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#1 adam c

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Posted 07 June 2004 - 07:21 PM

Sorry to start so many threads but...
Hopefully i will be putting all the bits of my engine back together in the next week or two and as pretty much everything will have been reconditoned is it worth doing anything to the timing while its stipped down??
Any advantages of duplex?
Is it difficult to fit duplex?? Do i need a new timing cover?
Whats the pupose of adjustable timing, surely its factory set correctly or have i missed something when reading how to align the timing gears when refitting??
Cheers guys...

#2 dklawson

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Posted 07 June 2004 - 09:10 PM

The duplex should fit without too much effort. You'll likely have to countersink the holes that attach the front plate to the block to accept flat-head screws. (The old hex head bolts will foul the sprocket). Duplex chains are stronger, but duplex pulleys don't have the rubber inserts that "try" to maintain tension. It's a trade off I guess, but the duplex are generally considered stronger and less subject to stretch. There are also multiple grades of duplex pulleys out there ranging from cheap, solid sprockets to lightened adjustable ones.

#3 Turbo Phil

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Posted 07 June 2004 - 09:30 PM

Lining the sprockets up using the "dot to dot" method is marginal to say the least. Timing the cam in accuratley is essential if the engine is to produce it's full power potential, even more so when a "performance" cam is installed.
If you can't afford a vernier set, then use offset keys to get the correct timing.

Phil. :grin:

#4 siggy

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Posted 07 June 2004 - 10:19 PM

As Phil says its a very basic setting and can be many degrees out.

As a comparison when I worked in a Ford dealer we used to get many cvh engine fords in running rough especially after they had had Unlead conversions (a simple adjustment of the ignition timing) In almost all cases what had happend was whoever reset the timing. connected the light up and adusted the light to the rcomended 8 deg in place of the standard 12 deg.
What you were actually meant to do was connect the timing light and then see what the light said the timing was, in practice this varied from 0 deg to 20 deg, then retard the timing by 4 degs. ie if the timing was 17 deg set it to 13 deg.



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#5 Wil_h

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Posted 08 June 2004 - 06:00 AM

I can't see any comparison between cam timing and ignition timing.

I don't know what engine you're putting to gether, but unless it's an absolute monster spending all its time at 7000rpm I wouldn't bother fitting a duplex. The later simplex chain with the tentioner (correctly) fitted is fine.

I've never used a duplex (mainly to save weight) and have never had a problem. I now use a belt drive but only because I was given it for nowt.

It is worth timing it in properly though. as mentioned using an off-set key.

Wil

#6 siggy

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Posted 08 June 2004 - 07:15 AM

Its simple the comparison is the fact that mass production tolerences can be a wayouy.
The acuracy of cam timing and ignion timing is controlled by the machining of keyways, pulleys

Get it now?

Sorry if it was not too clear

Siggy

#7 adam c

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Posted 08 June 2004 - 11:48 AM

Yeah i was thinking along the lines that the timing chain drives the cam which then drives the dizzy so if the chain is out then both the ignition and the valve timing will be out. How do i set/check them timing then??
Cheers...i think adjustable timinig is out of my budget and am using a standard cam so may stick with the simplex...unless anyones selling an adjustable set up??
Thanks for the advice :D ...

#8 dklawson

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Posted 08 June 2004 - 01:09 PM

Don't worry about variable pulleys being out of your budget. Regardless of what timing chain you finally choose, you can buy offset keys to set the valve timing. AFTER you've measured the valve angle you order the one key you need and you're done. Figure about 3 GBP.

#9 Bluemini

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Posted 08 June 2004 - 05:04 PM

For your engine and budget, standard simplex will be fine. I ran Old Blue at 80-odd bhp with a simplex chain and never had any problems.
The only thing I would recomend is that you buy a new chain and tensioner pad. The cahins stretch and the pads wear, and both are very cheap.

I would only fit an adjustable chain or belt kit if I was fitting an aftermarket cam, or after every last ounce of power from the engine.

#10 adam c

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Posted 08 June 2004 - 06:51 PM

Thanks..
The tensioner snapped in half when i was taking the pulleys off and was well worn anyway. Think the chains are only about 4 quid so i'll get one of those too, i presume i should replace the tensioner rings at the same time and then hopefully should be OK. Think i'll also get new cam followers as i don't have the followers to go with the cam i'm using so its probably a good idea....

Just out of interest do they use offset keys when the engines were originally built or is the timing on standard engines always out??

#11 dklawson

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Posted 08 June 2004 - 09:20 PM

I'm pretty certain that only standard keys were used at the factory. Proper selection of the offset keys requires measuring, disassembling and reassembling the timing components. This would cost too much on an assembly line.

#12 siggy

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Posted 08 June 2004 - 09:34 PM

Just standard keys, adjusting the valve timing with off set keys would cost too much

Siggy

#13 adam c

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Posted 09 June 2004 - 07:55 PM

Ahhh.... so theoretically a 3 quid offset key could make my engine more powerful than a standard one!!
Hopefully i'll be gettin the engine back together soon so i'll soon see what shes gonna run like - after all this is the first car engine i've ever rebuilt :D
Thanks guys....

#14 Bluemini

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Posted 09 June 2004 - 08:42 PM

theoretically a 3 quid offset key could make my engine more powerful

I wouldnt count on it, 3* could throw the timing miles out, just leave it as standard.

The tensioner rings you say about, are they the ones on the cam sproket? If so, dont get new ones jus use the spoket of a later engine. If you have a tensioner pad you dont need the rubber tensioner ring too.

#15 dklawson

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Posted 09 June 2004 - 09:17 PM

I thought the tensioner pads were only on the A+ engines? Did later A series engines switch to this arrangement and do away with the rubber rings in the pulley?

I think the "3" Adam is talking about is the guess I made for the cost of the offset keys in the U.K.... not the amount of offset. Since you select the number of degrees of offset you need based on measurements... it won't be "out" it would be spot on. If your old stock arrangement was WAY out this could make more power for you but realistically, with a stock cam and no changes to the combustion chambers or ports it may only slightly improve the power you had.




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