Replacing a 283 motor with a 283H motor

Replacing a 283 motor with a 283H motor

Joined: May 30th, 2012, 6:08 pm

June 3rd, 2012, 11:22 am #1

I have a 283 flywheel forward motor in my new 1968 20'Chris Craft Corsair and am looking at replacing the motor with a new one I found. The one I found has 283H stamped on the exhaust manifold. Aside from the bolt pattern of the valve covers, it looks just like the standard 283 that is in there now. Can you tell me what the H means (I think it is a Hercules motor) and will the two interchange well?
Last edited by ronalddsherman on June 4th, 2012, 2:53 pm, edited 1 time in total.
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Joined: May 30th, 2012, 6:08 pm

June 4th, 2012, 2:52 pm #2

The 283-H turned out to be just the exhaust manifolds from the original motor. The actual engine is a 327 with the 283 manifolds.

A couple of questions:

Will I have any issues dropping in a 327 to replace a 283?

The 327 has the old style generator. The 283 has an alternator. I am thinking about replacing the generator with the alternator. Any issues to be aware of?

Thanks!
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Joined: July 15th, 2005, 8:09 pm

June 4th, 2012, 3:33 pm #3

The 283H is "the" first small block GM V8 Chris Craft used in boats. The runabout model (which I have in my 17' mahogany speedboat) uses the same oil for the motor and the transmission, and the "H" designation has nothing to do with Hercules. Interesting though, the Hercules and the 283H share IDENTICAL motor mount points and this was no accident.

The 283H is the old style flywheel forward design (I posted photos of mine earlier in one of your threads) and it uses a generator driven from belts, that uses the shaft through the generator to also drive the 4-port water pump.

It is not unusual at all to find exhaust manifolds swapped around from motor to motor, and sometimes it really gives false readings when the motor identification is also on that exhaust manifold.

Basically if you have the flywheel aft 283F, there would be NO issues I am aware of swapping in a 327F or vice versa, as they are externally identical motors. If you are swapping in a flywheel forward small block motor, that would seem to fit and work too, as the flywheel really works best up fron on a runabout this size anyway. Flywheelaft motors work better in larger boats, but they do fine in runabouts until there is a little bilge water.

Send in some photos, we'll help you any way we can.

best,

Paul

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Joined: May 30th, 2012, 6:08 pm

June 4th, 2012, 4:59 pm #4

Both the old 283 and the new 327 are flywheel forward.

Would you recommend swapping out the geonerator for the alternator?
Last edited by ronalddsherman on June 4th, 2012, 4:59 pm, edited 1 time in total.
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Paul
Paul

June 4th, 2012, 5:37 pm #5

Unlike our Forum Regular, Mark, who has rebuilt these things blindfolded since a small child, I am not as familiar but I do know some of the details.

If the distributor is not on the same end of the motor as the flywheel and is driven off the adapter to the transmission, it is a H motor.

If the distributor is on the flywheel end of the motor and the flywheel is AFT, then it is a standard F motor.

If the distributor is on the flywheel end of the motor and the flywheel is FORWARD, then it is either a Q motor or some sort of an oddball F motor I don't know about, which is possible because I don't get out much and I don't know which fork to use first.

So what do the valve covers say? Wondering if they have been swapped too? Photos will clear this up quick.

When you mention "generator" it makes me think you really do have a H motor ! If it charges, why change it? Some people think the generator does little or nothing at idle, which may be true, but would not appear to be an issue.

Regards,

Paul
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Joined: May 30th, 2012, 6:08 pm

June 7th, 2012, 1:56 pm #6

Sorry about the absense of pictures. Most of the photos are on a mobile device and the process is difficult from there.

It appears the engine is a 32. My Tech told me when they rebuilt this engine they used a 327 block, it also has newer style heads than the original 283.

We looked up the block casting # and it comes up as 1964-1967 302/327/350, My Tech thinks it is the 327 just from experience but the only way to know for sure is measure bore/stroke etc.

Here is the block casting # 3892657

The distributor is in the back with the flywheel forward. It looks like it will be a good fit. The generator was only a concern since I have an alternator on the existing engine and COULD change it if there is a history of generator issues that I could prevent.

Right now, I am going down the path that if, during the engine test, the generator is working, I will leave it and deal with it if and when it breaks down. I will keep the alternator and associated components just in case.

Here is the actual engine assembly


Here is the valve cover that is on it
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Paul
Paul

June 7th, 2012, 2:54 pm #7

Sure enough that is an H motor. No thermostat, 4-port Sherwood, old style intake manifold with the filler tube, and distributor off the transmission housing. If the original crankshaft from the 283 was re-used then you have the oil supply to the transmission, if a new crankshaft was used, then you must drill the end of the crankshaft to supply oil to the transmission.

The motor oil on this model is also common with the transmission, they are bolted together so the same oil flows through both.

Good little motors, I am running one in my 17' 1956 now and it is a rocket.

best,

Paul
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