Cracked head. Is this a problem?

G

groomerguy

Active member
I finally got the trail groomer over to my shop to begin the work. We planned to do a valve job this year. It's a 1969 250 and probably original so I suppose it's due.
First I tried to fit the header up. It was a shot in the dark if it would fit or not. It wasn't made for this type of machine. It doesn't but I'm still hoping for a solution for that.
Next I got the head off and could see a small crack in the roof of the exhaust port that goes through to the floor of the intake. Once I chipped away the carbon on the floor if the intake I could spray some carb cleaner in there and see it weep through into the exhaust port. With the port divider fitted the crack is covered.
Does this crack junk the head? If so where can I find another? Will a head from a 200 fit it or does it need to be from a 250?
When I got the head off it had a FelPro head gasket in there so it must have been apart at some point in the past. The gasket was .040" compressed thickness.
Any advice or help would be appreciated.
Thanks!
Mel
 
Do a search on the port divider. There are several posts on what will & will not work with PD. Sounds to me like you have the best reason on the board for installing the PD permanently. :wink:
 
Howdy Mel:

If it was me, I would not trust a head with a crack in it. If you can see one, there's likely to be more. IF you're going to invest time and money in r&r of a head it is wise to be sure that what you're working on is sound.

Any late model 200 head will interchange with no problem. A '78 and later head will also have hardened valves seats to begin with, and a larger intake valve. I would have the new head milled .030" to be sure it is true and to regain some of the original CR. Check the piston height while the head is off an let me know. I'll run some ratio numbers for you.

Take your time to fit the port divider tight and be sure to weld it in as per the directions.

Adios, David
 
Thanks for the replies. Late model 200 head means what years?
If the head will be an issue with this crack then I'll certainly replace it.
If I could figure out how to post pictures I'd show you what the plugs looked like. Never seen them like this before. The massive carbon build up that in some cases is formed out to the side like it's blowing in the wind. I've seen the build up on plugs before but this is white, not black or brown.
The carb is off an 86 F-150 with a 300. I rebuilt it but didn't do any jetting. I can't believe it'd be that lean but maybe so.
I'll get the piston depth number today. They stop short of the deck surface by quite a distance.
Thanks for the help.
Mel
 
Howdy Back:

Late model means a D7xx or later. 1977 Fairmonts and Zephyrs are good donors. Also Granadas and Monarchs. A '75 or '76 casting may have hardened seats also, but no guarentee as these were change over years. 1977 and on are a fairly sure thing.

A carb of of an '86 300 should have a richer A/F curve. The buildup may be a gas additive?? Do you get it in other carbureted engines in your area?

Adios, David
 
David,
I measured the piston depth in the cylinder. It sits .155" down into the bore. It has a slight dish, not much.
The info on what donors are best is helpful. I'll be talking with a friend today who knows a guy who might have something that will work.
I could send you pics of the plugs and unit if you want.
I don't see that sort of buildup on plugs in other engines around here. It is very strange.
Mel
 
David,
One more item in the mix. Our snowmobile club purchased this unit from the State back in the early 90's. It had not been used by them for many years and had trees and such growing up though it's tracks and frame. iT was in very poor shape.
In looking at the block and head numbers, and comparing them to your book, this must be a 1975 engine even though the unit is a 1969 model year.
The block number is D5DE-6015-AA and the head number is D3DE-6090-AA.
My info is this is an Industrial Engine. The valve cover says 250. It does has 4 water pump mounting bolts so it must be - right?
In your opinion is this a 1975 engine? Are there any other ways I can make sure?
If it is a 1975 engine then the original engine must have been replaced at some point.
Mel
 
If the casting number says D5, it is indeed a 1975 casting. The head is from 73. It sounds like a 250 to me with the four water pump bolts--the 200 only has three.
 
Howdy:

All indications are "yes, it is a 250". Just for kicks, check the stroke, as long as the head is already off. a 250s stroke is almost 4" @ 3.91". A 200 measures 3.126. It is an obvious difference.

