More 250 Head Questions

[Anonymous]

Trying not to overhash this head topic too much, but I've looked around for two days now and can't quite find what I'm looking for. I'm new here and have really enjoyed reading all the old discussions. This seems to be a really neat and informed bunch of guys. OK, here's my questions. I recently picked up an old Comet GT with the 250 six in it only the car has a crunched or broken cam gear in it. So I went down to the local police auction and picked up a '76 maverick also with a 250 in it. My original intent was to pull out the '76 250 and drop it in the '71. After poping the hood on the '76 I'm finding that this car has reached the emmision age. So my thinking is to loose all the emmision gear. I've also read that the '71 has a higher compression ratio. So now my thinking is to use the '71 head, log and carb on the '76 block. So the qustion is will I gain the compresion from the '71 by putting the '71 head on the '76 block. A couple other questions. Does the cam from the '76 have the same specs as the '71. Maybe I should just swap out the cam? One more question. I want to start up the Mav before I pull the engine. No keys though. I thought a wire from the pos. side of the battery to the pos side of the coil would do the trick, but I can't seem to get ignition doing this. How do I hot wire the Mav? I've pretty much trashed the locking mechanism on the stearing column already. Still can't get it to turn on. Any help on any of this would surely be appreciated. Thanks and talk to ya soon.
Speedy

 

[Anonymous]

what i would have done is just bought a new cam, you can get one for $115 on here and be better than stock, im sure that is less than the cost of that car

 

[Anonymous]

Well the car was $150. It has plenty of parts that can be used to upgrade the comet. Like front disk brakes. The original idea though was to just pop out the engine and drop it in the comet. Now that I have it home I'm just thinking what will be the best combo prior to putting it back in the car.

 

[CZLN6]

Howdy Speedy:

Look for a casting # on each head to determine which heads you have. It will be on top on the intake log behind the carb. There will be subtle differences between a '71 head and a '76. It is the 1st two # that are critical. The '71 will likely have a C9XX, or a D0XX. Either could have the disireable flat-top log manifold. THe C9 could have either a 1.5" or 1.75 carb hole, it will have a 1.69"intake valve and no hard valve seats, it could have a 52cc or a 62cc chamber. Either head can be milled to achieve your desired CR.

The D5 head will have a 1.75" carb hole, probably induction hardened seats, It could have 1.75" intake valves (D5 heads were a transition time, some early heads have 1.69, while later heads have 1.75" intake valves), it will likely have the 62cc chambers.

If either is a flat-top log head, that's the one I'd use and upgrade to a large carb hole, 1.75" intake valves, hard seats, and a smaller chamber to meet you CR goal.

Don't bother swapping an old, used cam and/or gear. You didn't say what trans your planning on, but a new 260 to 268 degree cam with new lifters and timing gear set will be the way to go.

Save the engine mounts on both sides- frame to rubber insolators and rubber to engine. These mounts are unique to 250 installs. No telling which you'll need. Also check over the pans and pulley systems for comparison in the swap.

Keep and adapt the electronic ignition from the '76 to the final engine.

Sorry, I can't help you with the hot-wire, but it is a worthy goal to get the '76 engine running now to assess it before installing in the Comet. If you have to doe engine work before installing please get back to me for some critical options to improve the bottom end and match a good USA head combo.

Adios, David

 

[Anonymous]

David,
Now that's the kind of info I've been looking for. I'll check out the numbers on the logs and get back with you. Hopefully I'll have the 1.75 hole and the 52cc chamber. You also touched on the other thing I was looking into and that's the electronic ignition in the '76. I noticed that the newer car did not have points and I was thinking the same thing. Is there an ignition box or anything, or is it just a distributor and coil? I lucked into the '71 Comet. Found it in the Thrifty Nickle and the guys mom was wanting it out of her yard. It's a one owner with original paint and straight body. The guy said it had a thrown rod but after checking it out I found it to be a cam gear. Paid a whole $350 for it. It's bright yellow with black accent stripes, hood scoop and bucket seats. I can hardly wait to get her running. Oh, It has an automatic in it. Thanks,
Also Dave

 

[Anonymous]

OK, I have the numbers off the '71 engine. The numbers I found on the log are: C9DE-6090-M. I can't see the numbers on the '76 due to everything still being hooked up. Visually the two logs look to be pretty much the same. They do have different carbs though. I'll know more after I get them both off. Any preference on which carb to use?

 

[FastRonald]

8) Take a wire and run it from the Positive side of the battery to the Positive side of the coil. Now either use a bump switch or a screw driver and jump from the terminals on the solonoid. Should start

 

[Anonymous]

Hey FastRonald,
I appreciate the info. That's what I thought and that's what I was doing but I still wasn't getting any spark. Like the ignition switch isn't turned on. I'm not sure if it's because it's electronic ignition or what, but I gave up on it. The motors coming out. Just as well. While removing everything I found a lot of corodid and brittle wires and connections. I'm pretty confident I'll get it going after I put everything back together right. Thanks for your help. I'm still interested in any head specific information by year though. Thanks again and talk to ya later.
Dave

 

[CZLN6]

Howdy Again Speedy:

Wow! you are speedy. The C9-M head is probably the preferred head for a performance 250 because it has the largest log and intake port volume of any small six head. It does not have hard seats and it does have 1.69" intake valves. D7 and later heads will have 1.76" intake valves and hard valve seats. Some D5 castings have the good stuff too, but this was a transition year for FoMoCo. It's an even bet that your '76 Maverick will have either a D5 or D7 casting and either a flat-top or hex shaped intake log. The difference is the width of the flat top surface. The flat top log has about a 1 1/2" flat surface, the hex log, only about 1/2". If the '76 has a D7 casting and a flat top then it's the one and you're ready to go. If not then we'll assess what you do have and mix and match to get the best.

