Strange noise in engine

[Steve Keohane]

Hi all,

I have just given QFAD's head a good decoke - lapped vales and cleaned combustion chambers and pistons (consequence of leaking valve stem seals).

When I fired up the engine (started fine) there was a 'loose tappet' sound which appeared to be coming from the O/S of the engine (I checked the N'S cylinder and all seemed fine). I listened some more and the sound definitely seemed to be coming from the crankcase and not the cylinder head) - I thought cam follower?? Mind you I know sound travelling around an engine can play tricks with you.

Anyhow removed the rocker box and checked the valves - all seemed fine. I then loosened the head and removed each valve train in turn - still the noise persisted (seemed to be a little loose tappet type sound every few rotations of the engine. Finally I removed the head and securing the barrel, held each pushrod in its follower - still the noise persisted?

Before I get too despondent do you folks have any ideas?

[david]

if you use a metal rod on the engine and to your ear, you will hear more accurately and be able to pin point the area of noise...rather like a stethoscope idea...-non sharp bit to your ear.....
hope its not 2 serious...

[tangara]

On my falcon engine, I had a very hard noise like too much clearence in valve gaping. Reset and no change. Tried the rocker, no change. Finally after a certain time and friends reflections we found the bronze rod ring was broken !!
Hope it will help

Thierry

[Steve Keohane]

Well after a good nights sleep and a fresh start I realized I had been turning the engine backwards! When rotated clockwise no strange noises. Anyhow QFAD is up and running; went for a wonderful drive around southern Wiltshire/Somerset today. had a picnic near Mere - wonderful views of the Blackmore Vale from Mere Down. Actually gave the Citroen suspension a good test driving along the green lane!

The only gripe is the Solex 26/35; I cannot seem to get on with this carb. I have read all the old blogs and noted Kens helpful tips;

Running St/Steel headers joining std crossbox onto a motor cycle type secondary silencer. Carb set up with; primary 110, Secondary 90, Primary air correction 1F2, Secondary correction jet 110 and an idle jet of 40. There is currently no air filter yet it seems to be running very rich? The engine runs fine a higher rpm but bogs down and spits back when pulling away.

Mind you I soon will not have to be a slave to the dark lord Solex (I'm convinced he is related to Lucas) as I will have my SU manifold welded this week (MkII version - I tried the 45 Degree angle but just could not get it to fit underneath the bonnet - now going for a horizontal option - realigned the SU float bowl). Looking forward to being an acolyte of the good and kind Lord SU.

I do not mind these troubles as I knew when purchasing the Lomax it would be an adventure...

Steve

[Ken Hanna]

Steve,
'spitting back' is invariably due to a weak mixture, so there are two things I'd recommend you have a look at...

First, the operation of the accelerator pump; with the engine running at about 2,000 rpm, operate the accelerator pump lever by hand and watch to see if there's a good shot of neat fuel from the nozzle which points downwards into the primary barrel.
It's very common for the accelerator pump to become 'lazy', particularly if a carburettor has been left idle for any length of time. A good shot of WD40 around the mechanism in conjunction with 'direct' operation usually helps to get things working as they should.

Second, have you adjusted the closing position of the secondary butterfly? With use, the factory setting will need adjusting, backing off the adjusting screw by 1/2 to 1 turn is enough to restore the seal. Depending on the age/type of 26/35 carburettor, the adjusting screw can have a different location, but for the last type, it's as shown in this photograph.
https://www.flickr.com/search/?w=301328 ... =secondary

Maybe worth a try, before you go over to the SUnny side of the street?

Ken

[Steve Keohane]

Hi Ken,

I have just cleaned the heads and lapped in the valves - they were heavily contaminated by oil leaking through very old valve stem seals (hard). Pistons and bores fine.


I have a 18/26 version of the 26/35. I have checked the butterfly adjustment (OK) and the accelerator pump is working fine. I get that the spitting back usually reflects a weak mixture - yet my plugs are sooted black?

At higher rpm the car bombs along happily at 70 mph+ (well indicated). It has always suffered at low rpm despite everything I do. I stripped the carb, fitted an overhaul kit, cleaned all jets etc, reset float height and blanked off the old choke mechanism. Maybe the floats are sticking??

Enough is enough so have gone for the SU.

Steve

[david]

The SU is very easy to tune to your engine if there is need... it is possible to modify the needle to overcome any flat spots [without taking it on the road ]
good book by Hammill explains but I can give you the general idea if necessary...
It worked wonderfully on the Superlite Triking racer at magny cours F1 en france...
using an old marina SU on a copper plumbing manifold for 1200cc guzzi from tickover to 8000 revs without hesitation,deviation or repetition....in" just a minute" time
David.

[Steve Keohane]

Well SU mocked up and all cables c/w brackets sorted. manifold off to powder coaters. Air filter (K&N) supplying lots of external cool air etc fitted ready for installation. I will report progress when all is assembled.

Steve: