so the weak spot in the crossflow enigne is the pushrods right? is there anyway to beef up the motor so it can be spun at 7k?
nick
nick
crossflow weak spot
- Thread starter XFlow_Fairlane
- Start date
so ya wanna go to 7000.......first get your rods shotpeened ,resized and fit arp rod bolts or go the expensive way and get some h-beam rods .
get a race type harmonic balancer and get your flywheel checked for cracks and machined .make sure you have a good brand of piston.
get the right cam to suit your rev range plus the right springs and retainers .get your engine balanced complete from balancer to clutch.
now to the push rods ,CROW CAMS
get a race type harmonic balancer and get your flywheel checked for cracks and machined .make sure you have a good brand of piston.
get the right cam to suit your rev range plus the right springs and retainers .get your engine balanced complete from balancer to clutch.
now to the push rods ,CROW CAMS
DUNNO WHAT I DID THEN BUT ILL TRY AGAIN...
Now to the pushrods ,CROW CAMS ...they make a few different types of pushrod for the crossflow..either 5/16 or 3/8 diameter 080" wall hardened chrome moly .You may need to fit anti-pump lifters for that sort of revs . also a compulsory double row timing set.get rid of mechanical fuel pump and fan...if your feelin rich fit an electric water pump.
fit a new helmut to your head and strap in....
HOPE THIS HELPS A BIT
cheers .dave
Now to the pushrods ,CROW CAMS ...they make a few different types of pushrod for the crossflow..either 5/16 or 3/8 diameter 080" wall hardened chrome moly .You may need to fit anti-pump lifters for that sort of revs . also a compulsory double row timing set.get rid of mechanical fuel pump and fan...if your feelin rich fit an electric water pump.
fit a new helmut to your head and strap in....
HOPE THIS HELPS A BIT
cheers .dave
well 7k was just kinda a number pulled out of thin air. would 5-6K be more reasonable?
nick
nick
A
Anonymous
Guest
For sure. My XF 4.1 litre alloy head revs to 6000 with only a come racing racing head and cam. New carby and manifold and extractors.
Dan
Dan
A
Anonymous
Guest
Hey Dan,
Are You using the Stage2 or Stage3 head?
It looks like they do some good work on the web site.
When they port the Crossflow head, are the ports still round or are they more squared or oval in shape?
John
Are You using the Stage2 or Stage3 head?
It looks like they do some good work on the web site.
When they port the Crossflow head, are the ports still round or are they more squared or oval in shape?
John
I think the weak spot is the stock rocker. Just like the 351C the sledge fulcrum is not the greatest thing invented.
What I've found is that the stock pedestal is not that robust, so machining for studs leaves little meat for support if you drill and tap for a 7/16" stud base. Probably best to use a 3/8" stud and cut and weld 351C pushrod guides.
What I've found is that the stock pedestal is not that robust, so machining for studs leaves little meat for support if you drill and tap for a 7/16" stud base. Probably best to use a 3/8" stud and cut and weld 351C pushrod guides.
The hot tip is to use the Chevy big block sled fulcrum and retainers, and just limit things to less than 5300 rpm. This is where valve surge happens on a stock 250 cross-flow. The 200 x-flows can go beyond 5500 rpm, so some harmonics must get passed on to the gvalve gear via the cam. After market cams and there recommended springs don't seam to suffer, but there need the better valve gear for sure. The 4VHO 351/Boss 302/351 gear is too hard to get a posilock on, so the other option at about 400 bucks NZ is to get Yella Terra rockers for a x-flow 250. Bolt on, adjustable. Many US market 351 C roller rockers are made from YT extrusions anyway...imported into Aussie from America 
!
!
2nd.gunman
Well-known member
are the yella terra roller rockers a true bolt on or is machining head/fitting studs and guide plates required?
