I'm looking for some suggestions regarding engine choice. My 50 F1 has a 255 Merc Flathead with a four speed trans in it now. The flatty leaks like a sieve, and the four speed limits me to about 50 mph.

But...... It's cool! I love it and want to keep it, but I'm afraid I'm gonna get a grand or two into a t5 swap, 9" rear end,and Toyota PS conversion and find myself with a crapped out flatty that will cost $3K to rebuild.

My question is; Do I move forward with the aforementioned upgrades and replace the seals and gaskets on the flatty, or do I go ahead and pull the trigger on a 302/AOD swap. I can probably get into a new 302 for about $1000-1500.

I wouldn't be so hesitant about just sealing up the flatty, but it seems it may have some issues more than just the leaks. I'm getting a good amount of blow-by when I start it, and I may also have some valvetrain issues.

I wouldn't be agonizing over this decision if I didn't LOVE my flathead so much.

Thoughts? Opinions?

 

Stay with the flattie. You won't regret it. Plus, your truck will be different from the others that have newer engine swaps.

 

It depends on what is important to you. There is the "cool" factor of the flatty, but it will be more costly and require more maintenance. The late model gives much more dependability and flexibility for less money.
For a weekend driver and a healthy wallet, the former may be desirable, for a daily driver that needs to be dependable without tinkering the late model wins.
PS: you don't need to go to a 9" with either of these engine tranny combos, an 8" would be plenty strong and much cheaper.

 

Don't forget the other costs involved in making the swap. You have to remove or chop out your original transmission crossmember and flathead motor mounts (usually). Then don't forget a 12 volt conversion if it's still stock 6 volt. A radiator swap and the addition of a transmission cooler is also needed. Also, you'll need new motor mounts for the 302. Then you've already mentioned the rear end issues. I'm sure I've forgotten other things like new instruments, wiring issues, transmission shifter, removing your clutch pedal, etc. Also, you will run into the dilemma of "do I keep the original drum brakes or do a disc conversion considering I'm gonna have more horses under the hood and the need for better stopping power.". The point is that the costs could very well be even or more by the time you're finished (especially if you factor in your time and labor).

 

I agree with Doc completely. The only added benefits of a transplant is parts availability locally and you end up with more power, but a complete transplant for $1500 isn't likely considering all the costs. I don't know why AX thinks there is more maintenance on a flatty, that has not been my experience. If yours is leaking (antifreeze? oil?) a $100 worth of gaskets will fix that. Any 302 you get for the money you've described is likely to be leaking, and an AOD that old is going to be a crap-shoot as far as needing a $1200 rebuild.

Whichever you choose, it will make a huge difference in your truck!

 

I really like a flattie....that being said, part of your decision depends on your skill set. If you're able to tear down the flathead to replace gaskets and seals, maybe throw in a little bit of extra work to freshen up the engine (rings, possibly bearings, and a valve job if they need it). I've always been amazed at how well old Ford engines will run even when the clearances are way out of tolerance. A minor overhaul could breathe some new life into your engine. How much do you drive your truck?

Dan

 

Since you have a 4 speed have you thought about just going to a 9" rear with a lower numerically number gear to get a more comfortable cruise rpm? A (" should run you around 150-250 then a driveshaft modification is not to hard by a shop. So it costs you 500-600 bucks and lower rpms. I would do that before a t5. Also you could probably get a different gear set for your existing rear to help. Just the rear would make a big difference in your motor.

Also what fluids are you leaking?

 

I chose the route of keeping the flathead and eventually decided transmission change had to happen.
You can seal up a leaky flatty with just effort, a nominal amount of gaskets and a tube of "form a gasket" that is for sure.
if your blowby is like what I had, a couple oil changes and some TLC tuning it up will get that to settle down - they always leak after sitting extended time it seams.

I did a junkyard T5, and professional driveshaft shorten/balance and all the parts and pieces of a trans swap for less than $400 ($150 for the driveshaft, $150 for the trans). Being west of the miss, your yard prices will be about the same I will bet.

I did a complete 9" rear end swap for under $200, again $150 for the "axle beam complete" and then new seals, fluid, etc.

With just a little bit of money you can take it from museum piece to very good driver.

There's nothing hard about keeping a flattie on the road. I vote for keeping the flattie it can be done reasonably and makes a good reliable machine.

 

i vote flatty but i got a 9in and a c4 for 75 bucks did nothing but seals to both and my bro rebuilt the flatty before he died

 

I appreciate the replies and opinions. I'm not sure if I conveyed it sufficiently in my original post, but I LOVE my flattie! I was hoping to hear reasons to keep her.

She's just leaking oil from the rear main, oil pan gasket, and as unlikely as it seems, from around the base of the fuel pump. It's messy up front but seems to be more from the road draft tube than from the main (planning on a PCV conversion).

As Doc and Ross said, I know I am looking at a chunk of change either way I go, and if so, why not keep the flathead?

I am definitely leaning toward flattie, t5, rear end, Toyota PS, Power Disc brakes, and possibly AC. Not to mention new lowering springs, king pins, tie rod ends, bushings and pins.

My other thought was Mustang II, 302, AOD, 9". (power discs, PS, and AC are all included in the package, but need a little more fabbing.

I took some time to break down each option (worst case), and came out pretty close $ wise either way if a rebuild is necessary.

I know it's a trade off and each has their benefit. This truck will be driven often, but not a daily driver. Probably a 3 time/week driver.

Again, thanks! I think I just needed to hear someone else tell me what my inner voice was already telling me. I appreciate the dissenting opinions also and know they also have merit, but I am stuck on the nostalgia that drew me to my truck in the first place.

 

Oh, I forgot to mention. The transmission has to go. It is about to give up the ghost. Third gear whines like a freight train, 1st is useless since I have no stumps to pull or hay to load. Lack of synchros is killing me too. I see a new trans In my future no matter what I do.

 

Despite the noise I bet that stump puller has another 60 years in her. Mine is in great shape and I just pulled her. The spur cut gears wail like banshees - that's just how they work.

Put some serious consideration into this as well... How soon do you want to drive it. 4-5 day weekend and you could be driving a new rear end and tranny... Tear it all down for a front end transplant and you will be 2-3 years and joining the clan here of "in pieces and never finished"

 

OK I have a couple of questions you need to ask yourself (and i'm sure some of us would like to hear the answers as well)
1-Can you afford to spend 5 grand on an engine swap assuming 302 and an AOD tranny
2-Are your skills up to the task
3-Have you checked out your flatty to see what all is wrong with it ie. compression test,leakdown test,pressure test cooling system .pull the heads to have a look at the valves and cylinder wear .
Here is my opinion ,If the answer to question number one and two is yes and the block is not too badly cracked then keep it rebuild it put a T% behind it and Love it .

 

If you do a T5 the stock rear end can stay, in fact it would be a waste to change it unless it's a goner. If you do the T5 (and any stock brake repairs needed), drive it like that a while before you start throwing serious money at it for lowering and IFS.

 

I'll echo Ross' comments in that if you swap in an overdrive trans, auto or manual, you can keep the stock rear, no matter if you keep the flattie or change to an OHV engine later. Adding an extra gear is all that's necessary to give you additional top speed while keeping the revs in the lower stratosphere.