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Hello all, ive got a 1293 engine fitted with a leyland 648 camshaft fitted, I bought the engine off the shelf so to speak so didnt check it as I should of prior to fitting,
As such ive had a few issues such as :
Difficulty starting particularly when cold
Poor performance, the car doesnt want to rev
Lower than expected compression

Ive checked cam timing and found it to be 11 degrees retarded from the figure listed for the cam,
Are the problems ive been having symptomatic retarded cam timing

Thanks

Possibly - More than likely installed one tooth wrong on the sprocket...
... should be easy to fix, though!

If you know it's wrong, you might as well try fixing it.
If you "fix" it and it runs better, you will have your answer for definite.
If you "fix" it and it's worse, there will be some ADDITIONAL problem
that needs looking at as well.

Anything over a couple of degrees out will be detrimental.

Ian

I agree with what Ian's already said.

There could well be other issues, but as this one has been found, start with that.

Correct factory advice on this Cam is that it should be timing in at full lift on No. 1 Inlet at 100 degrees ATDC. I'd also strongly recommend you check too that the Inlets aren't going to kiss the pistons when you've reset the cam timing.

Also - and just my view - it's not a street-able cam, though I know some guys do use them (or similar grinds) in street cars. It wouldn't come 'on' the cam until you get to around 4000 RPM, below that, there will be much less power than you'd get from a 'lesser' cam. Though, I'm not sure what type of car you have it fitted to.

So, you'd really need a low FD as well, probably something around the 3.9 to 4.2 range.

And as the Power band will be narrow, you'd also likely need close ratio gears.

Personally, I think / feel and from my own experience, a 643 is about as far as you can sensibly go for the street.

Its for a historic rally build, currently running with a sccr box and 3:765 fd, cam timing currently at 111 degrees atdc so I will be changing it to 100, whats the best way of checking the valves arent touching the pistons?

hmm

my 1430 in the er' runs a 649 on twin 1 1/2's and a 3.4:1 and its fine on the road

it will 'bog' in third if the revs drop below, say, 2000, but it just chugs a while until it clears its self (im too lazy to change down to try and help it! - bar that its just not an issue.. it does have the super heavy flywheel of a 1300, so that inertia maybe helps it a lot

I would agree that 11 degrees sounds like the builder has got the cam wheel a tooth out - easy to do if your squinting at the dots and shuffling the gears back onto the shafts

Assuming you have the head off, Put some Plasticine (or Blue-tac) on to the crown of No. 1 piston, then wipe some oil over that (so it doesn't stick to the head / valves), set the pistons to around mid-stroke,fit the head on with an old gasket (or even no gasket), fit the push rod in for No. 1 Inlet, initially set the tappet clearance by feel is good enough, give it some extra (say even a couple of mm), SLOWLY wind it over by hand while looking in through the spark plug hole, at the right angle you'll be able to see the Valve opening and the head of the valve, keep winding over slow while watching and feeling if it wants to stop or if there's any interference. If all looks good, set the tappet clearance for real and go again.

With the rings on, this can be a bit hard to feel for, I usually do it at the dry build stage, then you're not fighting the rings and you can really feel everything.

By doing this check without a gasket, that will give that added margin when done for real.

If you have a vernier timing gear set, you can set the timing to say 105 degrees and check what clearance you have there and that will guide you if there will likely be issues. At 105 degrees, you will be 'safe' but when you start getting down to around 102 - 103 degrees, especially with a cam like that that opens so early, then check check check.

If you find you have clearance but is close, best check all cylinders as there will likely be some variation between them.

Apart from the long duration, early opening of the cam itself, you need to get the CR up which can compound the issue of valves kissing the pistons as you'll likely have the pistons flush or coming out of the deck and / or shaved the head, and with each of these steps, bringing the valves and pistons ever so closer together.

Given your build, if 97 Octane Fuels (or better) are available and permitted to be used, I'd be aiming for a Dynamic Compression Ratio of 8.8 - 8.9:1, which without crunching the numbers, would likely be in the region of 12.5 to 13.5:1 SCR. A low CR will make it hard to start. You may also find you'll need to fit a hotter plug to start it and warm it up a bit then fit cooler plugs for the runs.

Also, and this is just my thoughts, if it were me, I'd probably be more inclined to reach for a 643 for Rally work along with a 4.1 Diff. If I were to go for a 648, then 4.3 or a custom FD at around 4.5 or 4.7:1. Top end speeds generally peak at around 80 mph (though there maybe the odd one that will get to 100) so, if it were me, I'd start on paper from that and work back to see if the other end of the spectrum will also be satisfactory.

Sounds great build.

Rich - sure, a 1430 will come on at lower revs and almost getting into that streetable region

Thanks for that , ill definitely check, when fitting the head to check does it need to be torqued down, thanks

No need to torque the head down, however be sure to use an old gasket (or no gasket for a safety margin). For that matter, it can be advantageous to swap out the valve spring for a much lighter spring, something you can easily push down with your finger, then you wouldn't need to even fasten the head at all. With the lighter spring, as the piston gets near TDC and begins to fall away, you can also lightly open the valve with your finger, go so you can feel what clearances you are getting and stop the process if it's getting silly. By not fastening the head, it will greatly reduce the risk of and damage to the piston and valve if they do kiss as the head will start to lift.