Got my 250!

[62Ranchero200]

Greetings Ford Six Fans,

To provide a brief background, the 200 in my Ranchero now has excessive blow-by and needs to be rebuilt. However, to MAXIMIZE my ford six performance, I wanted to find a 250 to build for the Ranchero.

I found a 250 with a C-4 flexplate in Houston's craigslist (the Ranchero already has a C-4). According to the owner, the 250 was pulled out of a '74 Maverick with 45,000 miles that had been totaled by a front end collision. The 250 was delivered Saturday morning and I already have it almost down to the short block (still need to get the balancer off).









My basic idea is to have it cleaned up, checked for crank / rod / block cracks or other damage, then put back together with ARP main and head studs, ARP rod bolts, a static and dynamic balance, and new flattop pistons (either cast or forged, thinking about that one). Then, I can put the rebuilt head, Autolite 2100 carb, and DUI ignition I already have on the 250 short block. Will need to get a SBF bellhousing, starter, and (I think) a different torque converter. May spring for some long-tube headers while I am at it.

I am going to have LOTS of 250 questions!

Bob the Builder

 

[FalconSedanDelivery]

Don't waste your money on a DUI , use a Duraspark I or II, or just add a pertronix conversion along with a recurve to the Dist in the 250 , If you had no dist it might be an option , but they are Way overpriced and have their problems

 

[62Ranchero200]

Greetings Ford Six Fans,

My basic idea is to have it cleaned up, checked for crank / rod / block cracks or other damage, then put back together with ARP main and head studs, ARP rod bolts, a static and dynamic balance, and new flattop pistons (either cast or forged, thinking about that one). Then, I can put the rebuilt head, Autolite 2100 carb, and DUI ignition I already have on the 250 short block. Will need to get a SBF bellhousing, starter, and (I think) a different torque converter. May spring for some long-tube headers while I am at it.

Bob the Builder

I've been readings posts about 250 for about a year on this forum, and I've already read the Ford Falcon Six Handbook from cover to cover a few times. Those of you who are familiar with both 200's and 250's please correct the below.

200 parts not compatible with a 250

pushrods (250 pushrods are longer)
timing set (read somewhere that advancing or retarding cam was in the crank gear)
timing cover? (250 block is wider)
harmonic balancer
water pump (250 water pump has four bolts, 200 three bolts)
water pump pulley
oil pan (250 block is wider)
crankshaft (250 has longer stroke)
connecting rods (250 has longer stroke)
starter
flexplate
bellhousing (SBF)
motor mounts

200 parts compatible with a 250

distributor & ignition (including coil, ignition module, etc.)
head (including carburetor, headers, etc.)
pistons (same 3.68" bore and compression height)
camshaft
lifters
rocker arm assembly

Thank you,
Bob the Builder

 

[bmbm40]

Congratulations on your 250. I think your list is accurate on the parts. If you replace the pistons have you considered a mild cam? From what i have read it is one of the best performance mods and relatively inexpensive if you block is out and disassembled. Can't wait to see how it works out.

 

[62Ranchero200]

Congratulations on your 250. I think your list is accurate on the parts. If you replace the pistons have you considered a mild cam? From what i have read it is one of the best performance mods and relatively inexpensive if you block is out and disassembled. Can't wait to see how it works out.

I put a Clay Smith 264H/110 cam in my 200 last winter, and have driven few miles since - it should still be almost new, so I should be able to take it out of the 200 and put it into the 250, right?

As I understand it, the long crankshaft and cast connecting rods make the 250 RPM-limited. I don't ever expect to set up a turbo or supercharger, nor nitrous oxide. Although I may take the Ranchero to the strip a time or two to see what in runs in the quarter mile, I don't expect to run it over 5,000 RPM. In these circumstances, how much of an advantage do forged pistons offer for the extra $550?

Thanks
Bob the Builder

 

[bubba22349]

Right cam will swap into your new 250 block I would guess that the lifters were new with the cam. If you keep them in order so they go back on the same cam lobe it will work out fine. For the use you are planing cast pistons will work great.

 

[xctasy]

Greetings Ford Six Fans,

My basic idea is to have it cleaned up, checked for crank / rod / block cracks or other damage, then put back together with ARP main and head studs, ARP rod bolts, a static and dynamic balance, and new flattop pistons (either cast or forged, thinking about that one). Then, I can put the rebuilt head, Autolite 2100 carb, and DUI ignition I already have on the 250 short block. Will need to get a SBF bellhousing, starter, and (I think) a different torque converter. May spring for some long-tube headers while I am at it.

