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post #1 of 7 (permalink) Old 12-20-04, 03:41 AM Thread Starter
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I6's beyond 6000rpm

When I first got my ef the engine had done about 60,000k's and although it would hit 5000rpm it did not sound nice (waiting for rods to come flying out of the guards). Since I rebuilt my engine (fresh balanced the bottom end - good parts), the engine easily revs to 6000rpm and sounds schweet every bit of the way. At these revs it is still pulling hard and shows no signs or running out of breath. Although it sounds good and is making power, it is not going to be doing my bottom end which still has relatively stock specifications much good. Anyway, it has got me thinking.

Now the basic design of the ford i6 limits its capabilities as a high reving engine, so I am wondering what can be done to the bottom end to push the limits. I guess the following items are going to be on the shopping list:

1. longer rods (AU / 3.2L)
2. lighter rotating assembly (pistons, flywheel etc)
3. Aftermarket engine management
4. Offset ground crank?

Anyone had any high rpm experience?

BTW- I am not thinking daily driver here, more of a strip/track weekender.

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post #2 of 7 (permalink) Old 12-20-04, 03:54 AM
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Re: I6's beyond 6000rpm

i would definetly run AU pistons and rods for a better rod ratio. id also use ARP rodbolts and get the rods shot peened and crack tested too as this is what usually lets go first. also the AU pistons run a teflon coating on the side and also have 0.000" piston to bore clearance (size for size)

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post #3 of 7 (permalink) Old 12-20-04, 04:21 AM
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Re: I6's beyond 6000rpm

1. what the diffence in length and weight between AU/3.2L?
if the same, then go the AU as i would think they would be lighter....

2. get the whole reciprotating assembly fully balanced seperatly then all the parts (crank, flywheel, balancer and i think they also use a the weights of the conrods/pistons bolted to the rod journals of the crankshaft) balanced together.

3. what r u thinkin of using? ive heard people on this forum have had good success on the 4L's with the EMS 8860

4. i dont really know about an offset ground crank, it will reduce some rotational friction but will also increase stroke. you will most prob get more power but i dont really know if it would rev more. i have read about a 250 X-flow that was offset-ground 80 thou which brought it to 280ci

titanium valves, custom machined titanium "rockers", roller bearing camshaft tunnel(not the word im lookin 4...but cant think of it...), billet crankshaft, but the most important thing of all with these things is to win lotto before putting them on your credit card.........,

on a serious side, an electric water pump would help a lot. definitly rev better.

underdrive pulleys would also help but i would think they would need to be custom made for the 4L
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post #4 of 7 (permalink) Old 12-20-04, 04:57 AM Thread Starter
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Re: I6's beyond 6000rpm

RE 1 - 3.2L rods are longer IIRC, but I suspect au rods are stronger.

RE 2 - The balancing done to the bottom end of my current engine made a very noticable difference. The crank was first balanced, then rebalanced with the harmonic balancer attached, then again with the flywheel. Each of the rods was then machined to 450g and each piston to 563.9g. This required a hell of a lot of metal to be drilled out of each of the components. I dont know what the tolerances are on stock components but seeing all those holes drilled in the counterweights of the crank I can see why these engines complain so much at revs.

RE 3 - I talked to boostin oz about the EMS computers (8860 and stinger) and liked what they had to say so I would probably lean towards them atm.

RE 4 - I was thinking about an offset grind to de-stroke the engine. I am thinking that the top end of a free reving engine may offset the loss of capacity. I really dont know that much about this though, like how much you can actually alter the stroke with the grind, how much of a reduction in stroke in nessisary to actually make a difference, and how this would change the power curve.

Money might not turn out to be to much of an issue. I cant see the parts costing that much more than a standard rebuild, and I have made a few contacts that will cut me some deals with the machining work. Anyway at the moment I am just throwing a few ideas around to see what people think.
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post #5 of 7 (permalink) Old 12-20-04, 12:28 PM
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Re: I6's beyond 6000rpm

I've had my BA XR6 manual up to 6600 sounds a little harsh - and wouldn't want to do that again. Missed a shift and ended up in second at 110 instead of forth....

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AU II XR6 - October 2001 ~ December 2002 - RIP
BA XR6 - December 2002 ~ Soon to disappear if Ford CRC can't fix it....

45,000km service coming up - and i'll be asking for a sizable list of fixes:
* Gearbox (3rd time)
* Steering click (5th time)
* Brake Shudder (2nd time, and has the applied "Fix")
* etc...
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post #6 of 7 (permalink) Old 12-21-04, 01:31 AM
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Re: I6's beyond 6000rpm

If you ofset grind the crank to de stroke it... What rods are u going to use then ???? Its def not worth doing at all....

My 250 i built runns the fowling its safe to 7000.

Yella terra rollers.
Wade Flat tappet Solid cam. 260@0.050 and 560 lift
Double Springs, Hardened Retainers.
302 Cleverland intake valves Machined down to 1.98
200 6 inch rods, fitted with arp rod bolts, and weighed
ACL RACE series pistons, light weight, Long rod series
Romac Alluminun Balancer
Mellings Oil pump
Crow dg2 dissy gear.
Crank, Fly wheel, And balancer all balanced.
Jp Timing chain double row..
Pace maker Extractors,
400 cc injectors
ED falcon manifold...

Now this was to get a shitty old 250 to like top end work..... I think AN au motor has all this, in the long rods, the balanced crank, rods, light weight pistons....
With an au bottom end, i think it would rev to what ever you wanted to a point..
Biggest problem would have to be the hydrualic lifters as i reckon they would start to oump up and hold the valves open...

98 T5 gear box (was auto)
Wade 977b cam
3.7 lsd
AU bottem end
ELXR6 ported Head
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post #7 of 7 (permalink) Old 12-21-04, 01:47 AM Thread Starter
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Re: I6's beyond 6000rpm

So you think that the bottom end is safe @ 7000 with a long rod & piston combo + balancing?
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