Performance camshaft.... wont start!!!

[picky]

Just got my engine back together after replacing the standard camshaft with a kent cams 276 'road/rally' camshaft. Ive timed it in using an adjustable duplex timing chain, is there any way of checking whether I have the camshaft timing anywhere near correct? by looking at the rockers and the crankshaft postion etc
Please help!

[Alec]

Hello Picky,
a simple general check is to get number one cylinder to the firing position, and look at number seven and eight rocker. Now rotate the engine back and forward through top dead centre and you should see the seven and eight rockers 'rocking' i.e one closing and the other opening.
With symetrical cam timing and the cam correctly timed the lift on seven and eight should be equal at top dead centre.

Alec

[picky]

alec, wont that only apply to to an engine using the standard camshaft? as the timing on the new camshaft is likely to be different?? Also I have realized I have no power to the coil, dodgeyt wires or something, so it wont start until I sort that first!
Thanks for your help,
Tim

[Alec]

Hello Tim,

no, that is a general rule whatever the cam. Certainly there may be specific cams with assymetric timing which means that my statement of equal lift at TDC is not accurate.
However that is not the best way to time a cam, but merely a rule of thumb check. Follow the manufacturers recommendation as to setting which may involve a degree wheel or a dial indicator to achieve accuracy. Note that often the valve clearances are different for cam timing to basic running clearances.

Alec

[picky]

ive set the engine to no. 1 piston at TDC and the no. 4 piston has its inlet valve about half open.. when installing the cam I did use the supplied dial wheel, but I think I have probably set it incorrectly!!
also, the two wires leading to the coi, which way round should I have them? as it is negative earth it is supposed to be the other way round from the norm.. I have a black and white wire, and an only white wire. My coil is marked with '+' and '-'.
Thanks again!
Tim

[ColinP]

Picky,

I've just finished a major service - and of course the car didn't start (again).

My usual problem, I keep forgetting to where to put the insulated washer with the wires and the points....
(points, wire from points, live feed, insulating washer, nut) x 500 lines!

Any help?

Colin

[picky]

i simply removed the distributor, and replaced it, so my problem is unlikely to be points I think..

thanks anyway colin!

[Alec]

Hello Tim,
it sounds as though the cam is mistimed, remember to turn the engine in its normal direction when setting.
The coil polarity will not stop the engine running, but the white\black distributor wire should be on the - terminal and the white live feed onto the +. If the cam is incorrectly timed then the distributor will also be out of time.

Alec

[picky]

thanks alec, I will have to rething the camshaft timing, once I have it set, I can check that the no. 4 has its valves rocking, this should show that the timing is correct?
Tim

[bmcecosse]

This is where peeps get all confused trying to 'time in ' camshafts ! Just set it dot to dot - for anything but a full race engine that will be fine. Any tiny variation on that will amount to +/- 1 bhp - you won't even notice it ! And Alec is dead right about the lift at TDC - the inlet and exaust should be exactly the same amount lifted when rocking at TDC. This IS the correct way to time in a camshaft - equal lift on overlap at TDC. It minimises hydrocarbons being dragged down the exhaust - and should give the smoothest running (ie torque) at low/medium revs. Remember also to re-time your ignition since you have had the dizzy out. Start at TDC and advance until you hear it 'pinking' when accelerating hard in top gear - then retard it slightly. Ideally - you should fiddle with the advance curve to 'match' your fancy new cam.

[picky]

wel my 'fancy new cam' came with a 'fancy new' adjustable timing chain, so it doesnt have any dots to line up. I will line up the cam by looking at the rockers as suggested. I was also getting a little confused with the distributor.. loose wire to the coil
anyway ill have a go at the camshaft tommorrow, thanks everyone for their input...
Tim

[bmcecosse]

Good luck with it ! Must have cost a wee fortune - and I hope it came with a nice new oil pump - much more important than adjustable timing. What size engine is this for ?

