Tappet queries
Discussion
All
Can any one answer this
MY 89 esprit is down 30 psi on the very rear cylinder and is consequently idleing off she is fine when being driven
I have talked to Pete (who was very helpful in PMN) he indicated it migh be the tappets (engine was rebuilt 15000 miles ago) What do I have to do to set the tappets, has anyone ever done this ,,,,, is there a step by step guide and how lightly is this to cause the above symptoms.
Regards Cathal
Can any one answer this
MY 89 esprit is down 30 psi on the very rear cylinder and is consequently idleing off she is fine when being driven
I have talked to Pete (who was very helpful in PMN) he indicated it migh be the tappets (engine was rebuilt 15000 miles ago) What do I have to do to set the tappets, has anyone ever done this ,,,,, is there a step by step guide and how lightly is this to cause the above symptoms.
Regards Cathal
Dr Hess was hoping you would reply
I can do the oil test what would this show???
Lats year I done a compression test and all were at 168 psi she has only completed 3000 miles since however recently I had an accelator cable change could this affect only one piston when doing a compression test would balancing the 2 carbs help
Cathal
>> Edited by lotire on Tuesday 2nd August 17:49
I can do the oil test what would this show???
Lats year I done a compression test and all were at 168 psi she has only completed 3000 miles since however recently I had an accelator cable change could this affect only one piston when doing a compression test would balancing the 2 carbs help
Cathal
>> Edited by lotire on Tuesday 2nd August 17:49
Well, if you put 5cc of oil down the hole and the compression comes up significantly, it indicates a problem with rings. If it doesn't come up, then valves could be involved. If the lash is 0, that is, the valves are being held open, you can burn an exhaust valve and that would cause that cylinder to read low. A really really out of sync carb might do that, but it would have to basically have the butterfly shaft twisted within the carb so that #3 was opening but #4 wasn't, and I don't really see that happening.
I haven't done a valve adjustment myself yet, but from what I have read from the experts like Tim, et.al, it isn't that big of a deal. Just take the cam towers off with the proper star tool, etc. Follow the instructions in the book. You should be able to pull the cover off and check the lash without too much trouble. I would do that (after the repeat compression test) and see what you have. If they are all within spec, I think you're going to have to pull the head.
In my opinion, carbs and turbos are a dangerous combination. Especially on motors that are expensive to rebuild.
Dr.Hess
I haven't done a valve adjustment myself yet, but from what I have read from the experts like Tim, et.al, it isn't that big of a deal. Just take the cam towers off with the proper star tool, etc. Follow the instructions in the book. You should be able to pull the cover off and check the lash without too much trouble. I would do that (after the repeat compression test) and see what you have. If they are all within spec, I think you're going to have to pull the head.
In my opinion, carbs and turbos are a dangerous combination. Especially on motors that are expensive to rebuild.
Dr.Hess
lotire said:
All
Can any one answer this
MY 89 esprit is down 30 psi on the very rear cylinder and is consequently idleing off she is fine when being driven
I have talked to Pete (who was very helpful in PMN) he indicated it migh be the tappets (engine was rebuilt 15000 miles ago) What do I have to do to set the tappets, has anyone ever done this ,,,,, is there a step by step guide and how lightly is this to cause the above symptoms.
Regards Cathal
A leakdown test would give you more information, let you know whether it is leaking past intake valves, exhaust valves, or rings.
Do that before you take everything apart.
Next, if it is valves, you'll need to check the clearence on the valves. This can be done by removing the valve covers only (really easy). If the valves are in spec, then you have to look at valve damage.
If the valves are out of spec, then you'll need to remove the timing belt from the cams (not a full belt change, don't need to break the water system open). You'll have to remove the cam towers, being carefull not to loose the shims (use magnets ontop of the tappets to retain the shims). Record the shims and mix them to put them where they will bring it back to spec. Order any shims that you need. Then do a dry fit (no gasket for the cam tower, but grease the shims) and add .0015" to any valve clearence to account for the gasket adhesive. Once it is in spec, you can apply the gasket material (use Loctite 518 or Permatex anerobic gasket maker), torque the cam towers on to spec. Then check clearences again. Refit the belt, and tension. It is also a good idea to replace the o-rings around the cam tower bolt plugs, and the end seal o-rings.
Shims
www.lotuscolorado.com/vulcangrey/gallery/fueltankremoval/P8090099
tappets, shims, and cam tower
www.lotuscolorado.com/vulcangrey/gallery/fueltankremoval/P8090100
cam towers
www.lotuscolorado.com/vulcangrey/gallery/fueltankremoval/P8090102
cam tower bolts, two are hex (at each end) the rest are E-10 torx (male)
www.lotuscolorado.com/vulcangrey/gallery/fueltankremoval/P8090107
mark your belt like this (2 stripes on intake, one stripe on exhaust, one stripe on crank) to put it back on easily. Don't forget to put some paint on te cam too.
www.lotuscolorado.com/vulcangrey/gallery/fueltankremoval/P8090108
www.lotuscolorado.com/vulcangrey/gallery/fueltankremoval/P8090113
Lotus head, can be removed inplace.
www.lotuscolorado.com/vulcangrey/gallery/head-and-fuel-tanks/P1010001
if you have to remove the head, DO NOT rotate the crank without cylinder liner clamps!!!! You must have clamps installed, or the cylinders will press out the liners and they will have to be reglued in!!!
www.lotuscolorado.com/vulcangrey/gallery/head-and-fuel-tanks/P1010001_001
Travis
Vulcan Grey 89SE
www.lotuscolorado.com/vulcangrey/
>> Edited by lotusse89 on Wednesday 3rd August 03:21
CD,
A 4-tube manometer is the best way to balance the carbs. I like the Carbtune II mercury-free unit. They're a little expensive, but sometimes you get what you pay for. They show up on eBay from time to time for much less than new.
For a quick eyeball check, remove a progression hole cover from each carb. Adjust the throttle so the butterfly just aligns with the edge of one of the drillings. Then look at the same hole in the other carb to see how that butterfly aligns. A gross error should be obvious to the eye. Adjust the screw on the throttle linkage coupler to get the same apparent setting on both carbs.
To really get it right... invest in a 4-tube manometer. Once you get the proper tool I can forward instructions on how to use it.
Regards,
Tim Engel
Lotus Owners Oftha North
A 4-tube manometer is the best way to balance the carbs. I like the Carbtune II mercury-free unit. They're a little expensive, but sometimes you get what you pay for. They show up on eBay from time to time for much less than new.
For a quick eyeball check, remove a progression hole cover from each carb. Adjust the throttle so the butterfly just aligns with the edge of one of the drillings. Then look at the same hole in the other carb to see how that butterfly aligns. A gross error should be obvious to the eye. Adjust the screw on the throttle linkage coupler to get the same apparent setting on both carbs.
To really get it right... invest in a 4-tube manometer. Once you get the proper tool I can forward instructions on how to use it.
Regards,
Tim Engel
Lotus Owners Oftha North
I actually done this and yes she came in and compression came back up on the last cylinder I cant figure this out is there an offset between each butterfly? ie are they at a slightly different angle in each barrel, I have also ordered a 4 column manometer there are really good instructions on www.delorto.co.uk
Regards CD
Regards CD
lotire said:
I actually done this and yes she came in and compression came back up on the last cylinder I cant figure this out is there an offset between each butterfly? ie are they at a slightly different angle in each barrel
CD,
The correct procedure for a compression test includes:
1) engine at full, normal operating temperature
2) hold the throttle wide open and...
3) crank the engine at 200 rpm or better. To achieve the 200 rpm on the starter usually requires removing all spark plugs to relieve the compression pressure.
You report that your test results varied from cylinder to cylinder and that the variation improved when you balanced the throttles. That would indicate that the original compression test was done with the throttles closed... and that the throttles were out of balance. Two separate issues.
If you still wish to check the compression, repeat the test with a hot engine, wide open throttles and 200 rpm.
And to your question... no there should not be a difference between the angles of the butterflies, but yes it can happen. Getting the angles all the same is what balanceing the carbs (or throttle bodies) is all about.
So, do balance the carbs. You can get close by looking at the alignment of the butterflies and the Progression Holes, but getting the balance truly right requires an flow or vacuum measuring instrument of some kink. The best (IMHO) is a 4-tube manometer... and I like the Carbtune II the best.
An imbalance will be most noticeable at idle/ closed thottle. In that case there isn't much air flowing into the engine, and a small difference in butterfly position can make a large percentage difference in how much air/fuel mixture is getting to each cylinder.
