Valve clearance issue

Redstern837

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I have a 7.3IDI that I built a few months ago with upgraded injectors, pump, and cam from R&D, as well at ARP head studs, dual valve springs, and the stock turbo system. I just took the engine apart again because it was making some noises I wasn't liking, and what I found was that every single exhaust valve was hitting the pistons. I don't have reason to suspect the cam is out of time because it ran perfect and made tons of power.
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I realized the problem was that I bought the engine dissembled, and the guy I bought it from said he got the heads decked, and I didn't think anything of it at the time. So it was put together with a regular thickness head gasket and the higher lift cam.

My questions are, what is the stock deck height on the heads and block and how do I measure it? I don't know how much has been milled off. Also what are my options for thicker head gaskets or head gasket spacers. I know I can get my pistons milled, but I need to know if that will take off enough to clear properly.

I am already going to send the block to a machine shop to get at least one bore sleeved as one bore is badly worn and was piston slapping.
 

Booyah45828

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The spec for deck height is irrelevant. The spec your looking for is valve recession and piston protrusion. Those 2 items will give you your valve to piston clearance. If they're out, you'll end up with where you're at now. Any machine shop and engine builder worth a darn will measure both of those specs before assembly, especially if any decking was involved.

I'm unaware of any optional head gasket thicknesses. At one time, there were pistons made that had the wrist pin hole machined higher in the piston that could give a rebuild additional clearance. But I'm not sure if those are made/available any more. I also believe I've read about head saver shims being available for the IDI as well, but I can't comment on the availability/reliability of those either.
 

71 Highboy

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I have a 7.3IDI that I built a few months ago with upgraded injectors, pump, and cam from R&D, as well at ARP head studs, dual valve springs, and the stock turbo system. I just took the engine apart again because it was making some noises I wasn't liking, and what I found was that every single exhaust valve was hitting the pistons. I don't have reason to suspect the cam is out of time because it ran perfect and made tons of power.
You must be registered for see images attach


I realized the problem was that I bought the engine dissembled, and the guy I bought it from said he got the heads decked, and I didn't think anything of it at the time. So it was put together with a regular thickness head gasket and the higher lift cam.

My questions are, what is the stock deck height on the heads and block and how do I measure it? I don't know how much has been milled off. Also what are my options for thicker head gaskets or head gasket spacers. I know I can get my pistons milled, but I need to know if that will take off enough to clear properly.

I am already going to send the block to a machine shop to get at least one bore sleeved as one bore is badly worn and was piston slapping.

If you are sending your block out for one sleeve, they can measure deck height at that time and tell you how much is gone. Usually .010" will clean them up. Next, check everything in the cylinder with clay and light valve springs installed in a mock up assembly and rolling it through all cycles. It sounds/looks like you only need to seat the exhaust valves about .040" deeper into the head for acceptable piston to valve clearance, and readjust spring packs.
 

Redstern837

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It sounds/looks like you only need to seat the exhaust valves about .040" deeper into the head for acceptable piston to valve clearance, and readjust spring packs.

So that would involve having the machine shop cut the valve seats down a bit, and then shimming the springs? Would I need to shim the rocker arms too, or is that difference in height no issue for the hydraulic lifters?
 

71 Highboy

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So that would involve having the machine shop cut the valve seats down a bit, and then shimming the springs? Would I need to shim the rocker arms too, or is that difference in height no issue for the hydraulic lifters?

Correct on all points, except about the rocker arms. A good shop can also adjust stem length and re cut for the keepers if necessary. The lifters will adjust for these minor differences; the rockers need to operate in the designed geometry. I have a similar cam to the R&D, and a decked block with new pistons, so just went through all this. Measure. Measure again. And use clay for checking your math. You are lucky if no valves are bent, ( I would replace them all ), and hope there are no cracked pistons. These are tough pistons, but they obviously were impacted hard.
 

aggiediesel01

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Also know that Justin had some specific instruction on how to time the cam. Some of his cams had to be installed retarded a tooth but I don't know if it was batch specific or what. Anyway check with him or some of the other guys that have put his cams in.
 

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