Your engine at .155" deck height, .040" gasket, assuming a standard bore and an unmilled head at 62 cc chambers, figured out to a compression ratio of 7.6:1.

Clean the top of a couple of pistons to verify if it had previously been rebuilt. If the pistons are oversize the amount will be stamped on the top of each piston.

Assuming a standard bore, .155" deck height, a new Felpro gasket at .050", a '77 or later head milled .050" to achieve 52 cc chamber volume- the new CR would be 8.1:1. While 8.1 is on the low side for performance it may be just about right for this engines application. Using 81 octane regular, unleaded gas, and a moderate ignition curve, you will not likely have any problems with pre-ignition or heating. I don't recall what ignition you are using on this engine, but an upgrade to an electronic unit would be a good idea. A 1975 engine could have had a DuraSpark, which is fine.

The curse of the 250 is/was its huge deck height. That acounted for its tendency to knock. Partly due to no quench on compression making for poor combustion efficiency. This also contributed to a tendency to allow carbon build up in the chambers, allowing hot spot and pre-ignition.

You would be wise to thoroughly clean any carbon buildup off the piston tops, and spend some time smoothing the chambers rougher cast surfaces.

The valve job gasket kit will include a set of valve stem seals. Be sure to use them. It is likely that some of the contamination build-up on the old plugs was from oil.

Consider having a three angle valve seat and having the intake valves back-cut with a 30 degree cut on top of the 45. These procedures will increase flow from Idle to redline. We don't reccomend back-cutting the exhaust valves because of the heat they deal with.

Adios, David
 
I checked the stroke. It's 3.90 or so. Definately a 250 engine. The bore measures 3.680 so it's stock.
There was a large amount of carbon between the piston tops and the head. No squish will do that.
I'm waiting on word if a head is available from a friend. If not I don't know what to do. I guess start calling around to junk yards.
I know about smoothing out the chambers and the 3 angle valve job. This unit isn't about performance. It just plods along at 2000 to 2500 RPM in 2nd gear on the early model C4 tranny. That's about 5 mph they way it's geared. A pretty exciting ride......
I installed a Pertronix conversion about 4 years ago. It runs great now.

I'll post again when I get more info.
Thanks!
Mel
 
David,
We picked up a head over the weekend. It's from a 1982 Cougar. The exhaust manifold has an enormous outlet on it. Must be 6" in diameter! Must be for EGR or a cat or something. I didn't see the car it came off of. We got the head, carb, valve cover, bolts and exhaust manifold for $125! Not a bad deal.
I plan to install the port divider but this head has the ribs on the roof of the exhaust port ending about 1/4" short of the gasket surface. Do I fit it to the end of the ribs or the gasket surface?
Our old exhaust manifold is warped some. I can mill that and reuse it but should I use the newer manifold?
It doesn't look like the right setup. I'd think the exhaust flow would slow down a bunch when it hit that huge cavity before funneling down into the pipe. That and I'd have to get creative to make an adapter to size it down.
I plan to have the machine shop deck this head 0.040" and just touch the valves and seats. The head is supposed to have just 33,000 miles on it.
I also plan to upgrade our unit and use this newer carb. Any opinion on that? I had replaced the original 1969 carb with one from a 1986 F-150 truck with a 300 in it. It runs better than before. Would this 82 car carb make any difference? Better? Worse?
Thanks for the advice.
Mel
 
Howdy Back Mel:

Definitely use your original exhaust manifold. The '82 quick burn cat unit is not one of Ford's better ideas.

My suggestion for rebuilding the head will aid and add flow and torque throught the rpm range- even the "Plodding" speeds. That is particularly true of back-cutting the intakes. Their greatest gain will be in the lowest valve lift.

On the port divider- fit it before you have the head refreshed. If the divider is fitted tightly and still protrudes, have the machinist weld it in and then mill it off smooth along with the exhaust manifold mating surfaces- both head and manifold. This will ensure a permanent and tight seal.

I'll run the numbers on CR with a .040" cut on the E0xx head for you. What head gasket are you using?