Just a small imbalance will cause the engine to idle poorly. The rough running will seem to deminish at wider throttle openings, but the engine will still not run properly all through the rev range.
If a compression test is done incorrectly with the throttles closed, then the cylinder that receives more air past the slightly more open butterfly will show a higher compression reading... and vice versa. Checking compression at wide open throttle pretty much eliminates any differential flow due to throttle imbalance.
If the barrels on one carb are pretty closely balanced but there's a difference between 1-2 and 3-4, then it's just the linkage coupler between the carbs that's out of adjustment. A simple screw adjustment.
If there's a significant difference in manifold vacuum between the two barrels of one carb, then the throttle shaft is twisted. That usually happens when someone tries to remove the nut at either end of the shaft by simply turning it with a wrench. Doing that requires the shaft to react the applied torque. But it's just a slender brass shaft with big notches cut out of it where the butterflies sit, so it's pretty weak.
Removing or tightening the nut(s) by simply turning with a wrench will surly twist the shaft. Once the shaft is twisted the two butterflies will be at different angles, and the resulting difference in manifold vacuum will probably be more than can be compensated for by adjusting the Air Bleed Screws.
The correct way to remove/ replace the nuts is to first remove the carb from the manifold. Then use a long-nose pliers with padded jaws to straddle the butterfly and grip the shaft just insde the carb wall from the nut. Then torque the nut while reacting the load with the pliers. That will keep the load from being applied to the length of the shaft.
The "book" fix for a twisted shaft is to replace it. However, you can twist it back with a little patience.
Determine which butterfly is more closed (stronger vacuum) and which is more open (weaker vacuum). Then figure out which way the shaft needs to be twisted to make things right.
Hook up a 4-tube manometer. Close the Air Bleed Screws. Apply wrenches to the nuts on either end of the shaft and gently twist a bit while observing the manometer. When you release wrench pressure, the shaft will spring back a bit. So it will be necessary to over-shoot the desired setting a bit so the final setting is correct after the spring-back. Sneak up on it in little steps.
Get the butterflies tweaked in as close as you can, then use one Air Bleed Screw to finish the job. Open the Air Bleed on the stronger barrel to weaken the vacuum until it matches that of the weaker barrel. Open only one Air Bleed.
Good luck,
Tim Engel
Lotus Owners Oftha North
Cathal,
Your original post was about checking/ setting valve clearances (Tappet queries). Did you get the answer you were looking for on that.
Compression pressure would only be affected if some of the clearances had gone negative... which would prevent the valve from sealing. Did you ever check the clearances? Checking is the easy part... it's adjusting that takes a lot of work.
Just remove the cam cover and check clearances with a feeler gauge. Rotate the engine in it's normal operating direction until the cam lobe to be checked it pointing straight up away from the tappet. Push the tappet down to make sure it's fully seated against the valve stem. Measure the clearance between the tappet and cab with a feeler gauge. Rotate the engine again and check another cylinder until you've got them all.
Reinstall the cam covers with a sealant/ gasket dressing, replacing the gaskets if necessary.
Regards,
Tim Engel
Lotus Ownwers Oftha North
Your original post was about checking/ setting valve clearances (Tappet queries). Did you get the answer you were looking for on that.
Compression pressure would only be affected if some of the clearances had gone negative... which would prevent the valve from sealing. Did you ever check the clearances? Checking is the easy part... it's adjusting that takes a lot of work.
Just remove the cam cover and check clearances with a feeler gauge. Rotate the engine in it's normal operating direction until the cam lobe to be checked it pointing straight up away from the tappet. Push the tappet down to make sure it's fully seated against the valve stem. Measure the clearance between the tappet and cab with a feeler gauge. Rotate the engine again and check another cylinder until you've got them all.
Reinstall the cam covers with a sealant/ gasket dressing, replacing the gaskets if necessary.
Regards,
Tim Engel
Lotus Ownwers Oftha North
All thanks for you help and the excellent advice.... I have balance the carbs using a 4 column manometer and with the instructions I have recieved. the car has never run so smooth. I can confirm the butterflys were offset and this resulted in the compression figures being different on the cylinders
Cathal
>> Edited by lotire on Monday 15th August 09:56
Cathal
>> Edited by lotire on Monday 15th August 09:56
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