Tear Down and Rebuild of My R400 Duratec Engine

[aerobod - near CYYC]

So after my sudden engine failure at just over 6000RPM (my bright blue knock sensor LED came on solid, which I've never seen before), on a track day Friday. I started the assessment of what failed today.

The initial failure seems to have been the "B" inlet valve spring on cylinder 1. You can see in the photo the bucket tappet almost fully depressed, but the cam isn't anywhere near it:

The spark plug had little left of the tip:

My fibre optic camera isn't very good, but even it's poor quality image shows lots of carnage on the top of the piston with what seems to be the initial imprint of the valve, then gouges and what seem to be holes punched by the valve stem:

 

I had a noise suppressor on the exhaust with SuperTrapp plates, this is some of the mixed steel (magnetic) and aluminium (shiny) bits I shook out from between the plates:

The "B" exhaust valve has the carbon scoured off and the remains of the assumed broken valve head seems to be visible, likely embedded in the head:

The engine is now prepped for removal with fluids drained, alternator, starter motor, exhaust and oil tank removed and all appropriate wires and hoses disconnected and bolts loosened. I ran a magnet through the drained oil and bottom of the oil tank and inspected the oil for any residual metal debris, none was found.

I plan on splitting the engine and gearbox to lift out fairly vertically, but I have a tilt bar with the engine crane if needed. Luckily I also have an engine stand to mount it to, it has been sitting in the garage for many years now without use, I think this engine is going to be on it for a while.

 

 

[simon_h]

Looks like you'll be needing to find a replacement donor engine and swapping the caterham parts over to me.

[7 wonders of the world]

James,

Some notes heading your way via BM

Once you have it in component ofrm you will be in a better place to fully asses the damage

Rebuild and engineer our the weaker areas ... 

Donor engines are unknown - let the buyer beware !!

[aerobod - near CYYC]

Thanks Neil, I would agree on the donor engines. The main decisions I see are:

- Is the block repairable? If any scrapes are less than 0.2mm deep, a rebore to a standard 88mm and a decking skim is on the cards.

- Is the head repairable? TIG welding by a head specialist followed by a skim may be enough.

- Which 88mm forged pistons (Wiseco, Omega/Accralite, etc) and what compression ratio?

- Which double valve springs? As this seems to have been the cause of the failure.

- Can I squeeze throttle bodies in to the budget and what airbox can I use to keep within track noise limits?

I'm thinking of keeping the same cams, crank and connecting rods and a similar rev limit, as the price otherwise is going to be closer to an upgraded crate engine. My overall budget limit is likely CAD$10,000 / £6,000, but I would need to factor in a rolling road session and shipping/customs charges into that, too.

[mic]

The rods will be standard ford items with interference fit pins, you may find it difficult to find the same type of piston. 

[Shortshift]

I seem to remember that double valve springs are not the answer, as they allow each spring to resonate independently within the assembly, leading to fretting between the springs and ultimately to fatigue failures.

There's quite a history of spring failures in the early R500 Duratecs (that Mick A helped educate me about) but, as I understand it, the single Cosworth conical spring with standard caps has been used across Caterham's higher-revving/more heavily loaded engines for quite some time now, without problems.

I know your engine if 420 spec but maybe there's a lesson here from the R500 experience?

James

[7 wonders of the world]

seen to many fail due to fretting which is why I run correctly weighted singles on mine... 

 

[aerobod - near CYYC]

I will have to see the type of failure of the spring when it comes out, if it is just a manufacturing defect or some other issue. definitely don't want to put the original spec ones back in, though.

Engine is now in place on the crane, just waiting for my son to come over tonight to give me a hand to make the removal easier:

[Shortshift]

Umm... whilst it's out, James, why not upgrade to R500 spec (or get Stuart Cresswell to do a trans-continental F275 conversion)?

You know it makes sense...

James

[Hampshire West AR]

Think the Cosworth springs are no longer available, Boss Racing upgraded mine to Kent Cam valve spring kit.

