Hi,

I'm getting really frustrated with a cam I bought recently for my Kent 1600, it was supposed to be a Cosworth A2 profile but I'm not sure what it is because it certainly doesn't seem to match up with any of the A2 specs.

I fit the cam and dialled it in to 108 degrees at full lift but can't turn it over by hand, pistons hitting valves, then I tried to set it up with the inlet valve opening at 40 degrees BTDC ,still no joy.

In desperation I lines up the cam markers but the figures I get are totally whacky......

Is anyone able to help me work out what the hell this cam is ????

These figures are with the cam markers lined up....

Inlet cam lift 6.18mm
Opens 66 BTDC
Full Lift at 12 BBDC
Fully closed at 60 ATDC

Exhaust cam lift 6.18mm
Opens 74 ATDC
Full Lift at 45 BTDC
Fully closed at 60 ATDC.


Along the same lines I'm getting a bit confused with cam specs....

- I assume that when duration is specified this is cam and not crank duration ?
- Timing the cam at 108 degrees means 108 degrees ATDC ?
- On cam specs the close timing degree is the time the valve is fully closed and not when it starts to close.....

Please help.....going nuts here trying to work it out.......

You can't use seat to seat timing figures because no one actually uses fully seated. It could be 0.006" off the valve or cam to something like 0.009" off the cam.

You are best off picking a "set" lift point, a common standard is 0.050", thats 1.27mm. Use something around there.

Find the opening and closing point, add 180 then divide by 2.

You also can't use the full lift position either because the reading may dwell for a few degrees on the direction change.

Otherwise look up youtube there should be a video there.

May not be a cam problem either. Maybe you just don't have enough piston/valve clearance to suit that cam. Was the rest of the engine built to factor in that cam?

Woz

That's what has got me a bit confused, a Cosworth A2 should fit into a stock motor
But none of the timing seems to match up. I would be happy if I could work
Out what it is and then I can work out what sort of valve pockets I need if at all.

quote:

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Originally posted by harrier

That's what has got me a bit confused, a Cosworth A2 should fit into a stock motor
But none of the timing seems to match up. I would be happy if I could work
Out what it is and then I can work out what sort of valve pockets I need if at all.

---

The lift you stated at 6.18mm is only about 0.17mm more than a GT cam so should definately fit without machining. From what I can gather you should be able to fit a cam with lift of about 6.7mm before you need to machine valve pockets unless the head has been shaved a fair bit. Sorry I can't help with the timing issues but check out this website for some hints...

http://www.tighecams.com.au/helpful-hints.htm

Did you fit roller rockers? These often have different ratios to standard (people use Holden 6 rockers on V6 capris which are 1.55 instead of 1.5) etc etc

What Kent engine are you using (681F; 711M etc)? What pistons have you used? I've got a 711M (1600) with an A2 cam and it was not necessary to deepen the valve pockets in the 1600 Hepolite pistons for that engine. The A2 is not much more radical than the Ford GT spec cam.

quote:

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Originally posted by Batman105E

quote:

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Originally posted by harrier

That's what has got me a bit confused, a Cosworth A2 should fit into a stock motor
But none of the timing seems to match up. I would be happy if I could work
Out what it is and then I can work out what sort of valve pockets I need if at all.

---

The lift you stated at 6.18mm is only about 0.17mm more than a GT cam so should definately fit without machining. From what I can gather you should be able to fit a cam with lift of about 6.7mm before you need to machine valve pockets unless the head has been shaved a fair bit. Sorry I can't help with the timing issues but check out this website for some hints...

http://www.tighecams.com.au/helpful-hints.htm

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It depends totally on what pistons are fitted, and what cylinder head is fitted.

I would suggest to use the "lift at tdc" method of dialling the camshaft.

Basic rule of thumb, lift even on inlet and exhaust @ 2 deg before TDC on the over lap stroke.

Whilst the A2 profile doesn't have a lot more lift than the GT grind it has alot more timing which means more lift at TDC which may create problems depending on your piston/head combo.

Woz

This forum rocks!!!!!

Thanks for the advice and pointers, the cam timing make a a load of sense now. I dialed the cam in with the 'lift @ TDC' method and rechecked the timing figure as people suggested and it matches up perfectly as the A2 Cosworth profile it is supposed to be. The car fired up first go and runs like a treat. I'm not using roller rockers and its the 711 block.

I was looking for the A2 just to give the car a bit of a note but still have it drivable as a daily driver.

Thanks again for all the advice, its been a great learning exercise as well, I just wish I posted to the forum before I spent a couple of days pulling my hair out trying to work it out.

I'm chalking this one up as a step in the home mechanic apprenticeship