My 390 is currently .020 over, and has few miles since the rebuild.

I've got the body off the truck, so I want to get the motor up to par while it's easily accesible.

I though about about throwing some $$ at it and getting a 427 or 428. But now, I'm thinking the 390 should be enough.

Is it possible my pistons will work with a 428 crank? If not, can I get pistons for a .020 390 that will work wit hthe 428 crank?

What connecting rods do I need and how do I ID them?

I'll probably tear it down here soon to determine what pistons I have. I just know they are .020 over, but I have no idea what compression I'm running.

Thanks,

Greg

 

Hey Greg. Sounds like what you want to do is stroke the 390. If you do that, you will need a 428 crank, the 428 external counter balance, 428 flywheel, and differnt pistons with the rings for .020 over. I have already looked at doing this before I started my rebuild and found it to be very costly. A 428 crank goes for anywhere from $450 to $800, if you can find one!

If you are looking to add horses, I'm sure there is a better way to go about it. There are books that outline what you are looking to do. I believe I've even seen one of the books in an add in the frame just right of this forum. Best I can tell you is to get some Ford HP Engine books to help you out.

Should you want to check out what I have been doing on and off over the last 2 years, check out my gallery. Other than going with a radical cam, I've got just about every high performance mod you can make. All-be-it a very good rebuild, it could have some other performance upgrades likes a roller cam or Dove heads.

Happy to answer any questions I can for ya. Good luck!

 

If you have a low compression 390 and good pistons you have all you need except for the flywheel or flexplate, and the 410/428 crank. You should not have to pay much more than $400. for the crank. The way to find out if you have the 8.5-1 pistons is to check and see if the piston comes all the way to the top of block. Use your 390 rods and harmonic ballancer and you set. I would have it ballanced.

 

I think I have low compression pistons, check them out.

http://www.thedreyerfamily.com/69f250/390pistons.htm

 

The difference in the low compression (8.5-1) is the compression height of the piston. How much below the top of the deck are the pistons. Remember the 410/428 cramk is like .100 or so longer so you have to have the 8.5-1 pistons and they will make about 10.-1 compression.

 

if you use the 428 crank, you better have the counter ballance as well. and with the longer stroke, aren't you worried about the piston slapping the head? I've never done it, but from the research I've done, I believe you need to have pistons that are offset. and if you can find a 428 crank for $400, then you are blessed!

again, good luck. hope I am wrong.

 

You can use the harmonic ballancer from the 390 the only 428 ballancer that was different was when the HP rods were used. There are a few years of pickup pistons that use a 8.5-1 piston that is about .100+ shorter compression height that will work with the 410/428 crank in fact it is listed to be used in the 410. eith about 10.-1 comp. I am not sure of the offset piston but I think all piston have a offeset pin to keep the piston form slapping on culinder walls, but I might be wrong on that one I always put the piston in with the index to the front no matter what. Remember I said that I would always have the rotation ballanced.

 

Here is a kit that I wish they had out when I tore down my engine. I would have gone this route. This should give you an idea on a "do it right the first time" type kit. However, I'm not so sure this is what you want with your motor.

auction on eBay

I see that there is a 428 crank out there now too. You could get the crank for $450 if you didn't want to go with the kit.

crank for sale

Best of luck with it!

 

Gidde Up

Where would you get a block that could take a bore of 4.25

 

From the pics, it looks like the pistons might work. On my setup, I had to have the pistons cut down some or order some new pistons and I opted to have them cut down.

Yours don't look to be even with the block, but I can't tell how far down they are. Even if they are out of the block a bit, you can still use them with some cutting off the top.

This is really an issue of how much money you want to spend, I like the flat pistons with only valve cuts (eye brows) because this offers more squish effect on the FE's.

The 428 crank might be just the ticket to bring the pistons up even with the top of the block and then all you need is the flywheel/flexplate and balancing of the engine.

I paid $375 for my 428 crank and $250 for balancing, as for the flywheel, I bought a new billet steel McLeod setup because I was having trouble finding one.

Overall, the cost is a bit high. If the parts you have are in good working order... crank doesn't need reground, bearings are good... then I'd think about additions to the 390 like porting the heads, intake, ...

I went with the 428 because I had pretty much an open ended budget for the engine and wanted the most torque I could get.

 

the only block that will get 482 cubes is the 427 block bored .020. No 428 block or 390 block can do it. On the other hand, using that kit with a 390 yields a potential of 450 cubes and with a 428 block you can get roughly 460 cubes. I personally am going to use this kit and a 428 block. These kits would make torque monsters out of our FE's. Ratsmoker desktopped this motor for me and it made 513hp at 5k and 580ft lbs of torques at 3500, not bad I'd say

 

After purchasing a 428 crank myself for your very purpose, I called up the Ford performance racing hotline. I am told by both the guys at the Ford performance hotline, as well as an FE specialist speed shop that they (ford guys) recommend that you do NOT want to stroke a 390 for a heavy, truck type application.

Reason: " With the longer stroke, the piston will sit at top dead center too long at low RPM's and especially under HEAVY LOADS. Since the piston cannot get out of the way fast enough, much of the heat and combustion is going to blow back up through your valve guides - it has to go somehwere. You can expect to replace parts of your valve train every 1000 to 2000 miles. For this very reason, when Ford designed the 429/460 for trucks, they went with a large bore and a short stroke. If you want bigger cubes and more power, then do the conversion to a 460."

This identical quote came from both Ford and John from the FE recommended speed shop (586-468-3710 if you want to call).

This really bursted my bubble; on paper, this conversion should have worked out beautifully. Trust me, I called Ford THREE times and talked to three different guys to make sure this wasn't the opninon of just one guy.

Thus, I am just beefing the hell out of my FE 390. Ultimately, the decision is yours. I hope this was helpful. BTW, I still have the crank if anyone is interested.

 

You could just use shorter rods. I dont see how a 460 would be any different when stroking it because it would do the exact same thing. I'm sure they know what they are talking about, but the way one engine works isn't different from any other, meaning, there is no way that ONLY a stroked 390 would do that and a 460 would be fine. I am just going to pretend that I didnt hear that and go on about my business as I am stoked about my upcoming project. We will see.

 

They just want to sell you one of those nice 460 blocks. First off how is cylinder pressure going to blow gasses back through the valve guides if the valves aren't leaking. You want the pistons to "dwell" longer. It promotes better combustion and more power. That is the most rediculous, uneducated statement I have ever heard about the FE. I guess the 300 I6 was a flop then as it had a 4" stroke and thrived at low RPMS. If they are saying that a bigger cam will open the valves during the power stroke and let off cylinder pressure throught the exhaust then this is true for every engine. They are stroking 460s out to 6" nowadays and making tons of power. The new 4.6L cobra engine has 8.9" long rods which equates to massive hang time at the TDC area.

 

I am not talking about a stroked 429/460, just a stock 429/460.

A stock 429 has a 3.58 inch stroke; a 460 has a 3.85 inch stroke. The 390 has a 3.78 stroke, the 410 conversion would have a stroke of 3.98. You can see that the 410 has a much longer stroke than either of the biggest production gas engines Ford designed. They went with a giant bore and kept the stroke modest. Ford engineers are pretty smart; there is a reason why they did not design a truck motor with a really long stroke. Big blocks already have long strokes; it is not like were are talking about stroking a 289, 302 or even a 351.

So, you are right, a stroked 429/460 would behave no differently than a stroked 390. Again, I was referring to a stock 429/460 stroke though.