Will a 302 bolt up to a 51 Merc 3sp od trans?

[Solo_909]

Hey fellas,

So I know some of you guys won’t like this but Will a 302 bolt up to a 51 Merc 3sp od trans? I can not afford a flathead rebuild nor do I have the skills or talent to rebuild it. My buddy has fresh 302 that I would like to swap in but would love to keep the original trans since I just put a new clutch kit in.

Any help and wisdom would be greatly appreciated.

Thanks,
George

[Tinker]

Hey George if you are going through all that trouble (I understand flathead rebuild cost) It might be better to just do the transmission at he same time also. Go open drive diff and make it all happy.


You can certainly put a 302 in with the merc od too.


http://www.wilcap.com/




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[51 MERC-CT]

And then there's the oil pan fit.

[mfirth]

There must be oil pans that will work here as i knew of a 51 Merc with a 302 in it.

[Frank Miller]

Not sure how well that original trans will stand up to a 302. You say you do not have the skills to rebuild a flathead but you can put in a completely different motor with skill sets equal to or higher, in my opinion. If your flathead is running and you want to spend minimal money then put new rings and bearings and do the valves. It won't be completely rebuilt but will give you a better engine at minimum cost. I think your car will retain more value too.

[ponymare]

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If the merc trans is the round 8 bolt, you can get an adaptor, if its the 4 bolt, some early sbf bellhousing were drilled for both patterns. Not sure about being able to use your new clutch and p plate on the later engine though.

[JSeery]

I can not see this type of modification as cheap or easy. Attempting it because it is perceived as cheaper than repairing a flathead is a false premise in my option. You install a 302 because you want to build a street rod type of vehicle, not because it is cheap. If you want cheap go with a sbc.

The rear sump oil pans require a different oil pump pickup and a different front engine cover. There are motor mounts that have to be installed. The radiator has to be changed. A transmission adaptor may be required and the flywheel may need to be drill to except the pressure plate. There will be exhaust header issues especially around the steering box.

Sure it can be done, but there is cost & building skills involved. I would think it would be must easier and cheaper to do a minimal rebuild on the existing flathead engine.

Looks like there is some information over on the HAMB.

https://www.jalopyjournal.com/forum/...9-merc.818277/

https://www.jalopyjournal.com/forum/...shoebox.96611/

http://shoebox-central.com/1949-1950...conversion-kit

[V8COOPMAN]

Originally Posted by Solo_909

Hey fellas,

So I know some of you guys won’t like this but Will a 302 bolt up to a 51 Merc 3sp od trans? I can not afford a flathead rebuild nor do I have the skills or talent to rebuild it. My buddy has fresh 302 that I would like to swap in but would love to keep the original trans since I just put a new clutch kit in.

Any help and wisdom would be greatly appreciated.

Thanks,
George

George.....Is this for your '35 coupe? If so, I see at least a couple of reasons that this MAY not work-out. Furthermore, 1951 Mercs (early and late) came with two entirely different transmissions. Either one being an OVERDRIVE will make it too long for your '35, plus bolting to the torque tube would be crazy. What are you really trying to do? DD

[JSeery]

That's an interesting twist! Guess I was assuming the question was installing into a 51 Merc, should have checked.

[Solo_909]

Thanks guys,

So yes this is for a 51 Merc and not my 35. I sold my 35 a couple months ago.

So let me ask you this is there an adaptor or something that will allow me to use my stock pedal assembly with a manual transmission?

[TomT/Williamsburg]

Could it work? Yes, with enough time, effort, and money. Will you be changing a tranny or rear down the road? Depends how on how you drive it once done whether that will be sooner or later. If you liked the way the car ran before, I would start looking for a good, running flatheads, one that you can see and hear running, before going the 392 route. You may be opening a can of worms that may end up costing you more than if you just had your flattie rebuilt. I know you are West coast and things are different than eaet coast flatheads availability but they do pop up quite often if you are lookng hard enough. There are several for sale on the HAMB that youi could be able to buy and pickup for cheaper than a flattie rebuild. That would be my first choice.

Second choice, go with an all modern driveline for the 302. You then know what you got and everything is like-to-like and replacing major components is much less likely this way.

This is just mho ....

