Cooper works High lift rockers with Isky springs?
Discussion
Anyone know if I’ll have a problem using the high lift rockers (1.5:1) supplied on the cooper sport 5 works with isky double valve springs?
I have a big valve head with high compression (about 11:1), the engine builder said I need to fit at least a 285 cam, I’m hoping I can chuck the head on my standard engine for the London and Surrey track day at Goodwood next month, was going to fit the rockers to give it a bit extra lift.
I have a big valve head with high compression (about 11:1), the engine builder said I need to fit at least a 285 cam, I’m hoping I can chuck the head on my standard engine for the London and Surrey track day at Goodwood next month, was going to fit the rockers to give it a bit extra lift.
Paul,
before you put the head back on, work out what the lift will be, fit one valve and spring. The n lay the head on ots sie in a biggish vice and compress the spring to the amount of maximum lift and measure the gap between the spring coils.
I always work on a minimum of 0.015" coil clearance at full lift. If you have double valve springs, so long as the outers have clearance the inners are usually OK as well.
I hope this helps. it sounds as though it will be a nice spec engine. 11:1 C.R. is good and the old 'A-series' does like high compression.
If you are running a dizzy you need to watch out for the static timing. At high C.R.'s I've had problems getting the engine to turn over on the starter when hot due to the high static timing at optimum max advance for high revs. To cure this I used a custom built dizzy (from Aldon) and a 560 CCA battery.
before you put the head back on, work out what the lift will be, fit one valve and spring. The n lay the head on ots sie in a biggish vice and compress the spring to the amount of maximum lift and measure the gap between the spring coils.
I always work on a minimum of 0.015" coil clearance at full lift. If you have double valve springs, so long as the outers have clearance the inners are usually OK as well.
I hope this helps. it sounds as though it will be a nice spec engine. 11:1 C.R. is good and the old 'A-series' does like high compression.
If you are running a dizzy you need to watch out for the static timing. At high C.R.'s I've had problems getting the engine to turn over on the starter when hot due to the high static timing at optimum max advance for high revs. To cure this I used a custom built dizzy (from Aldon) and a 560 CCA battery.
I will have a measure up, any idea what the lift is for a standard 1275 cam? could I do that once the head is on as if the rockers are going to cause a problem I’ll just use the standard ones until the engine come apart for the rebuild. I need to take the standard head off as it smoking quite badly, think the valve stem seals are a little worse for wear.
I have an electronic dizzy that Bill Richards modified for my 11:1 compression 1380, wondering if that might be better than the standard one.
I have an electronic dizzy that Bill Richards modified for my 11:1 compression 1380, wondering if that might be better than the standard one.
Paul,
Yes, you can do it with the head on, but use an old gasket as if the springs do bind, or get near to binding, you'll have to take the head off again and that scraps a gasket.
I recently changed the head on my 1293 cc rally car and when I built up the new head and put the new springs on I only had 0.006" coli clearance with the high-lift rockers. This was due to the head not having been machined down, although I thought it had (a momentary lapse of common sense i.e. forgot to check). I changed the springs and fitted standard lift rockers. Funnily it didn't seem to have reduced the power, so I'm staying with standard rockers now.
I think the lift is 0.318" at he valve with standard rockers, but that figure is for an MG METRO cam. I don't have the book with the numbers in at work.
Dont forget to check the comp ratio before you fit the head as what might be an 11:1 head on one engine could be completely different on another one.
The C.R. is affected by the distance down the bore to the piston crown, the piston dish capacity, the capacity of the engine (a head will give a lower C.R. the bigger the bore goes), and the volume of the combustion chamber in the head. I posted all the calculations on here a few weeks ago if you need them.
The electronic modded dizzy should be OK.
I hope this all helps. Good luck,
Peter
Yes, you can do it with the head on, but use an old gasket as if the springs do bind, or get near to binding, you'll have to take the head off again and that scraps a gasket.
I recently changed the head on my 1293 cc rally car and when I built up the new head and put the new springs on I only had 0.006" coli clearance with the high-lift rockers. This was due to the head not having been machined down, although I thought it had (a momentary lapse of common sense i.e. forgot to check). I changed the springs and fitted standard lift rockers. Funnily it didn't seem to have reduced the power, so I'm staying with standard rockers now.
