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3.5,3.9 & 4.2 heads

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Majority of R V8 pistons are graded and weighted, there is norm a small stamp on the crown,

all 8 need to be the same or the engine runs unbalanced, when I was young and stupid

(as oppossed to now old and stupid :P ) I found thisout the hard way :lol:

Nige

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Indeed Nige, IIRC nothing on the crown is standard, and either A or B is stamped toward the front on the engine on the piston crown. I think I have only ever come across A grade pistons in a 1988 3.5EFI engine.

Often with 3rd party supplied piston they just have the part number and '+' size.

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You have quoted 3rd party suppliers. Whilst we all use these folk for some of our parts they do not carry a complete stock, however, I found a number of options on all of the sites…….. I guess you were just being selective again….. :rolleyes: Intersetingly I spend quite a lot of money with one of those suppliers............

OEM there are currently six (6) 3948cc pistons available, however, when the assembly line was in place there we eight options

3948cc Piston HC RTC2295S (also available in +20 – RTC229520) which went to STC909 and is now 8510068

3948cc Piston LC RTC2186S (also available in +20 – RTC218620) which is now 8510109

3948cc Piston HC ERR5553 (Standard) ERR5553A (A Grade) ERR5553B (B Grade)

3948cc Piston LC ERR5555

In the above I have highlighted (bold text) statements that are incorrect, although I think you know what you mean, its just stated wrongly……..

There is only one block Suffix B block (this would apply to late 4L & all 4.6L) LCF104860 and the CR is governed by the Piston of which there are currently 4 options.

4554 Piston HC ERR5554 (standard) ERR5554A (A Grade) ERR5554B (B Grade)

4554 Piston LC ERR5556

I think we have done this to death, however, here we go again.

The 28cc chambered head was part of the phase II design package and takes into account not only the thickness of the gasket (which is slightly variable) but also the fact that the bowl in piston ERR553 (AB) is of more capacity than that of piston 810068.

TBH when you rebuilt your engine you would have been better off using Ford V6 forged pistons………. Or KB pistons http://www.kb-silvolite.com/index.html

Yes, you keep repeating this but still come back for more punishment ........... :ph34r:

This has been most enjoyable.............

So now you are just into posting things that are completely false.

So you list pistons that are for a 4.0 with those for a 3.9 and make out they will fit the same motor. You should know that they are not interchangeable.

Are you attempting to make out that A and B pistons have something to do with the head change. In the 4.0 and 4.6 motors LR do not make oversize pistons. B pistons are a couple of thou bigger than A pistons to take into any variations during the manufacturing process of the block.

Obviously you can't find anything different in the 3.9 A and the 3.9 B motors that would change capacity. But you still refuse to admit that they reduced the heads by 8CC, changed the head gasket and kept the same compression ratio. You also keep avoiding the question about how the 3.9 B motors had the short nose crank, so how can they have 4.0 internals.

At least you have shown your true colours. A person that will post whatever false information he can once he has dug himself into a hole that deep that he can't find any other way out.

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At the risk of ruining my reputation for talking b*ll*cks, some interesting tech just happened there...

Ian, care to expand on the difference between "standard", "A grade" and "B grade" pistons, and the use of Ford (or other) pistons in a Rover lump? Sounds like it could be a useful thing to know both from an engine building perspective and an emergency spares perspective. I have to admit I'd never really considered the interchangeability of things like pistons.

Read my reply to cowboy. Not sure why I have to educate you guys about basic stuff like this. Or maybe its some sought of test, in which case it you just failed to prove your point.

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John,

The way I understand it is, A , B and then standard and it comes down to the machining tolerance of the final product …….. with A at the top of the tree.

I think you are confusing the grading of blocks (which determines what engine they will be used for) with sizes of pistons. There is no difference in grade between A and B pistons. B pistons are just slightly wider, from memory its about 2 thou, maybe 4.

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I think you are confusing the grading of blocks (which determines what engine they will be used for) with sizes of pistons. There is no difference in grade between A and B pistons. B pistons are just slightly wider, from memory its about 2 thou, maybe 4.

I have to admit that I got it wrong again. It is 6 thou different. Here is section from RAVE CD.

Pistons

Type Solid skirt, elliptical open end with offset gudgeon pin

Material Aluminium AE413P

Clearance in cylinder bore. Measured 10 mm (0.4 in) from bottom of skirt, 90° to gudgeon pin.

Diameter - Grade A 93.970 - 93.985 mm (3.6996 - 3.7002 in)

Diameter - Grade B 93.986 - 94.001 mm (3.7002 - 3.7008 in)

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I have to admit that I got it wrong again. It is 6 thou different. Here is section from RAVE CD.

