9 replies to this topic

[Petro1head]

I have a 1330cc engine with RE13 cam (Similar to 286), 37/29 Swiftune head, Calver modded distributor running Acuspark electronic ignition, new Lucal gold coil and twin HS4 SU carbs. Its running about 32deg total advance . Engine running about 200psi on compression test on all 4 cylinders

 

The engine now has about 2000 miles on it  however its always miss fired at about 5500 rpm.

 

I took the car to bogg bros who set it up and it stall miss fires so David changed the plugs from NGK BP7ES to NGK B7ES.  This did improve things however it missfired at just under 6000 rpm.  Engine was putting out about 70bhp at the wheels

 

We ran out of time and I have just put up with it but its starting to anoy me.  It seems to happen no matter what the throttle position is and I am unable to drive through it.  Likewaise pulling the choke out, in case it was running lean, makes no difference

 

I have attached photos of No1 and No4 plugs.  Interesting No4 insulation in pink in colour whereas No1 is grey/white  DSCF6800.JPG   41.18K   6 downloadsNo4

 DSCF6798.JPG   47.88K   5 downloadsNo1

 

My thoughts are could the coil not be man enough and the spark is getting blown out?

 

Any other thought or suggestions

Edited by Petro1head, 28 August 2013 - 09:31 PM.

[Cooperman]

There have been some very 'iffy' Lucas coils. I have had problems with them and in the end I fitted a Delphi coil which cured the problem.

Peter Baldwin said he has had huge problems with Lucas coils over the past few years, even new ones have been defective. Try a non-Lucas one.

[Petro1head]

There have been some very 'iffy' Lucas coils. I have had problems with them and in the end I fitted a Delphi coil which cured the problem.

Peter Baldwin said he has had huge problems with Lucas coils over the past few years, even new ones have been defective. Try a non-Lucas one.

Cheers, any suggestions as to which one to try

 

[edit]Stupid question as you have said Delphi

 

However any other choices in case I cant get one

Edited by Petro1head, 28 August 2013 - 09:35 PM.

[Cooperman]

I would try to borrow one first to identify whether that is the problem. You don't want to buy a new coil only to find it doesn't cure it. If you were nearer I would lend you one, but Newcastle is a long way from Cambridge!

[Petro1head]

Well I have a std silver lucac coil but had the missfire with that also, was one of the reasons for getting the Gold coil route.

 

I have just read this thread: http://www.theminifo...facts/?hl=+coil

 

I am running 25tho gap, should it be bigger?

I am using copper core leads, bought from here: http://www.gsparkplu...-pvc-black.html

[Cooperman]

Plug gap at 0.025" should be fine.

Could it be running too weak right at the top end?

Or could the timing be insufficiently advanced at high revs?

 

I'm afraid it's a case of keep trying, or put it back on the rolling road with everything wired up to find where & why it's 'missing'.

[Petro1head]

Calver recconed 30deg max advance would be fine the engine spec

If it was running week surly by pulling the choke out would richen it up and make it run better?

 

Any idea why the change from protruding plug to non protruding would change the poit in the rev rage that the missfire occured?

 

Would you think NGK heat range of 7 was correct?

Edited by Petro1head, 28 August 2013 - 10:16 PM.

[jaydee]

I dont think its something to do with plugs, although they can make the problm less evident, they're not the cause.

As with everything, its the cause of the problem you need to fix.

The RR operator already tried fresh plugs, good things becuase we all know how unreliable are these plugs nowadays, but the problem is still there.

I'd be looking at the low tension LT circuit first. Coil and its connections. I had a lucas DLB105 failing.

7s can cause a missfire at bottom end if not correct, not at top end.

Fuelling and timing looks right by looking at the pic, but theres a difference between #1 and #4 with #4 running richer, this suggests an air leak or wrong tappet clearance, which could be the cause of the top end missfire. Remember that you'll have a difference between inner and outer cyls due to the siamese ports, so cyl 1 and 4 will burn equally unless porting or chamber size are wrong and missmatched.

Single or twin carbs?

[Petro1head]

I have a 1330cc engine with RE13 cam (Similar to 286), 37/29 Swiftune head, Calver modded distributor running Acuspark electronic ignition, new Lucal gold coil and twin HS4 SU carbs. Its running about 32deg total advance . Engine running about 200psi on compression test on all 4 cylinders

 

;)

 

Will check the tappets

[Petro1head]

Misfire solved, it was the acuspark unit. So I am now running on points at the mo. engine revs cleanly up to 6500