250 Build in 67 Mustang

Georgia200

Well-known member
My block and crank are at the machine shop. Looks like .030 over, I will know for sure next week.

Time to put my build plan on paper and start ordering parts. My goal is to be on the road by spring.

67 Mustang coupe
DD / week end cruiser est: 3000 miles a year, mostly in town and on country roads
C4
2.79 gears
AC
PS
 
I see three separate areas: Bottom end Head / exhaust

On the bottom end Im thinking OZ 3332H pistons and Taurus E63E-B1A rods. The rods are on ebay used pretty often, Summit for the pistons.

I do not want to mill the block so CR adjustment will have to be made with the head gasket and combustion chamber volume.

How much CR can I run with 91 octane/10% ethanol?

Stock oil pump

DS11

1965 fuel pump because I like the filter and I already have a new one.

What cam? I want a smooth idle.

I have a C9DE-M head. I have a new 1100, but if my machine shop can mill the head for a 2100 at a reasonable cost, I will do that. Stock valvetrain, I dont want to mess with adjusting valves.

Im planning on the stock exhaust manifold or a single outlet header. I have no idea how a header will interfere with the starter and alt/ac bracket. I have a C90A-2882 C alt/ac bracket.

Cam recommendation? Will it be different for a 1100 or 2100? Compression?
 
starting to get confused (easliy done). Is this the same post elsewhere?
I think 1 way to reduce is by IDing CR 1st, go fr there...
The CR comes frm that ol time fav of all automtive Qs "What's the final application?"
Do U have "the Hanbook"?

"...How much CR can I run with 91 octane?..."
average 9.5 I'd say but it not done ina vacum there's (timing, cam, etc too).
 
New thread to focus on the engine build alone.

Yes I have the handbook, very useful but dated in the sense that the internet contains much more information.

I thought I was clear on "What's the final application?" DD / weekend cruiser, I can add no track, no high rpm, just a nice driver.

I asked what CR i can run on pump gas with 10% ethanol.

The CR is a big question, as I think more about it, I realize that I need more information.

I have (2) C9DE - M heads. one of them untouched, one of them IDK. In either case, I doubt I will be able to keep the stock 62cc combustion chambers, so I need to ID that value first. Assuming 8.8-9.3 final CR, I may keep my stock rods and run flat tops.

Still need some opinions/guidence.
 
The trouble with building a 250 is the amount of Quench or pistions being so far down the hole (from .123 to .150 down the bore depending on year). Stock these 250’s can be at 8.0 to 8.5 to 1 C. R. with a few real early 250's (1969-71) maybe a little bit more. Hope you did or can take some measurements of pistion height distance of #1 & #6 pistions at TDC, during the tear down so you know we're you starting from. Ideally in a Hi Performance build up we would want to see around .035 to .050 of quench, the two most current available head gaskets are FelPro at about .050 and Victor at .044.

Because 250's can become detonation prone when you start raising the compression ratio higher, only cutting the head to get the compression ratio up isn't really the best plan action for a 250 when using the stock rods and pistons. As you stated in your first above post you had planed on using the longer Taurus E6 conecting rods, at 5.99 lenght that is really a solid choice along with a good choice in a piston. Currently one site member is also doing that exact plan to get get much closer to the ideal of a zero deck height.

Another rod choice that can be used is the 300 big six Rods they are 6.2097 in length with early 1965 to 69 rods having a .912 small end pin size and the later ones being .975. Usually these rods require a custom piston but I haven't checked pistion catalogs in quite some time so there maybe an off the shelf piston available and there are a number of people on the site that have went with a 300 Rod using custom pistons.

Otherwise 8.8 to 9.3 (running on 91) would be is a decent goal for a daily driver, the bigger 250's can also handle a bit more cam than the smaller 200, around a 264 advertised duration for your DD goal, but you can get just what would be the very best for your exact combo with a custom ground cam by calling Jerry at Schinndler racing cams, plus it costs the same as a off the shelf cam (see below link). Your starting out doing it right asking questions and forming your plan, good luck. (y) :nod:

Scheider Cams
http://schneidercams.com
 
I couldnt rotate the engine before teardown. Rust in the cylinders and a couple broken rings.