[picky]

its in my 1098cc.. kent cam 276 megadyne with steel lightened adjustable duplex timing chain kit anyone good at guessing engine power outputs?? what am I likely to get from my engine after fitting the camshaft... at the moment I havea 12G295 ported head with 29/33mm valves, LCB and silencers by maniflow, HIF38 modified carb on minisport inlet manifold K&N air filter and lucas sports coil( its gold coloured it must make it go faster!!!) want to get a set of 1.5 ratio rockers next....
Tim

[picky]

Ok, so I got the timing cover off again and timed the camshaft in, it was about 90 degrees out put it back together and it works great!! getting a funny metal clicking noise though... only at tickover, it disapears when u rev the engine, put im not sure if thats just because you cant hear it above the exhaust...
thanks for everyones input
Tim

[bmcecosse]

Did you countersink the holes in the front plate and fit c/sunk screws? Also - last time I did this I realised the timing chain had slightly longer pins at the 'joining link' - and with these pointing fitted inwards they were still slightly catching the c/sunk screws. Chain turned round gave lots of clearance. Forget the high ratio rockers - these are a big sales gimmick - recently revealed (what I and others already suspected) on a Mini test as giving precisely 1 bhp more for huge cash outlay. They also stress the valve gear terribly causing wear and sometimes valve sticking !! Their only use is on HUGE engines (bored and stroked 1275 units) where there just is not enough valve area to feed the air in and so higher lift is the way to go. Your 276 MAY have a little better lift than standard - do they quote a figure ? 285/286 cams (the old BMC 544) ceratinly have more lift. Your engine will benefit greatly from a 12g940 head - and the 38 carb could be marginal - may be better with a 44. However - 1098 engines fall apart if run over 6000 rpm - so maybe better to keep the smaller carb and tune for torque rather than ulimate high revs power - it WILL break if you rev it !!

[picky]

I can remember the countersunk screws being very close to the chain.. maybe the slightly wider joining link is hitting them like you said.. ill check it out. about the carb I have modified it according to david vizard, so im hoping it will flow a bit better than standard and adding an unmodified 44 will not do much. I know the 12g940 has larger valves and better ports etc but I cudnt possibly afford a modified one, and the 12G295 head I have I got very cheap on ebay and it is well ported and also has larger valves, 29mm exhaust and 33mm inlet, so I dont know if I would get much from fitting a 12G940. anyone disagree with me?? I compared my standard camshaft with the 276 when I was fitting it, and the lobes seemed to be the same height, just in slightly different places.. so I dont think I have any more lift than before. IF I could get hold of a well sorted 12G940....

[Stig]

Forget the high ratio rockers - these are a big sales gimmick - recently revealed (what I and others already suspected) on a Mini test as giving precisely 1 bhp more for huge cash outlay.

Sorry, can't agree with that. They may be a waste on the Kent cam as it doubtless already has increased lift, but I've noticed quite an improvement in torque after fitting them to my 1098 with a standard cam. OK, I got them for free so no "huge cash outlay" but I'd recommend them as a bolt-on mod. Sure, a cam change may be better value for money but you have to have the engine out for that.

[picky]

I think that high ratio rockers are not just a bolt on mod, there are certain situations where they will show an improvement, but some engines where you get no extra power at all, particularly it seems on smaller engines. It is quite possible to replace the camshaft on a 1098 without removing the engine from the car. I found that by removing the radiator and the front grille you can pull the camshaft straight out of the front of the car and slide the new one in.

[bmcecosse]

In fact it can be squeezed through the grille bars ! But only if you know what kind of oil pump you have !! High ratio rockers usually cost ~£200 - NOT value for money power which on a recent Mini test was exposed as precisely 1 bhp. They also cause high wear on cam/cam followers/rocker bushes and shaft - and valve guides.

[Stig]

In fact it can be squeezed through the grille bars ! But only if you know what kind of oil pump you have !! High ratio rockers usually cost ~£200 - NOT value for money power which on a recent Mini test was exposed as precisely 1 bhp. They also cause high wear on cam/cam followers/rocker bushes and shaft - and valve guides.

Surely the wear on the valvetrain would be no worse than a cam with equivalent valve lift?

I'd be interested to read that Mini test, but £200 is indeedy a lot of cash which could be better spent on a head or cam with only a little more effort.

Just a thought about in-situ cam replacement, I assume you have to remove the followers via the side covers or they'd drop into the sump?