11 replies to this topic

[karlnz]

Hello. I'm backtracking a bit here but ive got fresh 1275 +60 running a 544 cam that i got from a friend, however i fear that the head may have been 'chucked on there' as opposed to have being carefully selected to create a sucessful engine. I saw them apart at we put them together, together, howeve ri did not measure the valve sizes, the piston dish, or combustion chamber size on the head. However they are all freshyly rebuilt and machined and in excellent condition. The head has been mildly ported. I'm concerned my compression ratio is too low. Is there a way i can can 'ballpark' it without pulling the head off?  My questions relate to the cam.... Thanks in advance for any information, i really do appreciate it....

 

1) valve clearances? 15thou, correct?

 

2) advance curve? im running a 45d with vac advance. Its off to the rollers in a week and i have to get the dizzy to the operator a few days before the car arrives so he can do the advance curve.... he has a rough idea of where to get it but i said i'd get some more upto date info from the forums? should i be running vac advance too? how should this be calibrated?

 

3)static timing

 

4) static compression ratio? max octane we get here in NZ is 96ron (can get avgas easy but want to plan around the pumps)

 

5) valve lift, whats the max travel of the valves? according to vizard its .388" which leads to my next question...

 

my friend has a lovely head for sale at a good price, its just been crack tested skimmed and vacum tested, its beautiful, 33/29 and ports you could climb into, however...

 

Its has ALOT of meat taken off it, slightly concerned that the compression will be too high. Best way to measure is to do all the calcs... does anyone have the formula on here, i understand its piston dish cc, clearance at TDC, plus gasket (1275 (1330) 4cc?) then combustion chamber..

 

also theres so much meat off it that it looks like there will be bugger all, if any, clearance between the valves and the pistons. Does anyone know the best way to check this, other than bolting it on and turning it over? does anyone know what the clearance should be?

 

attatched is a picture of a combustion chamber

 

thanks, Karl

 

 

 

 

 

Attached Files

•  IMG_00431.jpg   56.59K   42 downloads

[Cooperman]

To establish & correct the C.R. the head will have to be removed.

Then measure the piston dish (or post the piston part number and we'll tell you the dish volume), measure how far down the bores the tops of the pistons are below block deck level at TDC. Then measure accurately the volume in each combustion chamber. The gasket volume can be taken as 4 cc.

Post those measurements on here and I'll be pleased to do the calculations and post them on here for you and anyone else who is interested.

So long as the head has been gas-flowed and has 35.6 mm inlet valves and 29.5 or 30.5 mm exhaust valves it will work well with a 544 so long as the C.R is around 10.3:1, which will be fine with 96 RON petrol. However, a slightly modified distributor advance curve will be needed for best running.+

The old 544 is a fine cam, but you have to be careful about gear ratios and final drive ratio as the peak power is at around 6200 rpm (from memory), so it will need to be capable of revving comfortably to around 6500 rpm and closer ratio gears and/or a low ratio final drive might be best to keep it all 'on the cam'.

[karlnz]

thanks mate, do you have any more information regarding advance curve modifications.... like how far?

 

also, just so my brain can learn these things, as opposed to me just doign what im told... what would be the consequences of a lower compression ratio than 10.3:1, or slightly smaller valves?

 

and what do closer ratio gears DO? i understand that a lower final drive will keep her on the cam sepending on the speed range that i want to drive in... i.e a 3.44 would be alot more suitable than a 2.9

 

thanks

[Earwax]

Hi karinz

 

Go to CSi multicurve distributor site for a look at curves for vac systems .   I would think   something with 23-24 degrees at 2000 rpm and 32-34 at WIDE OPen would work but DO YOUR OWN HOMWEORK and talk to the DIST modifier ie don't just take this as gospel)

 

Using the 33/29 valves would lose some of the potential of that cam ( cooperman's selection is tried and tested on sporty type cams. - kind of working against having that cam in the first instance)

 

You are spot on about final drives 3.44 would be better at keeping cam in the zone  - go to guessworks gear and ratio calculator to see what revs in what gear etc to check.

 

A Close ratio box has a taller first and then closer 2, 3, and 4  - subjective but most people say that is a good fit for the mini

 

As you suggest skimmed head could raise CR   you could go as low as 9.75 on ron 96 but you wouldn't really want to be in the 11s on that fuel

 

If you are running SU carb (ies) then vac advance is fine to stay - only really comes into play in cruise mode. If you are running Weber or dellorto most go no vac.

[Paul Wiginton]

Have you turned the engine by hand with the head on? Do the valves miss the pistons? That head looks to have had way too much metal taken off

[jaydee]

Valves look recessed theres even the possibility spark plug is too close to the piston, if not hitting..

To establish wether this good or not, you need to remove the vlves and inspect both valves and seat, huge ports wont really help power.

[karlnz]

thanks guys. Done several CR calculations... that head was no good, think its all over to be honest, maybe usefull for a 998

 

off to the dyno soon

 

thanks for the CSi resource, there are several curves on there but none of them are recommened for any particular cam/config

 

the above figs suggested by old mate (24/34) are very simlar to the 998 cooper... this correct, can anyone confirm a ballpark

 

or who makes the 544? its similar to a 286 right? ill have alot ok Kent's website

 

thanks :)

[Cooperman]

The 544 is the old BMC rally cam and is quite like a 286 but not quite as good at the top end. It is a nice cam to use with a well gas-flowed big-valve head and a good induction & exhaust system.
It used to be very popular for competition back in the 60's.

[karlnz]

forumal junior... im waiting for my vizard book to come from aus but its taking forver, trying to get some opinions on advance curve

[Earwax]

the 123 ignition dizzy (similar to csi but preceded it i think) has idle 10, 2000 24 and 5000 34  for late model minis and mokes with 1275,  I don't have as lumpy a cam and i just time on 30- 32degrees at what, and then look at the static, easy to touch tune :- set it to 30 by strobe then rotate slightly to see if improves etc. tyhen check idle  (10) and then take for a drive to check for knocking /pinking

[karlnz]

awesome, im using a 45d

 

should i keep the vac advance?

[Earwax]

hi

 

if you are running SU carb (s) keep the vac advance,  ( you need to block both carb and dizzy to set the timing though)

Edited by Earwax, 28 August 2013 - 10:00 AM.