24 replies to this topic

[RedRallyMini]

Hi,

 

I've been offered a "stage 5 race" cylinder head with the following specs:

 

11 stud

number 1742 written on the head (somebody on the Belgian forum thinks it's a Longman head)

inlet 37mm

exhaust 29.4mm

double valve springs

4 titanium and 4 aluminium spring retainers

16.5cc chambers (seems a bit small, but I can always use a decomp plate?(don't kill me for suggesting this))

race valves (21NS)

bronze valve guides

 

 

 

 

 

Is this a good cylinder head or not?

 

I want to use it on my standard Metro 1275 engine with 1.5:1 rockers, is that possible without effing things up?

Edited by RedRallyMini, 17 November 2013 - 02:59 PM.

[Carlos W]

You need to calculate your compression ratio mate!

Cooperman has posted how to do it on a few threads

I'm on my phone at the moment so can't search very easily but once I can be bothered to get out of bed I'll see if I can find one

[RedRallyMini]

I don't know how to calculate the CR but the guy selling it said it would give me a CR of 11.5:1 and that I would need a decomp plate to get a CR of 10.5:1.

 

I've seen cooperman's post but it's way too complicated for me (partially because it's in English and I don't understand everything) ...

[jaydee]

Port are quite big, it should be good at top end and bad and bottmo-midrange, its a race head by the way.

A word of warning, these valve seats are so close that maybe prone to cracking.

 

To measure CR, you need to measure the chambers cc with a burette filled with parafin and a small glass. Measure all 4 chambers so you have evidence of eventual differencies between the chambers. Calculate the averag chamber cc.

Measure the piston to deck cc: put one piston at TDC using a DTI and use burette and glass to measure the cc. Add the cc of the head gasket (nominal values is between 3 and 4cc) and the chamber cc. This is the upswept volume to be divided by the (swept volume+ cylinder head volume) to obtain the static CR of your engine with said cylinder head.

Swept volume is calculated with normal maths, (bore size/2 x bore size/2) x Pi x stroke.

A video will make it easier to understand:

[RedRallyMini]

I've just calculated it (thank you jaydee for the video) with figures I've foud on the internet:

 

((pi x bore²) : 4)x stroke = swept volume: ((pi x 7.06²cm) : 4)x 8.128cm= 318.1874004cc

head volume: 16.5cc

gasket volume: 4cc

dish volume + piston to deck volume: 11.1cc+1cc= 12.1cc

 

(318.1874004 + 16.5 + 4 + 12.1) : (16.5 + 4 + 12.1)= 10.76034971

 

So the CR should be 10.8:1 if my calculations are correct...

Edited by RedRallyMini, 17 November 2013 - 02:55 PM.

[RedRallyMini]

Could somebody tell me if my calculations are correct?

[RedRallyMini]

Thanks everyone but I'm not going to buy it after all because I can't use it with unleaded petrol and also because it's only good at the top end of the rev range...

[jaydee]

I've just calculated it (thank you jaydee for the video) with figures I've foud on the internet:

 

((pi x bore²) : 4)x stroke = swept volume: ((pi x 7.06²cm) : 4)x 8.128cm= 318.1874004cc

head volume: 16.5cc

gasket volume: 4cc

dish volume + piston to deck volume: 11.1cc+1cc= 12.1cc

 

(318.1874004 + 16.5 + 4 + 12.1) : (16.5 + 4 + 12.1)= 10.76034971

 

So the CR should be 10.8:1 if my calculations are correct...

 

(70.61/2 * 70.61/2)* Pi * 81.28 = 318.277

 

If its a 'leaded head' you have to run it on tetraboost but..is it worth it?

Edited by jaydee, 17 November 2013 - 06:06 PM.

[RedRallyMini]

(70.61/2 * 70.61/2)* Pi * 81.28 = 318.277

If its a 'leaded head' you have to run it on tetraboost but..is it worth it?

 

 

Wikipedia says it's 70.6mm instead of 70.61mm, that's what caused the minor mistake (never trust Wikipedia!)...

 

And no, it's not worth it, that's why I'm going to search for an other cylinder head...

[RedRallyMini]

I've just discovered this, again (I already knew it, I just forgot about it..):

 

 

You just instal it into your fuel lines and it will, through some chemical reactions, distribute lead into your petrol, it lasts for 400 000km and I've read and heard some good things about it.

 

So I'll buy the cylinder head...

[GreaseMonkey]

Where is this lead thing available to buy from? Whats it called?

[RedRallyMini]

Where is this lead thing available to buy from? Whats it called?

 

It's called "Fuelcat" and it's available here:

 

http://classiccarser...chk=1&Itemid=26

[jaydee]

I can feel the smell of snake oil in this

[Jacksdad]

Snake oil is dead right!! It used to be called "Broquet" as far as I can recall. Was never proven (sp?) to do any good. Google is your friend on this. Cheers, Steve.

[ace01]

Snake oil is about right!  Just buy the cylinder head and use Castrol Valvemaster.    It's what I do.