Ahhh. Late ammendment: YT has for $NZ 1000 a forth set of YT 6345's WHICH ARE SINGLE STUD 7/16, BUT HAVE A LOCATION DOWEL ON THE BASE!!!. No potential to turn around or mis-align. Jack, your question has been answered, and no gude plates, moly rods or stud girdle required!
Two out of three of the Yella Terra roller rockers for X-flows are true bolt ons! One, the big daddy hi-line one, isn't
Just got to make sure the stud doesn't loosen. A big lift cam with a sharp ramp and long duration might need some moly rods and guideplates. YT can advise. YT 5034 is a stock bolts on for about 500 ping, the YT 6018 is the same but adjustable, for an extra 100 bucks, and both use the stock stud. These may not like lifts over 480 thou at 5500 rpm or so, as they employ the stock5/16"( ~8 mm) stud which can pull out.
The giant killer(YT 5011), the 4V/Cobra Jet/HO/Phase III style 7/16(~11 mm) stud mount is really strong, but you must machine the 12 pads on the head to fit, and there needs to be a positive lock to stop it shifting. This is also provided by YT specifying ARE BARE MINIMUM of rocker studs,guide plates, hardnened push rods. The rockers alone are no more than the YT 5034, but all the extras cost big bickies. If you want your car to scream without firing a "dancing knitting needle", these are the items!
Jack noted
This has been are real issue for people trying to make a hi-po head out of stock 2V Windsors, 2V Clevelands, stock 429/460's. The 4V/Cobra Jet/Boss/Super Cobra Jet versions had much nicer castings which can take the bigger studs. There is no hi-po cast x-flow or alloy Honda Ford head, so were on our own. 3/8" studs (~9.5 mm) would be ideal, but they would need to fit the rocker designs. Chev guys designed the system, which was stollen from the Mark IV Mystery engine in 1965..I'm not sure if there exists a stud which is 3/8" based, shanked to suit the after market 7/16" roller rockers, yet doesn't loose strength.
Chevytown?
Two out of three of the Yella Terra roller rockers for X-flows are true bolt ons! One, the big daddy hi-line one, isn't
Just got to make sure the stud doesn't loosen. A big lift cam with a sharp ramp and long duration might need some moly rods and guideplates. YT can advise. YT 5034 is a stock bolts on for about 500 ping, the YT 6018 is the same but adjustable, for an extra 100 bucks, and both use the stock stud. These may not like lifts over 480 thou at 5500 rpm or so, as they employ the stock5/16"( ~8 mm) stud which can pull out.
The giant killer(YT 5011), the 4V/Cobra Jet/HO/Phase III style 7/16(~11 mm) stud mount is really strong, but you must machine the 12 pads on the head to fit, and there needs to be a positive lock to stop it shifting. This is also provided by YT specifying ARE BARE MINIMUM of rocker studs,guide plates, hardnened push rods. The rockers alone are no more than the YT 5034, but all the extras cost big bickies. If you want your car to scream without firing a "dancing knitting needle", these are the items!
Jack noted
This has been are real issue for people trying to make a hi-po head out of stock 2V Windsors, 2V Clevelands, stock 429/460's. The 4V/Cobra Jet/Boss/Super Cobra Jet versions had much nicer castings which can take the bigger studs. There is no hi-po cast x-flow or alloy Honda Ford head, so were on our own. 3/8" studs (~9.5 mm) would be ideal, but they would need to fit the rocker designs. Chev guys designed the system, which was stollen from the Mark IV Mystery engine in 1965..I'm not sure if there exists a stud which is 3/8" based, shanked to suit the after market 7/16" roller rockers, yet doesn't loose strength.
Chevytown?
i have the 6018 with the hardened crow push rods and as long as i keep an eye on the bolts holding down rockers i think they don't mind 6000rpm i have hit a bit over 7000rpm a couple of times. cam has about 0.51 lift. the hardened push rods work a treat as they will not bend! but i have snaped one (very unlucky).
so with new pushrods and beefier rocker with larger studs is what I would need? aside form any bottom end work..
nick
nick
