250 XFlow Rockers

[StarDiero75]

Howdy guys,

So i recently acquired a 250 xflow and im in the process of gathering parts. The rocker bolts look like 5/16" so I know that ain't flying. I'm looking to push it to 6500 RPM. I'll be using Molnar 300 rods and custom forged pistons. Possibly larger intake valves. Supercharger. Still researching cams. I am planning to use a 1.73 roller rocker off a 351C/460. They typically use 7/16" studs, which I don't think there's enough meat in the head boss to hold that together just by looking at it. What is the typical thing done here? Machine the tops off and install 3/8" or 7/16" studs? Adapter plates? Whats the secret? I would also assume for this setup to run 3/8" pushrods, right?

Thanks!

 

[Cox Custom Mechanical]

There are already rod and piston kits out there rather than using custom 300 rods and custom pistons, your application doesn't look that ground breaking.

3/8 to 7/16 all depends on cam and spring pressures etc, at 6500 with a reasonable cam 3/8 will still be ok. If you are thinking over .550 lift id suggest 7/16 studs.

Yes machine them off drill and tap, sometimes you need to do a bit of welding to build up the areas and if you are trying to make a decent amount of power you will be welding the top of the intake port to raise the runner.

Again pushrods thickness and diameter depend on your setup, 5/16 will do most but sometimes with boosted applications I use a larger diameter or thicker exhaust pushrod because of the high cylinder pressures.

 

[rocklord]

Are these the some of the rod and piston kits you are talking about?

250 XFlow Conrod + Piston Deal

Australian online store selling genuine Spool conrods, crankshafts and performance parts worldwide.

www.spoolimports.com

 

[aussie7mains]

Are these the some of the rod and piston kits you are talking about?

250 XFlow Conrod + Piston Deal

Australian online store selling genuine Spool conrods, crankshafts and performance parts worldwide.

www.spoolimports.com

Thats what Id suggest, the 200 rods are 6.27 long. The dished piston would be a good start. Crow is a good source for cams, I doubt you will find anything stateside for the crossflow. Yellaterra do a line in rockers for them. Aussiespeed have blower manifolds. I doubt you will need 6500rpm to get what you desire. The EFI crossflow heads have about the biggest valves you can fit, 1.84/1.54, they hay silicon bronze inserts in the head. Pushrods are the achilles heel of the crossie, they are long and spindly. I'sure you can find something localy.

 

[Cox Custom Mechanical]

Thats what Id suggest, the 200 rods are 6.27 long. The dished piston would be a good start. Crow is a good source for cams, I doubt you will find anything stateside for the crossflow. Yellaterra do a line in rockers for them. Aussiespeed have blower manifolds. I doubt you will need 6500rpm to get what you desire. The EFI crossflow heads have about the biggest valves you can fit, 1.84/1.54, they hay silicon bronze inserts in the head. Pushrods are the achilles heel of the crossie, they are long and spindly. I'sure you can find something localy.

I also stock and supply all of those brands. I am also paid sponsor that supports this site...

 

[aussie7mains]

I also stock and supply all of those brands. I am also paid sponsor that supports this site...

Didnt know that.

 

[StarDiero75]

There are already rod and piston kits out there rather than using custom 300 rods and custom pistons, your application doesn't look that ground breaking.

3/8 to 7/16 all depends on cam and spring pressures etc, at 6500 with a reasonable cam 3/8 will still be ok. If you are thinking over .550 lift id suggest 7/16 studs.

Yes machine them off drill and tap, sometimes you need to do a bit of welding to build up the areas and if you are trying to make a decent amount of power you will be welding the top of the intake port to raise the runner.

Again pushrods thickness and diameter depend on your setup, 5/16 will do most but sometimes with boosted applications I use a larger diameter or thicker exhaust pushrod because of the high cylinder pressures.

So whatever setup I get will end up being "custom". The kits are like $1700 a set. The Molnar 300 rods are like $650 and unless custom pistons are $1000, then whats the benefit? Just curious. Also, I noticed they are for 0.040" over, I have a standard bore motor and would really prefer not to take off more than necessary, especially if I am boosting.

Currently I am trying to find an engine builder who's willing to touch this. The very reputable one I'd like to take it to wants me to get all this info ahead of time, otherwise he won't touch it because he hasn't dealt with one before. He has a few more questions:
1. Any torque plates? He's not super excited to machine without one since he knows what power goal I want.
2. Forged cranks? Any worries with stock cranks, why or why not?
3. Special harmonic balancers to allow to spin up to 6500?
4. Any known cooling issues? He believes the #6 cylinder is known for getting hot like on the old 200s/250s.
5. Any other issues or concerns to build to this kind of power?

 

[StarDiero75]

Thats what Id suggest, the 200 rods are 6.27 long. The dished piston would be a good start. Crow is a good source for cams, I doubt you will find anything stateside for the crossflow. Yellaterra do a line in rockers for them. Aussiespeed have blower manifolds. I doubt you will need 6500rpm to get what you desire. The EFI crossflow heads have about the biggest valves you can fit, 1.84/1.54, they hay silicon bronze inserts in the head. Pushrods are the achilles heel of the crossie, they are long and spindly. I'sure you can find something localy.

You would suggest the yellaterras over anything normally for the 351C motors?

I was thinking of trying to sneak a little larger valve for either the exhaust or intake as it looks like I can do one or the other. Are the silicon bronze seats better than a normal "hardened" seat that gets installed?

I have read that about the pushrods. I was planning on using something from Summit racing's site.

I currently have a crow cam but I don't think it's gonna be enough for the plan. I'll try and find the number on it unless Rocklord knows offhand which one he gave me. I can have my crow reground to something different, right?

I do have the 6.27 200 rods already. pmuller suggested not using them b/c they won't hold up to the power and to look at the 300 molnar.

 

[aussie7mains]

You would suggest the yellaterras over anything normally for the 351C motors?

I was thinking of trying to sneak a little larger valve for either the exhaust or intake as it looks like I can do one or the other. Are the silicon bronze seats better than a normal "hardened" seat that gets installed?

I have read that about the pushrods. I was planning on using something from Summit racing's site.

I currently have a crow cam but I don't think it's gonna be enough for the plan. I'll try and find the number on it unless Rocklord knows offhand which one he gave me. I can have my crow reground to something different, right?

I do have the 6.27 200 rods already. pmuller suggested not using them b/c they won't hold up to the power and to look at the 300 molnar.

YT rockers can be obtained in a direct bolt on form, plus you get a kit with everything you need. Stock rockers work ok up to a point.
Silicon bronze is what everybody uses here, Id stick with them, I dont think there is much to gain with the slightly larger intake valve, and exhaust is good as it is.
Pushrods, somethings needs to be done there.
Crowcams, need to know the PN.
Many guys race with the 200 rods in 250s, they run then out to 6500, you here of occassional blow ups. If you can get better rods at a reasonable price, do it.

 

[pmuller9]

Remind me.
What are you looking at for power?

 

[Jmustang_65]

So whatever setup I get will end up being "custom". The kits are like $1700 a set. The Molnar 300 rods are like $650 and unless custom pistons are $1000, then whats the benefit? Just curious. Also, I noticed they are for 0.040" over, I have a standard bore motor and would really prefer not to take off more than necessary, especially if I am boosting.

Racetec will make a piston, I'm sure for less then $1000. My custom pistons were about $700.

 

[Jmustang_65]

3. Special harmonic balancers to allow to spin up to 6500?

Check out Romac Balancers.

Romac parts for Ford engines

www.norndaautomotive.com.au

 

[aussie7mains]

So whatever setup I get will end up being "custom". The kits are like $1700 a set. The Molnar 300 rods are like $650 and unless custom pistons are $1000, then whats the benefit? Just curious. Also, I noticed they are for 0.040" over, I have a standard bore motor and would really prefer not to take off more than necessary, especially if I am boosting.

Currently I am trying to find an engine builder who's willing to touch this. The very reputable one I'd like to take it to wants me to get all this info ahead of time, otherwise he won't touch it because he hasn't dealt with one before. He has a few more questions:
1. Any torque plates? He's not super excited to machine without one since he knows what power goal I want.
2. Forged cranks? Any worries with stock cranks, why or why not?
3. Special harmonic balancers to allow to spin up to 6500?
4. Any known cooling issues? He believes the #6 cylinder is known for getting hot like on the old 200s/250s.
5. Any other issues or concerns to build to this kind of power?