Bob the Builder

I've been readings posts about 250 for about a year on this forum, and I've already read the Ford Falcon Six Handbook from cover to cover a few times. Those of you who are familiar with both 200's and 250's please correct the below.

200 parts not compatible with a 250

pushrods (250 pushrods are longer, right?)
timing set (read somewhere that advancing or retarding cam was in the crank gear?)
timing cover? (250 block is wider, right)
harmonic balancer
water pump (250 water pump has four bolts, 200 three bolts)
water pump pulley
oil pan (if 250 block is wider, oil pan would be different too)
crankshaft (250 has longer stroke)
connecting rods (250 has longer stroke)
starter
flexplate
bellhousing (SBF)
motor mounts

200 parts compatible with a 250

distributor & ignition (including coil, ignition module, etc.)
head (including carburetor, headers, etc.)
pistons? (same 3.68" bore, right?)
camshaft
lifters
rocker arm assembly

Thank you,
Bob the Builder

Bob the builder/


You might have three options to consider if you've got the early 1962 close coupled firewall, which isn't big I6 compatible.

(The early 62 firewall won't clear the 157, 160 or 164 teeth bellhousing that can be bolted to the stock 1965 onwards six bolt Small Block Ford bellhousing. The XK 2000 platform wasn't the same as the mid 1962 revision. About that time, Ford brought out running changes in preperation to fitting the 221/260 engines for the Sprint and the stock Unibody Fairlane Compact. The centre trans tunnel was common to both the Unibody Fairlane and the 1962.5 Falcon.)

If its early 62, your 'Chero might require oxy actetalyne and 10 pound sledge hammer work to fit the SBF size transmission.

If you don't like that, a second option (option two) so you can fit the transmission and six bolts into the firewall area so you can remove the trans in an emmergecy, then you'll have to track down a 1976 to 1978 Mustang II 302 V8 gearbox, starter and 141 tooth flexplate and seperator plate. If you get one of them, you then have to remove the 28 Ounce unbalance. Then you won't need to belt the bejesus out of the 1962 firewall.

Find a junked core from a Mustang II, get the trans plate and VIN number, and get a fully gautrenteed rebuild for 660 bucks. The parts are so cheap! Even the separator plate is just US $ 22.50, see http://www.ebay.com/itm/MUSTANG-II-C4-B ... 0822327528

The C4's are Ford best non overdrive trans, and the Mustang II bellhousing C4 is Fords best, and smallest C4 transmission. The M2 302 kicdown rod needs to be reworked, use the lokar kickdown cable and bracket and you won't look back.

See http://www.rebuilt-auto-transmissions.c ... 2108818.b6. If you've got a space problem, the M ii C4 is the best option because, if you can fit one behind a 351w and have it live, its perfect for a hot 250. See http://www.mustangii.net/351convert.asp

Option three, if sledge hammering and tracking down a Mustang II small 302 transmission isn't your idea of a good time, you'll have to use 138 teeth Cologne V6 transmission and an adaptor to suit the 4 or 5 speed auto or manuals they used. They will clear a smaller , early trans tunnel.

See viewtopic.php?f=76&t=68695

Thanks for the heads up

See viewtopic.php?f=3&t=67524&start=50#p523895

So is the 5r55 a five speed auto and will it bolt to the US 250? Are they available in the states? Is a controller required/ is it a realistic option?

So is the 5r55 a five speed auto

Yes

will it bolt to the US 250?

No, not without an adaptor

Are they available in the states?

Yes

Is a controller required

Yes

is it a realistic option?

Yes

The 5R55S used in the Aussie Falcon was the last of the Bordeux automatic transmissions, and is available ex Mustang (2005-2010 S197 Cologne V6 138 teeth flexplate) or Modular Romeo Windsor (2005-date 164 teeth new cammer bolt pattern), or later 2001 on Explorer/Ranger as a 5R55W in 138 tooth form for 4.0 Colognes. The 4.6 Explorers ran 164 teeth new cammer bolt pattern.

