I just brought an auto 18rc powered ra40, and it has a wicked miss fire on idle but it clears up after about 1500rpm, it's something to do with cylinder 3 because when you pull the lead off number 3 nothing changes. But theres a nice blue spark, it has brand a new looking dizzy cap, I've tried different leads and a different spark plug... but the miss fire is still there.

 

What on earth is going on? Its shitting me up the wall.

 

Cheers

Corey

Burnt valve??

 

Has most effect at idle as the air has time to leak past, and at higher revs you don't notice it.

 

Done a compression test??

 

Could be head gasket I suppose, same thing- most noticeable at idle.

Its pointing more towards a burnt valve I'm thinking, I adjusted the the tappets up to specs and it fixed the miss a little bit. But she still puffs away on idle.

If it a nice body its worth doing the motor up. Rings and bearings OK?? So a head gasket set and re-cut of valves and seats would freshen it up.

 

Any sign of an 18RG for sale.... that would make a difference... :laff:

G`day mate, a simple test for a burnt valve is to grab a flat peice of paper about 200x100 and hold it with your finger tips so it droops over the end of your exhaust pipe when the car is idling. On the firing strokes of the cylinders that the valves are seating ok, the paper will be pushed away from the exhaust. If one cylinder has a burnt valve the pistion stroke will try to pull gas back into the cylinder via the exhaust and so will pull the paper over the pipe.

That saves having to come up with a compression gauge to do much the same test.

Cheers.

Altezza is taking the words out of my mouth :laff:

 

After the RWC clears and I get some more money together, a w50 and 18RG will be going in. Should be a pretty grunty first car.

Cheers Oldfella, ill give that ago after I finish waxing it.

dizzzzzzzzzzy????