I will mock up the old pistons when I get it back to check piston height.

I dont think zero decking a 250 block is a wise move for the long haul. That doesnt leave you any room if you need to true the head in the future.

This is a D2DE block.
 
Howdy Back Georgia and All:

Aah, good memories. My 250 build was a few years ago now, but still remember the stress of juggling all of the variables. I ended up with a 9.75:1 CR because I'm at 5,000 ft elevation. I used stock rods, with the beams polished and ARP rod bolts. I had the crank assembly balanced. I milled the block .070". I had the crank off set ground to gain a little more stroke.
I chose a 260 Comp cam, which was one of the best available at that time. If I were doing it today I'd follow Bubba's advice and call Jerry. Be sure to point out the high rear end gear you are planning on. In general, I thing you will want a torque cam.

For your driving description, IIWIYS, I wouldn't stress about the quench. I would stick with dished pistons for their less prone to knock quality. That leave you with milling the head to achieve your goal CR. Maximizing quench is a high performance, best practice. It doesn't sound like you are doing that, so build to your need.

Anyway, enjoy the journey and keep us posted on what you decide on.

Adios, David
 
CZLN6":2n6fr9r4 said:
Maximizing quench is a high performance, best practice. It doesn't sound like you are doing that, so build to your need.
I don't post on the small block side very often but I saw this statement and felt the need.

Maximizing quench is very important in a street application where you are limited to pump gas octane.
The tighter the squish distance the higher the quish velocity for turbulance and the cooler the quench effect.
This becomes more critical when you are using a short duration cam for low end torque and want to push the DCR for overall efficiency especially for those of us that live closer to sea level.

On a different note, if you are looking for a smooth idle and performance use a cam that has a 112 degree Lobe Separation Angle.
 
I would go with zero deck and .044 Victor gasket and if you have to mill your head later use the FelPro .050 gasket. Or at least that's my plan with 200.
 
Zero decking is a problem if the head has been milled or will need to be milled in the future.

If I can find a couple unmolested heads, Im sucking them up for spares. There cant be that many left.
 
Yes sir that is a good strategy. I have a whole spare 250, 1979 I think, and a 200 with the big hex log head. I am currently looking for a late 200 with the big bell and another 250.
 
Would it be reasonable to use the stock 5.88" long rods and have AutoTec supply pistons with a 1.63" pin height and around a 15cc dish?
No machining to get zero deck and the compression ratio would be around 9:1 depending on head gasket and chamber volume.

Have Schneider make a 270H cam with a 112 LSA.
The DCR would be 9.2 to 9.3 and run nicely on 91 octane fuel with a little room to spare.
 
You can zero deck a 250 if you do it with different rods and pistons. I wouldn't get there with decking 60-100 thou. If the piston has a dish that will allow say 8:1 DCR or less with a stock or low duration cam and 56cc chambers, you're going to be just fine regardless. It's all in the planning and you're starting from scratch. So if you used .912 240 rods or HSC rods and custom pistons with a D dish matching the chamber in 13 or whatever cc was needed you could run an aluminum head if you wanted to AND have descent quench effect. Theoretically you could probably come out of the hole at ~.010-.015" with the gaskets available and still not interfere with the valves, depending on the lift and chamber depth and get the quench down below .040". You'd have to be real careful about that of course.

The HSC rods are the way to go iirc, too little piston left with the 240 rods or something. I'm a little fuzzy on the details right now. I remember thinking after lavron started his build that those rods with a custom piston could solve all the problems associated with the long stroke 250 and the heads available today. He's got a great build going. I think he's going with aussie hypereutectic 13cc dish pistons. The advantage of custom pistons is you can get exactly the size and shape of dish you want/need.
 
