Xf Falcon 250 xflow rebuild

[Anonymous]

Hey everyone

Calling for everyones valued help and opinions for some ideas on a rebuild for my XF falcon... Lately its running pretty good, but I'm not sure about a noise it has, it has the usual lifter tick, but it also has a dull knocking sound that kinda sounds like a quiet diesel rattle in the bottom end. My dad suggested that it could be piston slap, but I thought it's kinda strange considering the previous owner had the engine rebuild 50,000km ago...

So that leaves me with starting from fresh, and rebuilding a strong, yet streetable 250 alloy head xflow carby engine. Now the engine, been a leaded engine from a few of the first XF's, runs 9:35.1 compression standard. I have a megatork high performance cam (215 @.50 duration, .496 valve lift), heavy duty MT250K valve spring kit to suit, double row timing chain, h/d dissy gear and new lifters - so I dont have to worry about those. That leaves me with getting the bottom end sorted, I was thinking of using ACL components, what do you guys think I should use? I want it to be able to do 5000rpm without killing itself over, the cam's power range is 1800-4800 so I would possibly hit 5000 occasionly. Howmuch would I be looking to spend to get the bottom end sorted out? My father will assemble it all, that just leaves me with the cost of parts, and machining.

So I would probably have to do the following - Pistons, Bearings - What else? What work is worth getting done to the crank? What pistons should I use?

I want the engine to be streetable, and safely run on 98 octane fuels.

Thanks for taking the time to read all this, can't wait to read some informative replies from the blokes in the know!

 

[Anonymous]

Just taking a look at the ACL race series, and the flat top pistons... but they would probably raise compression to high?

 

[Anonymous]

Anyone? Addo? xtaxi??

 

[addo]

I'm brain dead tonight. Too much possum chasing.

Have you tried No More Gaps or Selley's Roof Gutter and Compression Ring Sealant?

 

[Anonymous]

Also been told about the shitty standard rod bolts and how they just love disintegrating about 5000rpm.... how would one cure this.

 

[xctasy]

Dame Edna Average does a great job at scaring Possums!

Good at 'drag' racing too.


I'd just pike out an use XE 4.1 spec leaded pistons with the lower 22 cc dish. Make certain they are to be for the XE, as factory replacements are low tension, and don't like big revs.

Keep away from low tension rings if you are going to hammer it. 4500 RPM IS THE LIMIT FOR AN XF 4.1, not 4800 (XD and XE alloy or 5300 rpm XD cast iron)

ACL have a part number, care of Alloy Dave. These don't have low tension rings, but often come as 3.3 pistons with a 15.3 cc dish, way too high compression for a 250. In my opinion, its better to get a used XE 4.1 carb short block engine, and send it exhange to an engine reconditioner, and have him send you an XE engine back on exchange.

alloy dave said:- your engine could be
one of about 4 different options . you may have to cc the dish in the piston
leaded petrol pistons have a 22cc bowl
unleaded petrol pistons have a 27.9cc bowl
hi comp pistons from acl auzzie have 15.3cc bowl
the stock production 3.3 units were also 15.3cc 5.88" rod

The ACL Race Series pistons are in Eutectic material and not in
Hypereutectic. Please contact the distributors or stockists (see web
page for details.) for pricing.

I'm not sure what the stock ACL list is, but they all suit 4.1 250 engines with stock 5.88" rod. ACL Race have 38.86 and 29.54 mm deck pistons

ACL Race Pistons are:-
6mkry9411 hi comp/performance, they have 8.6cc bowl
6mkry9412 has a 8.6cc bowl for short deck 6.27" rod
6mkry9413 is a flat top 0 cc..this is a 2 ring piston, flat top which is 11.2:1 in a stock XE, 6.27" rod


I'd not use the 6mkry9411 hi comp/performance acl auzzie pistons as they have 8.6cc bowl, very high compession. 10:1.

If you do use them, you will have to machine 1mm from this crown. To drop your comp ratio by half a ratio down to 9.5, you would need a bowl volume of around 13cc which is 4.4cc more than the
nominal 8.6cc on the 9412 piston.

Increasing the bowl depth by 1mm will give around an extra 4.75cc which should do the trick.

The later kidney bean heads have the high swirl ramps, and they carry lots of compression. They are detonation prone too, but they ran very mild cams and had high gearing. When 91 octane came, they got bigger 22.7 cc pistons. The bigger dish was used to drop CR in Jan 1986 to 8.8:1 or so . With the bigger cam bleeding off effective compression, you should be able to run the 9.35:1 CR.

Don't use the EFI headgasket, use the Permaset Grand Prix item. It's thick and strong. Douh!

Care of alloy dave 67xr6,

AA GASKETS (permaseal) in aussie also do a "GRAND PRIX " gasket which is also a good performance gasket. P/NUMBER BH100GP

Try WWW.ACL.COM.AU or WWW.AAGASKETS.COM.AU

The short engine is normally 800 ping exchange, with you left to degree the cam, fit the engine, and screw the head an jewlery, with extra for exotic bits. No thin deck ACL's and 6.27" 3.3 rods. They normally use garden variety ACL 250 p/n 7M2158 bearings unless you pay extra

The engine is a nice peice of iron. Detonation is the enemy of any x-flow. Like base model Clevelands, they cary a lot of compression, but give you no warning when our low grade 98 causes detonation to set in. You hear the onset of knock on early log head engines well before the damage is done. In canted valve engines, you don't hear it, you just deal with the valve gear, bearing and piston failures. Having said that, a Falcon x-flow is a heck of a lot tougher in the pistons and timing gear than the earlier log and 2v's.

 

[Anonymous]

So to sum up what you are saying, Send a XE short block to engine reconditioner, he will put basic ACL pistons in and make sure its all good, and then bolt on a head, put my cam in etc with all the goodies and run around but dont exceed 4800 on a daily basis?

 

[xctasy]

Yes.

The alloy head can cope with 5500 rpm in a 3.3, but not more than about 4800 in a 250.

 

[addo]

My bloke charges $1800 for a short, no cam or timing set.

 

[Anonymous]

Where could I obtain aftermarket rod bolts from that would be strong enough for say, 5000rpm? What headwork should I get done, just a little shave? Or should I go porting aswell...

Are the COME racing heads any good? They charge $999 and quote 200hp from their heads, sounds pretty expensive considering the heads arne't all that bad in the XFLOWS.