Nick

[aerobod - near CYYC]

I think my budget is way under for major power upgrades, James. Especially with the issues of shipment to Calgary, typically adding 50% to the ex-UK cost after duty and brokerage is added to crated items. I would also need to add the struts/bracing for the diff to ensure no cracking of the frame mount points due to the extra power. 230bhp with an 8000RPM redline and 11.5:1 compression ratio would be an initial target, depending on what I need to replace.

[Shortshift]

Sounds good, James.  The diff struts are just pennies in the scheme of things, but I get what you're saying.

Good luck as you delve deeper,

James

[aerobod - near CYYC]

Had a bit of a run around yesterday to find suitable mounting bolts to attach the engine block to my engine stand, but now it is attached, I tilted it and a piece of valve stem fell out into the intake plenum:

 

 

Need to make a crankshaft brace to hold it in a fixed position by locking it to one of the bellhousing bolt holes in the block, as the flywheel had to be taken off to fit the engine stand so I can't use a conventional locking tool on there. Will do that this afternoon to be able to start full tear down tomorrow.

[Golf Juliet Tango]

Quite a challenge James. Good luck with it. 

[Amos91]

I'll be amazed if there is no cylinder wall damage. 

[7 wonders of the world]

An old 'intact' valve with a 90 degree bend in the stem works a treat, pop the stem in one of the dowel holes and the edge of the valve locks in the teeth.

Might be worth checking the valve timing before you crack the crank bolt off and loose it, not sure if yours runs OE timing.

[aerobod - near CYYC]

Only had a few minutes to look at things today, but I did find out where the valve head went:

[Nigel Blandin]

I thought the Duratec was a U.S. motor? Are they not tuned over your side? Or Maybe a 2.3 CSR type jobbie....

[aerobod - near CYYC]

There are plenty of Duratec variants over in North America Nigel, but there are lots of parts variations that are different than the Caterham variant that is closest to the Mondeo Duratec.

[aerobod - near CYYC]

Disassembled almost all the components today (still have to remove the pistons, but will need to go and find an external Torx socket this weekend to remove the big end bolts).

After removing the bucket tappers, a piece of valve stem was jammed in the cylinder #1 "B" inlet valve guide and needed a punch to remove it:

On the other side of the head the valve head was jammed sideways into the seat with plenty of impact marks in the head. If I have the head repaired, the impact areas will need welding and a new seat will be needed. There are also quite a few impact marks in cylinder #2 from debris ingestion, along with a small mark in cylinder #3:

The valve guide has partly shattered and will need replacement as part of head repair, it is likely the source of the small steel bits I found in the exhaust:

 

The valve spring broke in 3 pieces with what looks like a double torsion failure. Subsequently the valve was pounded into 4 pieces:

 

Although #1 piston is badly damaged, it wasn't pierced by the debris and I haven't found anything in the oil that shows overall bottom-end damage. The connecting rods also all seem to be the same length (so no bends), with all pistons measured at 0.7mm below the block top surface, which seems to be the appropriate spec value:

 

Some scratching of the bore, but doesn't seem to be as deep as 0.2mm, so a 0.5mm over bore to 88mm looks to be the best option, instead of scrapping the block:

 

I will have to talk to some engine machining specialists next week and see what they advise in terms of rebore and head repairs.

[Shortshift]

I know it's small consolation, James, but the step-by-step voyage of discovery (and hopefully also of the rebuild, in due course) are really interesting.  Please keep posting!

James

[7 wonders of the world]

Plenty of Tuners and parts in North America - not sure on import duties over the border though...

 

 

[aerobod - near CYYC]

Typically I have found it is cheaper overall to get parts for non-American v8s from the UK than from the US, Neil. The shipping time is often quicker, too and the VAT saved often will cover the shipping cost, duty and brokerage from the UK to Canada. This may change when the part is not shipped by air and is over the 30kg limit of a standard parcel, though.

[aerobod - near CYYC]

Had to cleanup and rearrange the garage today instead of working on the engine, to make room for the new M2 arrival that was about 3 weeks earlier than expected. Had to push the Caterham out to take the RGB photo:

[Shortshift]

That's a very nice collection!  I think of the new M2 as the spiritual successor to the brilliant, compact M3's of previous years (E46 era).  And the Macan is hard to beat as a solid all-round daily.  As for the green thing in the middle...

James