Siamese'd Cylinders ?

[milnersXcoupe]

Read the new 5.7 has 'Siamese'd ' cylinders - is this great ?:flowers1:

the 4.7 to 2006 iron block isn't 'Siamese'd ' is it ?

Is it my guess that Toyota did this to 'package' the timing chain ?

 

[turboandrew]

I think the bore centers are extactly the same on both motors. 4.7 are not siamesed. There really shouldn't be much packing issues for chains. I'd actually suspect the engine is shorter in height and depth with chains, since they can use smaller gears than belts. As for the liners, maybe they just went with much thicker liners, so they had to be siamesed. Is the new motor open deck?

 

[striker]

if true.... not so nice.

just can't believe toyota would do this, is it really so?

grtz Thomas

 

[milnersXcoupe]

I read it in print - only one mention of it in over 9 hours of surfing the .net for data on the UR engines - totally bummed - as I don't like chain driven cam systems to begin with and now siamese'd cylinders...after three weeks studying Ford Cobra problems - overheating 'n hot spots being one - this needs s'plainin..

The 4.02" stroke is going to stress the cylinders differently than straight cyl. pressure - stands to reason they'd want to 'beef'...against 'rockin.... right ?..

I heard it is an open deck arrangement -


Upside of the UR production:

If the 2UZ FE can take a 3.75" stroke in the compacted graphite iron block - and if the 5.7 4.02" stroke crank as the same journal locations as the 4.7 -
we've a radical stroker kit - and a much nicer engine than the 5.7.

And if the 4.7 UR engine has an Alloy cyl. block - that can be retrofitted with a UZ top end - there'll be some great builds going on with that 94mm bore.


Bottom line to my mind:

belt drive is performance and you need coolant flow around the entire cylinder.

A great majority of the Cobra 4.6 / 5.4 failures are heat related.

Check: '.......had a Bad Uzzie Day.......' thread - some awesome failure pictures - heat related.

 

[striker]

Hmm, still strange isn'it

nothing wrong with chain drive cams now is there? yamaha put those to over 16.000rpm on their motorcycle's I deffo can't see a belt holding that up. almost all MC's have it like that without any apparent problems, holeshot turbo R1's go fine regarding cooling at 350+hp in the back of Global GT racers.
merc and BMW have been doing chains for all time (only at the front end), and honda has recently reverted back to aswell on the K20 and s2000 engines, as did toyota on a few engines high revving units. must be something good about this otherwise they wouldn't methinks.
cosworth V8's also all had chaindrive, and if that aint a performance engine.......

per setting cam timing, yes that can be a lot more hassle, but doable.

grtz Thomas

 

[milnersXcoupe]

hmmm.......design inertia - existing designs - supplier pricing, a long chain - a long heavy chain whipping air into oil - hauling oil out of the crankcase - added heat..... load force required to accelerate / decelerate a 3,500 RPM long chain vs belt - Porsche 944 Turbo / belt > lighter is better.

minor considerations but considerations Toyota / Yamaha settled upon before going after solid market shares - delivering what they believed was 'the best' design - before comparisons to F-150s and 'chain drive cams' began filtering into service bays by forgetful owners with 80K miles on the belts.

 

[turboandrew]

I trust Toyota to do chain drive well. They would not have made a switch -from- belts unless they were very confident about it.

I also don't anticpate many UZ/UR hybrids -too hard to match up a chain driven block with belt driven heads or vice versa. Besides, the UR heads are probably another improvement in design (much like pre98 UZ vs 98+ UZ heads)

 

[gte]

They do have the same center to center, I bought a head gasket for the 3ur yesterday and measured it, 105.5 or 106mm, center to center.

I doubt the engine is shorter in height, it has a much longer centerline to bore to achieve that stroke

I think the bore centers are extactly the same on both motors. 4.7 are not siamesed. There really shouldn't be much packing issues for chains. I'd actually suspect the engine is shorter in height and depth with chains, since they can use smaller gears than belts. As for the liners, maybe they just went with much thicker liners, so they had to be siamesed. Is the new motor open deck?

 

[gte]

The heads cannot be interchanged, checked that too

I read it in print - only one mention of it in over 9 hours of surfing the .net for data on the UR engines - totally bummed - as I don't like chain driven cam systems to begin with and now siamese'd cylinders...after three weeks studying Ford Cobra problems - overheating 'n hot spots being one - this needs s'plainin..

The 4.02" stroke is going to stress the cylinders differently than straight cyl. pressure - stands to reason they'd want to 'beef'...against 'rockin.... right ?..

I heard it is an open deck arrangement -


Upside of the UR production:

If the 2UZ FE can take a 3.75" stroke in the compacted graphite iron block - and if the 5.7 4.02" stroke crank as the same journal locations as the 4.7 -
we've a radical stroker kit - and a much nicer engine than the 5.7.

And if the 4.7 UR engine has an Alloy cyl. block - that can be retrofitted with a UZ top end - there'll be some great builds going on with that 94mm bore.


Bottom line to my mind:

belt drive is performance and you need coolant flow around the entire cylinder.

A great majority of the Cobra 4.6 / 5.4 failures are heat related.

Check: '.......had a Bad Uzzie Day.......' thread - some awesome failure pictures - heat related.

 

[milnersXcoupe]

Using the 5.7 UR crank for a stroker 4.7 is the most interesting
item.

Destroke 4.02" to 3.75" for a 5.5 @ 2 UZ FE stroker - nose would need
some massaging but a great asset none the less.

 

[gte]

The 3ur crank would not fit into the 2uz block

You'd be much better off just getting a custom crank out of billet

Using the 5.7 UR crank for a stroker 4.7 is the most interesting
item.

Destroke 4.02" to 3.75" for a 5.5 @ 2 UZ FE stroker - nose would need
some massaging but a great asset none the less.

 

[gte]

I can't find anything on the UR either

Can you post what you have at least? Maybe start another thread dedicated to finding info on the UR motors, on the web?

I read it in print - only one mention of it in over 9 hours of surfing the .net for data on the UR engines - totally bummed

 

[milnersXcoupe]

2007 Tundra 'Parts' - 4.0 / 4.7 / 5.7 -

Here's the thread currently on page 2:

2007 Tundra 'Parts' - 4.0 / 4.7 / 5.7 -


Only item of note was that the UR 5.7 has Siamese d
bores.

Of the UZ 4.7 block I read it is made of
Compacted Graphite Iron - which might explain
why it weighs 18 to 20lbs. less than a comparable
Ford NVH 5.4 DOHC cylinder block.