48 replies to this topic

[Tonylamb]

Just picked up this thread because I'm having terrible trouble with my new engine build.  1380 with MED Stroked Crank and pistons, Calver fast Road Head and Cam nothing too extreme.  Electronic dizzy.  Running on twin 1.5's absolutely cannot get it rich enough as soon as you let off the throttle it goes lean lean lean.  Car is fitted with air fuel gauge.

SU's just slamming shut when you let off after high rpms.  

Switched to a Weber which just seems to make the middle two chambers rich and had the same problems with lean at lift.

 

We built the engine to 11.3 Comp ratio. Recommended by Calver.  Which I was persuaded was needed to produce the power.  Seems like far too much to me for a road car.  I would run 98Ron super and would stick some additive in it.  

 

Cannot get to the problem and it pinks like crazy.  Just cannot get enough fuel in it at top end.  Thinking the only answer is to drop the comp ratio with a slightly thicker head gasket.  Dizzy has programable curve but Comp ratio seems like the problem.  But I'm a bit worried about the Quench?

 

Any more thoughts on what is a fairly extensive thread.  Thanks

[Lplus]

Just picked up this thread because I'm having terrible trouble with my new engine build.  1380 with MED Stroked Crank and pistons, Calver fast Road Head and Cam nothing too extreme.  Electronic dizzy.  Running on twin 1.5's absolutely cannot get it rich enough as soon as you let off the throttle it goes lean lean lean.  Car is fitted with air fuel gauge.

SU's just slamming shut when you let off after high rpms.  

Switched to a Weber which just seems to make the middle two chambers rich and had the same problems with lean at lift.

 

We built the engine to 11.3 Comp ratio. Recommended by Calver.  Which I was persuaded was needed to produce the power.  Seems like far too much to me for a road car.  I would run 98Ron super and would stick some additive in it.  

 

Cannot get to the problem and it pinks like crazy.  Just cannot get enough fuel in it at top end.  Thinking the only answer is to drop the comp ratio with a slightly thicker head gasket.  Dizzy has programable curve but Comp ratio seems like the problem.  But I'm a bit worried about the Quench?

 

Any more thoughts on what is a fairly extensive thread.  Thanks

Which needles and springs are you using?

[Tonylamb]

We tried all kinds of needles and springs its actually worth a really good tuning guy.  We also tried it with a Weber still the same problem.

 

I can only imagine its the CR but some folks tell me that 11.3 is acceptable.

 

Others think that for a road car anything over 10.5 is too much and 10.1 is probably better.  OK it may lose power but at the moment its undrivable.  A lesson here on getting excited buying a whole load of kit from MED.  They make race stuff but dont care if you buy it and it doesn't work on the road.  my fault.

 

Example I tried the belt drive instead of the cam chain.  Seal leaked like a sieve ruined the belt.  They didn't have any new ones and wouldn't for 6 months.  So I had to go back to a chain.  Might as well have set fire to a grand.

[sonscar]

Have you identified true tdc and verified the timing is set at sensible values.Not trying to be funny but this is the first thing to do and is very important.
The engine will lean off on closed throttle.Just thoughts,Steve..