provided so far.
If the block deck height is 9.025" (0.010" piston deck height), then the static compression ratio of the motor will be 10.49:1. This is the lower limit that I can figure for you with the information you have provided so far. Either of these static compression ratios will require a cam with at least ~222 degrees intake duration @0.050" tappet lift or a cam with at most ~238 degrees intake duration @0.050" tappet lift. Disregard exhaust duration, it plays no role in figuring the cam you need. What you are interested in knowing is where the cam closes the intake valve.

If I were building your motor, I wouldn't have built it with this much static compression ratio in the first place, but if I did, I would choose a cam in the middle of this range, ~230 degrees intake duration @0.050" tappet lift. I would also choose a cam ground on a 112 degree lobe separation angle or even a 114 degree lobe separation angle in order to try to have a little intake manifold vacuum for power brakes. I predict you'll have to use hydroboost off an Astro Van anyway, but having a little manifold vacuum to provide a signal for the carburetor is a good thing.

You cannot use a smaller cam than 222 because the intake closing point of such a cam will make too much cylinder pressure for use on pump gas and you'll detonate the motor to destruction. Cruising rpm's for a 230 cam will be in the area of 3600-4400, so again, the 700R4 is not the transmission that you want to use, particularly with that long fosdick 1-2 shift. What you need is a TH400, a set of 4.44/4.56 gears and a 3500 stall 10" converter. Don't be fooled into using a 12" converter with the fins bent over, go for a 10" to begin with. Budget $500 to $600.

BOTTOM LINE: You have painted yourself into a corner with your choice of parts.

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