The Ford Barn

37pickupproject · 04-21-2016, 02:33 PM

How much clearance do I need between the valve and the spark plug?

I'm running new edelbrock heads (1127), best gasket graphtite gasket (.045 compressed thickness), with an isky 1007b regrind. The cam has .355 lift.

If I use the use the edelbrock recommended champion rc12yc the valve will hit the spark plug. That plug has a 3/4 reach and it's a projected tip. If I were to use an NGK BR5ES plug it has the same reach but a non projected tip (.120 shorter) it may clear. But how much is enough?

It's a 4 1/4 x 3 5/16 engine with light port work, am I in the right heat range?

51 MERC-CT · 04-22-2016, 04:54 AM

Shoot for .050"min., electrode to open valve clearance.
You will have to determine from what you have, to achieve that.
The size of the engine is not the main factor in determining plug heat range.
Fuel mixture, timing etc. are just a couple of factors.

Walt Dupont--Me. · 04-22-2016, 06:38 AM

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Some place makes spacer washers for spark plugs. Walt

04-21-2016, 02:33 PM	#1
37pickupproject Member Join Date: Jul 2014 Location: Minneapolis, Minnesota Posts: 78	Spark plug to valve clearance How much clearance do I need between the valve and the spark plug? I'm running new edelbrock heads (1127), best gasket graphtite gasket (.045 compressed thickness), with an isky 1007b regrind. The cam has .355 lift. If I use the use the edelbrock recommended champion rc12yc the valve will hit the spark plug. That plug has a 3/4 reach and it's a projected tip. If I were to use an NGK BR5ES plug it has the same reach but a non projected tip (.120 shorter) it may clear. But how much is enough? It's a 4 1/4 x 3 5/16 engine with light port work, am I in the right heat range?

04-22-2016, 04:54 AM	#2
51 MERC-CT Senior Member Join Date: May 2010 Location: East Hartford, Ct Posts: 5,898	Re: Spark plug to valve clearance Shoot for .050"min., electrode to open valve clearance. You will have to determine from what you have, to achieve that. The size of the engine is not the main factor in determining plug heat range. Fuel mixture, timing etc. are just a couple of factors. __________________ DON'T RECALL DOING SOMETHING FOR MYSELF BASED ON SOMEONE ELSE'S LIKES OR DISLIKES Last edited by 51 MERC-CT; 04-22-2016 at 06:04 AM.

04-22-2016, 06:38 AM	#3
Walt Dupont--Me. Senior Member Join Date: May 2010 Location: Gardiner Me. Posts: 4,200	Re: Spark plug to valve clearance Sponsored Links (Register now to hide all advertisements) Some place makes spacer washers for spark plugs. Walt