The '82 carb will be a Holley #1946. It is a very encumbered carb for the EPA requirements of that time. IT is a complex one barrel. I've never seen an official OEM cfm rating on these carbs, but by comparison of throttle bore, venturi and all else my estimate is in the 180 cfm range. The down-side is that the low speed air screw is sealed and preset by the factory. IF it is a good running carb, it will likely run leaner/cleaner then your 300 carb- but probably down on top-end power. I'd be inclined to clean it up and try it. At your rpm range, the loss of power may not matter and a little more economy should make the club bean counters happy.

Adios, David
 
David,
I dropped the head off at the machine shop today. I got the port divider fitted really well. They'll weld and machine smooth.
I also asked them to cut .035" to .040" off the head gasket surface. They said they never take more than .010" to clean them up. There are water ports adjacent to the head gasket and that as the head is shaved the port widens and you run the risk of a future leak.
I can't see any difference between our old 1973 head and the 1980 head. It does have a E0 casting number. I'm trusting that .035" or so is the right thing to do.
They will also mill our exhaust manifold to get it straight. It has a couple of small cracks trying to start and they'll weld them and build up and out the gasket sealing flange along the top of the center port. Matching the gasket up to it I can see only half the gasket is on the exhaust manifold so it probably didn't want to seal too good from the start.
The head gasket is from NAPA. I suspect it'll crush down like the FelPro one.
Ah the carb issue. I just love it when they "seal" an adjuster from the factory. That makes it a challange to undo their best intentions. Seriously, I'll look at using that carb. Fuel economy and torque are at the top of the list. I don't mind all the extra junk on it.
There is a club to our west with a unit just like ours and they need a good carb setup. If I use the newer carb I'll probably donate ours to them.
I also have the rocker shaft from the 200 engine. Is it the same as the one I have from our 250? If so, I may use the newer one since it will be fresher. I'll still take it all apart and clean per the book, I just think it'll be a bit cleaner to start with.
Thanks for all the info. Your continued help is making this an easy job.
Mel
 
Howdy Back Mel:

The head can easily and safely be milled up to .090". Even though these are "Thin Casting" head and block, there is plenty of meat. The standard cleanup cut on a valve job is .010" or just enough to clean up and true. The difference here is that the stock OEM head gasket was .025" crushed thickness. The gasket you'll be using, assuming NAPA still sells Victor, will be .045" crushed thickness. THe new gaskets seal much better then the stock steel shim type too. The Victor (NAPA) gaskets typically crush to .045" while the FelPro measure .055".

Given a Victor head gasket at .045" and a mill cut of .035" will yeild a CR of aproximately 8:1. That should be very safe in your application.

The "E0" castings first appeared in the 1980 model year and was the last commonly found casting on all eighties engines.

THe later rockers should be fine. Look them over carefully. Especially the ball ends of the pushrods. IF the rockers have not been getting properly oiled the ball ends are the first place it shows up. THe next area is the botton of the rocker shaft where each rocker rotates. The oil gets to the front rockers last and is usually the most likely place for wear.

Keep us posted on how it comes along.

Adios, David
 
David,
Got the head back from the machine shop. It looks good. He told be the first pass on the surface planer just touched the two ends of the head about 1" in from the ends. Apparently the head had a pretty good bow in it. The middle was low (high on the engine). He took nearly .025" off before it cleaned the entire surface. I guess the end cylinders will have a touch more compression than the middle. Nothing I can do now.
The port divider look good and he planed the exhaust manifold and head surface.
More to come after Saturday. That's when I start putting it together.
Any spark plug preference? Timing recomendation? I guess I should go back and reread the book again. Lots of great info in there!
Have a great weekend!
Mel
 
Howdy Mell:

At 8:1 a little CR variance from cylinder to cylinder will not be an issue.

On timing and plug heat range, my guess is about 12 to 15 Btc initial and Motorcraft 45 or 46, depending on many of your circumstances. Read the plugs. where you're doing mostly steady speeds I'd be inclined to try to tune the carb for max vacuum and initial spark setting while in operation under load and at work speed. It will be a two man job, but may be worth it in economy and efficiency.

