250 rebuild

[Anonymous]

I just bought a '75 Granada with a 250, C4, and 8".
The plan is to put this combo into a '61 Comet and replace the 170 and 3 speed.
The 250 has a stuck intake valve, and the thing has a good 135,000 miles on it. I'm going to take the mill to a machine shop and have the head and the block done right. I'm thinking a mild cam (a little more than stock) and get that thing to breath a little better. (port the head intake and exhaust).

What are some recomendations on things to have done or a good set up?

This will be on a smog free vehicle.
On the front page of this site is a break down of levels on builds. I'm looking at something between a level 2 and level 3.

I want the car to be set up as a good daily driver that can keep up with traffic here in San Diego, and have the thing get up and go when the gas pedal is hit.

 

[Bobscoupe]

Replace the timing set with one from a 69 - 72 250.

 

[Anonymous]

Replace the timing set with one from a 69 - 72 250.

why is that?
not that I'm questioning your input, I'd just like to know.

 

[wallaka]

It's not retarded as much as the newer ones, it may be cut straight up. More power and fuel economy.

 

[Anonymous]

Cool.....
little tid bits like this are really helpfull.
What about head work, what should be done other than basic valve job?
3 angle grind? porting?
what about a good cam, carb, intake, and exhaust combo?

 

[Rustang Racer]

I would go with something like a Clifford 264H cam (.444 lift, short duration so its still very streetable), three angle valve job, pocket port the head mostly just smoothing sharp edges behind the valves, and go to a 2bbl carb (either a Holley 350 or 500). You could mill the intake to mount the carb directly, which would give more power or you could use a clifford adapter plate which won't give quite as much power but is much easier as long as you have enough hood clearance. The carb by itself will make a big difference. Changing to a 69-72 timing set as already mentioned is definitely a good idea.

Fully porting the head will make a difference but I don't think its worth the money or effort since you can't remove the intake. If you want to make that much power you should probably look at AzCoupe's aluminum head that will be coming out soon.

 

[Anonymous]

Thanks John,
I really don't want to put that much dough into it, nor that much time.
I have other projects waiting in line like my 62 Falcon Gasser.
I like the idea of a Holley 350, but a 500? would that be over carb'ing it?

 

[powerband]

'Nuthin nicer than the sweeping tail of the 60/61 Comet. One of the last American cars with real FINS!.

I'm kinda' partial because I'm runnin a '61 Comet with a D7xx('77) 250. I've been participating in many threads on getting the 250 in the body,and dealing with related "issues" like the steering center link, firewall and fan clearance.

I'm running a Toploader 3speed with modified 3OTTand the "The Legacy Mill";
Jack Clifford, legendary six cylinder racer, record holder and engine builder's shop, performance built Ford 250 six engine- 10:1 Pistons, Clifford rods, Clifford 272H Cam, line bored & balanced bottom end, Cloyes timing set, Fisher balancer, 1.88 int. valves, Ported and relieved, Offy 3X1 w/3 Holleys, Re-curved distrib., the works, a few mysteries...

I'm anxious to hear more of this build and follow the adventures.

Powerband

 

[Rustang Racer]

Well if you don't want to spend too much then I would focus on the carb to get the most power. There's been a lot of discussion about 350 vs 500 carbs so try searching the forum. For a daily driver the 350 would probably be better but I haven't personally used either one because I don't have the hood clearance. A holley 2300 series 350cfm carb is about $250 new plus the cost of the adapter plate but you'll end up with a good carb instead of a 30 year old one.

If you have to pull the head and take it to a machine shop to get the car running you should definitely go for the three angle valve job. Thats probably what the machinist will do by default anyway. If you think you might install a cam in the future its cheapest to do that while the head is off. But if you are not going to do a carb upgrade any time soon, don't waste your money on a cam. I have a 264 cam but still have the stock carb for now and the cam hardly made any difference. It will make a difference once I upgrade the carb though.

 

[xctasy]

You are fortunate that Powerband has done the homework, along with 61Ranchero. Pre 63's are not compatible with the 250 due to the firewall clearance. The rest is able to be sorted out with reasonable ease.

The hitting of the firewall with a big hammer and a little warming with an oxy actetylne torch will be lots of fun, but you'll get the clearance.

The US 250 is a very strong engine. Take the advice here of people who have one. Its a great engine.

Please make certain you consider getting some HSC 2.5 or 255 Ford V8 pistons in stock size if the engine bore is okay. Read the posts of Hot6t Falcon and decide on a course of action.

Its great to see people reworking these lovely old machines!

 

[CZLN6]

Howdy Slick and All:

There are three areas in the short block that limit performance of a '75 250. They are; 1- advanced cam timing to help low end torque, emissions and vacuum, 2- an incredibly large deck clearance, which contributes to, 3. Low compression ratio. The '75 250 has an advertized CR of 8:1.

My '72 250 block had a deck height of .150"!!! Redicules!!! For efficiecy the deck height should be ZERO. An aftermarket head gasket will add .045" to .055", more than enough for valve/piston clearance. Deck clearance is the combination of deck height and gasket thickness. If the Deck clearance is in the .035" to .050" a quench effect is created when the piston comes to the top of the cylinder and intake charge is squeesed out from the non chamber/ non dish areas. This causes turbulence and increased combustion efficiency. Without, expect no turbulence and a knock prone engine as heat and CR goes up.

These engines are also at the beginning of the smog crutches, that also effect performance. So the carb may be hurtful depending on which this engine has. It may have a Carter RBS (good) or a Carter YF or YFA (not so good). The good news is that a '75 should have a DuraSpark II electronic ignition system. If the distributor cap is the larger diameter type it is a II, if not, it is most likely a 1st generation DuraSpark system.

It would be helpful if you would post the casting code for the head and block, as well as the carb and distributor.