Torque plates probably not,
Forged cranks, can be sources but VERY expensive, not really needed, barra is similar and they will go 750kw on stock nodular crank.
Special balancers, yes ROMAC in Adelaide have them.
Only cooling issues known is when there is a lot of corrosion in the system, otherwise usually no problems.
These things are like a brick shithouse, people have got huge power out of them, they seem to be able to handle 500bhp fairly well, the Barras are known for up to 2000bhp with factory blocks and heads, there are NO aftermarket blocks or heads ATM

 

[StarDiero75]

Remind me.
What are you looking at for power?

I'd like to see 450-500 at the crank. That'd just tickle me lol.

 

[StarDiero75]

Torque plates probably not,
Forged cranks, can be sources but VERY expensive, not really needed, barra is similar and they will go 750kw on stock nodular crank.
Special balancers, yes ROMAC in Adelaide have them.
Only cooling issues known is when there is a lot of corrosion in the system, otherwise usually no problems.
These things are like a brick shithouse, people have got huge power out of them, they seem to be able to handle 500bhp fairly well, the Barras are known for up to 2000bhp with factory blocks and heads, there are NO aftermarket blocks or heads ATM

Thanks for going through the list. I'll get this info back to my guy. I'm also gonna start talking to Jeff Jones. I have heard he's a pretty impressive builder of the Ford inlines in California. Just wish he was a little closer. Just gives me an excuse to use some hotel points lol.

Maybe Matt Cox or Jeff have torque plate since they build hopped up motors. Then maybe this will work out.

 

[StarDiero75]

YT rockers can be obtained in a direct bolt on form, plus you get a kit with everything you need. Stock rockers work ok up to a point.
Silicon bronze is what everybody uses here, Id stick with them, I dont think there is much to gain with the slightly larger intake valve, and exhaust is good as it is.
Pushrods, somethings needs to be done there.
Crowcams, need to know the PN.
Many guys race with the 200 rods in 250s, they run then out to 6500, you here of occassional blow ups. If you can get better rods at a reasonable price, do it.

I'll do yoy one better and include the cam card. Its 2800-6000rpm range. This is a rompy cam. Its a Crow 14650 cam. This is just what came with the motor (not installed).

 

[rocklord]

StarDiero75, the cam you have is a Crow Cam 14650.
Attached is the cam specs.

 

[StarDiero75]

StarDiero75, the cam you have is a Crow Cam 14650.
Attached is the cam specs.

I think I uploaded it at the same time you were haha. Thanks foe that. I had to go to the garage and look.

 

[Cox Custom Mechanical]

Thanks for going through the list. I'll get this info back to my guy. I'm also gonna start talking to Jeff Jones. I have heard he's a pretty impressive builder of the Ford inlines in California. Just wish he was a little closer. Just gives me an excuse to use some hotel points lol.

Maybe Matt Cox or Jeff have torque plate since they build hopped up motors. Then maybe this will work out.

Matt does not build anything...

If Jeff does as many small sixes as people say then id imagine he would have or his machinist will have a torque plate. For a Small six it is necessary to torque plate hone engines as the bore distortion can be up to .001 at the top of the block, granted its less on a crossflow block than a pre crossflow.

Your cam is on the small side for 450fwhp unless you are jamming in some boost.

 

[Cox Custom Mechanical]

Torque plates probably not,
Forged cranks, can be sources but VERY expensive, not really needed, barra is similar and they will go 750kw on stock nodular crank.
Special balancers, yes ROMAC in Adelaide have them.
Only cooling issues known is when there is a lot of corrosion in the system, otherwise usually no problems.
These things are like a brick shithouse, people have got huge power out of them, they seem to be able to handle 500bhp fairly well, the Barras are known for up to 2000bhp with factory blocks and heads, there are NO aftermarket blocks or heads ATM

Close but not quiet true, there are a few people making aftermarket Barra blocks.

As for crossflows there was one or two aftermarket crossflow blocks made, I know where one of them is as for the rest. No idea.