Since 2001, all 5R55 variants ran one piece casings, so no longer can post 2001 5R55 transmissions be converted to a different bellhousing adaptor.(See the Luiz Camilo adaptor below)

The Aussie 5r55 transmissions ran an early 289 style 160 tooth flexplate, and a unique case to suit the 1993 to 2012 I6 (E-series 4.0 sohc, A series Intec, or B and F series Barra).

But any 5r55 trans behind a 138 tooth Ranger, Explorer or Mustang with a Cologne V6 can be used to mate to it with a Luiz Camilo style adaptor.

I sent this to RickWrench about his Brazillian mate who used and perfected the kit back in the early Naughties

Way back, I remember your brilliant Brazillian friends Alfa Romeo GTV 5000 with 302 Small block Ford with a Cologne V6 gearbox adaptor plate, 138 tooth flywheel and its 5 speed gearbox mated up to down size the 141/148/157/164 tooth bellhousing enough to fit in the 1750 derived engine bay.

Done a heap of research, mixed and matched some photo's




and I'm gonna use the idea myself. I can ad lib it from here, but do you still have any contact with him, and if so, what thickness was used, and how does the little 138 flywheel mate to the 3" pitch 6 bolt 3.625" crank flange. Is he making a kit. If not, its a really good idea and would allow all the stronger 5r55 auto gearboxes to fit behind any 302 small block.

Best wishes,

Dean from New Zealand

 

[62Ranchero200]

Greetings Ford Six Fans,

My basic idea is to have it cleaned up, checked for crank / rod / block cracks or other damage, then put back together with ARP main and head studs, ARP rod bolts, a static and dynamic balance, and new flattop pistons (either cast or forged, thinking about that one). Then, I can put the rebuilt head, Autolite 2100 carb, and DUI ignition I already have on the 250 short block. Will need to get a SBF bellhousing, starter, and (I think) a different torque converter. May spring for some long-tube headers while I am at it.

Bob the Builder

I've been readings posts about 250 for about a year on this forum, and I've already read the Ford Falcon Six Handbook from cover to cover a few times. Those of you who are familiar with both 200's and 250's please correct the below.

200 parts not compatible with a 250

pushrods (250 pushrods are longer, right?)
timing set (read somewhere that advancing or retarding cam was in the crank gear?)
timing cover? (250 block is wider, right)
harmonic balancer
water pump (250 water pump has four bolts, 200 three bolts)
water pump pulley
oil pan (if 250 block is wider, oil pan would be different too)
crankshaft (250 has longer stroke)
connecting rods (250 has longer stroke)
starter
flexplate
bellhousing (SBF)
motor mounts

200 parts compatible with a 250

distributor & ignition (including coil, ignition module, etc.)
head (including carburetor, headers, etc.)
pistons? (same 3.68" bore, right?)
camshaft
lifters
rocker arm assembly

Thank you,
Bob the Builder

Bob the builder/


You might have three options to consider if you've got the early 1962 close coupled firewall, which isn't big I6 compatible.

(The early 62 firewall won't clear the 157, 160 or 164 teeth bellhousing that can be bolted to the stock 1965 onwards six bolt Small Block Ford bellhousing. The XK 2000 platform wasn't the same as the mid 1962 revision. About that time, Ford brought out running changes in preperation to fitting the 221/260 engines for the Sprint and the stock Unibody Fairlane Compact. The centre trans tunnel was common to both the Unibody Fairlane and the 1962.5 Falcon.)

If its early 62, your 'Chero might require oxy actetalyne and 10 pound sledge hammer work to fit the SBF size transmission.

If you don't like that, a second option (option two) so you can fit the transmission and six bolts into the firewall area so you can remove the trans in an emmergecy, then you'll have to track down a 1976 to 1978 Mustang II 302 V8 gearbox, starter and 141 tooth flexplate and seperator plate. If you get one of them, you then have to remove the 28 Ounce unbalance. Then you won't need to belt the bejesus out of the 1962 firewall.

Find a junked core from a Mustang II, get the trans plate and VIN number, and get a fully gautrenteed rebuild for 660 bucks. The parts are so cheap! Even the separator plate is just US $ 22.50, see http://www.ebay.com/itm/MUSTANG-II-C4-B ... 0822327528

The C4's are Ford best non overdrive trans, and the Mustang II bellhousing C4 is Fords best, and smallest C4 transmission. The M2 302 kicdown rod needs to be reworked, use the lokar kickdown cable and bracket and you won't look back.

