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MG MGB Technical - Camshaft timing
Camshaft 714, Engine 18V 847F, engine at TDC
Can anyone tell how to time in this shaft for street driving?
Have degree wheel and dial indicator
|110 degrees after TDC max lift on number one inlet valve|
|Chris at Octarine Services|
|Thank you Chris.|
For correct timing procedure: Fix the dial indicator on top of spring collar, set valve to rocker clearance 0.013in, then start rotating crank clockwise. OK?
If the reading is off some degrees, is an offset cam key or special timing sprocket required?
|Check the TDC mark is correct using a stop plug on No1 cylinder.|
|Take the reading straight off the top of the push rod (no clearance) for this setting. Denis|
Don't fit it, it is absolute rubbish performance, it was, we understand designed as a shale rally cam so the engine could rev without a sudden input of grunt. On SUs we see less bhp than a standard cam. You will wait for something to happen then all the engine will do is rev.
They were commonly used in standard B class racing, a modern standard lift race cam such as the Piper929 would leave the 714 for dead. If you want a mild road cam look at at 270 Piper cam and if you want more top end try a 285 Piper.
|Back 1900 and harrumph when I cammed my car I looked at some Oselli literature (printed in those pre-web days)and for UK road use the 270 fast road was the clear winner. Yes you could get more grunt with "road rally" cams but it was all up at max revs where you hardly ever use the car on the road. Where you did use it they had less torque as I imagine the valves were effectivley just pumping thr mixture straight through wirthout touching the sides. This is fascinating info Peter,a cam desingned for use on the gravel tuned to stop the back overtaking the front, I note this car is in Norway and maybe its to be used in competition on snow and ice?|
ps Im sure I could change to a newer fast road and see some inprovement, no intetion before I have to touch it though.
I'am an DIY-guy at 60. My driving is family mild street. I just want more hpower and noice when other drivers are teasing me. The car is not to be used in competition.
The engine and Sierra 5speed gearbox are to be fitted in an MGA-56 Roadster. (See picture)
The 714 cam is already in the engine, new tappets/lifters, head on block. Still I listen to Peter B and will remove it. Then, should I go for a new Piper270 cam?
|The MGA with its lower curbweight and profile drag makes a very fast road car with mild tuning. Peter will remember when Trish's car came up to Derby and had the Sierra box fitted with a longer first and then he put an econotune head on the 1588cc engine. It got good HP on the rolling road there and Trish reamains delighted with it. It easily keeps up with modern traffic, and runs on fresh air. The natter were delighted when her husbands AM Virage cooked its LSD on the way back from Le Mans, he is a big guy and had to fold himelf into the A to get home :-)|
The Piper HR270 is a lovely cam which pulls from idle and adds a little sparkle up to 5000 rpm, works well with a nice three angle seat tdy up head with cr around 9.75:1, the end result is how the engines should have left the Factory in the first place IMHO.
Are you still with me? I go for the HR270. The new 714 cam to be removed this christmas.
My engine: Imported from California. The original 1800 head with new valves is on the block, new tappets/lifters, HIF4 carbs, original MGA cast iron manifold. There is no room for a MGB manifold without modifications.
I hope the head will do. I think new tappets/lifters is a must. Can the 270 camshaft be timed in without a vernier timing gear set?
The engine has been testrun in the garage. I agree with you, the 714 was rubbish performance after so
many hours of work. Have to start all over again before I put the MGA body back on.
You can use offset keys to time the cam in, they are cheaper than verniers, it is best to buy a billet camshaft. Seven out of ten billet cams are correct on the dots. You will need new cam followers.
I go for the billet cam of your advice. My wife Christmas gift.
Can you give the total price, shipment to Norway included.
I hope to remove old cam and install the new one without first having to remove oil pump/drive spindle, only the distributor spindle?
We would charge £180 for the cam and late style followers (18v) if you need later longer pushrods to match they are £2 each. Delivery to Norway by BusinessPost would be £30 insured.
How/where do I order?
Send me an email just to remind me, then when we are back at work (4th Jan)we can sort out the order for you.
|Peter, a final problem:|
Don't have your mailaddress.
It is email@example.com
|Me too is looking for a camshaft to install in my 18V engine. So this post is not about timing in a cam, rather a hint of how to find the best suitable camshaft for my needs. This is what I have learned:|
Wild or "race" cams are just not suitable for a road car. They do not allow you to drive smoothly in say 4th gear in town because they make your engine run "lumpy" at low revs! And you will have an uneven idle like a bike engine.
