9 replies to this topic

[Pigeonto]

I am changing to a duplex chain and am wondering what the general thought is on a tensioner. I have been told that one can use the single chain tensioner but I offered it up and it runs on the 2 inner plates of the double chain and I reckoned it would soon wear grooves in it and all the material would end up in the sump!Lots of you must run these so what is the thing to do? Also Mr. ecosse once posted a fairly idiot proof way of checking cam timing which seemed very good but I cant find it, I remember you have end up with a large valve gap after turning one revolution if that reminds anyone? Would be nice to read it again.

[Ouster]

It's not essential to have on a duplex chain, especially if you're seeing high revs often.

[mk1leg]

you do not need the tensioner.................but you must countersink the 2 bottom holes where small gear slips onto crank ...............

[Pigeonto]

you do not need the tensioner.................but you must countersink the 2 bottom holes where small gear slips onto crank ...............

Ah, I hadnt considered not even using one,am happy to do so if thats normal,just didnt want the annoying rattle. I'm not intending high revs but the double springs which were recommended with the 1.5 rockers worried me,being 180 Lb so thats why I decided on the duplex.Ps thanks for the csk bit but sussed that and have done it

Edited by PIGEONTO, 18 February 2010 - 09:01 PM.

[bmcecosse]

Well - I tried a tensioner on a duplex - and as you feared it soon broke up and made a fearful racket. It really should not be necessary. As for these strong springs - if not planning high revs - remove the inners. I'm not in favour of the 1.5 rockers either - but it's up to you!
As for the timing check - at TDC the cylinder NOT firing should have both valves held slightly open by exactly the SAME amount. This is the overlap at TDC. If you have a dial gauge - you can use it to measure this - of course you need to get TDC precisely - chop stick down the spark plug hole works quite well! If no dial gauge - set the engine as above - then wind the two valves in question up on the rocker adjustment until you get a gap of say 10 thou on each valve. Then turn the engine one full rev - and now measure the gaps at each valve. They should be the same - at maybe 50 or 60 thou - the actual value doesn't matter - just that they are the same. If not same within a very few thou - then the cam is off the design timing. That's not to say it won't run well - some engine set-ups prefer the cam slightly advanced - some retarded - it just depends whether you want ultimate peak power - or a better spread of power at lower revs.
Obviously after doing this check - you will need to reset these valve gaps back to normal!

Edited by bmcecosse, 18 February 2010 - 09:15 PM.

[samsfern]

ive built a few a series engines, and never used a tensioner when using duplex gears.

[Pigeonto]

ive built a few a series engines, and never used a tensioner when using duplex gears.

I think that decides it:- I wont use anything. thanks bmc, I knew I was risking your wrath! but I should add this is a std HLE cam not high lift so I may be forgiven?

[bmcecosse]

It's up to you mate! It's your engine - enjoy. But I suspect the HLE has the very soft/low lift economy cam. An MG metro cam would make a world of difference!

Edited by bmcecosse, 18 February 2010 - 09:52 PM.

[Mei]

Someone the other day told me, it's not necessary to even put those two screws that have to be counter sunk back in, as the rest of the bolts will hold the front plate on....
anyone got any confirmation on this?

[Pigeonto]

It's up to you mate! It's your engine - enjoy. But I suspect the HLE has the very soft/low lift economy cam. An MG metro cam would make a world of difference!

That is all to come! At moment I am fitting a "temporary" engine I aquired from HLE 1275 metro while I completely build up my 1275 into a +60 or even 80. I didnt want to separate the engine from box on this temp. one so am just doing external things -rockers,Lcb,1 3/4 system, ported,10:1,hope for a good result while I slowly do the big job on my project engine. I suppose i could have found a used MG cam and turned engine upside down and fitted it,never mind that would be using old followers but I've got to save myself for when I get it all done and THEN enjoy better cam!Then go back to 1.3 rockers. I reckon youre right about this cam, with 1.5s I get 360 thou total lift, but if you remember a few weeks back I asked how they got 63 hp from HLE oppposed to 50 from my Mayfair and you suggested slightly better cam + other things. Cheers mate, may pm you when its in to report!