I think the lift is 0.318" at he valve with standard rockers, but that figure is for an MG METRO cam. I don't have the book with the numbers in at work.
Dont forget to check the comp ratio before you fit the head as what might be an 11:1 head on one engine could be completely different on another one.
The C.R. is affected by the distance down the bore to the piston crown, the piston dish capacity, the capacity of the engine (a head will give a lower C.R. the bigger the bore goes), and the volume of the combustion chamber in the head. I posted all the calculations on here a few weeks ago if you need them.
The electronic modded dizzy should be OK.
I hope this all helps. Good luck,
Peter
Paul
If it's any consolation, I've got a Kent 276 with 1.5 rockers and Isky springs on my 1380. I had to change the springs from the ones fitted to my Cooper S pack conversion as they went coil-bound with 1.5 rockers. I think the lift at the valve with a 286 is getting damn close to 0.500", the 276 is about 0.450" I seem to remember. Even if you are convinced the springs are Isky, I think it pays to check.
I would agree with Peter on looking at your final compression, especially if the block has been "decked". You may find your waaaaay over on compression if the heads been skimmed to up the compression on a non-decked block.
I got around the timing problem by fitting a fully mappable ignition controller, extream but effective.
Let us know how you get on mate !! I used to live about 25 mins from Goodwood, but never got to drive the circuit there. Perhaps I'll make the journey south sometime !!
If it's any consolation, I've got a Kent 276 with 1.5 rockers and Isky springs on my 1380. I had to change the springs from the ones fitted to my Cooper S pack conversion as they went coil-bound with 1.5 rockers. I think the lift at the valve with a 286 is getting damn close to 0.500", the 276 is about 0.450" I seem to remember. Even if you are convinced the springs are Isky, I think it pays to check.
I would agree with Peter on looking at your final compression, especially if the block has been "decked". You may find your waaaaay over on compression if the heads been skimmed to up the compression on a non-decked block.
I got around the timing problem by fitting a fully mappable ignition controller, extream but effective.
Let us know how you get on mate !! I used to live about 25 mins from Goodwood, but never got to drive the circuit there. Perhaps I'll make the journey south sometime !!
The block is standard at the moment, the head was too much as originally came off a 1380 with big dished pistons so I’ve had the chambers opened out to give it a bit more volume, hoping it works well, its got huge ports and stainless race valve, I’ll check it all out when I get it on the engine.
The Goodwood day is fantastic value through the LSMOC, the full day for £40, its split into 15 minute sessions which is a bit short but at that price you can’t complain.
The Goodwood day is fantastic value through the LSMOC, the full day for £40, its split into 15 minute sessions which is a bit short but at that price you can’t complain.
plotloss said:
small hijack
Hows the build coming along Phil?
Last time I saw the pictures of the beautifully detailed subframe it looked amazing.
Finished now?
Errr, not me I'm afraid !! I think that was Sagalout ?? Although I am starting a new project based on a part-prepared Miglia shell..........
Not me either, haven't found out how to post pictures yet!
Probably not wise at the moment anyway yet. Car looks like a bomb hit it at the moment and so does my wallet now, after just getting the block back with new pistons, and buying a new cam/bearings/clutch. Bought that as a good running engine......still it's in the back of my 4 wheeled shed (Volvo740) and going home with me tonight. 1330 will be a little bit better than the old no compression 998. Shame the engine is now worth 3 times the rest of the car.
Have a good weekend all...
Tony H
Probably not wise at the moment anyway yet. Car looks like a bomb hit it at the moment and so does my wallet now, after just getting the block back with new pistons, and buying a new cam/bearings/clutch. Bought that as a good running engine......still it's in the back of my 4 wheeled shed (Volvo740) and going home with me tonight. 1330 will be a little bit better than the old no compression 998. Shame the engine is now worth 3 times the rest of the car.
Have a good weekend all...
Tony H
I've lost more than my marbles in that garage of mine...current panic is the little spring clip for the distributor cap. Most are about 30mm long & fixed to the distributor, the ones on my distribitor are about 15mm long and loose. Very loose....it went twang and that was that. Anyone got a spare?
Cheers
Cheers
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