Brian Sculpher

[Brian Sculpher]

Can anyone assist?

I recently had an issue with my engine failing to run correctly apart from idling only - as soon as the accelerator was depressed the car appeared to blow back through the H6 SU carbs.

I have already undertaken the following in an effort to resolve:

1) Retimed the engine in accordance with the manual = No 1 cylinder confirmed at TDC and set the red rotary arm pointing to No 1, inclusive of a new set of  points.

2) All the spark plugs were removed cleaned/capped and temporarily secured to the head ensuring a suitable spark achieved.

3) Refurb SU kit x 2no sets obtained/installed which includes: the Main jet, needle, gland cork caskets, seat cork casket, to include necessary replacement brass washers. Although the needle valve could easily be centralised during the rebuild, the piston below the cover cap would stick within the cylinder further adjustments resolved this issue. The mixture control was first set at 2 full turns from a snug point following the jet originally set correctly flush with the carb body.

4) The engine will now start albeit only briefly and backfires through the carbs and then stalls.

Has anyone experienced a similar problem, as prior to my problem the car was running fine.

With thanks

Brian

 

 

 

 

[Pete Lewis]

Think I would take it down to 3 turns   it can spit back if too lean

Also tight valve clearances  , head gasket failing, burnt inlet valve seats .....do the cheap and simple first

Can you do a compression test  ???

Pete

[Brian Sculpher]

Hi Pete,

I appreciated your prompt response.

I will undertake as suggested in the next few days as suggested.

Turn down to 3 turns // although valve clearance were adjusted some month ago I will re-check as you now have advised.

A close friend did a compression test some 3 months ago and were found to be fine, perhaps a may be necessary again depending on results of above changes/checks.

If OK I let you know more later.

Many thanks

Brian

 

 

 

 

 

[dougbgt6]

Brian,

Also suspect the manifold gasket, you can have good compression and not start at all! Even a slight air leak here and nothing will run right.

Doug

 

[NonMember]

As Pete says, the spitting back is often caused by being too lean. It's even possible to get your original symptoms (idles fine but backfires on opening the throttle) simply by not having any dashpot oil.

I've also had a car exhibit very much that behaviour - would run at very light throttle but not if more open - due to a broken wire in the distributor, meaning that the vacuum advance could make or break the circuit. That one flat refused to re-start once stopped, though.