Valve clearance+timing.help

[john.houston]

Hi. I am coming to the tricky bits on my rebuild.The shell is in primer ,the chassis is built up now awaiting the engine.
I bought the car complete, but with the head off ,having had the waterways TIG welded,and a skim,previously having new seats ,guides and valves fitted.
All parts were numbered and went back a treat. But I found that all the shims were out by + .010 thou I have to assume that all the seats were re-cut (i just don't know) ,.The smallest was 0.085 but this will now be 0.075. All the rest are over .083 .
I have been told 0.080 is the safe limit so Q... Do I have .005 taken of the valve stem (hard to get done as a single job and not a DIY job with a stone or bench grinder).Or do I leave it and worry. and why do they sell 0.065 shims???.

Next .The sprockets came with offset dowels.Q.Is there a set way they go, either the offset to the left or to the right. This might save me spending lots of time with a DTI and cardboard disc etc .

Why doesn't this site have a shim bank I would happily send my old shims to one.
Once again thanks for any help you give. John.

[ncm]

Hi John, Wilkins' twincam book gives 0.060" as minimum shim size so you will not need to shorten the valve. What cams are in the engine?If they are a standard Lotus profile you shouldn't need offset dowels ( unless you are using a 1600 block...)
Cheers , Brian.

[rgh0]

Offset dowels can go both ways depending on what setting is needed. The dowels cover half the gap between each tooth. Set one way and you retard the cam up to half a tooth set the other and you advance it up to half a tooth. If you get to half the gap and the timing is still not right then you move than cam one tooth and start again.

While 60 thou shims are generally OK it is worth checking the top of the retainer to the bottom of the bucket clearance when you get to these sizes of shims as depending on the valve, retainer and bucket components they can sometimes clash if the shim is down around 60 thou.

The other problem with thin shims is that they can sometimes crack but this is an unusual problem with 60 thou shims and probably relates to them being hardened totally through by accident due to poor heat treatment control

regards
Rohan

[steveww]

IMHO throw away the offset dowels and get some adjust able sprockets and set the valve timing properly with a dial gauge and a degree wheel.

The shim bank is a good idea, I already have a bag full of various sizes.

[kenny]

I believe Johns engine has the standard se cam on inlet and a cam of "unknown identity" on exhaust. If the exhaust cam is identified as standard could we not just revert to standard straight dowel sprockets.?
I'm not sure it is a different cam to standard profile until measured/checked out! if it is then timing figures will be needed.

I agree with the vernier route for bigger cams but what is the concensus here for using these with a standard motor?
Surely setting up on crank tdc mark and aligning sprocket marks suffices.

I ask these questions as we're both at the same stage of rebuild.

Kenny

PS Shim bank = Great idea, But ferfuksakes don't let John be the banker

[rgh0]

If everything else is standard then using the cam timing marks for a road engine is probably near enough. However almost all Lotus engine these days are not standard in terms of things like head thickness, block height, camshaft profile (even standard cams may have been reground that may have moved thier timing a little) all which can put the standard timing marks off.

Whether you use offset dowels versus vernier sprockets is really a personal preference. Vernier cams are more expensive but easier offset dowels cheaper and not much harder to use especially if you have a number of engines to do and are experienced at timing them.

regards
Rohan

[ncm]

Whatever you decide to do , do it on the bench..it is sooo much easier than with the motor in the car!

[andyhodg]

John

I had a problem in achieving adquate clearances when fitting a re-built head (new seats and valves) I couldn't get shims thin enough to give the correct clearance. I ended up replacing the follwer buckets with lightweight ones which QED supplied. This then allowed me to use "standard" shim thicknesses.

Good luck

Andy

[john.houston]

Thanks for the fast replies.The P.O was a keen engine man so I will get the D.T.I out and spend some time getting the offsets back to where they were originaly.
Rohan if you tell me I am O.k. with one shim only at 0.075 I will order the shims and never worry again. I need you to say "it's O.K John."please.
As Kenny said the Exhaust cam is an" unknown ".
Looks like Kenny has sacked me before I even wrote my C.V for the Shim Bank Manager

Thanks again.

[steveww]

QED do some very nice adjustable cam sprockets. It really is a lot easier with these IIRC they are ?100 for the pair. BTW they also make getting the cams in/out when re-shimming a lot easier.

[miked]

Guys,

while you are talking about adjustable sprockets, I have just fitted some. Not done the fine tune yet. They are from QED with the 6 allen studs. Do you use loctite on the threads when you have set them up or am I being paranoid.

Thanks Mike

[john.p.clegg]

Mike
no need for locktite,mine have been OK without for years,but,please be careful when adjusting in-situ as if you drop one of the buggers down the timimg chest it's not easy to retrieve....

John

[steveww]

Don't use thread lock on mine, I just torque them up to 10ftlbs.

[rgh0]

John

It's OK with a shim at 75 thou --- unless you have some strange retainers or valves or buckets. I cant guarrantee it without measuring up all the components and checking the clearances and assembly but if your using standard components in the rest of the valve gear -- its OK.

Photo of a broken 60 thou shim I took out of an engine attached, I never did find the other half it must have gone out in an oil change at some time I guess. Just made me nervous about going to thin on shims but I have never seen a broken 75 thou shim --- so its OK

cheers
Rohan

[Bruce Crowthorne]

So any volunteers for a "shim librarian"?
I have a set of eight that I will donate.
Bruce