250 overhaul suggestions

[Anonymous]

Hey all.. I'm looking to take apart my 250 and replace pretty much everything. I'm wondering what to expect and what parts to get. Are there any things that most likely won't really need to be replaced? What parts do y'all suggest? I'm wanting to keep a happy medium of efficiency/performance, so I'm not wanting to do anything really weird in there. Right now, I'm expecting to do all the gaskets, esp. the rear main seal (been leaking), new pistons & rings, timing chain & gear, oil pump.. I keep hearing that the 7 main bearing setup is tough as hell so would assume that wouldn't be necessary to replace.. ? I also don't have a small fortune to put toward this either so..

Anysuggestions are appreciated! Thanks

-Chris

 

[mugsy]

My plan of attack on my recent rebuild was this: build the bottom end for durability and longevity; build the top end (head and valve train) for speed.

So what does that mean? well replace all of the bearings and gaskets in the lower end. Over size the piston as needed and don't go over board. There is very little speed to be found in the short block. Get good replacement/new pistons, rods, bearings, etc. Also got a new oil pump, replaced the balancer that was shot, and paid for good machine shop work.

Horsepower is typically made by the three Cs. Cam shaft, compression and carburation. Besides the 250 head with the larger intake valve, I got the compression I wanted, went with a 270 cam and the Offy triple one bbl will be on soon!! Thsi is all head/valve train stuff.

I used roller rockers on another motor and didn't tell a difference. So they were left off. Bought a damper from e-bay versus the hi-po stuff. Again I don't think it makes horsepower. You won't need high end pistons if you don't go turbo, NOS or insane compression. I was even tempted to put a thermal coating on the pistons. But I resisted.

have fun,
Mugsy

 

[Anonymous]

I'm looking mostly at fordsixparts.com for parts.. here's what I'm lookin at:

Clevite 77 Cam, Rod & Main bearings
Complete Gasket Set
Chrome Moly pushrods
New springs
SI-200-RSE valves
Gear Drive timing chain/gear
Eaton FE-BBF lifters

Anyone have any advice as to what type/brand pistons to get? Cast or forged? Dished or flat? etc. I also am not sure about which Camshaft.. as suggested I won't bother w/ roller rockers. THe site says their teflon valve seals require headwork.. what are they talking about? worth it?

 

[xctasy]

The main thing is to fix the factory maliase.... a too tall block with too shallow pistons which park over 100 thou below the block face!

There are a few ways to deal with it, but I'd suggest lining your ducks up in a row, and doing this:-

You could look at some +30 2.5 HSC or 4.2 V8 replacement pistons, which are taller than the stock 250 items by over 50 thou. They are dished quite a large amount. Then look at the 6.00" rods from a couple of wrecked Taurus or Tempo 2.5's. Remove nothing from the head, and get a nice thick gasket of about 50 to 80 thou. Doing this will help correct all the things that hurt performance, fuel economy, strength, and engine design restraints. It's soooo rare to be able to do any rod swap on any engine without getting special expensive bits. The 250 is a walk in the park, because the 2.5 OHV engine is just a scaled I6 with a shorter stroke crank and about 17 years worth of extra developement.

Read Mark P posts on head and ignition!

Then spend some time chasing suppliers. 4-cyl stuff is always tougher than I6 gear. The fours vibrate lots more, rev to a much higher RPM, produce more power per cylinder, carry more load per cylinder than a six, and suffer more detonation than a I6 was ever designed for.

 

[mugsy]

Just remember.... opinions are like a**holes- every one has one and they all stink!!

Now for my opinion!

I would only replace the pushrods if they are bent or scuffed, etc. I have bought stuff from FSPP and hate to drive business away, but use that money for other things. Same thing for the valves. Replace if the existing ones are not rebuildable. There was a long thread while back about using larger 1.50 inch exhaust valves, the consensus was with no other changes it wouldn't help that much. I did replace my valves, but the ends were too worn out.

have fun,
Mugsy

 

[Anonymous]

Would I have to get the 2.5 pushrods in order to use the 2.5 pistons?

 

[Anonymous]

Would I have to get the 2.5 pushrods in order to use the 2.5 pistons?

Do you mean the connecting rods? Pushrods don't have much to do with piston choice. You should be able to use the 2.5L pistons on 250 rods (.9122" pin - anyone?).

 

[Anonymous]

you want 2.5L HSC rods as recommended by xtaxi. the 2.3L HSC flat tops have the 1.5" compression height(perfect) the 2.5L HSC pistons are a tad taller.

DB

 

[Anonymous]

So I need 2.5l rods w/ 2.3l pistons?

 

[Anonymous]

so its fine to just grab some used pistons if they look fine from a parts yard and re-ring them and replace them with the stock pistons in the engine? nothing else involed with it...the engine in my car has probably 40,000 miles max on it, rebuilt..probably less since it had 20,000 when i bought it and i dont drive all that much, i could probably still see the crosshatching slightly in the bores...maybe..i could when i bought it...so i'm sure it doesnt need too much work...or will it? and is it safe to just swap the push rods as well, how bout the lifters...should those get yoinked too? i suppose the only things that need to be removed are the head and oil pan to replace pistons n stuff?

 

[Anonymous]

bump

 

[MustangSix]

2.5 HSC rods, but I would stick with the stock 250 pistons to keep the compression down to a reasonable level.