Pistons

Type Solid skirt, elliptical open end with offset gudgeon pin

Material Aluminium AE413P

Clearance in cylinder bore. Measured 10 mm (0.4 in) from bottom of skirt, 90° to gudgeon pin.

Diameter - Grade A 93.970 - 93.985 mm (3.6996 - 3.7002 in)

Diameter - Grade B 93.986 - 94.001 mm (3.7002 - 3.7008 in)

Bloody hell,admission - so how many "errors" could that add up to ? :rolleyes:

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just wanting to stoke the fire a little when i build my engines i always have the pisotns balanced to 1/2 gram the rods balanced end to end and the crank and flywheel and front pulley as well this makes for a very smooth running engine and also worth a few bhp as well, which as we all know every pony counts.

if you are wanting to build a hi comp motor as most of mine are i go this route

4.6 cross bolted block top hat linnered

4.6 crank

4.6 rods

4.0 pistons

give a comp ratio of 10.4-1 with comp gaskets

also a 22cc in the crown of the piston 28cc in the head and the the comp gasket also all pistons are cc balanced alonmg with the heads

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just wanting to stoke the fire a little when i build my engines i always have the pisotns balanced to 1/2 gram the rods balanced end to end and the crank and flywheel and front pulley as well this makes for a very smooth running engine and also worth a few bhp as well, which as we all know every pony counts.

if you are wanting to build a hi comp motor as most of mine are i go this route

4.6 cross bolted block top hat linnered

4.6 crank

4.6 rods

4.0 pistons

give a comp ratio of 10.4-1 with comp gaskets

also a 22cc in the crown of the piston 28cc in the head and the the comp gasket also all pistons are cc balanced alonmg with the heads

Works for me :i-m_so_happy: ......... but 4.0L pistons have a 13.23cc bowl (not 22cc as per the 4.6 pistons) ........ I guess that was a typo. ;)

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WOW OH BOY,

Did i ask a good question or what ?

Thanks for all the replies some reading.

Now for the next one, you said all heads are the same valve size etc

So are all the ECU's(14cux) the same, or is there a difference between 3.9L and 4.2L ecu's ?

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Checking with microcat the 3.9 & 4.2 share the same part number for the ecu....... early models were AMR1424 and later models AMP3243, so I guess they must be the same.

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Checking with microcat the 3.9 & 4.2 share the same part number for the ecu....... early models were AMR1424 and later models AMP3243, so I guess they must be the same.

Are there differences in other parts though - for example airflow meters? Not unknown for the airflow meter to have a different response curve from vehicle to vehicle.

And I may as well say - megasquirt it :P

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To get a 14cux to run a 4.2 properly(Fridge comments expected !) it needs the correct tune resistor, which is not green or white but yellow or blue.

Colour Ohms Cat Common Application

Red 180 No Australian 3.9

Green 470 No Europe & UK 3.9 (or 3.5 Disco)

Yellow 910 No Gulf States 3.9, or Europe & UK 4.2

Blue 1800 Yes Gulf States 3.9, or Europe & UK 4.2

White 3900 Yes Europe & UK 3.9 (or 3.5 Disco)

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Works for me :i-m_so_happy: ......... but 4.0L pistons have a 13.23cc bowl (not 22cc as per the 4.6 pistons) ........ I guess that was a typo. ;)

no was not a typo when we do the fill test on each cylinder for balancing with the piston at the top of the stroke and water/antifreeze mix poured in it equates to 22cc sorry not me typing all the info

as for ecus the 14cux ecu will adpt to a larger better breathing engine without major issues

if you have cats fitted and fit a non cat tune ecu disconnect the lambdas

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There's 2 very different tones in this thread, think one needs to calm down a just a tad smile.gif

'Arguing on the internet is like running in the special Olympics..........'

I agree. Perhaps when there is such a wide gulf in personal opinions those involved should resort to PM's, as what started as an interesting subject is now being seriously diluted.

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Is there a wy of telling what engine a set of heads came from? I am trying to raise CR in a stage 1 engine...

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Standard Heads will not raise compression ratio - all Rover heads are basically the same with minor changes between engines.  To raise compression ratio you need to change from low compression pistons to high  compression pistons.

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If you fit later 10 bolt heads that are intended for composite gaskets, but use a tin gasket intended for the earlier 14 bolt heads, you will increase compression slightly. However, then you have to shim the rocker pedestals or get adjustable pushrods to get the valve gear right.

I think composite heads have a volume of 28cc, and the tin ones are 36cc. In fact that info is probably contained somewhere in this thread that is a day older than god, on one of the pages before the handbags were deployed.

So to do it properly, yes you should really be changing pistons as Garry has said above.

Have a browse of v8forum.co.uk as it has come up plenty of times on there.

 

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