[Ol' Ron]

The year 1951 was a transition one for the Merc. early ones had the Big Bell and the late ones were like the ford unit. AS for the OD that's very fragile, and had trouble holding up to the flathead. Using the later 55/57 OD would be stronger. and had the same bolt pattern.

[40 Deluxe]

Originally Posted by Solo_909

Hey fellas,

So I know some of you guys won’t like this but Will a 302 bolt up to a 51 Merc 3sp od trans? I can not afford a flathead rebuild nor do I have the skills or talent to rebuild it. My buddy has fresh 302 that I would like to swap in but would love to keep the original trans since I just put a new clutch kit in.

Any help and wisdom would be greatly appreciated.

Thanks,
George

There's no mystery to overhauling a flathead! It's all straight forward nuts and bolts. Unless the block is cracked or cylinders deeply scored, or crankshaft way out of round, a simple re-ring and bearing job with lapping the valves is cheap and will run a long time. These engines are very forgiving!

If you have an early'51, you have the early style 8 bolt bellhousing, and I believe, the large spline input shaft and diaphragm Borg and Beck pressure plate. So you will need a special bellhousing adapter (large dollars), plus redrilling the flywheel. Make sure the flywheel matches the year of the 302 as there are different balance weights (early 3402's are 28 oz., later are 50 oz.). Then there's the muffler shop expense for the exhaust system, motor mounts, etc.

[Solo_909]

Okay,

Thanks for all the wisdom guys.

I guess my next question is, is there some sort of adaptor that would allow me to use my original pedal set up with a manual trans?

[JSeery]

I know nothing about Mercurys, where they all automatics? How different is the pedal bracket setup from the Fords?

[40 Deluxe]

Originally Posted by JSeery

I know nothing about Mercurys, where they all automatics? How different is the pedal bracket setup from the Fords?

No, this one is a three speed with overdrive.

[JSeery]

So why would the pedals need to be modified? Are you looking to change out the transmission now?

[rotorwrench]

The 1949 thru 51 used two variations of the rotating fork throw out shaft with an equalizer. The late 51 Mercury transmissions (R10 overdrive) had the 4-bolt Borg Warner narrow pattern. This is about the same as the early 260 & 289 manual trans V8s had but that changed after the bell was changed to 6-bolt instead of the earlier 5-bolt set up. The 302 is the later 6-bolt but 289 bells with fit it if you can find one with the old narrow 4-bolt BW pattern. Big problem is that it is a fulcrum arm clutch release. The through the floor pedals may not work well. Swing pedal came out in 52 and all the later cars are set up to work with a fulcrum arm clutch.

Most folks that go 302 use all the later stuff. Your R10 overdrive has value. You may be able to sell it or do some horse trading. The later T85 transmission with R11 overdrive used in Lincolns and later Ford & Mercury applications was a way lot stronger than the R10. The R10 will work if you baby it but the R11 will work behind a 390FE motor and take most everything you can throw at it.

[JSeery]

And all of this is to save money on a rebuild of the original engine?

[Solo_909]

Originally Posted by JSeery

So why would the pedals need to be modified? Are you looking to change out the transmission now?

Originally Posted by JSeery

And all of this is to save money on a rebuild of the original engine?

Iwas asking if the pedals needed to be modified for an upgraded manual trans.


And yes all this to save money and upgrade my driveline. A flathead shortblock costs 3k at its cheapest and if I want a full rebuild I’m looking at 9k+. I can swap in a brand new turn key 302 and a brand new transmission, new wiring harness, new dash, and rearend and still have money left over and be able to drive everywhere and anywhere.

Some of us don’t want everything down to the bolt original. Some of us love old cars but were born after they were made so the motor doesn’t really have that much value to us. Now don’t get me wrong I would have loved to keep the Flathead but......... since it’s toast it’s cheaper and a better decision for me to upgrade everything.

Now some of you guys will say just rebuild it myself. That sounds great but I don’t have the tools, room, or knowledge to do so. It sounds easy but I will bet money it’s not as easy as people say for someone who would have to do it by myself and depend on other local mechanics who have no idea what to do with a flathead to help me if I’m in a bind. Plus when you try to ask a question on the internet you get 25 different answers all making it more difficult for someone like me.