Can someone PLEASE set me straight on which valves need extra clearance on an 83mm bore.  How to modify says on page 15, "When 35mm exhaust valves are used on engines with 83-85mm bores and high lift cams, the bores must be relieved, or notched, in the area of the exhaust valves".

 

I've read a lot about the intake valves hitting.  So which is it?  Both?

 

Thanks for any input,

Cliff

I just did the exhaust on an L24 with Maxima N-47 head and medium lift cam. It worked fine.

Doing the intake *may* give better breathing but lower CR

The bible is correct. Early L24 engines had 33mm exhaust valves. and 42mm Intake Valves. Installing 35MM exhaust valves with a high lift cam requires slight bore notching for clearance. The valve center-line is offset to place the larger Intake valve closer to the center-line of the combustion chamber, so it normally clears the cylinder wall no problem.

 

Installing 44 mm Intake valves and a .500" lift cam on an L24 will clear the cylinder wall " Physically " if my memory serves me correct. Bore notching on the Intake side is done purely for " un-shrouding purposes. DOUBLE CHECK that clearance...it's been a long time since I've assembled an L24!!!

 

Best way is to install some lightweight checking springs on the valves and assemble with retainers. 

 

Bolt the head to the block with an old gasket, flip it over, then physically open and close the Intake and exhaust valves while looking down the bore. Confirm the valve to piston wall clearances visually.  Use a dial indicator to measure valve lift. Give at least .090" clearance over maximum valve lift specs to allow for Valve float in the case of over rev.

 

As I said. I'm reasonably sure that the 42mm and 44mm Intake valve clear the cylinder wall at all lifts. But check it to be sure. The 35mm exhaust valves do not. They can tag the bore edge.

 

Of course you're going to check Piston to Valve clearance as well.... correct?

Thanks guys.  I always forget the simplest things, I have 12 intake valves in a coffee container.  I put them in my bare N47 and put that on top of my 2.4 without a head gasket.  They dropped and hung up on the carbon ring at the top of the bore, barely tapped them and they fell through. 

Then I put a used gasket on and they fell through as soon as I let the clothes pins loose.