See http://www.rebuilt-auto-transmissions.c ... 2108818.b6. If you've got a space problem, the M ii C4 is the best option because, if you can fit one behind a 351w and have it live, its perfect for a hot 250. See http://www.mustangii.net/351convert.asp

Option three, if sledge hammering and tracking down a Mustang II small 302 transmission isn't your idea of a good time, you'll have to use 138 teeth Cologne V6 transmission and an adaptor to suit the 4 or 5 speed auto or manuals they used. They will clear a smaller , early trans tunnel.

See viewtopic.php?f=76&t=68695

Thanks for the heads up

See viewtopic.php?f=3&t=67524&start=50#p523895

So is the 5r55 a five speed auto and will it bolt to the US 250? Are they available in the states? Is a controller required/ is it a realistic option?

So is the 5r55 a five speed auto

Yes

will it bolt to the US 250?

No, not without an adaptor

Are they available in the states?

Yes

Is a controller required

Yes

is it a realistic option?

Yes

The 5R55S used in the Aussie Falcon was the last of the Bordeux automatic transmissions, and is available ex Mustang (2005-2010 S197 Cologne V6 138 teeth flexplate) or Modular Romeo Windsor (2005-date 164 teeth new cammer bolt pattern), or later 2001 on Explorer/Ranger as a 5R55W in 138 tooth form for 4.0 Colognes. The 4.6 Explorers ran 164 teeth new cammer bolt pattern.

Since 2001, all 5R55 variants ran one piece casings, so no longer can post 2001 5R55 transmissions be converted to a different bellhousing adaptor.(See the Luiz Camilo adaptor below)

The Aussie 5r55 transmissions ran an early 289 style 160 tooth flexplate, and a unique case to suit the 1993 to 2012 I6 (E-series 4.0 sohc, A series Intec, or B and F series Barra).

But any 5r55 trans behind a 138 tooth Ranger, Explorer or Mustang with a Cologne V6 can be used to mate to it with a Luiz Camilo style adaptor.

I sent this to RickWrench about his Brazillian mate who used and perfected the kit back in the early Naughties

Way back, I remember your brilliant Brazillian friends Alfa Romeo GTV 5000 with 302 Small block Ford with a Cologne V6 gearbox adaptor plate, 138 tooth flywheel and its 5 speed gearbox mated up to down size the 141/148/157/164 tooth bellhousing enough to fit in the 1750 derived engine bay.

Done a heap of research, mixed and matched some photo's




and I'm gonna use the idea myself. I can ad lib it from here, but do you still have any contact with him, and if so, what thickness was used, and how does the little 138 flywheel mate to the 3" pitch 6 bolt 3.625" crank flange. Is he making a kit. If not, its a really good idea and would allow all the stronger 5r55 auto gearboxes to fit behind any 302 small block.

Best wishes,

Dean from New Zealand

Xctasy,

Thank you for the information about the SBF bellhousing / firewall clearance concerns.

Is there a measurement or any other way I can tell if I have an early "close coupled" or late '62 Ranchero firewall, other than finding a SBF bellhousing, bolting it to the transmission and seeing the interference? I already have a C4 in the Ranchero and it seems to have been rebuilt recently, so I would like to keep it and just change the bellhousing if possible.

I guess if "push came to shove" I might cut the firewall and put some kind of fire barrier material over the opening on the inside.

Thank you,
Bob

 

[Gene Fiore]

Bob, just a quick tip when you install the head studs. The front most passenger side stud goes into the water jacket and may hit the water pump impeller. You may need to grind off part of the stud for clearance. Many of us have had to do that. Just have the water pump installed first so you can turn it by hand. Then test fit the stud and turn the water pump by hand...if it is hitting you will hear it. Also you will need thread sealer on this stud so that water/anti-freeze won't seep up the threads. Happy building!

 

[CZLN6]

Howdy back Bob and All:

IIWIYS I'd seriously rethink using flat top pistons in a 250. The 250 has a serious tendency to knock. Dished piston are more knock resistant than flat topped. The performance cam will help by reducing cylinder pressure. IF you want more compression ratio (Who doesn't?) consider having the top of the block milled or "decked". That will reduce deck height and improve quench somewhat. What is your compression ratio goal with this engine?

If you were thinking of using the 255 V8 piston for an additional .085" of pin height, consider having the crowns milled with a "D" shaped dish mimicking the combustion chamber shape in the head. That, and decking the block will get you close to a zero deck height, which would be ideal with a composite type head gasket. Do not mill the head until you do the math on CR.