They can give some performance benefit at higher revs though, but only if the rest of your engine and induction system and exhaust are also modified to take advantage! If not, the extra valve o "overlap" makes them sensitive to exhaust back pressure and your car may well be slower! Valve overlap happens when your engines inlet valve opens whilst the exhaust valve is still open. This aids airflow at high engine rpms.
On the other hand, if you have just spent a fortune building a "big valve" race engine with lightened and balanced internals etc it would be stupid to fit a standard camshaft, as most of your hard work would be wasted! Like everything in life it has to be a balance. So its best to know what you are looking for and plan for that! Its no use just putting a few go faster bits on your car and hoping! That does not just apply to camshafts but to the complete engine. All the bits need to be matched and work together! You must have a plan before you start.
Description of some cam types (very general) :
smooth, long lasting, good emissions, good economy, good low down power for smooth easy driving in traffic. The main manufacturers are not stupid! Think carefully before you decide on a "race" cam. Power falls away at higher rpms.
-Towing, mild, or whatever:
these will give good economy and will work much like the manufacturers stock cams. Standard lift and duration usually expected top, give more torque than stock ones at low rpms, smooth tick over.
Usually works ok with stock head/valves and a good free flow exhaust system, and bigger better multi carbs. These will give a higher RPM peak power than stock and usually at the expense of some low down power. Remember that low down power is where you spend the most time in a road car. Usually a touch more lift and duration (about 260 / 270 degrees) Slightly lumpy idle in some cases. Gas flowed head and bigger valves helps if you can afford to do it, but generally not essential.
If you want to read more just visit:
There are lots of aftermarket Camshaft manufacturers to choose from.
Many drivers talk about Piper cams, like the above Guru Mr Peter Burgess. Yes, I think I will go for one of these Piper cams:
-BP255 Mild road / automatic profile - stage 1
This cam is a straight forward installation with no modifications or additional parts required in order to use this profile. This is the first level of cam tuning used where high torque is required for towing / touring. (Approx 255 ° duration)
-BP270 Fast road profile - stage 2
This cam is a straight forward installation with none to light modification and parts needed depending on vehicle. Generally referred to as the stage 2 of cam tuning this profile performs well when used in conjunction with other stage 2 tuning products such as free flow exhaust systems and remaps, giving a good torque and power increase in road cars. (Approx 270 ° duration)
The Piper HR270 we use would have been 'just right' for a B if the Factory had fitted it in the first place, nice idle and sweet power delivery. If you are going to use revs above 4800 I would look at a Piper HR285, purposeful Idle note, as they say, then pulls nicely from 1100 rpm, no kangarooing at low rpms you might associate with a 'Hairy' cam
|Speaking of cam timing, someone elsewhere has been asking about how you measure it, e.g. do the valve clearances have to be at the specified running values, no clearance at all, or some other clearance? Despite lots of 'advice' no one has come up with the answer to his initial question. Looking round I found a page that gives information for midget engines for example, which states the clearances must be set larger than normal for checking the cam timing, and the clearance is different for each size of engine! I also found another page for MGA/MGB engines that gave three different sets of figures - one from the Workshop Manual, one for the position of peak lift, and one for the number of degrees when each valve has .05" of lift during opening and closing. Only the point of peak lift rules valve clearance out of the equation, but that still doesn't tell you when the valve starts to open or is fully closed, and valve clearances weren't mentioned at all.|
Me too, like stk, will go for the Piper270 camshaft.
Agree with PaulH, so far he is the only one with an answer to this thread initial question. I hope several of you out there will continue this cam timing thread.
Happy New Year Driving!
I think Chris answered the question by saying time the 714 cam in at 110 degrees. It doesnt matter what the lift is at TDC or whether the effects of clearance are taken into account the cam should reach max lift (unspecified amount) at 110 degrees after TDC on the inlet valve. How to actually determine the points with a dial gauge and a protractor are well documented on the web.
The different ways of determining durations are mind boggling which is why I reckon it is impossible to work out what a cam will do from basic figures, one needs more info and advice. The figures never mention tappet velocity or acceleration rates.
|Sorry, Chris at Octarine Services, course you were the very first one to answer the timing question....|
and newbies like me, start with reading P. Burgess book: "How to Power Tune MGB 4-Cylinder Engines"
This thread was discussed between 16/12/2010 and 02/01/2011
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