Still pulling hair- Twin Cam timing marks. How accurate?

[john.p.clegg]

Bill

Totally agree but with ref to step 2, take measurements at approx 90 BTDC and ATDC with a calibrated "stick" down the plughole to give less angular error when setting timing disk?

John

[Craig Elliott]

Mark, at risk of sounding like a stuck record (I've said this in other posts), what fuel/additives are you using?

C

[M.J.S]

Mark, at risk of sounding like a stuck record (I've said this in other posts), what fuel/additives are you using?

C

Hi Craig,

The car has an inline POWERPLUS FUEL ENHANCER, which is supposed to allow an old engine to run unleaded without mods.

http://www.powerplus-fuel-technology.com

Recently I have added castrol Valvemaster to the 97ron superunleaded I always use, to be on the safe side.

As a precaution when looking for the fault I removed the PowerPlus to check it wasn't blocked or at fault, but it made no difference to the running.

I have just taken a look at the fuel pump when I had the carbs off, and it looks like virtually new to me from its shiny screws and new gasket, and looking through the fuel filter there seems to be no problem with fuel supply.

Mark.

[kstrutt11]

Mark,

I assume all you are looking for is to get it running reasonably well, in which case the factory marks should be fine.

My +2S130 has done 40,000miles and the timing chain is at the end of it's adjustment (job for this winter), yet it reliably returns 35mpg and pulls well the only pops and bangs are in the exhaust on overun which I believe is pretty normal, it also has between 180 and 190 psi in each cylinder and the chain timing marks don't align any better than yours.

If I were you I would check basics first.

1. Check the timing marks on the crank pulley are correct (it is possible to fit Ford pulleys) using a piece of dowel in no 1 cyclinder, idealy you should use a dial gauge equaly about TDC but a pointer and a pencil mark will be enough to check if anything is massively wrong

2. check you have the right cam sprockets on the right cams (inlet and exhaust are different)

3. Check it has standard Lotus cams and not some other aftermarket item which needs to be timed differently.

4. If these are ok then I don't believe there is anything too wrong with your cam timing.

5. Next I would check the valve clearances. (if it does not rattle when hot I would be suspicious because when the clearances are correct they usually are a little rattly). It's all to easy to get metric and imperial mixed up and end up with half the specified clearance.

6 get your compresion gauge checked (or test it on another vehicle)

7. Try repeating the compression test with oil in the bore, if it increases you have a leak past the piston (probably glazed bores).


If all this fails get back to us and we can have a another go!!


Kevin +2S130.

[hatman]

I thought I'd cracked it until I tightened the tensioner and settled everything back in, to find that when the top lined up it threw the bottom out by approx 5 degrees.

That's because when you re-fitted the chain to the cam sprockets after lining up the marks you had the left side (looking from the front of the car) run of chain tight so that when you re-tightened the adjuster screw to take up the slack (which must have been on the righthand side) the tensioning of the chain then pulled the two cam sprockets back to your left (if you can follow all the lefts and rights!) putting them out of kilter with the crankshaft. Or would you rather be a fish?

[andyelan]

I think what hatman is saying is, that looking from the front, the engine rotates clockwise. Therefore when setting the valve timing you always need to turn the engine in that direction and keep the chain run from crank to exhaust pully to inlet pully tight. The tensioner shouldn't have any effect as it's on the slack side of the chain.

Having said all that, your timing doesn't too bad, it's no worse than my car which runs fine.

The problem with this sort thing is it's so easy to start second guessing yourself. You have to trust that once you've checked somthing and found it OK, it is indeed OK. That said I'm really running out of anything else to suggest.

I known its obvious but, you made sure you have the sparkplug leads in the correct order and also made sure that you haven't move the distributor drive shaft out of position when doing the valve timing and got the ignition timing all messed up. Just a thought

Andy

[bill308]

Thank you John. You wrote:

"Bill

Totally agree but with ref to step 2, take measurements at approx 90 BTDC and ATDC with a calibrated "stick" down the plughole to give less angular error when setting timing disk?

John"

You are correct. These are the most accurate positions to make the measurements to determine true TDC. A further refinement is approach the 3 and 9 oclock positions from the BDC location, first going clockwise to the 9 oclock position then counter clockwise through BDC to the 3 oclock position. This practice negates any bearing clearance issues and is the only time it makes sense to reverse engine rotation to take a measurement.

All timing events, cam and ignition, must always be measured in the normal engine rotation direction.

Bill

[M.J.S]

Hello everyone. Been a while since my last desperate post. She has been off road 5 weeks while i have been on holiday and have been Trying to sort problem.

After a Lotus expert suggested the cam timing was out, probably since PO rebuild 4 yrs ago, if you remember when I posted photo it was difficult to tell. Marks appeared to line up but were below level of head casting.

In desperation and unsure whether to alter them or not, I took off head to check it on bench.

This also allowed for a decoke and a couple of noisy tappets to be sorted.

Once on the bench to my disbelief, to line the marks up as in the workshop manual, with the marks level with the head casting, I had to turn the inlet back one tooth and the exhaust forward one tooth.

2 teeth out.

Once the head was rebuilt and back on it was impossible to get all 3 timing marks perfect. In the end after trying every position possible, the best compromise was the two cam pulleys absolutely spot on and the crank pulley approx 7 degrees out. To get the crank dead on TDC meant both cam pulleys were then out and there was not enough in the chain to level them up. Hence the mistake by the previous engine builder.

After checking all by hand I went for broke and built and fired her back up.

Immediately I could tell she was revving completely differently, far more eager and lively. I took her for a blast up the lane and she feels as if she has another 30BHP or so. Big difference, no flattening out, nice growl, no farting through the exhaust, smooth powerband, only the odd misfire.

She is running a bit lumpy because the carbs are now a mile out of balance. That's the next job. Have retested the compressions with the throttles open and have about 200 across the board.

Thanks to the many people who responded. I feel now I have a fighting chance of getting her running like Chapman intended. No wonder the PO could never get her running right.

I have posted a photo of the timing marks on the bench to compare with the one earlier in this post on the car.

Mark.



Mark.

[twincamman]

ok---I posted this trick a little while ago -------1--set the intake cam gear mark and the crank mark correctly [ at 0]-[needless to say #1 at tdc]-- [this will leave the exhaust slightly down] -2 remove the bolt and spacer and remove the exhaust cam gear ----3 place the gear in the chain so the mark is now correct [opposite the intake cam mark]--4 place a vice grip on the cam and move it back untill the cam peg sets into the cam gear ----replace the spacer and bolt and your timing is spot on -----[and the crowd still goes wild applause applause ]-- -ed [ the set the timing to 17 degrees at 2200 rpm --mine runs happily at at 22 deegrees advance in at 2500 rpm-----------

[twincamman]

ok --now that you have run out and followed the timing instructions and its all razor sharp-----get a unysin---ya ya I know Joe uses a manometer and somebody else uses a visual liquid and some body else uses a whatever ----LISTEN --- GET A UNYSIN ---now with fresh plugs[ cleaned and gaped at the least ] in the motor --turn the idle screws down to the bottom --CAREFULLY---and turn them out 1 and 1\4 turns ---start it up and balance the carbs with the screw in between the carbs ---until the unysin shows the ball is at the same level carb to carb----now --drive the bags off the thing get it all hot --THEN adjust the idle screws at 1000 rpm ]about 1\16th of a turn if your following instructions and the idle will be magic --set the speed with the idle control screw in the center of the carbs [dont get confused and touch the balance one ----NOW- anytime you lose power or performance from now on the problem will be in the points [closing up] or the plugs --or wires -or dist cap -or a hole in the block -so remember --carberetter in French for LEAVE IT ALONE---they never go wrong unless a float goes Titanic -or a needle and seat goes bad -so if you get bored on a Sunday afternoon go to a titty bar and have some beer and watch the girls but leave the car alone -----oh yes ---don't hurt yourself in the thing --- -ed