BCOWANWHEELS
Well-known member
What brand of forged pistons are the majority of you fellas using ? I,ve decided to go forged in my 250 build so I can get exactly the end product I want. a 9.5 flat top with iron log head.
thanks
bob
thanks
bob
FORGED PISTONS QUESTION
- Thread starter BCOWANWHEELS
- Start date
pmuller9":166famhu said:
:mrgreen: What he said. A great US piston with great results from a very smart company.
You've got a number of options. I'd recomend no more than 9.8:1 compression ratio with the specs you are looking at. So your 9.5:1 seams like a great call.
I know its all playing with semantics, so when you say flat top, you probably mean as flat top as possible with a zero or close to zero deck, and the bare miniumum of dish to get 9.5:1 on your 250 engine.
You won't get a flat top with 9.5:1 compression. With a 41 to 45 thou gasket, and 51 to 62 cc camber (56 is ideal) what you need is about 15 cc to get a sub 9:1 static compression ratio from a custom piston.
See viewtopic.php?f=1&t=72433&p=556443#p556443 and follow schaferstephen and the advice of 62Ranchero200
take a leaf from mike1157, 64fastRanchero and 62Ranchero200 and hae a custom forged piston made to get the right end compression.
viewtopic.php?f=1&t=73711
62Ranchero200":166famhu said:
I like the custom 6.21 300 rod and forged Racetek or CP piston, but there are other options that will work
Don't turn you back on 55 years of Aussie piston development. On the 4.1 250 engine, they went to as much as 27.9 and as little as 12 cc in the piston to get 8.6 to 9.35:1 compression ratios with 53 to 60 cc chamber heads. Doesn't mater if its a 250 (4.10, or a 3.9 SOHC or a 4.0 SOHC or DOHC, they all use the same 28 to perhaps 12 cc piston volume to get a less than 9.7:1 target static compression.
[/quote]xctasy":166famhu said:
I'm not sure what the rest of your engine spec is, but from your other posts I gather you are building a naturally aspirated, 9.5:1 CR, log head engine, possibly with higher ratio rockers. Nice setup to put in a driver.
That combo will give you a very torquey, robust engine, but will be limited in total horsepower and rpm. Airflow, rotating mass, rod ratio, and other factors will limit you to not much more than 6000-6200 rpm at redline, but most of your power will be produced well below that.
Unless you intend to run the engine at those elevated speeds continuously, forged pistons may be overkill. A nice set of forged pistons could cost up to $600 to $1000, plus rings. If you were turbocharged or running at constant high output that might be worth it.
Maybe Jeep pistons instead?
That combo will give you a very torquey, robust engine, but will be limited in total horsepower and rpm. Airflow, rotating mass, rod ratio, and other factors will limit you to not much more than 6000-6200 rpm at redline, but most of your power will be produced well below that.
Unless you intend to run the engine at those elevated speeds continuously, forged pistons may be overkill. A nice set of forged pistons could cost up to $600 to $1000, plus rings. If you were turbocharged or running at constant high output that might be worth it.
Maybe Jeep pistons instead?
A set of Autotec forged 4032 alloy pistons are in the $400 range.
Just a quick summary including some of what xctasy covered:
They are a lot lighter than cast.
Being eutectic the piston clearance is still relatively tight.
There is an accumulator groove to help with ring stability
You have the option of using a thinner ring set
They save you money on block and head machining since you order them with the correct compression height and dish volume for the compression ratio needed at zero deck.
It also gives the option of using the 300 six longer rods.
Just a quick summary including some of what xctasy covered:
They are a lot lighter than cast.
Being eutectic the piston clearance is still relatively tight.
There is an accumulator groove to help with ring stability
You have the option of using a thinner ring set
They save you money on block and head machining since you order them with the correct compression height and dish volume for the compression ratio needed at zero deck.
It also gives the option of using the 300 six longer rods.
BCOWANWHEELS
Well-known member
I called autotech and the fella said 500.00 for just the pistons and pins. rings and shipping not included. whats the next best choice fellas. this is just a street driven engine in my 63 comet and auto trans. my engine spec,s-
.020 over,
log head, big valves, ported and polished 2 x 2bbls (holley 94.s ) or new holley 350 cfm 2bbl.
mild cam
1.6 rockers adj.
headers
electronic dist brand unknown yet.
forged rods w/arp bolts (balanced / polished beams
.020 over,
log head, big valves, ported and polished 2 x 2bbls (holley 94.s ) or new holley 350 cfm 2bbl.
mild cam
1.6 rockers adj.
headers
electronic dist brand unknown yet.
forged rods w/arp bolts (balanced / polished beams
Good fortune with your build. Open forum discussion helps because you can see your way through the mine field of alternatives. 250 sixes have some specfic issues due to it being a 200 head with a long stroke block.
