Situation: utterly gutless performance after 140,000 miles (70,000 since head was ?overhauled?, 100,000 since bottom end shells and rings were replaced with standard sized items), marginal compression (150 ? 160 psi when hot, dry, WOT), embarrassingly excessive level of smoke during starting up after standing for more than a day or two. I can’t afford a full overhaul parts bill, and I want to get another 10,000 leisurely miles of the car without being accused of environmental vandalism. All I need is to fix the smoke issue and have the engine run and accelerate smoothly. I am thinking of spending about ?500 on having the webers ultrasonically cleaned, retaining the original jets, with a view to getting smoother running and hesitation-free acceleration, and fitting new valves (plus cutting of valve seats) and new guides, to fix the smoke and possibly help with getting the smoother running.
My questions: (a), if I make do with the existing tappets and sleeves which are likely also to be well worn, could I still be faced with high level of smoke on start up? (b), If so would there be any benefit in replacing only the tappets, not the sleeves? (c), if I reface the valve seats will I need to add ?lead? to the fuel for normal road use? (d) Or is there a better way to spend the ?500 budget? Thanks in anticipation.
I think you need to do a few more diagnostics before you spend your well earned dollars!
proper leakdown test would be good as a start.
As far as the carbs, you could almost buy a new set for 500 quid…
If it is the carbs it could also be a jetting problem.
Tim
New valve seats, new bronze valve guides, and probably new valves would be the minimum needed. Can that be done for $1000?..maybe. Some testing before wrenching is always a good policy.
Don
Rereading your post I want to add to my comments. The tappets and sleeves could be usable. The other problem is the piston rings. If you have a valve guide problem and fix the head with new seats and valves the additional pressure created could push the old rings over the edge.
Cure smoking at startup and create smoking while running.
Don
hey there,
Like Tim says, I wouldn’t spend all the money on the carbs. You can do a pretty good job yourself by completely dismantling them and then soaking them for a couple of days in petrol, then using a selection of old toothbrushes and cheap plastic brushes etc to clean all the parts, blowing them out with compressed air and reassembling. You might find a couple of the idle jets are blocked, and the accelerator pump is stuck. With care these can be sorted out practically free of charge - although getting a couple of overhaul kits (pattern kits, not original, 25 quid the pair) is a good plan. If you can’t get jets etc unblocked with air alone, be very very gentle if you use a needle or you’ll enlarge the holes. then check the float heights blah blah blah, i’m sure you know the drill.
I presume the gutless performance isn’t because the ignition is hopelessly out and the carbs are running, say, way too rich? what do the plugs look like - oily, sooty, ok?
I had an ‘oil burning’ case on my alfa 1750 gtv when i bought it, turned out the DPO had made his own ‘oil catch tank’ from a plastic water bottle, which was effectively blocking the crank venting, oil was weeping through all the seals, geting blown by the fan all over the engine bay and getting sucked in through the webers. Initially I thought it was guides - as did the DPO who sold it cheap - but the engine turned out to be sweet once the leak was sorted (and a million weeping seals replaced…)
if you do a wet compression test, what results are you getting? at least that’d indicate top/bottom, although i agree smoke after standing points to guides. if you stripped the head yourself i reckon you could get them done for less than the money you have; workshop manual says heat and drift them out, so not the most difficult of jobs.
I think you might get away with re-using the sleeves as I don’t see them making a huge difference to the amount of oil getting down the guides.
let us know any other observations you have - i’m sure we can work this out!
hope this is of some use
will
Coincidence… I had my head rebuilt this week at Sheffield Engine Services who come highly recommended 01142320400. Stripped, crack tested, slightly refaced, valve seats recut, new valves, sleeves, guides, ?220.
Jim
I rebuild every 50 to 60 thousand miles ----bottom end [mains and con rod bearings ] -rings - water pump and valve lapped or replaced as needed etc ----motor in the super 7 has 170000 miles on it and the 26r ran all last year trouble free but the performance fell off a bit so now has new valves -rings -bearings- water pump and timing chain on the way to rebuild --have the crank crack tested —the motors cost about 450 to 550 cdn dollars in parts and some garage time to rebuild —they are worth the investment just being able to ‘stand on it’ confidently - --ed —
One assumes the smoke is oil? In which case why a carb rebuild? ?500 is way too much to spend on it anyway as Tim has said. Get the toothbrush out!
That cash could buy a hone and new rings or rebore and new pistons (just, if you are lucky!) if that’s the prob or new guides and valves if it’s that. ‘Leakdown’ could prove which is required. After your mileage it could be both, of course! 100k is pretty good on a twincam without some smoke.
Roy
'65S2
One assumes the smoke is oil? In which case why a carb rebuild? ?500 is way too much to spend on it anyway as Tim has said. Get the toothbrush out!
That cash could buy a hone and new rings or rebore and new pistons (just, if you are lucky!) if that’s the prob or new guides and valves if it’s that. ‘Leakdown’ could prove which is required. After your mileage it could be both, of course! 100k is pretty good on a twincam without some smoke.
Roy
'65S2
I am with the others i am afraid you would be wasting ?500 it is likely rings & guides will be shot do the leak down & find out what you are up against. Only 140K i would take it back under warranty. Good Luck
Ian
Ok ----first --carburetter is French for leave it alone because it aint the problem —second there are no valve guide seals on these motors so when they are parked any excess oil leaks into the pistons and smokes on start up and when the guides get worn they smoke all the time —at that mil age a complete tear down and rebuild is in order ------ Ill tell you what-----I have a 711 block ff push rod 1600 cc motor and a set of 40 mm dcoe Weber’s and manifold that will bolt right in ----it will be rebuilt after the TC is installed in 26r s2 33 -later this month or early June [hopefully]---- oyyyy–such a deal we could make!!! ed
You can also buy a rebuilt crossflow 711M block for ?525. bit of negotiation an you could probably get them to bore it out to fit the lotus pistons (which you can get for ?60 a set) and deck the block.
Tim