200 or 250 cubic inch

[Anonymous]

I am currently running a 250 x-flow in my Altered.I use around 6500 but would like to run up to 7500 reliably.Anyone with any info on this as I have been told that I will need to go to the 200 inch motor due to rod ratios.

 

[fordmuscle83]

6500 rpm?

Is the engine totally rebuilt? Thats wild revs for a stock crossflow.

Pete

 

[Anonymous]

Engine totally reconned ,30 over,speed pro cam,early style electronic ignition,9.3 /1 comp,10 psi boost[supercharged]600 Holley.Engine has never completed a full pass without a head gasket failure or pushrod failure ,but I am now working towards eliminating these problems
Best ET 11.6
Best MPH 132.

 

[xctasy]

As most die-hard 250 guys know, the engine was never a rever. It has a torsional vibration period somewhere, but its reputed to be okay to 7500 rpm if the rods, bolts and pistons don't explode.

Once you've added:-
either AU/BA 6.06" or XA-XF 3.3 6.27" rods (preped as appropriate)
with good pistons, and
a really got set of rod bolts and
a really good, big harmonic balancer and
ensured the mains are roll pined to stop spining (a David Vizard trick), and
have added a windage tray with crank scarper and enough capacity and
ensured the oil pump pressure isn't too high at max rpm

then the crank is the only worry!

The crank, being cast iron of a common grade, will possibly flex and need proper chamfers on the oil galleries, knife edging, and attention paid to the fillet radius.

Cast cranks fatigue over time exposed to vibration. Just because its been seasoned for 20 years in Mums family hack, doesn't mean it won't explode during RPM service.

The cost of this prep is huge in time and effort. Some racers in the US with the bigger 300, like the FrenchtownFlyer, have buddies who just fit some smaller journal, longer Honda rods, and use this to create a better fillet radius between the rod journal and the side of the counterweight/ crank flanges.

I'm sure some of the Aussies in Speedway are right on to it.

The best option is to go for a later crank from the OHC versions. The oil pump and main seals changed in 1987 to incorporate the new OHC production cranks in the old OHV X-flow used in the utes untill 1992.

I haven't ever been on intimate terms with the OHC, so I am only guessing regards the space for an EL fully counterweighed 12 bob crank. Earlier versions had 10 bob weight cranks of two different versions.

The OHC runs metric bolts.

AU/BA's have a different front mounted oil pump, and 2.65" mains.

 

[DYNOED250]

only the ba has the front timing cover oil pump the au still has the good old style oil pump

 

[Anonymous]

The harmonic problem mentioned in the post above is known to occur at around 5500 rpm on a crossflow. It is exaggerated on a forced induction engine also.

The harmonic problem stems from the camshaft arrangement and is not evident in the newer OHC engine. I have seen camshafts snapped in two on a crossflow engine which was continually revved past 5500rpm.

You will always spit pushrods if you continue to rev the engine past 5500rpm.

The head gasket is a different problem all together. My turbo engine spat a couple of head gaskets out the side into the pushrod gallery before I o-ringed the cylinder head.

If you are running too much timing and the engine is pinging this will also cause head gasket failure.

Are you running Methanol? If so you can afford to run reasonabley high compression so you could use long rods from the 200 CI engine and the ACL pistons designed to suit this conversion. This will help piston speeds and piston loads but won't get rid of the harmonics altogether. Like I said the harmonics are mostly camshaft related.

Another suggestion I have is to make your car's setup work with 5500rpm. I.e change the diff ratio and converter to suit.

Design your extractors, inlet manifolds and blower pulleys to suit this max 5500 rpm. With boost you will not need the RPM to make the power!

The limiting factor is the air flow your blower can provide efficiently so if you gear up the blower to be working at its peak efficiency at the same rpm range that the crossflow likes to work you will make far more torque at lower rpm and you will get similar power with less breakages.

Have you dynoed the engine? Does the engine power actually continue to increase above 5500rpm. I would doubt it.

My engine was making 530hp at 5200rpm using a 230 advertised camshaft 114 lobe centres and 17 degrees total timing. Boost was from a T04 turbo at 17 psi in my case. Max torque was 565 ft-lbs @ 3650 rpm

I have since changed the inlet manifold to have shorter runners and gone to a 256 advertised solid profile camshaft and I intend to make around 650 flywheel horsepower @ 5250 rpm. I am hoping to shift the maximum torque up to around 610ft-lb @ 4000rpm.

I am still using ACL pistons, standard shotpeened rods, O-ringed head, and 98 octane pump petrol.

 

[TCSTEVE]

Markze,

My engine was making 530hp at 5200rpm using a 230 advertised camshaft 114 lobe centres and 17 degrees total timing. Boost was from a T04 turbo at 17 psi in my case. Max torque was 565 ft-lbs @ 3650 rpm

I have since changed the inlet manifold to have shorter runners and gone to a 256 advertised solid profile camshaft and I intend to make around 650 flywheel horsepower @ 5250 rpm. I am hoping to shift the maximum torque up to around 610ft-lb @ 4000rpm.

I am still using ACL pistons, standard shotpeened rods, O-ringed head, and 98 octane pump petrol.

Mark that motor sounds mad!
What Crossflow 250 is it? Pretty interested in doind a turbo/crossfow setup for a drag car?
Thanks Steve

 

[addo]

That camshaft snapping biz sounds interesting! Is it shaft "whirl" in fact?

 

[aussie7mains]

Take some history of Quatermaines Torrie with turbo crossflow, has run 8.16et must be naking around 850bhp on methanol.
he stated out using a 250 but went to the 200ci engine with (i think) sleeved bores to come down to the OHC bore size.
BUT, why run pushroda at all when the OHC engines are relatively cheap these days and have so many advantages, better rods as stated, longer in the case of AU engines, OHC with it attendant loss of valve train problems, even the stockers will go 5500 any time.
Crow has cams available and I believe Kosteckis can provide solid lifters for the rocker arms.
So heres a suggestion, get a EA 3.2 litre bottom ned, or just get any 3.9 or 4 litre, put a 200 crank in it and go racing, there will be some piston issues but Im sure youll find something to suit, with the bigger valve and better breathing you should realise better power even without the rpm.
The AU engines are my preference as theyve got a better bottom end and scope for a main girdle etc, also larger main bearing diameter, to help with crank stability.
So ditch the crossflow and go OHC.
A7M
PS Im in perth in you want to chat get back to me.