FYI- If the 250 is from '74 you may have the early version of the Dura Spark ignition system. Take a peek under the distributor cap to be certain. If you do choose to go DUI, someone will likely want the early, small cap DS.

Keep it coming.

Adios, David

 

[62Ranchero200]

Howdy back Bob and All:

IIWIYS I'd seriously rethink using flat top pistons in a 250. The 250 has a serious tendency to knock. Dished piston are more knock resistant than dished. The performance cam will help by reducing cylinder pressure. IF you want more compression ratio (Who doesn't?) consider having the top of the block milled or "decked". That will reduce deck height and improve quench somewhat. What is your compression ratio goal with this engine?

If you were thinking of using the 255 V8 piston for an additional .085" of pin height, consider having the crowns milled with a "D" shaped dish mimicking the combustion chamber shape in the head. That, and decking the block will get you close to a zero deck height, which would be ideal with a composite type head gasket. Do not mill the head until you do the math on CR.

FYI- If the 250 is from '74 you may have the early version of the Dura Spark ignition system. Take a peek under the distributor cap to be certain. If you do choose to go DUI, someone will likely want the early, small cap DS.

Keep it coming.

Adios, David

David,

Thanks for warning me about the 250's tendency to knock. That's certainly something I don't need.

Haven't done the CR math yet, but I want the highest compression I can run with the Supreme Unleaded available in this area (92 Octane I think). I'm definitely willing to pay more for Supreme if that will allow me to run a slightly higher CR. but I definitely don't want to have to run aviation fuel or octane booster (what if I need to get gas on the way to or from a cruise-in and no aviation fuel or octane booster is available?). I'd like your opinion on how high I can go with the CR. Don't want the engine "right on the edge" of knocking.

I'll have an '80 large log head with the largest combustion chambers (already have this head, with recent valve job and pocket porting), and replacing the thin (.025 I think) original steel shim gasket with a thicker (.045 I think) composite gasket.

Yes, the 250 is supposed to be from a '74 Maverick (block casting number is D2BE) so probably does have an early Duraspark - with the "merger" of the 200 and the 250 I will have quite a few parts that I need to give away or sell.

Thanks
Bob the Builder

 

[xctasy]

Probably info over load, but you did ask about what goes with what.

It should be the brilliant red insulator control unit Duraspark I set up. It's probably the best Duraspark. After that, the Blue grommit Duraspark was introduced, with reduced peak voltage. Ford had problems with product liability based on the first Durasparks ability to shock and awe the human heart if discharged accidentally. The early small cap DSI was designed around that first version, and the control box must match.

I use a composite gasket and 8.9:1 compression on 87 octane gas with my 200, and have run 9.7:1 with propane (99 octane) on my X-flow 250. Unless you retard the cam timing and have less than 180 psi cold cranking compression (corrected to sea level), reduce the compression ratio to less than 9.3:1 measured. You won't get away with less than 93 octane. Even if you use water injection, you won't be able to reduce combustion chamber pressures. Part of the problem is cylinders 6 and 1 are prone to lean out, and a 1 or 2-bbl carb won't supply enough gasoline to those cylinders, and lean knocking isn't noticable to the operator. The stock cast oversize pistons, weather it be Silvolite 12 cc, 5.5 cc, or flat top 2300 or 2500HSC, or 255, have been know on occassion to suffer cracking in No 1 under certain conditions, been documented here many times since the early days of this board. Heed Davids warning.

As for the engine bay, check with people who have the early round bodies. One guy fitted a 300 to his 61 Ranchero, it has the same block flange as the US 250, and he had to use a Big Friendly Hammer to help his 157 teeth/RUC gearbox fit.Not impossible, but as I've said, 1962 is a lottery as to weather or not you got Ford's phased in engine bay modifications. Drag link will have to be flipped over, the idler's chamfered, unless you can use the Mustang II gearbox with its much smaller bellhousing in which case it should clear with no mods.

Perhaps Powerband or some of the other Round body people with 250's or 300's might like to corroborate what I've said.

 

[bmbm40]

well you got plenty of advice, all good, these guys are the best. Maybe at this point direct mount for the 2100 might be a consideration to maximize the cam benefits. It may also give you some needed room under the hood.