A few notes.
1. I got some very important info from a BBD Performance enginer builder realting to many dyno engine runs that show our air flow limited engines love longer rods. This is not always the case with other engines, but it is with the 250. Just a longer rod will make more peak power, but you may not like it on the basis of cost.
2. I'd go for any non HSC Tempo piston. I'm not anti HSC piston, but it might be a risk for any 250 engine since it seams to figure in some skirt failures. You don't want to use a piston that has a track record of failure like the Silvolite 489p does.
3. If you want to use the 255 piston you first suggested, you can, but you'll then you loose power with a poorer squecnh/chamber, and will need to pick this up by getting some more valve lift if you are planning on using the standadrd 250 5.88" long rod.
4. It depends on your situation, but remember, with a 255 piston at 1.585" compression hight, you've got an extra 90 to perhaps 103 thou over the 490 maximum allowable with a stock 200 engine...some where between 490 and 580 thou lift would make a lot of mid range torque if you got a custom ground cam to suit. Its true that the US 250 engine may have a deck problem, but it has the ability to take a very high lift cam without piston contact as well.
5. My other suggestions are 6" HSC rods with 27.9 cc pistons, or stock 5.88" rods and 255 pistons. here is also a 6.06" conrod we use in Australian Fords with the realted to 250 "4.0" 244 in line SOHC/DOHC engine
6. Your trying to find a sweet spot conversant with your cost goals. So if 1.6:1 rockers don't figure, then you need to discern what is important for you over all vlave lift.
My second piston options above, the US made Aussie 250 pistons, are now second options still if the 255 piston might be more your thing. You can have it contoured down to a certain cc, at a cost. Its all about what you need to get your pefromance and horspower goals.
7. Like everything, saying yes to one thing means saying no to others. The longer rods give you a 1.5% power boost everywhere. Expensive rockers can be cancelled out by having a custom ground cam, which will make more power and torque where it counts. An air flow limited engine loves valve lift, and longer con rods. A cheaper piston with a good compression ratio that suits your engine will save you on forged pistons. You can save on the long rods by having stock 5.88" rods. But get the wrong cast iron rods, and wrong pistons, and all your plans will be ashes.
A few notes.
1. I got some very important info from a BBD Performance enginer builder realting to many dyno engine runs that show our air flow limited engines love longer rods. This is not always the case with other engines, but it is with the 250. Just a longer rod will make more peak power, but you may not like it on the basis of cost.
2. I'd go for any non HSC Tempo piston. I'm not anti HSC piston, but it might be a risk for any 250 engine since it seams to figure in some skirt failures. You don't want to use a piston that has a track record of failure like the Silvolite 489p does.
3. If you want to use the 255 piston you first suggested, you can, but you'll then you loose power with a poorer squecnh/chamber, and will need to pick this up by getting some more valve lift if you are planning on using the standadrd 250 5.88" long rod.
4. It depends on your situation, but remember, with a 255 piston at 1.585" compression hight, you've got an extra 90 to perhaps 103 thou over the 490 maximum allowable with a stock 200 engine...some where between 490 and 580 thou lift would make a lot of mid range torque if you got a custom ground cam to suit. Its true that the US 250 engine may have a deck problem, but it has the ability to take a very high lift cam without piston contact as well.
5. My other suggestions are 6" HSC rods with 27.9 cc pistons, or stock 5.88" rods and 255 pistons. here is also a 6.06" conrod we use in Australian Fords with the realted to 250 "4.0" 244 in line SOHC/DOHC engine
6. Your trying to find a sweet spot conversant with your cost goals. So if 1.6:1 rockers don't figure, then you need to discern what is important for you over all vlave lift.
My second piston options above, the US made Aussie 250 pistons, are now second options still if the 255 piston might be more your thing. You can have it contoured down to a certain cc, at a cost. Its all about what you need to get your pefromance and horspower goals.
7. Like everything, saying yes to one thing means saying no to others. The longer rods give you a 1.5% power boost everywhere. Expensive rockers can be cancelled out by having a custom ground cam, which will make more power and torque where it counts. An air flow limited engine loves valve lift, and longer con rods. A cheaper piston with a good compression ratio that suits your engine will save you on forged pistons. You can save on the long rods by having stock 5.88" rods. But get the wrong cast iron rods, and wrong pistons, and all your plans will be ashes.