A less known option to achieve Zero decking on a 250 uses AMC 258 pistons with stock rods. The rods small end only needs slight enlarging .
from previous post:

Ford 250: bore = 3.68 / comp distance = 1.5 / dish volume = 13cc
AMC 258: bore = 3.75 / comp distance = 1.633 / D-Sump = 21cc

This puts the bore at @ .070 over and raise the piston toward the deck .133 . The specs list the pin diameter of the ford at .9122 and the AMC's at .9310 which can easily be accommodated.

The cc volume of the recess is 21ccs- which makes it ideal for this application. With the .070" overbore the bore is 3.75", stroke of 3.91, a Felpro head gasket at .050", a zero deck height, chamber volume of 60ccs and a piston recess of 21 ccs, gives a compression ratio of 8.8:1.

The 61 Comet with AMC piston 250 has run reliably for over ten years with full power track launches and long distance interstate cruising. Two years ago the head gasket blew between 4 / 5 . With repair I got to inspect the still crosshatched cylinder walls and it appeared the Head work around valves thinned comp. chamber 4/5 near gasket .

have fun

 
Econoline":20t4lsz1 said:
You can zero deck a 250 if you do it with different rods and pistons. I wouldn't get there with decking 60-100 thou. If the piston has a dish that will allow say 8:1 DCR or less with a stock or low duration cam and 56cc chambers, you're going to be just fine regardless. It's all in the planning and you're starting from scratch. So if you used .912 240 rods or HSC rods and custom pistons with a D dish matching the chamber in 13 or whatever cc was needed you could run an aluminum head if you wanted to AND have descent quench effect. Theoretically you could probably come out of the hole at ~.010-.015" with the gaskets available and still not interfere with the valves, depending on the lift and chamber depth and get the quench down below .040". You'd have to be real careful about that of course.

The HSC rods are the way to go iirc, too little piston left with the 240 rods or something. I'm a little fuzzy on the details right now. I remember thinking after lavron started his build that those rods with a custom piston could solve all the problems associated with the long stroke 250 and the heads available today. He's got a great build going. I think he's going with aussie hypereutectic 13cc dish pistons. The advantage of custom pistons is you can get exactly the size and shape of dish you want/need.

The 240 rods are 6.79" long and wouldn't work in a 250 unless you could find pistons with a 0.724" CH. Highly unlikely.

The 2.5 HSC rods (5.990") would be a good way to go. With a stock 1.50" piston, the recess would only be 0.024".
The rod ratio would increase to 1.532, a lot better than the stock 1.50.
 
My block is a 74. How much overbore can it tolerate?

The problem with AMC pistons is that you need a virgin head. A zero deck, 258 piston. .050 gasket and a 54cc head yields 9.4:1 CR.

No room if you need to true the head in the future.

Same engine with a 60cc head nets 8.86:1 CR.

Brian, I am not yet ready to buy a cam but will keep you in mind.

Im waiting for the machine shop to give me the all clear on the block.
 
Georgia200":33c7tlyd said:
My block is a 74. How much overbore can it tolerate?

The problem with AMC pistons is that you need a virgin head. A zero deck, 258 piston. .050 gasket and a 54cc head yields 9.4:1 CR.

No room if you need to true the head in the future.

Same engine with a 60cc head nets 8.86:1 CR.

Brian, I am not yet ready to buy a cam but will keep you in mind.

Im waiting for the machine shop to give me the all clear on the block.

Okay I have extra 250 blocks if you need one. But I would think yours will be fine.
 
Would you be willing to get a custom piston form AutoTec and get the exact pin height and dish volume needed for zero deck and correct compression ratio?
 
Here are a couple 250 builds of site members that might be of interest for you. This first one is the link to Lavron's budget 250 a mild build up (for his Comet) he's using the E6 5.99 rods with off the self pistons these conecting rods are .110 longer than the stock 250 rods at 5.88 so they go a long ways to help close up the quench distance. viewtopic.php?f=1&t=77057&hilit=Budget+250

Here is link to a 250 using the 300 rods (for a 1969 Mustang) with I think the custom Autotec or Racetec Pistons a more Hi Performance combo street / drag build up. viewtopic.php?f=1&t=74039&p=569484#p569484

Good luck (y) :nod:
 
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