 

[FalconSedanDelivery]

I have NOT found the 250 to knock any more than any others , as long as the CURVE in the Dist is correct for the usage , much has been changed over the years ( this is NOT the 60's 70's or 80's ) Gas is different , parts have been changed and worn out , also a Dished piston is NOT better than a Flat Top , Unless the end compression ratio is higher than the gas available / intended to use, ALSO , the later head is designed for EGR , ( open chambers with less squish ) so using it on any engine without ( 99% of what is done ) will be knock sensitive , UNLESS the curve is changed.

 

[62Ranchero200]

Bob, just a quick tip when you install the head studs. The front most passenger side stud goes into the water jacket and may hit the water pump impeller. You may need to grind off part of the stud for clearance. Many of us have had to do that. Just have the water pump installed first so you can turn it by hand. Then test fit the stud and turn the water pump by hand...if it is hitting you will hear it. Also you will need thread sealer on this stud so that water/anti-freeze won't seep up the threads. Happy building!

Thanks for the tip Gene! I will certainly check the stud's length and install it with thread sealer.

Thank you,
Bob

 

[62Ranchero200]

I have NOT found the 250 to knock any more than any others , as long as the CURVE in the Dist is correct for the usage , much has been changed over the years ( this is NOT the 60's 70's or 80's ) Gas is different , parts have been changed and worn out , also a Dished piston is NOT better than a Flat Top , Unless the end compression ratio is higher than the gas available / intended to use, ALSO , the later head is designed for EGR , ( open chambers with less squish ) so using it on any engine without ( 99% of what is done ) will be knock sensitive , UNLESS the curve is changed.

Thanks FSD,

Yes I will be using an EGR head, and no I will not run EGR on the engine, so it sounds like that setup will be more knock sensitive. I don't want to have to worry about knocking or make frequent adjustments to avoid it - I just want to set it up correctly on installation - "set it and forget it". How do I determine what the correct timing curve is? I will live with a compression ratio that's lower to achieve this. I really need to do the CR calculator math - it will at least be a starting point. I did physically check yesterday and there is 93 Octane gas available in my area.

Bob

 

[FalconSedanDelivery]

I can suggest having it done ( recurving ) , but tell you how , sorry , Ive been doing it for 25+ years , cant be done on a paragraph in a forum , there are sites that show you how , Google them ,If you choose to have it done , I do it as a service 89.95 plus parts , PM me ,

 

[CZLN6]

Howdy Bob and All:

Have FSD do it for you. It doesn't take long and doesn't cost too much. And no more worries. Mail your distributor to him and it will come back ready to bolt in. Give him as many details as you can.

IIWIYS, I'd plan for an engine that can run on 92 octane and less if necessary. I'm at 5,000 ft. elevation and run 9.8:1 with a 260 Comp cam. Your at a lower elevation and will likely need to stay closer to 9.2:1 as a CR goal.

Respects to FSD but, I reiterate, dished piston are more knock resistant than flat topped or domed piston. I've verified this generality with several sources. Specifically, with the 250, the knock tendency was with the huge deck clearance of .150" and more. This measurement made for a very lazy quench effect, even with dished pistons. Anything you can do to tighten up the deck clearance will improve combustion efficency and reduce knock tendency. That's where the modified 255 V8 pistons and decking the block to zero come in. But, the V8 pistons are significantly more expensive than replacement 200/250 pistons- and they will have to have a "D" shaped dish milled into them to help control compression ratio and to maintain the quench to bore ratio.

Keep it coming Bob.

Adios, David

 

[FalconSedanDelivery]

I will Clarify , If the Dish piston gave less compression , ( all other things the same), they would of course be less ping prone , BUT , when you are trying to get as much compression as possible and not ping the Flat Top will work better , Because of the Squish ,as you mentioned , the squish needs to be correct FIRST.and Yes the 250 was worse in that regard , add open chambered late ( smog chambers ) and it gets worse.we are on Kind of the same page just needed more unknowns filled in LOL , ,

 

[powerband]

I should add this reasomnable option to the discussion on dished vs flat top pistons :

The US 250 performance engine I'm running, uses TRW/SealedPower # 470NP's DISHED pistons. The application is 79-89 AMC 4.2(258).

The cc volume of the recess is 21ccs. With .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 street compression ratio of 8.8:1 with @ OEM deck/head before any milling. milled head chamber volume , gasket crush variable will raise CR.


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

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

have fub


Powerband