If you do plan to rebuild the block there are several economical steps that can be taken that would make for a better, more durable, more powerful engine. I'm confused though. In your intro you said you were going to rebuild the head and shortblock, but later you said you didn't want to put "That much" into it. It costs no more to do the block right, if you're going to rebuild the block.

To accomplish a zero deck clearance use pistons from a 255 V8 and deck the top of the block to zero. You must measure the block with the new pistons for accuracy. The 255 V8 pistons have a pin height that is .085" taller than the 200/250 pistons. This step resolves both the deck height and the low compression problem. Be sure to use washers under the head bolts to keep them from bottoming out in their holes.

There are some other ways to accomplish zero deck height, but they are either more expensive or involve parts swapping/modifications.

The best cam, with a stock C4 may be the dual pattern ARC- 268/274 from FSPP. It will maintain good vacuum and idle quality, yet broaden the useful rpm range. It will also bleed off some cylinder pressure to resist detonation.

Depending on the head casting, your '75 may or may not have the 1.75" intake valves and hardened seats. It will, at least, have induction hardened seats on the exhaust. If you go for a zero deck height, do not mill the head anymore than necessary to create a flat mating surface.

That's my two cents, for what it's worth.

Adios, David

 

[Anonymous]

Howdy Slick and All:


It would be helpful if you would post the casting code for the head and block, as well as the carb and distributor.

If you do plan to rebuild the block there are several economical steps that can be taken that would make for a better, more durable, more powerful engine. I'm confused though. In your intro you said you were going to rebuild the head and shortblock, but later you said you didn't want to put "That much" into it. It costs no more to do the block right, if you're going to rebuild the block.

Thanks for all the info......

Not spending too much was just in referance to getting an aluminum head.

As far as those casting numbers on the head and block, do you have a location where they hid those?
To read the numbers on the 170's head I had to take a yoga class and I still got stuck in the engine bay.
Tonight after the kids go to bed I'm going to start pulling all the hoses and crap to see what's actually under the hood. I'll let you guy know what I find.

 

[CZLN6]

Howdy Back:

The head code is on top of the log, behind the carb. The block code is on the side, under the exhaust manifold.

Enjoy the journey.

Adios, David

 

[Anonymous]

Ummmm, yeah, thanks David.
I attacked it last night. With all the lines from the A/C, vacuum, and smog it was like opening a panel on the space shuttle.
I did see the last part if the numbers on that intake log, but the rest are covered buy the kickdown bracket, which is allen screwed to the bottom of the exhaust and blocked by a bunch of smog lines.
I got out the die grinder to start cutting away at it, but it was way to late to make that kind of noise.

I did get that carb off, how can I I.D. the thing. I didn't see anything that said RBS, YF or YFA.
There is a Motorcraft tag with the numbers D-5PE ATA F 6 L 4
and stamped on the side just above the throtle body are the numbers 7127 S
I did a Google search but with no luck.

That dizzy looks like an average size cap, but it is pointless.

 

[Anonymous]

Hey Slickmofo,
Not to belabor the point, but I have learned a lot from buying David's book,
Falcon Performance Handbook. It is well worth the money.
Ken

 

[Anonymous]

Hey Slickmofo,
Not to belabor the point, but I have learned a lot from buying David's book,
Falcon Performance Handbook. It is well worth the money.
Ken

Thanks Ken, I'll look into finding it.

 

[Anonymous]

Numbers on that intake log D5DE-6090-BA

Numbers on block
D5DE
6015-AA

 

[CZLN6]

Howdy back Slick:

Your D5DE-6090-BA head is most likely a flat-topped log with a 1.75" carb hole. It will most likely not have the largest intake valves. It will also have the larger 62 cc chambers to get it down to 8.0:1. Most likely the intake valves will be 1.69" diameter. The D8 and later heads have a 1.75" intake. The head may have valve seat inserts- at the least they will be induction hardened.

The head, in your case could benefit from an upgrade to 1.75" intake valves. Add a three angle valve job, back cut the intakes, find a pre-'65 adjustible rocker arm assembly. You'll need longer pushrods, but the adjustibility is worth the trouble.

The block is a good place to start, but be sure to get cam gear from the '69 - '71.

IF the carb has the float bowl sitting out toward the front it is likely an RBS. Spray down the outside with some carb cleaner for more markings. Look for a "4980" stamped on the base on the inside, linkage side. The tag is the FoMoCo.

Keep us posted on your plan.

Adios, David

 

[mugsy]

Here was my "game-plan":

1) Build the short block/bottom end for durability. There is very little power to be found in the short block. Other than the quench height previously mentioned, go for good, basic machine work. Don't go overboarded with H-beam rods, forged pistons, etc. Just worry about the tolerances and the basic machining.

2) Remember the 3 C's of Power: Carb, Camshaft and Compression. Upgrade the carb to either a 2V or larger 1-bbl. Also go with the cam recommended above. And finally, measure, don't guess, the volumes and go with the a high 9.X:1 compression ratio. Please don't ask "how much should I tell the machinist to mill off the head" etc... Determine the deck height, buy and measure the head gasket and then cc the combustion chambers. There are compression ratio calculators out on the web. I was lucky, my machinist let me cc the head in the mill as he was milling it. I had a target volume, and I was able to verify that it was done right.

3) Install headers and a larger diameter exhaust system.

4) Lastly, upgrade the ignition. Go with either a revised advance curve on your DuraSpark II or buy Mike's DUI HEI upgrade. I think there is a sticky on re-curving the DS-II. Or drop the bucks and go with the HEI unit.

 

[Anonymous]

Hey Powerband,
Have you raced your Comet in a QT Mile? If so, what are your times and speed? I am looking for some insperation.
Thanks,
Ken