7.3 IDI Block Deck Flatness / Trueness Spec

[MasterChiefIDI]

I have been looking all through my service manual and cannot find the Block Deck Flatness spec anywhere. Can anyone provide me what the max clearance should be when checking with a straight edge? I am trying to determine if my deck is acceptable or if I need to resurface it. Any help is appreciated.

 

[MasterChiefIDI]

I may have just found it.. This is from my 6.9 manual and I am thinking it would apply to my 7.3 as well. Would this be correct?

Thanks!

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[IDIBRONCO]

I'm no machinist, but that sounds like A LOT of warpage to me. I might be wrong, but half that seems like a more realistic limit.

 

[rreegg]

I have no experience with this but think there’s a recent thread about similar work from @bulletpruf

It doesn’t have shop manual specs copied like your post but there are some tolerances mentioned so maybe it’s worth a oook and hopefully more experienced folks can chime in

Can You Surface IDI Cylinder Heads with Sandpaper?

So, I surfaced some cylinder heads this weekend in the garage quickly and accurately with some 60 and 80 grit ceramic sandpaper (Don't use box store sandpaper! Get Hercules ceramic sandpaper from Harbor Freight), a feeler gauge, an OEM Tools 2' machinist straightedge, and an inexpensive granite...

www.oilburners.net

 

[lotzagoodstuff]

I'm no machinist, but that sounds like A LOT of warpage to me. I might be wrong, but half that seems like a more realistic limit.

I agree that .003" sounds like a lot, especially when the cylinder head flatness spec is more like a third of that, but I think you have to think about the overall blueprinting of the engine. if you don't want to count your time, you could deck the block until it's way tighter than the spec. You could also cc each combustion chamber, and port/gasket match, polish, etc etc etc

When I think about potential block warpage on an IDI, I feel like the head gaskets and heads tend to respond to most of terrors of overheating. If you have the skills and tools to measure and flatten the deck, do it. If you really want it machined perfectly, contact Justin at R&D or find a reputable machine shop and spend the money. if not, I'd abide by the seemingly large tolerancing that you have per the manual with the comfort of knowing that somebody came up with those specs 40 years ago when your rig was brand new.

Any any case: bullnose 4x4 crewcab IDI is an awesome foundation, so best wishes regardless of how deep you get into the build.

 

[bulletpruf]

My preference is no more than .001" per cylinder, so .004" for a V-8 cylinder head.

If your block deck is perfectly flat, that helps.

 

[ROCK HARVEY]

Here’s what my 7.3 service manual says:

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I know the manuals say not to deck the block, but in Justin from R&D’s block machining video on YouTube he does multiple light passes on the deck during the process of sleeving the block. I think there’s some wiggle room now with the thicker head gaskets available today.

 

[IDIBRONCO]

I think there’s some wiggle room now with the thicker head gaskets available today.

Plus you can buy decompressed pistons. I haven't been able to, but some people have had someone machine some material off of the tops of their pistons too.

 

[MasterChiefIDI]

Thank y'all very much for the feedback! It is appreciated. That .003" spec seems more like it. I bought the OEM tool machinist straight edge from bulletpruf's video to check mine. Fantastic video btw!

So, I have already purchased .010" reduced height pistons and have had my cylinders and rods honed to match. The below picture shows the protrusion measurements I got for all 8 cylinders with these pistons in my block as it is.

If my deck is truly flat and decking is not necessary, should I use the .010 thicker felpro HG or go with a stock thickness HG from Victor Reinz? Wondering if the felpro would reduce my compression a little too much and make for hard starting considering my shortest piston is .010" on cyl 6. There will be a stage 2 turbo on this thing with R&D's cam FYI.

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[DougBoy66]

Just some info from my experience here. I have the thicker head gaskets in combination with the shorter pistons. I did have my block trued while it was at the machinist but it was very minimal to get that done. I am not experiencing any hard starts, we had a pretty good cold snap a little bit back and it fired right up at about 15 degrees f out door temp after the glow plugs cycled and without plugging in the block heater. I think that a strong glow plug system and a air tight fuel system make all the difference for quick starts apposed to what little change of compression you may see in the different head gaskets. The taller HG gave me more peace of mind knowing the tight clearances with the head to block but..... Results may vary.

 

[lotzagoodstuff]

Thank y'all very much for the feedback! It is appreciated. That .003" spec seems more like it. I bought the OEM tool machinist straight edge from bulletpruf's video to check mine. Fantastic video btw!

So, I have already purchased .010" reduced height pistons and have had my cylinders and rods honed to match. The below picture shows the protrusion measurements I got for all 8 cylinders with these pistons in my block as it is.

If my deck is truly flat and decking is not necessary, should I use the .010 thicker felpro HG or go with a stock thickness HG from Victor Reinz? Wondering if the felpro would reduce my compression a little too much and make for hard starting considering my shortest prison is .010" on cyl 6. There will be a stage 2 turbo on this thing with R&D's cam FYI.

Sounds like a really well thought out build. Regarding your concerns about cold starts: I think the DougBoy66 feedback coupled with the relatively mild weather in your neck of the woods would lead me to believe you'll be OK no matter what you do, but doing a quick stock versus your revised compression ratio would give you the ability to consider the actual effects of either gasket.

Again, cool truck with a well thought out powertrain plan

 

[MasterChiefIDI]

Thank you two for the kind words and feedback. This is a build that has suffered from scope creep and is one of those things that I want to get right the first time and not have to come back and do later. When this engine goes in I'm hoping to never have to take it out again!

I'll work on making some calculations and see where I'm at. I imagine .010" under the bottom spec from IH on 1 or 2 cyls will not make a huge difference but I'll see what the figures say. Got my straight edge in today to take with me to the machine Shop to validate it's flatness before I pick it up! This shop messed up my first block but they are making it right however I am still going to check their work with my own gauge.

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[rreegg]

Great to see the care and effort with this.

Watched a YT video today titled “changing Subaru head gasket in autozone parking lot” and he did what he set out to do… also part of the work was honing down the heads in the Home Depot parking lot on a big slab of tile/marble counter top.

It makes for interesting watching but I also felt a little sad cuz he was all “I don’t care am gonna flip the car anyway”.

 

[IDIBRONCO]

When this engine goes in I'm hoping to never have to take it out again!

By saying this, you are easily justifying the scope creep of your engine. It's FAR better to spend some extra money and get a lot more life out of your engine. Even if the total cost ends up being 3x what you'd originally planned for, that's only a drop in the bucket compared to new truck payments. Plus you get to brag to people what all you've done to the truck.

 

[IDIBRONCO]

I bought the OEM tool machinist straight edge from bulletpruf's video to check mine.

I just ordered one myself. It's possible to have too many tools, but then you build a bigger garage!