The ignition system includes the large cap distributor, spark plug wires, coil, module and the wiring harness to connect the three pieces and to the switched power source. The module is usually mounted on the inner fender with two screws. Keep as much of the wiring harness intact and track hot wires to there source, and take as much as possible. Jack (Web site creator and host) has a chart/graph/illustration as to how to wire the DuraSparkII system into a pre DSII engine posted somewhere here.

I'm surprised that the carbs are not the same. The Carter RBS were, supposedly, used on 250's from 1970 to the 1978. Who knows what might have happened in the last 28 years since the Maverick was new! the Holley #1940 was a common universal FoMoCo replacement carb, of questionable merit.

The RBS is a good carb when working properly. But, this is a good time for you to sit down and assess your goals for this vehicle and create a plan, with a budget and a time line. Carb choices, CR and cam are critical components that must be planned for and coordinated for best results.

Again, Let me repeat- Carefully compare and check out the engine mounts- both frame to rubber and rubber to engine, for differences. Also check out the pulley system and pans on both vehicles.

Keep us posted.

Adios, David

 

[Anonymous]

cool a nother maverick and comet on the forum 8)

 

[Anonymous]

Hello again David and '76Mav,
I've got more numbers to crunch. I stayed up last night and got the engine out of the '76. Yea it was a pain. Really not that bad, but it was the first time with one of these. I think I'll be able to cut the time in half when I yank the Comet engine. The intake logs on both these engines look to be about the same with the exception of the plates mounted underneith the carbs. On the '76 there's a plate that has a line that goes to the exhaust manifold. On the '71 the line goes into the valve cover. The '76 just has way more emmisions. Anyway, here's the numbers. Some of these were hard to read so they may be off a little bit...

On the '71 Comet:

Intake log - C9DE-6090-M
Exhaust - C6DE-94?C-A
Block - C9DE
8015-B
Carb - Carter 0-2185
Model RBS
Autolite DIZF KA
VIN# 6K92LI07522
---------------------------------------
On the '76 Mav:

Intake log - 5H25
D5DE-6090 BA
Exhaust - 10 5H20
D6BE-9430-AA
Block - 6015-AB
DX 9
Carb - Carter Remanufactured by Holley 987247
0690
64-1103
VIN# 6K92LI07522
-----------------------------------------------------------------
Allright guys. What do you think I have or how do you think we should proceed? I'll know once I get these things taken apart but it sure is cool having you guys describe the differences between the engines and cars. Also, the '76 Mav is FOR SALE should ya'll know anyone looking for fenders or parts. That is after I find out about the rear end on it. I'm thinking I will only do the disk brake swap if the rear end is worthy of a rear end swap. To get five lug wheels, can I just pull the axles? I mean, five lug wheels would be cool if I got a nine inch rear end to go with them. On the other hand I'm thinking four lug wheels is cool too. Kind of like a six banger is cool. You guys following me? I'll quit rambling now. Ya'll may speak now. Thanks for your help.
Dave

 

[Anonymous]

The Carter RBS was only used from 1970-1974. After that, Ford switched to the Carter YF/YFA.

 

[Anonymous]

do a google search on maverick forums (I lost the home page link to the one I`m on :roll: ) and post that in the for sale forum you should be rid of it pretty quick

 

[CZLN6]

Howdy Speedy:

Sorry to be so long in responding. I've been off to the wilds of Idaho for a few days. Here's what you will likely have;

The D5XX-AA head will likely have a 1.75" carb hole and a Carter YF carb. C5 was a transition year for cylinder heads. It has been our experience that the AA head will likely have 1.69" intakes and posibly induction hardened valve seats on the exhaust side only. A D5XX-BA usually have 1.75 intakes and induction hardened seats on the exhaust. All BA suffex heads we've seen have been flat-topped log manifolds.

If your D5XX-AA head has 1.75" intake valves, please let me know. It will be a first. But, it would not surprise me. D5 is a transition casting #. Strange things happen in transition years.

Under any circumstances, IIWIYS, I'd use a flat-topped log head, we know the C9XX is. I'd upgrade to 1.75" intakes, install hard valve seats, Have a three angle valve job, back cut the intakes, install an exhaust port divider, and mill to achieve your compression ratio goal. If you want to go the extra mile, polish the chambers and smooth any transitions in the bowl area of the intake port. Round the right angle transition under the carb pad to either direction into the log.

Let me know what your plan is for the block before we talk about your CR goal and head milling.

If you're going to rebuild the block, check both for previous overbores and use the freshest. Overbore pistons will have the overbore amount stamped on the top of the piston. Let me know if you plan to do the block. You have good options.

Did you check the engine mounts for differences between the two rigs? Any? I would be very interested in the Mounts you do not use. Both frame to rubber and rubber to engine.

Keep us posted.

Adios, David