At 2200 to 2400 rpms you will be at a steady speed so should be able to use a vacuum guage to fine tune the low speed air screw, which will be at the upper end of its range (You may or may not see any difference depending on the carb you use), and the initial advance setting. While the centrifugal advance will have kicked in at a steady speed it can still be assessed with a vacuum gauge. Hook the vacuum gauge to a full manifold vacuum source, do the carb first, trying for the highest steady vacuum reading, then the initial, again, trying for the highest vacuum reading. Be sure to disconnect the vacuum advance line to the distributor and plug it. Be sure to reconnect when you're done.

Once your satisfied, run with this setting for at least a half an hour with a new set of spark plugs. Longer is better. After that run pull the plugs and check for color. Too white, glazed, or peppered- reduce advance, try a colder heat range plug, or richen A/F mixiture. Too dark- try a hotter heat range plug, more advance (Warning- anything past about 16 degrees initial will only generate more heat), or richen the A/F mixture.

Keep us posted.

Adios, David
 
Howdy Mell:

At 8:1 a little CR variance from cylinder to cylinder will not be an issue.

On timing and plug heat range, my guess is about 12 to 15 Btc initial and Motorcraft 45 or 46, depending on many of your circumstances. Read the plugs. where you're doing mostly steady speeds I'd be inclined to try to tune the carb for max vacuum and initial spark setting while in operation under load and at work speed. It will be a two man job, but may be worth it in economy and efficiency.

At 2200 to 2400 rpms you will be at a steady speed so should be able to use a vacuum guage to fine tune the low speed air screw, which will be at the upper end of its range (You may or may not see any difference depending on the carb you use), and the initial advance setting. While the centrifugal advance will have kicked in at a steady speed it can still be assessed with a vacuum gauge. Hook the vacuum gauge to a full manifold vacuum source, do the carb first, trying for the highest steady vacuum reading, then the initial, again, trying for the highest vacuum reading. Be sure to disconnect the vacuum advance line to the distributor and plug it. Be sure to reconnect when you're done.

Once your satisfied, run with this setting for at least a half an hour with a new set of spark plugs. Longer is better. After that run pull the plugs and check for color. Too white, glazed, or peppered- reduce advance, try a colder heat range plug, or richen A/F mixiture. Too dark- try a hotter heat range plug, more advance (Warning- anything past about 16 degrees initial will only generate more heat), or richen the A/F mixture.

Keep us posted.

Adios, David
 
David,
I got the head head back on and almost ready to fire it up. I'm staying with the carb from the 300. The new one meant I'd have to goof around with linkages and I'm too far behind to do that. Maybe next year.
I matched the ports to the gasket on both the head and manifold. They were pretty messed up. Worse than most I've seen.
I plan to weld a bung into the exhaust pipe just below the manifold and use my Innovate A/F meter for fine tuning. It's a bunch quicker than reading plugs.
I'll start with 10* initial and see how it runs and what my burn is like on the gauge. With all the racket in the cab I don't want to get into the detonation range and not hear it.
I'm getting very close. The next two weekends are booked for me with trail work and a trip I have to take so it might be October before I get it going.
Stay tuned.
Mel
 
A late season update. I slightly ported the head and manifold before installing it mainly to just match the ports.
The engine is running perfect. Smooth as silk. Throttle response is greatly improved.
With about 80 hours on the engine the plugs look perfect. A light tan and very clean. Running at a steady 2000-2500 under the load of pulling the drag through the snow it uses about 2.6 gallon of fuel per hour. I suspect that would be in the mid 20's MPG range if it was in a car.
Thanks to all those on this site who offered advice and help.
Next summer I'll fabricate a header for it since the one I bought that was listed as fitting a 250 has no chance in heck of actually fitting a 250. Live and learn I guess.
Anyone interested in a "new in box" header for a 200?
Mel
 
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